The International Space Station (ISS) is a habitable satellite in low Earth orbit. The ISS depends on solar energy, and during every second of the Earth’s 92-minute orbit, the station’s solar panels must be precisely positioned to safely maximize energy capture. At the same time, energy capture must occur within prescribed limits or else the station and its solar panels will cast uneven shadows on the longerons — the long, thin tethering beams that hold the panels to the station — and cause them to warp and snap due to their high sensitivity to temperature.
The Topcoder community developed a high performance Java-based model of the station to assist competitors in their pursuit of a new solution. By using this model, competitors were able to test their solutions at home in under 15 seconds. Competitors then submitted their code and solutions to Topcoder for automated, online testing. Results were computed in real time during the challenge and posted to a public leaderboard to drive competition.
The goal of the Longeron Challenge was to develop a complex algorithm that would carefully turn motors to reposition the solar collectors on the ISS to generate as much power as possible throughout the station’s most shadow-prone and difficult orbit. During the 3-week system optimization challenge, 4,000 citizen scientists registered for the challenge and 459 competitors submitted over 2,000 submissions vying for a piece of the $30,000 prize pool. NASA received a huge response to the challenge and took the solar array angle input from multiple finishers. The top solution provided an average output similar to what NASA had previously experienced with its own solution. In this case, the fact that the challenge used new motor configurations that did not produce superior results affirmed NASA’s use of its own system, and the contest was deemed a success. The winner was a contestant with no prior experience solving problems related to space or solar capture.