মঙ্গলবার, ১৮ অক্টোবর, ২০১১

Satellite Refueling in Orbit, Coming Soon?

A satellite has always been a one-shot deal. Once a satellite enters orbit, it operates either until the equipment fails or until it runs out of propellant and burns up into the atmosphere. Humans have been launching satellites for more than a half-century, and we?ve yet to come up with an effective way to visit them and extend their lives. "Our space infrastructure is an incredibly fragile thing," says Steve Oldham, president of Space Infrastructure Services (SIS) at MacDonald, Detwiler and Associates (MDA). "We all depend on it, and yet we have a throwaway culture in space."

MDA is one of two aerospace companies, the other being ViviSat, who had representatives speak at the recent SATCON satellite industry expo in New York about new projects to change that, by developing in-orbit refuel and repair services to extend the life of currently operating satellites.

Satellites are expected to last a 10 to 15 years without mechanical fault, and most do without a problem: The hardware is still chugging along fine when the satellite runs out of fuel, according to ViviSat COO Brian McGuirk. So these multimillion dollar pieces of technology could keep operating if engineers could find a way to prevent them from tumbling into the atmosphere. "A large number of satellites are de-orbited, are perfectly good, perfectly functioning satellites generating tens of millions of dollars a year in revenue," says Richard DalBello, vice president of Legal and Regulatory Affairs at Intelsat General, the world?s largest commercial satellite operator.

MDA?s solution to this problem: Fill ?er up. The company's SIS satellite servicer would use video recognition technology and a robotic arm to carefully open the craft?s fuel nozzle, insert a hose and replenish the fuel supply (MDA built a robotic arm that's currently on board the International Space Station). Oldham says the servicer?a vehicle in itself?could stay in orbit for about seven years completing refueling missions that take about two to three weeks each. At the moment, he says, the design of the project?s robotic arm includes a "tool belt" that could open about three-quarters of all satellite?s fuel caps.

ViviSat?s servicer is called the Mission Extension Vehicle (MEV). It would carefully dock onto satellites and act as a space-tug, correcting the orbit. Because that?s what you?d do with the satellite once it was refueled, the MEV basically performs the same function as the SIS servicer, but without adding fuel. However, the MEV would stay attached to the satellite for much longer than an SIS. It would take one to five years to gently correct the satellite?s course.

They?re both impressive systems, DalBello says. "The ability to refuel is a very powerful technology," he says, and his company just signed a $280 million contract with MDA. However, he says, the tug system has its own strengths, such as for satellites that can?t steer themselves anymore. "In situations where you might have a control malfunction on the satellite, it might be your only solution," he says. In addition to extending the life of satellites, these fixers could also react to problems the satellites have in orbit. DalBello gives the example of an Intelsat satellite over Africa that had a problem deploying one of its dishes. "That?s a multimillion dollar revenue hit to us," he says. "It might be something that would have required a simple tap to open the dish." That simple tap could have been provided by an SIS servicer.

Although these two support systems would provide the unprecedented ability to keep satellites going, neither provides permanent fixes. Eventually, satellites do wear out or become obsolete, and at that point wouldn?t benefit from additional refueling or course-correction. According to DalBello, Intelsat would look to use SIS on the satellites that are aging the best and extend their lives by two to four years. That?s a small step, but satellite-operating companies are excited about the ability to service their craft, which will probably start in 2015. "We build a satellite, we cross our fingers and we hope for the best, and we completely rely on it," Oldham says. "We totally rely on that network, but strangely we don?t service it?unlike every other network that we use." That?s about to change.

Source: http://www.popularmechanics.com/technology/military/satellites/satellite-refueling-in-orbit-coming-soon?src=rss

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