Anyone out there involved in High Altitude Ballooning (HAB) operations might be interested in the space-grade Polyimide Thermofoil flexible heater rig we're using to keep our Vulture 2 spaceplane's rocket motor toasty at altitude.
The propellant doesn't much like the cold, so we need to keep it above -5 degrees C if possible - the minimum guaranteed firing temperature.
The last snap is the heater sealed onto our Ceasaroni 54mm 3G case with heatshrink, and the no-expense-spared $10 aquarium thermostat is to prevent the heater from melting down at altitude, where its mighty 2.24W output can't dissipate.
While the heater is only capable of raising the casing temperature 5 degs C above ambient on the ground, it's a completely different story in the air, or the lack of it.
A recent test flight confirmed the rig works as expected, and will keep the motor nice and warm. There are full details here.
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This is such an interesting thread, thanks chaps.
I know we aren't talking about high enough altitudes here, but what happens with the EKF/DCM solution when gravity is partially missing? I am betting it's one of those "not tested yet" scenarios :)
Thanks Monroe. I reciprocate the sentiments and look forward to writing something about the Condor soon.
Our airframe is rated to well over Mach 1, according to the designers. That's at altitude, obviously, since it's not a good idea to try that at ground level. It's a strong beast, nonetheless. There are some photos of the unassembled bits and pieces here: http://reg.cx/28zB
All excellent stuff. We're liaising with Andrew Tridgell on the Pixhawk, and I'd love to get your experience as we move forward. Good to hear your in the Pi club - I'm just about to connect a new dedicated transmitter and GPS board, the "Pi in the Sky". Details soon.
We've tried PBN. Hot stuff. We've actually got three brews on the go (classified info - I'll let you know personally when we've done the last test), so we'll see what works best.
Ardupilot Space Program duly joined, and with great pleasure. I feel you and the Stateside members of the group may be able to lend us a hand, since we're having a few issues here in Spain.
Also, I'll try and give the team and your spaceplane a heads-up on the Register as soon as I get some spare time to do it justice. It's our kind of mission.
@John and Monroe: Again, thanks for all the input. Yup, we know about igniters. We've got our own brew which has done the job at altitude and low temps in our own hypobaric chamber. We're just waiting on the results of the last airborne test, which should settle the matter once and for all.
You don't even need a current limiter. If you swap the heat-pcb out with some heat/resistance wire and match the total resistance of wire to the voltage you are going to use, you have a closed system not requiring any electronics.
For example is you have 12v and need 15W of heat, then just find the right heat-wire and cut the length that gives a resistance of 12/15=1.25ohm. Add a matched thermistor and you can even have a self adjusting system.
Thanks, Monroe - all sound advice.
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