Answering Some Pico Balloon Questions

When the US Air Force shot down some suspected Chinese spy balloons a couple of weeks ago, it was widely reported that one of the targets might have been a much more harmless amateur radio craft. The so-called pico balloon K9YO was a helium-inflated Mylar balloon carrying a tiny solar-powered WSPR beacon, and it abruptly disappeared in the same place and time in which the USAF claimed one of their targets. When we covered  the story it garnered a huge number of comments both for and against the balloonists, so perhaps it’s worth returning with the views of a high-altitude-ballooning expert.

[Dave Akerman] has been sending things aloft for a long time now, we think he may have been one of the first to put a Raspberry Pi aloft back in 2012. In his blog post he attempts to answer the frequently asked questions about pico balloons, their legality, whether they should carry a beacon, and what the difference is between these balloons and the latex “weather balloon” type we’re familiar with. It’s worth a read, because not all of us are part of the high-altitude balloon community and thus it’s good to educate oneself.

Meanwhile, you can read our original report here.

29 thoughts on “Answering Some Pico Balloon Questions

  1. FWIW, NASA’s been using Raspberry Pis on balloon payloads for a long while now. Along with a webcam to monitor the LEDs (not kidding). Not sure how long ago they started, but pretty sure it was close to ’12.

      1. If you find out when NASA started flying them let me know as I’d like to follow that up.

        Mine was only a month or so after the first board was delivered, so I’d be surprised if they did it before me!

    1. But I guess I’m wrong, there. I remember weather balloons from way back, that were huge polyester film balloons. But now I see that radiosondes are light enough that relatively small, biodegradable latex balloons are the current technology.

        1. Weather balloons for radiosondes are usually latex. they only need to go up to 100,000 ft or so, then pop. that only takes 90 minutes or so, no worries about leaking helium in that time frame. Even larger radiosondes that also measure ozone use larger latex balloons.

          1. Indeed. There’s an amateur network that tracks met office weather balloons and I’m not aware of any that don’t pop, so unless I’ve missed some then they’re all latex.

            Helium leaking isn’t an issue for any latex weather balloon as their lifetime is so short. Even deliberate amteur latex floaters tend to pop after 24 hours due to UV degradation.

      1. The twice-daily weather balloons are all latex. Up, pop, down. Telemetry is logged on the way up then the balloon’s job is done. There’s an amateur network to track them down to (near) landing, and some amateurs then go out to collect the free hardware!

    2. All the radiosondes I’ve recovered (RS41-SGP’s launched out of my local NWS office) have been under shreds of latex envelope.

      When I toured the office a few years ago, they were in the process of converting from helium to hydrogen as a lift gas, lots of ESD precautions around the launcher. I’ve heard that more recently they’ve installed an automated launcher so there aren’t even people nearby when they go up.

      Of course by the time they come down, all the lift gas is long gone so it doesn’t really matter. I’m only in it for the sondes (free STM32’s that literally fall from the sky!), but I try to clean up the balloon and tether too if I’m able to recover them.

    3. That is precisely what they’re made of, covered in talcum powder to prevent them sticking to things prior to and during launch.
      latex is presumed to be best for purpose due to its bio degradable nature and also its extremely elastic. Weather balloons can grow to more than 10 times their inflated size at the height of their ascent.

      The Vaisala radiosonde which is attached to them is a mostly polystyrene affair (sadly) which is extremely lightweight but obviously Carries some environmental issues. I believe research into bio plastics and cellulose based shells has been going on for a while… perhaps not with a suitable degree of urgency…

  2. You’d be surprised how much you can do with latex weather balloons. When you combine them with some altitude control hardware you can float at any altitude from 50 m to 30+ km for 24+ hours. And if you’re willing to combine a couple balloons then 50+ kg payloads are possible.

    Depending on your application there are good reasons to go with plastic balloons, but latex balloons are often overlooked when they’d work just as well for a fraction of the cost.

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