July 3, 2004 notes

 

Ready to fly

 

As far as we know, everything is completely ready for flight testing on the big vehicle, but we weren’t able to get our usual lift truck for testing on Saturday.  We did a lot of other miscellaneous stuff, but we are definitely looking forward to our tests on Tuesday.

 

The shock absorbers for the big vehicle are in ( mc64100-1 from http://www.parker.com/cylinder/cat/english/102202.pdf ).  I need to buy a 2mm thread mill so I can cut nice thick mounting blocks for these in the future, but for this vehicle I made some plates that capture the jam nut and let us screw the shocks through a form fitting tube and hard up against the base mount.  We need to land pretty straight with these, but they are only a third the weight of the big wire rope isolators, and they don’t have any spring back on landing.

 

http://media.armadilloaerospace.com/2004_07_04/shocksBefore.jpg

http://media.armadilloaerospace.com/2004_07_04/shocksAfter.jpg

 

We anchored a piece of road plate on the concrete so we won’t chew it up any more during hover tests.

 

http://media.armadilloaerospace.com/2004_07_04/roadPlate.jpg

 

We have modified the metal vehicle stands with some side legs, which we plan on using instead of the messy foam blocks for the first elevated hanging test, but after that proves out, we will do a ground liftoff while tethered under the crane.  After that, we will head to the 100 acres for a boosted hop.

 

We replaced the RTV insulation that caught on fire after the extended burn last week with furnace cement, which should seal everything off at any temperatures we can reach.  It isn’t clear that we need to go to that length just to avoid a little blowby past the jet vane shafts, but it shouldn’t hurt anything.

 

We have done significant rework on our test stand hardware to allow a better large run tank and some other improvements.

 

We did some tests with the fresh new 7” engine, but the spreading plate has too much flow for stable operation at full throttle right now.  We did find that the 2 x 900 cpsi catalyst monoliths were actually somewhat more difficult to start the warmup process with, supporting our theory that it won’t start when the methanol is able to decompose in the cold pack along with the peroxide.  If this theory holds, the pack will get easier to start after it wears out a little.  For now, it needs the slug-before-cracking procedure.  We ran a total of 30 gallons of propellant through it to see if it would stabilize after it cooked and pressed for a while, but I was still limited to about half throttle on it to keep it running smooth.  At the low flow rate, the engine got very hot all the way up through the bottom catalyst section.  At full flow rate, it will probably be cooler until near the bottom.  We are going to swap to a smaller spreading plate as soon as Global Stencil gets their laser fixed and finishes our order, which fixed the last 5.5” motor right up after we had problems with the high open area one.  We are also going to revisit using ethanol instead of methanol as the fuel, which may avoid the fuel decomposition in the cold pack issue.  We could never get ethanol going with glow plugs, but now that we have spark ignition it might work.

 

http://media.armadilloaerospace.com/2004_07_04/veryHot.jpg

 

We did several tests using the Liquox sodium permanganate instead of solid catalysts in a small test motor.  We had some periods of clear running, but it has generally been rough, and we have only seen 240C chamber temperatures so far.  We have several more things to try, but there are definitely some operational headaches to permanganates.

 

We started working on the new cabin-at-the-bottom design.  The hatch and hatch reinforcement are being fabricated, but we went ahead and cut out the reinforcement area from the cylinder for some test fitting.  This design can actually hold three people in pretty good comfort, unlike our cone cabin which was really only suitable for the ballasted “virtual passengers” required by the X-Prize rules.

 

http://media.armadilloaerospace.com/2004_07_04/newCabin.jpg

 

The ball is rolling on getting a carbon fiber wound 850 gallon tank, but the lead time is over three months.  We had been planning on using the 1600 gallon fiberglass tank, but after some thought I realized that paying the extra money for the smaller carbon tank will earn out over the flight test series by allowing us to use a smaller engine with less catalyst and by consuming less propellant on each test flight.

 

Neil traveled out to the Southwest Regional Spaceport to do a site survey for our waivered flight testing.  It looks good, but we are probably going to need to upgrade all of our transportation equipment so we can move our own nitrogen and vehicle erection equipment.