My son (Paul A) spent the better part of the last two weeks helping some friends finish the plumbing and fixtures for a static firing. I went out Sunday to wire up some sensors and record data for the event. beyond that I can't talk about it much. All of the stuff Paul A and I were responsible for worked correctly. All the plumbing worked and I logged good data. Both Murphy and Marvin were present at the test. Marvin who??? Marvin the Martian of course, his favorite line "And right about now there should have been an earth shattering Kaboom!" It was nice to see everyone from FAR and work on a project with them. It was also nice as a father, to see skilled, competent, successful adults, impressed by my sons skills and work ethic. Being a father has been a hard job, but its nice to see that my son is starting to learn a lesson that took me at least 10 years longer to learn. Happiness and satisfaction can not be purchased. All too often we think I'll be happy as soon as I buy a new motorcycle,car, house,wardrobe etc... I'll be happy as soon as I'm promoted to manger, VP etc.... I strongly believe that happiness is earned by creating or doing something that has value. The sense of satisfaction earned by accomplishing something hard can not be oversold. I also think that the creation of tangible things with your own hands is of great personal value. You can not purchase this feeling.
While I was out at FAR waiting for other parts of the project to come together I flew the helicopter, the GPS finally works correctly in flight! Alas the Compass does not because the GPS antenna has magnets in the bottom and sits above the compass sensor. Arghhhh!
Tuesday, December 18, 2007
Saturday, December 08, 2007
Christmas Copter/Fun
One of my issues with working on the helicopter has been getting time to actually test. I can only really work weekends and evenings. If the weather is bad on the weekend, that means no testing for the whole week. I just discovered that people fly RC helicopters at night. (the previous link is not me)
I bought a pair of lit blades and some glow wire to give it a try. I'm not the worlds best RC pilot, I can hover nose in, nose out and fly around a little, but not a whole lot more. So I was worried about flying the big trex with 3K worth of electronics on it and crashing it. So I went to the hobby store today and bought some night blades for my little Trex. $45.00 worth of blades seems like a good price to see if I can fly at night. I wired up the glow wire and went out and tried flying it. I flew off three full battery packs in drive way at night, the test was both a success and a bit of fun. So now I have the confidence to be comfortable flying the big trex in an open field at night!
My wifes comment "oh thats pretty it matches our Christmas lights, a Christmas copter!"
I bought a pair of lit blades and some glow wire to give it a try. I'm not the worlds best RC pilot, I can hover nose in, nose out and fly around a little, but not a whole lot more. So I was worried about flying the big trex with 3K worth of electronics on it and crashing it. So I went to the hobby store today and bought some night blades for my little Trex. $45.00 worth of blades seems like a good price to see if I can fly at night. I wired up the glow wire and went out and tried flying it. I flew off three full battery packs in drive way at night, the test was both a success and a bit of fun. So now I have the confidence to be comfortable flying the big trex in an open field at night!
My wifes comment "oh thats pretty it matches our Christmas lights, a Christmas copter!"
A glimpse at the software details....
I want to try and give a glimpse of the details involved with some thing as simple as a swapping the GPS. Ive been working with a GARMIN GPS-18 5Hz gps, it has a serial interface that spits out NMEA sentences. NMEA is a standard protocol. If all you want out of the GPS is position then the GPS units are almost interchangeable. They almost all support the NMEA sentence...GPGGA.
The simple way to process the NEMA sentence is to load the whole thing into a character buffer and parse it. The Netburner library has a nicely written serial driver that makes talking to the serial port pretty painless. Open the port and read characters from it. The serial driver is intrrupt driven, so if you get busy and don't read characters, nothing is lost. To fit this reading and parsing into the main control loop is as simple as adding code to check to see if GPS chars are available and then jumping to a routine to read and process the chars.
You duplicate this three times, GPS, IMU and Telemetry commands.
I thought I'd try to unclutter the main task loop and be a little more efficient. I'm the original author of the Netburner serial driver, so modifying things at the driver level was not too scary. I modified the serial driver to parse the GPGGA sentance one charactor at a time in a state machine and then post to a semaphore to tell the main task that new GPS data is ready. This is a nice routine because it spreads the GPS parsing out in time and has the minimum possible delay.When the sentence checksum is validated the data is ready, all of the floating point data fields have already been parsed out. So the main task only gets notified when data is actually ready. After the GPGGA I expanded the system to capture the proprietary garmin PGRMV sentence that gives me north, east and vertical velocity. Again its all clean and works well. The state machine now knows how to parse two sentences and ignore the others.
This data is processed by the main data processing task. In addition to using it internally it also sends telemetry frames off on the maxstream radio to be displayed and recorded on the ground.
The display program receives a data structure and logs, plots and displays things based on the received data frame type. (The processing for the IMU data is almost identical)
Now I want to upgrade the GPS to the Crescent Vector. The obvious software differences are:
Humm I really want to know vertical velocity... digging in the crescent vector manual I discover that they have a binary message that has vertical velocity, in fact the single binary message has ALL the GPS data I have been capturing in a single message. The Crescent also has heading capability, alas it only outputs heading in a NMEA sentance, not a binary one. so my parsing state machine needs to process a mixed stream of Binary and NMEA messages.
The Binary message is nice in that it starts with $BIN so the beginning looks like a NMEA message, and the simple approach would be to just branch on this NMEA message ,
Its not that simple. My state machine resets its state to 0 whenever it sees a '$' beginning of message,but with the GPS sending binary data there is no guarentee that the binary data won't contain a '$' this breaks my state machine, so now the state machine knows if it is parsing a NMEA or binary data set and reacts accordingly. Also note that in a serial stream of chactors 1234.5678 there is no ambiguity on how to interpit the data. In a binary stream its a little bit more complicated. The GPS sends binary data as a IEEE754 double. standard format, but the GPS sends data in littel endian or intel format and the Coldfire processor I'm using uses big endian or Motorola format.(See Endian). SO I have to convert formats before I use the data. This is still a big win, because the endian conversion is much more efficient than parsing ASCII. Note that I'm already doing the endian conversion on the PC display software so this was not unexpected.
Once I'm parsing the GPS message the system stops responding reliably to telemetry commands....argghhhh! The problem is that If I keep the telemetry link busy sending data from the helicopter to the ground there is no time for the ground station to send data back. Up to this point the telemetry data stream was not too big for the down link pipe, switching from 5 to 10hz GPS pushes me over the edge. So now I write and debug a telemetry throttling routine that tries to keep the telemetry link idle for 50% of the time by throwing away data based on its age and priority.
All seems to be working except none of my telemetry frames have a spot for the GPS heading information, I'd like to keep both the GPS and IMU heading data, so I add a new GPS heading frame type to both the helicopter and the display software. Both areas are pretty modular so this is an easy fix. I label the new data with the same data type tag as the IMU heading data.... .
without remembering that the IMU heading is not floating point but a 0->65536 binary heading.(I worte the IMU parser and display code framework for my air lander over a year a go and have not really modifed it) Hence the GPS heading display is all messed up on the PC so I spend some time debugging the helicopter code to try and figure out why my parser is not properly parsing the GPS heading, only to eventually discover its a problem on the PC side.
This is now almost complete. At some future date I will add HOP and VDOP and signal to noise reporting. I'm now ready to take the whole helicopter outside and see how it works as an assembly. (I've been testing with two external GPS antennas on the roof. The GPS informs me that the antennas are 49.6 cm apart and that my roof has a heading of 172.3 degrees)
I really enjoy reading technical blog posts that give you a sense of the problems and struggles involved with building hardware. In an Ideal world I'd like to cover all of the project in this much detail. The reality of time and the need to sleep conspire against this. I've never been a skilled word smith so writing this saga took 25% as much time as struggling through the code. I don't have the patience to document everything to this level, but I'm going to try and do more posts at this level of detail.
The simple way to process the NEMA sentence is to load the whole thing into a character buffer and parse it. The Netburner library has a nicely written serial driver that makes talking to the serial port pretty painless. Open the port and read characters from it. The serial driver is intrrupt driven, so if you get busy and don't read characters, nothing is lost. To fit this reading and parsing into the main control loop is as simple as adding code to check to see if GPS chars are available and then jumping to a routine to read and process the chars.
You duplicate this three times, GPS, IMU and Telemetry commands.
I thought I'd try to unclutter the main task loop and be a little more efficient. I'm the original author of the Netburner serial driver, so modifying things at the driver level was not too scary. I modified the serial driver to parse the GPGGA sentance one charactor at a time in a state machine and then post to a semaphore to tell the main task that new GPS data is ready. This is a nice routine because it spreads the GPS parsing out in time and has the minimum possible delay.When the sentence checksum is validated the data is ready, all of the floating point data fields have already been parsed out. So the main task only gets notified when data is actually ready. After the GPGGA I expanded the system to capture the proprietary garmin PGRMV sentence that gives me north, east and vertical velocity. Again its all clean and works well. The state machine now knows how to parse two sentences and ignore the others.
This data is processed by the main data processing task. In addition to using it internally it also sends telemetry frames off on the maxstream radio to be displayed and recorded on the ground.
The display program receives a data structure and logs, plots and displays things based on the received data frame type. (The processing for the IMU data is almost identical)
Now I want to upgrade the GPS to the Crescent Vector. The obvious software differences are:
- It provides Heading information
- It updates at 10Hz
- It does not support the garmin PGRMV sentance.
- None of its NMEA sentances have vertical velocity.
Humm I really want to know vertical velocity... digging in the crescent vector manual I discover that they have a binary message that has vertical velocity, in fact the single binary message has ALL the GPS data I have been capturing in a single message. The Crescent also has heading capability, alas it only outputs heading in a NMEA sentance, not a binary one. so my parsing state machine needs to process a mixed stream of Binary and NMEA messages.
The Binary message is nice in that it starts with $BIN so the beginning looks like a NMEA message, and the simple approach would be to just branch on this NMEA message ,
Its not that simple. My state machine resets its state to 0 whenever it sees a '$' beginning of message,but with the GPS sending binary data there is no guarentee that the binary data won't contain a '$' this breaks my state machine, so now the state machine knows if it is parsing a NMEA or binary data set and reacts accordingly. Also note that in a serial stream of chactors 1234.5678 there is no ambiguity on how to interpit the data. In a binary stream its a little bit more complicated. The GPS sends binary data as a IEEE754 double. standard format, but the GPS sends data in littel endian or intel format and the Coldfire processor I'm using uses big endian or Motorola format.(See Endian). SO I have to convert formats before I use the data. This is still a big win, because the endian conversion is much more efficient than parsing ASCII. Note that I'm already doing the endian conversion on the PC display software so this was not unexpected.
Once I'm parsing the GPS message the system stops responding reliably to telemetry commands....argghhhh! The problem is that If I keep the telemetry link busy sending data from the helicopter to the ground there is no time for the ground station to send data back. Up to this point the telemetry data stream was not too big for the down link pipe, switching from 5 to 10hz GPS pushes me over the edge. So now I write and debug a telemetry throttling routine that tries to keep the telemetry link idle for 50% of the time by throwing away data based on its age and priority.
All seems to be working except none of my telemetry frames have a spot for the GPS heading information, I'd like to keep both the GPS and IMU heading data, so I add a new GPS heading frame type to both the helicopter and the display software. Both areas are pretty modular so this is an easy fix. I label the new data with the same data type tag as the IMU heading data.... .
without remembering that the IMU heading is not floating point but a 0->65536 binary heading.(I worte the IMU parser and display code framework for my air lander over a year a go and have not really modifed it) Hence the GPS heading display is all messed up on the PC so I spend some time debugging the helicopter code to try and figure out why my parser is not properly parsing the GPS heading, only to eventually discover its a problem on the PC side.
This is now almost complete. At some future date I will add HOP and VDOP and signal to noise reporting. I'm now ready to take the whole helicopter outside and see how it works as an assembly. (I've been testing with two external GPS antennas on the roof. The GPS informs me that the antennas are 49.6 cm apart and that my roof has a heading of 172.3 degrees)
I really enjoy reading technical blog posts that give you a sense of the problems and struggles involved with building hardware. In an Ideal world I'd like to cover all of the project in this much detail. The reality of time and the need to sleep conspire against this. I've never been a skilled word smith so writing this saga took 25% as much time as struggling through the code. I don't have the patience to document everything to this level, but I'm going to try and do more posts at this level of detail.
Friday, December 07, 2007
Gingerbread cookies and GPS
I've been experimenting with a Crescent Vector GPS from Hemisphere GPS. It uses two antennas 1/2 meter apart to gove heading as well as GPS position at 10Hz. The only problem is that the helicopter test bed (and the rocket) is an electrically noisy place. So I built an adapter module that has an isolated DC-DC converter, a logic isolator and RS-232 level converters on a small PCB. I then needed to mount the whole thing in some kind of shielded enclosure. I've been reading the "Jack Crossfire blog" about the trials and tribulations of making a autonomous UAV helicopter. He used an altoids tin to shield his GPS, I'm using a gingerbread cookie tin. (Altoids was too small for the vector).
The back side....
With the top on....
And finally a picture of the carbon fiber frame that mounts to the helicopter and holds the two GPS antennas.
I should be ready to fly this contraption tonight, but Southern California are in the midst of a big rain storm and thats not conducive to flying the helicopter.
The back side....
With the top on....
And finally a picture of the carbon fiber frame that mounts to the helicopter and holds the two GPS antennas.
I should be ready to fly this contraption tonight, but Southern California are in the midst of a big rain storm and thats not conducive to flying the helicopter.
Sunday, December 02, 2007
Helicopter testing an a new notional vehicle.
I reviewd the telemetry from the last helicopter flight and I think I have finally resolved all my issues with telemetry and hardware. No glitches in either control or data , my telemetry logger logged correctly to SD media so I will never again loose telemetry data from a failure to save, or a dead laptop battery. I got no GPS data, but it's probably because I did not give ehough time for the GPS to lock prior to flight and it did not acquire in the high vib helicopter environement. I'm planning to swith GPS receivers before the next flight in any case.
A new notional vehicle. And a plan forward.
The big question with insufficient data is:
Are our rocket motors really robust for multiple firings and throttling?
We have fired multiple times for long runs within an hour, we have throttled, but we have also had failures. We need to run the motor through several simulated missions. That is follow the LLC flight throttle profile and restart in less than 1/2 hour. Until we have done that several times we do not know if we have a workable design or not.
If our motors work then we will probably continue with a 4 motor vehicle. If they do not we will probably develop a single larger motor. The notional design for the vehicle branches on that question.
Assuming we have a working motor the the current notional design is as shown above. The key is that the weight is supported by a simple pad under the tank and the landing gear only keeps the vehicle from tipping over.
If the motors don't work then we are probably going to build a single engine vehicle with spherical tanks. There are really only two configurations that seem to make sens, the Quad and the Pixel design. Pixel has balance feed problems, but is structurally more efficient. The one drawback I see to the armadillo module design is the mass of the landing gear and the fact that the motor is very close to the ground. I've ordered some hemispheres from AMS industries and they should be here some time in January.
A new notional vehicle. And a plan forward.
The big question with insufficient data is:
Are our rocket motors really robust for multiple firings and throttling?
We have fired multiple times for long runs within an hour, we have throttled, but we have also had failures. We need to run the motor through several simulated missions. That is follow the LLC flight throttle profile and restart in less than 1/2 hour. Until we have done that several times we do not know if we have a workable design or not.
If our motors work then we will probably continue with a 4 motor vehicle. If they do not we will probably develop a single larger motor. The notional design for the vehicle branches on that question.
Assuming we have a working motor the the current notional design is as shown above. The key is that the weight is supported by a simple pad under the tank and the landing gear only keeps the vehicle from tipping over.
If the motors don't work then we are probably going to build a single engine vehicle with spherical tanks. There are really only two configurations that seem to make sens, the Quad and the Pixel design. Pixel has balance feed problems, but is structurally more efficient. The one drawback I see to the armadillo module design is the mass of the landing gear and the fact that the motor is very close to the ground. I've ordered some hemispheres from AMS industries and they should be here some time in January.
Tuesday, November 27, 2007
Tank and Helicopter Testing.
Today at lunch I flew the helicopter again and I seem to have solved all the electronics glitches. I changed from a 72Mhz RC Rx to one of the new 2.4Ghz units and it was much smoother. I'll analyze the recorded telemetry in the next day or so and post the results.
This afternoon my son started hydro testing all of the vehicle tanks. We had planed to test the entire vehicle with plumbing and everything, but with recent tank failures on the test stand and our sample heat treated tank we decided to individually test the vehicle tanks. The tanks were designed to be hydroed to 500PSI. However for the 90 second vehicle we did not ned to go so high. We backed off to 450PSI and still did not fair well. We tested all 8 tanks and got the following results: Failures at 350, 385,415 and 435. Four tanks passed all the way to 455. Since thanks are welded together in pairs we have one good pair, that will go on the test stand. The rest of the vehicle tanks are probably scrap. All four tanks failed in exactly the same way, at the interface between the endcap and the tubular tank. The weld stayed attached to the end cap and the weld pulled away from or failed at the tubular part of the tank. The tubular part is 6063 and the end cap 6061 so this failure mode sort of makes sense.
This result really complicates the decision process. What do we have from last years effort? We have 1/4 of a vehicle tank. We have some structure. We don't have valves, plumbing electronics we can use. We think (confidence 80%) that we have motors that will work. Do we scrap the design for a simpler solution or do we fix what we know is broken? There is a strong desire to start over from scratch. If I were to start again I think I'd build a 3/4 scale pixel. However this would mean scrapping the one part we think we have working the motor. Arghhhh decisions and only 11 months to be ready.
This afternoon my son started hydro testing all of the vehicle tanks. We had planed to test the entire vehicle with plumbing and everything, but with recent tank failures on the test stand and our sample heat treated tank we decided to individually test the vehicle tanks. The tanks were designed to be hydroed to 500PSI. However for the 90 second vehicle we did not ned to go so high. We backed off to 450PSI and still did not fair well. We tested all 8 tanks and got the following results: Failures at 350, 385,415 and 435. Four tanks passed all the way to 455. Since thanks are welded together in pairs we have one good pair, that will go on the test stand. The rest of the vehicle tanks are probably scrap. All four tanks failed in exactly the same way, at the interface between the endcap and the tubular tank. The weld stayed attached to the end cap and the weld pulled away from or failed at the tubular part of the tank. The tubular part is 6063 and the end cap 6061 so this failure mode sort of makes sense.
This result really complicates the decision process. What do we have from last years effort? We have 1/4 of a vehicle tank. We have some structure. We don't have valves, plumbing electronics we can use. We think (confidence 80%) that we have motors that will work. Do we scrap the design for a simpler solution or do we fix what we know is broken? There is a strong desire to start over from scratch. If I were to start again I think I'd build a 3/4 scale pixel. However this would mean scrapping the one part we think we have working the motor. Arghhhh decisions and only 11 months to be ready.
Sunday, November 18, 2007
Back in the swing
Starting to get back into it. I made some sugar rocket parts for Kevin of FAR on the Lathe. This generated a bunch of aluminum chips that swiftly made their way into the house. Since I'm trying to reduce the amount of $$ spent on the
"Calm angry wife with aluminum chip in her foot by purchasing flowers"
budget line item.
I've decided that the lathe needs to move away from the exit door. I can do this by swapping the lathe and a work bench. So next week I need to move some power wiring and add another layer of waterproof sheet rock and or stainless steel sheeting behind the lathes new home. I'm also going to install a troll at the exit door whose job is to throw you to the ground and remove all the metal chips. If you know anyone marketing such a creature please let me know.
On a slightly less serious note I flew the helicopter a number of times on Saturday and all the electronics seem to be working.I've got GPS, IMU, Ultrasonic altitude sensor, compass, RC receiver,telemetry transceiver and netburner cpu all running on an electric Trex 600. I finally solved the GPS problem by moving it to the end of the tail boom. It is all functional, with the current setup the RC receiver is hooked to the CPU and the servos are all driven by the CPU. Right now the CPU just echoes the RC receiver commands and the vehicle is flown manually, but it proves out all the hardware. These tests included the ground telemetry box and RF to Ethernet translator I was showing at the xprize cup. There were a bunch of guys at FAR for a solid motor class and one of them captured me flying the helicopter.
"Calm angry wife with aluminum chip in her foot by purchasing flowers"
budget line item.
I've decided that the lathe needs to move away from the exit door. I can do this by swapping the lathe and a work bench. So next week I need to move some power wiring and add another layer of waterproof sheet rock and or stainless steel sheeting behind the lathes new home. I'm also going to install a troll at the exit door whose job is to throw you to the ground and remove all the metal chips. If you know anyone marketing such a creature please let me know.
On a slightly less serious note I flew the helicopter a number of times on Saturday and all the electronics seem to be working.I've got GPS, IMU, Ultrasonic altitude sensor, compass, RC receiver,telemetry transceiver and netburner cpu all running on an electric Trex 600. I finally solved the GPS problem by moving it to the end of the tail boom. It is all functional, with the current setup the RC receiver is hooked to the CPU and the servos are all driven by the CPU. Right now the CPU just echoes the RC receiver commands and the vehicle is flown manually, but it proves out all the hardware. These tests included the ground telemetry box and RF to Ethernet translator I was showing at the xprize cup. There were a bunch of guys at FAR for a solid motor class and one of them captured me flying the helicopter.
Monday, November 12, 2007
Tanks, good news bad news...
We originally hydroed one tank to failure. It failed at 495 PSI.
We made the end cap that failed thicker, and assumed we fixed the problem.
Today I asked my son to hydro the test stand to 500 PSI since we had not done so. The first tank in the test stand failed at 475. He then hydro tested the tank we had heat treated. It failed at 425. So to complete the set we tested the other tank on the test stand to failure it failed at 560PSI. All three failed in exactly the same spot in the weld between the end cap and tank end. Its clear that our quality control needs some work. On Tuesday we will hydro all 8 tanks on the actual vehicle and see how that goes. Its really hard to tell if the failure is in the heat effected zone on the margin next to the weld, or if the welds them selves are too thin.
We made the end cap that failed thicker, and assumed we fixed the problem.
Today I asked my son to hydro the test stand to 500 PSI since we had not done so. The first tank in the test stand failed at 475. He then hydro tested the tank we had heat treated. It failed at 425. So to complete the set we tested the other tank on the test stand to failure it failed at 560PSI. All three failed in exactly the same spot in the weld between the end cap and tank end. Its clear that our quality control needs some work. On Tuesday we will hydro all 8 tanks on the actual vehicle and see how that goes. Its really hard to tell if the failure is in the heat effected zone on the margin next to the weld, or if the welds them selves are too thin.
Support the troups.
Every year for the last 6 years I've supported http://www.lbeh.org/
Its an effort to buy plane tickets for enlisted men and women to allow them to fly home for the holidays. Its an all volunteer's effort last year they spent 96% of what was donated on the troops.
(2.5 % of the take went to PayPal fees.)
This is the one and only time of the year I'll post a request on the blog.
Its an effort to buy plane tickets for enlisted men and women to allow them to fly home for the holidays. Its an all volunteer's effort last year they spent 96% of what was donated on the troops.
(2.5 % of the take went to PayPal fees.)
This is the one and only time of the year I'll post a request on the blog.
Sunday, November 11, 2007
Valves, Valves,Valves and Valves...
We started this project last year looking for light weight actuators. We assumed that we could just use off the shelf ball valves.
When we sit down and evaluate the response time needed and the hysterisis of ball valves then we realize that in the small sizes we need ball valves are problematic. There is slop between the ball and the stem and rotationally the ball valve is not very linear. We have also had leak and wear problems with our ball valves. So given the actuator we like we are now trying to find a better valve to go under it. Today we manually tested the following valves with 200 PSI liquid nitrogen:
Large O2 rated solenoid. (Cryogenic solenoids are larger and heaver)
Failed stuck open.
Buttery fly valve we were using as a throttling vale as the only valve.
Failed Leaking, very very non-linear.
SwageLoc Plug valve with 4 different kinds of alternate o-rings including
$70.00 of Kalrez o-rings.
All rotating seals failed at Ln2 Temperatures.
Small Brass Ball Valve.
Froze Solid and Jammed.
Small SS Ball valve.
Worked, sealed and had signiifcantly more hysteresis at LN2 temps than at room temperature.
For my next bout of insanity Paul builds a valve....
This is my "Simple" custom valve idea. I build a small linear valve in a copper plumbing tee. Making cryogenic seals work is hard, so I cheat. I add some heat to the end of the thin wall stainless to keep the seal end warm. The force necessary to operate this valve is within the range of the small fast robot servos I've been using. the valve is operated by pulling the stainless rod in and out. The Cage pins are there to make the ball stay in place. I'm concerned that the flow will make the ball chatter. If the seals give me trouble I can go to an electroformed bellows.
From Servometer
This makes me wonder if I should try a stock off the shelf.... bellows valve
When we sit down and evaluate the response time needed and the hysterisis of ball valves then we realize that in the small sizes we need ball valves are problematic. There is slop between the ball and the stem and rotationally the ball valve is not very linear. We have also had leak and wear problems with our ball valves. So given the actuator we like we are now trying to find a better valve to go under it. Today we manually tested the following valves with 200 PSI liquid nitrogen:
Large O2 rated solenoid. (Cryogenic solenoids are larger and heaver)
Failed stuck open.
Buttery fly valve we were using as a throttling vale as the only valve.
Failed Leaking, very very non-linear.
SwageLoc Plug valve with 4 different kinds of alternate o-rings including
$70.00 of Kalrez o-rings.
All rotating seals failed at Ln2 Temperatures.
Small Brass Ball Valve.
Froze Solid and Jammed.
Small SS Ball valve.
Worked, sealed and had signiifcantly more hysteresis at LN2 temps than at room temperature.
For my next bout of insanity Paul builds a valve....
This is my "Simple" custom valve idea. I build a small linear valve in a copper plumbing tee. Making cryogenic seals work is hard, so I cheat. I add some heat to the end of the thin wall stainless to keep the seal end warm. The force necessary to operate this valve is within the range of the small fast robot servos I've been using. the valve is operated by pulling the stainless rod in and out. The Cage pins are there to make the ball stay in place. I'm concerned that the flow will make the ball chatter. If the seals give me trouble I can go to an electroformed bellows.
From Servometer
This makes me wonder if I should try a stock off the shelf.... bellows valve
Thursday, November 08, 2007
Wednesday, November 07, 2007
The most common misconception.
I've had at least 50 people tell me the following:
(Including more than one scientist with a hard science PHD)
Why not put your rocket engine on top so the vehicle will be naturally stable.
This is wrong. It jives with our natural experience of the world, but it is wrong.
A rocket has no natural preference for thrusting UP. The rocket will thrust in whatever direction you point it. This is unusual in out natural experience. It you hang something on a rope the rope has the natural tendency to dangle straight down and only apply force in the up direction. If you attach something to a balloon the balloon only pulls straight up.
So given that the rocket will thrust in whatever direction its pointed and has no natural tendency to point up the rocket can't add any stability.
So if the motor can't add stability is there anything you can do for gravity to add stability? If the gravity field was uniform it would operate on the center of mass appling no torque to the vehicle and thus no stability. On the surface of the earth this is basically the case. The gravity field varies with the square of the radius. In orbit this slight difference can be used to stabilize a spacecraft, but on the surface the effect is so slight as to be undetectable. (On a 2meter high object gravity is 0.999999969 as strong on the top as it is on the bottom)
Our intuition is not completely wrong with respect to where the rocket motor goes, if it's center of thrust is not pointing through the center of mass then the rocket engine will apply a torque and the vehicle will spin. The current unreasonable rocket design has four engines that must be balanced to keep the vehicle from spinning, so in this sense a single rocket motor pointing toward the center of mass would keep the rocket pointed in a constant direction, but that direction would not be preferentially up without some kind of external control.
(Including more than one scientist with a hard science PHD)
Why not put your rocket engine on top so the vehicle will be naturally stable.
This is wrong. It jives with our natural experience of the world, but it is wrong.
A rocket has no natural preference for thrusting UP. The rocket will thrust in whatever direction you point it. This is unusual in out natural experience. It you hang something on a rope the rope has the natural tendency to dangle straight down and only apply force in the up direction. If you attach something to a balloon the balloon only pulls straight up.
So given that the rocket will thrust in whatever direction its pointed and has no natural tendency to point up the rocket can't add any stability.
So if the motor can't add stability is there anything you can do for gravity to add stability? If the gravity field was uniform it would operate on the center of mass appling no torque to the vehicle and thus no stability. On the surface of the earth this is basically the case. The gravity field varies with the square of the radius. In orbit this slight difference can be used to stabilize a spacecraft, but on the surface the effect is so slight as to be undetectable. (On a 2meter high object gravity is 0.999999969 as strong on the top as it is on the bottom)
Our intuition is not completely wrong with respect to where the rocket motor goes, if it's center of thrust is not pointing through the center of mass then the rocket engine will apply a torque and the vehicle will spin. The current unreasonable rocket design has four engines that must be balanced to keep the vehicle from spinning, so in this sense a single rocket motor pointing toward the center of mass would keep the rocket pointed in a constant direction, but that direction would not be preferentially up without some kind of external control.
Monday, November 05, 2007
The Agony of the valves.
After spending a few days at XPC it's very clear that our system is too complex.
KISS Keep It Simple Stupid.
The temptation is very great to start over from scratch and redesign everything. If I were to start again I would design something that looks a lot like pixel or the Armadillo Quad, a Single engine. The counter to this is that the only thing we really need to finish our vehicle is fast robust reliable valves. Its always tempting to trade the devil you know for the invisible devil lying in the green grass on the other side of the fence. Everyone I've talked to in Alt space has had valve problems of one kind or another.
My core problem is that I need very fast (50 to 100msec) control of the engine thrust to maintain reliable attitude control. Our vehicle is relatively small so that it's overall rotational inertia is low, and the motors are on the very outside of the vehicle this combines to require fast/precise control of the motor thrust.
How fast?
We can do some freshman physics and figure that out.
Lets assume that the vehicle is 2m diameter sphere.
(This is a slightly pessimistic view of our inertia the vehicle will be more stable than this)
I=2 mr^2/5 =2m/5
We are hovering with 4 motors. The total required lift is mg
So the force for each motor is mg/4
The motors are thrusting on a 1 meter lever arm from the Cg.
Now assume we can very the thrust in 1% steps around nominal.
Assume we increase the thrust in one motor by 1% and decrease the opposite motor by 1%
torque=1 * 2%mg/4
angular acceleration alpha=torque /I =(1*0.02mg/4)/(2m/5)
alpha = 0.0125g (notice m drops out)
or assuming g=9.8m/sec
alpha = .1225 radians/sec ^2
If we want 1 degree control of the vehicle 1 degree = 0.01745 radians.
The rotation is just like linear acceleration angle = (alpha*t^2)/2
So for 1% motor change a 1 degree error occurs in t=.53 seconds.
We would like our control to be about 5x to 10x the speed hence we need a 50msec valve.
How do we get such fast control:
Monster actuators and normal ball valves.
Pros:
95% Off the shelf.
Cons:
Lots of hysteresis (3 to 5%), Seals wear out quickly.
Hysteresis really complicates the control system.
Voice coil driven piloted spool valves.
Pros:
Such things exist for Hydraulic systems.
Control response as fast as 15msec 0 to 100%
Hysteresis 0.1% Basically a perfect valve.
Cons:
No off the shelf valves will work for LOX
Heavy
Expensive.
Serious engineering effort to build such a valve in a Lox compatible way.
More complicated Odd combinations.
One can start doing things that add significant complexity:
Adding modulated water injection.
Modulating just the fuel supply while leaving the LOX on a slow actuator.
Using a pile of fast solenoid valves
One fast Solenoid valve as trim with Slow ball valve following.
Pros:
Potentially the lowest cost option.
Cons:
Violates KISS
Requires a lot of development testing.
I'm sure I'll post more on this in the coming days and weeks.
KISS Keep It Simple Stupid.
The temptation is very great to start over from scratch and redesign everything. If I were to start again I would design something that looks a lot like pixel or the Armadillo Quad, a Single engine. The counter to this is that the only thing we really need to finish our vehicle is fast robust reliable valves. Its always tempting to trade the devil you know for the invisible devil lying in the green grass on the other side of the fence. Everyone I've talked to in Alt space has had valve problems of one kind or another.
My core problem is that I need very fast (50 to 100msec) control of the engine thrust to maintain reliable attitude control. Our vehicle is relatively small so that it's overall rotational inertia is low, and the motors are on the very outside of the vehicle this combines to require fast/precise control of the motor thrust.
How fast?
We can do some freshman physics and figure that out.
Lets assume that the vehicle is 2m diameter sphere.
(This is a slightly pessimistic view of our inertia the vehicle will be more stable than this)
I=2 mr^2/5 =2m/5
We are hovering with 4 motors. The total required lift is mg
So the force for each motor is mg/4
The motors are thrusting on a 1 meter lever arm from the Cg.
Now assume we can very the thrust in 1% steps around nominal.
Assume we increase the thrust in one motor by 1% and decrease the opposite motor by 1%
torque=1 * 2%mg/4
angular acceleration alpha=torque /I =(1*0.02mg/4)/(2m/5)
alpha = 0.0125g (notice m drops out)
or assuming g=9.8m/sec
alpha = .1225 radians/sec ^2
If we want 1 degree control of the vehicle 1 degree = 0.01745 radians.
The rotation is just like linear acceleration angle = (alpha*t^2)/2
So for 1% motor change a 1 degree error occurs in t=.53 seconds.
We would like our control to be about 5x to 10x the speed hence we need a 50msec valve.
How do we get such fast control:
Monster actuators and normal ball valves.
Pros:
95% Off the shelf.
Cons:
Lots of hysteresis (3 to 5%), Seals wear out quickly.
Hysteresis really complicates the control system.
Voice coil driven piloted spool valves.
Pros:
Such things exist for Hydraulic systems.
Control response as fast as 15msec 0 to 100%
Hysteresis 0.1% Basically a perfect valve.
Cons:
No off the shelf valves will work for LOX
Heavy
Expensive.
Serious engineering effort to build such a valve in a Lox compatible way.
More complicated Odd combinations.
One can start doing things that add significant complexity:
Adding modulated water injection.
Modulating just the fuel supply while leaving the LOX on a slow actuator.
Using a pile of fast solenoid valves
One fast Solenoid valve as trim with Slow ball valve following.
Pros:
Potentially the lowest cost option.
Cons:
Violates KISS
Requires a lot of development testing.
I'm sure I'll post more on this in the coming days and weeks.
Wednesday, October 31, 2007
Unreasonable Plans
I enjoyed visiting with all the people that stopped by to visit at the Xprize cup.
It was really heartbreaking that Armadillo did not win anything. Watching this unfold shows how hard this problem really is and makes me realize how very far from being ready we really are. I've been trying to work up a plan of action for the next year and the rough outline looks something like this:
1)Start working on the command and control code on the Helicopter to get the telemetry and mission planning stuff out of the way. This can be done close to home without the major expedition aspects of going out to FAR. Id like to have this 100% resolved by Christmas.
2)Work on resolving my valve issues, this will probably be one of the following:
3)Resurrect the test stand even if it means making new tanks and resolving our engine igntion issues once and for all. Before we do any vehicle work I want to run a motor on the test stand with throttling and simulate a full LLC mission including the 30 minute turnaround. I want to do this over and over until we get it right. This may get as involved as developing a new injector and igniter design. I'd like to start this testing in January.
4)Once 1,2,3 are done rebuild the vehicle and start tethered testing. If all goes well I could see tethered testing as soon as Febuary 1 ~ 4 months from now. After watching Armadillo I know I want to make some architectural changes. The primary one will be for the vehicle to automatically test all its valve actuators and sensors with minimal human intervention.
When I get to the point of testing a full vehicle I need to find a different transportation method. I'd be inclinded to buy a used flatbed or Box truck, but I can't park that near me, so I'd need to find someplace in San Diego to park it without spending a fortune. Anyone with an empty lot in San Diego where I can park a 20' box truck off and on for a year?
It was really heartbreaking that Armadillo did not win anything. Watching this unfold shows how hard this problem really is and makes me realize how very far from being ready we really are. I've been trying to work up a plan of action for the next year and the rough outline looks something like this:
1)Start working on the command and control code on the Helicopter to get the telemetry and mission planning stuff out of the way. This can be done close to home without the major expedition aspects of going out to FAR. Id like to have this 100% resolved by Christmas.
2)Work on resolving my valve issues, this will probably be one of the following:
- Rework the tonegowa driven valves for less backlash and better electronics. (Open servo based?) This is my preference.
- Use higher pressure Butterfly valves as the sole valve. This is my sons preference.
- Design a custom valve using either rotary or poppet style valves. This is no-ones preference. (I'm thinking a bearing supported plug valve sort of like this)
3)Resurrect the test stand even if it means making new tanks and resolving our engine igntion issues once and for all. Before we do any vehicle work I want to run a motor on the test stand with throttling and simulate a full LLC mission including the 30 minute turnaround. I want to do this over and over until we get it right. This may get as involved as developing a new injector and igniter design. I'd like to start this testing in January.
4)Once 1,2,3 are done rebuild the vehicle and start tethered testing. If all goes well I could see tethered testing as soon as Febuary 1 ~ 4 months from now. After watching Armadillo I know I want to make some architectural changes. The primary one will be for the vehicle to automatically test all its valve actuators and sensors with minimal human intervention.
When I get to the point of testing a full vehicle I need to find a different transportation method. I'd be inclinded to buy a used flatbed or Box truck, but I can't park that near me, so I'd need to find someplace in San Diego to park it without spending a fortune. Anyone with an empty lot in San Diego where I can park a 20' box truck off and on for a year?
Tuesday, October 23, 2007
Good Luck to Armadillo
I will be leaving for Holloman some time Wednesday afternoon.
Before I go I want to wish armadillo the best of luck in their NG-LLC efforts.
I will be rooting for them!
They have worked very hard and have been a real class act.
Good luck to John and the rest of the Armadillo team!
Before I go I want to wish armadillo the best of luck in their NG-LLC efforts.
I will be rooting for them!
They have worked very hard and have been a real class act.
Good luck to John and the rest of the Armadillo team!
Long night we are ok...
The wind switched directions and it looks like the witch fire will not reach the coast. Our thoughts are with the 500,000 people that have been evacuated and don't know the status of their homes. It looks like 1200+ homes have been destroyed in the last 36 hours. There are still areas in San Deigo county where people are still losing homes. If the wind switches we could still be at risk, but
it looks 200% better than is did 24 hours ago.
it looks 200% better than is did 24 hours ago.
Monday, October 22, 2007
San Diego fires
We live in Solana Beach, the city has just said
"Everyone is being asked to plan, pack and evacuate ahead of
being required to do so. "
It looks like the witch creek fire is likely going to burn all the way to the coast. Where it crosses I5 and hits the coast is pretty much up in the air. It looks like its going to cross somewhere near our house +/- 5 miles. We live in a fairly dense residential neighborhood, if it gets to us this fire is going to be a truely note worthy disaster. I'm going home from work to join the rest of the family and get prepared to leave. It probably won't be to the coast for another 12-18 hours , but it looks like nothing is going to stop it. Wish us luck, we hope to see all of you this coming weekend at Holloman. I'll let everyone know how it turns out Tuesday.
Paul
"Everyone is being asked to plan, pack and evacuate ahead of
being required to do so. "
It looks like the witch creek fire is likely going to burn all the way to the coast. Where it crosses I5 and hits the coast is pretty much up in the air. It looks like its going to cross somewhere near our house +/- 5 miles. We live in a fairly dense residential neighborhood, if it gets to us this fire is going to be a truely note worthy disaster. I'm going home from work to join the rest of the family and get prepared to leave. It probably won't be to the coast for another 12-18 hours , but it looks like nothing is going to stop it. Wish us luck, we hope to see all of you this coming weekend at Holloman. I'll let everyone know how it turns out Tuesday.
Paul
Friday, October 19, 2007
Unreasonable Ideas
For awhile I've been contemplating making some personal or political posts on this blog. I don't really want to mix the messages that way. Today I started a new blog unreasonableideas with a sad personal note. I'll continue posting rocket stuff here, and I'll post personal stuff there.
Wednesday, October 10, 2007
We will be displaying at XPC.
I've been having an internal debate about coming to the Xprize cup as an exhibitor or strictly as an observer. Unlike the other teams that are are looking to raise capital and awareness, we are not yet trying to do that. So I was hesitant to spend the money necessary to transport stuff to the show. I've decided that it would serve my larger goals of showing that small teams and individuals can do significant things in "space development" so we will be there.
We will be bringing the complete vehicle minus some valves and plumbing.
We may also bring the test stand carcass, the test helicopter, and and a video display. If you are coming to the show stop by and say hi.
On a personal note I went to the Plaster Blaster event last Saturday and spent the day watching a huge array of people launch rockets of all shapes and sizes. It was my first trip to a high power rocket event. The Xwing (http://rocketdungeon.blogspot.com/2007/10/empire-struck-back-may-x-wing-rip.html)was very cool, but all in all I found the event somewhat depressing. There were several cool projects, but none of the projects seemed to be advancing the state of the art. In some ways it seemed like a conspicuous consumption event. To be fair I saw a lot of families there and that was a very cool aspect to the event. My wife chastised me for this attitude, and said who am I to be judging other peoples efforts. She is probably right.
Lastly I've not done ANY thing on the rocket in the last month, I needed the break. I've been trying to catch up at work, organize my office and play some video games... (online chess and replaying all the original starcraft scenarios.)
We will be bringing the complete vehicle minus some valves and plumbing.
We may also bring the test stand carcass, the test helicopter, and and a video display. If you are coming to the show stop by and say hi.
On a personal note I went to the Plaster Blaster event last Saturday and spent the day watching a huge array of people launch rockets of all shapes and sizes. It was my first trip to a high power rocket event. The Xwing (http://rocketdungeon.blogspot.com/2007/10/empire-struck-back-may-x-wing-rip.html)was very cool, but all in all I found the event somewhat depressing. There were several cool projects, but none of the projects seemed to be advancing the state of the art. In some ways it seemed like a conspicuous consumption event. To be fair I saw a lot of families there and that was a very cool aspect to the event. My wife chastised me for this attitude, and said who am I to be judging other peoples efforts. She is probably right.
Lastly I've not done ANY thing on the rocket in the last month, I needed the break. I've been trying to catch up at work, organize my office and play some video games... (online chess and replaying all the original starcraft scenarios.)
Wednesday, September 19, 2007
400 Days till XPC 2008
I will boldly predict that there will be NG-LLC prize money for 2008. We only have ~400 days until the 2008 XPC, 280 days till the FAA permit app must be accepted. What are our plans? In no particular order...
1)Simplify.
Make one valve work, not two,
Go to blow down pressurization (for at least the 90 sec vehicle.)
2)Add more diagnostic automation.
Add some more feedback to the open loop vales so we can automagically determine their health.We need both position and current feedback from each valve. I may convert the valves to www.openservo.org derived control electronics.
3)Build a more robust vehicle.
Most plumbing, stainless not aluminum.
sturdier landing gear.
4)Find a more benign transport system.
5)Try other fuels and gasses
IPA (cleaner) and E85 cheaper.
Do at least one burn with 100% Nitrogen pressurization.
With our long thin tanks it might not be as bad as it is for Carmacks Spherical tanks. I've been told that a shot of He followed by N2 pressurization is not bad. the Russians use Nitrogen to pressurize their Lox tanks, and Nitrogen is a Lot Lot Lot cheaper than Hydrogen.
(Self presurized Lox might be similar....)
7)Put better data logging software in place.
( I write embedded S/W for a living and the shoemakers kids have no shoes.)
8)Convert the simulator to a hardware in loop tester.
9)Make the control system fly the helicopter, and publish ALL the results.
10)Try a impinging injector rather than a pintile.
11)Try Charles Pooleys Lox pre-burner idea.
12)Build and leave set up a good valve and injector flow test setup.
1)Simplify.
Make one valve work, not two,
Go to blow down pressurization (for at least the 90 sec vehicle.)
2)Add more diagnostic automation.
Add some more feedback to the open loop vales so we can automagically determine their health.We need both position and current feedback from each valve. I may convert the valves to www.openservo.org derived control electronics.
3)Build a more robust vehicle.
Most plumbing, stainless not aluminum.
sturdier landing gear.
4)Find a more benign transport system.
5)Try other fuels and gasses
IPA (cleaner) and E85 cheaper.
Do at least one burn with 100% Nitrogen pressurization.
With our long thin tanks it might not be as bad as it is for Carmacks Spherical tanks. I've been told that a shot of He followed by N2 pressurization is not bad. the Russians use Nitrogen to pressurize their Lox tanks, and Nitrogen is a Lot Lot Lot cheaper than Hydrogen.
(Self presurized Lox might be similar....)
7)Put better data logging software in place.
( I write embedded S/W for a living and the shoemakers kids have no shoes.)
8)Convert the simulator to a hardware in loop tester.
9)Make the control system fly the helicopter, and publish ALL the results.
10)Try a impinging injector rather than a pintile.
11)Try Charles Pooleys Lox pre-burner idea.
12)Build and leave set up a good valve and injector flow test setup.
Monday, September 17, 2007
Quick Update on LLC 2007
Since I posted my Out of Time post, a couple of teams have
announced to the world what they had told me in private.
Acuity:
Very Secret I know almost nothign about their progress. They had an unflown vehicle at the 2006 XPC, they could be the dark horse. They have an interesting control scheme that always made me wonder.
Armadillo:
As ready as anyone could be, the "Gold Standard"
Bon Nova:
They have posted a couple of very quick Rocket Motor videos, the longest being several seconds. We posted our 106 Second firing in April and we did not make it. They have posted no vehicle hardware pictures.
Masten:
They just announced on their blog they are out for 2007.
Micro space:
Failed to attend the required team meeting in Aug.
Paragon Labs:
They have a very credible vehicle, well constructed and professional Another team that is somewhat secretive and an unknown. They posted finished airframe and rocket firing pictures in Aug. They were planning to have throttling via movable pintile in the all aluminum motor, while technically very cool, not easy to do and Armadillo was never able to make an all aluminum motor last without melting.
Speed Up:
Announced that they will not make 2007.
Unreasonable Rocket:
Announced we will not make it in 2007.
Team X :
Pulled out before the Last team summit.
announced to the world what they had told me in private.
Acuity:
Very Secret I know almost nothign about their progress. They had an unflown vehicle at the 2006 XPC, they could be the dark horse. They have an interesting control scheme that always made me wonder.
Armadillo:
As ready as anyone could be, the "Gold Standard"
Bon Nova:
They have posted a couple of very quick Rocket Motor videos, the longest being several seconds. We posted our 106 Second firing in April and we did not make it. They have posted no vehicle hardware pictures.
Masten:
They just announced on their blog they are out for 2007.
Micro space:
Failed to attend the required team meeting in Aug.
Paragon Labs:
They have a very credible vehicle, well constructed and professional Another team that is somewhat secretive and an unknown. They posted finished airframe and rocket firing pictures in Aug. They were planning to have throttling via movable pintile in the all aluminum motor, while technically very cool, not easy to do and Armadillo was never able to make an all aluminum motor last without melting.
Speed Up:
Announced that they will not make 2007.
Unreasonable Rocket:
Announced we will not make it in 2007.
Team X :
Pulled out before the Last team summit.
Sunday, September 16, 2007
Out of Time
The end of 2007
We took the complete vehicle out to FAR to do a four engine static test this weekend. We had a number of transport issues. We finally settled on a U haul trailer.
With the motors mounted the vehicle did not fit. So we unmounted the four motors. This left a fair bit dangling plumbing. Realize that this is a trailer with leaf springs and no shocks. The trailer is rated for 4500LBs we put 230 lbs in it. WE then drove for three hours to Mojave. We stopped early in the trip to check the tie downs and again at Mojave. By the time we reached the Arco station in Mojave we had either damaged the plumbing or shaken the hardware off of the valves for 19 of the 21 valves. The trip killed the vehicle. This ends the 2007 effort.
This is a lesson in construction. WE need to pay more attention to transport with a "Real" suspension and we need a lot more plumbing support brackets etc...
Also what are we doing with 21 Valves?
On Each Quadrant: (4 each for 16)
Main Lox
Main Fuel
Lox Throttle
Fuel Throttle
On the Top (5)
Lox Safety pop off
Fuel Safety Pop off
Master Pressurization
Master Fuel Purge.
Igniter Dual Valve.
This is part of our problem. We could not get the ball valves to throttle/operate fast enough for our throttle and we could not get the fast butterflies to seal so we doubled the quadrant valves. If we had more time we would had fixed the big ball valves with shims and shaped orifices, removing one whole set of valves. We applied a quick fix and it failed.
Going forward/Don Quixote
We have 34 days till the practice session at the NG-LLC site. We have 41 days till the contest. I made a spread sheet with a list of the tasks necessary to compete. I made an optimistic and pessimistic time estimate. If I stopped going to work (I've been working 4 days a week) and worked full time for the next 41 days, the optimistic schedule says I have 7 Extra days before the practice session. The Pessimistic schedule says I'd be 4 days late for the contest.
My Day Job is CTO of Netburner, I'm one of the founders and the success of that company is the source of funding that makes Unreasonable Rocket possible. In the last year I've been putting most of my creative efforts toward this project and my business has suffered as a result. How much more do I commit? These are agonizing decisions. The Logical decision would be to suspend the effort for this year and restart if there is any prize money left after the contest.
Evaluating other teams for 2007/2008
I've been trying to keep track of the other teams and Judge the status of their efforts. There are 9 teams. Armadillo is as ready as anyone is ever going to get. Unreasonable Rocket is not going to make it in 2007. Two teams dropped out by not making the summit. That leaves five teams. Two teams have privately told me they won't make it. One team has asked if they can share test days with me at FAR,I Said yes, no problem. (If they are just starting serious rocket engine tests they won't make it) One more team privately told me they were giving up on the 180 second contest for this year. This leaves one team unknown for the 180 second flight. Only Armadillo has anything posted on the FAA website. I have to conclude that it will probably be the Armadillo show this year at XPC.
Even Armadillo has some issues, they crashed texel and have a supplier problem with their graphite chambers for long duration high pressure operation. (180 seconds). If I were a betting man I'd give 90% odds that there will still be 2nd place 500K available next year.
This has been the most difficult post to write, I know a lot of people have been following and rooting for the father and son team and I'm sorry to let you all down. Be assured that we will continue. We will probably take a month off to rest. Tonight I'm going to do something I have not done in a year. I'm going to sit a and watch the Chargers Patriots game. . I spent 10 years living near Boston, GO Pats, I've spent 15 years in the San Diego area, GO Bolts. So I don't know who to root for, but it should be a good game.
We took the complete vehicle out to FAR to do a four engine static test this weekend. We had a number of transport issues. We finally settled on a U haul trailer.
With the motors mounted the vehicle did not fit. So we unmounted the four motors. This left a fair bit dangling plumbing. Realize that this is a trailer with leaf springs and no shocks. The trailer is rated for 4500LBs we put 230 lbs in it. WE then drove for three hours to Mojave. We stopped early in the trip to check the tie downs and again at Mojave. By the time we reached the Arco station in Mojave we had either damaged the plumbing or shaken the hardware off of the valves for 19 of the 21 valves. The trip killed the vehicle. This ends the 2007 effort.
This is a lesson in construction. WE need to pay more attention to transport with a "Real" suspension and we need a lot more plumbing support brackets etc...
Also what are we doing with 21 Valves?
On Each Quadrant: (4 each for 16)
Main Lox
Main Fuel
Lox Throttle
Fuel Throttle
On the Top (5)
Lox Safety pop off
Fuel Safety Pop off
Master Pressurization
Master Fuel Purge.
Igniter Dual Valve.
This is part of our problem. We could not get the ball valves to throttle/operate fast enough for our throttle and we could not get the fast butterflies to seal so we doubled the quadrant valves. If we had more time we would had fixed the big ball valves with shims and shaped orifices, removing one whole set of valves. We applied a quick fix and it failed.
Going forward/Don Quixote
We have 34 days till the practice session at the NG-LLC site. We have 41 days till the contest. I made a spread sheet with a list of the tasks necessary to compete. I made an optimistic and pessimistic time estimate. If I stopped going to work (I've been working 4 days a week) and worked full time for the next 41 days, the optimistic schedule says I have 7 Extra days before the practice session. The Pessimistic schedule says I'd be 4 days late for the contest.
My Day Job is CTO of Netburner, I'm one of the founders and the success of that company is the source of funding that makes Unreasonable Rocket possible. In the last year I've been putting most of my creative efforts toward this project and my business has suffered as a result. How much more do I commit? These are agonizing decisions. The Logical decision would be to suspend the effort for this year and restart if there is any prize money left after the contest.
Evaluating other teams for 2007/2008
I've been trying to keep track of the other teams and Judge the status of their efforts. There are 9 teams. Armadillo is as ready as anyone is ever going to get. Unreasonable Rocket is not going to make it in 2007. Two teams dropped out by not making the summit. That leaves five teams. Two teams have privately told me they won't make it. One team has asked if they can share test days with me at FAR,I Said yes, no problem. (If they are just starting serious rocket engine tests they won't make it) One more team privately told me they were giving up on the 180 second contest for this year. This leaves one team unknown for the 180 second flight. Only Armadillo has anything posted on the FAA website. I have to conclude that it will probably be the Armadillo show this year at XPC.
Even Armadillo has some issues, they crashed texel and have a supplier problem with their graphite chambers for long duration high pressure operation. (180 seconds). If I were a betting man I'd give 90% odds that there will still be 2nd place 500K available next year.
This has been the most difficult post to write, I know a lot of people have been following and rooting for the father and son team and I'm sorry to let you all down. Be assured that we will continue. We will probably take a month off to rest. Tonight I'm going to do something I have not done in a year. I'm going to sit a and watch the Chargers Patriots game. . I spent 10 years living near Boston, GO Pats, I've spent 15 years in the San Diego area, GO Bolts. So I don't know who to root for, but it should be a good game.
Thursday, September 13, 2007
The New X prize.
I'm really disappointed in the new Google Lunar Xprize.
It would be a great prize 10 years from now, but today it just illustrates the core problem with space access. The high cost of access to low earth orbit.
The grand prize is 20M only twice what the original x-prize, yet the problem is at least 100 times as hard. I can't imagine what group or company would go after this prize.
Even if it is won, I fear it will not add much to reducing the cost of access.
It might be done as a stunt with a 500 gm Microrover.
I fear it will be a cool footnote, and will be a lot like Bigelows Americas space prize, The ratio of difficulty to winnings is just too high. (I personally think that Bigelows prize is of similar difficulty to the Google Lunar Xprize, and is twice the $$)
There are a number of firms working on high performance sub orbital aiming toward orbital launchers , Armadillo, Garvey Space, Micro-launchers, Masten etc...
If the intent of prizes is to encourage space exploration, A prize to encourage transport development would be so much more useful. I'd like to see a prize for a reusable orbital launcher, just something to launch 350 gram can sats.
It would be a great prize 10 years from now, but today it just illustrates the core problem with space access. The high cost of access to low earth orbit.
The grand prize is 20M only twice what the original x-prize, yet the problem is at least 100 times as hard. I can't imagine what group or company would go after this prize.
Even if it is won, I fear it will not add much to reducing the cost of access.
It might be done as a stunt with a 500 gm Microrover.
I fear it will be a cool footnote, and will be a lot like Bigelows Americas space prize, The ratio of difficulty to winnings is just too high. (I personally think that Bigelows prize is of similar difficulty to the Google Lunar Xprize, and is twice the $$)
There are a number of firms working on high performance sub orbital aiming toward orbital launchers , Armadillo, Garvey Space, Micro-launchers, Masten etc...
If the intent of prizes is to encourage space exploration, A prize to encourage transport development would be so much more useful. I'd like to see a prize for a reusable orbital launcher, just something to launch 350 gram can sats.
Wednesday, September 12, 2007
Win some loose some...
Tonight I finished the last little bit of wiring on the vehicle.
All the cable bundles had been run a few days ago, I just had a few misc connectors to solder on or wiring errors to fix.
We then went about systematically checking out quadrants.
Some where in the middle of doing this I tripped on the Ethernet cable going to the LapTop and the resultant experiment in inelastic collisions took out the LapTop screen.
Fortunately there is no shortage of computers in the Breed household.
All the cable bundles had been run a few days ago, I just had a few misc connectors to solder on or wiring errors to fix.
We then went about systematically checking out quadrants.
Some where in the middle of doing this I tripped on the Ethernet cable going to the LapTop and the resultant experiment in inelastic collisions took out the LapTop screen.
Fortunately there is no shortage of computers in the Breed household.
Tuesday, September 11, 2007
Really good news...
The vehicle is 100% hardware complete.
We weighed it and we are at least 10% under our target weight!!!!!!!
I'm not going to publish the weight until I can repeat the measurement, with a better calibrated scale,but this gives us significant performance margin for reaching 180 seconds!
More details:
The target weight with payload was 326 lbs.
The target empty weight was 271 lbs
The actual empty weight 230 Lbs.
My actual empty weight is 15% under Budget!!!
In order to do the 180 seconds I need a realized in flight ISP of ~152
As John Carmack rightly points out it won't be as high as I expect or wish.
The theoretical ISP for the pressures and fuel combination I'm using is 227
So I need to realize 66% of theoretical.
This is with tanks 90% full.
If I go to tanks 97% full I need an ISP of 145
We weighed it and we are at least 10% under our target weight!!!!!!!
I'm not going to publish the weight until I can repeat the measurement, with a better calibrated scale,but this gives us significant performance margin for reaching 180 seconds!
More details:
The target weight with payload was 326 lbs.
The target empty weight was 271 lbs
The actual empty weight 230 Lbs.
My actual empty weight is 15% under Budget!!!
In order to do the 180 seconds I need a realized in flight ISP of ~152
As John Carmack rightly points out it won't be as high as I expect or wish.
The theoretical ISP for the pressures and fuel combination I'm using is 227
So I need to realize 66% of theoretical.
This is with tanks 90% full.
If I go to tanks 97% full I need an ISP of 145
Friday, September 07, 2007
I'll sleep when I'm dead.
So much to do, there's plenty on the farm
I'll sleep when I'm dead
Saturday night I like to raise a little harm
I'll sleep when I'm dead
I'm drinking heartbreak motor oil and Bombay gin
I'll sleep when I'm dead
Straight from the rocket , twisted again
I'll sleep when I'm dead
Paraphrased from Warren Zevon.
Today I machined the last part.
If it all works the rocket hardware is done.
We have been trying to test it for the last three weeks.
We thought we had a chance to test two weeks ago Saturday.
We thought we would test with one motor last Saturday, alas when we flow tested the motor we were going to use, it was unusable, and may be why our last test failed. So I spent the last week building and carefully QA-ing 5 motors. I've taken detailed pictures of the whole process and after the XPC I'll post the drawings and detailed machining documentation.
So here it is three weeks after I first thought we might test the full up vehicle in a static fire, I've worked 18 and 20 hour days for three weeks and we have a shot at being ready for Saturday. I keep telling people we are testing next staurday,and I'm feeling like a flake. There are always a million details. Example Today my son and I are going over the new igniter plumbing and I realized that we had not put in the necessary check valves. So we are redoing that section of plumbing. (My son is currently driving back from the LA McMaster Carr will call with the check valves.) I'll post more later.
I'll sleep when I'm dead
Saturday night I like to raise a little harm
I'll sleep when I'm dead
I'm drinking heartbreak motor oil and Bombay gin
I'll sleep when I'm dead
Straight from the rocket , twisted again
I'll sleep when I'm dead
Paraphrased from Warren Zevon.
Today I machined the last part.
If it all works the rocket hardware is done.
We have been trying to test it for the last three weeks.
We thought we had a chance to test two weeks ago Saturday.
We thought we would test with one motor last Saturday, alas when we flow tested the motor we were going to use, it was unusable, and may be why our last test failed. So I spent the last week building and carefully QA-ing 5 motors. I've taken detailed pictures of the whole process and after the XPC I'll post the drawings and detailed machining documentation.
So here it is three weeks after I first thought we might test the full up vehicle in a static fire, I've worked 18 and 20 hour days for three weeks and we have a shot at being ready for Saturday. I keep telling people we are testing next staurday,and I'm feeling like a flake. There are always a million details. Example Today my son and I are going over the new igniter plumbing and I realized that we had not put in the necessary check valves. So we are redoing that section of plumbing. (My son is currently driving back from the LA McMaster Carr will call with the check valves.) I'll post more later.
Monday, September 03, 2007
Do you have a rocket problem?
If your garage sink has sprouted strange blue plumbing...
If you spend hours in the hot sun with a magnifying glass and a stop watch
staring at streams of water..
If you can quote the National fire protection standards for cryogenic fluids to the code enforcement officer, without notes.
If you know exactly what chemicals are used to denature ethanol, and can quote the stock numbers for the different types from the local chemical supplier.
If you collect strange copper sculptures.
If you know the density of several kinds of alcohol in both English and metric units.
If you have a sleepless night worring about how to rotate an Inertia Tensor
(And your friends solve the problem by return E-mail)
If you have a weekly conference call to a federal agency to explain how you problem is going...
If one of your buddies stops by to visit on the weekend and the first question he asks "are there any stainless chips in the chips on the floor" He's barefoot and his feet are just fine with aluminum chips, but they are not yet tough enough for stainless.
If you are proud of your AN fittings collection.
If you know the hours of and directions to the McMaster Carr will call window.
If you this looks like you, you have arocket problem, seek help.
If you spend hours in the hot sun with a magnifying glass and a stop watch
staring at streams of water..
If you can quote the National fire protection standards for cryogenic fluids to the code enforcement officer, without notes.
If you know exactly what chemicals are used to denature ethanol, and can quote the stock numbers for the different types from the local chemical supplier.
If you collect strange copper sculptures.
If you know the density of several kinds of alcohol in both English and metric units.
If you have a sleepless night worring about how to rotate an Inertia Tensor
(And your friends solve the problem by return E-mail)
If you have a weekly conference call to a federal agency to explain how you problem is going...
If one of your buddies stops by to visit on the weekend and the first question he asks "are there any stainless chips in the chips on the floor" He's barefoot and his feet are just fine with aluminum chips, but they are not yet tough enough for stainless.
If you are proud of your AN fittings collection.
If you know the hours of and directions to the McMaster Carr will call window.
If you this looks like you, you have arocket problem, seek help.
Friday, August 24, 2007
Vehicle progress.
The vehicle is coming along nicely. We were planning to test this weekend and we could probably be ready with p=.8, but things would be rushed and unchecked. We will test next weekend and we will be really ready. Current progress:
Propane igniter:
We did some testing with using a normal camp stove propane cylinder as the fuel source for the igniter, and it looks like the tank orifice is too small and it won't feed 4 motors. We will be switching to a paint ball tank for the propane source tank.
Paperwork:
I've been working on the hardware and have neglected the FAA paperwork side. They are going to put my 120 day clock on hold until I finish up some details I owe them.
- The top side pressurization, regulator and blow off vent valves are all done.
- The igniter plumbing is all done.
- 3 of the four motors are plumbed.
- The structural framing is all complete.
- The first cut of the landing gear is done and 3 of 4 are on the vehicle.
- (Were going to change the Landing gear slightly so we don't melt it.)
- The new control board electronics have finished initial testing and seem to work.
Propane igniter:
We did some testing with using a normal camp stove propane cylinder as the fuel source for the igniter, and it looks like the tank orifice is too small and it won't feed 4 motors. We will be switching to a paint ball tank for the propane source tank.
Paperwork:
I've been working on the hardware and have neglected the FAA paperwork side. They are going to put my 120 day clock on hold until I finish up some details I owe them.
Saturday, August 18, 2007
Getting the vehicle ready.
While I probably don't mention them enough there are a number of people that are helping this project significantly.
For the past six months I've been working on this project three days a week, Friday, Saturday and Sunday all day, as well as evenings the rest of this week.
This week we are trying to get the whole vehicle ready for a single engine test firing next weekend. To have any chance of doing this I'm taking a week and half off of work and doing nothing but unreasonable Rocket.
Fridays Progress:
I worked on the ground equipment case that holds the data recorder, telemetry radios, video receivers etc.... (This is now Jasons project)
I fabricated and tested a small dual 1/8" ball valve actuator to replace our unreliable igniter solenoids.
I finished the servo mountings on the safety vent valves.
My Son Plumbed the pressurization system and with Carl's help at Flowmetrics got the regulator working.
My son continued to plumb the vehicle.
I put together another "hardware tour" video of the vent and igniter valves.
Today we are going to combine a trip to the Los Angles McMaster Carr will call with a trip to see my Father who is recovering from Knee replacement surgery in Long Beach..
- Charles Pooley has been an invaluable resource to discuss rocket ideas and to bounce ideas off of.
- The guys at flowmetrics have their shop about 1/2 mile from my house. They have been very helpful with knowledge, know how and ideas.
- My sons friend Jason. Jason is home from college for the summer and spends considerable time in our garage helping with the electronics, software and the much appreciated shop entropy control.
- Mark, Kevin and Ted at Friends of amateur rocketry.
- Bob Nortman has been doing all of our aluminum welding.
For the past six months I've been working on this project three days a week, Friday, Saturday and Sunday all day, as well as evenings the rest of this week.
This week we are trying to get the whole vehicle ready for a single engine test firing next weekend. To have any chance of doing this I'm taking a week and half off of work and doing nothing but unreasonable Rocket.
Fridays Progress:
I worked on the ground equipment case that holds the data recorder, telemetry radios, video receivers etc.... (This is now Jasons project)
I fabricated and tested a small dual 1/8" ball valve actuator to replace our unreliable igniter solenoids.
I finished the servo mountings on the safety vent valves.
My Son Plumbed the pressurization system and with Carl's help at Flowmetrics got the regulator working.
My son continued to plumb the vehicle.
I put together another "hardware tour" video of the vent and igniter valves.
Today we are going to combine a trip to the Los Angles McMaster Carr will call with a trip to see my Father who is recovering from Knee replacement surgery in Long Beach..
Monday, August 13, 2007
Disapointing weekend.
We spent a long 16 hour day out at the test site and never got the igniter to light. We had some kind of sludge form in the ethanol tanks and it kept clogging the igniter solenoid and filter. It was a very discouraging day.
We test again in two weeks. We have a long list of things to try.
1)Change to isopropyl alcohol for less residue.
2)change to propane for the igniter fuel.
3)Possibly change to a pyro igniter based on a small solid rocket motor.
(This is a major logistics hassle, but simplifies and lightens the vehicle.)
If we do not get reliable ignition and throttling working by the end of that weekend, we are realistically done for this year.
The one bright spot was that we were sharing the test facilities with Garvey space and they had a successful test. Seeing a 5K motor running is a beautiful thing. I have some awesome video, and I will post it as soon as I get permission from Garvey.
We test again in two weeks. We have a long list of things to try.
1)Change to isopropyl alcohol for less residue.
2)change to propane for the igniter fuel.
3)Possibly change to a pyro igniter based on a small solid rocket motor.
(This is a major logistics hassle, but simplifies and lightens the vehicle.)
If we do not get reliable ignition and throttling working by the end of that weekend, we are realistically done for this year.
The one bright spot was that we were sharing the test facilities with Garvey space and they had a successful test. Seeing a 5K motor running is a beautiful thing. I have some awesome video, and I will post it as soon as I get permission from Garvey.
Thursday, August 09, 2007
72 Days left...
There are 72 days until the contest.
Its going to be really busy!
I went to the team summit last week and it looks like we did not scare the Airforce too bad ;-).
The Local paper put us on the front page. (Web version)
I'm testing again this weekend, I realize that I've been lax in updating the blog, but hardware comes first. I just finished making my first set of safety relief valves, they hold to 1100 PSI
and open instantaneously, when I deliberately added a bit of air before pumping up the hydro tester it sounds like a gun shot when it opens. As I have to prepare pictures and test docs for these valves for the FAA I'll post them here as well.
Its going to be really busy!
I went to the team summit last week and it looks like we did not scare the Airforce too bad ;-).
The Local paper put us on the front page. (Web version)
I'm testing again this weekend, I realize that I've been lax in updating the blog, but hardware comes first. I just finished making my first set of safety relief valves, they hold to 1100 PSI
and open instantaneously, when I deliberately added a bit of air before pumping up the hydro tester it sounds like a gun shot when it opens. As I have to prepare pictures and test docs for these valves for the FAA I'll post them here as well.
Thursday, July 26, 2007
Sad day in rocket land.
Rockets are energetic devices. They are dangerous. No one working on them should ever forget that. Nor should we shy from the task at hand. Very often in human history progress has been paid for in blood. So it has been and so it always will be.
Our heartfelt condolences go out to the entire scaled family.
Our heartfelt condolences go out to the entire scaled family.
Monday, July 23, 2007
Its all about the systems...
Its all about the systems integration.
I'm trying to diagnose the Helicopter systems to work on flight software. I have a GPS on the roof of my house and one mounted on the back of the helicopter, when working on the system I unplug the one on the helicopter and plug in the one on the roof We get ZERO gps reception inside. The one on the roof works really well.
So I take the helicopter out to fly it and after waiting a long time get no GPS lock at all. So I bring it back to the house and replace the GPS receiver with another one. (assuming the old GPS receiver got broken in the last heli cras h.) ,butI'm getting smarter I don't drive all the way to the flying field to test the new receiver. I go out in the back yard still no GPS.
So now I take a 6 foot cable and the "broken" gps and plug it into the helicopter it works from 6 feet away! So I then set the broken GPS on top of the gps on the helicopter and it still works! Then I remove the 6 foot cable and it does not work.
So then I plug in the 6 foot cable between the electronics and the GPS currently mouted on the helicopter. It works.....
So I now have 2 GPS receivers that have decided that they need 6 feet of cable to operate. 1 foot is not enough.
First working hypothesis: the 900Mhz telemetry radio is putting EMI on the wiring. The long cable is enough to filter it out, the short cable is not.
Experimental test don't transmit until you get GPS lock.
Still no GPS, add 6foot cable to verify the don't transmit till you get lock code works, the code works.
Second working hypothsis:
Some other component of the system (likely the CPU) is putting enough noise on the wire to kill the GPS, Next step put noise filter on all the cables and try again.
Well let you know......
I'm trying to diagnose the Helicopter systems to work on flight software. I have a GPS on the roof of my house and one mounted on the back of the helicopter, when working on the system I unplug the one on the helicopter and plug in the one on the roof We get ZERO gps reception inside. The one on the roof works really well.
So I take the helicopter out to fly it and after waiting a long time get no GPS lock at all. So I bring it back to the house and replace the GPS receiver with another one. (assuming the old GPS receiver got broken in the last heli cras h.) ,butI'm getting smarter I don't drive all the way to the flying field to test the new receiver. I go out in the back yard still no GPS.
So now I take a 6 foot cable and the "broken" gps and plug it into the helicopter it works from 6 feet away! So I then set the broken GPS on top of the gps on the helicopter and it still works! Then I remove the 6 foot cable and it does not work.
So then I plug in the 6 foot cable between the electronics and the GPS currently mouted on the helicopter. It works.....
So I now have 2 GPS receivers that have decided that they need 6 feet of cable to operate. 1 foot is not enough.
First working hypothesis: the 900Mhz telemetry radio is putting EMI on the wiring. The long cable is enough to filter it out, the short cable is not.
Experimental test don't transmit until you get GPS lock.
Still no GPS, add 6foot cable to verify the don't transmit till you get lock code works, the code works.
Second working hypothsis:
Some other component of the system (likely the CPU) is putting enough noise on the wire to kill the GPS, Next step put noise filter on all the cables and try again.
Well let you know......
Sunday, July 22, 2007
Software Hardware Hardware Hardware Paperwork
Software
Our current plans for developing the stability and control aspect of this are as follows:
1)Make the system fly on a Trex 600 RC helicopter.
2)Move all but the lowest level rate command servo loops from the helicopter to the rocket.
Toward that end we have been using a nice RC heli sim from source forge to simulate the helicopter systems in software. We have modified the sim to only update the data at the same rate as our IMU and GPS. The windows version of the simulator does not have any kind of control or autopilot, just a comment in the code that says put your control laws here.... Using that I've tuned the insane number of PID loops and adjusted it so it will fly a whole XPC LLC flight from start to finish. (You can run my compiled version of the code here) Again this is an exe that is compiled for my use etc etc .
Hardware Hardware Hardware
I took the video camera and wandered around the house and shop and
took video of: (Video is here (Fixed) )
Not awesome video and if you have not been following the blog it probably won't make sense, but my guess is that people like to see hardware from time to time.
Paperwork
No show stoppers in paperwork land. This last week I had to provide XPC a Mishap response plan. I think such plans should be really simple so that you can actually do them in time of crisis. The document is here.
Our current plans for developing the stability and control aspect of this are as follows:
1)Make the system fly on a Trex 600 RC helicopter.
2)Move all but the lowest level rate command servo loops from the helicopter to the rocket.
Toward that end we have been using a nice RC heli sim from source forge to simulate the helicopter systems in software. We have modified the sim to only update the data at the same rate as our IMU and GPS. The windows version of the simulator does not have any kind of control or autopilot, just a comment in the code that says put your control laws here.... Using that I've tuned the insane number of PID loops and adjusted it so it will fly a whole XPC LLC flight from start to finish. (You can run my compiled version of the code here) Again this is an exe that is compiled for my use etc etc .
Hardware Hardware Hardware
I took the video camera and wandered around the house and shop and
took video of: (Video is here (Fixed) )
- The helicopter with GPS, IMU and computer mounted on it.
- The test stand we have been running.
- The first vehicle airframe.
Not awesome video and if you have not been following the blog it probably won't make sense, but my guess is that people like to see hardware from time to time.
Paperwork
No show stoppers in paperwork land. This last week I had to provide XPC a Mishap response plan. I think such plans should be really simple so that you can actually do them in time of crisis. The document is here.
Sunday, July 15, 2007
Weekend Testing results...
This weekends motor tesoting started out with a lot of little issues.Not the least of which was sleep deprivation. We finally got them straightened out in the early afternoon and had two successful tests. The second test was operationally perfect. For some reason we did not get chamber pressure, but the light was perfect and the motor ran really well until we ran out of helium pressurizing gas at about 95 seconds of run time. (The previous minor problems used a lot of helium). the two key events were:
1)The motor started correctly. This was the result of using a lox lead and pre-flowing the igniter for a few seconds.
2)We did a number of throttle step tests with the new fast butterfly valves. From the gathered data we were only really throttling the fuel side, but the response time and the fact that the motor ran down to 75 PSI input pressure was really good news.
I was manually operating the valves in an open loop manner and the response from giving the step up/down command to seeing the mach diamonds change was instantaneous to my perception. Lastly we had a teperature probe in the fuel feed and we are ok for heat load. At full throttle my guess is we are getting some boiling, but not extreme boiling. The video camera shutdown about 15 sseconds into both tests. I'm beginning to wonder if the there is some sort of IR oscillation in the motor that is commanding the camera off. The first 15 seconds with the first throttle step at the the end of the video is here I'll put tape over the IR remote port next time. The gathered data is below:
1)The motor started correctly. This was the result of using a lox lead and pre-flowing the igniter for a few seconds.
2)We did a number of throttle step tests with the new fast butterfly valves. From the gathered data we were only really throttling the fuel side, but the response time and the fact that the motor ran down to 75 PSI input pressure was really good news.
I was manually operating the valves in an open loop manner and the response from giving the step up/down command to seeing the mach diamonds change was instantaneous to my perception. Lastly we had a teperature probe in the fuel feed and we are ok for heat load. At full throttle my guess is we are getting some boiling, but not extreme boiling. The video camera shutdown about 15 sseconds into both tests. I'm beginning to wonder if the there is some sort of IR oscillation in the motor that is commanding the camera off. The first 15 seconds with the first throttle step at the the end of the video is here I'll put tape over the IR remote port next time. The gathered data is below:
Wednesday, July 11, 2007
This weeks plans.
We are planning to do a test fire again this Saturday. We have made a number of changes. We have added very very fast butterfly valves just after the main (slow) ball valves. We hope this will have a bit more linear throttle action and be somewhat faster. Toward that end we have set up a flow test with an exact engine string, pressure transducer, ball valve, butterfly valve , pressure transducer,turbine flow meter , long tube and pintile orifice. We have started mapping how linear the valve is and it's flow response. This will all be on the test stand before Friday.
In addition I found some very small isolated thermocouples and we will instrument the fuel temperature rise for this event. So this weeks fireeing should generate some good data. I always planned to have the thermocouple, but the non-isolated version had some ground loop problems that totally swamped the signal I was trying to measure.
On the stability and control front I upgraded my helicopter from a Trex 450 to a Trex 600, it no longer wallows with the IMU, GPS and computer attached. We will report more on this effort next week.
In addition I found some very small isolated thermocouples and we will instrument the fuel temperature rise for this event. So this weeks fireeing should generate some good data. I always planned to have the thermocouple, but the non-isolated version had some ground loop problems that totally swamped the signal I was trying to measure.
On the stability and control front I upgraded my helicopter from a Trex 450 to a Trex 600, it no longer wallows with the IMU, GPS and computer attached. We will report more on this effort next week.
Thursday, July 05, 2007
A Quick update...
Due to some scheduling issues we will not be testing this comming weekend, but we will be testing the weekend of the 14th.
Since the airlander flight testing did not go so well I thought I'd sneak up on the problem. I took my IMU, CPU, Telemetry radio and GPS and weighed it. I then took that much lead and put it on my Trex 450 RC helicopter. It's a small helicopter as RC helicopters go and I wanted to see if it could carry that much weight. So with 290 grams of lead it flew just fine, hovered for close to 5 minutes.
Step 2 Actually mount all that stuff to the helicopter and see if all works.
So I mounted the GPS, IMU, Telemetry Radio to the Helicopter. I then took the outputs from the RC receiver to the CPU board and then ran the helicopter servos from the CPU. The CPU is in the loop, but not yet doing anything but passing the commands directly from the RC receiver. I added an additional input from the RC receiver that I call mode that will allow me to switch from manual contol to automated control as time goes on. The GPS, RC receiver and telemetry radio all seem to coexist with no detectable interference.
I also did a fair bit of work on my telemetry display framework. My windows coding is a bit rusty so that has been an interesting challenge. So I flew it in my driveway, everything worked perfectly but my thumbs. I've been flying the copter in my driveway for awhile, but my wife added a new shrub........In any case I need to get new blades at the hobby store as I cliped the edge of the shrub and this pulled the helicopter into the shrub. None of the electronics or expensive bits seems to be damaged, just the typical helicopter crash parts, blades, flybar etc...
I'll get the replacement parts on Friday and go to a large open field and start doing some serious testing this week end.
I recorded the telemetry during this whole flight.
You can take a look at it I've uploaded the telemetry data file and the executable to view it.
The executable is the same one that shows telemetry in real time so on startup you need to select the "replay log" button. Then load flight2.dat. The log file has a bit of dull data as I go from starting the recording to connecting the RC power battery and moving the helicopter into position. Liftoff is around frame 8000. You probably want to click the 10X button until data starts changing. The 5 combo boxes on top left control what data is displayed.
The screen shot on the left is centered at the moment of shrub acquisition.
The derived Roll, Pitch and Yaw seem really reasonable, the rates and accelerations seem really noisy. Enjoy following along.
As always its probably not a good idea to download and run an executable from someone you don't know without virus scanning it etc... This exe was done for me on my computers so if there is a missing DLL, it crashes etc... no guarantee....
Since the airlander flight testing did not go so well I thought I'd sneak up on the problem. I took my IMU, CPU, Telemetry radio and GPS and weighed it. I then took that much lead and put it on my Trex 450 RC helicopter. It's a small helicopter as RC helicopters go and I wanted to see if it could carry that much weight. So with 290 grams of lead it flew just fine, hovered for close to 5 minutes.
Step 2 Actually mount all that stuff to the helicopter and see if all works.
So I mounted the GPS, IMU, Telemetry Radio to the Helicopter. I then took the outputs from the RC receiver to the CPU board and then ran the helicopter servos from the CPU. The CPU is in the loop, but not yet doing anything but passing the commands directly from the RC receiver. I added an additional input from the RC receiver that I call mode that will allow me to switch from manual contol to automated control as time goes on. The GPS, RC receiver and telemetry radio all seem to coexist with no detectable interference.
I also did a fair bit of work on my telemetry display framework. My windows coding is a bit rusty so that has been an interesting challenge. So I flew it in my driveway, everything worked perfectly but my thumbs. I've been flying the copter in my driveway for awhile, but my wife added a new shrub........In any case I need to get new blades at the hobby store as I cliped the edge of the shrub and this pulled the helicopter into the shrub. None of the electronics or expensive bits seems to be damaged, just the typical helicopter crash parts, blades, flybar etc...
I'll get the replacement parts on Friday and go to a large open field and start doing some serious testing this week end.
I recorded the telemetry during this whole flight.
You can take a look at it I've uploaded the telemetry data file and the executable to view it.
The executable is the same one that shows telemetry in real time so on startup you need to select the "replay log" button. Then load flight2.dat. The log file has a bit of dull data as I go from starting the recording to connecting the RC power battery and moving the helicopter into position. Liftoff is around frame 8000. You probably want to click the 10X button until data starts changing. The 5 combo boxes on top left control what data is displayed.
The screen shot on the left is centered at the moment of shrub acquisition.
The derived Roll, Pitch and Yaw seem really reasonable, the rates and accelerations seem really noisy. Enjoy following along.
As always its probably not a good idea to download and run an executable from someone you don't know without virus scanning it etc... This exe was done for me on my computers so if there is a missing DLL, it crashes etc... no guarantee....
Tuesday, June 26, 2007
Out of Town this week.
I went testing last weekend and have some more video. The testing raised more questions than it answered. I'll be back in town Friday and try to post some of the video and more commentary. I'm away at the freescale technology forum in Orlando. The cool non-rocket news is that the new Netburner product I designed, the Product Kit won the best in show award!
One question for the rocket geeks... I'm still having troubles getting the engine reliably lit. Is there any harm to a really long (A second or more) LOX lead?
One question for the rocket geeks... I'm still having troubles getting the engine reliably lit. Is there any harm to a really long (A second or more) LOX lead?
Thursday, June 21, 2007
FAA paperwork milestone.
I just got off the phone with the FAA/AST and they have determined that my application is complete enough to begin the evaluation. (This used to be called sufficiently complete) This is the official milestone that starts the 120 day clock. Since the Application they deemed complete enough was received by the FAA on May 29th They are now legislatively bound to approve or disapprove the application by September 26th. They can still ask for a lot of information and request changes in the vehicle or safety systems, but at least the clock is started.
Here is the offical PDF (with addresses and phone numbers removed)
Here is the offical PDF (with addresses and phone numbers removed)
Sunday, June 10, 2007
Wednesday, June 06, 2007
More chamber failure testing...
We went out to the test site last Sunday to test the normal soldered
chamber. It failed by buldging in, but no where near as bad as the earlier failures. It bulged in exactly inline with the igniter outlet. So maybe the torch igniter is softening the chamber wall. We are goign to try a number of fixes for this this again this weekend. Three expeditions to Mojave in three weeks is a bit hard on the sleep schedule.
chamber. It failed by buldging in, but no where near as bad as the earlier failures. It bulged in exactly inline with the igniter outlet. So maybe the torch igniter is softening the chamber wall. We are goign to try a number of fixes for this this again this weekend. Three expeditions to Mojave in three weeks is a bit hard on the sleep schedule.
Thursday, May 31, 2007
Chamber failures explained.
Tonight I made a chamber liner by silver soldering it at high temperature.
In my pressure test fixture it failed between 380 and 400 PSI.
So this explains my motor failures, but does not really give me a huge amount of comfort. It means I can never get the liner hot enough to anneal it and I am Dependant on the annealed condition of commercial water pipe for my strength.
We are going to test fire again the weekend.
In my pressure test fixture it failed between 380 and 400 PSI.
So this explains my motor failures, but does not really give me a huge amount of comfort. It means I can never get the liner hot enough to anneal it and I am Dependant on the annealed condition of commercial water pipe for my strength.
We are going to test fire again the weekend.
Wednesday, May 30, 2007
Simulating Chamber failure at home.
Any time I can run an experiment at home that replicates things I see at the test site it's a huge win. Tonight I fabricated a plugged injector plate and soldered up a chamber inner liner and throat. I used the plugged injector plate to Hydro test the chamber to failure. The chamber liner failed at 1750 PSI. It failed in exactly the same way as the chambers that failed in the field did. This liner and throat were soldered with normal relatively low temp solder.
Thursday I will solder up a throat with high temp silver solder and test that to failure.
As part of doing this test I also abused my o-ring seals, no lubricant and hammered them together. I even got o-ring slivers sliced off the injector end o-ring. Still the o-rings held and did not leak at 1750 PSI.The Snap ring retainers and the fuel feed plumbing also held the pressure. All in all a good test.
For one last reality check Plain old un alloyed copper has a work hardened to fully annealed yield strength ratio of ~5. So 1750/5 = 350PSI we were running the fuel feed at around 375.
At some level it all makes sense.
Thursday I will solder up a throat with high temp silver solder and test that to failure.
As part of doing this test I also abused my o-ring seals, no lubricant and hammered them together. I even got o-ring slivers sliced off the injector end o-ring. Still the o-rings held and did not leak at 1750 PSI.The Snap ring retainers and the fuel feed plumbing also held the pressure. All in all a good test.
For one last reality check Plain old un alloyed copper has a work hardened to fully annealed yield strength ratio of ~5. So 1750/5 = 350PSI we were running the fuel feed at around 375.
At some level it all makes sense.
Monday, May 28, 2007
Chamber Failures
This weekend we had two chambers fail identically. We set out to verify we had solved our ignition problems. So for our first test we ran a few seconds , purged a few seconds and ran again. Both ignitions were perfect. On the second start we saw a big green copper flash. We thought this chamber failure was due to too short of purge. But in reviewing the video I see we got a green flash on shutdown. We ran a second motor and it failed on startup.
Thoughts on the failures:
The first chambers we built we used high temp silicon to seal to the carbon throat and had the spiral wires soldered on with normal solder. The chamber to aluminum jacket tolerance was so tight we had to assemble the motors with a sledge hammer.
The motor we ran for 106 seconds had the copper throat soldered into the chamber wall with normal solder and spiral wires soldered on with normal solder. This motor was tight, but only needed light taps, not the full sledge treatment.
When we disassembled that motor we discovered that some of the spiral wires were loose, we did no know if that was an issues with getting hot of breaking the wires loose on assembly / disassembly.
As a result we decided that we should silver solder the parts together. So the last two motors we built with silver solder. This requires that we get the copper liner much hotter and probably removes the temper. As we have been using copper water pipe the temper is a side effect of the forming process and is not guaranteed to be in any particular state of hardness.
My current set of hypothesis is as follows:
- We are softening the chamber walls when we silver solder the parts together.
- The Hotrod igniter is making a soft spot on the chamber side leading to local buckling.
- We got a different batch of water pipe and is is less tempered.
- Switch back to normal solder for the throat and spiral wires.
- Rerun our flow rate tests we ran on the first chamber to verify we have not drifted off of nominal.
- Do a hydrostatic collapse test on the pipe we have to see if the batches are different.
- Build up 4 chambers for testing, hopefully, next weekend.
- One of these chambers will use thicker pipe wall.
My verification tests are as follows:
- Run a test where we run the igniter and then hit the chamber with full fuel pressure, but no lox if this collapses then we have the igniter too hot or oriented wrong.
- Rerun the tests we tried this weekend.
- If both of these fail retest with the thick wall chamber.
Sunday, May 27, 2007
Murphy Wins!
We went testing this weekend....
The game was not even close, Murphy won.
Video Summary here
1)Saturday Afternoon Very little lox, almost none.
Masten Space was nice enough to sell us some of theirs.
Thank you thank you thank you!
2)Saturday late ran the test chamber twice
Melted the test chamber in a new way. Video and pictures Monday.
3)Late Saturday set up telescope.
One axis is broken and drive motor makes grinding noises.
Used it in manual mode looked at moon and Jupiter, very cool viewing.
4)Sunday Morning test stability and control air lander...
No stability no control we now have pieces...video later
5)Sunday noon time...Tested 2nd chamber failed immediately with the center copper chamber wall buckling and collapsing inward. Same failure as #2 above.
6)Sunday just after noon help SDSU students with telemetry for their rocket.
SDSU has spectacular hard start and fireball. (video Monday)
7)Early Saturday Successfully flew my RC helicopter.
Saturday Afternoon flew it again, tail rotor belt failed.
Failed in low hover, no other damage.
8)Sunday about 3:30 got flat tire.
Spare was flat. The road to the test site is rock and dirt, very hard on tires.
(Had a 12 V compressor with me, dodged Murphy a bit)
Murphy 8 unreasonable rocketeers ZERO.
No one was physically injured, when I got home the house had not been leveled by a stray meteor, its all part of the process.
The game was not even close, Murphy won.
Video Summary here
1)Saturday Afternoon Very little lox, almost none.
Masten Space was nice enough to sell us some of theirs.
Thank you thank you thank you!
2)Saturday late ran the test chamber twice
Melted the test chamber in a new way. Video and pictures Monday.
3)Late Saturday set up telescope.
One axis is broken and drive motor makes grinding noises.
Used it in manual mode looked at moon and Jupiter, very cool viewing.
4)Sunday Morning test stability and control air lander...
No stability no control we now have pieces...video later
5)Sunday noon time...Tested 2nd chamber failed immediately with the center copper chamber wall buckling and collapsing inward. Same failure as #2 above.
6)Sunday just after noon help SDSU students with telemetry for their rocket.
SDSU has spectacular hard start and fireball. (video Monday)
7)Early Saturday Successfully flew my RC helicopter.
Saturday Afternoon flew it again, tail rotor belt failed.
Failed in low hover, no other damage.
8)Sunday about 3:30 got flat tire.
Spare was flat. The road to the test site is rock and dirt, very hard on tires.
(Had a 12 V compressor with me, dodged Murphy a bit)
Murphy 8 unreasonable rocketeers ZERO.
No one was physically injured, when I got home the house had not been leveled by a stray meteor, its all part of the process.
Friday, May 25, 2007
I've received the first Tee Shirts
I've just received the first Unreasonable Rocket Tee's and they look good.
So feel free to order some at the Store.
So feel free to order some at the Store.
Learning Curve/Frustration...
I brazed my last injector myself, but it got really oxidized.
I was worried about the black oxide flakes plugging up the injector.
So I thought I would step up to the plate and have the next one furnace brazed.
So I did about 30 hours of machining making all the parts and took it to a company that specializes in furnace brazing. As I did it all myself I had the peice part drawings, but did not have an assembly drawing. The parts only fit together one way.
So I carefully showed them how it all goes together with the warning that it was very important that the gap between the pintile and the injector face not be brazed....
Unfortunately the person doing the work was not the person I presented the parts to. The person I presented the parts to came from the shop end of the building so I figured he would be doing the work.
I got it back today and the gap between the pintile and injector plate is brazed shut. $200.00 of telerium copper and more importantly 30 hours of work are scrap. Argggh!
Key learning point.... If the shop is used to detailed assembly drawings provide them one. Even if it is self explanatory to you it may not be so to them.
I was worried about the black oxide flakes plugging up the injector.
So I thought I would step up to the plate and have the next one furnace brazed.
So I did about 30 hours of machining making all the parts and took it to a company that specializes in furnace brazing. As I did it all myself I had the peice part drawings, but did not have an assembly drawing. The parts only fit together one way.
So I carefully showed them how it all goes together with the warning that it was very important that the gap between the pintile and the injector face not be brazed....
Unfortunately the person doing the work was not the person I presented the parts to. The person I presented the parts to came from the shop end of the building so I figured he would be doing the work.
I got it back today and the gap between the pintile and injector plate is brazed shut. $200.00 of telerium copper and more importantly 30 hours of work are scrap. Argggh!
Key learning point.... If the shop is used to detailed assembly drawings provide them one. Even if it is self explanatory to you it may not be so to them.
FAA Permit Application
I've just finished printing the two copies of my experimental permit application. I'm on my way out the door to send them.
As I've stated previously I would make anything I formally submit available.
Here is the Application and the Cover Letters.
I'm a tiny bit queasy making all of this public, but one of my main goals is to try to demystify the process of doing rocketry as much as possible. The regulatory aspects are a key part of that process.
As I've stated previously I would make anything I formally submit available.
Here is the Application and the Cover Letters.
I'm a tiny bit queasy making all of this public, but one of my main goals is to try to demystify the process of doing rocketry as much as possible. The regulatory aspects are a key part of that process.
Wednesday, May 23, 2007
AST News.
I got a chance to chat with my AST representative today and I'm pleased with the discussion. He indicated that I should probably formally submit my next revision and not just send them a draft for review. While not a formal endorsement, it at least implies that I'm close to "complete enough". I hope to finish up and Mail the Fed-X the formal application on Monday or Tuesday.
In a past life I was responsible for negotiating the technical engineering aspects of a significant subcontract. whenever we found ambiguity in the contract it was good news because we could exploit this to get more money from the prime. As a result I have a fine tuned "ambigious nit sensor". I have to fight this impulse to pick these nits when working with the FAA.
A simple example:
One of the comments I received on my draft application was :
AST understands that there are no hazardous materials asociated with the vehicle.
However for the purposes of documentation completeness, the application still needs to state positively that there are no hazardous materials used in the suborbital rocket.
Seems like a simple statement and they are really looking for a statement that I'm not using hydrazine or some other really nasty substance. This seems really simple,but my "ambigious nit sensor" goes off and I start wondering ....
Is Lead solder Hazardous?
Is the Lead in Brass Hazardous?
Is the gallium arsenide in the GASFET RF amplifiers hazardous?
So I write the following:
In a past life I was responsible for negotiating the technical engineering aspects of a significant subcontract. whenever we found ambiguity in the contract it was good news because we could exploit this to get more money from the prime. As a result I have a fine tuned "ambigious nit sensor". I have to fight this impulse to pick these nits when working with the FAA.
A simple example:
One of the comments I received on my draft application was :
AST understands that there are no hazardous materials asociated with the vehicle.
However for the purposes of documentation completeness, the application still needs to state positively that there are no hazardous materials used in the suborbital rocket.
Seems like a simple statement and they are really looking for a statement that I'm not using hydrazine or some other really nasty substance. This seems really simple,but my "ambigious nit sensor" goes off and I start wondering ....
Is Lead solder Hazardous?
Is the Lead in Brass Hazardous?
Is the gallium arsenide in the GASFET RF amplifiers hazardous?
So I write the following:
Unreasonable rocket will not be using any environmentally hazardous substance, we are only using benign non-toxic propellants . The non- consumable portions of the vehicle will be constructed with aluminum,copper, stainless steel and normal composite structures. The only components of vehicle that might contain nominally hazardous materials are the trace elements in the electronic components and lead containing solders that are part of these assemblies. The commercial components will all be RHOS compliant lead free, but the non commercial components assembled for this effort will use lead solder for reliability purposes.
What I finally put in the application is:
Unreasonable rocket is not using any hazardous consumables.
What I finally put in the application is:
Unreasonable rocket is not using any hazardous consumables.
Tuesday, May 22, 2007
Fabricating our first vehicle....
Our test stand used flight weight tanks and valves.
Our first vehicle is going to look a lot like four of these test stands.
Toward that end my son and I have been fabricating and buying parts, we hydroformed and machined 17 tank ends (1 spare ),
We had Thunderbird Water jet cut some valve parts and brackets.
We ordered and received a batch of tonegawa servos from Tokyo hobbies.
Tube services sold us some aluminum tubing to make tanks.
We ordered all the tank weld on AN fittings from Iindustrial liquidators They are a dealer for Earls Fittings.
Lots of Valves, snap rings and parts from McMaster Carr.
I have enough Tellirium Copper to build 20 or so Motors purchased from Cambrdige Lee.
3 Vehicles of solinoids from Predyne.
1.25 Vehicles of ignition modules from CH-Ignitions.
2 Vehicles worth of Composite helium tanks on Order from SCI.
O-rings from Real Seal.
On Friday I pick up a furnace brazed Injector assembly from Certified Metal Craft.
Flowers for my understanding wife from ProFlowers.com....
(Delivered some time Wednesday Morning. Shes' usually home in the mornings, so I've asked her if she can be home Wednesday Morning to receive a very important package for my project, she just doesn't know its flowers for her...yet....)
I'm sure I've left off and forgotten a million vendors.
Our first vehicle is going to look a lot like four of these test stands.
Toward that end my son and I have been fabricating and buying parts, we hydroformed and machined 17 tank ends (1 spare ),
We had Thunderbird Water jet cut some valve parts and brackets.
We ordered and received a batch of tonegawa servos from Tokyo hobbies.
Tube services sold us some aluminum tubing to make tanks.
We ordered all the tank weld on AN fittings from Iindustrial liquidators They are a dealer for Earls Fittings.
Lots of Valves, snap rings and parts from McMaster Carr.
I have enough Tellirium Copper to build 20 or so Motors purchased from Cambrdige Lee.
3 Vehicles of solinoids from Predyne.
1.25 Vehicles of ignition modules from CH-Ignitions.
2 Vehicles worth of Composite helium tanks on Order from SCI.
O-rings from Real Seal.
On Friday I pick up a furnace brazed Injector assembly from Certified Metal Craft.
Flowers for my understanding wife from ProFlowers.com....
(Delivered some time Wednesday Morning. Shes' usually home in the mornings, so I've asked her if she can be home Wednesday Morning to receive a very important package for my project, she just doesn't know its flowers for her...yet....)
I'm sure I've left off and forgotten a million vendors.
Our New Logo....
What would a new logo be without a Tee shirt Shop...
Buyer Beware I have not yet seen this printed on a Tee shirt.
The colors may not work... I've ordered a few I will update
the blog with a good/bad review later this week when they arrive.
Friday, May 18, 2007
A trip to DC
On Monday I flew to DC to meet with AST to discuss my draft experimental permit application and to attend the Experimental Permit workshop. After this series of meetings I'm feeling pretty good about the paperwork side of the process. AST did not ask for anything that was at all unreasonable. The comments to my draft application were entirely reasonable and I'm very hopeful that my next submission will be judged as "Complete enough" to start the 120 day permit clock. Now back to actually building a vehicle capable of competing.
While I was in DC I went to visit the Aerospace museum. It was really sad that the only launch hardware advances in the museum newer than 35 years old was Spaceship one.
We made incredible advances in the 50's 60's and early 70's, since that time we have done nothing to extend that legacy of development. What we have instead is an entrenched NASA bureaucracy striving to get funding for a development boondoggle of biblical proportions.
While I was in DC I went to visit the Aerospace museum. It was really sad that the only launch hardware advances in the museum newer than 35 years old was Spaceship one.
We made incredible advances in the 50's 60's and early 70's, since that time we have done nothing to extend that legacy of development. What we have instead is an entrenched NASA bureaucracy striving to get funding for a development boondoggle of biblical proportions.
Sunday, May 13, 2007
Testing 5/12 (sort of)
After the last test sequence I did some more igniter test work and made a few changes:
We have been bringing our own LOX out to the test site, but this time we were bringing two barrels of Ethanol and did not want to carry both on the highway at the same time. So we had the LOX delivered. We arrived at the test site about 00:30 Saturday morning. As we unpacked and got ready to camp we noticed a loud hissing noise and discovered it was the lox dewar venting, It was completely empty. The short version is no LOX no testing.
Saturday was scheduled to be a FAR work party weekend, so we spent the day working on the facility. We shovled the sand out of the block house, and laid out and leveled the Emergency Medical Evacuation Helipad. (Just happens to be a 10M diameter circle.)
On Monday the 14th I fly back to DC to talk to the FAA about my experimental permit and to attend the experimental permit workshop.
- Increased the orfice sizes raising the igniter chamber pressure from 80 to 160 PSI.
- Changed the check valves to metal seat check valves and moved them closer to the igniter.
- Added a sintered fuel filter to keep from plugging the fuel orfice.
- Changed the orifices from steel to stainless.
We have been bringing our own LOX out to the test site, but this time we were bringing two barrels of Ethanol and did not want to carry both on the highway at the same time. So we had the LOX delivered. We arrived at the test site about 00:30 Saturday morning. As we unpacked and got ready to camp we noticed a loud hissing noise and discovered it was the lox dewar venting, It was completely empty. The short version is no LOX no testing.
Saturday was scheduled to be a FAR work party weekend, so we spent the day working on the facility. We shovled the sand out of the block house, and laid out and leveled the Emergency Medical Evacuation Helipad. (Just happens to be a 10M diameter circle.)
On Monday the 14th I fly back to DC to talk to the FAA about my experimental permit and to attend the experimental permit workshop.
Testing 4/28
I'ts been 4 weeks since I last offered an update. We have been testing every 2 weeks, two weeks ago we went out to test with the goal of improving our ignition reliability and doing some throttle testing.
After reviewing the data from our earlier test series we learned that the fuel and LOX pressures were not coming up evenly to the commanded start position. The end result is that we tried to start at idle and then powered up to full throttle. We probably did this before the chamber was 100% lit causing harder starts. So we modified the software to change this sequence and went out to try again. The only physical change to the motor was a change from bolted to snap ring closures on the motor.
We tried to start the motor 4 times with only one successful light. After the first two failures to light we changed the software back to its origional condition and tried a third time, still no light.
So some diagnostics showed that the igniter fuel solenoid was dead. We replaced that and tried a fourth time. We did not switch the old software back to the new so for the forth attempt we successfully lit the motor but it started a bit hard. At this point we were suffering for the 3 failed attempts as we were running low on presurant gas. The video camera had also been running for more than an hour and it gave up the ghost so we got no video of the 4th run. The 4th run was a 30 second throttle test.
As we had been messing with the igniter connections diagnosing the no-light issues the igniter plumbing connection at the fuel solinoid was loose so we got chamber gas flow backwards into the igniter at about 20 seconds into the run the fuel solenoid decided it had had enough of hot gases leaking at it and let a burst of fuel into the aluminum line between the chamber and igniter. The mixture was just right to detonate in the line. So we have a small bulge/hole in the fuel line between the igniter and the fuel solenoid. At or near the same time the chamber pressure transducer disassembled it self. We did not notice any of this from the block house the only thing we knew is that the chamber pressure went to zero. The motor continued to run
and did its throttle steps for another 10 seconds or so. This chain of events is pure speculation based solely on the visual state after the run and the data we collected.
When we returned home and disassembled the motor we also determined that the injector plate was bent.
After reviewing the data from our earlier test series we learned that the fuel and LOX pressures were not coming up evenly to the commanded start position. The end result is that we tried to start at idle and then powered up to full throttle. We probably did this before the chamber was 100% lit causing harder starts. So we modified the software to change this sequence and went out to try again. The only physical change to the motor was a change from bolted to snap ring closures on the motor.
We tried to start the motor 4 times with only one successful light. After the first two failures to light we changed the software back to its origional condition and tried a third time, still no light.
So some diagnostics showed that the igniter fuel solenoid was dead. We replaced that and tried a fourth time. We did not switch the old software back to the new so for the forth attempt we successfully lit the motor but it started a bit hard. At this point we were suffering for the 3 failed attempts as we were running low on presurant gas. The video camera had also been running for more than an hour and it gave up the ghost so we got no video of the 4th run. The 4th run was a 30 second throttle test.
As we had been messing with the igniter connections diagnosing the no-light issues the igniter plumbing connection at the fuel solinoid was loose so we got chamber gas flow backwards into the igniter at about 20 seconds into the run the fuel solenoid decided it had had enough of hot gases leaking at it and let a burst of fuel into the aluminum line between the chamber and igniter. The mixture was just right to detonate in the line. So we have a small bulge/hole in the fuel line between the igniter and the fuel solenoid. At or near the same time the chamber pressure transducer disassembled it self. We did not notice any of this from the block house the only thing we knew is that the chamber pressure went to zero. The motor continued to run
and did its throttle steps for another 10 seconds or so. This chain of events is pure speculation based solely on the visual state after the run and the data we collected.
When we returned home and disassembled the motor we also determined that the injector plate was bent.
Monday, April 23, 2007
An overdue update...
This last weekend I went to the NG-LLC summit at Holloman airforce base in New Mexico. I have not been officially notified that this is not secret, but I found a bunch of references to the 2007 XPC being at Holloman on the web via Google so by the terms of the NDA its no longer secret. We got to chat with a number of the airforce people and it was a productive meeting.
I think it will be cool to fly at the base and I'm a bit worried about the red tape.
The Airforce Officers think it will be cool for us to fly at the base and are a bit worried about our lack of red tape... All in all a good balance. The Base looks like a good site if the MPL insurance issues can be worked out. A single F117 stealth fighter inside the NG-LLC flight hazard area would make the Maximum Probable Loss so high we could not afford insurance....
(I believe that holloman has the only F-117 fighter wing.) So the FAA, XPC and air force are playing with maps and trying to put us where:
Tonight I disassembled the motor I ran for 106 seconds to look for the leak.
Its very obvious that the oring was cut on the screw holes during assembly.
Charles Pooley nailed it for an explanation. I'm going to rebuild that part and try again on Saturday.
I bought a new(to me) truck since the old one died and I wanted something with a tad more creature comforts for driving to the test site. An 18 year old truck with stiff off road suspension and no air conditioning was a bit stressful. I bought a used Dodge RAM 1500 Quad cab. Its a nice looking truck, I almost feel sorry for what we are going to do to it in the next six months.
Lastly I sent my FAA/AST contact a mostly complete draft of my experimental permit application. This has been a real challenge for me as I would rather chew off my right arm than work on paper work. Many thanks to Mike Kelley (who has been asisting me in this effort) for listening to me whine and offering useful suggestions.
I think it will be cool to fly at the base and I'm a bit worried about the red tape.
The Airforce Officers think it will be cool for us to fly at the base and are a bit worried about our lack of red tape... All in all a good balance. The Base looks like a good site if the MPL insurance issues can be worked out. A single F117 stealth fighter inside the NG-LLC flight hazard area would make the Maximum Probable Loss so high we could not afford insurance....
(I believe that holloman has the only F-117 fighter wing.) So the FAA, XPC and air force are playing with maps and trying to put us where:
- We cant hit anything valuable.
- The crowd can see us.
- We can't hit the crowd. (see #2)
- The Airforce does not have to move anything unmovable.
- The operating area is not a three day drive from the staging area.
Tonight I disassembled the motor I ran for 106 seconds to look for the leak.
Its very obvious that the oring was cut on the screw holes during assembly.
Charles Pooley nailed it for an explanation. I'm going to rebuild that part and try again on Saturday.
I bought a new(to me) truck since the old one died and I wanted something with a tad more creature comforts for driving to the test site. An 18 year old truck with stiff off road suspension and no air conditioning was a bit stressful. I bought a used Dodge RAM 1500 Quad cab. Its a nice looking truck, I almost feel sorry for what we are going to do to it in the next six months.
Lastly I sent my FAA/AST contact a mostly complete draft of my experimental permit application. This has been a real challenge for me as I would rather chew off my right arm than work on paper work. Many thanks to Mike Kelley (who has been asisting me in this effort) for listening to me whine and offering useful suggestions.
Sunday, April 15, 2007
Seal problem looking for suggestions...
In reviewing the video for Saturdays test I realized I have a seal problem.
The first short test:Video
The second long test:Video
If you look at the very bottom end of the motor on the first run there is a minor leak/spray where the throat seals to the outer aluminum. On the second run this is a huge gushing torrent until the copper throat gets hot enough to seal. (You can also see where this leak seals up on the chamber pressure graph)
The seal is is a a 1/8" 0.139 nominal high temperature o-ring.
The mechanical details are shown below. The pressure is about 350 PSI not trivial, but not huge either.The clearance between the copper throat and aluminum outer closure in almost zero. The motor was assembled with a rubber hammer its very tight. Its quite clear that the seal failed after the first test. Any ideas on what is wrong?
The first short test:Video
The second long test:Video
If you look at the very bottom end of the motor on the first run there is a minor leak/spray where the throat seals to the outer aluminum. On the second run this is a huge gushing torrent until the copper throat gets hot enough to seal. (You can also see where this leak seals up on the chamber pressure graph)
The seal is is a a 1/8" 0.139 nominal high temperature o-ring.
The mechanical details are shown below. The pressure is about 350 PSI not trivial, but not huge either.The clearance between the copper throat and aluminum outer closure in almost zero. The motor was assembled with a rubber hammer its very tight. Its quite clear that the seal failed after the first test. Any ideas on what is wrong?
Saturday, April 14, 2007
106 second burn Good Motor/Bad Motor
Good Motor:
We ran the 250lb regen motor again today. We ran from full tanks to depletion at full throttle, between 105 and 106 seconds. It lit a bit hard, and it had a bad fuel leak, but otherwise it was an almost perfect run. The video up on youtube .
Bad Motor:
On the way home going up the hill on hwy 14 we blew a head gasket in the truck. It took 6 quarts of oil and 2 gallons of water to get home.
Data:
The data is below. the Load cell gave me qualitatively reasonable data, but the calibration can't be right, with the measured chamber pressure and throat size, I'd see more thrust with no expansion cone at all.... alas there is something I don't understand about the load cell calibration.
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