A new spin on Orbital Gas stations?

In a word or two, Engineers at MIT are proposing a novel idea to fuel up in Space using Fuel depots at Lagrange points. How it would work is spacecraft would carry a supply of additional emergency fuel on board. If the emergency fuel isn't used then they would leave it at the Fuel Depot for the next spacecraft to pick up. Another option is spacecraft to spacecraft fueling although that is a bit more tricky.

"The scientists suggest setting up depotsat Lagrange points — regions of space between the Earth, the moon and the sun that maintain gravitational equilibrium. The gravitational pulls of the two large bodies are balanced, so objects at these points keep the same position relative to these two bodies (for example, the Earth and the moon.)"

I'm somewhat bothered by this idea; this idea which has been around for ages and MIT engineers talk about it like it's something new. The article doesn't talk about fueling with respect any of the new propulsion technologies out there, just the old adage of using liquid fuel to explore the neighborhood. I'm all for progress and I'm glad to see that scientists are looking at ways to explore Space but I'm a little concerned with the technology discussed. We could've done orbital depots years ago; I'm frustrated with the baby steps. What say you, ATS?

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I'm not impressed. This sounds like a couple of people sitting at a bar saying, "Y'know what would be cool?" without really thinking it through.

It's nice that they're thinking about the difficulty of transferring fuel between mostly-empty tanks, and wondering about long-term storage of cryogenic liquid oxygen & hydrogen. They're looking at that problem the wrong way - instead of figuring-out temperature control, simply use fuel cells to react the two into water, which can be easily stored for years (and generating electricity in the process, which can also be stored by various means, though in the presence of solar energy only limited by your collector, this is a secondary consideration). When needed, you can use stored/solar electricity to separate the water back into LOX & LH2.

What they are not thinking about - and this is a real killer - is the fact that, to drop-off the so-call contingency-fuel, they will need to rendezvous & dock with the storage depot, and this in itself requires a non-trivial amount of fuel. Changing orbits is expensive in terms of fuel.*

For example, suppose they had had wanted to establish a contingency fuel depot in lunar orbit during Apollo: It would not have worked because each of the landing sites required a different orbit to land & take-off. Neither the lander nor the orbiting command/service module had fuel reserve to switch from one of these orbits to another, and modifying either or both spacecraft to carry that extra fuel would have made them too heavy for the Saturn V rocket to lift.

Similarly, if you put the depot at one of the Lagrange points, the spacecraft still has to shape an orbit to get there, then match orbits, and then burn more fuel to leave the depot's orbit and return to Earth. The lunar L4 & L5 point are both as far from the Earth and Moon as the Earth is from the Moon (they form equilateral triangles). Getting there would require dedicated missions lasting several days. This is much, much more involved than "Hey, if you don't mind, can you pop by the depot on the way home and drop-off anything you're not using...?"

I don't think that the idea of an orbital depot is a bad one - In fact, if we ever get serious about manned interplanetary space travel, it will be a necessity - but doing it with so-called contingency fuel from missions to anywhere BUT the depot is not in any way practical.

lostbook
The article doesn't talk about fueling with respect any of the new propulsion technologies out there, just the old adage of using liquid fuel to explore the neighborhood.

No matter what propulsion system or energy source you use, you're going to need reaction mass. Newton's Third Law is a bitch.

lostbook
I'm frustrated with the baby steps.

As someone who watched the greatest space transportation infrastructure ever built junked by short-sighted know-nothing luddite political hacks... well, you're preaching to the choir.
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* I thoroughly enjoyed the movie "Gravity" - thought it was great, in fact - but its central plot mechanism (using small thrusts to go from Hubble to ISS to Tiangong) was frankly impossible (almost as much as the Millenium Falcon doing a U-turn in space). The Space Shuttle itself, with a cargo bay full of extra maneuvering fuel, would not have had enough fuel to go between the actual orbits of these objects. Even if you could get the orbits to intersect at the right time, the closing speeds would be hundreds or even thousands of miles-per-hour. The collision... well, it would pretty much be like the one that starts the whole drama at the beginning of the movie.

reply to post by lostbook


If it is truly that simple then we should have used the retired Space shuttle Fleet to get the ball rolling.

@ Saint and his star wars reference -
I think this one is more on target -

"You've never heard of the Millennium Falcon?…It's the ship that made the Kessel Run in less than twelve parsecs."

I'm frustrated with the baby steps. What say you, ATS?

we're still dicking around with internal combustion engines more than a century after they've been invented
back in the 60's and 70's some interesting # happened
but most people saw that as "thunderbirds" and "sea-quest"

UNIT76

I'm frustrated with the baby steps. What say you, ATS?

we're still dicking around with internal combustion engines more than a century after they've been invented
back in the 60's and 70's some interesting # happened
but most people saw that as "thunderbirds" and "sea-quest"

Got anything better than conventional engines? Let's see them!

reply to post by wildespace


..you asking me to reinvent the wheel?
what i'm saying is, there are much better ways to make them move around

reply to post by lostbook


Using tons of fuel so to propel some fuel into space. Hm, I dunno, but in my mind it'd be less of a hassle (and of an irony) to develop ions thrusters and use the Sun as energy source.

S&F for the find, though.

reply to post by swanne

Ion thrusters work great in space, if you have a lot of time to deal with the low acceleration.

Interesting idea though. I guess if you could sustain enough thrust to overcome the weight of the vehicle you could, very slowly get far enough away so that gravity would become less of a problem. Trouble is, the best ion thrusters we've got give less than 1 Newton. That's less than 0.2 pounds of thrust. So, depending on how much your engine weighs, you'd need a whole lot of them to get a person off the ground...slowly. Going to have to get a lot more out of them than we are now.

UNIT76
reply to post by wildespace

 

..you asking me to reinvent the wheel?
what i'm saying is, there are much better ways to make them move around

Humour me. What better ways are there to move around? Ion thrusters provide better acceleration, but over much longer periods of time. Other propulsion methods are theoretical, and seem to be very costly and complicated.

My guess as to why we are still burning fuel, is that fuel is plentiful, relatively cheap, and delivers high acceleration in a short amount of time. Is there something that can beat that?

reply to post by wildespace


humor? ...well, photovoltaic cells for starters
it all hinges on that word "better"..

simply put;
is it "better" to get from point A to point B really-really-really FAST? (and all the inherent dangers that come with it)
or
is it "better" to get there eventually, safely, and without spewing a bunch of carcinogens into the atmosphere?

you mention cost, complications, and things being in the "theoretical" stages
meanwhile there are some interesting things flying around at places like area 51
things joe public isn't in the know about.. but i'm being too glib,

it's not because the fossil fuels are plentiful and/or cheap (we wouldn't be fighting over them)
it more to do with the cartel$ and in$titution$ that are built around these outdated paradigms

i would've stated ion-drives here also (someone beat me to it, it must be well known by now, all this stuff they still claim is in the theoretical stages.. lol, like CERN)
i can make a little device in my home using magnets and have a simple wheel spinning ad infinitum
all these boffins have to do is reproduce this on an atomic scale..

reply to post by UNIT76

Photovoltaic cells provide electricity, not propulsion. You cannot take off from Earth using ion thrusters. Using ion thrusters for manned space exploration will increase exposure time to harmful space radiation. When we finally are going to Mars or asteroids, it's better be done in the shortest possible time.

The bulk of the fuel is used up getting off Earth with its strong gravity and a thick atmosphere, and there's no easy cheap solution for that.

We developed a nuclear engines back in the early 60s or late 50s. The problem is getting off the earth without radiating everything within "X" miles of the launch sight and anything down wind. There was a proposal to make the second stage of the Saturn 5 "nuclear" which would have worked unless there was a crash on take-off.



and of course the Orion which was to use 1000's of small nuclear explosions to propel an ocean liner size space ship to mars...

reply to post by wildespace

Photovoltaic cells provide electricity, not propulsion. You cannot take off from Earth using ion thrusters. Using ion thrusters for manned space exploration will increase exposure time to harmful space radiation. When we finally are going to Mars or asteroids, it's better be done in the shortest possible time. The bulk of the fuel is used up getting off Earth with its strong gravity and a thick atmosphere, and there's no easy cheap solution for that.

that's cute, you think i don't know that these photovoltaic cells just provide power to this propulsion system


it's because they're doing it all on the wrong level, like trying to throw some rock at the moon
you know what i'm talking about, don't you?
we don't hear much about the progress they're making into the microcosmic world and the macrocosmic world
we only see this is products like sunscreen and movies like star wars
not even baby steps really, more like stuck in the cradle


when we're talking about making wheels move, there's much more going on here, think about the atomic world and the reactions that take place and how they effect the 'physical' world


fwiw, i thought the idea of leaving that fuel behind *made sense*, i think that's the whole problem

reply to post by Phage


Yeah, ion thrusters aren't very effective on the ground. People will still need to fuel up with chemical propellants to get off Earth. But then, if you have ion thrusters for space, then one wouldn't need to put gas stations in orbit at Lagrangian points - that was my point. The thrusters could simply use the Sun's energy to re-charge.