Re: Do satellites need refuelling?
The idea seems neat, but is there really a need to refuel satellites?
Most geosynchronous communication satellite lifespans are determined entirely by fuel, which runs out before the other factors you mentioned kill the satellite. After all, a designated orbital slot in geosynchronous orbit is subject to a lot of perturbations and satellites there need 50 to 55m/s of delta-V per year. This is why the aerospace and telecommunications industries are adding nekkid pictures of the Boeing 702SP all-electric satellite bus to their pr0n folders. By using entirely ion propulsion, its fuel endurance and thus time on station is significantly improved.
Low orbit spy satellites are another group of fuel pigs. They tend to encounter a lot of atmospheric drag and frequently modify their orbits to more quickly pass over a target of interest.
Its been nearly 60 years since Sputnik and as far as I know nobody has bothered with satellite refuelling
It was part of the plan for the US shuttle-as-a-space truck. The shuttle was launching up to 3 satellites (several flights launched 3); recovering satellites for repair (STS-41C & STS-51A, 3 total recoveries for repair); repairing satellites in flight (STS-27, STS-49, Hubble missions), and, yes, refueling satellites (STS-41-G). The classified shuttle military missions may have actually refueled spy satellites (e.g., STS-27).
The plan was there for satellite refueling, but widespread implementation was halted by the Challenger disaster. A lot of plans for satellites altered after Challenger: design for retrieval was almost completely abandoned; refueling was abandoned; satellites mostly stopped being designed for in-flight repair; the US military gradually disengaged itself from shuttles; etc. Now you see satellites designed for the longest possible life, going to extremes like all-electric propulsion.