For sci-fi writers the prospects of orbiting ‘space tugs’ have been a staple of their writings. Whether to somehow rescue problem satellites, or simply act as an orbiting refuelling source, the ‘satellite life extension’ concept seem to have all the common sense logic that would propel the idea into real world usage.
‘Not so’, seems to be the response. Trade publication Space Intel Report (SIR) says that despite Intelsat and SES having commenced some degree of planning for such ‘space tugs’, the overall sentiment now is that the industry’s technology is moving so fast that instead of planning for a 20 or 25 year life in orbit, it is better to build shorter in-orbit lifetimes for satellites.
The industry recognises that there is an inherent extra – and major – risk when docking the ‘space tug’ with the target satellite, let alone the risk of transferring highly volatile fuel from one craft to the other.
SIR quotes SES’s CTO Martin Halliwell who says that the operator’s next generation of satellites will likely have in-orbit lives of between 13-16 years. Halliwell says investing in a refuelling mission for a craft that’s perhaps 12 years-old with a ‘space tug’ is not sensible when the orbiting satellite is – in effect – nearing the end of its life.
There’s another benefit increasingly used in today’s normal launches, and which is electric propulsion of a satellite which is now a standard feature on most geostationary satellites.
Stewart Sanders, EVP Technology at SES Networks, is quoted by SIR saying that the technology demands on today’s operators are not favouring the in-orbit refuelling option. He also argues that the extra costs of installing a lighting system on a satellite so that ground-based operators could see what they were doing during the mating process adds significant costs of a craft.