November 04, 2013
Credit: Photo: NASA
NASA astronaut Mike Hopkins started a series of on-orbit tests Monday that could lead to large “sparse arrays” of satellites in space maintaining their relative position using electromagnetic fields generated by superconducting coils.
Working with engineering graduate students from the Massachusetts Institute of Technology and the University of Maryland, Hopkins set up two soccer-ball-size “satellites” inside the Japanese Experiment Module (JEM) on the International Space Station and plugged them into 75-cm electromagnetic rings delivered to the station in August on the H-II Transfer Vehicle.
Guided by Allison Porter, a Ph.D candidate at Maryland who helped build the Resonant Inductive Near-field Generation System (Rings) as a master’s degree project, Hopkins put the test satellites through their paces in the first of three test series that will run until next March. After he positioned them floating in the station’s microgravity environment, the satellite/ring combinations moved eerily toward and away from each other as the coils followed pre-programmed power configurations.
Meanwhile, the Synchronized Position Hold Engage and Reorient (Spheres) satellites used their carbon-dioxide thrusters to counteract any torque set up by the electromagnetic fields. Students monitoring the test on a large video-screen maintained a running discussion of what they were seeing, relaying suggestions and adjustments to Hopkins through Porter in real time to accommodate the results. They were guided by Alvar Saenz-Otero, the Spheres lead scientist at MIT.
The experiment hardware is designed to validate technology for electromagnetic formation flying (EMFF) with multiple spacecraft, which would enable large-array space telescopes for astronomy and Earth observation. While the tests inside the station using aluminum wire at room temperature allow the coils to influence each other at distances measured in centimeters, in open space using superconducting coils spacecraft can be controlled at ranges of 70-100 meters, according to Ray Sedwick, an associate professor of aerospace engineering at Maryland who is principal investigator on the Rings experiment.
The coils can also transfer power across open space via resonant inductive coupling. During a break in the experiment setup Monday, Sedwick said the technique, already demonstrated in a checkout session on the ISS, could lead to constellations with primary spacecraft supplying power to a swarm of smaller and simpler satellites held in formation by EMFF.
The back and forth between Hopkins and Porter illustrated the value of two-way conversation between researchers on the ground and the station crewmembers carrying out their experiments. The setup required Hopkins to juggle settings on the two Spheres mini-satellites, the two Rings surrounding them, the laptop programs running the tests and the infrared and ultrasound beacons in the JEM that collected data and sent it down via NASA payload links. At one point Saenz-Otero asked to be “enabled” to speak directly to Hopkins, so he could expedite a Spheres procedure outside the training Hopkins and Porter had received. On another occasion Saenz-Otero asked the students if Hopkins would be able to disconnect a ring and replace a CO2 cartridge in its Spheres spacecraft.
“I don’t know how hard it is to do in space, because I’ve never been there, but we’ve done it on the ground,” said Drew Hilton, an MIT student.