Location: Long Range Systems
Next meeting at Norwood Autocraft, unless notified.
I was at the Space Frontier Conference last week, and did a
few things related to the project.
I got to meet a couple of the ERPS guys, but circumstances
conspired to prevent any substantive discussion time.
I had a long talk with Jeff Greason of XCOR (ex Rotary
Rocket people), and he shared some thoughts on peroxide. He isn't particularly
fond of it, but he has worked with it and could grudgingly admit that it might
be the right choice for us. He likes biprop motors, but their trick
motors (with electronic ignition) have five times the complexity of our simple
His big piece of advice was just that peroxide lulls you
into a state of complacency, and it is all too easy to get casual with it when
you need to stay alert. He had seen people go from full PVC suits to
walking around with an open jug in one hand without even safety glasses.
He had also seen someone almost lose their eyebrows when an open container went
He also convinced me that a blow off valve really isn't much
of a safety benefit. With rocket concentrations, there isn't any such
thing as decomposition slow enough for a blow off valve to help. If
anything in the tank catalytically decomposes from a tiny impurity, it will set
the whole thing off with thermal decomposition.
The big win at the conference was talking to the JPA people
and finding out that one of their sponsors (http://www.magnetometer.com) makes
EXACTLY the part we need for our attitude sensor! I am getting a sample
soon, and JPA has already made an A/D board and bench tested it, so that removes
a major uncertainty from our plans. I will write up some GUI software for
it to share back with them.
I didn't have much to bring to the meeting this week, but
Phil and Russ had been busy.
We have found the perfect cart for the fill system, but it
We have a 12vdc vacuum pump for the fill system.
We had the nickel metallic foam plated with silver, and Russ
finished our first experimental engine.
I brought our now neatly organized collection of fittings,
and left them with Russ and Phil. We have already run out of -4 female /
Darin has some output from the accelerometer, but it needs
The big news is that we fired our own engine tonight!
It wasn't a very scientific test, because we were only committing
to doing the peroxide compatibility testing, but we decided to go ahead with
the firing. We didn't have the load cell on, so we don't have real data,
but we generated some good impressions.
We had three small jars of distilled peroxide, with less
than a pint in each. We don't know the exact concentration, but it is
probably in the 80% range.
We had two pairs of gloves and goggles, so the two other
people stood away and checked procedures.
We had the test stand on the other side of a solid concrete
wall, and we watched it through a mirror we pulled off the bathroom wall.
We hooked everything up and ran a load of water through
without any hitches in our procedure. Hopefully this is the last week
where we are hooking and unhooking the fill station, we should have the
integrated cart soon.
First we just loaded up a bit of peroxide and let it sit in
the tank while we watched for any pressure increases. We could hear some
bubbling, but it settled down and we didn't get any pressure rise.
We should drip some peroxide directly on the big O-ring in
the bottle neck and make sure it is viton instead of rubber.
During the first fill, we had one minor incident. We
disconnected the vacuum line from the pump, intending to put it into an empty
water jug in case someone opened the wrong valve, but vacuum started leaking
out. All of these valves and solenoids are directional, and this one has
to be oriented to prevent nitrogen pressure from flowing out to the vacuum
pump. Our plan is to have a catch tank always connected to the vacuum pump, but
we might want to add another check valve on the vacuum side. A big lesson
that has been repeated many times is that we need more check valves than we
expected. For the tests, we just left the vacuum line connected to the
When we fired it, it coughed and spit for a second or two
with a plume of uncatalyzed peroxide, then made a bit of a roar just before it
ran out and vented all the gas. We had a long foaming puddle behind
When we drew the vacuum again, we got a bit of smoke and
smell from the vacuum pump's muffler as it digested some peroxide drops left in
the fill system. This is almost certainly not a good thing, another
reason why we need our catch tank in line.
We loaded the remaining 2/3 of our peroxide in and set up
for another run. This time, we pulsed the launch valve open and closed to
pre-heat the catalyst pack before dumping everything out. It was very
different this time. The heating pulse was only a quarter second or so, but
the exhaust was clear before it was over. When we opened the launch valve
the second time, it was absolutely perfect. It roared for three seconds
or so with a completely invisible exhaust plume.
We were quite surprised. The first run was about how we
were expecting things to go, based on our readings of the literature.
Seeing the awesomely clean second run was unexpected. We knew we had a
lot of water left in the system before the first firing, but the difference was
striking. We will need to do more tests to see if the high quality second
run was just due to not having any water in the system, or if the residual heat
from the first run was a primary factor. There was nearly ten minutes
between the firings, but I'm sure the motor was still warm.
This plated metallic foam catalyst seems to be a Very Good
Thing. Bob had given us a roll that had been used by a rocket dragster
many years ago, but a funny coincidence occurred as we were getting it silver
plated. Russ and Phil ran into a guy that had samples of the same stuff
in his briefcase, and it turns out we have a lot of options to experiment and
pursue in this direction. They were also given some information about
baking the silver plating onto the foam if we had trouble with it coming off.
The catalyst pack was made by hand cutting disks of the foam
and stacking them until it was about four inches high. The pack was
inserted into the engine by hand, without any compression, unlike silver screen
packs. Five cm is usually quoted as a good catalyst depth, so we expected
it to be more than sufficiently catalyzed. The pack still flowed easily
enough to blow through. We might try just rolling up the foam for a pack
instead of cutting disks.
We ran a full load of water through after the last firing,
then disassembled and washed everything.
I am a little concerned that the launch valve we are using
may not even be able to flow 100lb of thrust. The engine we ran today was
a good bit larger than the one Juan rated at 100lb thrust, but it still took
two or three seconds (I wish we had been logging!) to blow out only a couple
pints of peroxide, which is well below that thrust level. We have a
higher flowing valve, but it is a momentary solenoid, which means we would need
a flight battery and that it would close when power runs out, which is not
good. We may need to find a larger latching valve before flying the dumb
Phil got a little peroxide itch when he moved the vacuum
pump, because he accidentally grabbed the suction point that had been whetted
on the second fill. It washed off fine. This corroborates the
opinion that you only get peroxide on you after you think you are done and have
taken off your gear.
When we pulled the motor apart, we found that the nozzle
side catalyst retaining plate had cracked during the firing. We need to
experiment with different materials and hole patterns.
The foam discs hold a pretty fair amount of liquid in them,
so an incautious person picking up an engine after a peroxide firing could dump
a lot out.
After we finished with the motor, we parted out all the
plumbing and solenoids we will need to assemble the first VTVL platform.
If we share the tank with the dumb rocket, it should come in under $1000.
Russ is going to make a small engine in the 10lb thrust
range, representative of what we will use in the VTVL platform.
I really, really need to start bringing the camera.
I need to get us a cheap laptop we can leave with the fill
stand, so I don't have to remember to bring mine all the time.
Russ wants to turn a custom bottle fitting so we can dump
the heavy NOS manifold at the bottle. That will also improve our flow
rate for the big motors somewhat, but I think the launch valve is still the
We need to do several instrumented full tank runs on the
stand with the bigger engines to make sure we are going to launch the dumb
rocket fast enough to be stable.
Our biggest unknown now is how well pulse width modulation
will work on the small engines.
We need a good peroxide source to start doing serious engine
development and testing. I would really prefer that we not distill any
We are supposed to be able to get unstabilized 70% peroxide
from a local source, but there may be a lead time. That would be down on
Isp, but if we can still fully catalyze it, I certainly don't have a problem
using it. Lower chamber temperatures won't hurt.
FMC is going to be here on Thursday to tell us what we need
to do to our site to get a drum of 90% from them delivered.
Russ knows exactly what we need to drive the solenoids from
a microcontroller. I am ordering more solenoids for the VTVL platform, so
we should be able to test PWM soon.
We have appointed Neil (in his absence
) to build the flight
rocket. I would like to launch it next month at Windom on a certified
motor to test stability with a tank loaded with water before we run it on a
Tripoli experimental launches apparently won't allow liquid
engines, so we are going to have to get our own launch insurance. I am
bumping the priority of creating a corporate entity for this purpose. We
need a name pretty soon.