October 1 and 5, 2002 Meeting Notes
The original tube vehicle that we put together has been
completely scrapped without ever flying, we are only using a few sections of it
in the new vehicle. We werent
confident that the small side firing attitude engines would have sufficient
control authority, and we felt the fins were almost certainly going to break
off on landing.
The new design uses one of the low pressure (250 psi) 24
diameter Structural tank as a part of the airframe, and has 30 degree
half-angle cones for the base and nose.
This is going to be very draggy, but it should be stable and
robust. The propulsion system is almost
exactly like the landers, with four down firing attitude engines near the
inside corners of the tail cone, and a large central engine. At only 250 psi, that will only be about 500
pounds of lift from the system, and the vehicle will weigh about 300 pounds
ready to fly, so it wont accelerate very hard, but it should be able to fly
for quite a while. We intend to test
four large, differentially throttled engines with this platform, which will
move the thrust to weight ratio back up to something more rocket-like.
The rocket tower drawn parachute system is almost done, but
we are still waiting on some supplies to make a separate little parachute for
the tower, which will fly completely away from the vehicle with the parachute
free bag. In theory, the parachute
should deploy fast enough to be useful in as little as a hundred feet or so.
Russ found that even our new TIG welder struggles quite a
bit welding ¼ thick aluminum plate and tubes together.
We are directly bonding filament wound tube and cone
sections to the fiberglass tank, which seems to be working out very
nicely. The parachute loads are going to
be fed to the tank through straps, rather than through the airframe, so the
bonds shouldnt be stressed very much
Big Biprop Test Facilities
We finished assembling and water testing our high flow, dual
regulated pressurization system that will be used for the 1000lbf biprop. We built manifolding to be able to gang
together multiple nitrogen bottles, but it turns out that a single fresh bottle
can flow enough to expel our desired amount of peroxide at 250 psi with minimal
pressure drop. The big Tescom
regulators flow a LOT more than the welding regulators we have been using. Adding a check valve did let the pressure
drop during the second test, but that may have been due to the lower supply
pressure. We will probably tax this
system when we run the 5k monoprop motor, but well see what it does. I am still looking for official data on the
SCFM flow rates of standard nitrogen bottle valves at various pressures.
We finished the dual motor controller board that we will use
to run the valves at the test site, giving us proper on/off control of both
peroxide and kerosene valves. We had
been using our old testing system that was designed around solenoids for too
long, and the inability to remotely close the valves had forced us to always
let the tests run to depletion. A relay
board probably would be appropriate, but we just ganged two batteries together
to get enough voltage to run over 250 of cable.
We had a visit from a pair of fire inspectors on Saturday
night. They were cordial enough, and we
showed them everything we are working on, including the video of the flight on
Saturday. They didnt seem alarmed at
our work facility, and the only thing they mentioned was that we should have
our nitrogen bottles chained (done), and that we needed a welding permit to
have welders on site (we had no idea about that, but will get one next week).
This was a little peculiar, because they said they had a
complaint registered on the first, a day when we werent doing anything but
construction work, and they knew to come by on Saturday night to find us. There may be some other business around that
has people working late that we arent aware of, or someone that has seen us
for a while got distressed at the sight of the tube vehicle being mocked up,
which does look rather more like a missile than our landers.
This is only historically related to our work, but Chris
Hanson asked if I would be willing to host a video that he put together nine
years ago from the public test flight of the DC-X. The DC-X was long before my interest in rocketry, but it was
certainly an influence on the directions we have been pursuing, and several of
the principles from the DC-X team have expressed their support of our work.