Solar Eclipse High Altitude Balloon, part 2


If there’s one piece of advice I could give to anyone looking to launch a high altitude balloon, it’s this: don’t pick a date and try to prepare for it; instead, get everything prepared and then pick a date. The former is a recipe for disaster; you’ll start cutting corners and leaving things unprepared and unchecked. In my case, I didn’t even think of the idea until the eclipse was a month away, and I couldn’t really reschedule.

On the plus side, I had the pleasure of working with some fantastic people at the Boulder Hacker Space, Solid State Depot, and I’m confident that the project would not have succeeded without their help.

Overall, it’s important that you do everything you can to keep your launch safe and prevent it from interfering with or presenting dangers other people. Launching a balloon presents a risk to other aircraft and to people on the ground. The FAA has stated that they think this risk is acceptable because of the scientific value that balloon launches can provide.  In our case, we were doing this for fun and and to learn, but there was little scientific value otherwise, so be mindful and polite and do everything you can to reduce risk.


As this was a group project, we tried to meet often in person. We also kept documentation on our wiki, which I highly recommend. It was useful any time we had some documentation we wanted to keep or share, and it’s easy and quick to edit. We kept track of ideas for the payload, experiments, testing results, and a launch checklist.

The process

There are a whole lot of things you need to do to launch a balloon:

  1. Pick a launch site
  2. Prepare the payload: recording, sensors, tracking, electronics, case, parachute
  3. Prepare ground tracking equipment
  4. Test everything
  5. Prepare lifting gas and launch setup
  6. Notify the FAA
  7. Launch!

All of these steps ended up being more complicated than I had realized. I’ll try to go through each one with a different post. First up, picking a launch site.

Picking a launch site

Before anything else, you should consider where to launch from. If you only want get views of the curvature of Earth or just some nice aerial views, then your launch site can be pretty flexible. In our case, we wanted to capture the eclipse and view it for as long as possible, so there was a pretty narrow band of land that we wanted to launch from. We looked at a map of the eclipse in Wyoming and decided to launch from there.

The FAA has some requirements for anyone launching a balloon that further restrict launch sites: you’re not allowed to launch your balloon over populated or congested areas (for the first 1000 feet of launch), you’re not allowed to pass through class A-E airspace (near an airport), you can’t operate at any altitude if there’s more than five-tenths cloud coverage, and you’re not allowed to operate your balloon in a hazardous manner. That last one is ambiguous, but you should avoid highways at the least.

For viewing restricted airspace, SkyVector is a fantastic resource. The FAA also has a map tool named Know Before You Fly aimed at drone operators, and you should avoid any restricted places that it lists.

You should also consider how to recover the balloon after it lands. Wyoming has large amounts of state and federally owned land which you are allowed to walk on, which makes recovery convenient. If you do land on private property, you will need to contact the landowner to get permission to recover your balloon. Note that landowners are not required to give you access, nor are they required to recover and provide you the payload, but they also can’t claim ownership of it. It gets into a weird legal limbo that is best avoided if possible. There are several hunting apps for your phone that show which land is public or private that can aid in recovery. Some will even list the owners’ names, so you can start to contact them if you need to.

Once you have a general sense of where you want to launch, you can start running predictions of your balloon’s flight path using several online tools. This will give you a good idea of how your balloon will travel with the jet stream at different heights and where the balloon will land. Two tools that I like are HabHub’s CUSF predictor and The University of Southampton’s ASTRA predictor. Note that HabHub’s launch time is in UTC, while ASTRA’s is local. Both sites require you to enter some details about your payload – you won’t know the details yet, but an ascent rate of 5 m/s, descent rate of 5 m/s, and burst height of 30,000m are good defaults. ASTRA gives more control over your parameters, but at this stage, I would recommend using the parameters we launched with: 1.1kg, payload, Rocketman 3 ft. parachute, 2.3kg neck lift, helium, standard weather data, and standard flight type.

You have two choices for launch gas: helium and hydrogen. Helium is a nonrenewable resource and costs more than hydrogen, but unlike hydrogen, it’s not explosive. You will need a gas regulator for either one. For helium, you can use carbon dioxide regulators, which are commonly used in kegs, so you might be able to borrow one. I’d recommend using helium for your first launch because it’s safer.

In the next part, I’ll talk about the payload – what electronics we selected, tracking mechanisms, the enclosure, testing, and picking a balloon and parachute.

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