Raspberry Pi used as flight computer aboard black-sky balloon A Brit amateur balloonist has pulled off two major achievements: getting his hands on a wallet-sized Raspberry Pi computer and then sending it heavenwards to 39,994m (131,200ft). Over the weekend, Dave Akerman's PIE1 payload was carried aloft into the stratosphere under a latex meteorological balloon, sending back live webcam …
I may be a bit "off" on this, but why has Dave fitted a heatsink to the Ethernet controller (just behind the USB ports), and not to the main CPU/GPU (SoC) in the middle?
I wouldn't have thought the Ethernet would be used at 39,000m, but surely the CPU would?
Cool achievement overall, though :-)
The ethernet circuitry is housed in the same chip as the USB stuff on the Pi. The webcam was USB, so the chip was in use, even if the ethernet wasn't plugged in. Interestingly on heat scans of the Pi when it's running the hottest part of the board is the ethernet/USB chip, not the CPU/RAM stack in the middle. Dave did his homework!
PS. Please can we call them Pydrogen balloons now?
Generally, no. I've flown other payloads before with a couple of cameras in them, and they can get quite warm.
Also, after the thing lands, the outside warms up (though not that much in our "summer"!) and the inside can get very warm indeed till recovered. As mentioned in my blog I was hoping to use switching regulators but they didn't arrive in time, so when I opened the payload the linear regulator was very, very warm!
could anyone explain, whether this was tethered? Surely not, I can't imagine a 40 km long piece of string. How much would it weigh?
and then, yes, hypothetically, if not attached, what happens when it pops? I mean, think of the children, for God's sake.
Worse still, imagine one of our Masters, moving briskly between the limo and the door of the conference hall. Short distance, brisk pace, wide grin, but still... I dread to think of the mess on the street...
Not so silly - it's what we need to teach kids to do more of.
With what seems like man+dog launching stratospheric balloons (James May ????) I've vaguely wondered about this too. ISTR talk that you need to watchout for pylons
Regarding the descent, the only thing I can think of is that statistically, it's so unlikely a falling weather balloon will hit someone, it's regarded as acceptable. However, that said, a few years ago, we (Dad & I) found a weather balloon plus payload tangled up in a tree at his garage yard, in Hounslow - and I would not want that hitting me on the head. ISTR it had a little inventory tag asking nicely to call the Met Office, who came and collected it. It did have a rather Heath Robinson appearance, and was spray painted silver.
Even without a parachute, the drag created by a burst weather balloon is fairly considerable. I expect that for the weight of payload that it can lift, packed into something without any sharp corners, the risk of causing serious injury is negligible even if it does land on someone's head at terminal velocity.
The odds of hitting someone with an object dropped randomly on the earth's surface are very small. There are probably more meteorites dropping to earth every year than there are weather balloons, and even a small lump of nickel-iron at terminal velocity could do serious injury or worse.
Er, no, not tethered. 40km of nylon is going to weigh (rough guess) 40kg and the balloon had about 600g of free lift available.
As mentioned in the article we use flight prediction software so we know roughly where it's going, and if that means in or close to a large populated area or airport for example then we wait for another day. We can also change the flight path a little (e.g. increasing the ascent rate by adding more gas).
All flights in the UK have to carry parachutes, for obvious reasons.
Further "well" (relating to Lester's linked article) is that a balloon wouldn't "pop up" on an aircraft - its ascent rate (at that height) would mean it would be in the FOV of the aircraft for some time.
Regardless, at the speeds the aircraft is traveling, it's more likely the balloon would be pushed around the craft (best case), or it hits the balloon (ruptures, little damage to plane, bearing in mind the hydrogen won't burn at that altitude) or in the very absolute worse case it gets sucked into the engine. It's for this infinitesimally tiny probability that a plane generally tends to have at least two engines.
We were doing that in the early 1980s.
Much more fun, in the late 1960s we were drifting fused aluminum-foil draped oxy-acetylene balloons over Moffett Field when the weather conditions were right ... Watching the Phantom jets scramble was a hoot ;-)
The balloon "boom" wasn't quite as nice as the sonic boom of the Phantoms ...
Presumably the lightest possible batteries that pack enough charge for the duration of the flight. I'd guess non-rechargeable Lithium cells. Obviously one would check that the voltage and current needed are maintained at low temperatures (or weight-budget for enough thermal insulation to prevent them getting too cold).
6 AA Lithium Energizers into a linear regulator, then that was connected to 0V and 5V test points on the Pi.
I left the on-board 3.3V in place for this flight, but for next time it and the external regulator will both be replaced by switched-mode versions.
The webcam powered from the USB port, but I shorted out the USB thermal fuse on the board. Webcam current peaks at about 250mA and the fuse is rated at 140mA. The 5V to the webcam drops quite considerably with the fuse in place. In tests I could take low-res photos OK but it all locked up when trying to take hires photos.
"..Doubtless this will renew efforts by inflammable gas experts to convince us to use hydrogen for our Low Orbit Helium Assisted Navigator (LOHAN) mission, but we're sticking with cigarette-friendly helium, thanks very much..."
Would there be ANYTHING which would convince you to use hydrogen?
Truly stunning ... I'm impressed.
Wait, not at the ballon altitude or the assembling of the various perpipherals. Frankly lofting a camera to 143,000 feet is not that much of an achievement compared to actually gettign hold of a Rapsberry Pi. It's the stuff of legends .. there are people who claim to know people who have seen one, but, when these leads are followed up, they turn out to be dead ends. Rarer than olympic guards and dodo eggs, the RaspberryPi is the stuff of dreams.
I'll get my coat, its the one with an Arduino in the pocket.
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