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NASA Space Science

NASA Working On Refueling Satellites 116

Posted by Soulskill
from the fill-'er-up dept.
cylonlover writes "Geostationary satellites cost a fortune and, despite their sophistication, they break down or eventually run out of propellant to keep them oriented. This is unfortunate when the nearest garage is back on Earth, so NASA wants to remedy this with an orbital version of roadside service. The space agency is developing a service robot that can visit ailing satellites and refuel or even repair them on the spot. The refueling program is already at an advanced enough stage that a technology demonstrator called the Robotic Refueling Mission (RRM) was delivered to the International Space Station (ISS) in July of last year. The RRM was installed on a temporary platform outside the station. NASA's Goddard Space Flight Center wants a robot capable of carrying out what it calls the five 'Rs' – refueling, repositioning, remote survey, component replacement or repairing – on any satellite that might require its services."
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NASA Working On Refueling Satellites

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  • Re:So...um... (Score:5, Informative)

    by Rich0 (548339) on Monday October 22, 2012 @10:26AM (#41728413) Homepage

    The refueling robots could just drop out of orbit to Earth to be recovered and reused?

    That way they can only carry half as much fuel? It takes a lot fuel to get from transfer orbit to geostationary orbit, and just as much fuel to get back down. The energy to get to transfer orbit in the first place is a one-time expense, since atmospheric drag and gravity will get you back down from there.

  • Re:So...um... (Score:4, Informative)

    by Baloroth (2370816) on Monday October 22, 2012 @10:51AM (#41728619)

    What will refuel the refueling robots? Refueling-robot-refueling robots?

    Pretty sure you're just being snarky, but the principle is the same as tanker aircraft. A satellite dedicated to carrying fuel can carry vastly more of it than a satellite dedicated to communications. And after it is done, the mass of the fuel-carrying robot is significantly less than it was when placed into orbit, so the cost of de-orbiting is much much less than the cost of orbiting it in the first place (since the vast majority of the mass of the satellite is now gone).

  • Re:So...um... (Score:4, Informative)

    by Baloroth (2370816) on Monday October 22, 2012 @10:53AM (#41728645)

    and just as much fuel to get back down.

    Provided the mass stays the same. Can you guess why a tanker-satellite might have significantly less mass after it's re-fueled a bunch of other satellites? (hint: it's because it isn't carrying all that fuel any more).

  • by SilentStaid (1474575) on Monday October 22, 2012 @11:22AM (#41728937)
    I hate to reply to myself, but one shot of caffeine later and the results are in:

    Projected budget for FY12 for NASA: $17,770m, or 0.48% of the total Fed budget.
    Projected budget for FY12 for the Military: $1,030,000m – $1,415,000m, or potentially 33% of the Fed budget.

    So now the question is, what has NASA spent historically? Well, if you normalize dollar amounts over the course of NASA's almost 60 years the grand total is 870,709m or a healthy 160,000m dollars below the lowest estimated cost for the military this year...

    I don't want to live on this planet anymore.

    Sources: http://en.wikipedia.org/wiki/Budget_of_NASA [wikipedia.org]; http://en.wikipedia.org/wiki/Military_budget_of_the_United_States [wikipedia.org]
  • by rossdee (243626) on Monday October 22, 2012 @11:29AM (#41729009)

    I don't think the X37-B can reach geostationary orbit

  • Re:So...um... (Score:5, Informative)

    by Patch86 (1465427) on Monday October 22, 2012 @01:15PM (#41730513)

    That's not how orbital mechanics work.

    Orbit is basically (in really inaccurate terms which someone will undoubtedly shoot me down on) where you're travelling sideways fast enough that, although you're falling towards the Earth, you keep missing. It's like when you throw a ball in a straight line, and it travels along and curves down towards the ground. Imagine throwing the ball so hard that the curve downward takes it over the horizon. This trick works because atmospheric drag is so little in orbit, once the object has achieved a high enough speed that it keeps "missing" the Earth, it retains that speed for a good long time.

    So, in order to get up to geo-stationary orbit, you basically have to add a huge amount of speed to your satellite by burning lots of fuel. Once it's up to speed and stops burning its engines, it stays up to speed.

    If you want it to come down again, you need to cause it to lose speed. In order to do that, you need to burn a rocket engine in the opposite direction to slow it down. It takes the same amount of fuel to reduce speed by 1 km/h as it does to gain speed by 1km/h. So you need to burn almost* the same amount of fuel to get back down as you do to get up there.

    (* "Almost" because you only need to lose altitude to the point where atmospheric drag picks up, and then you start to lose speed "naturally")

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