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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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  • Wall-E

    • You're telling me that our consumer driven, planned obsolescence culture has extended into space and that now those tree-huggers are trying to extend their reach too? What is this world coming to?
    • by yog (19073) * on Monday October 22, 2012 @09:40AM (#41728517) Homepage Journal

      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.

      • by kiriath (2670145)

        But then they would get smart, want rights, form an army. We'll eventually be forced to black out the sun due to their mystical use of solar energy. Which will lead to them enslaving the human race and utilizing our comatose bodies as batteries.

        I should so write a book series about that...

    • R5-2do
  • So...um... (Score:5, Funny)

    by stillnotelf (1476907) on Monday October 22, 2012 @09:19AM (#41728349)
    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).
    • by Anonymous Coward

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

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

        by Rich0 (548339) on Monday October 22, 2012 @09:26AM (#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.

        • by tomhath (637240)

          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

          Care to explain how? In order to repair and refuel the robot must be in the same geostationary orbit as the satellite it's fixing. Read that carefully - geostationary orbit - it's not going to fall down.

          • by Dekker3D (989692)

            "Transfer orbit". Probably the kind of orbit where you transfer from atmosphere to "space" (as in, getting almost no drag from the atmosphere anymore). That's different from geostationary... and changing orbits takes a lot of fuel, that's simple.

            • by Yoda222 (943886)
              If the refuelling satellite is on GTO and the satellite is in GEO, the refuelling will not be very easy. Have you ever tried to refuel a running formula one with the spare tank on your bicycle ?
              • by Rich0 (548339)

                Yup, hence the whole point of my post. If you want it to come back down you need way more fuel, since you would have expended the energy to get into geostationary orbit and need to expend it again to come back down...

              • by shiftless (410350)

                Yeah, and the driver went on to win the race.

                you insensitive clod

            • by S.O.B. (136083)

              "Transfer orbit". Probably the kind of orbit where you transfer from atmosphere to "space" (as in, getting almost no drag from the atmosphere anymore). That's different from geostationary... and changing to a higher orbit takes a lot of fuel, that's simple.

              FTFY.

              Changing to a lower orbit takes a lot less energy.

              • by Yoda222 (943886)
                Going from GTO to GEO or from GEO to GTO needs the same DeltaV (in fact -DeltaV) So if you have the same initial mass and the same thrusters, you need the same amount of fuel. (but if you do GTO to GEO to GTO, you don't have the same mass ;-) )
            • That's different from geostationary... and changing orbits takes a lot of fuel, that's simple.

              Changing certain elements of the orbit, such as inclination, is very costly (unless the apogee is very high). Changing others, not so much. You can transfer between individual geostationary satellites at a fairly modest fuel cost, if you're willing to wait a little bit more. The machine could also employ electric engines, that would make the whole thing much more efficient. Geostationary satellites started using them some time ago anyway, to perform East-West station keeping, but I believe there are either

          • by Rich0 (548339)

            Read my whole post carefully.

            To get to geostationary orbit there are two energy expenditures. One is from ground to geostationary transfer orbit. The other is from transfer orbit to geostationary orbit.

            To get back there is really just one energy expenditure - from geostationary orbit to transfer orbit. The bottom of transfer orbit would be far enough in the atmosphere that drag would do the rest - you don't need to re-circularize it with propellant.

            However, no question that you'll need a ton of fuel just

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

          by Baloroth (2370816) on Monday October 22, 2012 @09:53AM (#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 Rich0 (548339)

            Fair enough, but I'm sure it will still take a fair bit. If the tanker sat is designed to be simple I doubt it would be worth it. Plus now you have to contend with re-entry - that's a lot of extra mass.

        • by S.O.B. (136083)

          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.

          The reason it takes fuel to get to geostationary orbit is because you're fighting gravity. Why would you need to use the same amount of fuel to come back down when gravity is helping you along?

          As someone else pointed out, the refueling robot is now a lot lighter having just refueled a satellite so even less fuel is required. My guess is all you have to do is aim the refueling robot at it's reentry window, give it a nudge and let gravity do the rest.

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

            by Patch86 (1465427) on Monday October 22, 2012 @12:15PM (#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")

            • by Rich0 (548339)

              Yup. Granted, others have pointed out that mass will be lower so the amount of fuel required to change velocity will be lower. However, it will still be a significant amount of fuel to get back down. More if the whole thing needs a fancy re-entry shield and the required additional structural strength.

      • by Coisiche (2000870)

        A-ha! A perfect cover story for the X-37B. Expect to read it in a press release soon.

      • Bonkers (Score:3, Interesting)

        by Anonymous Coward

        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 ;-)

        • 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)

          No, the Space Shuttle program is just anecdotal evidence. Anecdotal counter-evidence would be fixing and maintaining the Hubble Space Telescope, as opposed to building a launching a new one. But don't allow facts get in the way of your thoughts, that's never good.

        • by Anonymous Coward

          I'm not sure why this is modded up. The shuttle was an expensive boondoggle, but that was because the flight rate was low and fixed costs were high. A single shuttle flight cost around $200,000,000 and put about the same amount of mass into space as a Saturn V did at 10x the cost, most of it just happened to be wings and fuselage. What raised the cost of a shuttle flight to over a billion dollars a time were the enormous fixed costs of maintaining the required infrastructure, which would have applied just a

        • Obligatory ID4 quote:-

          Julius Levinson: "You don't actually think they spend $20,000 on a hammer, $30,000 on a toilet seat, do you? "

        • by sjames (1099)

          The Space Shuttle was a first attempt. It's no surprise it didn't work exactly as planned.

          For example, if we were to design it again now, it would have an expendable ablative heat shield rather than the tiles.

      • by sjames (1099)

        I would think an expendable tanker would be a better option. Put it in LEO, the refuelers fill up from it and go about their business.

    • Yes, the space refueling robots can refuel each other, too. Haven't you ever played Total Annihilation????

    • Perhaps a single refueling robot that can top off several satellites and reposition a few more is cost effective enough to justify a one-time refueling satellite? Long term, we could imagine that such robots will be refueled via space based resources (asteroid mining, etc).

    • by khallow (566160)
      Well, we could launch more propellant from Earth. Launch it, the robot tanks up, and keeps going. One could even do major orbit change burns at this time using excess propellant.
    • Re:So...um... (Score:4, Informative)

      by Baloroth (2370816) on Monday October 22, 2012 @09:51AM (#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).

      • Oh, I was definitely being snarky (perpetual motion? infinite mass?). I understand the aerial refueling idea - a certain Mr. Clancy always wrote lovingly of the KC-135. Sometimes figuratively, and once more literally when he called it something like "airplanes having sex". In general I'm in favor of any idea that will reduce the orbital debris problem.
    • by mk1004 (2488060)
      If it doesn't matter how long you take to get from LEO to geosync and back again, then maybe an ion-drive using solar panels for power. That maximizes the payload that gets to geosynchronous orbit, and you resupply the repair satellite periodically while it's in LEO. One issue I'm concerned with is how standardized any available connections are on the satellites to refuel them. But the repair satellite could be made versatile enough to bring satellites to LEO for repair/refueling. Perhaps someone on the ISS
      • And if the time really doesn't matter, then you use a flashlight drive or solar sail....

        • by mk1004 (2488060)

          OK, the SMART-1 http://en.wikipedia.org/wiki/SMART-1 [wikipedia.org] went from an initial orbital period of about 11 hours to 25 hours in about 147 days. This was achieved running the ion drive for 1/3 to 1/2 of the orbit, since they wanted a highly elliptical orbit. LEO for the repair/resupply satellite would start with a more circular orbit and a period of about 90 minutes. If you run the ion drive for most of the orbit, I'd guess that would roughly balance out the lower starting point. Only 22% of the weight was propell

    • by Belial6 (794905)
      Hopefully, the refueling robot isn't being launched over and over. Much better would be to put a spacecraft up there that can pull fuel from a big dumb lumbering tanker and deliver it to the specific satellites. This way, the craft being launched full of fuel can carry more fuel/parts/whatever, and doesn't need to carry all of the equipment for performing the more detailed work.
  • by LifesABeach (234436) on Monday October 22, 2012 @09:27AM (#41728423)
    Refuel, Reposition, and Repair

    With apologies to AAA.
  • by Anonymous Coward

    All NASA has to do is ask the Air Force if they can get a civvie version of the X-37B.

    Yeah they keep it missions "secret" but this pretty much fits the only reason for having an autonomous space-truck with a robotic arm and cargo bay. Afterall, they're not going to be getting a full-sized replacement for the Shuttle anytime soon, so this is the next best thing.

  • by Rich0 (548339) on Monday October 22, 2012 @09:39AM (#41728509) Homepage

    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.

    • by tomhath (637240)
      The satellites frequently reposition themselves, because no matter how accurate they are placed into orbit they drift a little. I can see having a tanker satellite up there that can help reposition one that wandered out of place and refuel it if the physics of docking with it are possible. Maybe even replace a solar panel once they standardize external parts and connections. The tanker would need a much stronger engine so using it to reposition would probably make sense in some circumstances.
    • by thrich81 (1357561) on Monday October 22, 2012 @10:07AM (#41728767)

      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.

      • by eth1 (94901)

        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.

        Well, they could actually be trying to subsidize the refueling of government craft with corporate money, too, depending on how you look at it.

        In any case, I'm curious how they plan to refuel a satellite that wasn't designed to be refueled in space. It's not like you can just unscrew the gas cap and stick a hose in. (maybe that's why "repair" is included in the mission parameters? Some amount of dis/re-assembly required?)

    • by Kjella (173770)

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

      It might not be Hubble-class replacement jobs we're talking about, it may be changing the windshield wipers but there's nobody to do it because it's 36000 km away from the nearest service station. Yes, each repair job will probably be a custom fit but I imagine this refuel/repair course is laid out before it even launches, I doubt it'll be orbiting up there waiting for customers.

      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?

      Weight and size constraints? Big rockets costs big money, if you can get away with a smaller launch vehicle and a top up in orbit

      • by Rich0 (548339)

        You might have hit on something with the military bit. They stick some giant billion dollar mirror in space and just need some fuel to keep it up. Might let them do more maneuvering to put it where they want it when they want it there, and make it harder to keep track of.

        • by cusco (717999)
          And once again NASA will be footing the bill for the Pentagon's profligate waste.
    • Refuel and reposition will probably not need to be run at the same time. I imagine, as others have, the refuel capability may be difficult and will have to be designed into the satellite in the first place. For sats that need to be repositioned but cannot be refueled this robot could give them a boost, thereby saving it some much needed fuel for later maneuvers. (Say the robot was passing a sat without the capability to be refueled on its way to another customer, owner of the robot can offer owner of the
    • by khallow (566160)

      Maybe also in reposition if a big change is involved (but why would you need to move it anyway?).

      I'll answer this one since there are some relatively straightforward answers to that.

      There are two big reasons. First, satellites don't always end up where you want them. For example, the recent SpaceX launch put its payload in an incorrect orbit that'll require some burns by the satellite to get into the desired orbit. The more onboard propellant you use, the shorter the lifespan of the satellite.

      Second, there's the closely related problem of tight launch windows which is especially a problem when fi

      • by Rich0 (548339)

        Well, if the satellite could burn its way to the correct orbit better to let it do so, and then just refuel it when the tank gets low. That beats burning fuel to reach it at point A, and then burning fuel on both to get to point B.

        Unless the tanker had quite a bit of fuel any but the smallest inclination changes would be very expensive, unless the orbit was very high at at least one point. It would make far more sense to just launch at the right time than to give the satellite a ton of energy during launc

        • by khallow (566160)
          NASA is looking into a number of related, but not necessarily complementary activities. Repositioning can be done with almost any satellite today, unless it happens to be tumbling in a way that the repositioning satellite can't cope with and "grab" the target satellite. Refueling requires in addition some sort of structure on the target satellite to accept propellant. The two vehicles have to be compatible. I imagine you can count on one hand the satellites that can currently be refueled in space.

          My view
  • Surely one of the main jobs this kind of program would encounter is retiring any satellite that it finds it cannot repair/refuel? Effectively just re-positioning into an orbit that intersects the atmosphere but given the problems of space junk I would have thought they would want to highlight this potential benefit especially as it increases the "R" count to 6.
    • I was going to suggest "Reclaim" or "Recycle".

    • by gmuslera (3436)
      Retiring is a necessary thing, but not in the same category. Taking out old/dead/broken satellites that could be a risk in a near/middle term. But what about the non broken ones? nuke them and send up a replacement or try to refuel them? In the middle term could be cheaper to try to keep them up and running than somewhat destroying them.
  • they should have thought of that 30 years ago
  • Fit out the sats with an electric drive instead, like this: http://emdrive.com/ [emdrive.com]

  • By the time a satellite in geostationary orbit needs refueling the technology will have advanced a lot, so why not just repelace it with a newer satellite that has more bandwidth and capabilities.. It might make sense for speciallised things like space telescopes, but not for general comunication / TV satellites.

  • The next step is to build a refinery right there in orbit, and mine some asteroids for raw materials. Or some Jupiter moons, even better, since they are loaded with hydrocarbons. That is where the real savings would be, since you're not paying to blast all that fuel into space.

  • The orbit, itself (Score:5, Interesting)

    by dpilot (134227) on Monday October 22, 2012 @10:45AM (#41729199) Homepage Journal

    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.

    • 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.

      De-orbiting from geosync is way to expensive to be an option (too high delta-V). What they use instead is the "graveyard orbit". At the end of operational life, the satellite just does some final burns to raise its orbit by a few hundred km, where it is no longer geosynchronous but also out of the way of the geosync orbit. Satellites launched into geosync are required to have this capability.

      • by dpilot (134227)

        How save is the graveyard orbit, really? It'll be even less likely to decay than geosync, but isn't it then a "fixed size trashcan?" At some point won't you start getting collisions, and some of the pieces might get enough delta-V to get in the way. Certainly the graveyard orbit is cheaper than de-orbit, but for the long run, have our repair satellite tow them out there and attach them to the junkyard. (The other dead satellites, all "tied" together.)

    • by Guppy06 (410832)

      More likely, the most valuable thing up there is not the satellite, it's the position it's occupying.

      Like the real estate agents say, "location, location, location."

  • How come we let robots have all the fun? I'd sign up for a job as geosync satellite gas-station attendant in a heartbeat! Who wants to be a coddled planet-bound human? I'll welcome our robot overlords only if they let me in on a piece of the action.
  • Most, if not all, present day satellites do not have fuel tanks that are made to be refueled, a lot have tanks that aren't even accessible from the exterior. They are going to have to come up with some kind of a way to put a hole in a tank, that doesn't put metal shaving inside, and install a refueling port that is perfectly sealed to the tank for this to be able to work. Might have to wait for the next gen of satellites before starting this service. Though NASA being NASA, they have pulled off some amazing
    • by 0123456 (636235)

      Hint: how do you think those tanks were filled on the ground?

      I believe this is mainly intended for new satellites, but there has been talk about refueling old ones using existing ports.

  • by SethJohnson (112166) on Monday October 22, 2012 @01:06PM (#41731263) Homepage Journal
    First it was self-serve gas pumps. That relegated the station attendant to a cash register operator.

    Then they implemented gas pumps with credit card readers. No need to interact with a human running a cash register. Fully automated fuel stations.

    Now, we've got a huge new industry being invented, and they're not even including humans in any part of this transaction. No one to ask what grade of fuel to use. No one to check the condition of the wiper blades or upsell the satellite owner on a new air filter. Probably going to have NFC chips on the satellites so there's not even a credit card to swipe to charge the customers for the fuel.

    I gotta get on the horn to my congressman today. This is going to be too efficient at the cost of jobs. We need to employ a human operator up there or else there is no hope of the unemployment rate dropping below 7%.

    Seth
    • by evilviper (135110)

      Then they implemented gas pumps with credit card readers. No need to interact with a human running a cash register. Fully automated fuel stations.

      Can't have unattended gas pumps, so somebody is still getting paid, they're just sitting around, trying to hawk slim jims, instead of spinning trying to handle everyone's cash.

      Besides... credit cards are going down. Last 3 different gas stations I went to, all had dual signage... One column for gas prices if you pay in cash, and one (higher) for people paying

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