There are a bunch of details missing such as braces for the motor,electronics boxes, jet vanes vents etc…. but it’s aproximatly right.
Thursday, March 27, 2008
Wednesday, March 26, 2008
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.
Saturday, March 22, 2008
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.
Monday, March 17, 2008
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
Sunday, March 16, 2008
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.
Friday, March 14, 2008
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!
Sunday, March 09, 2008
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.
Saturday, March 08, 2008
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.)
Wednesday, March 05, 2008
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 14th.
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.
Monday, March 03, 2008
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.
Sunday, March 02, 2008
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.