July 25, 2004 update
Moving to the 48 tank initially looked like bolt the
flanges to the new tank and we are almost done, but because we also moved the
motor drives, reworked all the jet vane actuators, and built a brand new wiring
harness with shielded cables, it has taken a bit longer than expected.
We got the new interface cone bonded onto the 48 tank, and
the cutouts made for the vacuum line and all the cables. The top cone was 1/8 aluminum, and weighed
50 pounds. We added a cross brace and
lifting point, which allows us to just barely stand the vehicle up inside under
our hoists if the shocks arent on the feet.
On our next vehicle revision, we are going to arrange to mount all the
electronics around the base of the
vehicle, and use a fountain tube from the bottom to draw vacuum in the
tank. With those changes, we really
will be able to literally bolt different tanks on without changing anything,
and we wont need a ladder to turn the electronics on and attach the vacuum
We are beginning the design of a custom board that will
replace all the connectors, terminal strips, and random wiring on our
electronics system. That should
increase reliability, save space, and allow us to rapidly put together extra
systems for crash replacement or redundancy.
We are using shielded cables with solder-shield termination for
everything, and using metal shell connectors with the proper contact directions
for all new connectors. It is a trivial
little thing, but I had always wondered why you could get CPC connectors in
both normal and reverse sex, and I only just found out the reasoning for it a
couple weeks ago (while reading http://workmanship.nasa.gov
): live power contacts should be sockets instead of pins, so they are harder to
short. Makes sense to me.
Each jet vane actuator is now wrapped in insulation and
enclosed in a stainless steel sheet metal enclosure. We are going to avoid burning off residual propellant while on
the ground (dumping it to a holding drum instead), which is how we melted our
last set of actuators, but with a 120 second flight we will probably see
significantly higher heating.
We have started putting together the A-frame that we will
use for erecting the vehicle in the field, so we dont need to have a lift
truck on site, which was going to be a logistics issue at the distant launch
We are renting the lift on Tuesday, so we expect to be hover
testing by the end of the day. If that
goes well and the weather doesnt give out, we will do a boosted hop next