Sphere vehicle rough rendering

There are a bunch of details missing such as braces for the motor,electronics boxes, jet vanes vents etc…. but it’s aproximatly right.

Autonomous Hover Video

Not produced to the best quality, but it shows the helicopter hovering,

both in manual altitude and full altitude hold modes..

 

Autonmous Hover

I just finished flying out an entire Trex battery pack in 3 axis autonomous position hold hover. (Altitude was still manual) I set the reference position landed, moved the helicopter and it returned to the commanded position from 10 yards away with displacements both north and east of target. Hover never seemed to deviate by more than 1.5m from center. At one point the hold position moved about 1m in a pronounced step, I have not analized the telemetry yet, but I assume this was a change in the GPS sats tracked. This was done with the Hemisphere GPS in 20Hz update mode, but without the differential corrections. I will attempt to acquire video to bring with me to space access. I’ll post telmetry details later tonight.  

More Pictures....

The whole assembly is upside down.

From Top of picture to bottom…. Motor (not yet welded together) Big stainless check valve, main valve, tank(100% welded) plastic bucket. We will provide some pictures of the tanks in process as our welder Bob took some pictures, but I don’t have them yet.

Detail shot of the gear mount. (Upside down) 

Detail shot of the Tank Top…

 

So far the tank is about 5% over the “Spread sheet” target weight and the motor is 50% under the spread sheet SWAG, In total all parts we can weigh are comming in under the target weight.

The motor exit cone needs to be shortened a bit and the main chamber will shrink as we have a really parinoid L*. We are missing one small fitting for the Catalyist injector fittings or the whole motor would get welded together today. The local indusrtial hardware store is usually open on Saturday, but they closed for Easter.

Data Results

We went back out and reran the test after the purple nighmare.

Here is the pressure data from the decomposition test. Note that the chamber pressure dropped off more than the feed presure did this makes me think the excess permangnate at startup had a positive effect and we would benifit from from some kind of screen in the chamber to hold the reactant products longer. Note how the feed pressure drops off rapidly when the peroxide runs out.

 

Here is the data with thermocouple voltage data added. One channel did not work at all and the data is very puzzeling. TC1 (not shown) is at the exit with TC2,TC3,TC4 getting closer to the Injector end. Either I have my wireing notes wrong (possible) or I don’t understand the data.Why would the thermocouple in the middle be lower than the one on the ends?I have not calibrated the thermocouple data, its displaying scaled RAW A/D counts. From the noise its clear I need to work on my TC amplifer some more.

Here is the video from the test series

 

 

The Purple Menace strikes back.

A quick update, we’ll post videos and more info in a couple of days. We went out to FAR to work on the site and run a quick repeat of our decompoisition test. When we ran it a flxible stainless line from the  permangenate tank to the motor failed at the fitting spraying permangenate everywhere. We had gotten a bit lazy and did not remove the tools generator etc.. from the vicinity of the test stand. SO everything involved with the test is covered in fine purple goo. We only used 1 liter of permangenate ,but 1 liter covers a truely amazing amount of area. The leak was at about 300 PSI so we covered  everything in a 35 foot radius with purple goo.  I can’t find the reference, but somewhere I’ve seen a dilution ratio of 10000:1 specified for making the purple go away.I can personally vouch for that number. I can also vouch for the warning one of the Arocket chemists gave me that vitamin C solution is exothermic with concentrated permangenate. A Vitamin C and  soaked shop rag used to wipe down  permangnate splash will end up smoking.

Progress...

This morning I had a conference call with the FAA to talk about getting started again.  With the rapid progress we are making on the simple vehicle there is a very real possibility that the ability to get a burn time waiver will become a limiting issue. So I need to go back into paperwork mode, the most fun part of the project!

Based on some feedback from John Carmack and some personal experiences trying to get Large fittings to seal we are switching to sanitary fittings for all of our large plumbing. We have always wanted to use a butterfly valve for better throttleing and less hysteresis, this is hard to do with lox as no seal material is soft at Lox temps. With peroxide its a bit easier, we found a 1 inch butterfly valve with built in sanitary connections and hydro tested it to 500 PSI. It held fine and operated correctly. Its nominal commercial rating is 150PSI, we are going to run it to 300 PSI. My son designed and machined a two peice aluminum housing to hold the valve and connect one of our servos to it.

Its a fast 1” valve.

 

How come we spend so much time on valves? Here is the dual igniter valve we made last year…

 

This weekend we are going out to FAR to rerun the L* test with sodium permangenate. We are also going to do a bunch of site improvement work, trenching, running power and data wires and boring the big hole to put the foundatiuon in for our tether crane.

 

Stunning Rocket news: at 8:10 PM everything is packed and I might get a full nights sleep before a test!

Helicopter Tanks and Shuttle

HelicopterI’ve got the helicopter flying in attitude hold more, but I have not yet turned on the postion hold software. I want to review the data from an atitude hold flight before turning on the position hold. So I went out and flew the helicopter again today. Data records fine at home, it records fine according to the lights on the recording unit, alas when I get home and look at the SD card no data. Arghhhhh….

Tanks We did a lot of prep work on the tanks today, we figured out what brackets, fittings etc… need to be welded on. I also machined some Aluminum sanitary fittings for the main propellant line. My  mcMaster sanitary parts arrive on Monday so I’ll see how well I did with the aluminum ones on Monday. One of the hemispheres has a stress crack that goes all the way through. I hope this is not an omen for the whole set of 6. I think I can probably stop drill the cracks, grind them out and weld patches over them, but its less than ideal. We’ll save that hemisphere for last.

Shuttle One of my long term really want do to items is to watch a shuttle launch. I’ve seen it land 3 times (including the very first time), I’ve never seen it launch. Tuesdays launch will be a night time launch and should be quite spectacular. I came real close to hopping on southwest and flying out to florida to see the launch. I would have cost me $800 two days of works work and at least one day of Unreaosnable work and in the end I decided that I really want the time to work on Unreasonable. We are so close to having every thing come together for the new 90 second vehicle. So I’ll try to be less impulsive and plan ahead to go see the next launch.

Parts

The new 1” (or possibly 3/4”) valve mechanics.

The baffels for the new tanks… they still need to be trimed, fitted and welded.

Parts for the potential off the shelf monoprop chamber only welding required… (Will probably up the base tube size for a shorter chamber.)

 

Data and Plans

Based on a lot of discussion with the chemists on Arocket its clear that the potasium catalyst was about 1/7th as active as the sodium catalyst I’d designed for. So we need to rerun the test when we get our sodium permangenate. We have it on order from two different sources. I finally reduced the data from my test and I got zero thermocouple data. I need to work on that. We hope to rerun the test on the 14^th.

Here is that data I did get.

Several things to note. first off my pressure regulator is not healthy. Its hitting the correct final pressure, but it is not happy doing so. Second according to the CV calcs I did the 1/2 inch valve should have about 10 PSI drop at full flow, it clealry had 150 PSI of drop. This could be because chamber pressure did not come up due to incomplete decomposition, but in that case I would have expected a larger injector drop due to too high of flow. Toward this end I spent the last two nights fabricating a fast 1” ball valve controller, I’m waiting for one more McMaster part and I’ll test it Thursday night. 

We are currently fleshing out the details of our 90 second test vehicle. We made baffles and parts for welding the tanks together. I’ll provide pictures when the tank starts going together. The last parts should be back from the Water Jet Cutters Friday. We are going to use AN fittings for all the plumbing smaller than 3/4 and probably sanitary fittings for the larger plumbing.  We have one area where the two Pauls do not yet agree, we can’t decide if we are going to use attitude thrustors or jet vanes. For the monoprop the jetvanes are clearly a win, but our longer term plans include making the vehicle a bi/tri prop by adding fuel to the peroxide and getting more performance. The bi/triprop  is a bit warm for jetvanes. It probably means we need to use some kind of exotic refrectory metal or ceramic. The bi/tri prop is the  current path to the 180 second prize.

For the Monoprop the safety system will be easy, we will add one small normally closed  valve to the liquid catalyst. As you can see in the video the thrust stops abruptly when the catalyst is all gone. (You can also see this in the chamber pressure trace above)  The bi/tri prop is more problematic as one might expect the biprop to keep going even if you turn off the catalyst.  If all goes well we expect a compete monoprop vehicle in about 6 weeks. We have all the long lead parts in hand. The current design is really really simple

I’ve glossed over a whole bunch of work… cat pack research, small thrustor chambers, learning about peroxide chemistry,high temperature ball bearings,  big servos, off the shelf source  thrust chambers, work on the helicopter, etc.. etc…

I’ll present the details of the 90 second monoprop vehicle design at Space Access. We will be at Space Access for all three days.If you are a space fanatic, and enjoy hanging out with three sigma nerds you can’t beat space access. 

Testing new Blogtools

To date I’ve been doing all my blogging with the blogger online tool. It is really limited, today I’m trying a desktop blogging tool. I’m hoping it will make things a little easier.

This picture was taken by Ben Brockert, one of the Masten guys that came out to watch the test. As he says ("Where's Waldo" bonus: find Paul's foot) Also notice the wind swept hair and the flapping tee shirt. It was REALLLY blowing.

Here is the You tube video embedded in the blog. The tool I’m trying is blogjet.

The Purple Menace

Saturday we went out to FAR and ran a test to determine Peroxide decomposition L* for a liquid catalyst. We were unable to get Sodium Permanganate for this test so we ran it with Potassium Permanganate. This results in about 1/4 the amount of effective catalyst. The end result is that we did not get full decomposition. The peroxide was still cloudy at the end of the tube. We did however fully check out a new test stand and data collection. All the parts worked correctly. A lot of people have told us that Permanganate makes an insane purple mess. Part of this test was to determine if we could handle this "mess". Thanks to a suggestion on Arrocket we mixed up a saturated solution of Vitamin C powder and that cuts the purple menace, making cleanup a non event.In the test setup we had insufficient permanganate so 100% of it was reacted in the engine leaving the engine perfectly clean. The only purple goo was from filling the cat tank.

The Last time I was out at FAR it was really pleasant. Nice lite breeze, moderate temperatures in the liow 70's and generally jerust a pleasant environment. So I convinced my desert hating wife to come with me this time. This must have angered the mojave deity as the wind was blowing so hard it felt like you were being sandblasted. The wind was blowing so hard that 2.5 GAL distilled water jugs 2/3 full were blowing over. It actually complicated the peroxide handeling, as we were in a blowing catalyst blizzard. It also made the personal protective gear hard, as the wind would blow a full face shield off in an instant. Also when you get peroxide on you it stings/burns, the blowing sand/rocks/boulders also sting. We were forever walking up to each other and saying any white spots on my face? The answer was always no, so we had no peroxide issues, but the sand was really unpleasant. There was a discussion of what was worse the wind or the 125degree heat we've seen on the site. Most preferred the heat, then John, who lives near FAR, said why do you think you would not have both? That pretty much ended the what if discussions involving mojave weather.


I've posted a a quick youtube video of the test. As a side note this test went from a concept to a test including assembling a test stand, fabricating a test motor and custom thermocouple electronics in 7 or 8 days.

Hardware, Rocket Hardware

If I learned any lesson from last years attempt its KISS keep it simple stupid.
A 4 engine vehicle with 39 valves is not going to fly reliably. Toward that end this years vehicle is going to be much simpler. Today I got a package...



The more I work on this stuff the smarter John Carmack gets... these are 6 5086 spun aluminum hemispheres from AMS industries.




They are 30" ID 0.1875 inch at the base 0.171 thick at the edges. 19 lbs each half. This should conservatively give me a burst pressure between 600 and 800 PSI. I'm shooting for 500, so I may lighten them a bit. The edge thinning is a lot less than AMS said it would be so I could have gone down a size in the thickness and saves some weight.

Given KISS what is the simplest system that will do the level 1 prize?
A Peroxide monoprop.
Everyone who works with peroxide spends inordinate time playing with cat packs. So I'm going to test a liquid catalyst like the Germans used 65 years ago. Using 85% peroxide I'm well under the melting temperature of 316 stainless so no cooling is needed I can just use a stainless chamber. I can also buy No clog spray nozzles in 316 from McMaster Carr and use off the shelf spray nozzles. The big question I have is with a liquid catalyst, what do I need to L* or chamber length? So I got a simple experiment I hope to run this weekend, its a long Stainless tube with 316 stainless pipe fittings welded in one end. In the pipe fittings I screw in off the shelf low clog spray nozzles and install thermocouples down the length of the tube to see what length is necessary to get maximum decomposition temperature.

Bittersweet day

My son and I spent the day cleaning out the garage in anticipation of getting back to rockets.
Part of this involved taking the carcass of the origional Unreasonable rocket to the aluminum scrap dealer. We both agree that a 4 engine vehicle is just too complex, but its still sad to take brackets, fittings and tanks one worked hundreds of hours on back to the scrap dealer.

Progress and thoughts...

I flew the helicopter in attitude hold mode today.
It worked perfectly. the autopilot flys a lot better than I do. On flight #2 the commercial off the shelf RC regulator failed and the servos acted very erratic.I set it down with no damage. More debugging Sunday.

My son and I spent the day at FAR, we went out to clean up our storage space, work on the site and watch a large 5K liquid test firing. The work on the site is the real sexy part of rocket development. I spent my morning repairing the outhouse door jamb and installing godzilla's own door closer. Maybe the Mojave winds wont rip the outhouse door off, again.

After a full day of checkout the large test was a no light with a frozen LOX valve. We were not involved other than as spectators. My son has been working with some people doing peroxide rockets of various forms,and the grass on that side of the fence looks a lot greener.... Use cheap nitrogen for a presurant gas, all your valves and plumbing are at room temperature, dense, reasonably clean. Possibly auto igniting in bi-prop mode after decomposition.... hummm....

Quick Update

I've been very busy with "Other" mostly trying to catch up on work. I've been doing some work on the helicopter and I've flown it a few times, but no big news to report on that front. I've started testing with the DGPS and I've come to the conclusion that I need better antennas to make the RTK work. My one successful RTK test with the antennas on my roof took 46 minutes to resolve the integers, and then the solution was accurate to within 6" at 10Hz for 10 hours. The average RTK solution between the antennas was 20.02" with actual measured truth being 19.75". My son has come back down from the bay area to work on some rocket projects, both unreasonable and other..... I can't talk about "other" other than to say it is a paying gig. I'm glad to have him home.

I also find it frustrating that its sunny all week when I can't fly, then it rains all weekend where I can't fly.(Actually it stopped raining during the super bowl and I choose to watch that) This week is not going to be "unreasonably " productive as I have a lot of stuff going on.

Sunday, Loops and Simulation

The Simulated weather for Sunday was Rain all day. The Reality was that after 10am it did not really rain again until 4:00pm. So I went flying. I'm currently working on altitude hold, but the wind was really gusty gusting from 5 to 20mph. A helicopter takes less energy to fly when moving than when it is hovering. If you try to hover in one spot with gusty winds the helicopter balloons up and down as the wind speed increases and decreases. This makes it very hard to sort out the altitude hold loop as you are never sure if the up and down is wind or oscillation's. I could hover lower and get a better handle on how the altitude loop gain is but until I have it hovering at high (recoverable) altitude I'm not going to play with the altitude hold down low. The altitude hold will have to wait until a calmer day.



So since I could not do altitude hold I thought I'd work on heading hold. In flying around with the magnetic heading hold engaged the helicopter seems relatively stable but the tail wandered a few degrees each way. I always thought that it was some local magnetic variation, that may contribute, but in looking at the data the tail target vs actual error is often 3 to 6 degrees and it wanders a bit. It seems to hold an offset. The standard way to fix this in a control loop is to add some integral error term and the result is The oscillation's you see on the left. So I turn down the I term (to 5% of the P term) and turn up the D term and its better, but still not ideal. You can still see some 3 to 4 second oscillations when steady and a fair bit of overshoot when perturbed. I'd been doing the default PID tuning of turning the P gain up to the point where it just starts to oscillate and taking the Ziegler-Nichols values you can find on the web. I conceptually understand what is going on, but this is straining my control system theory. (My only official control theory class was all done as laplace transforms in 1983) Early in my professional career(1985 to 1991) I did a fair number of analog and mixed analog/digital control systems, but always with a adult supervision from a controls person. Since 1991 I've mostly been a software coder. So in trying to relearn all of this I have a several specific questions that I'd love have any lurking control theory guys help me with.

Most control theory books, articles and tuning discussions assume you have a linear plant. In reality most of my "Plants" will be integral in nature. IE I do not control the thing I'm trying to close the loop on directly, I really control the acceleration or rate. So there are one or two physical integrals between my control input and the thing I want to control. See the example to the left.
If I just close the loop around the whole thing, its going to be really unstable. So my plan was to have Target Position yield Target Velocity Target Velocity yield target Pitch and Target Pitch yield Pitch Rate. This would have hard limits for each intermediate step. IE max velocity will be 5m/sec, regardless of the position error. Clearly every intermediate step in this will have a proportional gain term, any advice on which ones should have integral terms and when I should reset the integrals to zero?





I'm also struggling with a stupid simple question I have about PID terminology. You can express a PID as

control= P*(error+I*integral+D*difference_or_rate)

or You can express a PID loop as

control = (P*Error)+(I*Integral )+(D*difference_or_rate)

When you look at the standard Ziegler-Nichols chart :
for PID P = .6Gu I=2/PU D=PU/8 Is this for the first form or the second? When you measure Pu I assume Pu is the oscillation period in samples (this is a discrete system), or have I made a wrong assumption here?

Lastly is the guidance for standard linear PID tuning even valid for this sort of plant? If not can one provide some guidance on tuning such loops?

It Never Rains in Southern California

Notice the Probability of precipitation line...90% at 1AM 100% for the rest of the day. No FLying today.

Pavlov's Pilot

After two outings where I hit the altitude hold switch and I crashed, I was hesitant to test again. I reluctantly went out to test fly the helicopter today and on the second flight I got up the courage to hit the altitude hold switch and things seemed to work. I failed to get data from the second flight for some reason, probably has to do with the software in the Telemetry box not logging restarts correctly, but I'm not exactly sure why I got no data. I'm ready to test again in the morning.

Last Crash

The last crash was a bit violent. You can see the crushed tin that held the formerly working GPS.



I did not take a picture of the crashed helicopter, but here are some of the broken pieces extracted from the trash.



I was planning to replace the GPS with the new smaller differential capable GPS so I
packaged that in an altoids tin, its about 1/3 the size of the old GPS.

Here it is rebuilt and ready to try again. To get a concept of the amount of work, the main frame on the helicopter is flat carbon fiber plate, in the broken pieces picture you can see that both side plates were broken.