Space refuelling

SPACE

“ This mission aims to demonstrate the viability of robotically maintaining spacecraft while in orbit”

The RRM’s key kit

Fewer heavy tools keeps costs down, so the RRM module houses just four multipurpose devices. The Wire Cutter is used for delicate operations; not only can it snip cables, but it also has a deft enough touch to move aside the thin layers of delicate thermal blanket that insulate satellites. The Multifunction tool connects with four adaptors, removing various caps on the RRM module. The Safety Cap Removal tool is likewise equipped with adaptors to take off screws and caps, plus has two cameras either side of its manipulator for close-up views. Finally, the Nozzle connects the fuel supply via a hose and is responsible for opening and shutting the valve.

On board the module are the Wire Cutter, Nozzle, Multifunction and Safety Cap Removal tools

Astronauts work on the RRM module during an extravehicular activity outside the ISS

Servicing satellites

How are satellites refuelled and repaired while drifting out in Earth’s orbit?

At this moment satellites aren’t actually serviced in space, simply because it’s too diffi cult, expensive and risky to maintain them up there. These machines are sent into orbit with crossed fi ngers and, if they’re lucky enough to survive until their fuel runs out, at best they become a fl oating relic and, at worst, a liability to other projects. But NASA’s Robotic Refueling Mission (RRM) is seeking to change all that.

Currently in development, this pioneering mission aims to demonstrate the viability of robotically maintaining spacecraft while in orbit, using the International Space Station as a platform. On board, the two arms of the ISS’s Canadian robot Dextre will act as the technician, remotely controlled from Earth to approach its target in orbit, then reach into the RRM module and pick out one of four versatile tools for mending an ailing satellite. This module is very compact – around the size of a washing machine, weighs in at 250 kilograms (550 pounds) and will be loaded with 1.7 litres (0.45 gallons) of liquid ethanol fuel, to ascertain the viability of refuelling in orbit.

The RRM mission is about halfway through its tasks and is scheduled to fi nish before summer 2013. A dedicated refuelling craft – effectively a fl ying petrol station – is also in development and is slated for launch in 2015.

Thinking ahead

You might wonder why NASA is going to all this trouble just to prove that it’s possible to refuel and fi x satellites in space. Why go to this much effort when the disposable nature of satellites has been a perfectly acceptable model for decades? Technology has developed to the point now where refuelling and repairing satellites is becoming more cost effective, adding years to the life of existing satellites at a fraction of the price of another launch. Not only could satellite servicing via a remote robotic station in orbit be economical for an operator, but for NASA it will enable safer and less expensive maintenance on its own orbital craft, as well as the ISS. It’s also a step towards clearing up the masses of space junk already drifting in the geosynchronous zone.