Last week, SpaceX launched a Dragon rocket to the International Space Station (ISS), delivering supplies and research projects to the orbiting laboratory. Among the experiments onboard is ROSA, a Roll-Out Solar Array made by Deployable Space Systems. ROSA offers a lightweight, compact, and less expensive solar power source that could be used for future communication, weather, and GPS satellites.
Additionally, NASA hopes that the array design proves itself useful to the solar electric propulsion (SEP) endeavor, which uses Hall-effect thrusters to accelerate propellant using an electromagnetic field. SEP could reduce the amount of chemical propellant needed for a long-range mission (to Mars, perhaps) by a factor of ten, which decreases the launch weight and the cost of the vehicle. Of course, for that to work, the added weight of the Hall-effect thrusters and the solar array needed to power it must be less than the weight of the fuel that it replaces, hence the lightweight composite structural materials and the thin, flexible photovoltaic array.
Unlike other space-based solar arrays which unfold accordion-style, ROSA consists of a rigid backbone with attached winglets that roll out and retract like a tape measure. The flexible solar panels unfurl themselves without the need for motors, decreasing cost, weight, and complexity.
According to the mission site, "In general, the solar array rolls up around a spindle to form a compact cylinder for launch. Those solar wings are then deployed via strain energy in rolled booms that form the outer sides of the structure. A lightweight mesh material supports strings of photovoltaic cells that churn out electrical power."
The array itself is less than three kilowatts - not exactly a powerhouse, but the purpose of the experiment is to test the mechanics of the structure under deployment conditions and to measure the impact of constant heating/cooling cycles as the array passes from sun to shade several times each day. Electrical characteristics will be measured under various temperature, sun angle, and shading conditions in order to produce photovoltaic IV curves.
The mission also marks the first reuse of a SpaceX Dragon rocket and the 100th flight initiated from Kennedy Space Center's Complex 39A, the site of many Apollo launches.
Video courtesy of SpaceX
Images courtesy of NASA
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