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NASA working on refueling satellites


October 19, 2012

Artist's concept of a servicing satellite (Image: NASA)

Artist's concept of a servicing satellite (Image: NASA)

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Geostationary satellites cost a fortune and, despite their sophistication, they break down or eventually run out of propellant to keep them oriented. This is unfortunate when the nearest garage is back on Earth, so NASA wants to remedy this with an orbital version of roadside service. The space agency is developing a service robot that can visit ailing satellites and refuel or even repair them on the spot.

Geosynchronous satellites are a vital part of the modern world. Orbiting 22,300 miles (35,800 km) above the earth, they are a key link in global telecommunications, and keep a constant eye on the planet’s weather. They are extremely valuable both for the work they do, and due to the cost of building them and putting them in orbit.

NASA astronaut Mike Fossum holds the Robotics Refueling Mission unit (Image: NASA)

Unfortunately, their service life can be frustratingly short. Even if a satellite operates flawlessly for years without a component failing, there comes a day when it runs out of propellant and can no longer keep itself on station and properly pointed. When that happens, it goes from being a vital part of the global infrastructure to so much space junk. With 149 government-owned spacecraft and 275 commercial satellites currently in geosynchronous orbit, that is a very large investment at risk.

NASA’s Goddard Space Flight Center is working to develop orbital robots that can intercept, refuel and service geosynchronous satellites. The refueling program is already at an advanced enough stage that a technology demonstrator called the Robotic Refueling Mission (RRM) was delivered to the International Space Station (ISS) in July of last year. The RRM was installed on a temporary platform outside the station.

Though it’s designed to refuel satellites, the RRM isn't just an outer space petrol pump. It’s more of a robotic mechanic with tools to manipulate wires, unscrew caps and operate valves. In March of this year the space station’s RRM, nicknamed “Dextre,” cut two twisted "lock wires" – each one measuring 20 thousandths of an inch (0.5 mm) in diameter. This was an extremely delicate operation and a first for a space robot.

Technicians in protective gear test satellite refueling pump hardware (Image: NASA)

The reason why the RRM needs these capabilities is that the service robot isn't just intended to refuel satellites designed to receive it, but others as well. Goddard wants a robot capable of carrying out what it calls the five “Rs” – refueling, repositioning, remote survey, component replacement or repairing – on any satellite that might require its services.

Working with Goddard are engineers at the Kennedy Space Center in Florida. Their job is to find a way to safely and effectively refuel satellites using hypergolic propellants such as nitrogen tetroxide, hydrazine and monomethyl hydrazine. It’s a tricky job because these propellants are highly corrosive and toxic, and have low viscosity, which means they spread easily whether you want them to or not. Worse, they ignite on contact with one another, so leaks are definitely out.

Also, the systems on the recipient satellite aren't very robust, so the pumping system needs to be very accurate to avoid blowing a hose or gasket. With this in mind, Kennedy has been testing a proof-of-concept pump. The next phase will be to develop a flight-ready pump and work out operating procedures with testing to begin in the next year. Meanwhile, the astronauts aboard the ISS will be carrying out a refueling demonstration later this year.

Source: NASA

About the Author
David Szondy David Szondy is a freelance writer based in Monroe, Washington. An award-winning playwright, he has contributed to Charged and iQ magazine and is the author of the website Tales of Future Past. All articles by David Szondy

As much as this is a welcome development according to Arthur C Clarke, if the world had never invented the microprocessor we would have had massive communication satellights which were manned space stations in their own right to service and maintain vaccum tube elecronic communication equipment in orbit, leading to a huge space cargo launching infrastructure many times that of today, All launches would have to be piloted, with so many people in orbit it leads inevitably to space colonisation rather than using robots and living on the Earth.

I wonder if we had to do this all over again, which way would we choose.


IMHO extending the life of expensive hardware in LEO will be a double edged sword with price points lower allowing a greater spread of services to a larger number of people due to decreased cost of maintaining services but technical advances slowing due to slower replacement with more advanced systems. L1ma, as much as I like Clarkes SciFi books he's just wrong on that one as we all are aware the spread of technology is based solely on making it low enough in cost that it can be affordable to a larger portion of the population (consider cell phones) and massive orbital stations doing a less cabable job due to inferior tech with a huge increase in cost from being not only manned but astronomically expensive to place into orbit (think space station) would put services out of reach for anybody but a wealthy countries government and a few of the very wealthiest in society.

Michael Gene

@Michael Gene

Of course the problem addressed by this article is trying to extend the life of current satellites if it is possible - maybe.

Most are not designed to be repaired, those dead in space such as the Astras have obsolete analogue transmitters. The reason they are not replaced by digital's is because they are occupying a slot in orbit and there is no way at present of removing them legally also if any satellites had been designed with standard modular components which were easily slotted in, we might have had a chance of upgrading them (i.e. replacing gyroscopes which are the main cause of failure). NASA has an uphill struggle with the current components but could force a future standard on the industry.

It was not untill late 1970's that the fuel crisis showed the cost of producing Hydrogen for the Saturn 5 to be untenable, but as SpaceX has demonstrated you never had to use it at all. The point of space colonisation is that it is cheaper to grow humans in Space and harvest resources there than to launch them from the Earth's gravity, but the habitats and industry have to be launched at a time when it was affordable, the odds being without microelectronics that we would have a small nuclear powered orbital colony of communist engineers in orbit with the old Soviet belief that Humans were an expendable renewable resource. President Reagans Freedom space station would have also been built to counter the Soviet one. Microelectronics created mechanical slaves to replace human ones but for good or ill kept people on the Earth because they were cheaper.

And to as putting those services out of reach of everyone - not true, once a Space station is put into geostationary orbit it stays there, its huge volume allows new components to be bolted on and unlike satellites needs never be outdated. Your digital revolution would have happened anyway, there would have just been 4 massive manned satellights covering the whole Earth rather than the 180 today at around $600 million to build and launch - the costs would probably have evened out, the point being that we would either have continued the space race and ignored costs or would have gone back to using Hydrogen peroxide or the current Oxygen Kerosene with SRBs.


Like this, give reason to extend ISS into 30 more years & under Pvt control. Launch refuelling probes to satellites worldwide. Awesome. Control from Ground or in ISS. Have 2 have new module for new mission.

Stephen Russell
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