Canada

[Crisp]

Canada?s Dextre robot passes first-of-a-kind test to refuel satellites in space

This NASA photo relealsed on July 18, 2011 shows astronaut Mike Fossum as he carries a Robotics Refueling Mission (RRM) payload from Atlantis' cargo bay to a platform used by the space station's famous robot DEXTRE. Pictured above on the far left, DEXTRE prepares to help move a failed space pump back to Atlantis.

The Canadian Space Agency?s ?Dextre,? the robotic handyman on board the International Space Station, made history over the weekend by successfully refuelling a mock satellite outside of the station.

The refuelling mission ? a collaboration between NASA and the Canadian Space Agency for their experimental Robotic Refueling Mission (RRM) ? was a pivotal demonstration for robots? ability to refuel satellites in space, extending their service lifetime.

Since 2011, Dextre, a two-armed mechanical robot not far removed from ?Star Wars? R2-D2 has successfully performed three tests on satellites that weren?t built to be repaired in space.

From the Canadian Space Agency:

RRM is a significant step in pioneering robotic technologies and techniques in the field of satellite servicing-saving ailing space hardware by refueling or refurbishing them before they become space debris. The ability to refuel satellites in space could one day save satellite operators from the significant costs of building and launching new replacement satellites. With over 1100 active satellites currently operating in the near-Earth environment (many of them worth hundreds of millions of dollars), and an additional 2500 inactive satellites still orbiting around our planet, the savings could be substantial.

Source

[DocM]

Fuel depots are the future IMO, enabling exploration gateways, space docks etc. etc. The problem is using them with liquid oxygen and hydrogen, which are cryogenic, and hydrogen tends to boil off if it warms at all.

There is also the problem of using 2 fuels, meaning 2 tanks, 2 sets of plumbing, 2 sets of seals. Twice as many places for leaks. Another method would be the continued use of noni-cryo hypergollic fuels, but they're toxic as hell.

Sounds like a place for s single fluid propellant system to simplify matters. For ion or plasma engines this is the rule - argon, xenon etc. and not much of it, but you need big solar arrays or a reactor to power them..

Another possibility is NOFBX, which gets tested as ISS after being taken up on a Dragon spacecrat. It's a blend if nitrous oxide, a light hydrocarbon like acetylene or ethane, and a mix of stabilizing additives.

[SALSN]

Here is a video regarding the subject: