![]() ![]() "It represents physics pretty well," Easley said. Credit: NASA's Goddard Space Flight Center A gravity offset table at NASA’s Goddard Space Flight Center being used to simulate contact dynamics of a grapple operation. A gravity offset table allows NASA to test how a robot arm would interact with a satellite in space, which is mimicked by the payload on top of the sled. Reach too far and the servicer could push the satellite away don't reach far enough, and the servicer could miss the satellite. This is no easy feat since the client satellite was not designed to be grappled, and this operation must be fully autonomous. The technology demonstration mission will utilize a servicing spacecraft with two robotic arms that must match speed with and grapple a client satellite to refuel it. Simulating a space-like environment is critical to OSAM-1 testing. This technique helps ensure that our complex simulations are accurate and realistic. It was and continues to be used for testing elements of the On-orbit Servicing, Assembly, and Manufacturing 1 (OSAM-1) mission, which will robotically refuel a satellite in space. NASA Goddard has been using this gravity offset technique for developing satellite servicing technologies since receiving its first gravity offset table in early 2017. The new gravity offset table arrives and is installed at NASA’s Goddard Space Flight Center. It comes very close to zero-gravity-so close that you could push the payload with your finger, and it would glide away from you, just as it would in space. The gravity offset table has three degrees of freedom. To reach true zero-gravity, the table would need to simulate six degrees of freedom or directions in which objects can move. In our system, it's more like the puck, with the mass of a satellite, floats itself." "For air hockey, a table perforated with jets of air floats a puck. "It's basically like an air hockey table in reverse," said Joe Easley, robot operator group lead at NASA's Exploration and In-Space Services Division at NASA Goddard. Three air bearings under the sled output a thin layer of air from a pressurized source allowing items to "float," which simulates how a payload moves in space. Measuring 8 feet by 10 feet and weighing 8.5 tons, the slab is polished precisely then leveled. It would be interesting if somebody could dig through records and interview people and find out what really killed the centrifuge.A gravity offset table is a large piece of granite used for testing space payloads in simulated zero-gravity conditions. Yeah, it was killed for cost reasons, but they were covering for an ally. She said that they were never able to get a straight answer out of NASA, but that there was a general belief that the Japanese, who were building the centrifuge, were having major technical problems, such as isolating it from the station. Why not simply state "we couldn't afford it" and leave it at that? So I asked one of my colleagues, who was very familiar with life and microgravity research issues on ISS. Many people still think that.) Anyway, the ISS official was really cagey about the whole thing. (The reason is that from a scientific point of view, the centrifuge was very high priority and many people thought that without it the scientific value of ISS was zero. However, back around 2005 or 2006 I was in a meeting where a senior ISS official was pressed on this issue by some scientists. Officially it got canceled due to "cost overruns." On a slightly different note, it might be interesting for an enterprising grad student to research the history of NASA's centrifuge and what really happened to it.
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