May 6 and 10 meeting notes
A whole lot of miscellaneous notes:
We are talking to Yet Another Parachute Vendor for the full
size vehicle: Strong Parachutes. They
are already working on parachutes for Starchaser, so the odds of them getting
cold feet on us are probably slim. We
are hopeful about getting a main canopy for helicopter drop tests of a full
size vehicle by July.
We have continued some alternate propellant engine tests
with 50% peroxide and the XCOR igniter, but we havent had any success to speak
of yet. We did manage to foul the spark
plug in the igniter once, and overheat it a bit so that one solder joint
melted, but the problems were easily fixed.
We have little doubt that a 70% peroxide / kerosene biprop would light
up easily with our current setup, but the 50% peroxide mixes cease combustion
when the igniter torch goes out.
We have one more direction to pursue before giving up on the
50% mixtures: peroxide / methanol with
a pre-heated platinum catalyst. This
has some interesting possibilities, because methanol burns catalytically in
contact with hot platinum (a significant aspect of how glow fuel based engines
work, and it also functions with propane in catalytic heaters), and hot
platinum is also a good catalyst for peroxide decomposition. I will be testing some catalysts from
Catalytic Products International www.cpilink.com
, which may also turn out useful even if we stick with 90% peroxide. One thing that this will force us to look at
is catalyst pre-heaters, because platinum is a much poorer catalyst than silver
at room temperature. Even silver packs
could probably benefit from pre-heating, which would likely make startup much
more consistent. We are experimenting
with some heating elements and temperature sensors for this.
We hope to have some 70% peroxide for tests soon, and our
efforts to secure additional 90% peroxide seem to be looking up a little.
In support of our alternate propellant work, I just bought
the rather expensive "Handbook of Reactive Chemical Hazards." A
Acetone and hydrogen peroxide readily form
explosive dimeric and trimeric cyclic peroxides, particularly during
evaporation of the mixture. Many explosions have occurred during work-up
of peroxide reactions run in acetone as solvent ... A general warning against
using acetone as a solvent for peroxide oxidations is given.
Furfuryl alcohol ignites in contact with 85% peroxide within 1 s.
Detonability limits of
mixtures with 2-propanol have been measured. Approximately stoichiometric
combinations of 50% hydrogen peroxide and the alcohol could be made to
detonate, as could a wider range of mixtures with higher test peroxide.
It is worth noting that the entire book seems to be basically
a collection of empirical observations and anecdotes from the last fifty years,
which isnt really as rigorous as I was hoping for. The accuracy may be a bit questionable as well we testing
furfuryl alcohol with 90% peroxide, and it doesnt self ignite at all. Perhaps the case of ignition involves
combinations of additives or stabilizers in the two chemicals that were not
present in our samples.
Neil has been busy doing meetings with government officials regarding
launch licensing and operations.
Joseph has been laying the foundation for our new peroxide storage
facility and test stand support building.
We have been doing some final work on the sub-scale vehicle,
so as soon as we get more 90% peroxide, we should be ready to fly.
The flaky damaged Esteem wireless bridge has been replaced with
a brand new unit, which we have mounted vertically so it can stay in the
factory shielded case.
The entire electronics bulkhead has been mounted on a
vibration isolating ring which is side bolted into the tube, instead of sliding
the electronics bulkhead down over studs coming from angle brackets bolted to
the side of the tube. It is likely that
the damaged Esteem was the only thing really being effected by vibration, but
we decided to proactively attack vibration and shock for the future. We had originally intended to use four
bonded rubber isolator mounts in place of the mounting studs, but the stamped
angle brackets werent really square enough to provide a good base, and we were
finding we needed more points of support around the outer ring anyway. I milled a complete 24 OD ring out of ½
thick aluminum, and we bonded a ½ wide strip of fairly soft foam rubber on top
of it. Because we use nutserts on the
inside of the tube to retain the bolts that hold the nose cone to the body, I
had to add cutout pockets to the ring to allow it to slide by them. I made equidistant pockets on the mill, but
it turned out that we had just sort of eyeballed the nutsert placement on the
tube, so we had to do some last minute hacking to make it fit. The honeycomb electronics bulkhead was
sanded and bonded directly to the foam rubber with RTV. We sanded 1/8 off the outer diameter of the
bulkhead, so it now has a nice multi-axial vibration mount when inside the tube. This may lose some bandwidth from the
inertial sensors, but most of the isolation should be well above 100hz.
We did a drag test on our Kevlar drogue chute to see how
much load the vehicle would see at burnout deployment, and how fast it would
need to be going to deploy the main chute.
We had a hanging scale hooked up to the parachute cable, but getting a
good deployment was trickier than we expected.
We first tried just tossing it out the back of Phils suburban, but the
base drag was so high that we couldnt get it to inflate at all. We then tried out the sun roof, which didnt
work much better. Finally, we rigged up
a pulley on the end of a six foot wooden beam, and stuck that out the sun roof,
which worked fine. The chute produces
about 35 pounds of drag at 50 mph (22 m/s).
In theory, a deployment at 200 mph would give 16x, or 560 pounds of drag
on our release latches.
We hung the small vehicle from the hoist, and hung weight
from the parachute release chain underneath it. The releases worked fine at a terminal velocity (weight of the
vehicle) test, and nothing broke when we hung 900 pounds from it, but the latch
bodies did bend a bit. We will probably
have to build some stronger releases when we want to fly this vehicle with a
large propellant load.
Matt is finally done with his heavy work load, so we have
some pictures of work from Saturday:
(those are our empty peroxide drums that we just had sent back from our storage
warehouse, since we no longer have anything to actually store there)