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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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The title calls this a "tugboat", but as far as I can see from the article, it is really just an extra fuel tank and set of rockets.
A real tugboat would be very cool indeed -- something which could grab a satellite, move it up back into the correct orbit, and then let go and move on to the next satellite -- but it looks like this is rather less so.
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Wha? They're using them:
from http://www.orbitalrecovery.com/faq.html
Attitude control for the SLES and the telecommunications satellite to which it is mated is handled by ion thruster packs mounted on deployable booms. These booms are extended to provide sufficient thruster impulse for control of the SLES/telecom satellite combination.
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.
Do you think this company is gonna charge the extra 40 cents per gallon for full-serve? If so, they better at least wash the windows and check the oil in the satellite.
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
Actually the shuttle is incapable or reaching GeoSynch orbit w/o substantional modifications - and dangerous ones (like a fuel tank in cargo bay, extra SRB, etc) or refueling at the ISS if that ever becomes a possibility. The highest altitude a shuttle has ever achieved, IIRC, is around 490 miles.
So if there really was a mess in GeoSynch they would just be screwed...
Both of the articles mentioned that fuel is not the only problem, the rest of the satellite has degraded as well. So, why don't they come up with a good garbage collection method to periodically get rid of the old sattelites. This could also partially answer the problem that it's starting to be pretty crowded there in the orbit already.
I'm curious why they haven't started using something like this to remove old satellites. A remote controlled vehicle equipped with a mass delivery system (rail gun, propellent, hell it could even ram them) that would deliver enough force to knock the old satellites out of orbit and maybe on a vector towards the sun where they will be quietly taken apart into component atoms.
Any atronomists/physicists know what the gravitational pull of the earth is in orbit and how much force would be necessary to kick, say, a 2000 lb satellite to escape velocity?
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The highest altitude a shuttle has ever achieved, IIRC, is around 490 miles.
Rubbish. I saw a documentary only last week where a suttle left the Earth's orbit and went thousands of miles out into space to land on an asteroid. They didn't have extra fuel tanks in teh cargo bay eitehr, cos it was full of these neat, large-wheeled, big trucks fitted with drills and machien guns and everything - they could even jump mile wide cnayons. You just ask the leader of the mission, Harry S. Stamper , a rough-neck, Texas oil man and his team of expert oil drillers if it ain't so!
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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.
Check out the DARPA project for more info. Do a Google search on "orbital express" for other links and news.
~afniv
"Man könnte froh sein, wenn die Luft so rein wäre wie das Bier"
Richard von Weizs
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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I have another shuttle sighting. Last week the Space Shuttle flew not one, but two secret BATF missions to an insect-like alien vessel in high earth orbit with no apparent problems, to capture the renegade space captain from the Light Universe, Stanley H. Tweedle.
These shuttles have capabilities that we don't know about - and they are as easy to drive as your car.
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Maybe its just very big?...
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