back to article NASA spunks $127m on SSL-powered robot to refuel satellites in space

SSL (previously Space Systems/Loral) has won a contract to build a robot capable of refueling satellites in orbit, whether or not they have been designed to get more fuel. There are already scores of satellites in orbit that are useless due to lack of fuel, and NASA wants the ability to refuel future orbital platforms without …

  1. Swiss Anton

    Do satellites need refuelling?

    The idea seems neat, but is there really a need to refuel satellites?

    There are four things that constrain the life of a satellite; fuel, technology, reliability and a random hit from some space junk. Regarding reliability, there is a trade off between the added weight for backup spares and the cost of launching that weight into orbit. Technology is always progressing, and old sats just won't aren't good enough for today's needs (for instance 4K TV). I guess heavy armour could provide some protection from space junk, but again, heavy means added launch costs.

    Its been nearly 60 years since Sputnik and as far as I know nobody has bothered with satellite refuelling - is this because it is pointless?.

    On the plus side the cost of rocket launches keeps dropping. Maybe in time it will become viable to prolong the life of satellites by refuelling, but is this the time?

    1. Pangasinan Philippines

      Re: Do satellites need refuelling?

      Just what I was thinking when reading the article.

      However, a high capacity satellite -(with many times frequency re-use) might be deemed to be low capacity after 15 years (full design life) but could be refuelled, re-positioned and sold to less affluent nations or service providers. Maybe direct TV broadcasting over Africa for example.

      A new in-orbit bird that was poorly launched and with low fuel at start of life would benefit from a refuel being cheaper than another new replacement.

      Maybe the Ka birds would benefit most from refuelling as the technology appears to be ahead of the industry demand at the moment and current capacity is under used? (a bit of a guess here)

    2. cray74

      Re: Do satellites need refuelling?

      The idea seems neat, but is there really a need to refuel satellites?

      Most geosynchronous communication satellite lifespans are determined entirely by fuel, which runs out before the other factors you mentioned kill the satellite. After all, a designated orbital slot in geosynchronous orbit is subject to a lot of perturbations and satellites there need 50 to 55m/s of delta-V per year. This is why the aerospace and telecommunications industries are adding nekkid pictures of the Boeing 702SP all-electric satellite bus to their pr0n folders. By using entirely ion propulsion, its fuel endurance and thus time on station is significantly improved.

      Low orbit spy satellites are another group of fuel pigs. They tend to encounter a lot of atmospheric drag and frequently modify their orbits to more quickly pass over a target of interest.

      Its been nearly 60 years since Sputnik and as far as I know nobody has bothered with satellite refuelling

      It was part of the plan for the US shuttle-as-a-space truck. The shuttle was launching up to 3 satellites (several flights launched 3); recovering satellites for repair (STS-41C & STS-51A, 3 total recoveries for repair); repairing satellites in flight (STS-27, STS-49, Hubble missions), and, yes, refueling satellites (STS-41-G). The classified shuttle military missions may have actually refueled spy satellites (e.g., STS-27).

      The plan was there for satellite refueling, but widespread implementation was halted by the Challenger disaster. A lot of plans for satellites altered after Challenger: design for retrieval was almost completely abandoned; refueling was abandoned; satellites mostly stopped being designed for in-flight repair; the US military gradually disengaged itself from shuttles; etc. Now you see satellites designed for the longest possible life, going to extremes like all-electric propulsion.

  2. John Smith 19 Gold badge

    "should be capable of refueling satellites that haven't been designed for the job."

    That makes absolutely no sense.

    The only way they can make this work depends on what the current SOP for fueling satellites is. Most of them will be with the toxic NTO//UDMH combo, the others with Xenon for an ion the tanks are loaded with self sealing 2 part connectors on the skin of the satellite then it can move into position and dock with the bird. But otherwise this is something that's got to designed in from the start, so you need to get someone to do this.

    Running out of station keeping propellant is the cause of comm sats ending life so it's potentially got a lot of market.

    Definitely worth a shot.

    1. willi0000000

      Re: "should be capable of refueling satellites that haven't been designed for the job."

      from what i've seen on NASAs website, designed for refueling means putting the fueling ports in an easily accessible location with some sort of hold-fast for the refueling spacecraft to grab for stability.

      all satellites have fueling ports/valves that are used once just before installation of the satellite on the rocket . . . this should place them in relatively accessible locations, being one of the last things done to the satellite on the ground.

      accessing the fueling ports on orbit is just a bit trickier if not designed for refueling . . . you need more / different types of adapters to accommodate different satellite manufacturers changing standards . . . and probably several additional elbows on the arms as anyone who has ever tried to work on parts under the dashboard of a car knows quite well.

      and refueling even if just for controlled deorbiting would be worth it too . . . although a self-contained propulsion and guidance package for attachment to a dead satellite might be a worthwhile project.

      1. druck Silver badge

        Re: "should be capable of refueling satellites that haven't been designed for the job."

        Before you can even think about what refueling connector to use, you first have to grab hold of the satellite, which is extremely difficult if it hasn't been designed with any handles, and has protruding solar panels and antenna. It was difficult enough for shuttle astronauts to do by hand, so a machine is going to have quite a challenge.

        1. Brewster's Angle Grinder Silver badge

          Re: "should be capable of refueling satellites that haven't been designed for the job."

          " first have to grab hold of the satellite..."

          A big lasso. Because: "space cowboys".

          A clue, ape: astronauts only have two, rather small hands. A robot can have "hands" that are as big (or as small ) as are necessary, and it can have as many as are needed.

  3. Anonymous Coward
    Anonymous Coward

    Cheaper launches? Just hoping Apple don't get into building Satellites.

    Apple will just remove all the ports to prevent refueling of the Satellite and give the Satellite a design life of 2 years rather than 10.

    I can see the day. NASA's Jet Propulsion Lab's: 'Guys, who forget to pack the Apple Satellite Dongle'

    1. phuzz Silver badge

      Re: Cheaper launches? Just hoping Apple don't get into building Satellites.

      "Well, we were going to pack the Apple Satellite Dongle, but it turned out to cost as much as a Shuttle, and you still need the Apple Satellite Dongle to Lightning adaptor, and that's as much as a Delta IV, so we went for this cheap one off Amazon for $20..."

  4. Kevin McMurtrie Silver badge


    The complexity of building a refueling robot, especially one that doesn't make incredibly explosive mistakes, makes inventing new propulsion seem like a good idea. Maybe a way to ionize the air to reduce drag or add a bit of thrust, even if that air is essentially nothing moving at 30000 km/h. Or figure out the EM Drive paradox.

    1. Robert Sneddon

      Re: Yikes

      ESA and the Russians have flown refuelling robots several dozen times quite successfully. The International Space Station has thrusters to provide attitude control and some repositioning capability, to dodge space debris mostly. The Soyuz Progress capsules and the ESA ATV modules both have the capability to transfer fuel to the ISS as well as liquids such as water, ammonia etc.

  5. Kharkov

    This is a good idea

    First of all, if satellites aren't designed to be refueled then there is still a way to get fuel back into their tanks... through the rocket nozzle. Feed a flexible (and controllable) pipe in the back end and push it towards the fuel tank. Tricky but (I think... no, I'm not a rocket scientist) doable, surely.

    It helps that the liquids involved aren't cryogenic things like liquid hydrogen or oxygen. Being hypergolic liquids will mean that TWO pipes are needed but still... doable.

    The problem (of course) is the cost of getting a refueling satellite up there. If it costs the same as launching a new, upgraded-design satellite then there's not much point. Secondary payloads on SpaceX launchers?

    But the continual love for the X-37 is really ridiculous. It (only, as far as I know) launches on an (expensive) Atlas V. And if you've get a satellite that can move around to meet other satellites, why add a layer of complexity by putting it inside an X-37? There's no value-added at all.

    1. cray74

      Re: This is a good idea

      First of all, if satellites aren't designed to be refueled then there is still a way to get fuel back into their tanks... through the rocket nozzle.

      Rocket combustion chambers usually aren't fed through simple, single pipes. The space shuttle main engine used a forest of alternating oxidizer pipes surrounded by hydrogen that emerged through hundreds of ports. Tracing back up stream, you'd find the oxygen and hydrogen flows split to the tanks and the turbopump. You wouldn't be able to refill a given propellant tank by sticking a hose up the tailpipe.

      Even in simpler, smaller rockets, there's usually multiple fuel ports and flow paths. Fuel is often used as an engine coolant, spraying from the walls to form a cool "curtain" between the walls and flames. There may also be pre-mixing of oxidizer and fuel, so you can't select a desired destination tank (fuel OR oxidizer).

      1. Alan Brown Silver badge

        Re: This is a good idea

        You're confusing booster rockets with simple low impulse thrusters.

        Once you escape atmospheric drag and the extremely high impulse needed to overcome it, the vast majority of motors use simple hypergolics (and some used simple pressurised cold gas)

        As others have said, almost all satellites have accessible fuelling ports, because they had to be filled up before launch. The hard part is connecting to them in a "weightless" environment without the things simply bouncing off, which means not only to you have to fly up to the bird, you actually have to hold onto it whilst you plug in - and with the antenna/solar panels deployed that can be a pretty delicate manouvure if you want to do it without breaking parts off given the delicacy of parts and inertias involved.

        If you're ever in London, there's an Intelsat with half its antenna deployed on display in the science museum (the other is furled). Think of a butterfly and the fragility of its wings and you won't be too far off.

    2. John Brown (no body) Silver badge

      Re: This is a good idea

      "there is still a way to get fuel back into their tanks... through the rocket nozzle."

      Nice idea. Come back when you can do that with a car here on Earth and we'll talk :-)

  6. Winkypop Silver badge

    OK Satelite K2123B7, your refuel is now complete

    Would you like 2 chocolate bars for $3 ?

    1. John Brown (no body) Silver badge

      Re: OK Satelite K2123B7, your refuel is now complete

      ...and free whisky tumbler.

  7. JJKing Silver badge
    Thumb Up

    Fuel for thought.

    Here's hoping they put a refuelling port on the refueller.

    I hope they also can refuel the old satellites and force them out of orbit sooner either by burning up during re-entry or shooting them off to the sun. There is a lot of metal spinning round this planet. At some stage it is going to be too cluttered to launch new stuff. Maybe they could be parked near the moon and used as raw material for Starbase Alpha.

    Now if someone would just make a machine that would hoover up all the tiny bits from collisions and other acts of destruction. Any country that destroys a satellite in orbit should have squid and condensed milk put into the door sills of all their vehicles as a punishment and left there all during the summer.

    1. MrXavia

      Re: Fuel for thought.

      De-Orbiting anything seems foolish.... all that raw material ripe for building with...

      I like the idea of a space cleaner, collecting old rubbish, taking it to an orbital factory to be reduced down to its raw materials.... Power isn't a problem if you have enough solar panels...

      1. Martin Budden Bronze badge

        Re: Fuel for thought.

        "Power isn't a problem if you have enough solar panels..."

        Luckily, when you collect lots of old satellites you get to keep all their solar panels :-)

  8. TRT Silver badge

    Can't help but think of Lev Andropov...

    I am not gas station. This is sophisticated laboratory.

  9. Michael H.F. Wilkinson Silver badge

    Interesting idea if they can pull it off

    It is going to be quite a challenge (but hey, they are rocket scientists, after all)

  10. ElectricFox

    EM Drive

    Unfortunately, the inventor of the EM Drive appears to have jumped the shark:

    He's shifted focus from "our-current-model-of-physics-violating space propulsion" (which would do away with the need for propellant) to raving about the realms of flying cars. If you put kilowatts of power into the most sensitive measuring equipment available to science, then you're going to measure something.

    Icon, because I want to believe.

  11. MisterNineThousand

    What makes this an interesting thing is the economics!

    Matching orbits and docking are both pretty fuel intensive, so it'll likely burn more fuel getting on target than it'll actually deliver, esp since the way the rocket equation punishes doing all your burns with a full fuel tank. IF they can make it 100% reusable and there is a large fuel depot in LEO that it can dock with to refuel itself, then zip out on it's next delivery, I can totally see this being a lot cheaper than replacement satellites.

    Assuming that a large comsat is 50% fuel and it burns as much fuel getting on target as it delivers, it would work out to the same launch mass as replacing a sat, and I assume even expensive fuel is cheaper per kilo than satellite dry mass.

    Bonus if the world wide launch cadence picks up enough that there is a second class freight option to send up orbital fuel depot fuel on any launches that have a few hundred kilos of spare capacity.

    1. Marcelo Rodrigues

      "Matching orbits and docking are both pretty fuel intensive..."

      A robotic refueler would have the luxury of endurance. Use a low delta V, take your time, and save on fuel.

      1. Robert Sneddon

        It doesn't work that way

        Delta V is the total change in velocity of an object, its vector as well as its speed. A low delta V means the robot wouldn't get to its required position in space travelling at the correct speed in the correct direction (vector).

        A rocket motor produces a given amount of thrust per unit of fuel and oxidiser burned, the so-called specific impulse (Isp). Using it up slowly or quickly doesn't make a difference to the total amount of fuel needed to rendezvous with a target, at least in free flight in space where air friction etc. is not a factor.

        Electric thrusters like ion engines are very efficient in terms of Isp but they have very low thrust -- the engine that propelled the SMART 1 probe to the Moon had an Isp of about 1600, more than four times the best chemical rocket engines but it could only generate 68 milliNewtons of force using xenon as fuel.

        1. ArrZarr Silver badge

          Re: It doesn't work that way

          "it could only generate 68 milliNewtons of force"

          That was one dedicated KSP player to sit there all that time.

    2. Alan Brown Silver badge

      "it'll likely burn more fuel getting on target than it'll actually deliver"

      That doesn't matter. Fuel is cheap. You can manoeuvre and get there using electric thrusters

      The vast majority of a launched satellite's mass is.... satellite. They generally only have a few kg of fuel (up to a few tens of kg of fuel)

      If you can get 8 tons to GEO then you can refuel a couple of dozen birds and effectively double their lifespans AND bring the refueller back down or park it in graveyard orbit

      It'd be even more interesting if you could plug in extender tanks. It may even be possible to clip on retrofit electric thrusters to older birds.

      More important than all that is the possibility of getting out there and removing dead GEO birds to graveyard orbit because THEY are the reason that all the live ones are expending so much high thrust manoeuvring fuel each year to avoid the stuff precessing through the Clarke belt (stationkeeping can mostly be done on ion drives). This would be an extremely useful final mission for a refueller.

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