August 16, 2003 Notes
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.
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.
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
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 Russs 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.
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
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.
1: 1 SCFM air flow
temp: 87.3 F
cabin was then left open for 15 minutes, but it didnt cool back down to the
2: 2 SCFM air flow
temp: 88.4 F
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
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
We wound up with a richer than usual propellant mixture,
because I didnt 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. Im curious how much of the difference is
due to the richness versus the fact that nozzle exhaust is a lot cooler than
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>