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NASA Working On Refueling Satellites

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."

15 of 116 comments (clear)

  1. So...um... by stillnotelf · · Score: 4, Funny

    What will refuel the refueling robots? Refueling-robot-refueling robots? Hopefully they're universal and can refuel each other, at which point we have a perpetual motion machine (as opposed to an infinite mass of fuel-hungry robots in geostationary orbit).

    1. Re:So...um... by Rich0 · · Score: 4, Informative

      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.

    2. Re:So...um... by Baloroth · · Score: 3, Informative

      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).

      --
      "None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
    3. Re:So...um... by Baloroth · · Score: 3, Informative

      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).

      --
      "None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
    4. Re:So...um... by Patch86 · · Score: 4, Informative

      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")

  2. Re:Headline: NASA WANTS MONEY by K.+S.+Kyosuke · · Score: 5, Insightful

    Quit wasting our tax dollars on this boondoggle when people are dying from lack of healthcare.

    [sarcasm warning] Yes, because satellites are never used for saving lives. [end of sarcasm warning]

    --
    Ezekiel 23:20
  3. Talk about Scope Creep by Rich0 · · Score: 4, Interesting

    I could almost see there being some value in refuel. Maybe also in reposition if a big change is involved (but why would you need to move it anyway?). Take a few pictures of it if you want, since that is fairly cheap.

    However, when you start getting into repair you're talking about a massive increase in cost and decrease in reusability of the refueling ship.

    And if you don't do repair, then you need to design the satellites to have components that last for decades but a fuel supply which lasts much less - why not just launch it with a lifetime fuel load?

    Repositioning only makes sense if it was unplanned and needs more propellant than could be carried by the satellite. If you dock a ship to it and use that to move the satellite, then you need enough fuel to reposition the combined mass of both. It would be smarter to just refuel it and let the satellite move itself.

    Oh, and unless you're really patient, moving from satellite to satellite takes a fair bit of fuel (a little nudge goes a long way if you're willing to wait, but with each orbit lasting a day it will be probably weeks between encounters if you don't want to do large burns).

    I think that the only way private companies would sign up for this refueling service were if the cost of the service were basically subsidized on the backs of taxpayers. I could be wrong, and that would be wonderful, but this really seems like a solution looking for a product. Sometimes it really is cheaper to just make a new one.

    1. Re:Talk about Scope Creep by thrich81 · · Score: 4, Insightful

      You hit on my main concern in your last paragraph -- taxpayers subsidizing the owners of the geosynch satellites. If there is one space activity which private industry has figured out how to make a profit on it's geosynchronous satellites -- if refueling them is a great idea then the owners of the satellites can invest in developing the technology to do it. Let NASA spend its money going to Mars, etc.

  4. What about my car? by yog · · Score: 4, Funny

    Maybe if this is successful, Nasa can spin off the technology to earth-bound vehicles as well. I would love to have some robot wander by from time to time and refuel or service my car overnight! You could even have robotic landscapers and robotic Christmas decoration putter-uppers. Really, the possibilities are endless. And, of course, a commercial success with this would help pay for more space exploration.

    --
    it's = "it is"; its = possessive. E.g., it's flapping its wings.
  5. Bonkers by Anonymous Coward · · Score: 3, Interesting

    The whole "let's re-use spacecrafts" has been conclusively demonstrated to be Economic Nuts by the Space Shuttle program (1kg lifted by the shuttle is ten times more expensive than 1kg lifted by a throw-away rocket) . I have the definite feeling NASA wants to prove this once again, just in a different way.

    But maybe we should read this message metaphorically ;-)

  6. Re:Headline: NASA WANTS MONEY by SilentStaid · · Score: 5, Informative

    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; http://en.wikipedia.org/wiki/Military_budget_of_the_United_States

  7. Re:Civvie version of X37-B by rossdee · · Score: 3, Informative

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

  8. Re:Headline: NASA WANTS MONEY by GodfatherofSoul · · Score: 5, Funny

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

    Good News! We've got the firepower to make that happen since we haven't been wasting money on satellites!

    --
    I swear to God...I swear to God! That is NOT how you treat your human!
  9. The orbit, itself by dpilot · · Score: 4, Interesting

    More likely, the most valuable thing up there is not the satellite, it's the position it's occupying. Once upon a time, we tried to keep 2 degrees of separation between geosync satellites - meaning that there were 180 "slots" where one could be placed, and obviously fewer than that that could service any one location. The separation keeps dropping, but that makes the need for stationkeeping more precise, probably calling for more fuel, etc.

    So the best thing here is to keep those geosync slots in use, and not chewing up an empty slot with a dead or useless satellite. I'll have to agree with what someone else said - that de-orbit should be a published option, as well.

    Personally, I believe the best option is a big, gravity-gradient-stabilized boom, with some serious solar panel capacity on the outer side, battery capacity to match, and standardized electrical and mechanical hookups. Then rather than sending up complete satellites, lease hookups on the boom, and just send up an electronics package. In this case, the "service satellite" carries the package up, anchors and connects it, and does initial checkout.

    --
    The living have better things to do than to continue hating the dead.