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."

Comments

So...um...

[stillnotelf]

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).

Re:So...um...

[Rich0]

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...

[Impy the Impiuos Imp]

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

Re:So...um...

[Baloroth]

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...

[Baloroth]

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).

Re:So...um...

[Patch86]

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")

How About Calling It RRR

[LifesABeach]

Refuel, Reposition, and Repair

With apologies to AAA.

Civvie version of X37-B

[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.

Re:Civvie version of X37-B

[rossdee]

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

Re:Headline: NASA WANTS MONEY

[K. S. Kyosuke]

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]

Talk about Scope Creep

[Rich0]

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.

Re:Talk about Scope Creep

[tomhath]

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.

Re:Talk about Scope Creep

[thrich81]

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.

Re:Talk about Scope Creep

[Kjella]

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 maybe it will be cheaper. Personally I'm thinking more about big military satellites in low earth orbit that may need this much more often than GEO satellites. It could also put us in a position to do missions bigger than our current launch capability - which may be a very neat trick for say a Mars mission. I doubt we'll be building more Saturn Vs.

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).

So what if it does? They know when the satellites run out, it's not like they one day look at the dashboard and discover they're in the red and need a top up right now. Say a year long mission to top up 10 satellites sound like a perfectly reasonable duration for me. I must admit, I don't see huge wins for this, but it's skills that will only become more valuable the more satellites and things we put up there.

What about my car?

[yog]

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.

Bonkers

[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 ;-)

What about Retiring?

[T_Tauri]

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.

Re:Headline: NASA WANTS MONEY

[SilentStaid]

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

Re:Headline: NASA WANTS MONEY

[GodfatherofSoul]

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!

The orbit, itself

[dpilot]

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.

Re:The orbit, itself

[Clueless Moron]

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.

Re:The orbit, itself

[dpilot]

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.)

Re:Headline: NASA WANTS MONEY

[pguzmang]

http://launiusr.wordpress.com/2012/02/08/why-explore-space-a-1970-letter-to-a-nun-in-africa/

American Worker is Doomed

[SethJohnson]

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