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Space

Going To Space Inside Magnetic Bubbles 230

Posted by timothy from the let's-honeymoon-in-space dept.
Ecyrd writes: "Those fine guys at NASA have figured out a way to hitch rides to space inside magnetic bubbles, creating both an efficient propulsion system and protection from high-energy particles. Sorta taking the Earth's magnetosphere with you as a protective cloak when you go." The propulsion in this case comes not from within, but by using the magnetic bubble as a giant solar sail.
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Going To Space Inside Magnetic Bubbles More

Going To Space Inside Magnetic Bubbles

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  • How the hell do you make it slow down? Even if you never touched an atmosphere, you'd still need big, bulky engines to slow down so you don't splat yourself into wherever it is you're going. And it may deflect solar flares, but it damn sure isn't going to deflect a head-on collusion with anythign solid.
  • No, you can't tack. Tacking with a sailboat uses the force of the water to keep it bouyant and at an angle. In space you don't have that force because its space. The only way you could "tack" is if you have thrust. In that case, you might as well not use a magnetic field since it would be an opposing force. The thrust you would need to generate to tack would produce an unoptimal usage of resources to get where you wanted to go.

    As for using an "unbalanced" magenetic field, well that would just cause you to spin and move in the direction of the wind.
  • The sun can't be the only thing out there exerting solar wind. Even so, though, how would you get back home? Or how do you even slow down?

    They may be going for a trial in 2001, but there was no mention at all of getting back to earth, or even slowing down (or steering!) mentioned in the article at all ...
  • Anyone every read H.G. Wells...The First Men in the Moon? I'll bet he is rolling in his grave right now...
  • I don't want to go backward in life, I want to go forward! To hell with reverse...

    Especially with the quality of posts (noting this one as a prime example)... I'm on the next Magno-Bubble off this hunk of dirt. I'll realize my dream of starting Internet2 and /.2... it will be beautiful... and we all know trolls can't survive in the vacuum of space.

    It was great while it lasted, but better get while the getting is good. Farewell /.... farewell

  • The latest study shows that worrying about magnetic fields causing cancer causes cancer.

    -Pete

  • Did anyone notice they said the speed would be about 180,000 miles per hour in 3 months? The speed of light is about 186,000 miles per second, so traveling to the sun would only take about 21 days from earth's orbit.

    Yeah? What about the three months to get to that speed?

    -Pete

  • I can imagine a Pooh-Bear of the future inside of his magneto bubble, covered with mud, singing, "I'm just a little black space cloud hovering over the honey tree. . ."
  • Its so simple...just reverse the polarity of the magnet. The Sun would then pull the bubble, rather than push it.

  • this idea rules! just send some sort of magneto bubble/thruster package with drilling capabilities into space, point it in the right direction, and stick it to an asteroid in it's path. 10 years later, asteroid arrives at earth, vallet style. then mine out the asteroid in a honeycomb fashon, tether a cold fusion generator to the asteroid, and heat the inside and rent it out as some bitchin' penthouses. with views.
  • i would assume they'd speed up going twords a body, and then slingshot around it using the gravitational force to sling them back to earth, or their original origin while keeping the magneto bubble deflated
  • This isn't so bizarre. Science fiction writers have been clinging to this concept for a long, long time. (At least, the concept of riding on mangnetic waves).

    My personal favorite is Dan Simmons' vision of the Ousters with multi-kilometer wings that could 'catch the magnetic waves' and push them around in space. Like giant butterflies. Very cool. It's nice to see another of the science fiction authors' predictions coming true.

  • 200kg? (Score:5)

    by Gorimek ( 61128 ) on Thursday October 05, 2000 @10:49AM (#728275) Homepage
    Before you get carried away by "That's enough to accelerate a 200 kg spacecraft from a dead stop to 80 km/s (180,000 mph) in only 3 months.", remember that just 2 astronauts and their suits are heavier than that. That's without any actual spaceship.

    Also later on it says

    Maintaining such a bubble in space would require about 1 kW of power and less than 1 kg per day of helium propellant for the plasma source. In return, the bubble would intercept about 600 kW of solar wind power.

    So... if it weighs 200 kg, and uses 1 kg per day for propellant... Isn't there a fundamental problem here...?
  • mass expended per unit time is a rate.
  • This is a guess, but I'm pretty sure that I'm right: The magnetic field does not get more intense, it gets larger: the gas blows it up like a balloon. I would assume that the per-unit-area intensity decreases as the size increases, which means that, for a given field power, there would be an upper limit on field size: at some point, the field will become so large (and thus so weak) that the gas leaks out faster than you can replace it.

  • Wouldn't the force of accelerating that fast kill a person?

    I guess we can forget taking one of these things ourselves anywhere.
  • That star would have a solar wind itslef, would it not?

    I think the more important thing is running into a planet or asteroid.
    ----

  • Re:But how do they get back? (Score:3)

    by kevlar ( 13509 ) on Thursday October 05, 2000 @09:29AM (#728280)
    Good question. Whats even cooler though is how they can use the same propulsion system to stop. If they're traveling towards another star, they can gradually reduce the field in such a way that it'd bring them to a stop in just the right place. If the field was too strong, then they'd stop somewhere a little further than halfway, and if it wasn't strong enough, then they'd never stop.
  • There is no such thing as a frictionless anything. even in space there is dust, radiation, and all kinds of other things that WILL slow you down. And what i was trying to say is that had best not be off target or you will be missing your ride home. you would have to be at another star to get your push back, but if you miss a star then your SOL.
  • You speak of 'just travelling in space' as though that really wasn't much of a breakthrough at all! Granted, this is not the technology that will send the Millenium Falcon roaring out of Mos Eisley. It's not supposed to be. In a way, this technology is more exciting than that. This technology makes the idea of a manned trip to Jupiter, etc. much more of a possibility. We can get (roaring, even) into space already, albeit clumsily. Where we go from there and how we survive while doing so is where things get really sticky. This is great news!

  • That occured to me also. Either you use this kind of thing on a one-way trip (good for expendable probes) or you make a sling-shot around the planet of interest and conduct your business *real fast* on the fly-by. ;) I haven't heard anything written on the concept of "tacking" upwind like you would do in a sailboat (since I believe that makes use of lateral pressure exerted on the boat from the water). The only thing left would be some other (more conventional?) thrust device, but now we're stacking up lots of extra mass to the point that the magnetic sail wouldn't work nearly as well to begin with, rending the discussion somewhat moot. Unrelated to this, though, I have to wonder how massive the magnetic generator itself is. Sounds like they can meet the 1kW power requirement well enough, but it needs [nearly] 1kg of "fuel" (for plasma) also per day. The numbers quoted at the top for a 200kg vehicle isn't all the heavy. By the time you add yourself, a friend, and the obligatory Beowolf/Linux cluster, well, I just start wondering if it would truly attain their listed speed *or* endurance rating. Just my thoughts.
  • cancel the supply mission?
  • With more time to think, "tacking" certainly wasn't the right word to use, as this means progress upwind.

    I'm really thinking more of steering. The solar wind will always be radially outward from the sun. I'm thinking in terms of gaining accelleration in the plain perpendicular to the local wind vector.

    THe force vector will be radially outward. To knock off a dimension, assume that we stay in the plane of the solor system. If the vessel is off of the vector, displaced by an angle theta (where 0 would be on the vector), the accelleration breaks into Fcos(theta) away from the sun, and Fsin(theta) laterally.

    As far as the filed, I don't mean making the field funny, but instead to spread out the unit in some way so that the field is generated away from the center of gravity of the entire vessel. This should give a similar ability to move outward.

    There would still always be accelleration outward. HOwever, if it is possible to move the vessel far enough off center, it may be possible to move outward while accellerating against the direction of orbit, enough so that the orbit decays and the craft comes inward under the force of gravity.

    hawk, who could have done the math for this in his sleep 15 years ago . . .
  • As far as I can tell, this has nothing to do with going to space. It's talking about once you're already there. Isn't accelerating 200kg to 180,000mph in 3 months a little low to actually break out of earth's gravity? Unless they are referring to hitching a ride on the magnetosphere. But they never actually said anything about leaving earth on one of these, just travelling in space.


    _______________
    you may quote me
  • I wouldn't mind seeing the comparison between rocket propulsion and electromagnetic propulsion (incluing ramjets, ion, etc)...based on cost, efficiency, speed and payload capability. The rockets seem to be able to carry larger amounts of weight, but they only go so far. Ion propulsion, takes less money and less full, but takes little bit longer. However, it can go faster and longer easier. (hence deep space missions). What is the use for this new technology? Obervation missions only or a long-span manned flight? I suppose I could research it more...but if it is anything like my electrostatic paper research...it is too much info :) -Corey
  • The only way you can move with solar wind (without thrust in another direction) would be in the direction of the solar wind.
  • I'd really need to know what stops this from following the normal rules of mechanics before agreeing with that.

    The only force available is ratially outward, yes. But normally, if force is applied other than the center of mass of an object, the accelleration is *not* in the same direction as the force vector.

    hawk

  • Radio Interference.. (Score:3)

    by nyet ( 19118 ) on Thursday October 05, 2000 @09:36AM (#728290) Homepage
    Quick question (maybe a stupid one)...

    Does this miniature magnetosphere have to be turned off everytime you need to talk to your craft?

    It would seem to me it might interfere a tad with radio communications...
  • Man, what a nifty idea. Especially if the term "solar sail" conjures up for you images of kilometer-sized sheets of gold foil.

    One thing I wished the article would have explained better: How is it that plasma can expand a magnetic field in that way? I mean, I see how you could block an EM field-- we see that everyday-- but intensify it? (without increasing the coil voltage, at that). Could anyone comment?
  • Oh wgere can I find the tic in tape??? please somebody tell me. I NEED to know. I might die...
  • You'd be sending equipment, not people. On the other hand, the 1kg/day propellant is a much more serious problem. It's probably not steerable enough to do a good flyby of one of the outer gas planets or their moons to pickup some hydrogen without risking falling into their gravity well. But you can find some interesting balance of weights and propulsion strengths to get out to interesting parts of space and send telemetry back, and once you're going that fast, it's a nice cruising speed.
  • At first I read this and thought that it would be the greatest invention in the history of mankind, but then the skeptic in me hinted at the mathematician in me, and so they got together and did a few calculations. First of all, to say that a man-carrying spacecraft will weigh a mere 200 newtons is horribly unrealistic. Let's say it has a meager crew of two men, weighing 75 kg a piece, for a total of 150 kg; plus we'll say another 50 kg for spacesuits and such. Now we will use another 200 kg for the weight of the extremely diminutive spacecraft they are to travel in, all in all, that gives us a weight of 400 kg. However, for each day in flight, the engine requires 1 kg of fuel, and the astronauts, we will say, a conservative 3 kg of food a day, for another 4 kg of mass for each day of travel. It is approximately 5.8 billion km from pluto to the sun, and approximately 149 million km from the earth to the sun, so I hopefully can assume it is about 5.7 billion km from the earth to pluto, which I will use to represent the edge of the solar system (hey, it is, after all, isn't it?) Since F=ma and d=(at^2)/2, we can express d as being equal to (Ft^2)/(2m). There are about 86400 seconds in a day (slightly less, since a day is 23 hr, 56 min, 4.0989 s, but i have to be reasonable). The craft will need an extra 4 kg a day, which translates into 1 kg every 21600. We can then express the craft's mass in terms of t in s as m=400 kg+(t/21600s) kg. Using a bit of algebra we can get m=(Ft^2)/(2d). We can set these two equations equal to eachother and get the quadratic t^2-(1.75926*10^8)ts-(1.52*10^15)s^2=0. Solving this and eliminating a negative answer gives us about t=184 million seconds, or 2131 days, which is about 5.84 years. This would be far and away the longest mission ever (with an actual purpose, not including Russian guys spinning chess pieces in antigravity for ten years at a time while the government scrounges up enough money to get them home). The craft would weigh, by the way, about 8927 kg. These are most conservative estimates, and if someone can give me actual figures for my guesses I would be more than glad to do the math to figure them. Maybe later I will figure how long it would take to get to alpha centauri. The craft accelerates at about 3.36*10^-4 m/s^2 and would be going about 5.7*10^9 m/s, which leads to some interesting questions, since that is nearly twenty times the speed of light. When I sat down to do all this math, I thought I would debunk this technology, but really all I did was show that it unfurls even more questions, and that possibly all of you may be able to guess that I am doing poorly in my AP Physics B class.
  • someone needs to lay off the himalayan insane peppers...
  • The trick, of course, would be to use less energy running the 'sphere than you would gain through mechanical energy.

    Now I've got this mental image of a giant Sipping Bird on the Moon. Thanks a lot.

  • Science Fiction becomming Science Fact (Score:3)

    by Lensman ( 21605 ) on Thursday October 05, 2000 @10:57AM (#728300) Homepage
    Ok, Is it just me or does this look amazingly like the Star Trek "Warp fields"..... Use something along the lines of the ST nacells and you get more elongation to your field. (Ok I don't know how multiple fields might interact, but there's another way to gain a little control.) Also as long as your not talking about supra liminal velocities just stick a couple of "feild generators" out on some sort of boom arm and there you have some steering control with more or less pressure being applied to one side of the craft or the other. X wing them for more than one plane of control.
    For additional thrust (at least at the onset, or possibly for breaking) vent the plasma gases, that you just used to expand your field, through a nozzel.
  • But you've forgotten that the accel is continuous, not a single burn. As soon as you're going farther than the moon, you're saving time.

    With a (helluva) rocket that gets you to 50,000kph in one extended burn, a 1 AU trip (150M km) takes 3,000 hours.

    With a solar sail that gives continuous (and puny) .01 m/s/s acceleration (.001*g, or 10N acting on 1000kg), a 1 AU trip takes 1,521 hours, or half as long.

    (Neither of these take into account the time to brake, or my poor arithmetic. But plug in t = d/v versus t = sqrt (2d/a) with your favorite numbers and you get the idea.)
  • Easy. Just reverse the polarity!

  • Re:implications... (Score:3)

    by Dirtside ( 91468 ) on Thursday October 05, 2000 @11:00AM (#728311) Journal
    Hmm, if I traveled into the past and wanted to leave a message for future generations, I would use a giant laser to carve the message into the moon. It would be, CHA- but then get cut off as my laser was destroyed by a 400 pound blue idiot.
  • You shield and direct the magnetic field such that it is flat, then you turn is sideways to the magnetic wind. Just as in sailing, instead of going straight out in front of the wind, you will tend to drift sideways. You can use this effect to decrease your orbital velocity and then let gravity pull you home.

  • The report is obviously dumbed down for the layman, so it's hard to really pass judgment on this thing. (I would really like the read the whitepaper, if anyone has a link to it.) But if the description is accurate, this could be an incredibly cool way to get around, once you're in orbit.

    Of course, we still don't have a cheap way to get to orbit. Thanks, NASA.

    At any rate, to answer a few questions I've seen posted here:
    1) Yes, the basic concept of a solar sail is sound. It has been tested, and it works.
    2) Yes, the acceleration is low, but it is continuous. That fact, plus the fact that you don't have to carry (much) fuel, put's you WAY ahead of any chemical rocket solution.
    3) The magnetosphere wouldn't hurt the crew or the onboard electronics: you just put the lifesystem inside a Faraday cage.
    4)And YES, you could come back from a mission to, say, Mars, using this technology. Travel between planets is accomplished by establishing yourself in an eccentric orbit that passes through the orbital path of both your origin and your destination. So you can use the magneto-sail to push out away from the planet, establish your orbit, then turn it off when you reach the "top" of your curve, and fall back in. Then turn the sail on again when you need to brake.
    Depending on the location of various planets, you could also use the sail to travel out, develop alot of speed, and then slingshot around another planet to turn yourself around and head back home.

  • Wow! (Score:5)

    by jonfromspace ( 179394 ) <jonwilkins@nosPam.gmail.com> on Thursday October 05, 2000 @09:38AM (#728318)
    "A 15 km-wide miniature magnetosphere one astronomical unit from the Sun would feel 1 to 3 Newtons of force from the solar wind," says Gallagher, "That's enough to accelerate a 200 kg spacecraft from a dead stop to 80 km/s (180,000 mph) in only 3 months.


    I have been reading alot about alternative propulsion as of late, and this seems by far the most realistic approach. While we are not going to see this in action for some time, it opens a ton of possibilities for countries like China that are just venturing into manned space flight.

    With the amount of money the US Government has tied up in the Shuttle program, it is unlikely that they will even attempt implimenting this kind of technology on anything other than a "Test Platform" for at least 10 or so years. However, a country like China that is relatively new to the "Space Race" could easily use this kind of technology to attempt large scale interplanetary expiditions, with a far shorter time-line than competing countries.
    Wouldn't it be something if the Chinese were the first to put a man on Mars? Don't laugh, it could happen.
  • I suppose I'm going to have to give the proper response to this: You keep the bubble on full the whole way.

    Assuming two stars of equal solar wind, half way there, you're not being accelerated by the wind of either star, but you're coasting along at your highly accelerated rate. As you approach the other star, its solar wind begins to dominate, slowing you down to a neat stop at your destination.

    THEN you turn off the bubble!

    In a real example, Just adjust your bubble up or down as you go, according to the difference in solar winds.
  • especially if the planet you're aiming for won't be on this side of the solar system for another 90 years (hello pluto!)

    Doesn't the Earth go around *every* year? Can't you just wait six months for that, and THEN head off to Pluto? :)

  • This could be interesting. It's quite easy to manipulate the shape of a magnetic field (cf the torus-shaped fields used in fusion experiments). Maybe it doesn't have to be a bubble. Maybe it could be disk-like, and thus present a wide area for less energy than they figure for a spherical bubble. Hmmmmm....
  • Except, according to the article, the probe needs about 1kg of fuel per day to generate the plasma. So for 400 days of acceleration, you'd need 400kg of fuel... of course, the mass would decrease by 1 kg per day while the force remained constant, so that tends to complicate things somewhat.

    Still, it ends up going REALLY fast :)

  • Wouldn't it be something if the Chinese were the first to put a man on Mars?

    Sure. But it would be an even bigger deal if the Chinese got their act together on Earth first so they could be the first to put a free man on Mars.

    --

  • I've seen several questions about how to 'tack' back into the solar wind to get back to earth. With a conventional solar sail its pretty straight forward.

    A conventional solar sail works by reflecting particles/light/etc and simple action/reaction. to go out to mars for example it is angled in a way to reflect particles away from itself to increase it's orbital speed; faster orbital speed puts the vessel in a higher orbit in the solar system. Coming back simply means angling the sail the other way so that the reflected particles slow the orbital speed untill the orbit lowers back to earth.

    My understanding with a magnetosSPHERE sail is that it cannot by it's nature 'tack' back into a lower orbit as it is sphere shaped; It acts much like a parachute rather than a flat sail.

    To tack such a vessel back you either have to figure out a way to 'flatten' the magnetic sphere into more of a disk shape that can act as a conventional flat sail. The other alternative is to use a planet's gravity to 'slingshot' you back the way you came.

    You could probably 'flatten' a magnetic sail by using a large torsional (donut-shaped) ring to create the magnetic field. Older magnetic sail designs I have seen used a superconducting cable in a loop which naturally repelled itself and created such a shape but these early designs did not incorporate the 'plasma boosting' the new design displays.

    -- Greg
  • This bubble analogy they use in the article is confusing me. Blowing up a magnetic bubble with plasma? It makes for a good mental image, but from a physics standpoint is total crap.

    Can someone who understands the actual physics of this propulsion explain it in terms that someone with some physics knowledge could understand? I'd like to know how they really get magnetic field amplification from plasma.

  • It's easy (Score:3)

    by Once&FutureRocketman ( 148585 ) <otvk4o702NO@SPAMsneakemail.com> on Thursday October 05, 2000 @09:49AM (#728344) Homepage
    As I explain in my other post [slashdot.org], you CAN get home with this thing. Unless you have enough power to thrust continuously at high acceleration (which would require a fusion motor, at the least), travel between planets is done by establishing yourself in an eccentric orbit (or spiral) that includes your origin and destination. So to return from Mars, you can use the sail to accelerate out away from the sun, then turn it off (or turn off the plasma generator, allowing the sail field to shrink) while you fall back in, towards home. Turn turn it on again as you approach Earth, so that you are moving slow enough to be captured into orbit by Earth's gravity. After that you probably have to use rockets to deorbit, but that doesn't take much delta-V.

    The same approach would let you fly from Earth to, say, Mercury.

  • Tacking works on a sailboat because the keel has the water to push against, so the vector of the force exerted by the wind that would push the boat in the wrong direction has a contervailing force. A spacecraft wouldn't have the equivalent. To return, I presume that you'd do it the same way as you got to whereever you are (assuming that it's near a star): unfurl the sail and let the star accelerate you, then drop the sail when the solar wind from the destination exceeds that of the star you're using. Of course, IANASS (I am not a solar sailor)

  • Power Plants (Score:4)

    by mbrod ( 19122 ) on Thursday October 05, 2000 @09:50AM (#728346) Homepage Journal
    Since the moon doesn't have a magnetosphere couldn't you put types of these machines on the moon as power plants.

    You have one of these machines on an extremely long slanted pole. Slanted meaning slighty up from the moons surface. When you turn it on the solar wind pushes on it. You have a tether to a generator. The tether pulls on it creating power. Once at the end of the pole the machine turns off. The small amount of gravity on the moon pulls it back. Once it is back in its starting position it turns back on and the process starts over.

    Sort of like a windmill, moon style :-)
  • If the sail is reflective, you effectively get outwards thrust by intercepting solar photons and tangential thrust from 'emitting' the reflected photons.

    I had remembered that a black sail would work as well, but after a few minutes of drawing vector diagrams, I can't see how.

    Replying to someone else's point about using several bubbles tethered together: I can get some tangential thrust if one is 'shaded' by the other, so the rear one receives solar wind only on one side. There is also a torque that will tend to spin the tethered bubbles, but this can probably be counteracted by clever uses of magnetic fields reacting against the solar magnetic field. This isn't very efficient in terms of sail area to useful thrust ratio, however.

  • tacking uses two forces (the wind and the resitance of the water). In space, you have solar wind and you have grvity. *should* work... Oh, and this is not well thought through at all, so you may have to > /dev/null
  • It always amazes me how often science fiction predicts the future. This concept is similar to (and even looks like) the warp bubble idea in Star Trek.

    Actually, I suspect that it went the other way. Trek fx creators probably based the looks of the warp bubble on the shapes magnetic fields take. And the looks are sorta similar, but I can't see why you think the concepts are ...

  • TO be honest, this was the _first_ thing I thought of.

    Magneto's force-bubbles.

    Nice to know Real Life imitates art. Although, somehow, I don't think he's filling them with plasma, as even Magnus needs to _breathe_. :)

    Damn, I am a Marvel Comics Geek. :)

    Redhawk

  • Re:Looks pretty damn cool! (Score:5)

    by Wellspring ( 111524 ) on Thursday October 05, 2000 @11:25AM (#728360)
    (I would really like the read the whitepaper, if anyone has a link to it.)

    Ask and you shall receive:

    Phase One of his study: Read the Abstract, enjoy the [usra.edu]Full Report [usra.edu].

    Phase Two of his study: Read the Abstract, enjoy the [usra.edu]Full Report [usra.edu].

    You're welcome.

    Interesting idea. Note that the 15km bubble he talks about is only with a kilowatt of power and a 200kg spacecraft. A multiton behemoth would have a huge magnetic bubble. I think the economies of scale sound pretty good on this.

    Of course, the big problem of space travel, as everone else is also saying, is the earth to orbit phase.

    ps: 500 hits to this report before we slashdotted it!!!

  • no trip back (Score:3)

    by British ( 51765 ) <british1500@gmail.com> on Thursday October 05, 2000 @09:51AM (#728363) Homepage Journal
    Even if there's no way to take a trip home with it, would it be a cheaper way to build the ISS and shoot up satellites?
  • I don't know if this technology would be a candidate for interstellar spacecraft, but if it is, you could always just push off from the destination star to start the trip back.

    I wonder what the "terminal velocity" of this system would be? If you start off close to a star and just sail away, how fast would you be going when the acceleration finally peters out?
  • On the other hand, they probably won't have a hard time tracking the vehicle even if it's a horrendously far distance from us. Could they not modulate the field as a form of communications? It is after all, just a basic magnetic field and basic electronics gear.

    Food for thought!
  • It doesn't use radio for communications. It uses IR.

  • implications... (Score:4)

    by fudboy ( 199618 ) on Thursday October 05, 2000 @10:12AM (#728369) Homepage Journal
    It sounds like you could just bolt this new device to the floor of a shuttle's cargo bay and have yourself an interplanetary cruiser. That would make shuttle trips to places like L1 or a lunar base not only viable, but downright dirt cheap, and missions to Venus, mars and the asteroids well within reach. I am not too sure on how it works, but there is a technique that sailing ships used to travel into the wind (tacking?) for the return journeys. The biggest concern would become cargo space for life support: air, food and water, rather than fuel. The future is finally with us!

    One really exciting use for this would be to attach drives like this to asteroids. This would first and foremost serve to save the Earth from any imminent collisions but would also allow you to re-position juicy asteroids closer to home, etc. All you need to do is bolt the coil and a power generator to the surface, and voila'! the rock will be moving 180,000 km/sec within umpteen units of time.

    Let's just assume the m2p2 drive will make it. The next holdup will be attaining orbit. I predict that either one- something similar to m2p2 is developed to launch cheaply using the Earth's own magnetic currents. Launches would take place at one of the magnetic poles (finally, a use for Antarctica!) and will be simple and sturdy like the m2p2. OR two- the application of the cavitation bubble can be used for building up hypersonic speeds (escape velocity) without much friction and without fighting gravity. A damned Mack truck could attain orbit with a system like that.

    One further thing strikes me as curious about this. I know it's pretty far-fetched, but the [douglas adams/joseph campbell/tim powers] tainted conspiracy theorist within urges me to mention it; The name m2p2 bears a close resemblance to the city 'machu pichu' one of the absolute most vexing mysteries in human history. The architects of that ancient city were able to bring large rocks (massing dozens of tons each) to a remote South American mountain peak many miles from the quarry of origin. When you ask yourself "did they use m2p2 to build machu pichu?" and take into account the permutations and perversions of language drift, a suspicious coincidence in phonemes comes to light... I wonder if a band of space adventurers stumbled back in time and tried to leave us a message or hint?


    :)Fudboy

  • Hell bent for leather - outta here! (Score:4)

    by dmatos ( 232892 ) on Thursday October 05, 2000 @09:58AM (#728371)
    That guy's not kidding about becoming the furthest man-made object from the sun. 80km/s may not sound like much after three months, but note that, amazingly, acceleration will remain constant because the size of the bubble will increase as the pressure of the solar wind decreases.

    I did a little bit of math, and came up with 392 days to pass Pluto's orbit, at which time the probe would be travelling at a speed of almost 350 km/s. That's more than 0.01c, so we'd have to start figuring in relativistic effects, but damn that's fast.

    Note: I'm on my co-op term now, so please excuse any mathematical mistakes as my brain has been turned off.
  • will design translucent blue or orange or purple magnet bubbles, and we will have multiple color sky in the future.

  • Comment removed based on user account deletion

  • Can some one with a better grasp of inter-planetary physics comment on whether you could use the space shuttle to launch small vehicles using this technology?
    I know the space shuttle doesn't _really_ travel in space by some people's definition but how much force does it take for a comsat or something of that mass to get away from Earth if launched from the shuttle bay? If nothing else a test vehicle to demo the theory could be hoisted up and turned on to see if the idea works in practice.

    What about the same idea from the space station? And/or use it to help sheild parts of the space station and help it mantain orbit using less power?

    =tkk

  • Okay, factoring in the weight of the fuel, assuming it is used at a constant rate, and acceleration becomes a function of time (because mass decreases over time). Now calculate v after 400 days by integrating a from 0 to (400days*#seconds=) 34560000, and after 400 days the probe is moving at 190km/s. Still quite respectable.

    This is harder. Integrate v in terms of t to get the distance travelled in that time, and we have... Boy, this integral sucks... I'll get back to you...
  • I wonder if you could slingshot around the earth towards the sun, and fire up this sucker near a solar flare to see how far it would shoot you out of the solar system. The force on your magnetic field would be insane which would either kill you or propel you like mad out of the solar system. Suddently this makes lots of things in the solar system managable. Think robots dispatched into space to latch onto asteroids and propel them to near earth orbit (dangerous terrorist weapon OR raw material mining?), because most asteroids are further off you could slingshot an asteroid around a planet with one of these and send it back towards earth or keep it in orbit around the moon. The scifi implications of this stuff will keep people thinking for years to come.
  • Who wants to come back? I'm outta here. Alpha C, here I come!!!
  • This thing uses the solar winds to "push" itself somewhere.

    If this were sent to another solar system, it would use the Earth's sun to get it half way or so then it would use the solar wind from the destination star to slow it down. It would be like running _into_ the wind. This would slow it down, and bring it to a stop.

    Also, there are other ways of slowing down. Using gravity would be one example. They use it now for boosting the speed of satellites and other space equipment. But remember that this can be used to slow something down. Much like the way things are drawn into the sun, or a black hole, or a planet. Remember the comets that struck Jupiter not too long ago? Obviously they slowed down enought to fall into Jupiter's gravity well.

    Getting back from trip out to the planets could use the same principles. Get a boost from a planet and redirect back to Earth, turn off the sail. Get closer to Earth then hit the brakes by turn the sail back on.

    Without gravity to assist on the accelerations (whether positive or negative) many other alternative ways could be devised to slow down and stop. I'm sure you don't lack the creativity to come up with other means. (maybe a magnetic cannon or something)

  • No steering? (Score:3)

    by Michael Woodhams ( 112247 ) on Thursday October 05, 2000 @10:19AM (#728401) Journal
    A fascinating proposal, but it lacks an important factor - steering.

    A force radially away from the sun does very little for you. The solar wind force cancels a tiny portion of the solar gravity, with the result you end up in an orbit just slightly larger than before you turned on the sail.

    To get anywhere, you need a component of force along your direction of motion. In 'traditional' solar sailing, this is achieved by putting the sail at 45 degrees to the solar radiation. If the tangential force acts in the direction of your motion, your orbit steadily grows. If it acts against your motion, your orbit shrinks.

    So far as I can see, this proposal produces an approximately spherical 'sail'. This would not allow tilting the sail to produce a force component along the orbit. However, they don't discuss the shape of the bubble, so I may be going astray here.

    As an aside - from memory, there is about 10 times as much pressure available from the sun's light as from the solar wind. This method doesn't use the light, whereas 'traditional' solar sailing does. This advantage is likely overwelmed by the ability to make a large 'sail' cheaply and lightly with the bubble method.

    (My solar sailing experience is limited to setting an undergraduate assignment on the topic some years ago.)

  • they can gradually reduce the field in such a way that it'd bring them to a stop in just the right place.

    But then they would lose the magnetic shield that the propulsion system gives them. Worse, coming back they would have to counteract the force exerted by the solar wind.

    --locust

  • Re:Great, but... (Score:4)

    by option8 ( 16509 ) on Thursday October 05, 2000 @10:05AM (#728405) Homepage
    we've been talking around the office about this since it came up, so we have a few ideas already :)

    first of all, there would have to be some other kind of drive in order to leave orbit in the first place, or even simply for steering, so that could be used for braking, etc.

    then there's the option of the "2010" gravity-braking slingshot gambit, whereby one who is travelling at breakneck speeds whips around a nearby planet - optionally skipping off the atmosphere - slowing down enough to enter orbit at the target planet. the same trick can be used simply enough to steer - NASA's been doing it for years - or to head back in toward the sun after building up a velocity heading out

    let's say you're headed for venus, but the cheapest way to get there would be to build up a good velocity by heading out towards jupiter first, then whipping around big J, turning off the magnets (or turning down the power) and coasting back towards the sun, catching venus on the way. this isn't all that efficient, since you can build up enough speed whipping around the earth-moon system a few times, but you get the idea - especially if the planet you're aiming for won't be on this side of the solar system for another 90 years (hello pluto!)

    on the topic of longer distances - say another star - it's a simple matter of heading out on the solar wind, and using the other star's push to brake.

    the problems we see remaining involve being in interstallar space, outside the influence of any solar wind. sure, the velocity would be nice and constant, but short of another drive system, there's little to use for acceleration, steering, etc.

  • there are other things that might get a little wonky being in the middle of a big magnetic field - Larry Niven's stories come to mind, with the problems involving the damage to living systems in the middle of such fields - but there's no reason you couldn't use the sail as more of a kite

    put your fuel and your magnets on a probe and extend a long boom outside the field, or else far enough out to make the effects negligible, and build your life support there. let the sail tow the life support system along.

    tho, now that i think of it, the sail might be better off pushing the life system around rather than pulling, as the field acts as a shield against the debris and radiation of the solar wind...

  • That thing STILL won't get you out of the gravity well. The gravity well is what's holding us back at the moment. Once we get our asses INTO space, we'll figure something out.

    Call me when they find something that makes getting out of the gravity well as easy as this thing sounds like it is.


  • The baloon analogy is a good one. Although the basic fact is that currents in the plasma (which is a good conductor) cause the magnetic bubble to expand, these currents are generated by the thermal pressure of the plasma. This pressure pushes out against the magnetic field and the magnetic field tries to hold it in. Think of the field as a baloon, expanding until the surface tension balances the pressure of the gas inside. In the case of this bubble propulsion idea, there is a third force -- the solar wind. So your bubble expands until the force of the magnetic field+solar wind balances the plasma pressure. This is why they claim that the "sail" will get bigger as you go further out -- the solar wind pressure drops, and the thing will therefore expand more. I heard about this idea a while ago and read the early white papers. Sounds very interesting and is on a sound physical basis, but I think engineering issues will be hard to overcome (lots of potential damage to sensitive components by RF/high density plasma bombardment, etc).

    If you want a non-baloon explanation -- the driving force is a plasma pressure gradient. You put hot plasma on the field and so that it is hottest near the space craft and cool further away (hard not to do this!). This pressure gradient creates a current around the spacecraft called a "diamagnetic current" (due to gyration of particles about the field lines in concert with a density or temperature gradient). This current wants to expand outwards (all closed circuits experience the "hoop" force that make them want to expand), and hence your bubble expands. Couple that with the fact that the dipole field is "frozen" into the plasma, the dipole field is dragged outward to form your bubble.

  • But how do they get back? (Score:4)

    by NecroPuppy ( 222648 ) on Thursday October 05, 2000 @09:19AM (#728416) Homepage
    The article didn't go into this, but how would a vessel equiped with such a propulsion system return to Earth?

    Could it tack back into the solar wind for the return trip?

    NecroPuppy
    ---
    Godot called. He said he'd be late.
  • Wouldn't it be something if the Chinese were the first to put a man on Mars? Don't laugh, it could happen.

    would that make Mars the Red Planet?
    ---
  • . . .especially with the power and mass requirements.

    The one immediately obvious drawback is that it is relatively slow. Another question that comes to mind is the effects of such a strong magnetic field on electronic devices within the field. Or for that matter, the effect on biological systems within such a field, especially over long periods of time.

    But if nothing else, the team at NASA has apparentely developed an inexpensive solar radiation shield, especially useful for deep space exploration or space habitat use during solar storms. . . .

  • cool, but... (Score:3)

    by meersan ( 26609 ) on Thursday October 05, 2000 @09:20AM (#728425) Homepage
    This sounds cool, but from the sound of it, it only works one-way!

    The article talks about family flying saucers, but it doesn't mention how you get back after you zip off to Jupiter. Of course, considering some of the loony stuff happening on Earth lately, maybe you can't blame them for conveniently forgetting a return path.
  • If you need 1kW just for a 200kg craft it means that the power requirements for a manned 30 tonne mission will be pretty high. Where do you get all that power? Solar panels are heavy and not very efficient.

    I guess this calls for unpopular power sources such as radioisotope thermoelectric generators.

    ----
  • It sounds like you could just bolt this new device to the floor of a shuttle's cargo bay and have yourself an interplanetary cruiser. That would make shuttle trips to places like L1 or a lunar base not only viable, but downright dirt cheap, and missions to Venus, mars and the asteroids well within reach. I am not too sure on how it works, but there is a technique that sailing ships used to travel into the wind (tacking?) for the return journeys. The biggest concern would become cargo space for life support: air, food and water, rather than fuel. The future is finally with us!

    Hmmm - I think the mass of the Shuttle would be a little too large for this accelerative force to have enough of an effect. Of course, everything will be fine with this as long as the astronauts are willing to wait a few months to get up to speed :) As for tacking, as has been mentioned in numerous posts so far that only works because the interaction of the keel and the ocean coupled with a directional planar sail can translate the head-on force of the wind into forward momentum. Until we invent ourselves a spaceship 'keel' that can interact with the space-time continuum (I always enjoy it when I can crowbar that phrase into a sentence :) we're pretty much stuffed.

    One really exciting use for this would be to attach drives like this to asteroids. This would first and foremost serve to save the Earth from any imminent collisions but would also allow you to re-position juicy asteroids closer to home, etc. All you need to do is bolt the coil and a power generator to the surface, and voila'! the rock will be moving 180,000 km/sec within umpteen units of time.

    ...where 'umpteen' is unfortunately an unfeasibly long time due to the fact that an Asteroid is n orders of magnitude more massive than the 200kg spacecraft NASA is talking about.

    --
  • There is no such force in space
    In a word, gravity.

    Yes, it's the force the water applies to the keel, counteracting the sideways force of the wind which allows a sailboat to sail upwind. FYI sailing on water the vessel moves forward by using the wind to generate lift (like an airplane's wings) to pull it forward, whereas space sailing movement is generated by action/reaction (like a rocket motor) so they are two completely different methods.

    The 'keel' a solar sail uses to get closer to the sun is the sun's gravity itself. As the solar sail changes it's speed by reflecting particles in the direction it's traveling and causing an opposite reaction away from that direction (i.e. slowing itself) the lower orbital speed makes it fall towards the sun.

    The best way to explain it may not be by words; so try the solar sail simulator [ec-lille.fr] java applet and see for yourself.

    A conventional solar sail will sail 'to windward' like a Farr 40, whereas a magnetospheric sail sails to windward like a Morgan OutIsland.

    -- Greg (S/V Scirocco)

    PS: In the future please double-check that you are 'right' before calling someone else 'wrong'.
  • Yeah, that's correct. They said the thrust would be 1-3 Newtons, which is quite a bit smaller than your average Estes rocket motor. That's not enough to overcome gravitational acceleration for anything with a mass greater than... oh damn I could never do math ... 100 grams? Is that right? Something like that. Even if it did work in the atmosphere.

  • Re:But how do they get back? (Score:3)

    by Pablonius ( 3962 ) on Thursday October 05, 2000 @10:08AM (#728437) Homepage
    Actually, as soon as the grav assist was done, they could turn the bubble back on for a decel on the way back to Earth. If it took three months to get to their current speed to get to the planet they'll use for slingshot, they'll be back a their original starting speed + the speed they picked up from the slingshot. What they don't want is to try to deorbit at Earth with pre-slingshot speed + slingshot increase speed...
  • Eatrh's a dump.

    Heck, even the whales are leaving -didn't you ever see Star Trek IV: The Voyage home or read The Hitchhikers books.

    The evidence is clear -the fungi have reached us and now it's time to go.
  • Staaaar Trekkin' across the universe...
    On the starship Enterprise, under Captain Kiiirk
    Staaaar Trekkin' across the universe...
    Always moving forward, 'cause we can't find reverse...
  • and even worse...if you notice you're on a collision course with some asteroid, comet, or other space thing how do you change course to avoid while traveling at that kind of velocity?
    Changing your course is easy... remember, there's no friction. The hard part is noticing the obstacle soon enough to act on it.

    But actually, it's a silly thing to worry about... As astronomers often point out, real space is much emptier than the space in Star Trek. Even in the densest part of our local asteroid belt, an accidental collision would be very unlikely. In interstellar space, it's a non-issue.
  • If they're traveling towards another star, they can gradually reduce the field in such a way that it'd bring them to a stop in just the right place.
    Actually, if they kept the magnetic field constant, wouldn't they end up exactly as far from the destination star as they were from the origin star when they launched? (All other things being equal, of course.) It's just like a pendulum, except that they can turn off the force when they want to stop.
  • it's not too terribly difficult to build on an additional drive system to steer with - you have to get out of earth orbit somehow, anyway - but beside that, there are a multitude of ways to get to places in the solar system without much more than the magnetic sail

    for instance, as you said, by turning on the sail, you increase your orbit. by constantly increasing your orbital distance from the sun whilst you revolve around it, you can intercept an object in a higher orbit without much bother. changing orbital direction would involve some kind of propellant, or else whipping around a planet or something.

    i'm not the biggest physics nut, but how feasible might it be to put two drives tethered together at a distance, and varying the power of one or the other of the drives in order to get a lateral steering effect - in effect making the sail "flatter" in order to tack.

    also, there's no reason not to build a large light sail inside your magnetic bubble, which would grab the light from the sun as well as the wind, with the added effect that the field would protect the sail from heavier particles of dust, etc.

  • I'm sure it'll work great... (Score:4)

    by tuffy ( 10202 ) on Thursday October 05, 2000 @09:22AM (#728451) Homepage Journal
    ...until they turn it on and wipe out all of the onboard hard disk drives.

    :)

  • mag-neato (Score:4)

    by option8 ( 16509 ) on Thursday October 05, 2000 @09:24AM (#728457) Homepage
    okay, who else has visions of comic book supervillain magneto and his magnetic bubbles?

    magneto put all kinds of fun things into space with his bubbles - space ships, people, asteroids, the Avengers: West Coast mansion...

    maybe the guys at nasa aren't just watching Star Wars [slashdot.org] movies, but reading comics, too :)
  • The stuff they propose making solar sails out of is quite thin, the space debris is just going to punch a small hole in the sail. Your efficiency will drop a hair, but nothing catastrophic is likely to happen.

    I wouldn't worry about the sail so much as I would the struts and lines connecting the sail to the rest of the craft. Sure, the odds are really low that one will be severed, but if they weren't designed properly it could cause real problems.

    jim

  • Re:Solar sails (Score:3)

    by JatTDB ( 29747 ) on Thursday October 05, 2000 @09:25AM (#728463)
    Most conceptual solar sail designs assume the material is fairly thin, and anything that hits it would (generally) hit at a pretty good clip and just leave a hole shaped like it. No real tearing or shattering. Most of the holes left would be fairly small and not really impact performance significantly. For big holes, bring a repair kit along with you.

  • Ok, the working concept for a craft powered by solar wind involved a 300m wide sheet of 0.1mm thick carbon fiber fabric, or something like that. From an engineering standpoint, that is hellishly complex. The torque forces on something that would have to be small enough to launch complete by rocket, with a fold-out sail that enormous, are phenomenal. In addition, the solar sail's thrust is inversely proportional to the square of the distance from the sun, while the magnetic bubble expands as the wind gets more rarified, so the net thrust is the same at any distance.

    The fuel efficiency of this thing is pretty respectable, too. 1 kg per day is a little expensive over the course of a long mission, but they expect their efficiency to improve, and they would also probably also not need the full power field during cruising legs of the trip.

    The safety issue is the icing on the cake. This kind of thing would also make explorations of Jupiter easier, since Jupiter's equivalent of the Van Allen radiation belts give an exposure on the order of 5x a lethal human dose just to pass through at a speed reasonable for assuming a low orbit. Granted, there's not much on Jupiter for a human to walk around on, but if the radiation is 5x the lethal human dosage, your flight hardware needs to be very heavily shielded. This magnetic field frees up a lot of weight, which in turn increases the fuel efficiency.

    Now if only they could find a way of sailing upwind in the solar wind stream. You can do it with a properly configured sailboat, usually within about 45 degrees from the wind direction, give or take a few degrees depending on various specifics. If they could do it with solar sails, you'd have a viable human-transport system. Otherwise, the best return mechanism you could use would be to go out on full power, swing around a planet (without stopping) and power down to just enough to protect the crew, and drift back on momentum.
  • Do the math. If I have a 200kg probe, and I expend 1 kg of its' mass a day for the sail/shield, then we're talking about a **100** kg probe which can accellerate for 100 days. . .
  • if you're running into a star, it would have its own solar (stellar?) wind, so you'd coast to a stop.

    ..then start accelerating in reverse!

  • So you end up wth a hole a few inches, or feet
    at worst, in sail square kilometers large.
    No one would notice it.
    No significant ind force to enlarge the hole.
  • >you can't exactly 'tack' against the solor wind...

    Are you sure? Extend the lines on one size of the sail. The craft will be
    off-center, and you should get outward and lateral thrust
    as dictated by the cosine and sine of the angle at which the
    craft protrudes.

    I expect you could similarly steer with the magnetic sail by shifting the
    generation unit relative to the main craft, creating such
    an angle.

    These won't give you outright directional control, but they could affect
    the direction of your outward motion from the wind, or your
    inward fall from gravity . . .

    And the return trip could come by decelleration in orbit, and then
    steering along the trajectory . . .

    hawk

  • Re:But how do they get back? (Score:3)

    by maddogsparky ( 202296 ) on Thursday October 05, 2000 @09:27AM (#728491)
    Some of the stuff I've read about solar sails involves the use of small propulsion units to provide navigational capabilities. As for the return trip, they could use a gravity assist from a planet. As long as they shut off their magnetic sail, the return trip would be faster than the way out since decelleration could be done by atmospheric breaking.

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