I am contemplating putting a drone (like a Bixler or Skywalker) on a balloon for launch from a very high altitude and subsequent LONG, APM guided glide back to the starting point. Just for the hell of it (and some cool video)..
Would the typical APM and oilpan hardware have difficulties operating at, say, 60,000 - 100,000 ft that a balloon might reach? I suppose I might need to put a hand-warmer packet inside the airframe to keep things at a reasonable temperature... Also, I assume the barometric altimiter would not be accurate at that altitude.
I would not have the engine kick on until it came back down to 10,000 ft. or so, as there would be no need, and I assume there would be cooling issues in the thin air.
--Dan
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Johnny is right. There are a lot of amateur high-altitude balloon launches being done which are recording GPS data between 60,000-100,000+ ft. The majority of gps modules won't allow it, but there are some out there that will. I came here because I want to do a project exactly like Dan S (OP) describes. I was hoping the Mediatek MT3329 had firmware that would permit reporting above 60k ft, but apparently it does not (based on the spec sheet and this thread.) I thought maybe I could feed the APM GPS data from a different gps module (that will report above 60k ft) but from what I've read it sounds like the APM is listening for a special trimmed-down data stream from a purpose-written firmware on the Mediatek. I'm not a coder so it's all above my pay grade. Anyone have any ideas?
I have taken part in two balloon launches. On one, I built a photography satellite using a box of around 5" x 5" x 5" made of foam board. Once all of the "guts" were installed, foam padding was used to insulate and restrain the contents. A hand warmer can be used, but I think I used a battery with a resistor on it (this was around six years ago so I've forgotten which). This payload survived to around 100,000' and back.
The second launch was an R/C airplane. This was written about in "Design and Flight Testing of a Mars Aircraft Prototype Using Inflatable Wings". I was unable to find it after a short Google search, but there's plenty of information if you look search for "inflatable wings" in combination with "uav", or "Dr. Jamey Jacob". At high altitudes your wing and propeller will probably experience separation due to the very low Reynold's Number. Cooling might be offset by a heat-sink, but then you may have problems with things getting too cold.
As far as GPS is concerned, according to Garmin, the latest news is that GPS units have software limitations that do not allow them to work at altitudes above 60,000' and 1,000 kts (it's either knots or mph). It is a combination of the two that limits the unit. As long as you don't go supersonic you'll have all the GPS positioning you want.
Has anyone tried putting one of the APM-supported GPS units on a weather balloon?
-Johnny
All GPS modules are limited to no more than 60,000 feet for security reasons. See this.
The Navy manned high altitude balloon jumps from the 1950's, 1960, and the russian jumps of the 1970's come to mind as good lessons to consider, for conditions, electronics components behavior (like resisters) at low temperatures, flat spin, terminal velocity issues in near-space and slowing down as the air pressure increases... I think the enclosed space of the GoPro, and the limited time of exposure that results (takes time to lose heat in a sealed, small container, etc) allows people to use them w/o issue, but I wonder what lessons might be learned from the GoPro. Then there is recovery.... things can travel a long way if they are 100,000 feet up... I ran some simulations on FlightGear with some longer flights under AC2.0.2x, and make mistakes. The simulation (quite unrealistically) rose to 118,000 feet to the mid-point of a 45 mile leg before stopping mid-vector to descend to the target 400 feet altitude of the next waypoint. :) It spent a lot of time fighting for position at the 9000, 5000, and 2000 levels where FlightGear provided variations in atmospheric conditions (or whichever altitudes it has variations, numbers are from memory.)
There are a lot of things that might be learned from this, but for several reasons I'm not too hot about losing an APM for the cause :) And I am not confident enough of my engineering to say I could do this without ending up on national TV for killing someone in a mall when my frozen bixler smashes through the skylight. And attendant legal issues. But it is a very interesting engineering problem :)
Dan, i think you will need a little more than one hand warmer in your fuse to keep things warm, also your control surfaces with have very little response in such thin air, do you have a design of the bixler (dropball) that you can show us?
Temps at 60,000 feet are typically -75degs and lipos dont produce power well at cold temps.
keen to see what you attempt.
richie