Dec 28 2000 meeting notes
Dec 28 meeting notes:
Location: Norwood Autocraft, plus a stop at Long Range Systems
Next meeting will be Tuesday at LRS if the peroxide shows, Norwoods if it
Consolidated Freight picked our peroxide up from X-L on Tuesday, so it should be
here any day now. Really. We hope.
The shipping method is worth a mention: we are getting a five gallon
container of 98%, but it is shipped in a 55 gallon drum. Another empty
five gallon container is included to keep it from falling over, and an inch of
water with a lot of stabilizers is poured into the bottom of the drum, so if
there is a leak internally, it will become highly stabilized.
I have been unable to find a reasonable size commercial space that fits our
needs. I may start looking at building something, but an interim plan I am
considering is to find a local chemical company that would be willing to store a
55 gallon drum of peroxide for us, and let us just pick up a gallon or two at a
time as we need it.
Phil has our flight waiver at the FAA for the dumb rocket.
Phil has all the needed launch site info for the insurance company, but needs to
get it to them, then I need to get them a check.
Phil needs to place an order for our launch rail and base.
The silver screens still havent shown up.
We still need to have some of the new metal foam silver plated and sintered.
We should get the exact process parameters from the plating shop this time.
Neil and Phil brought the dumb rocket components tonight, and everything fits
together fine. It is being assembled with a 98mm engine mount, so we can
test it with conventional HPR motors, then install our peroxide motor with an
We hope to launch it on an L-600 (roughly what the peroxide motor should be)
with the tank loaded with water and functional electronics at Shoot For The
Stars next month, if it doesnt get rained out for the fourth time.
My wife had her graphic artist create some Armadillo Aerospace artwork, and we
will get some of it transferred to mylar adhesive for the rocket. Did we
settle on a white paint job?
Depending on when the flight computer arrives, I will either have a dumb GPS
telemetry relay for it, or we will run the full flight computer with multiple
sensors and blinking lights to test actuation.
I think I found the flight computer I want: http://www.winsystems.com/products/sbcs/lbcplus.htm
It is a bit overkill, but it has
four serial ports built in, and the video and ethernet will let me do normal
software development on it just like any other computer.
I am waiting to hear back from them with a quote for everything I need.
I made large changes to the VTVL simulator last week, primarily to validate the
canted engine roll control and tolerance of variability in engine placement and
efficiency. It works surprisingly well. If you run it in full manual
mode (which is basically unusable), you can see the cross coupling between roll
and the other axis, but with the computer doing the angle seeking, It Just
Works. This is very good news four fixed engines gives full three
axis attitude control.
I am officially changing my axis naming for the simulator so that roll is
the conventional rocketry use (around the axis of primary thrust), instead of
having it be yaw as it is in my games.
We test-fitted things on the VTVL platform tonight, and found that some things
The top crossbar and engine mounting tabs are perfect, but the engine canting
tabs are an inch or two too short. We could still use them by swiveling
the engine mounts a bit to the side, but we are having new pieces cut anyway,
because the solenoid mounting holes were also off. We left the solenoids
and tank with Bob to test fit.
We are still waiting on the two sticks of thin tubing for the tank mount and
We moved the electronics platform from under the crossbar to above it.
This means the electronics will need separate crash protection, but it allows
the bottle bars to be welded directly to the crossbar, and save seven inches or
so of leg height.
We had originally planned on having the distribution manifold on top of the
crossbar, but things work out a lot more symmetrically with it directly
connected under the bottle. Unfortunately, that means that the four hoses
we made are now too short.
With the engines under the crossbar instead of add the bar ends, we need more 90
The solenoids require a check valve between them and the bottle to use vacuum
loading, which complicates the bottle to manifold connection. Phil and I
fitted everything together to put the fill port ahead of a check valve ahead of
the distribution manifold, but it is a pretty ungainly mess. It may
actually be better to use a check valve per engine, which would let us put the
fill port on one of the extra manifold ports, and save eight inches or so of
Russ needs to tap his bottle manifold out to quarter NPT from 1/8. It
isnt critical for the VTVL, but we will need the flow in the dumb rocket.
If we are going to use Russs manifold instead of the NOS one (and the
arguments are good for it), we should look into adding blow off valves somewhere
else in our plumbing.
I just ordering 30 of 3 teflon hose, 8 1/8 to 3 90 degree fittings, 4
straight 3 hose ands, and 4 45 degree 3 hose ends.
Stuff to do over the next couple meetings:
Finish the VTVL and dumb rocket assembly.
I will bring two laptops and radios next week and demonstrate how the real
flight telemetry system will work.
Assemble and test battery packs for the VTVL vehicle. We should get
several identical packs made, so we can do back to back testing in one sitting
without worrying about recharging or running out. We should test them with
all four solenoids hooked up and running a high duty cycle to make sure they
wont run out too fast. I am getting an unregulated 12v to regulated 5v
power supply for the flight computer, so hopefully everything we need to run can
work off of one of the two voltages.
Experiment with the big automotive fuel injectors. We should take a look
at the spray pattern and see how much pressure they can open under. They
wont flow enough for our current uses, but they might be a good optimization
point for other projects.
If we have peroxide, this is the test plan I propose:
Russ: make sure we have plenty of nitrogen!
Continue with 100ml test runs on the small engine until we really have it sorted
out. The existing cycle of a 100 msec pulse followed by a 300 msec delay,
then full on for ten seconds (which will exhaust everything) should also be
followed until we are reliable, then we can experiment with PWM duty cycles.
Use 85ml of 98% peroxide and 15ml of distilled water (I will bring a jug next
week), which will give us 83% concentration. There still seems to be some
debate about the maximum concentration usable with silver catalysts, with some
sources citing 85% and others citing 90%. If we get good reusability out
of our catalysts at this level, we can increase the concentration to 90%.
Michael at X-L cautions that diluting the 98% takes a fair amount of mixing, and
that it will generate a bit of heat.
Start off with 200 psi pressure and the .040 jet. If it works reliably,
increase the pressure to 450 psi and possibly larger jets.
We currently have all of our decent silver foam packed into the small engine,
but there was already some erosion on some of the discs. If we get
degrading performance with subsequent runs, we are probably still either washing
the silver off or poisoning it.
We should try a pack of the pure silver screens when they arrive. That
will lay rest to the washing vs poisoning argument. If we are poisoning,
we should get some nitric acid so we can experiment with cleaning the pack after
We need to experiment with better injector plates. If nothing else, I want
to block off the central holes in the current plate. Just putting a dime
behind the plate should be a step in the right direction. Darin: email
around the specs you got from the laser cutting shop.
We can test Juans motor, but we will run through our peroxide pretty quickly
with it. 500ml should be enough to get a look at it.