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NASA Space Science

Send the ISS To the Moon 387

Posted by kdawson
from the one-of-these-days-alice dept.
jmichaelg writes "Michael Benson is proposing that NASA send the ISS to the moon instead of leaving it in low earth orbit. (While we're at it, we should re-brand it as the 'International Space Ship.') He points out that it's already designed to be moved periodically to higher orbits so instead of just boosting it a few miles, strap on some ion engines and put it in orbit around the moon instead of the earth. That would provide an initial base for the astronauts going to the moon and give the ISS a purpose other than performing yet more studies on the effect of micro gravity on humans. Benson concludes: 'Let's begin the process of turning the ISS from an Earth-orbiting caterpillar into an interplanetary butterfly.'"
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Send the ISS To the Moon

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  • by jamie (78724) * Works for Slashdot <jamie@slashdot.org> on Tuesday July 15, 2008 @03:50PM (#24201881) Journal

    My quick Wikipedia-based calculations are that the ISS could match orbits with the moon in 9.2 years if its solar panels were entirely devoted to powering ion engines.

    (They wouldn't be, of course, and my other major omission is the need to orbit the moon -- I have no idea how the moon's gravity would perturb the ISS as it approached, I suppose it would increase or decrease orbital transfer efficiency but I don't know which.)

    Sources:

    Low-thrust transfer [wikipedia.org] - "going from one circular orbit to another by gradually changing the radius costs a delta-v of simply the absolute value of the difference between the two speeds"

    Ion engine comparisons [wikipedia.org] - 25 kW can produce 1 N thrust

    ISS Solar Arrays [wikipedia.org] - 4 pairs of "wings" to be installed on ISS, totalling 262 kW (I think; might be half that [wikipedia.org] if I misunderstood "wing"); ISS weighs 1 million pounds

    Moon's orbital velocity [wikipedia.org] = 1.0 km/sec, ISS's orbital velocity [wikipedia.org] = 7.7 km/sec

    Google says: 9.2 years [google.com]

  • Lumpy Gravity (Score:5, Informative)

    by Detritus (11846) on Tuesday July 15, 2008 @03:55PM (#24201971) Homepage
    Bad idea. The Moon has a lumpy gravitational field. This makes it very difficult to keep anything in a stable orbit. Look up lunar mascons.
  • by fyngyrz (762201) * on Tuesday July 15, 2008 @03:56PM (#24201977) Homepage Journal

    Because old booster rockets are heavy, and the energy to get them into orbit has to come from somewhere. When we shot a big Apollo, for instance, most of it didn't reach orbit, much less the moon — just fell back to earth. And even then, they were light, empty of fuel. In the end, there was just enough energy available to send a tiny, tiny capsule to the moon.

    What you want to do is put heavy rockets in order with fuel. They have to get there somehow, and contrary to Robinson's optimism, we don't have a viable space elevator anywhere in sight. We'd have to do it the (very) hard way.

    My old friend Tony Splendora likes to say, with regard to physics and fast vehicles, "There are some laws you just can't break." That applies here as well; getting something heavy into orbit is hard.

  • by ogre7299 (229737) <jjtobin@[ ]ch.edu ['umi' in gap]> on Tuesday July 15, 2008 @04:03PM (#24202137)

    The inclination of the ISS orbit is too great with respect to the plane of the solar system. If I remember right it's inclined by 56 degrees to allow the Russian rockets easier access.

    With this orbit it's essentially useless for a "dry dock" since too much energy would have to be expended in changing the inclination to match the solar system.

  • by Free the Cowards (1280296) on Tuesday July 15, 2008 @04:21PM (#24202473)

    The cargo capacity of the shuttle is far too small to even contain the fuel needed for such a mission, much less the fuel plus a bunch of landers. The shuttle orbiter's cargo capacity is only 1/3rd of its empty weight.

  • by jfengel (409917) on Tuesday July 15, 2008 @04:32PM (#24202647) Homepage Journal

    According to the Wiki page (http://en.wikipedia.org/wiki/Michael_Benson), he's an writer and filmmaker. The closest thing he has to a qualification is a book of reprocessed images from space probes.

    Beyond: Visions of the Interplanetary Probes.

    Yes, I'm sure it's the same guy. Both the article and this wiki page cite the same book. Also, the Wiki page says he's "living in Slovenia", and the article includes a .si email address.

  • by Anonymous Coward on Tuesday July 15, 2008 @04:32PM (#24202661)

    Hydrazine is not normally used as a main propellant, it is used for steering thrusters. The Saturn 5s used LOX and LH2 for their oxidizer and fuel.

  • Re:Problems... (Score:5, Informative)

    by SBacks (1286786) on Tuesday July 15, 2008 @04:35PM (#24202717)

    You are correct, it would only need to go as fast as the ISS for a moment. However, this is space we're talking about, and there's nothing to slow you down out there. Going that fast for a microsecond takes as much energy as going that fast for a century.

    And, unfortunately, the ISS would be going its fastest when it was close to Earth, and its slowest somewhere near the moon.

  • Re:Lumpy Gravity (Score:5, Informative)

    by scuba_steve_1 (849912) on Tuesday July 15, 2008 @04:36PM (#24202719)

    Very interesting...and I did Google it...and ii turns out that there are actually four inclinations that allow one to orbit the moon indefinitely: 27Â, 50Â, 76Â, and 86Â

    http://science.nasa.gov/headlines/y2006/06nov_loworbit.htm [nasa.gov]

    Still though, it's an interesting point and a nice read...so thanks for the info.

    Me? I am still going with the lack of radiation shielding as the nail in the coffin. That reason alone makes this guy's idea seem fairly poorly thought out.

  • by scuba_steve_1 (849912) on Tuesday July 15, 2008 @04:45PM (#24202905)

    astrobill wrote:

    As a space physicist and engineer, I praise Mr. Benson's enthusiasm for space exploration. However, I feel compelled to explain to him and the millions of Post readers he was allowed to mislead why his idea to send the International Space Station (ISS) on interplanetary jaunts is wholly unrealistic, and frankly, impossible.

    For one thing, the shielding, wall thicknesses, and many other design aspects of the ISS were chosen to protect crews from the worst-case radiation environment known to exist throughout its present orbital environment. The ISS spends its entire time wholly within the protective cocoon of the Earth's magnetosphere, a complex electromagnetic structure generated within the Earth which also happens to protect the Earth from most forms of high energy cosmic rays and other ionizing particles. The ISS design is wholly unsuitable for long-duration jaunts outside this region and could not easily or practically be changed at this point to accommodate a different environment.

    Secondly, Mr. Benson's proposal to simply connect engines to the ISS and launch it away from Earth and onto interplanetary trajectories completely ignores the fact that every source of propulsion he cites would impart accelerations, even small ones for certain scenarios, that the ISS structure, joints, and arrays simply cannot accommodate -- the structure would simply exceed design tolerances under any source of thrust sufficient to launch it out of Earth orbit and on a transfer trajectory around the Sun to another Solar System body. Moreover, even the low-thrust ion engines Mr. Benson cites (actually, low "specific impulse," but that's another lesson...) would be unable to launch the ISS onto a transfer orbit to another solar system body, and certainly not on any reasonable timescale. It would be, perhaps, years before Mr. Benson's hypothetically-suitable ion engines could impart enough added velocity ("delta-V" to engineers) to move the ISS into an appreciably higher orbit, much less on a suitable trajectory to another planet in our Solar System. The ISS would require thousands of miles per hour of additional velocity to be placed onto such an orbit, regardless of the engine type used.

    Thirdly, Mr. Benson's essay completely ignores the fundamental fact that even the most efficient transfer orbit between Earth and, say, Mars, requires at least 8-9 months each way, not to mention the time spent actually DOING anything once there. The ISS is simply unable to hold enough food, water, air, and other "consumables" for any sized crew for the duration of any mission of the type Mr. Benson has in mind. And "direct" trajectory missions that ignore the more efficient transfer trajectories require so much acceleration that the ISS would simply flex and buckle were an attempt made.

    Forth, the amount of power the ISS solar arrays can generate is fundamentally tied to the solar energy received on their surfaces. Some of the interplanetary bodies Mr. Benson proposes visiting are at locations too far from the Sun for the arrays to generate enough power to operate systems on board. For example, the ISS solar arrays at Mars would receive only about half as much solar energy per square meter as they do at Earth. The ISS simply cannot accommodate hanging enough "extra" solar panels on its structure to make up for the difference, and wiring in new, additional power sources would require wholesale redesign of the ISS.

    There are about a dozen other significant reasons why sending the ISS on interplanetary missions is completely unfeasible from a technical perspective, and which time an space prohibit me from addressing here.

    Mr. Benson's claim that "...there are good answers to all these objections..." and his attempt at preemptive criticism of "skeptics" -- as well his claim that NASA is not "particularly welcoming to outside ideas" -- does not obviate the laws of physics, engineering limitations, much less the laws of astrodynamics and the hostile environment of our solar system.

    And contrary

  • Re:Problems... (Score:5, Informative)

    by Guysmiley777 (880063) on Tuesday July 15, 2008 @04:46PM (#24202913)
    I highly recommend Orbiter [ucl.ac.uk] for anyone really interested in seeing how orbital mechanics work. It's a fun sim (with a steep learning curve), but there's something satisfying about knowing how to figure an orbital engine burn.
  • by Richard_at_work (517087) <richardprice.gmail@com> on Tuesday July 15, 2008 @04:47PM (#24202943)
    Just a slight correction, of the 16 Saturn V rockets built for the Apollo program, 5 Stage 4 components are now in a solar orbit and another 5 made it all the way to the lunar surface.
  • Re:Problems... (Score:2, Informative)

    by atmtarzy (1267802) <ndnjones3@gmai[ ]om ['l.c' in gap]> on Tuesday July 15, 2008 @04:53PM (#24203057)

    I don't think that'd be too difficult, but when you consider that Mars' atmosphere is 95.72% Carbon Dioxide already (Mars Wiki page [wikipedia.org]), I doubt sending additional carbon dioxide is going to do much to increase the temperature.

  • Re:Problems... (Score:4, Informative)

    by mabhatter654 (561290) on Tuesday July 15, 2008 @05:24PM (#24203557)

    You'd want to put it at the earth-moon L4 and L5 Lagrange points. Then it would be equally "uphill" from both bodies, but in a statically stable orbit. Such an orbit would be good for resupply stations and emergency facilities as it would be in space, easier to get to. At the "halfway" point, you need your momentum to continue the journey and need the same momentum to get to the point anyway so you wouldn't want to kill it all slowing down to stop.

    The point would be to put something interesting at these points so we could have regular supply missions.. that means the simple repairs like ISS has had actually get done on time. If we could make fuel ON the Moon we'd greatly benefit from a space-based system and only have to do heavy lifting to get stuff from the earth to the closest space-base. Then we can work on putting bases at the Solar-earth Lagrange points to start exploration.

  • by A nonymous Coward (7548) * on Tuesday July 15, 2008 @05:30PM (#24203671)

    Even Jules Verne got it part right. The ISS would be at its fastest near Earth at its closest point to Earth, ditto for the moon, and at its slowest at the point in between where the gravities cancel each other out. In each direction of travel, it starts to accelerate as soon as one gravity is stronger than the other.

  • Re:Problems... (Score:4, Informative)

    by Timothy Brownawell (627747) <tbrownaw@prjek.net> on Tuesday July 15, 2008 @05:33PM (#24203721) Homepage Journal

    But the new supplies (and container) still end up going just as fast, which means it's still taken just as much energy to accelerate them. Only in this case, the energy comes from slowing down the station, so either you have to speed it back up (just as energy-intensive and therefore expensive as accelerating the supplies beforehand) or it drops into a lower orbit because it's going slower now.

    There's also the minor issue that paint chips going at orbital speeds can punch holes in things, so catching a cargo container at similar speeds would be rather hazardous to your wellbeing.

  • Re:Problems... (Score:5, Informative)

    by AeroIllini (726211) <aeroillini.gmail@com> on Tuesday July 15, 2008 @06:05PM (#24204209)

    I'm not too knowledgeable about this sort of stuff but wouldn't the reaction of the new container being tugged cause the ISS to change it's direction?

    unless that is only the effect on earth due to friction

    Yes it would, if the container was not traveling at the same speed and direction as the ISS, but it happens at the moment of capture, not during the reeling-in period.

    If the container is moving slower than the ISS (which it would be, I'll get to the speeds in a second), then at the moment of capture the wire would impart an impulse force on the ISS, due solely to the inertia of the container. This would slow the ISS down, and would require a reboost burn to get it back up to transfer speed. Once the container and the ISS have reached equal speeds (some speed less than the original ISS speed and greater than the original container speed, proportional to the ratio of masses), then the ISS-container combination are now in orbit as a single object. The line of the orbit is technically at the barycenter of the two object system, and that barycenter will shift slightly as the container is reeled in, but we can safely assume that since the ISS is many orders of magnitude more massive than the container, the barycenter will be very close to the center of the ISS and will not shift an appreciable amount during reel-in.

    Now, speeds. The apogee speed of a lunar transfer orbit is approximately 11 km/s (24,600 mph). This is the speed the ISS would be traveling at close approach to the Earth, and also the maximum speed and minimum altitude of the orbit. The shuttle is capable of launching to an altitude of 217 nautical miles, which in a circular orbit is a speed of about 7.7 km/s (17,160 mph). The ISS would have to catch a wire traveling at a relative speed of 3.3 km/s (7,440 mph), and the rebound in the cable alone would doom the ISS, not to mention the tremendous stresses placed on both objects to essentially accelerate the container to that speed in the space of a second or so. Capture from two different orbits is simply not feasible; it's much safer to have both objects traveling at the same speed in the same direction for capture, and if you have to boost the container to a lunar transfer orbit speed, you have just used the same amount of energy as simply sending it to the moon.

    IAARS (I Am A Rocket Scientist)

  • Re:Problems... (Score:5, Informative)

    by Miamicanes (730264) on Tuesday July 15, 2008 @07:27PM (#24205459)

    One thing that probably needs to be mentioned, since it's not necessarily obvious to anyone who hasn't taken physics: spacecraft in their current incarnation don't use their engines to keep them moving... they use their engines to rapidly propel themselves to a speed that's hopefully sufficient to reach their final destination (or next gravity waypoint) before the Earth's own gravity manages to pull them back. The shuttle & ISS fire their engines to alter their orbits and nudge themselves around, but once the shuttle is in orbit, it ALREADY has to be going in the right direction at the right speed to eventually rendezvous with the ISS. If there were another space station at a higher altitude, the current shuttle couldn't visit the ISS, then go visit space station #2... at least, not without refueling somehow, because it doesn't carry enough fuel to radically alter its orbit to a higher destination.

    That's the main reason why using the shuttle to service Hubble is so dangerous... it has to use most of its fuel to get there, and literally returns to Earth "on the fumes" (so to speak). Think of it as driving up a road along the side of a mountain in a car with mostly-empty gas tank, with *just* enough fuel to make it to the top... then using that final bit of gas to turn around, and coast all the way back down the mountain. If the shuttle encounters a serious problem en route to Hubble, it doesn't have enough fuel to reach the ISS, and no spacecraft already docked at the ISS has enough fuel left to reach the imperiled shuttle, so there's no metaphorical "tow truck" to rescue them.

    It's also the reason why spacecraft have to rapidly accelerate to multiple Gees, instead of taking off like a jet and just circling the Earth over and over, getting a little higher each time. When the solid rocket boosters are ignited, they burn in a predictable way, but there's no way to gracefully throttle them "up". They do their thing, run out of fuel, and quit -- hopefully (and by design) after the shuttle is already going fast enough for the liquid fueled engines to get it the rest of the way to its destination.

    That's one reason why nuclear engines were so eagerly explored during the 60s... they were the only potentially-viable way to achieve the kind of slow, steady, long-term acceleration that would have permitted a "space plane" to take off and slowly travel to orbit without subjecting its passengers to the usual Gee forces experienced by astronauts. Unfortunately, when you've got a populated planet below with lots of high-value real estate and residents below, nuclear-fired jet/rocket engines just aren't going to happen. People get neurotic about the use of RPGs, which are basically sealed nuclear batteries that generate heat from their own decay and generate electricity using technology that works not unlike solar cells (but with heat, rather than light)... and they probably WOULD make it safely back to Earth if something went wrong on the way up. As such, a real, honest-to-got nuclear REACTOR running at full-bore in a moving vehicle flying anywhere near anything resembling a populated area just isn't going to happen ;-)

  • by LeandroTLZ (1163617) on Tuesday July 15, 2008 @08:46PM (#24206313) Homepage Journal

    One thing that I've wondered is why can't the space shuttles be refit for moon missions?

    For the same reason my bicycle can't compete in a NASCAR race.

  • Re:Problems... (Score:2, Informative)

    by p3d0 (42270) on Tuesday July 15, 2008 @11:05PM (#24207701)

    What if the wire was a big spring?

    Can you picture a speed of 2 miles per second? Can you imagine a car 2 miles away, then one second later it's next to you, then one second later it's 2 miles away again?

    Now, just how big a "spring" would you want to use to try to catch that car?

  • by lordofthechia (598872) on Tuesday July 15, 2008 @11:49PM (#24208013)

    This is slashdot and I think it's safe to assume he's joking, now the general population though would raise that as a valid question. Just look at the movie "Mission to Mars" (or don't, it blows). Lets just say that if the writers knew a little about physics they would have known that one of the main characters didn't have to die...

    After all, if someone was tumbling in space and you accelerated to start to catch up to them, the moment you start to close the gap you are already going faster than them and will close the gap (and even overtake them!) in due time. God, I want that hour and a half of my life back...

Those who do things in a noble spirit of self-sacrifice are to be avoided at all costs. -- N. Alexander.

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