July 3, 2004 notes
Ready to fly
As far as we know, everything is completely ready for flight
testing on the big vehicle, but we werent able to get our usual lift truck for
testing on Saturday. We did a lot of
other miscellaneous stuff, but we are definitely looking forward to our tests
The shock absorbers for the big vehicle are in ( mc64100-1
). I need to buy a 2mm thread mill so I
can cut nice thick mounting blocks for these in the future, but for this
vehicle I made some plates that capture the jam nut and let us screw the shocks
through a form fitting tube and hard up against the base mount. We need to land pretty straight with these,
but they are only a third the weight of the big wire rope isolators, and they
dont have any spring back on landing.
We anchored a piece of road plate on the concrete so we wont
chew it up any more during hover tests.
We have modified the metal vehicle stands with some side
legs, which we plan on using instead of the messy foam blocks for the first
elevated hanging test, but after that proves out, we will do a ground liftoff
while tethered under the crane. After
that, we will head to the 100 acres for a boosted hop.
We replaced the RTV insulation that caught on fire after the
extended burn last week with furnace cement, which should seal everything off
at any temperatures we can reach. It
isnt clear that we need to go to that length just to avoid a little blowby
past the jet vane shafts, but it shouldnt hurt anything.
We have done significant rework on our test stand hardware
to allow a better large run tank and some other improvements.
We did some tests with the fresh new 7 engine, but the
spreading plate has too much flow for stable operation at full throttle right
now. We did find that the 2 x 900 cpsi
catalyst monoliths were actually somewhat more difficult to start the warmup
process with, supporting our theory that it wont start when the methanol is
able to decompose in the cold pack along with the peroxide. If this theory holds, the pack will get
easier to start after it wears out a little.
For now, it needs the slug-before-cracking procedure. We ran a total of 30 gallons of propellant
through it to see if it would stabilize after it cooked and pressed for a while,
but I was still limited to about half throttle on it to keep it running
smooth. At the low flow rate, the
engine got very hot all the way up through the bottom catalyst section. At full flow rate, it will probably be
cooler until near the bottom. We are
going to swap to a smaller spreading plate as soon as Global Stencil gets their
laser fixed and finishes our order, which fixed the last 5.5 motor right up
after we had problems with the high open area one. We are also going to revisit using ethanol instead of methanol as
the fuel, which may avoid the fuel decomposition in the cold pack issue. We could never get ethanol going with glow
plugs, but now that we have spark ignition it might work.
We did several tests using the Liquox sodium permanganate
instead of solid catalysts in a small test motor. We had some periods of clear running, but it has generally been
rough, and we have only seen 240C chamber temperatures so far. We have several more things to try, but
there are definitely some operational headaches to permanganates.
We started working on the new cabin-at-the-bottom
design. The hatch and hatch reinforcement
are being fabricated, but we went ahead and cut out the reinforcement area from
the cylinder for some test fitting.
This design can actually hold three people in pretty good comfort,
unlike our cone cabin which was really only suitable for the ballasted virtual
passengers required by the X-Prize rules.
The ball is rolling on getting a carbon fiber wound 850
gallon tank, but the lead time is over three months. We had been planning on using the 1600 gallon fiberglass tank,
but after some thought I realized that paying the extra money for the smaller carbon
tank will earn out over the flight test series by allowing us to use a smaller
engine with less catalyst and by consuming less propellant on each test flight.
Neil traveled out to the Southwest Regional Spaceport to do
a site survey for our waivered flight testing.
It looks good, but we are probably going to need to upgrade all of our
transportation equipment so we can move our own nitrogen and vehicle erection