Near-Space Balloon Story

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Pre-Launch

Project Icarus had its humble beginnings with a dream to see what the world looked like from the sky. At first, images were captured using a balloon tethered to the ground with fishing line, but then we dreamed bigger. After some research into high-altitude balloon flights, we were ready to start planning.


A major limitation to our work was the fact that we, being poor college students, had a very limited budget to spend on the electronics. The radio equipment necessary for tracking and retrieval of the balloon/camera was simply too expensive. Fortunately, we discovered that gps-enabled cell phones (and several models of these phones well within our budget-range) can be turned into trackers that would lead us to the balloon.

The next problem we faced was geographical in nature: we live on the coast, and if we launched the balloon from Boston, the prevailing West -> East jetstream would push the balloon into the Atlantic ocean. From previous low-altitude launches, we estimated that the balloon could drift as far as 200 to 300 miles during the course of its flight.

Knowing this flight risk, we planned to launch the balloon somewhere in the vicinity of Albany, NY. We planned to drive half of the distance the night before and finish the rest of the 250 miles on the day of the launch. We camped out in a Target parking lot because we could not afford to spend any money on hotel.

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Hardware

We designed a low cost balloon-launch platform that did not require the use of expensive equipment such as radio modems (the total cost of our device did not exceed 150 dollars) or complicated hardware hacking (all of the components of our device were common electronics available off-the-shelf in stores).


The GPS receiver was a Motorola i290 “Boost Mobile” prepaid phone with internet and GPS capability (set up with Accutracking to constantly report its GPS location).

We bought a AA-battery cell phone charger to sustain the phone’s power over the duration of the flight, and we used Energizer lithium batteries (rated to operate at temperatures are low as -40F) to power both this charger as well as our camera.We bought a AA-battery cell phone charger to sustain the phone’s power over the duration of the flight, and we used Energizer lithium batteries (rated to operate at temperatures are low as -40F) to power both this charger as well as our camera.

As a further safeguard against electronic/battery failure due to low temperature, we utilitzed Coleman disposable hand warmers (placed near our electronics) to help keep our equipment warm in the cold of the stratosphere.

We loaded a Canon A470 camera (bought used on Amazon) with CHDK open source software to enable a feature which allowed the camera to take pictures continuously (intervalometer). Using this feature, we set the camera to take a picture every 5 seconds at a 1/800 second shutter speed. With an 8GB card, the camera was able to chronicle the whole journey of the balloon from launch to retrieval. (~5 hours)

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Equipment Used in the Launch Capsule

Item Approx. Weight Approx. Cost
Sounding Balloon 350g from Kaymont 350g $20
Sounding Balloon Helium N/A $20
Parachute 10g $3*
Motorola i290 Prepaid Cellphone 90g $50**
Styrofoam Beer Cooler 15g $0
Duct Tape 10g $0
Zip Ties 5g $0
Canon A470 with 8GB SD card 165g $40***
Insulation material - newspaper 5g $0
Duracell USB phone charger powered by AA batteries 20g $10
Instant Hand warmer 5g $2****
4 Ultimate Lithium AA batteries 60g $5
Radar Reflector (aluminum foil) 0g $0
Total ~800g ~$150

*Two things: (1) We had one of these laying around, so we’re actually a little unclear about how much it would cost to get a plastic parachute with strings, but we can’t imagine it would be that much. However, we actually created a second launch vehicle using a trash bag as a parachute, so that is one way people could probably cut costs. (2) It may not even be necessary to attach a parachute. For instance, I think that a large number of streamers dangling off the back of the box might provide enough drag to slow it down to a comparable landing speed.

**Some people have told us (and we have confirmed after some searching online) that the cost of the cell phone (usable for a similar launch) can actually go as low as $30. We paid $50 for ours though.

***This was a lucky grab for us. One can do the same with a 4GB SD card with picture intervals of 10s each, and that will save you about $10. You can find cheap cameras on ebay or Amazon (used). You probably want to send a used one up anyways, considering the harsh conditions it will be subject to.

****A packet of 6 handwarmers can be bought for ~$5 from Target. We used two handwarmers for our launch, one pressed against the camera and one pressed against the cell phone.

*****Many people have asked about the antenna in our pictures. It was an extra part from a used wireless router. However, i don’t actually think it’s necessary to have one (and in our second vehicle, we actually didn’t add the antenna.) As long as the cell phone can report its location after landing, one should be okay.

Launch

We launched the balloon from Sturbridge MA at 11:45am on September 2nd, 2009. We concluded from local wind information and Balloon Trajectory Predictor website by University of Wyoming that the winds would be minimal on that day. Because of the limited cellphone coverage in the western parts of Massachusetts, we tried our very best to land the balloon east of Worcester, which is a city in the middle of Massachusetts. We selected the launch site by looking for the first open field after we exited the highway at Sturbridge. That landed us next to a company called Ryders. The vice-president of the company came out and helped us out. He even gave us free floss!

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Landing/Retrieval

The parachute slowed down the fall sufficiently for the capsule to stay together in one piece. The Motorola i290 managed to send out its gps location before landing. Although our the electronics suffered no damage (low impact velocity), the cell phone antenna burrowed into the ground upon landing, preventing further transmission of gps location.

We were also lucky that the capsule landed in a soft-earthed construction field with a clear view of the sky. Retrieval would definitely have been a much more difficult process had our device landed in a lake or in the forest.

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