July 18, 2004 notes
Construction
Lots of miscellaneous work as we rebuild and move to the new
tank diameter.
We pulled the computer and propulsion sections off of the 63”
diameter tank, and moved them to the 48” diameter tank. The old tank and cabin are now just strapped
to a palette off to the side of the shop.
http://media.armadilloaerospace.com/2004_07_18/retired.jpg
We hydrotested the new tank to 530 psi.
http://media.armadilloaerospace.com/2004_07_18/hydrotest.jpg
We straightened the vanes again, and added some bracing,
because the vane plate was warping a bit, either from heating or the hard push
against the out-of-position vanes.:
http://media.armadilloaerospace.com/2004_07_18/vaneBrace.jpg
The existing vanes only bend when we have a failure that turns
them more than 20 degrees under the flow, but we have some Rene-41 alloy plate
and rods from www.hightempmetals.com
coming, which we are going to try making a set of vanes with that should be
pretty indestructible under our conditions.
Depending on the form, Rene-41 is $75 to $100 a pound! I was shocked to see that as twice what the
refractory metals like TZM cost, but it is still easier to form and doesn’t
need an oxidation protection coating.
We built a completely separate box for all the motor drives,
and we are completely electrically isolating it without even connecting the
grounds this time. To do this, the
ignition will be controlled by separate solid state relays, leaving the drive
board and the master cutoff controlling motors exclusively. The complete box weighs 33lb, mostly in the batteries.
http://media.armadilloaerospace.com/2004_07_18/boxOutside.jpg
http://media.armadilloaerospace.com/2004_07_18/boxInside.jpg
Our hatch reinforcement for the cabin-at-the-bottom layout
arrived. Our previous hatch on the
cabin-in-the-cone had a separate lip that the hatch was supposed to fit in, but
at only ¼” thick, it wasn’t deep enough to provide any centering ability with
the gasket spacing the hatch off, so we left it off the new design. The corners were also clipped so we don’t
need to weld on extra bars when we want to externally bolt the hatch closed
instead of internally pressurizing it.
http://media.armadilloaerospace.com/2004_07_18/hatchReinforcement.jpg
We built an actuator framework to control a 4” ball valve
using the strongest KZCO actuator. It
took 24 volts to drive it, but it seems to be able to open and close it
continuously without any problems.
Unfortunately, there is so much backlash in the huge gear train and
mounting play that it isn’t very good at making small flow changes. We will probably use this for test stand
work, and find something better for vehicle engines. This size valve is good for over 30,000 lbf class mixed-monoprop
engines, but our next scaling should go to about 16,000 lbf.
http://media.armadilloaerospace.com/2004_07_18/bigValve.jpg
The plates for the mininozzle experiment arrived. The pictured plate arrangement actually has
slightly more throat area than the large single nozzle. We want to try out this experiment before we
scale to 24” engines, but vehicle flight tests are still top priority.
http://media.armadilloaerospace.com/2004_07_18/nozzleCompare.jpg
The new spreading plates for the 7” test engine should be
here on Monday. Based on my update description,
Terry Wheelock made a cutaway CAD drawing of our 7” engine:
http://media.armadilloaerospace.com/2004_07_18/engineCutaway.jpg
A picture of our prospective launch site at the Southwest
Regional Spaceport from Neil’s scouting trip (not much to damage out there…):
http://media.armadilloaerospace.com/2004_07_18/swrs.jpg
We are pushing to get the new vehicle configuration in the
air next Saturday, but that may be a stretch.
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