December 2 - 15, 2001 Notes
The new vehicle, all set:
We were all set for a series of flights that was intended to
end with our first manned liftoff today.
The vehicle was ready, the computers were ready, we had plenty of
peroxide and plenty of nitrogen, we had ballast measured, the ambulance was
standing by and
The engines started running cloudy.
At first we thought it was because it was cold and
drizzling, but two of the attitude engines did completely clear up, while two
stayed far too cloudy to fly with. We
vented all the peroxide out of one of the clear engines, and by the time it was
done, it was starting to cloud up as well.
In our rush of progress on the vehicle systems, we never did
really solve our catalyst pack wear problems.
We only get about 120 seconds of fire time on a fresh pack before the
engines start clouding up that is usually three flight days with two or three
flights each. Now that we are flying
larger and larger vehicles, it is only going to get worse. We need to address this. An old reference book referred to pack
lifetimes in HOURS for some engines.
We are just about out of our current batch of plated foam,
so we are going to get a new batch made with a different process. Our very first couple sheets of foam were
plated so thick that the foam was crunchy, and broke off in little pieces
when bent. That seemed to last very
well in our original tiny 20 pound motors, but other factors, like total pack
depth, and high pack compression, may also have played a part. The big batch of foam was plated thinner, and
seemed to have worse wear characteristics from the start. We have also been told that we should have
the plated silver sintered onto the foam before use, but we will just be
guessing on parameters.
If foam plated thicker and sintered works out, that will be
great, because we wont have to change our engines. If we have to go to a silver screen based pack, we are going to
have to make brand new engines, because screens require about twice the pack
depth of the foam packs. They also take
about four times as long to warm up (Mark Henry said that his specially plated screen
packs warm instantly, but Juan Lozanos screen packs and our pure silver screen
packs are significantly slower) and weigh several times as much (not that the
weight is an issue
). Long life is
probably the most important thing for us, although really long warmup times
might be a bit of a problem if a person is sitting on the vehicle.
We built a proper pure silver screen catalyst pack for one
of our test engines tonight. We used
our hydraulic press to push our cutter through about 14 layers of screen at a
time, which worked out very nicely. We
compressed 52 silver screens into the area normally occupied by about 23 of our
compressed foam discs. When we test
fired the engine, we were appalled to see liquid peroxide gush right out of the
engine on the warmup pulse. This was
right after water testing everything, so it was a cold, damp pack, but still
had stopped doing warmup pulses altogether on the foam packs. It made 30 pounds of thrust, but even after
multiple warmup pulses, it never ran clear.
We believe that we need twice the pack depth with the pure silver
We are going to make a quick test motor with twice the pack
depth to see if we can get stable performance out of a pure screen pack, then
we will run it for a couple minutes and see how it ages.
We have a bunch of other miscellaneous stuff going on as
The laptop remote piloting program has been modified to show
a realtime graph of tank pressure, which we are now using as a fuel gauge for
flight it changes the entire background color when it goes below a warning
level, which is visible even in your peripheral vision. We are now using exact, specific amounts of
peroxide and pressure for the flights to make this repeatable. The initial decay of pressure as the tank
cools after filling is a bit of an issue, but we are putting the warning at a
We should be spinning a pair of little engines on a shaft within
a couple weeks. I got a couple 1800 rpm
rotary seals from www.rotherm.com for the
shaft. They arent very peroxide
compatible, but they will be downstream of the valve, so we are going to see
how they do.
We are looking at using an airboat prop from http://www.airboatprops.com/ for our
first lifting tests. It wont be
optimized for high speed, but they can be configured for over 2000 pounds of
static lift. A rocket driven prop will
give us about a 6x lift multiplier at liftoff the props deliver up to four
pounds of lift per shaft horsepower, and a tip engine generates about 1.5 shaft
horsepower per pound of thrust. The
lift multiplier goes down as speed increases, going negative into pure drag at
some point around mach one.
We are buying a bar of TZM alloy molybdenum to make some
test nozzles for our hybrid engines.
This maintains good strength over 3000 deg F, but it needs an oxidation
protection layer. I had been hoping to
use ruthenium, which is cheaper and high melting than platinum, but I have been
told that it is difficult to get a pinhole free ruthenium plating, so we may
wind up with platinum plating.
I finally got the LCD panel working with our flight
computer, but the digital signal is touchy enough that I couldnt put an
extension between the panel and the computer.
The next generation electronics box will probably have the panel mounted
directly on it. I also ran into a
similar signal extension problem trying to run a USB joystick through our
normal CPC connectors two feet of unshielded, untwisted wire seems to be too
crappy even for low bandwidth USB devices.
Our one-watt 802.11b systems should be here soon.
I am looking at possibly buying this laser altimeter: http://www.laseroptronix.com/flyg/altm400.html There are a couple radar altimeters I am
also looking at, but they are more expensive.
I am very excited about getting a fast altimeter integrated with our
systems, because then we will be able to get good auto-hover and auto-land
running. I am probably going to
implement that in the simulator soon.
We are preparing to do some test composite fabrication. We are going to try making bulkheads for our
2 filament wound tubing, and see if they can hold enough pressure to act as a
pressurized cabin or a propellant tank for the rotary pumped engines. We are going to just use city water pressure
to hydrotest them to 50 psi or so.