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Jun 5, 2001 Meeting Notes

Jun 5, 2001 Meeting Notes


In Attendance:


John Carmack

Phil Eaton

Russ Blink

Bob Norwood


New Supplies


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



On Order


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.



Manned Vehicle


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 don’t 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 pilot’s 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 Juan’s motor drilled out to 150 lb thrust before moving to our 600 lb thrust motor.


The next generation vehicle will probably have a very fat tank, with the pilot’s seat supine above it for high G’s.  That will be the first vehicle that we will design to actually have a decent dry mass.



Software Changes


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 FOGs.

Continuous control, which should be possible with the low latency of the FOGs.

Active roll control with canted engines.


Other Contacts


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 wasn’t at her desk today.


I sent an inquiry email to http://www.ultramet.com/ about advanced chamber materials, but I haven’t 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 pilot’s perspective on where we are going, and possibly give some advice for dealing with the FAA.


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 it’s travel time before stopping.


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 constantly.


The normal way to brake a motor is to short its leads together, but I couldn’t 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.



To Do


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.




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