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by Staff Writers
Bethesda MD (SPX) Mar 01, 2013
In late January, Dextre, the Canada's robotic "handyman" on the International Space Station (ISS), made space history by successfully refueling a mock satellite attached to the exterior of the station. This was the key task in the experimental Robotic Refueling Mission (RRM). NASA and the Canadian Space Agency (CSA) collaborated to demonstrate robotic servicing and refueling of satellites in space in order to extend useful lifetimes.
For RRM, NASA's Goddard Space Flight Center designed a module simulating a satellite, as well as custom power tools for Dextre. RRM operations began in 2011, with Dextre performing three series of tests related to satellite servicing. In this latest test, Dextre removed two safety caps, cut through two sets of thin retaining wires and finally transferred a small quantity of liquid ethanol into the test module.
Handling liquids in space presents some very tricky challenges and requires perfect precision to prevent dangerous leaks. Specialized tools built for this mission permitted Dextre to seal the liquid transfer connections to eliminate the possibility of leaks. It took the combined skills of experienced NASA and CSA robotics controllers to successfully demonstrate space refueling without any mishap.
There are roughly 1100 active satellites in near-Earth orbits, many of which cost hundreds of millions of dollars to build and launch. Thus, the ability to service such vehicles and extend lifetimes appears to be very valuable. While the idea of refueling and servicing satellites is not new, RRM has demonstrated a significant step in pioneering the needed robotic technologies and techniques.
About 12 years ago, Orbital Recovery Corporation proposed a life extension system for use on geostationary satellites. The plan was to develop an orbital space tug, called the Orbital Life Extension Vehicle (OLEV), whose purpose was to mechanically mate with an existing GEO communications satellite and take over north/south and east/west stationkeeping, as well as attitude control.
OLEV was to be a secondary payload on an Ariane V launch vehicle that would take it to a geostationary transfer orbit (GTO). A Hall Effect Thruster (HET) would then execute the maneuver to take OLEV to GEO, followed by a rendezvous and docking with a satellite that is low on propellant. In this case there would be no fuel transfer, only a simple mating with a three-axis stabilized spacecraft.
About two years ago, Intelsat General and Canada's MacDonald, Dettwiler and Associates Ltd. (MDA) proposed a GEO refueling service. In this case MDA would provide Intelsat on-orbit servicing to the company's communications satellites.
Intelsat was to serve as an anchor tenant for the Canadian company's Space Infrastructure Servicing (SIS) initiative. The concept was studied for about a year, but the idea was finally scrapped due to a lack of commitment from the U.S. government and other prospective government and commercial customers.
Satellite servicing is clearly needed in order to reduce the costs of space operations.
It is simply a matter of time before satellite are designed and built to be serviced and refueled. Most of the needed incentives and technical elements are now available. The last remaining ingredient is an entrepreneur who can pull the technology together with a solid business plan and an anchor customer.
All about the robots on Earth and beyond!
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