Jun 5, 2001 Meeting Notes
Full carbon NGV tanks
30 silver plated foam sheets
Polyethylene bearing stock for hybrid grains
2 Serial port DC motor drives from National Control Devices
10 3 amp solid state relays
More distilled water
Ratchet set for LRS
Another motorized ball valve
Fiber optic gyros (any day now
Chassis mount connectors for new electronics box
Aviation record book from http://www.naa-usa.org/website/
If our vehicles are acceptable, we should collect some
time-to-climb records next year.
We are all settled on the design for the manned vehicle, and
Bob will have it tacked together next week for final check. It is probably going to wind up weighing
about 120lb dry, with thick steel tubes.
Bob got a couple carbon fiber NGV tanks from a local source
for us to look at. They are almost half
the mass of the hoop-wrapped aluminum tank we were previously considering. These are 3600 psi operating pressure tanks,
so they are vast overkill for us, but at 35 pounds, the tank is only going to
be about 1/3 the dry mass of the vehicle, and far less with the pilot, so the
extra margin will be just fine.
We are going with detachable legs for transportation. The total beam length will be around 11,
with the attitude engines out at the very ends. We should be able to detach the legs and strap them to the tank,
so we dont have do unhook any of the plumbing or electronics. We are going to have two cubic feet of foam
under each beam extension for landing / floatation.
The plumbing design is to have the main lifting engine and
all the distribution plumbing directly under the tank, with the pilots back
against the tank, standing on a platform between beams. There will be an aluminum splash shield
between the pilot and the main line plumbing.
We will start with this eight gallon tank, but we can more than double
the capacity with longer tanks without touching the vehicle at all.
The pilot will be offsetting the CG at a distance of about
one foot from the center. The
electronics box will be put at the far opposite side of the vehicle to provide
some counterbalance, and we will be starting off by adding ballast to
completely statically balance the vehicle with the pilot. There will be greater than a five to one
leverage advantage, so adding 20 pounds of ballast with the electronics box
should be close. After seeing how much
attitude control authority we have, we may allow the vehicle to fly with an
offset CG and skip the ballast.
It is worthwhile to note that if we had gone with the two
tank, pilot-in-the-center design, we would have a heavier dry mass than by just
adding ballast (more capacity, though).
We will initially hop the vehicle just on the attitude
control engines as a direct up scale of the current demonstrator, then we will
add the central lifting engine.
Depending on how our motor development has gone, we may fly it unmanned with
Juans motor drilled out to 150 lb thrust before moving to our 600 lb thrust
The next generation vehicle will probably have a very fat
tank, with the pilots seat supine above it for high Gs. That will be the first vehicle that we will
design to actually have a decent dry mass.
The simulator, flight computer, and remote pilot are all
ready to test three new things as soon as we get the new electronics box built:
Discrete control as we are currently doing it, but with the
Continuous control, which should be possible with the low
latency of the FOGs.
Active roll control with canted engines.
I have been trying again to buy some silver and platinum
metal foam from:
I finally got a return email, but it was just to fill out an
inquiry questionnaire, and no response since.
My designated customer service representative wasnt at her desk today.
I sent an inquiry email to http://www.ultramet.com/
about advanced chamber materials, but I havent gotten a response. They make small thrust chambers out of
iridium/rhenium with optional carbon / carbon backing. I suspect the prices are exorbitant, but it
would be very nice to do biprop work without worrying about melting your chamber.
I contacted my local FAA Flight Standards District Office to
see what the FAA thinks about manned rocket powered vehicles. I was pleasantly surprised to get a response
the very next morning, but unfortunately it was a notification that the request
had been forwarded to the Washington office.
I traded email with the president of the Dallas area EAA
chapter to see if there are any locals interested in giving us a pilots
perspective on where we are going, and possibly give some advice for dealing with
Tim Nolan is just about finished with an ultrasound range
finder for us to try as a landing assist.
Motorized Valve Control
The KZCO ½ motorized ball valve seems to work pretty well,
so I have ordering a second one for our master cutoff valve.
I did some logging of position and actuation times, and
found that it gets up to its full speed very rapidly (about 50 msec), but that
after power is removed, it will coast through over 20% of its travel time
I had it set up to follow the joystick throttle, but even
with a generous dead band, it would coast out of it and reverse itself
The normal way to brake a motor is to short its leads
together, but I couldnt do that with the control setup I had. I tried adding a resistor across the motor
leads to slow it down faster. It made a
nice little puff of smoke. :-)
Eventually in experimenting with reversing the motor for
braking, I managed to burn out one or more of the solid state relays I was
driving it with.
I found out that the proper way to drive motors is with an H
bridge, which allows forward, reverse, and brake to be easily applied. I ordered a couple pre-packaged motor
drivers to work with this week.
Pick up five more gallons of peroxide.
Refill nitrogen bottles
Finish the PC104 SSR driver board
I hope to have the new electronics box done this weekend,
assuming the FOGs get here.
Check with the local foam suppliers (who does LRS use?) for large blocks of closed cell foam.