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Space Tugboat to Refuel Satellites
Faeton sent in this article about a proposed space tugboat to refuel aging satellites. Looks like they're just going to bolt on some extra thrusters with a new fuel supply, guidance system, etc.
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This sounds remarkably like the first step in George William Herbert's "Phobos on the Cheap" paper, here.
The basic idea of the paper is that you could fund the development of these things by doing satellite maintenance and related things, then use one of them as the propulsion system for a trip to Mars orbit.
So I wonder if this is that project.
ION drives require power. The idea is to design newer satelites with larger solar arrays so they can last 20 years up there instead of 10. If you're going to add a booster you don't want it to have solar panels because they would be unlikely to work with all those old satelites without a redesign based on where the existing solar panels are on each one. Plus it might not make sense economically to add a 20 year propulsion system to a satelite with 10 years left in it.
As for wanting a "real tugboat" that attaches to multiple satelites... well the biggest problem is the docking, when we've had these working long enough to have confidence in automatic docking, then we can think about a general purpose tugboat. Remember it would have to dock with each satelite many times over a 10 year span, and transit between all the satelites it wants to service. Perhaps an ion based one could have a 25-30 year life span, but then you'd be testing two undertested technologies at once instead of just the docking. I'm not even sure they should be allowed to do this in geosynchronus orbit before it is tested in other less essential orbits; it's going to cost $$$ for the shuttle to go up there and clean up the mess when one of these fails.
From http://www.orbitalrecovery.com/about_us.html:
The SLES also can be used to rescue spacecraft that have been placed in a wrong orbit by their launch vehicles, or which have become stranded in an incorrect orbital location during positioning maneuvers.
They don't say anything about what happens after the SLES has moved the misplaced spacecraft. I suppose it would really depend on the needs of the rescued craft -- ie, whether it has enough on board fuel to maintain and adjust its attitude, or whether the SLES needs to hang around to help it.
As for a business model, well, how many satellites need rescuing? I would think that they're right to focus on the predictable market of sats that run out of juice instead of relying on error (human or mechanical) to create opportunities for them. At least, in the short-term. Once they've got their birds flying and have some real world experience, maybe they'll start getting creative with them and send them on "Extended Missions" once the sat-moving job is done.
But the thing is... old satellites don't die. They just sit up there, cluttering up the orbital space. The GPS system, for example, expects to retire satellites at a regular rate into "parking orbits". In fact recently, as this article in Space Daily shows, it was discovered that the parking orbits chosen will degrade and pose a threat to the operating GPS satellites in 20 to 40 years. This is a long-term problem that is only getting worse.
Refueling satellites at least gives us the control of them needed to take them out of orbit if required.
Anna B
When I studied satellite communications in grad school, the comment was always that the life span was to long on most communications satellites, not to short. We were shown graph after graph that illustrated that by the time the damn things were half way through their life cycle, a better model was available that handled a lot more traffic, better quality, half the size/price, or whatever. So you had a precious GEO slot taken up by a bird that was obsolete, while your competitor has a new one about to launch.
These things probably only have two useful applicaitons, orbital repair (not repair in orbit, but of the orbit), and de orbiting something to salvage the GEO slot. Not to say that the technology isn't great on its own merits.
One of the first applications of the Shuttle back in the 70s/80s was that it would carry a SpaceTug to retrieve satellites from orbits higher than the shuttle to travel.
Does anyone know if Challenger had an impact on why it's taken so long to return to this, or was this one of those "oh YEAH, we promised this to Congress back in 1978" deals?
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