August 16, 2003 Notes

 

Miscellaneous

 

The space suit gloves arrived, along with a communication helmet that goes inside the suit.  The Russian that sold them to us also tossed in a few Buran heat shield tiles for free.  We will start making some adapters and pressurizing it in the coming weeks.

http://media.armadilloaerospace.com/2003_08_16/suitAndGloves.jpg

 

We built a strain relief for the wiring going underneath the base of the vehicle, epoxied the entire harness to the side, then put on a layer of micro balloon filled epoxy so we can sand it down smooth later.

http://media.armadilloaerospace.com/2003_08_16/wires.jpg

 

I made all the 4 degree angle shims to cant the engines on the big vehicle.  This requires two on top of the plate that actually hold the engine at the right angle, then four underneath the plate that angle the nuts clamping the engine down.  The small vehicle has the same arrangement, but one problem we had was that it was easy to get the shims spun the wrong way when you replaced engines, so this time Russ tack welded them permanently to the mounting plates.  We also realized that I could have milled little four degree pockets on the bottom side of the plate when I cut the bolt holes for them on the mill, which would have saved two thirds of the work – only the top two shims would then be required.  I will do this when we make plates for the big engines.

http://media.armadilloaerospace.com/2003_08_16/shims.jpg

 

We received our batch of 5.5” diameter spreading plates from Global Stencil.  I believe these were laser cut, but they are perfect for our needs.  We made our last spreading plate with 1/16” holes, and we broke a ton of drill bits on Russ’s PCB milling machine trying to go through 0.030” thick stainless.  Getting a bag of 20 made was much nicer.  The new ones have four times the holes, with the hole size reduced to 0.030”, and the center blocked off to avoid the inlet pressure feed spike.  We did some tests and found that the slight dome at the top of our engines ( 0.25” higher at the peak ) is sufficient spreading height, so we welded the spreading plate in without any additional spacers.  A couple places at the edge got a little warped by the welding, but overall it works very nicely.

http://media.armadilloaerospace.com/2003_08_16/spreadingPlates.jpg

http://media.armadilloaerospace.com/2003_08_16/waterTest.jpg

 

One thing we found after using the new engine for a while was that heat cycling caused the slightly warped plate to pop “over center” up towards the inlet, nearly closing it off completely.  We popped it back down, but in the future, we are going to weld a little dividing bar in the center that guarantees it stays 0.25” away from the top of the motor.

 

We repacked the main parachute for the small vehicle, and made some improvements to the pneumatic system.  We have been operating the ejection tank at 600 psi, but when you fill it that high, the quick connect is very difficult to remove, often requiring you to rap on it with a wrench or hammer to pop it off.  We added a check valve in line with it, and a manual valve on the fill hose, se we can now bleed the pressure off before doing a disconnect.  We always had to have arrangements like that for the ½” and larger fill lines, but we had been sort of dodging it on this ¼” fill line.

 

We did a bunch of plumbing layout for each individual engine, both the propellant and preheat lines.  It winds up looking pretty damn ugly, but we got it all in.  We are going to have a separate quick connect for each engines preheat, rather than adding a distribution manifold on the vehicle.

 

We expanded the pilot hole in the middle bulkhead and started testing some ingress / egress issues.

 

We hammered out the bent top lip on the cabin that was damaged during the helicopter drop test.  We are going to build a completely new cabin with several improvements, but we may reinforce the current one for some operational uses.

 

Cabin temperature tests

 

We did a more rigorous test with someone closed up in the cabin with forced air providing both breathing air and cooling.  We added an air circulating fan inside, which mad it more comfortable at all levels.

 

Test 1:    1 SCFM air flow

 

Starting temp:    87.3 F

Minute 1:         88.0

Minute 2:         88.0

Minute 3:         88.0

Minute 4:         88.2

Minute 5:         88.4

Minute 6:         88.6

Minute 7:         88.7

Minute 8:         88.7

Minute 9:         88.7

Minute 10:        88.9

Minute 11:        89.1

Minute 12:        89.1

Minute 13:        89.3

Minute 14:        89.5

Minute 15:        89.5

 

The cabin was then left open for 15 minutes, but it didn’t cool back down to the original temperature.

 

Test 2:    2 SCFM air flow

 

Starting temp:    88.4 F

Minute 1:         88.4

Minute 2:         88.6

Minute 3:         88.6

Minute 4:         88.7

Minute 5:         88.7

Minute 6:         88.7

Minute 7:         88.7

Minute 8:         88.7

Minute 9:         88.7

Minute 10:        88.7

Minute 11:        88.7

Minute 12:        88.7

Minute 13:        88.7

Minute 14:        88.7

Minute 15:        88.7

 

We are probably going to provide enough air for at least 4 SCFM flow, so we can counteract some of the aerodynamic heating during flight.

 

Open catalyst tests

 

We performed some very interesting tests, running engines with the nozzle removed so we could directly watch the catalyst surface during operation.

 

We tested the 4” thick ceramic catalyst on the new spreading plate engine first.  In tests with the propane preheat, we still needed 10 20 mesh screens between the spreading plate and the catalyst block to avoid any noticeable hot spots as the catalyst heated.  This was a bit of a surprise, because that was the same number needed on the previous spreading plate that had only a quarter the hole count, with holes four times as big.

 

We used a small cavitating venturi to limit the flow to about 140 g/s, since the engine was obviously not going to have any back pressure.

 

We wound up with a richer than usual propellant mixture, because I didn’t bother pumping more peroxide out to make it perfect, but there was a HUGE amount of flames coming from the catalyst pack on our tests, especially considering that we were only flowing the equivalent of about 50 lbf thrust worth of peroxide if there had been a nozzle on.  I’m curious how much of the difference is due to the richness versus the fact that nozzle exhaust is a lot cooler than catalyst exhaust.

 

It was very interesting watching the glowing hot catalyst surface spewing tons of flames out, then seeing an area start to darken, then liquid draining out from that area, and others starting to darken.  The splotchy pattern that darkened first was exactly the same area that shows poor propane catalyzation when playing a torch on the surface, a definite sign of weakened catalyst.

 

We then put back together the rolled foil engine for a test of that.  The catalyst is unrolling and rather falling apart, but we stuffed it together as best we could.  We kept the same “high flames” propellant mixture for comparison sake.  It also cooled off in spots and started draining liquid through.

 

Both of these catalysts were already used and damaged, so we are very much looking forward to repeating these tests with fresh catalyst and FMC purified 50% peroxide.  Being able to literally see if the liquid is coming through the center, the sides, or some other spot is extremely valuable.

 

<check back later for the video>