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On Orbital Fuel Stations 152

Posted by Zonk
from the complete-with-nukable-burritos dept.
dylanduck writes "Being able to fill up your spacecraft from a fuel depot in orbit round the Earth or Moon is key to the long-term prospects of astronauts exploring the solar system, according to NASA engineers. Trouble is NASA doesn't want to build it themselves. So there's $5 million for any enterprising groups who can develop a simple version themselves."
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On Orbital Fuel Stations

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  • It's doable (Score:4, Insightful)

    by PatrickThomson (712694) on Saturday June 03, 2006 @07:40AM (#15461000)
    Obviously you need atoms up there, which have to come from somewhere, but splitting them into fuel is easy, you're floating in space with all this sunlight. The problem is that if you carry a kilo of water from the surface and then swap it for a kilo of hydrogen/oxygen when you get to space, the benefits are minimal (easier storage?). This would work well coupled with a captured icy asteroid, even a small one.
    • Given the mass ratio between anything we can send up and the average icy space rock, it's more likely the icy asteroid's gravity will capture the craft than the other way around. Not that it's a bad thing, mind you.
      • Given the mass of a space station or an asteriod, the attraction of gravity really wouldn't have any real noticeable pull on either object. The asteroid would have to be ginourmous, and therefore unmanageable to have any real pull and I think at that point they start calling them small planets.
    • Problem is, there's a word for those once they get about as close to the sun as Jupiter, they're called COMETS. That Presents Something of a difficulty, particularly with maneuverability.

      I would suggest fuel might be more likely to come from either: the moon, or a rocky asteroid, by chemically breaking down rock matrices. Of course, to do that efficiently might require something a bit more energetic than sunlight, one might want to go whole hog for nuclear fission (fusion) reactors.

  • Hmmm (Score:5, Insightful)

    by hyfe (641811) on Saturday June 03, 2006 @07:45AM (#15461007)
    Erm, you still have to get the fuel up there right? .. and the cost of putting something up there is still reasonably proportional to weight?

    So sure, once you get liquid hydrogen from the moon / some other energy source it'd be usefull.. which pretty much means we need a moonbase first.

    • Re:Hmmm (Score:5, Funny)

      by Funkcikle (630170) on Saturday June 03, 2006 @07:59AM (#15461045)
      "$9 a gallon? Let's just orbit a bit longer till we find a cheaper one."
    • Re:Hmmm (Score:4, Insightful)

      by MichaelSmith (789609) on Saturday June 03, 2006 @08:12AM (#15461071) Homepage Journal
      Erm, you still have to get the fuel up there right? .. and the cost of putting something up there is still reasonably proportional to weight?

      Fuel depots make sense for aircraft on Earth because you can use cheap surface transport to deliver the fuel, store it, and then load it into your aircraft when needed.

      This might work in space if you have ion powered slow boats to ship the heavy stuff, and fast human carrying vehicles to load up on fuel. But we are not that advanced yet. If we go to mars any time soon it might make sense to launch the cruise stage unmanned and then hook it to the command module in earth orbit. That would be a kind of fuel dump.

      • Re:Hmmm (Score:4, Informative)

        by NOLAChief (646613) on Saturday June 03, 2006 @02:11PM (#15462503)
        If we go to mars any time soon it might make sense to launch the cruise stage unmanned and then hook it to the command module in earth orbit. That would be a kind of fuel dump.

        Effectively that's what's being planned with the earth departure stage for the proposed lunar missions. That stage would be launched on the Cargo Launch Vehicle into earth orbit, where a CEV launch would rendezvous with it for a trip to the moon. See the Project Constellation [wikipedia.org] article here.

    • Re:Hmmm (Score:4, Interesting)

      by Darkman, Walkin Dude (707389) on Saturday June 03, 2006 @08:36AM (#15461106) Homepage

      There might be methods whereby you wouldn't need to carry the fuel with you, for example with a space elevator. However, just what advantages would a space elevator offer over a tower launch? (I've used parts of this post before, but I have since refined my ideas). I contacted a man responsible for a similar idea a while back, the skyramp [skyramp.org] (warning: hideous javascript menu may break firefox), Carlton Meyer, and had a dialogue in which he pointed me to a tower launch archive [yarchive.net].

      The ideas I see bandied about there are similar to what I had in mind, which would be essentially an 11km tall tower (think pylons rather than skyscrapers, based at sea), with evacuated airless launch tubes, using nuclear reactors to power a maglev or pulley system to accelerate vessels to escape velocity. These would then emerge above the end of the troposphere [gatech.edu], with it's associated weather and air pressure, and have little to no fuel needed to match the earth's gravity, meaning you could do a lot more while you were up there. At a reasonable acceleration (5 to 7 g's) you would be in geostationary orbit. From there you could build a fully system wide ship or ships, as its much easier to escape the planet's gravity from GEO than from the surface.

      Not only would this enable multiple launches daily, it is, unlike the space elevator, readily achievable with today's technology, and financially viable as well. Given NASA had an annual budget of $16.2 billion for 2005 [space.com], and a nuclear power plant costs a cool billion to build, give or take, we could have this up and running in a few years.

      • Re:Hmmm (Score:3, Insightful)

        by cnettel (836611)
        I somehow imagine that the pylon construction could be far more expensive than the power plant part.
        • I am not sure, myself. However even if it cost ten times more, it would still be less than NASA's 2005 budget. There ain't much you can't do with 15 billion.

          • Re:Hmmm (Score:2, Insightful)

            by adam1234 (696497)
            Most of NASA's budget inevitably goes to people (ie, payroll) and bureaucratic oversight, not operations.
          • You'd be suprised how fast 15 billion can go when you're talking massive amounts of construction. For example, This article [bostonherald.com] puts a 1,000 foot tower at 1-1.5 Billion.

            You're talking about building a structure 33 times as tall, tight enough to hold a reasonable vacuum, associated power plant, etc...
            • And the big dig in Boston cost 10 odd billion. Kindly read all the links before responding, thanks.

              • Big Dig cost an estimated ~$15B, if you want to get closer to reality.
                For a three and a half mile tunnel.
                That is over $800,000 per FOOT of tunnel. Holy crap.

                Talk about corruption and blatant theft ... Boston - the best government money can buy.
              • 1. The dig had to have a minimal environmental impact -- enough to satisfy Cambridge and the Cape.

                2. The tunnel has to go through reclaimed swamp silt. For a significant part of it, they had to drill holes and fit pipes into the ground in an area, then pump a supercooled solution (not sure if they used saltwater or glycol) through the pipes and freeze the ground hard enough to dig through as they placed the tunnel.

                3. The tunnel has to go through the center of a major city which is the economic engine fo
              • Which links? I looked at three of the ones you posted way earlier, one was bad, two didn't mention the big dig. I did read about the carbon fiber tower, and the other was about a ground rail launch, not going up 11km or whatever.

                I suggest you stop spouting 'read all links' all the time, unless it's just up a post or so. At least specify the correct link.

                For that matter, a carbon fiber tower is likely going to end up in the trillions for cost, once you factor in the cost of mounting the launching system.
                • Nope, materials cost for a carbon fibre tower 1800km tall would be 80 billion, so you aren't talking costing the earth. Then you have construction costs, insurance fees, permits and labour, but I mean, who said we should build it in America? Hell build it in international waters you could declare it your own nation. In any case the initial costs, however steep, are always going to be dwarfed by the ROI. This is space, baby, space.

                  • ROI from what? I do expect concrete answers.
                    • One single asteroid up there contains about 5 tons of high quality steel for every man, woman, and child on earth. How many more asteroids do you think there are? Algae pods (nutrients, sunlight, and ice are abundant, albeit spread out a bit) to grow biodiesel or refine metals, clone banks to hold replacement organs (eternal life anyone?). Manufactories to process the ores retrieved and shape them into useful products. Biodomes where crops and vat-grown meat can be cultivated. The ultimate removal of all m

                    • Ah yes the "I'll be dead before any that is feasible" reasons, which are really worthless in the near future.

                      One single asteroid up there contains about 5 tons of high quality steel for every man, woman, and child on earth.

                      Which does very little good for me as I'm right now down here and not up there. Bringing down such things is not easy (can't build your reentry vehicles in space for quite a while) and simply dropping them down would incur even more costs. You can't easily process it in space either. In a
                    • Let me expand on the previous post a bit, given a person requires 300lbs of food a year (I assume this is a very conservative estimate) and 15 billion people on earth you need to bring down 4.5e12 pounds of food per year to feed the world. At 200k lbs per flight you'd need to use 22.5 million such flights per year to feed the world. Add in manufactured products and it becomes even worse.

                      The question then becomes where do you get the raw materials from and where do they stuff the garbage. Unless they send al
                    • Ah yes, the hard headed realist who advocates a magical space elevator.

                      Which does very little good for me as I'm right now down here and not up there. Bringing down such things is not easy (can't build your reentry vehicles in space for quite a while) and simply dropping them down would incur even more costs. You can't easily process it in space either. In addition you'd need to overcome the political and technological hurdles of getting a rock that close to earth. Keep in mind that bringing things up wo

                    • Ah yes, the hard headed realist who advocates a magical space elevator.

                      No I simply said that theoretically it has various advantages over your plan. I always find it funny how zealots can never understand that some people aren't like them.

                      I feel like I am talking to myself here. The cost of bringing things up would be much lower with a tower launch, thats the entire point. The whole. Entire. Point.

                      Well you apparently can't read or don't know how much sending things up costs now. In either case I wonder why
                    • That sound you may have heard, that grinding squishy sound, was your pwnage in the last post I made. Your entire post has degenerated into a tantrum of some sort, lacking facts, real responses, any manner of thought, or originality. There are so many holes in what you are saying it would take me the best part of an hour to go through it all, and my time is far more valuable than that. You even mentioned turrursts, and that took some doing. In fact, its boring the shit out of me listening to your ass-gas fl

                    • Well I expected that, it seems whenever a zealot meets reality he goes and finds an excuse to run away. Well enjoy your fantasy.
      • Re:Hmmm (Score:3, Interesting)

        by Eivind (15695)
        Is 11km really enough that you don't need to worry about air-friction emerging from the tube at escape-velocity ? (well almost, you said geosynch orbit. But that is like 90% escape-velocity anyway)

        I very very very much doubt it. Even at 31km you still have 1% of the sea-level air-pressure, and at 9km healthy people can still breathe unaided. (as witnessed by the fact that people have climbed Mt. Everest without oxygen)

        I don't know the air-pressure at 11km, but I'd guess around 15% of that at sea-level.

        • Right, I have discussed it with people who actually have done the math, and what you think diverges wildly from reality. Sorry about that. Escape velocity is waaaay higher than what you need for GEO orbit. And unless you have some actual facts to back up your hypothesising, I'll file it under "s" for speculation. Or maybe "u" for uninformed speculation. And do read the links like a good man.

          • by Eivind (15695)
            You have discussed it with people who have done the math ? How ridicolous do you want to become ?

            Listen, its fairly trivial math. Here, let me help you. I'll do it rigth here in this post.

            First, earth has a radius of about 6375 km (eqautorial), geosynch orbit is about 35700 km above sea-level, which means a circular geosynchronous orbit has a radius of about 42100 km or so.

            Now, to be geosynchronous you need to circle once a day, so you'll have to go 42100*2*3.14 km every 24 hours. This works out to 30

        • by wasted (94866)
          I don't know the air-pressure at 11km, but I'd guess around 15% of that at sea-level.

          I think it is between 20% and 25%, depending upon weather and latitude, based on the heights of the 200hPa and 250hPa pressure surfaces.
      • a tube 11km kept as a vaccum?
        Sure you do this in your big particle accelerators, but there are precious few maglev trains 11km long, never mind running them vertically inside a particle accelerator style environment!

        Maybe this is a case of scaling up current technology, and maybe apollo was just a case of scaling up the v2 rocket, I'm still somewhat sceptical though since we've never built a building 1km tall, never mind 11!
        • Transatlantic vac train tunnel, the research has alredy been done. Google it yourself, I'm too damn sunburned right now. And read the links for gods sake. Buildings 1 mile high were 1950s technology.

        • a tube 11km kept as a vaccum?
          Sure you do this in your big particle accelerators, but there are precious few maglev trains 11km long, never mind running them vertically inside a particle accelerator style environment!


          Translation: It'd be expensive.

          From the proposals I've seen, it's a decent idea. Every pound of fuel you can drop from the vehicle makes it that much cheaper. Not having to deal with atmosphere for the first part, or maybe only the 11km pressure is of great assistance.

          One problem I see is how
          • by AGMW (594303)
            One problem I see is how do you keep the tube evacuated while leaving a clear path for the ship?

            If the top end of the tube was high enough, ie "in space" for whatever values of "in space" are appropriate (ie maybe a lot more than 11km!), maybe the end could just be open, as it is in "space" and therefore actually in a vacuum. You'd need some sort of air-lock (er, vacuum-lock?) at the base to load your next container, but otherwise, the open top would take care of itself!

            er ... maybe?

            • Problem is that it's not actually high enough to be out of all the atmosphere. At 11 miles high(a good deal higher than 11km), around 10% of pressure of sealevel [engineeringtoolbox.com](11 miles is ~58k feet) remains.

              Since gravity is the reason for the pressure increase, if you leave the top open and attempt to evacuate the tupe, you'll have a constant inpour of gas from the top to repressurize the tube. So you'd have to cap it off, somehow designing the cap to not interfere with the launching ship. Don't forget turbulance from
              • Yup, already been over that, an iris airlock covers it nicely. Thats two irises near the top of the tower. One opens to let the ship through, then closes immediately after, the other does the same, but you just evacuate the airlock between launches.

                • Have to be awfully fast irises. You wouldn't need two of them, though, you're not going to get a significant amount of air if the iris is only open for a few seconds. Heck, open it up when the ship pushes enough residual atmosphere up to equalize the pressure.
                  • Well the idea of evacuating the tower is twofold; one is to remove friction drag, the other is to stop shock wave effects weakening the tower structure. This ain't the barrel of a gun here. :D It would also be a lot more difficult to pump air out of the entire tower, as opposed to a small area on the top. As to the speed of the irises, if we can design processors of over 4 gigs commercially, a couple of irises shouldn't stretch our engineering abilities.

      • If you want to go on and on about a space elevator, then you need to start talking about how you will use it to put snake oil for sale in orbit. Space elevator, snake oil, all the same stuff.
      • I think it's the 11km tall tower that's the problem part! The difference is between a ladder planted on the ground, and a rope hanging from a high point. If you can reach the high point by another route and suspend the rope from it, you can have a much higher climbing method.

        Simply put, we have materials which survive tension+torsion much better than the materials which survive compression+torsion. We might be able to build an 11km high structure with current materials, but the structure would be VAST at th
      • However, just what advantages would a space elevator offer over a tower launch?

        A truly reasonable acceleration (read: basically none) although this means a very long ride up (week to GEO). Much safer travel, no massive acceleration or high speeds on either the way up or down. On that note going down doesn't require being a few feet from fiery death. The structure has nicer failure conditions and less mass that can impact if it fails, and is basically impossible to take out. The construction is simpler in ma
        • Much safer travel, no massive acceleration or high speeds on either the way up or down. On that note going down doesn't require being a few feet from fiery death. The structure has nicer failure conditions and less mass that can impact if it fails, and is basically impossible to take out. The construction is simpler in many ways if the correct material is found, both in the elevator itself and the actual "construction".

          But your shortfall there is that we have not and may never have the neccessary materi

          • But your shortfall there is that we have not and may never have the neccessary materials.

            Such a venture is not realistic or profitable for at least another 30 to 40 years so we can wait. Theoretically such a material is possible using carbon nanotubes and we'll probably know in 40 years if it is actually possible.

            Well we may as well shelve the whole space program then, in case "shit happens".

            The space program is a very limited, government owned, highly selective and highly unprofitable venture. This is ver
            • Such a venture is not realistic or profitable for at least another 30 to 40 years so we can wait. Theoretically such a material is possible using carbon nanotubes and we'll probably know in 40 years if it is actually possible.

              Or possibly 300 to 400 years. Or never. Magical imaginary materials are all well and good, but honestly, I wouldn't trust my weight to them.

              If you lose 1% of your launches you're not going to get many engineers to go up there and build your space based infrastructure.

              They al

    • and the cost of putting something up there is still reasonably proportional to weight?

      I think it's more than proportional, acually. For every piece of luggage you want to put up there, you need some amount of energy. That energy comes from fuel, which in itself adds to the total mass, thus requiring even more fuel. The fuel can quickly become the largest part of your spacecraft. Look for example at a NASA shuttle at the launch pad [wikipedia.org]. As you probably know, the orange thing just contains fuel, and the two sol

      • I think it's more than proportional, acually. For every piece of luggage you want to put up there, you need some amount of energy.

        On the other hand, air-resistance grows less than proportionally with weight, although I guess that's less by several factors...
        .. damn I wish I had done more actual physics calculations. I don't have any sense of proportion :/

    • by Soft (266615)

      Erm, you still have to get the fuel up there right? .. and the cost of putting something up there is still reasonably proportional to weight?

      True, it doesn't save money in the short run. But even if all that fuel still comes from Earth, it lowers the minimum mass per launch. So you can use many light boosters to supply the fuel depot instead of a few heavy ones. Some people believe that the current high cost of launches is due to a low launch rate (maybe only 10-20 a year, worldwide), and increasin

    • Not necessarily. (Score:3, Interesting)

      by WindBourne (631190)
      Assume it is water to be split. First it has easy requirements for storage. Compared to h2 and o2, it is positively trivial to store and work with (in liquid and solid form). 2'nd, this does not need to be shot up there. It could also be shot up an electronic railgun, or a maglev, to get the initial acceleration. It should be possible to get it going into top subsonic and then allow a much smaller rocket to take it up. Nice advantage of this, is that it could be used on a continutal basis for other cargo th
      • A lot of people are suggesting using water, either launched up or from icy body capture (comet, asteroid, whatever) and then separating the two via electrolysis. Great idea, since water is much easier to work with and store, but once you have separated it into H2 and O2, those gases must be liquefied to be usable by most rocket engines. Liquefaction is a very energy intensive process, particularly for hydrogen, so suddenly the depot's energy requirements have gone up, plus you have to have space for water
    • Erm, you still have to get the fuel up there right? .. and the cost of putting something up there is still reasonably proportional to weight?

      Only for loose values of "reasonably". Other important factors include:

      Required reliability - if an expendable launcher is 50% as expensive but only 95% as reliable, then it's worthless for launching humans, undesirable for precious cargo, but fantastic for fuel.

      Flexibility with existing launch vehicles - if your mass budget for a mission creeps up to 10% more than yo
    • by XNormal (8617)
      Erm, you still have to get the fuel up there right? .. and the cost of putting something up there is still reasonably proportional to weight?

      The nice thing about fuel is that unlike people or equipment you don't really care how it gets there: lots of small launches or a few bigger launches, high Gs or a gentle ride, expendable or reusable, winged or VTVL, high or low reliability. Whatever.

      Some people claim launch costs can be reduced by somewhere between one and two orders of magnitude using only existing t
    • Presumably you could just fire a reusable rocket at the station carrying nothing but fuel (ie: no astronauts, satellites, robots, space weapons, toxic/nuclear waste, orphans, or toupees for the hole in the ozone layer). Then that fuel is available to vehicles that are laden down with those things, allowing those craft to be slightly smaller because they initially only have to carry their launch fuel.

      Not being an engineer, or even a particularly practical mathematician (but ask me about finite automata!

  • by Kaptain_Korolev (848551) on Saturday June 03, 2006 @07:52AM (#15461025)
    Honestly, have we learnt nothing from Jerry Bruckheimer's excellent film Armageddon.

    Refuelling in orbit is dangerous!

    Next they'll be suggesting we man these orbital filling stations with drunken Russians. I only hope Ben and Bruce are there to sort things out when matters go awry.
  • by holdenholden (961300) on Saturday June 03, 2006 @07:58AM (#15461043)
    I say good for NASA. They are finally starting to realize that science can be done outside the government laboratories too. An (academic-type) researcher wastes plenty of time begging for money, writing grants and often balancing a teaching load. In industry, on the other hand, you worry less about budgets and more about what you are trying to achieve and how to achieve it. There is a flip side as well--in academia you are free to work on pretty much anything you like, while in industry you work on whatever your manager wants you to work. In the happy case when your interests and the company's interests coincide, you are only limited by your skills and your knowledge.

    Space One proved that a competition with a good incentive can produce results faster than state sponsored research. I hope the trend will continue.

    • Actually, the article summary is a little misleading.

      NASA's role has always been vision, specification, oversight, and operations. Design and construction have always been contracted out to the public sector, and to the universities.

      Classic examples of this method are the Gemini and Apollo projects. NASA's document, Chariots for Apollo [nasa.gov] gives a fascinating account of how this process works.
  • Zero Gee problems? (Score:4, Insightful)

    by Cicero382 (913621) <clancyj@@@tiscali...co...uk> on Saturday June 03, 2006 @08:12AM (#15461070)
    Has anyone else noticed that zero G is a constant PITA for nearly all space applications?

    A short list includes:

    Human health (bones, muscles, fluid accumulation etc)
    Environment (air flow, hygeine)
    Fluids in general (measuring, pumping)
    Going to the toilet (or john)

    And lots of others.

    I have a question: Why aren't we putting some effort into artificial gravity? I mean centrifuge effects - not Star Trek. After all, we're expending all this effort into individual engineering solutions for each problem. If we had AG of some sort, wouldn't that remove the need for that?

    Just my 2 pennies worth.
    • I think a significant aspect here is the size needed to get a reasonably large volume/area with somewhat consistent perceived gravity (preferably close to 1 g, as well). We simply don't build things that large. When we do, I don't see any big technical problems, but of course one can start to consider proper docking protocols and so on at that point. (Problematic if anyone gets the crazy idea to try to dock the rotating parts of two art-grav vessels with a mismatch in angular velocity.)
    • by GroeFaZ (850443) on Saturday June 03, 2006 @09:09AM (#15461214)
      Obviously, the cost-benefit-analysis, at the current state of technology, does not speak in favor of simulated gravity or the engineers would've done it already. Rocket engineers must justify every pound of mass they want to put into space (which is, by the way, an argument against manned space flight), and, while needless to say, it's just a LOT easier and cheaper to let an astronaut pee into a plastic bag and toss it out the window than designing the rocket with 2 huge rotating discs tens of meters in diameter. Ditto for all other points you mentioned.

      If and when our technology has matured enough so we can start designing RAMA-style spaceships [wikipedia.org] or large spacestations with permanent crews of dozens or hundreds, then this or another kind of AG will certainly be included.
    • No one is taking long-term human space exploration seroiusly yet. The Americans haven't even been to the Moon since 1972, and no one else has ever been.

      It will either take commercial space exploration or another cold war type space race between superpowers before anything actually gets done.

      At the moment, there is no commercial incentive to "explore" anything other than communication satellites.

      If China were to decide to establish a permanently manned lunar colony, I could imagine that the Americans woul

    • It's not as bad as people think. You need a long cable, with a good tensile strength to weight ratio. A simple steel cable will do. On one end you attach the space station, which could be as small as a single module of the current space station. The other end needs a weight, supplies, another half of the space station, space junk... whatever. Then you spin the thing. No big deal.

      To dock, you pull up to the middle and grab old of the rotating cable. You then lower yourself down to the station, and ent
    • ...(or john)...

      Geez, there are already Johns and Hos in space even before the first space hotel is launched???
    • Even if you conquer Zero Gee with Artificial Gravity, you haven't entirely solved the Toilets in Space problem. Especially when it comes to filling stations in space. After all, filling stations on earth often don't have the cleanest toilets. How are we going to keep them cleaner in space?

      Wait, don't say it! I'm one orbit ahead of you... Illegal aliens: Doing the jobs our astronauts (and filling station attendants) won't do.

    • Yeah, Zero G can be a boon and a bane, it has positive and negative aspects.

      I think building a spacedock at La Grange point L1 is the best idea, and a moonbase to get most of the materials for the spacedock, and intrastellar craft.

      Also satellites built and launched from the spacedock/moonbase would have a lower cost to put in high earth geosynch orbit.

      Although Stratallites are probably and even cheaper and easier to maintain scenario vs. satellites. http://www.21stcenturyairships.com/AirshipFAQ [21stcenturyairships.com]
  • by Tx (96709)
    Well, maybe not. But I have to wonder, why not just store the water, instead of separating it and storing liquid oxygen and hydrogen? You've got plenty of energy available up there from sunlight, so you should be able to split the stuff when it's needed, thus avoiding the problems of storing the liquid gases long term.

    So my winning design is a huge ice bucket attached to a big set of solar panels, some electrodes, and some cryo-pumps (ok don't actually know what cryo-pumps are, but they sound like the cool)
    • Well.... if we're thinking big... If a Space Elevator is "feasable" assuming carbon nanotubes happen properly, why not a geosychronous fuel station that pumps water up from the ocean? Think of a big pump in space, with a firehose all the way to Earth. OK, I'll admit that it's a large amount of liquid to lift vertically, tonnes and tonnes and tonnes, but possibly a nuclear generator could provide current for the pumping engines (or some kind of temperature difference pump...?) and/or solar power to split the
  • Delivering Fuel (Score:5, Interesting)

    by DanielRavenNest (107550) on Saturday June 03, 2006 @08:36AM (#15461109)
    When I worked at Boeing, I was in charge of a fuel-depot study.
    The method we looked at was a BFG to launch the fuel into orbit.
    The big gun used hydrogen gas that is quickly heated in a heat
    exchanger, then pushes a 600 kg projectile to 2/3 of orbital
    speed. The projectile uses some onboard fuel to go the rest
    of the way to orbit, then delivers the remaining 100 kg of fuel
    to the orbital gas station. The projectile de-orbits and is
    recovered to be reused. The projectile is rugged enough that
    it can land on anything without damage.

    The big gun is very cheap ($100M) compared to electromagnetic
    launchers, because it is basically a length of pipe, compared
    to a series of coils, switches, and big power supplies. On the
    other hand, it is more expensive to operate.

    The velocity split between the gun and the projectile depends
    on the size of the projectile and how much traffic there is to
    orbit. For the case we were studying, delivering fuel to
    carry comsats to GEO, we were launching 100 kg a day, or 30 tons/yr
    (allowing for downtime).

    DRN
    • "The projectile is rugged enough that it can land on anything without damage."

      Without damage to WHAT? But, ok, there are lots of sparsely populated places, in addition to open sea, but it's not like you can just ignore the damage at return, even if it's not your projectile that is damaged.

    • Re:Delivering Fuel (Score:5, Interesting)

      by rufty_tufty (888596) on Saturday June 03, 2006 @10:42AM (#15461570) Homepage
      Attempt to use BFG to get into orbit - mostly successful, damn politics though.
      http://www.astronautix.com/articles/abroject.htm [astronautix.com]
    • Re:Delivering Fuel (Score:2, Interesting)

      by tarpitcod (822436)
      I wonder if it is feasible to fire a solid block of ice (projectile shaped) into orbit. I wonder how much would ablate due to frictional heating. If you use a large enough electrical arc at the base you could use some of the ice of the projectile as the reaction mass.

      The density is obviously lower than liquid water - but theres no throw away / reuse of the casing required.

      Making the projectiles would require freezing water into the projectile form. It may be cost effective to make a larger solid ice proj
  • The article says one of the problems is figuring out how much fuel you have in zero G because it's all floating around inside the tank. Call me crazy, but can't you just rotate your station and then check the pressure on the inside walls of the tank? Not like centrifugal force is some newfangled idea or anything. It's not like it would even have to rotate particularly fast. Sheesh, do I have to figure out everything for these guys?
  • I doubt there will ever be a cheap/easy/affordable way to do this with chemical reaction rockets. If there was it would have been thunked up by now, doncha think? What you see is what ya get, big ole rockets carrying a relatively small amount of stuff up at great cost.

    We won't become much of a space faring race until we have *advanced physics drives of some sort that work with gravitrons or something along those lines.

    *note:said "advanced". We need to be able to understand and manipulate gravity i
    • Interesting concept, but it would be very difficult to use on current rockets. The structure on most rockets is pretty bare bones to begin with, for example only about 10% of the gross liftoff weight of the Saturn I-B [wikipedia.org] first stage is structure/engines. The rest is fuel. The structure is important because it is what transfers the thrust of the engines from the engines at the aft of the vehicle to the payload at the other end. Having the structure eat itself away as extra fuel would cut this thrust transfe
    • I doubt there will ever be a cheap/easy/affordable way to do this with chemical reaction rockets. If there was it would have been thunked up by now, doncha think?

      It already has been thought of - infact it's been known since the 60's. But there is no economical incentive to implement it - because their aren't enough payloads to make it work. (And of course, without a launcher, there's no reason to create payloads that will use it.)

      This cruel chicken-and-egg dilemma is what is holding us back.

  • Wouldn't there be a problem with the fuel depot maintaining a stable orbit? As it offloads mass to another vehicle, it seems its orbit should change because of its changing mass. Something to do with conservation of momentum.
    • Re:Orbital Mechanics (Score:2, Informative)

      by solitas (916005)
      By and large, a change in mass shouldn't affect an orbit - speed and altitude (orbital radius) are interdependent. It would affect drag (atmospheric & from the 'solar wind' - less mass = less momentum so drag would slow it down faster), but that's about all.
  • Aren't all the problems the same as those that exist for fuel tanks in spacecraft? In which case, they've already been solved in existing craft, so just modify their fuel tanks.

    I'm sure spacecraft can measure fuel levels in zero g - would seem odd not to be able to. And you have to suck fuel out in just the same was regardless of if it's going to an engine or another fuel tank.
  • Earth's gravity well is at the edge of bichemical propulsion capacity. The best systems to date still only lift less than 10% payload weight of the launch vehicle.

    This fact means that unless rocket technology and materials building became absurdly cheap it will never provide the basis for a massive launch capacity needed for ideas like colonization or even large scale outposts on other planets at anything approaching economicaly viable costs.

    True reuseablity is about the only thing that could make this piti
  • Everybody keeps going back to using water, cracking it via solar electricity into oxygen (gas, or cooled/compressed into a liquid) and hydrogen (again, as a gas, or (unlikely) as a liquid.)

    Where's the actual rocket fuel here? Last I recall, oxygen makes a great fire enabler, but pure oxygen itself doesn't really burn - it makes fire possible, makes fires better - but there needs to be some sort of fuel to burn in the first place. And as for H2 - if memory serves me correctly hydrogen + oxygen + spark does
    • Re:Water? (Score:3, Informative)

      by Larthallor (623891)
      No, hydrogen is explosive. I'm not sure what neat trick you saw, but I would guess it was likely a decrease in pressure after an explosion caused by two gases combining to become a much denser liquid. In other words the container (attached to a balloon?) contained the explosion and then the water vapor condensed lowering the overall pressure.

      Anyway, one of the reasons why to use hydrogen is that the hydrogen/oxygen reaction has an extremely high specific impulse for a chemical rocket. Here [wikipedia.org] is a Wikiped
      • I was going to explain it but I haven't had enough caffeine - so I will simply Google / cut & paste.

        One technical point about Hydrogen. It doesn't explode. It burns, certainly. Very hot, and with a dangerous, invisible flame. However, when hydrogen burns, it combines with oxygen to form water. You would combine 2 moles of H2 and 1 mole of O2 (6 moles of individual atoms) to get 2 moles of H2O - water vapor. Going from 3 moles to 1 mole of volume means that burning hydrogen IMplodes, not explodes.

        It was
  • The T-space consortium already proposed this in their bid for the CEV program. NASA should concentrate on ideas that haven't already been given to them.

    http://www.transformspace.com/ [transformspace.com]
  • we'll send punks with gasoline cans and syphons up there and "liberate" the russian and chinese orbital fuels. heck, with a coat hanger and wire cutters they could even jack spacecraft.

IF I HAD A MINE SHAFT, I don't think I would just abandon it. There's got to be a better way. -- Jack Handley, The New Mexican, 1988.

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