To keep everything from getting jumbled around, Hackerspace built a lightweight frame to mount the cameras. We put a handwarmer in the center-- the same kind you’d put in your ski boots to keep your toes warm on the slopes. We estimated the temperature at 100,000 feet to be about -60 degrees Fahrenheit, and cold temperatures can kill battery life. To keep the cameras rolling as long as possible, we needed to keep them warm. Another potential problem: lack of oxygen. Hand warmers need it to create the chemical reaction that creates heat. But at 60,000 feet, the amount of oxygen is so low, the reaction basically stops. We hoped that the residual heat that built up inside the lunchbox would be enough to keep the battery life as long as possible.