May 26, 2001 Meeting Notes
Two two-liter flasks
12VDC to 115VAC inverter for remote test stand
-10 AN Teflon hose, hose ends, and fittings for 600lb engine
Four NOS Pro-Race solenoids for manned attitude engines
We did three engine tests today, and then ran two loads of
peroxide in the VTVL.
The first engine test was a proper 3x expansion nozzle for a
half inch throat. Having made almost 40
pounds with a nozzleless engine earlier, we were expecting to see almost 50
pounds of thrust. The run was very
ragged, and didnt make much more power at all. We ran it again, with similar results.
We are assuming that the catalyst pack was messed up when it
was transferred from the old test stand engine (which now has the pressure port
plug cross-threaded) to one of the engines we pulled off the lander for this
The third test was of a quickly machined plug nozzle
(aerospike). This was sort of a throw-away
test, because we know the throat areas arent comparable, so we wouldnt be
able to say anything conclusively about it.
It made less thrust, and was still rough. We have designs for better plug nozzles that we will be testing
We need to do more investigation of this poor performance
today. I suspect channeling around the
pack, which probably wasnt very true after being pulled out of one engine and
pushed into another.
Based on suspicion of moving catalyst packs in and out of
the engines, we made all new catalyst packs for all the VTVL engines instead of
trying to stuff the original one back into the test stand engine when we moved
it back to the VTVL.
Russ took a quick stab at making the microcontroller
modifications to cut some latency out of the gyros, but we didnt have enough time
to work them out, so we went back to the original code for the sensor board.
We tried the first load with the same flight control as was
used on May 15th. It was a
little windy, but not as bad as the last time.
I hopped it up several times, but it couldnt stabilize itself. Using our new graphing software, it was easy
to see that it just didnt have the control authority.
The next load, I changed the flight control parameters so
that the minimum delay between attitude corrections would be lowered to two
instead of three. I expected to see
more overcompensation (although still less than on May 12th, because
of the addition of rate extrapolation), but it would give it about 40% more
I lifted it off and flew it for the entire propellant load
of seven seconds, and it stayed stable even when it drifted sideways enough to
pull one of the tethers taught. Yeah!
The control graph does show reasonably large oscillations,
but it kept it under control.
We probably wont be flying the VTVL again until we are
converted over to the fiber optic gyros, unless the delivery time is several
weeks off, in which case we might go ahead and work on roll control with the
After we get the FOGs and roll control in and tested, we
will be taking off the tethers and flying it around free.
Manned Vehicle Notes
Bob is looking into the local supplier of pure carbon fiber
NGV tanks, but if nothing better turns up, we will probably use Neils tank.
We need to take some peroxide to Bobs shop so we can test
its reactivity on various metals and coatings to be considered for the vehicle.
The primary design options are:
One tank in center, pilot offsets CG. Simplest and strongest, but requires the
most attitude control.
One tank slightly offset from center, balanced CG at
blowdown, when attitude control has least authority.
Two tanks, pilot in center, CG stays balanced throughout
flight, but with a larger polar moment.
Even though we are
intending to start with a standing pilot, this would be the direct path to a
supine pilot / high G vehicle.
With two of the tanks that Neil found, the vehicle would be
too heavy to lift off unmanned with just the attitude jets, so testing couldnt
be quite as incremental. If we get
carbon fiber tanks, it might still be ok.
It would require a significant additional amount of plumbing
to join the tanks at the top and bottom.
I think we are settled on pilot-facing-between-cross members,
rather than pilot-looking-down-cross member, because it lets all the cross members
be fully triangulated up the tank and out to the attitude engines. This joystick orientation will change the
control logic a bit, but I dont expect it to be a problem.
The driving design issue is the attitude control
system. The NOS solenoids are still the
best valves we have found in our pressure / response / materials domain, and
that limits us to about 50 pounds thrust at 400 psi tank pressure with the 8.5
amp solenoids, or 70 pounds with the 30 amp solenoids. If we need more thrust than that, we would
need to either gang multiple solenoids, add more attitude engines, raise our
tank pressure (limited possible gain), or move to slow acting servo valves for
Ideally, the attitude engines would be mounted vertically at
the height of the CG, which would apply all of their thrust as a rotational
torque. If we decide to mount them
completely below the pilot, we could regain the torque be canting them inward,
but they would be less efficient at providing lift, which would be a bit of an
issue if we used pulsing-off instead of pulsing-on for attitude adjustments.
If we have a 200 pound mass six inches from the centerline,
the attitude engines would need to be around eight feet from the centerline to
be able to keep the vehicle from rotating at the lowest engine blow down
pressures, and that wouldnt give much authority for wind. We can help by placing the electronics box (10
pounds) out by the opposite engines, and that could be extended to actually
adding some ballast at the far end. It
would probably be reasonable to completely statically balance the pilot with
less than twenty pounds of ballast added to the electronics box.
We need to be conscious of transportation logistics. A very wide vehicle will probably require
the outer legs to be removed for transportation. What is the maximum dimensions we can fit in our existing
vehicles (Phils Suburban or Neils van)?
How wide could we put something on a custom trailer?
Landing / floatation: foam blocks are working out great on
the demonstrator, but the manned vehicle will be about ten times larger, so it
bears reexamining. A large inner tube
is still a contender.
leaning forward against the tank, or leaning back against the tank? Leaning back against the tank almost makes
the entire vehicle a big rocket pack.
To Do List
Pick up more peroxide from Rinchem. Phil, let me know if you want me to come
over to help, or if you and Russ will take care of it.
Get some more silver plated foam. Phil mentioned getting it done at a level in between the two ones
we have tried, but if it hasnt already been started, I would probably prefer
to stay with the last version we got, and just change other pack variables.
Finish development on 50 pound thrust engines. Russ, you might want to make the converging
angle go deeper so the throat isnt as long, but it probably doesnt matter
much. We might want to investigate
other engine issues, like external threading to make pack insertion easier, designing
for O-rings on both closures, etc. before making all four nozzles.
Investigate pure silver foam for catalyst packs. We may be able to get by with a single layer
of thick silver foam instead of stacks of discs, which would reduce
Investigate using external threads on the motor tubes to
make catalyst insertion easier.
Investigate using an injector plate with lots of small
injector holes, both with and without inert foam spreaders. I would prefer to get this done in an
automated way, rather than doing it by hand in a drill press. We should figure out exactly what plate
diameter and hole diameter we want, and see about getting Darins friend at the
laser jet shop to cur it.
Test 30+ second burn on engines.
Test pack wear conditions.
The only way we are going to be able to do this is if we make a
completely separate engine for it, that will never get cannibalized for
anything else. We should fire it a few
times a week, and just see how it degrades over a couple months.
Aerospike testing. Technically,
they are plug nozzles, not aerospikes. We
need to do an exact, back-to-back test with the same throat area and a chamber
Fiber Optic Gyro integration when they arrive.
Start development on 600 pound thrust engine.
Vertical test stand.
Something good for several thousand pounds of thrust. Neil:
you mentioned before that you knew some people handy with concrete and
construction that we could probably get cheap.
Still an option?
Closed loop servo valve control.
New electronics box.
Basic GPS + accelerometer integration for landing assist.
Move the test stand hardware into one of the small
waterproof electronics boxes, and see if it is possible to run the engine with
a spare serial control line, instead of requiring both a serial cable and a
Roll control on the lander.
Parachute canisters and fins for the ballistic flights of
the lander with the larger engines. I
am thinking something like a PML piston ejection system. I would prefer to investigate cold gas
ejection, but we could do some flights with blackpowder ejection charges.
Drill ball valve vents.
Practice on our galled valve, then drill the servo valve. We need to decide for sure which side is
inlet and which is outlet before doing this.