Feb 27, March 5, and March 9, 2002 Meeting Notes
I had to be out of town last Saturday, so we missed a
A big piece of news is that it looks like we have clearance
to fly our unconventional vehicles in Oklahoma. We have had two waiver requests denied here in Texas, but for the
last several months I have been working with the Oklahoma Space Industry
Development Authority (OSIDA) http://www.okspaceport.state.ok.us/
to try to secure facilities for our future testing.
Our particular vehicles are especially problematic, because
they dont fit any of the common FAA categories. Apparently, FAA Flight Standards in Oklahoma has decided not to
regulate our vehicles, passing authority to air traffic control. The tower at the Clinton-Sherman base where
most of the OSIDA activity will be has complete control to 4500, so we can
arrange to fly our vehicles in any configuration we want, and just clear it
with the local tower.
This is a Very Good Thing, as high altitude testing is
obviously a critical path item. 4500
isnt much, but it will be all we need for the next six months or so, and with
the precedent of clearing it with air traffic control set, we should be able to
arrange higher altitude windows later on.
We will still have to go through AST in Washington when we want to go to
space, but there is reasonable hope that altitudes as high as 100,000 may be
done with only regional oversight. It
wont be important for quite a while, but Oklahoma does have large enough areas
of low enough population densities for 100km flights, given AST clearance.
The OSIDA folks are making things happen Right Now. They are actively working the FAA and EPA
issues, and they have a number of incentives for companies that can relocate to
Oklahoma. Pioneer Rocketplane is their
big shot, but they are also working with a number of other companies. JP Aerospace is doing an educational high altitude
balloon launch for OSIDA later this month.
I will be signing an official memorandum of understanding
with OSIDA next week.
Mobile Test Trailer
When we first started, almost a year and a half ago, our
little angle-iron test stand with a four liter tank strapped on was a good
match for us. In the ensuing time, we
have had to add bigger tanks, bolt down holding points, a separate cart for all
the filling equipment, a separate box for the electronics, and recently, externally
regulated nitrogen, kerosene, and ethane tanks. It has gotten to be a pain.
Since we also know that we will be doing some very large
engine testing on the new vertical test stand out at the 100 acres, we have
decided to get a good sized metal trailer that we can secure everything onto,
including space for a drum of peroxide, drums of water, tools, etc. We will leave the little horizontal test
stand at the back of the trailer for engines under 1000 pounds of thrust or so,
and we will be able to just pull it up beside the (soon to be sunk-in-concrete)
vertical test stand for the larger motors and rotor tests.
This is going to make our setup time a lot quicker for our
normal testing, and make it a lot easier for runs out at the 100 acres. Joseph is going to make a cradle to hold the
lander in his truck bed, and pull the trailer behind.
We finally got a price quote from Ultramet http://www.ultramet.com/ for putting an iridium
oxidation protection layer (with CVD) on top of a small (2.75 diameter by 6
long) chamber and nozzle that we would machine out of TZM. They quoted $15,000 in tooling and $20,000
for the coating. Err, no.
I have another vendor that is going to get me a price for some
other coating options (silicides, etc), and worst case, we will try platinum
electroplating. In the end, it may be a
moot point, because our cooled engines are coming along a lot better than I
Haver Standard, the company that we ordered our pure silver
screens from, is claiming that the domestic unrest in India is preventing them
from shipping our order. We can get
screens from other places, but they are far and away the cheapest.
Our big rotor blades from http://www.vortechinternational.com/
arrived. The full sized blades are 13
long each, but we also got a scrap blade that we cut into two 6 blades to do
initial testing with. We built all the
parts and plumbing we needed for the hub, and got the short blades bonded on at
10 degrees pitch today. We will be
doing the final bolting and assembly on Tuesday. After much arguing, we finally settled on a tip engine mounting
scheme, which we will hopefully be able to test on Tuesday. It will be a bit odd looking, but it should
be quite secure.
The 12 diameter rotor is pretty sizable. The full sized rotor is going to be
huge. We will do some very low RPM
tests to make sure the test stand and plumbing are functioning correctly, then
move out to the 100 acres for spinning it up to higher RPM. Sonic tip velocity would be around 1600 RPM,
but we dont plan on spinning it that fast.
If we can make over 500 pounds of lift at RPM we are comfortable with,
we will probably mount the rotor on top of the current lander, so we can
investigate how attitude engines behave with a coupled rotating mass, which I
am rather unclear on at the moment.
We will make a new hub and engine mounts for the 27
diameter rotor, which is intended for our next generation vehicle.
Because we are going to use hard line tubing for running the
peroxide down the rotor blades, I have had to start buying some new classes of
tools and fittings. I bought a few
Yor-Lok compression fittings, but Doug Jones of XCOR www.xcor.com (buy an EZ-Rocket poster!) gave me
a bunch of pointers, and I am going to be moving to flare fittings, which
interoperate with our other AN plumbing.
We will probably be using hard lines for other plumbing in the future,
as it is a lot cheaper, lighter, and easier to make different sizes than
braided stainless hose.
Feb 27 Engine Tests
We rebuilt a 1 diameter cat pack with some minor changes,
and had four absolutely dead smooth runs.
We are still recycling the same screens, because we are still waiting
for our new catalyst order. These pure
silver screens are closing in on 1000 seconds of firing time, with no sign of
March 5 Engine Tests
We finally got around to measuring some chamber pressures
today. We replaced out fuel injector fitting
with a 2 long, 1/8 diameter stainless pipe leading to our transducer. Many months ago, we had tried putting the
transducer right on the engine, but it got too hot almost immediately, and
started reading ridiculous chamber pressures.
0.080 peroxide jet
250 psi ullage
We got a very strange pressure curve, starting out much
higher than the ullage pressure, then decaying to around 80 psi.
Same results. After
analyzing it a bit, we have decided that the initial compression of the air in
the 2 pipe is heating it enough to throw the transducer off for a while. I had been hoping to avoid having to pack
grease in the transducer, which will prevent us from using it on a tank again,
but it looks like we are going to have to do that to get good data. Still, we believe that the point that it
leveled off at is probably reasonably correct.
That was only 80 psi, which is quite a bit lower than we were thinking. This pack had a total of 106 screens, 20 of
which were 80 mesh, and the remainder were 20 mesh (alternate silver and
stainless). It was running with the
solenoid valve, and a restrictor jet.
400 psi ullage
140 psi chamber
350 psi (ran out of nitrogen on this tank)
We changed the solenoid out for one of our big ball valves
150 psi chamber
This showed that the solenoid was a significant pressure
increase jet size from 0.080 to 0.120
This showed that even with our smooth running pack, we do
still require a pressure drop at the jet.
Repeat run 4 to make sure it returned to smoothness. It did.
We could probably get a bit more chamber pressure by
experimenting with in-between jet sizes.
Increase pressure to 600 psi
270 psi? may not have leveled off completely
We will probably repeat some of these tests with a better
insulated pressure gauge at some point.
We then did some kerosene biprop runs:
250 psi regulated
0.080 peroxide, 0.018 kerosene
perfect light, dead smooth thrust on both monoprop and
This was absolutely gorgeous the exhaust was as steady as
a welding torch, with lots of mach diamonds.
we set up for a 60 second burn, but the engine began acting
a little strange right off the bat, with the exhaust plume wavering a bit and
changing character a little each time it was relit.
We put the kerosene solenoid batter on the charger, thinking
it might not be opening the solenoid fully.
Still acting a little strange, some leaks evident
March 9 Engine Tests
We found that the catalyst pack that had been acting strange
was actually cracked at the flange, and severely warped. The chamber with the water jacket isnt
distorting at all, but it looks like the biprop runs are cooking the cat pack
flange quite a bit. We should probably
make a stainless cat pack holder before we try any more long duration biprop
We got the first test sheet of our new plated foam catalyst
for testing. This is supposedly a
better grade of foam than our previous material, and has been annealed after
the plating, which is supposed to make is a lot more resistant to stripping the
silver off. We had the entire process
done by Porous Metal Products, at about $200 / square foot, which was much more
expensive than when we just had the foam plated at a local plating shop. That is still a lot cheaper than buying
screens from McMaster, but more expensive than buying screens from Haver.
We pulled one of the 1/2" throat attitude engines off
the lander, and built a new pack for it.
We made two other changes from our previous packs: we used one of our new water jet cut perforated
stainless retaining plates to replace the previous mild steel perforated plates
that were severely bending, and we used the spiral retaining rings for
The initial pack had 24 foam discs. These runs were mostly at 600 psi, which is
the pressure we need to run the lander at for liftoff with a person.
0.120 peroxide jet
large ball valve
400 psi ullage
600 ml peroxide
60 pounds thrust
mildly rough, about what we saw when the old foam packs were
running well. The annealed foam doesnt
seem to light of quite as instantly as our older foam.
85 pounds thrust
We had been so used to testing the tiny little motors
recently that we had forgotten to bolt down the test stand, and this run shoved
the test stand back a foot or two.
78 pounds, slightly wet, slightly rougher
Pack seems to be degrading.
We opened up the engine, and found that there was still some
stripping of the silver going on with the top two disks.
Added six more foam disks.
72 pounds thrust, very smooth, almost as good as the screen
got rough at end after running smoothly for quite a while
We opened the engine up again, and found that there was some
more stripping, and that the pack had compressed itself another 1/16, which
seems to be the cause of the roughness.
The anti-channel rings had done a great job, the sides of the pack were
pristine. The stainless retaining plate
was also still in perfect shape.
The new packs are certainly lasting better than the old
ones, but it is hard to tell how much of that is due to the annealed plating or
the spiral anti-channel rings. However,
the incremental compression of the foam seems to be the cause of the roughness,
and is fundamental to the nature of the foam.
We discussed two possible options for avoiding the compression:
Alternate foam disks with very coarse 8 mesh stainless
screens, and compress the pack so that the foam is completely fitting between
the screens, with the screens providing all the structural strength.
Alternate foam disks with washers, and compress the pack
until the washers are taking all the load, and the foam is squashed flat on the
outside. This probably wouldnt work at
high pressure, because the foam would just tear through the center. It might work at low pressure.
At this point, we are probably giving up on the foam packs,
at least for our current set of applications.
There is still stripping evident, so they are unlikely to last as long
as we would like, and the roughness from compression problem has not yet had a
The foam might be useful for a low pressure engine, which
would have less of a problem with both stripping and compression, and would
benefit the most from the reduced pressure drop versus screens. One of our vehicle designs may have a large,
low pressure engine (fired only after the rotor lifts the vehicle high in the
atmosphere), so it is still worth thinking about. It would be nice to do an identical, back-to-back test of a
screen pack and a foam pack in the exact same engine (sized for the screen
pack, with spacers added for the foam pack) to quantify the difference. We arent sure if we are stuck with paying
for the complete foam order, or if we can cancel right now after testing the
first article. If we are stuck with it,
we will probably investigate some of the other options. If not, we are going to concentrate on the pure
silver / stainless screen packs.