Three free-flying spheres are currently zooming around inside the International Space Station. Is the crew of Expedition 18 using them to hone their light-saber battle skills a la Luke Skywalker or sharpen their ability to detect UFOs? No, these bowling-ball sized spherical satellites are part of an experiment devised by students at the Massachusetts Institute of Technology (MIT) to test autonomous rendezvous and docking maneuvers for future formation flying spacecraft. Called SPHERES – which stands for Synchronized Position Hold, Engage, Reorient, Experimental Satellites — these color-coded robots are flying inside the ISS, testing different flight formations. But these have to be a lot of fun to play with during off hours on the space station: zero-g bowling or space volleyball, anyone?
And smaller, multiple satellite missions are economical and provide redundancy. Instead of launching one big, heavy satellite, launching lots of little is easier. They can orbit Earth in tandem, each doing their own small part of the overall mission. If a solar flare zaps one satellite—no problem. The rest can close ranks and carry on. Launch costs are reduced, too, because tiny satellites can hitch a ride inside larger payloads, getting to space almost free of charge.
The SPHERES can also test the ability to build spaceships in orbit. One way to build a larger ship to go to, for instance, Mars, is to assemble it piece by piece in Earth orbit. The SPHERES are helping engineers design software that could be used to maneuver the pieces of a spaceship together.