DIY high altitude balloon launch

DIY high altitude balloon launch

I had the opportunity to organize a high altitude balloon launch for the Pueblo City-County Library District. It's a great activity for age groups ranging from high school up through university ages. It also caught the interest of the community at large. The project was broken up into three main phases: Building the payload, launch, and retrieval.

Building the Payload

When I was working as the Technology Trainer at the library, I led a weekly Maker Club. It's a great open-format time to share ideas and projects and also to introduce new tech and programs at the library. After reading about a dozen balloon launch reports, I pulled together and ordered the necessary supplies. Basically, the payload was a foam cooler with a window in the side for a GoPro camera. The inside had space for a heater, a GPS tracker, and some Arduino controllers to record data from an altimeter and thermometer.

 The inside layout of our balloon craft

The inside layout of our balloon craft

 3D printed camera holder, glued and taped into side of foam cooler.

3D printed camera holder, glued and taped into side of foam cooler.

The holder for the camera was a part that I designed in Tinkercad and 3D printed. In the end, this saved time and let us really secure the camera into the side of the foam box. I'm actually really glad we did it that way because the foam walls of the cooler are really brittle on their own, especially if you start cutting holes in them. Important: do not use 'Goop' to glue foam ~ it will make it melt! The best glue seems to be 'Liquid Nails' construction adhesive, spread thinly. Duct tape is also an excellent option. 'Gorilla Tape' is some amazing stuff; probably worthy an entire journal entry. 

Beyond the payload, which must meet certain FAA weight/size restrictions, there are some other considerations. I opted to go for a 1200g latex sounding balloon. These things cost about $30 and are amazing in that they start out at about 7ft in diameter on the ground, but expand to 30ft+ at altitude! Most balloon experiments rely on the balloon swelling to the point that it breaks in order to bring it down. In the event that it doesn't, the FAA rules require that a balloon craft has a cut-down device. This is anything that either pops the balloon or cuts it free of the payload. I built a small line cutter with a piece of nichrome heater wire. Electrifying the wire heats it up, melting through the nylon rope, releasing the balloon and letting the payload fall. Once the craft is downward bound, it needs a parachute to slow the descent. I bought a neat little 3 foot parachute from a hobby supply store. The whole craft is strung together and parts are secured with tape on the day of launch. 

It took about 2 months at our weekly meetings to physically assemble everything. I wish I had paid more attention to charging/replacing batteries the night before. As it was, it was a mad scramble in the morning to find a charger and new batteries etc etc. Just be meticulous and make lists and it will all turn out ok. In the end we spent a grand total of $680, including the GoPro camera and stand alone GPS tracking unit. 
 

Launch Day

We launched from the most remote of the library branches, out in the Greenhorn valley. The reason was that we had to put space between us and the Pueblo airport. I also had to call in a NOTAM notice to the air traffic controller, letting him know when and where we would be letting it go. 

We had a great turnout of people, especially considering it was a Sunday morning and the library wasn't even open! I had plenty of needed help with the inflating stage, as the balloon becomes very ungainly once partly full. Also, it's actually surprisingly hard to deal with somthing that is inversely-heavy. (Aggressively light?) 

We started the camera, the heaters to keep batteries from freezing, activated the data recorders and set the GPS transponder. At that point, we just duct taped it all up, walked it out into a field, and released it with much cheering and fanfare! There was also a group of onlookers watching a live Skype broadcast of the launch from the main library branch back in Pueblo. We all counted down together. A wonderful time was had by all!

 The balloon craft drifts away into the springtime Colorado sky. We had a fix on it at this point, able to follow it from our phones via the cloud app.

The balloon craft drifts away into the springtime Colorado sky. We had a fix on it at this point, able to follow it from our phones via the cloud app.

Retrieval

I thought I had planned for everything. I even found a balloon-prediction website set up by NOAA. Immediately after we let it go, the chase team mobalized. We were a motley crew of eight in an SUV, a minivan, and an old Honda. The van went northeast, according to the prediction. I went with the SUV and Honda to the east, but soon notice the location points beginning to drift off course. Suddenly, just two hours after launch, the GPS signal went dead... It turned out that the SPOT trace GPS unit has an operational ceiling of just 30,000 ft. An oversight. We drove and waited, checked, and waited. In the end, we went back to Pueblo, broken hearted.

 That night, at around 8PM, the signal returned to the map, this time over eighty miles to the west and on the other side of the Great Sand Dunes! It had apparently found a jet stream and been deposited in a field in Hooper, Colorado. (Hooper is known for its giant round fields, its UFO lookout station, and not much else... nobody was manning the station when our balloon came down.)

The next day, I provisioned my car, recruited a good friend, and headed for Hooper. It was actually pretty silly how easy it was to find. I had a dot on a map on my phone. I drove to the dot. Here's what I found:

 Balloon on the ground in Hooper, CO.

Balloon on the ground in Hooper, CO.

I recommend balloon launches as a good way of engaging public or students in an activity related to science & engineering. We had several weeks of activity in the planning stages, a full morning of setup and launch, and a full evening chasing it.

 A frame grabbed from the GoPro video from an altitude of around 50,000 feet.

A frame grabbed from the GoPro video from an altitude of around 50,000 feet.

Once the craft was retrieved, we downloaded the footage and it was just spectacular! It couldn't have gone better. A final edit of the film can be seen embedded below. We set it to classical music performed by Pueblo's Veronika String Quartet. Enjoy and feel free to share. 

 

Additional information about this project

Link to the final report: https://drive.google.com/open?id=0B20Tn1-412L7dXFYS3RDYkNwa0U

Link to a bunch of pictures and project media on a google drive: https://goo.gl/8GdnQY

 

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