NASA’s free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES) have been flying aboard the International Space Station since 2003. Powered by AA batteries, the satellites act as free-flying platforms that can accommodate various mounting features and mechanisms in order to test and examine the physical or mechanical properties of materials in microgravity.
Each satellite is an 18-sided polyhedron and is roughly the size of a soccer ball. The Department of Defense (DOD) SPHERES-Rings investigation is the first demonstration of electromagnetic formation flight in microgravity, as well as of wireless power transfer in space. The study installs highly advanced rings to existing SPHERES. The crew places the rings around an individual satellite, consisting of resonant coils, coil housing with fans, batteries and support structure hardware. The Rings project demonstrates the use of electromagnetic coils to maneuver individual SPHERES with respect to one another. The current running through the ring of coils controls the satellites, so that two ring-outfitted SPHERES are able to attract, repel, and rotate.
“Using electrically generated forces and torques is preferable to using fuel, since electricity can be generated by solar panels, but once fuel is expended, the mission is generally over,” explained Kathleen Riesing, a graduate student with the MIT Space Systems Laboratory.
Research goals for SPHERES-Rings include enhanced attitude control performance between separate satellites and the possibility of more efficient power transfer at a distance. Adding an efficient way to transfer power between SPHERES may alleviate the need for alternate power sources. The wireless power transfer experiment establishes the hardware necessary for potential future powering of space and urban robotics and enhanced communications systems in space, on land, or underwater.