The final Low Orbit Helium Assisted Navigator (LOHAN) test flight - codenamed PRATCHETT - will take off tomorrow (Saturday) from Colorado Springs East Airport at 13:30 local time (19:30 GMT).
The mission - designed to test our Vulture 2 spaceplane's avionics rig at altitude - is being conducted by our US allies at Edge Research Laboratory. They'll send this payload up to around 30,000m under a mighty meteorological balloon:
The test is a second pop at seeing how our Pixhawk autopilot, servos, batteries, etc, perform in extreme cold at altitude. This time around, however, we've got a 900MHz radio rig on board, by which Andrew Tridgell will monitor the flight live from the comfort of his sofa in Australia. There are more details on that and the payload here.
It should be entertaining, so if you fancy cracking a beer and coming along for the ride, you'll be able to follow the flight live here.
Comments
we've landed, got to over 30km, kept link using RFD900 whole flight. Lost radio link at 200m AGL
we have burst at a bit over 30km, over highway 24
http://uav.tridgell.net/Lohan/EdgeFlight2/
Hi Lester,
I know you do not have any navigation planned for the GPS, but you will get considerable interference from the Pixhawk with them strapped together as they are in the photo. If you can make provision in the container to separate them I'm sure you will find things work better.
Good luck with your flight!
@Eli - For the rudder servos, the foam is far greater insulation than they'll have in the final aircraft. That's not an ideal set-up for the test, I know. Regarding the canard servos, in the aircraft they'e sitting directly under a Raspberry Pi in the forward fuselage. They aren't going to be an issue, since the heat from Pi alone will keep them toasty. With the lack of air, there's nowhere for generated heat to go, so overheating is actually an issue, even at -50 deg C external ambient.
The servos are set to "wiggle" every 30 seconds during the ascent, which we hope will prevent freezing, even for the exposed units.
@John - Yes, the servo current will indicate any major issues we believe. We'e hoping to get a temp sensor on one of them at least. They're rated down to -20 deg C, I believe. We'll see how low they actually get, and if the "wiggle mode" keeps them in operating range.
I will be tuning in- thanks.
Since the question was raised, I assume that servo current is being reported. This will indicate any impact due to lubricant viscosity changes.
Do you have any idea if the thermal properties of your foam box are remotely similar to your final vehicle? May not be an apples-to-apples comparison if you are on the edge of the operating specs for your components.
Hopefully, our monitoring of the servos will tell us if all is well. If they do freeze, they may have thawed by the time the pursuit team gets there, but probably not on touch-down. I'll keep everyone posted on the results as soon as we have them.
Lester, how are you going to know if the servos freeze? Is there some sort of feedback you plan to measure? If they did freeze, would they have thawed by the time the package lands?
Good luck with your own flight.
@Lester,
Thank you for your answer :)
I'm getting ready to release a hyper pressurized floating balloon project ~10gr payload.
And yes, Ultimate Lithium is the only battery for this kind of applications.
Good luck and keep us updated
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