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Space

Antimatter Propulsion 185

er333 writes "A group at Penn State is building prototypes of antimatter storage for space applications, and makes a good case that with the amount of antimatter that will be produced in a few years, "omniplanetary" missions will become practical, including manned missions to Jupiter. They have some images describing possible missions and a concept craft design called the ICAN II."
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Antimatter Propulsion

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  • by Anonymous Coward
    It's because he used the word "apt". Some /. moderator got confused and thought he was referring to a linux distro of some sort.
  • by Anonymous Coward
    It was called an Orion, and NASA did some preliminary tests using conventional explosives on a scale model. Unfortunately, the explosives didn't blow up evenly, causing lateral thrust and resulting in a rather jittery flight.

    The History Channel had a show that covered it, as part of their "History Undercover" series, called "Code Name: Project Orion". It was also written about in the novel _Footfall_ by Niven and Pournelle, and was the technology used in the movie _Deep Impact_.
  • by Anonymous Coward
    Why don't they use matter-antimatter converters? Not anything fancy dilithium powered, but good old black hole device. You know, if you take a small black hole it vaporizes in Hawking radiation thereby loosing mass. If you feed the same mass while it looses the mass from a garbage heap, the black hole essentially converts garbage to Hawking radiation, consisting half of matter and half of antimatter. The antimatter you keep and the matter goes into the garbage dump, where it eventually reaches the black hole again.
  • by Anonymous Coward
    A decade ago, I worked as a lowly graphic artist at a nationally recognized think tank. I was looking for some Apache helicopter clip art in some files (paper files) when I came across some misfiled documents with the "Antimatter" heading. (These files were intended for graphics only, but someone had left the text on these particular docs - a security breach).

    Anyhow, the documents matter of factly listed current positron output of the nation's accelerators, and output when taking into account accelerators coming on line in the next few years. They did mention antimatter as a fuel source for spacecraft, but more ink was devoted toward offensive weaponry.

    Unlike some of the posters here, the military was not interested in creating antimatter bombs that could crack open the planet. Rather, they saw antimatter as a means to create extremely small devices with great destructive power, for "stealth" attacks. Imagine mailing an atomic-level letter bomb to an enemy leader! Actually, don't bother- someone already has imagined it.

    Posting anonymously for obvious reasons :-D
  • by Anonymous Coward on Tuesday May 29, 2001 @01:28AM (#191864)
    Looking back to the past from the present, we tend to forget the psychology of the day, instead seeing events through a filter of modern opinion and judgement.

    The Japanese (at least their military) were fanatical. Their country had never been successfully invaded by a foreign nation. They had the samurai mindset of death before dishonor. Even the Mongols who terrorized Eurasia couldnt do it: They sent the largest force of soldiers over water in the history of the world (unbeaten until WWI) and what happened? The Japanese gods intervened, sending a "Kamikaze" or "divine wind" that wrecked the Mongol ships after the first few battles. (And since the Mongols made the error of sleeping on their ships rather than making camps on the shores, they were all killed.)

    Thats why in the end of the war they had suicide pilots (named after the supernatural forces they believed defended them). They were training civilians, women, to fight the Americans when they came. Running out of metal, they resorted to building balloons out of cloth and wood with incendiary payloads, and tried to float them over to North America to start massive forest fires. In short, they were doing absolutely everything they could to win. The Emperor knew things were lost, but go read what he said he was dealing with in the end: A pack of generals who were still adamant that they would WIN the war, not just successfully defend Japan.

    But by dropping the atomic bomb, a weapon of unforseen destructive power, their mindset was broken: They realized that if they persisted in fighting, it wouldnt matter how hard they fought, they and their land and everything they were would be obliterated for all time in an atomic blast. Like a slap in the face to wake someone up from a delusion. So whenever you weep for those slain by the bomb (and you should), dont forget that it likely saved a lot more human life on both sides of the conflict, by bringing a swifter end to the war. (I admit though that I dont know why the second bomb was dropped.)

    Sorry for the offtopic post. :/
  • by Anonymous Coward on Tuesday May 29, 2001 @02:26AM (#191865)
    ... from the more prevalent perspective built upon modern day sympathies. Sympathies which didnt apply back then. Or in your case, through the filter of modern American "history," which many people have noted is more an exercise in revisionism than genuine research.

    Yes, many have noted that, including myself who is not an American and not as prone to many of their delusions. (Sorry guys.) Youll find the argument for the dropping of the bomb not only made by American historians, but by British and others if you look.

    While you cant ignore the subjectivity introduced by the background of the person making an argument (or that of the sources they use), but also do not throw aside a persons argument in the hasty thought that they are not intelligent enough to make an effort at objectivity themselves.

    It's funny how when this trait is present in our armies, we call it "courage" or "tenacity" isn't it?

    Except that the level of fanaticism, or "courage" or "tenacity" or whatever else you wish to call it, wasnt there in, say, the European theatre. Theres a difference between fighting courageously and fighting a completely hopeless cause.

    See the contradiction? If they were training all of these suicide pilots, what were they going to suicide in?

    Planes that were already built, and modified to be packed with explosives perhaps? Those modified planes were extremely good bang for the buck: If one got through, you scored one sunken ship. All it took was one hit. Simple economics when youre in dire straits.

    Ah, they were suicide balloonists, trained to float through the skys like a deadly horde of jellyfish, waiting for the chance to swoop down on helpless American fighters and explode.

    Well, more details just to be serious: The balloon idea depended on the time of year: summer. During that time, prevailing winds blew from west to east, and also, the American west coast was experiencing a drier than normal summer, so their forests were like a tinderbox. The balloons were given enough helium to make it to North America, where they would run out and descend. When they got below a certain altitude, the charge would go off and an incendiary burst would result. No really expensive components, no fancy guidance systems. Did they work? No. :) Some balloons DID make it to the states, but most failed to detonate. I think one DID detonate, but it landed in the middle of a ploughed field and caused no major damage. At the time, the farmer and authorities had NO IDEA wtf was going on. :)

    Along with a fair old chunk of the civilian population.

    Regrettable, but as I said, perhaps that loss of life prevented even greater losses. Just something to consider.

    Oh, further: Although some American generals really did just want to "blow stuff up" Im sure, they WERE considering it as a psychological weapon and not just a physical one. They were planning to blow up Kyoto (Japans former capital, and a spritiual center, it wouldve been like dropping the bomb on the Vatican) to really send a message to Japan but recalled that idea, fortunately for us all.

    I wont deny that Hiroshima was a test. (It was selected since it hadnt been bombed much until then and would reveal best the results.) But I wont accept that it was only a test. The drop had a purpose, and that was to end the war. That was by far the primary reason for its use.

  • by Anonymous Coward on Tuesday May 29, 2001 @02:11AM (#191866)
    It's fairly clear why the second bomb was dropped, although these reasons don't stand up brilliantly in hindsight.

    The Japanese civilian leadership wanted to surrender after the first bomb was dropped, but the more powerful military leadership refused. One of the reasons for this was that news didn't get from Hiroshima to Tokyo for at least a day after the first bomb was dropped, something that the american leadership failed to predict. The americans were therefore surprised that the Japanese didn't sue for peace immediately.

    Another reason for dropping the second bomb was that Stalin declared war on Japan just after the Hiroshima bombing, and immediately attacked Japanese positions on mainland Asia. The Americans didn't want Stalin to win too much against Japan (the mindset of the cold war had already started at this point), so it was deemed necessary to get the Japanese to surrender immediately.

    Throughout this you have to remember that six months earlier, the allies had won a war against Germany, with German divisions generally surrendering or retreating after 30% casualties. When the Americans invaded Guam and Saipan, the Japanese troops didn't surrender at all, and after ~90% losses, forced Japanese civilians on the islands to commit suicide rather than be captured, before committing suicide themselves. This event appeared in the American press, and the feeling was that if the Japanese defended a captured territory that strongly, then there was no chance of invading Japan.

    A blockade on Japan would have hurt even more civilians, as food and fuel would have been cut off. Japan gets very cold in winter, and civilian deaths from a blockade would have been much higher than from the two atom bombs.

    Most of this view is explained in "The Making of the Atom Bomb" by Richard Rhodes, which I admit takes an American viewpoint for most of the book, but I would say is fair at explaining the reasons the Americans had for dropping the two bombs.
  • Some balloons DID make it to the states, but most failed to detonate. I think one DID detonate, but it landed in the middle of a ploughed field and caused no major damage. At the time, the farmer and authorities had NO IDEA wtf was going on. :)

    It came down in Oregon. Killed six people. The only deaths as a result of an attack on the mainland during WWII. http://www.wpafb.af.mil/museum/history/wwii/jbb.ht m [af.mil]

  • Indeed, you are correct that it would not destroy the continent outright, but I suspect that the environmental and other collateral damage would be somewhat on par with an asteroid hit.

    In 3001, Clarke writes about an eerie explosion destroying an entire civilization due to mishandling of an extremely powerful energy source 500 lightyears from earth. Contextually, I think that was one of the few bits of the book that moved me much.

    -l

  • Yeah, I should've been more clear. I'd trailed off from the measly 1kg, thinking of larger bits, and didn't type all that out. Oh well.

    -l
  • In the article they are talking about 1 to 1000 grams of antimatter.
    One kilogram of antimatter let loose anywhere on the surface of the Earth, or in the atmosphere, will be enough to destroy an entire continent.
    And I mean thoroughly destroy, like vaporize. That at least was what my sub-atomic-physics professor told me, and he works at Cern. He knows what he's talking about.
    Any macroscopic amount of antimatter is so hideously dangerous to handle, that I can't imagine that it will be stored or produced anywhere on or even NEAR the Earth.

    They will have to produce and store it in orbit.
    And not even in Earth orbit, but rather in Moon orbit.
    ------------------------------------------ --------------
    UNIX isn't dead, it just smells funny...
  • Doing some calculations of my own, I have to concede that I was wrong. It was my prof who said it though, and he was doing these calculations out of the top of his head, "give or take an order of magnitude".
    Anyway, all this released energy is in the form of ultraviolet and gamma radiation, and the primary effect is ionization and a cascade of nuclear reactions (by the gamma rays) (at least, proton annihilation is at lambda=~10^-15 m). The first will generate a lot of heat, and the latter will make a lot of matter radioactive.
    With a nuclear fission explosion, most of the energy is released as kinetic energy of the nuclear fragments. This gives a hot, expanding plasma; an explosion.
    That is quite different from a anti-matter/matter detonation, where ALL of the matter is directly converted to radiation. Half of this radiates off into space, and the other half hits the bedrock. What happens then?
    Maybe my prof had calculated that the bedrock would vaporize or something. I was trying to understand 'quark-bags' at the time, so didn't want to pursue this matter then.

    Not that we're going to see even a microgram of anti-matter anytime soon.
    ------------------------------------------- -------------
    UNIX isn't dead, it just smells funny...
  • all I am saying is if a little plutonium upsets people imagine how they would protest a anit-matter launch that could prolly destroy the state of Flordia

    Well, now that you put it that way, it has my wholehearted support!

    Hell, I'd send 'em even MORE money if one of those launches could take out California ;)

    Your Working Boy,
    - Otis (GAIM: OtisWild)
  • No message here, either :)
  • I don't know a lot about this, but I'd guess that the solar wind must contain some antiparticles as byproducts of fusion reactions.

    Nothing gets out of sun's core fast, and that's where the fusion happens. Even the photons need about a million years until they reach the surface because of the dense gas. If there were any usable anti-particles created there, they wouldn't get far.

    Actually the neutrinos get out without being slowed down, IIRC they are even anti-particles. But apart from their scientific value they are quite worthless.

  • At least anti-hydrogen was built, I don't know if they succeeded with heavier elements.

    That still wouldn't solve any storage problems. It may be electrically neutral, but as soon as it comes to contact with a common atom, the electrons and positrons around the nucleus would annihilate and then the anti-matter nucleus would shoot straight at the matter nucleus and also be annihilated.

  • Yep, putting anti-matter into a storage ring wouldn't mean that it will stay there forever. But with a good enough vacuum you can keep it long enough so that you can use it. If in doubt, take an extra portion for safety.
  • Be careful, you don't want anyone farting on the antimatter, it might cause an explosion the likes of which have never been seen outside of drunken beer bash BBQs.
  • Yes, antimatter as it is currently produced is quite inefficient. However, it is the most compact fuel that exists (in fact, it's the most compact fuel that can exist), so you don't need a whole lot of it. Since your efficiency starts going down exponentially once the mass of fuel is similar to the mass of the payload (and all current rockets are way beyond that point), even a very small amount of antimatter can replace an awful lot of fuel. Of course, what we really ought to be doing is to work for better antimatter manufacturing techniques -- now there is an example on what until recently was nothing but "pie in the sky" basic research now having an obvious application.
  • Well, the key phrase in the article you link is "Energy of a million of volts", or 1 MeV (using particle physics units here). An electron weighs approximately 1/2 MeV, and a proton weighs about 1000 MeV. So if if you wanted to use this new laser acceleration technique, you'd need roughly 1000 of them in a row...needless to say, that's no longer a "tabletop" accelerator. And you'd need to put even more energy into the accelerated protons if you want to get anti-protons, since the probability of generating an anti-proton is so low, and because of the kinematics of fixed target collisions.

    The laser accelerator you link sounds very interesting, and if it becomes widely used, my wild guess is that it could reduce the cost of the accelerator by maybe an order of magnatude (if you're lucky). But we're still talking a huge chunk of change, and then there's all the hardware to collide the beam with a fixed target and filter the products for anti-protons, the cost of which isn't changed by having a cheaper accelerator.

    --Bob

  • by mcelrath ( 8027 ) on Tuesday May 29, 2001 @06:27AM (#191880) Homepage
    The article you linked to produces positrons from photons (femtosecond lasers), which is easy since at high energy a photon will split directly into an electron and positron. Antiprotons weigh 2000 times more than a positron (electron), and they're not fundamental particles. Even if you dumped enough energy into the laser to make antiprotons, you'd get mostly pions, etas, rhos, kaons, etc...and very few antiprotons. Photon "colliders" that would do exactly this are currently under study. But trust me, it wouldn't be an efficent source of antiprotons.

    Antiprotons are currently created by slamming a proton beam into a fixed target (Beryllium, IIRC), which creates a shower of hadronic junk. A very small fraction of that is antiprotons. The junk is filtered to keep the antiprotons, and dump the rest. It's an extremely inefficent and expensive process.

    --Bob

  • An accurate definition of "assault weapon" might read:

    assault weapon n : a light rifle capable of firing more than one bullet in sequence with a single trigger-pull.


    Or, there's the California definition:

    Waah! It looks like one! WAH! WAAAUUGH!


    For what it's worth, all full-auto weapons (capable of firing multiple bullets in sequence with a single trigger-pull) have been heavily regulated in America since the 1930s.

    Clary, I guess this just means I'm agreeing with you...

    Jon Acheson
  • According to our current base of knowledge of physics, antimatter is the end all of power generation. As far as propulsion goes, the biggest, baddest anti-matter drive that we can build can would only theoretically be able to travel us just shy of 1/2 the speed of light.

    Actually, you can get to as high a speed as you like, just like with any other reaction drive. It just takes exponentially more fuel (the 1/e point for the cargo:total mass ratio happens when your ship momentum per unit mass equals the exhaust momentum per unit mass ("momentum per unit mass" is just velocity, for non-relativistic speeds)).

    As for being the "end all of power generation", you're ignoring efficiency of power capture. Most of the energy from matter/antimatter annihilation comes out as gamma rays. You can't focus or reflect gamma rays. The best you could do for an antimatter rocket would be to use a big block of concrete to absorb all of the gamma rays going in one direction, pushing the block (and ship) in the other direction. This is far from being perfectly efficient.

    Some proposed schemes use the mesons and other crud produced by proton/antiproton annihilations as reaction mass, directing them with magnetic fields, but most of the annihilation energy still goes into gamma rays, so you're only capturing a small fraction of the energy for useful thrust.

    According to my own calculations, you *just might* be able to build a fusion drive that's more efficient in practical use than an antimatter drive (because it's not stuck with the very low thrust per unit energy of a photon drive, and can divert most or all of its exhaust in useful directions). Regardless of which is more efficient in practical use, fusion drives will be much, much, much cheaper (production efficiency for antiprotons is *extremely* horrible, and won't be getting much better).

    All of this is ignoring drives that use an external power source, like laser sails or the Bussard ramjets mentioned by another poster.
  • Found this late while browsing through your comment history for signal processing posts. Hopefully you check for replies now and then. A couple of pieces of relevant information:

    Indeed, its manufacture is highly inefficient. In fact, its maximum possible manufacturing efficiency is a mere 50% yield, and such a yeild is beyond the wildest expectations of most scientists. But, there is a much greater inefficiency involved here (actually two of them): acceleration energy and relativistic effects.

    The problem is that antiproton production is something like a million-to-one inefficient. You could still do it, but it would cost far less just to build a laser array to remotely propel a solar sail (for interstellar travel), or to use fusion or fission drives (for interplanetary travel).

    Assuming 100%-efficient magical synthesis of antimatter from electrical energy at 10 cents per kW/hr, it would cost $2.5 trillion per tonne. An antimatter-powered ship capable of interstellar flight within a lifetime would need to have about half its weight as fuel. Antimatter drives have great mass efficiency, but horrible energy efficiency. They work as photon drives; most of your momentum comes out as gamma rays, even with meson production from the antiproton reactions.

    This gives a fuel cost of about $1.25 trillion per tonne of unfuelled craft weight (only half of the fuel is antimatter).

    Plugging in realistic numbers for the cost of antimatter production gives quintillions of dollars. An array of lasers the diameter of Neptune still costs less.

    Re. relativistic effects, you can avoid most of them by limiting your craft velocity to, say, 0.7-0.8c. That gives you a factor of about 1.5 mass increase and time dilation, which doesn't throw off your numbers much.

    Re. carrying your reaction mass with you, you do indeed require exponentially more mass to gain velocity once your fuel mass dominates craft mass. What this in practice means is that instead of picking a speed and finding the required fuel ratio, you should pick a feasible fuel ratio and then find the resulting speed.

    It turns out that a really-well-engineered fusion drive could give you tolerable interstellar travel times (a few generations), for far less cost than an antimatter drive. Or, you could use externally powered systems like solar sails or Bussard ramjets and still save money. The laser sail, at least, could be built with current technology (though it's still expensive as heck).

    For interplanetary travel, a fission or fusion drive is more than adequate.

    Thus, I don't think that antimatter will ever be a practical spacecraft fuel.

    Now, a real issue to be investigated from the sun is (and, please, all ye experts on particle accelerators and animatter production, step in and comment (probably badly, sure, but its an idea)) whether or not you could produce antimatter from solar rays, which travel at a good percentage of the speed of light (sorry, no numbers on me right now). Most high-energy particle emissions from the sun are light nucleii, such as hydrogen and helium, but the sun does eject some denser nucleii. It'd be a free source of high-energy collisions, and you might be able to filter anitmatter from that in a fairly simple, low-weight, free-power (the main reason), low maintinence method, if you could set up simple automation.

    The problem is that in order to produce antiprotons, you need particle energies greater than twice the rest mass of a proton - i.e. greater than about 2 GeV. The particles in the corona and solar wind are almost all of far lower energy, if I understand correctly.
  • Dear god, a tonne of anti-matter???? We're trying to get to stars, not take them out!. All kidding aside, the proposed mission to alpha centauri mentioned in the article - the only mission for which they proposed using pure antimatter/matter annihilation - was to take 1 gram of antimatter, to push a several hundred ton spacecraft at 0.4c to alpha centauri.

    As you noted, they're building an antimatter-triggered fusion drive; different beast. Most of the energy comes from fusion, and most of the craft mass is reaction mass. They're still being very optimistic about their numbers.

    If my old "interstellar drives" post is still on file, it gives the numbers for fusion drives with varying degrees of optimism. The most optimistic would get you a delta-V of 0.14C at 50% fuel.

    That sounds like it's in line with the numbers you're quoting. If you can perfect fusion technology, you won't even need the antimatter.

    The problem is that they're assuming that all of the fusion energy can go to kinetic energy of the reaction products. For most fusion reactions, you lose most of it to gamma rays. Even if you use one of the more difficult reactions and get all of the kinetic energy in the plasma, the plasma will cool *extremely* quickly due to radiative heat emission (rate of radiative heat loss is proportional to the fourth power of the temperature). You'll have to divert the exhaust to its final direction before substantial energy is lost. Good luck.

    Thus, I question how realistic their assumptions are.

    A more realistic fusion drive would just set off fusion bombs and count on most of the energy being emitted as light and gamma rays. Put your ship on one side of the blast, and photon pressure pushes it in the desired direction (at photon drives' horrible energy efficiency).

    This is probably how a realistic pure-antimatter drive would work, too.

    For all practical purposes, without a space elevator, a solar sail is economicly impossible (if it is even feasable, given stability issues), if the issue of lifting material from the earth is required (just think of how much a day's worth of water costs for an astronaut, even including water recycling). The only way to build such a thing would be to do it in space, from asteroids and the like.

    The sailcraft itself would be light enough to build with material from Earth, though you'd still be much better off using a lunar mass-driver to supply it.

    The laser array would have to be built using space-derived mass (though a lunar mass driver would probably be a cheap enough solution). However, if you can afford to build the laser array at all, you can afford to put the required facilities up there.

    it requires a one-time investment in focusable mirrors orbiting near the sun. You take an asteroid and then spin it incredibly quickly (how quickly depending on the dimensions of what you want). You then keep light constantly focused on it at high temperatures. It'll steadily melt inwards, and flatten into a disc (which can then be cut up into sheet metal) after being cooled

    It turns out that space mirrors are quite cheap, actually. You don't need any support structure; just lots of aluminized mylar and lots of spray-foam for structural ribbing.

    Trying to melt and form the entire asteroid at once would probably result it being spun apart into globules (take a hose and shake spinning water blobs into the air for an idea of how this behaves). You could certainly use solar furnaces to aid in melting smaller quantities to smelt or to form by other means, though. This would be by far the cheapest way to melt large amounts of material.

    Larry Niven proposed an interesting variant of your idea in a few of his sci-fi novels - putting water in the core of an asteroid, and then heating it to get it to expand into a bubble of rock to build a colony in. While a neat concept, it would probably also fail due to stability problems.
  • I've never heard of lunar mass drivers before, but I'm quite interested :) Care to elaborate?

    A mass driver is a ground-based device that accelerates cargo to escape speeds. Usually they're based on electrical, magnetic, or electromagentic principles (configured as giant railguns, coilguns, or other such devices).

    The advantage to this is that you don't need to carry any fuel at all with your cargo, so the only energy consumed is that imparted to the useful cargo. This would be atou 60 MJ/kg launching from Earth, or about 3 MJ/kg launching from the moon.

    On Earth, you'd have to worry about heat shielding on the cargo, keeping a barrel around the launch path so you can take out the air or otherwise reduce turbulence, powering the device, and just finding somewhere to put it. On the moon, you have no atmosphere to interfere with things, lots of space to build, and lots of space for solar power generators of various types. Sending material from the lunar surface to lunar orbit or interplanetary space is beautifully easy. This is why the moon is often proposed as a source of raw materials for space-based construction.

    Moving material in from the asteroid belt would be expensive, because there's a great difference in gravitational potential energy between the belt and earth's orbit. You could use a near-earth asteroid to reduce this problem, but the moon's in a very convenient location and facilities there would be useful for many purposes, so IMO it's probably the best choice to supply any construction near Earth.

    Re. mining, it would actually be pretty easy to attach a mining facility to an asteroid, either on the surface or inside the asteroid itself.

    If the asteroid is in danger of crumbling, you can always turn some of its material into fiberglass rope and wrap the asteroid in webbing to keep material from drifting.

    The weak gravity of the asteroid itself is still enough to cause most crumbled material to return eventually (a few hours for a medium-sized asteroid).
  • The way we put men on the moon would be like 15th-century Europeans building a giant slingshot to shoot explorers over the Atlantic. It's an incredible achievement, and it's something to be proud of, but it's not useful.

    Today, we have the technology, knowledge, and infrastructure to do it right. We just don't want to go badly enough.
  • Didn't you read what he wrote? Explosions of that size have occured. People have detonated fusion weapons with a yield greater than the hypothetical kilogram of antimatter. None of the terrible things you talk about happened, it just made a big hole.
  • It's called time dialation jackass. The closer something gets to the speed of light the more ship relative time dialates compared to Earth relative time. If you were traveling at 99.99999%c to someplace. It would seem to you only a couple years went by but to somebody on Earth LOTS of years would have gone by. Fast clocks run slow.
  • Stop crying about antimatter for chrissakes. It would take beaucoup amounts of it to turn into some sort of continent destroying weapon. And a funny thing about particle annihilations is THE VAST AMOUNT OF GAMMA RADIATION RELEASED which basically ionizes just about everything. High energy gamma rays can cause stuff to start transmuting, one caveat of antimatter ractions setting off lithium hydride fuel pellets is the lead shielding slowly starts transmuting into gold after a while and you also end up with fucked up equipment do to the Cherenkov effect. So anyways, antimatter bombs would cost upwards of a hundred billion dollars to produce just one. Even if AM production increased tenfold the price wouldn't drop too much. So a hundred billion dollars for a 40Mt bomb thats not quite as useful as a clean fusion bomb? Yeah right.
    Aside from it not being used as a bomb, antimatter is a very good idea for use in spacecraft. It is the only way to get the energy you need for really long distance travel. And of fucking course any long term exploration projects will have AM production facilities in orbit, not because they're afraid of blowing themselves up but because its more efficient to not have to drag a heavy AM containment bottle up through the atmosphere. I think this will probably take around 50 years even if you account for increased levels of technology. The transition manned orbital stations to high tech production facilities on an extra terrestrial body is very large and requires a good deal of infrastructure to be built up. Before you have regular lunar travel you need craft capable of cheap hypersonic flight; this is the first step which gets alot of mass out of the signifigant part of the atmosphere. Once we're regularly scheduling flights from New York to Tokyo that take under two hours we'll have the capability to start building permenant and industrialized lunar bases. This is still 15 to 20 years off. We're well on our way but it will take time because there is little driving need to enter space in any hardcore fashion; political pressure got us to the moon. In an era of cooperation in space we'll be hard pressed to launch any crash space development projects in the near future. By the way a Saturn-V rocket carries no typical propellent, merely a pressurized container filled with hot air collected from the general hubub caused over the soviets beating the Americans into space.
  • FYI, it's because I have a Karma of over 25 so anything I post automatically gets a +1 rating right from the start (unless I check the "No Score +1 Bonus" box, as I did for this post, since it's not on the article topic). That post wasn't moderated at all, or there would have been a reason given after the number.
    --
  • It's those pesky social engineering issues again. If people are apt to go critical over nuclear power (like I mentioned in comments to the Mars and coffee story a couple weeks back), just think how they'll react to a proposal like this after decades of science fiction and Star Trek conditioning them to think of antimatter as insanely dangerous.
    --
  • Because that's useful.

    -k
  • this is known, as far as i can recall,
    as a DYson drive. Yup, just like the guy who thought up the solar dyson sphere.
  • It's worth noting that an antimatter drive would be efficient in the same way that an electric car is a zero-emission vehicle.

    Once the electricity is in the car or the antimatter in the spacecraft, the system is very efficient/nonpolluting, but the preparatory process of making the electricity/antimatter is still fraught with regular industrial-age inefficiency and pollution. Of course, for a spacecraft this is ideal, as it's a lot more effective to have all the hardware on the ground instead of carrying it with you. I only say this to forestall people talking about such a drive as an ecologically friendly alternative.

    Kevin Fox
    --
  • To your first question:

    Will it ?? Duration of a spaceflight depends on three variables: orbital path chosen, mass of probe, and the level of accelleration required.

    Lets consider a trip to the "heart" of the Oort Cloud, roughly 20 trillion Km out. In such a trip, Earth-Sun distance is trivial. Accellerate halfway, flip, decelerate. Assume flip time is trivial.

    At 10m/sec^2, it's a bit under 3 years (~1035 days). At 1m/sec^2, it's around 9 years (~3270 days).

    Real question is, what kind of acceleration can you get for such a drive, and how much antimatter will you need for antimatter-assisted fission/fusion to sustain such accelerations over the required time. . .

  • I think one DID detonate, but it landed in the middle of a ploughed field and caused no major damage. At the time, the farmer and authorities had NO IDEA wtf was going on. :)

    I believe a school teahcer and a couple of students were killed or injured with the balloon bomb.

  • Furthermore, the losses to the Atomic Bomb were in the region of 35,000 (IIRC). The number of civilian losses in the Tokyo firebombings that occurred a few weeks earlier were in the region of 250,000. Order of magnitude higher. If Japanese leadership was willing to continue the war after that, why would the loss of 35,000 faze them?
    Um, that's actually 350,000 or so.

    But I agree with most of your points. If they hadn't used the bombs, the war in Japan would have been something like Vietnam. Could have been worse in order of magnitude (for both the Japanese and Americans). The battle in Okinawa should also be in perspective when we deal with the decision to use the bombs. If I were in charge of American military, I wouldn't dare to risk my soldiers' life to fight with such a military force who do not care the life of enemies, themselves and even the civilians they are supposed to protect.

    Besides, I am not sure if my father could have survived if the war had not ended in August 1945. He was 14 and his brother (a couple of years older) was being trained for a suicide attack by a wooden boat.

    From what I hear, there was a bigger chance of being starved to death than being killed by bombing, if the war had prolonged.

    He was in Nagasaki on that day. He was supposed to get rations for his family. He was pulling a cart near downtown Nagasaki, when he saw a lone B-29 (should have been three, but he only saw one) flying away after releasing what looked like a canister with a parachute.

    Next thing he knew was that he was blown to a narrow path between buildings by a blast. (Well, this actually saved his life.) He thought there was a bomb exploded right next to him, which it didn't. It was 2.5 km away.

    He was keeping a journal in those days, and he had an entry for that day. The most impressing thing I read there was his completing remark:

    ``What a shame I could not get the ration.''

    They were starving, and he did not know the significane of the event he was experiencing. Or, being able to eat was what survival was for him.

    I do not want to judge what happened in the history. But I feel a little wierd that my existence might be dependent on what killed 150,000 people with a single blast.

  • Despite a 100% matter to energy conversion rate antimatter has got to be one of the most inefficient fuel sources out there when you look at the entire picture! We'd be conserving resources by making coal-powered spaceships...

    But when you think of the sheer amount of fuel necessary to brute force REALLY long-distance missions, the numbers quickly expand exponentially. I keep thinking how big a rocket would be required to lift a saturn-5 into orbit.

    However with antimatter, a kg of antimatter would take you virtually anywhere in the universe and back. Some missions would never be achievable within a human lifespan without antimatter, but with antimatter, high acceleration could be maintained for long long periods of time, significantly shortening the journey.

    So looking at the entire (long-term) picture, antimatter seems like the answer.

    Of course, if we can find replenishable sources of coal on other planets, maybe we'd better go that route... :-)
  • A-bomb survivors have been carefully tracked for mutations. AFAIK only a couple have shown up: about what would be expected from that population anyway.

    Paul

  • The thrust generated will be uprecedented in the use of fuel efficiently. As an example, the space shuttle main engines have a specific impulse (effectively a measure of "bang for your buck", substituting "weight of fuel" for "buck") of 452s while the test engine for an antimatter system would have a specific impulse of over 5000s!

    Sorry, math and physiks is not my strong suit> [snlmm.net], but are you saying that Antimatter is only eleven times more powerful/efficient than rocket engines?(5000/452=11.06)?

    11X is not so many :/ -- even my cdromz is now up to 56X!! Maybe we can use CDROMZ drives for omni-planet exploration one day (when they get to 1,000,000X!! :>)

    one day... :>

  • There are other sides to this though. Eventually, as time and technology progresses, it will become a lot cheaper than it is today to produce anti-matter in quantities sufficient to fuel huge numbers of missions to Mars, Jupiter and beyond. Such technology shouldn't be ditched because of expense when it's potential is so huge.

    As regards the potential use to the military, increased fuel economy in motor vehicles is also beneficial to the military... but because it benefits everybody else also, work in this area continues apace. Nuclear power, much as I dislike it, is clean and efficient and yes it produces a byproduct that can be used in weapons of mass destruction.

    We can't really complain about the potential military uses of new technologies when assault weapons are on sale to Joe Soap in the worlds more powerful country.
  • by Cuchulainn ( 41619 ) on Tuesday May 29, 2001 @01:26AM (#191902)
    If you read more on the site you will see that these people arent planning an engine which uses antimatter as the sole form of propulsion. A slightly better description is "antimatter catalysed fusion". A relatively small amount of antimatter (for second generation engines capable of interstellar travel this would be some micrograms - still many times more than the worlds current yearly production) is used as a catalyst to initiate fusion in lithium hydride pellets (this is the same fuel used in some thermonuclear weapons). The pellets form a plasma (superheated, ionised gas) and it is this plasma which will form the reaction mass. A couple of points to note:
    • The relatively low amount of antimatter used means that, should something go wrong there
    • would be a big explosion, but not the planet devastation that some people seem to be thinking of (we are quite a bit away from strategic am weapons, but probably closer to tactical ones than most people would like to think). It would most likely resemble an unusually efficient explosion of a very large conventional rocket.
    • The thrust generated will be uprecedented in the use of fuel efficiently. As an example, the space shuttle main engines have a specific impulse (effectively a measure of "bang for your buck", substituting "weight of fuel" for "buck") of 452s while the test engine for an antimatter system would have a specific impulse of over 5000s!
  • I think that this would be a good thing to watch occurring. Preferably from a long way away.

    Nuclear explosions, while not being all that good for the environment, do make really impressive movies and pictures. Antimatter being annihilated would probably look cool too.

    Does anyone have any ideas here?

    Ian.
  • "civilian deaths from a blockade would have been much higher than from the two atom bombs."

    Except of course for the effects of radiation that we probably didn't anticipate (there wasn't enough time to bomb Native Americans in New Mexico over several generations to see the effects, oh well). So AFAIK we basically doomed several generations to all sorts of f*cked up genetic problems.
  • "The balloon idea depended on the time of year: summer."

    Don't forget, us Americans had some pretty cockamamie ideas too. For instance, taping explosives to bats...yes *BATS*...and sending them over to Japan. The idea was that since most Japanese buildings were made from light wood and paper, that we could burn them down easily.
  • ... that currently, it's really hard to produce - as the article says there are less than 10 nanograms currently produced each year, and the projected yield from Fermilab's new equipment would be no more than 140ng or so. And this requires huge particle accelerators costing billions of dollars.
    I once read that the main reason it's so slow and expensive to produce antimatter today is that the colliders used to produce it were designed as research tools, not as manufacturing equipment. Apparently there were some proposed designs for space-based colliders, specifically designed for antimatter production, that would be far more efficient, yielding on the order of kilograms per year.
  • But .5 times the speed of light still gets you across solarsystem in 20 hours and even if we assume constant acceleration of 1m/s^2 you can go from earth to pluto in one month. I think that's pretty impressive compared to 10 years on current technology.
  • While we're all talking about potential military misuse of the technology and the destructive power of antimatter, aren't we overlooking one of the coolest things about this research? The second page [psu.edu] of the article talked about one of the side-effects of antimatter production was the creation of O-15 which is used in PET scans.

    Storage of antimatter is a challenging task, but reaps several benefits. One of which is the generation of O15, a radioisotope used for Positron Emission Tomagraphy (PET) of the human brain. Currently, only certain research hospitals across the world have the ability to create Oxygen-15. Due to its portability, a "radioisotope generator" antimatter trap may be transported to more remote areas for patients who cannot reach these hospitals. A second medical application concerns antiproton radiotherapy of tumors. The NASA Penning trap is being designed with these medical applications in mind.

    This fact would potentially offset some of the negatives that antimatter has.

    It amazes me the wonderful side-benefits we get from basic research and space research sometimes. Who would have thought that research on propulsion would provide an alternative means to create a rare but medically necessary element in significant quantities?
  • I seem to recall writing a report on the Penn State research about 4 or 5 years ago... kinda old news.
  • at least it's a 43 Megaton CLEAN explosion, vs a glow-in-the-dark-til-Y3K explosion.. Still a problem, but at least it's over in a few milliseconds :)

    //rdj
  • It was called Project Orion [islandone.org]. It ran for several years in the late 50s and early 60s and was more or less killed off by the nuclear test ban treaty of 1963.

    There was a considerable amount of R&D work, including building of at least one prototype (a scale model, using conventional explosives). IIRC, the Coca-Cola folks provided some expertise in desigining the mechanism to store & release the bombs; vending machines have been doing this for many years. One wonders how much change the pilot would have to carry for a trip to Alpha Centauri...
  • What's got me worried is the intense gamma ray burst that is (allegedly) emitted from a matter / antimatter reaction.

    With a bit of shielding, you could get some astronauts there, but they'd end up with Funny Looking Kids (tm).
  • According to our current base of knowledge of physics, antimatter is the end all of power generation. As far as propulsion goes, the biggest, baddest anti-matter drive that we can build can would only theoretically be able to travel us just shy of 1/2 the speed of light. This assumes the fuel to generate the acceleration is carried by the drive. Obviously, we'll need to cheat relativity somewhere to get around this little problem or devise methods of acceleration which don't carry fuel.
  • by selectspec ( 74651 ) on Tuesday May 29, 2001 @08:24AM (#191914)
    The problem comes down to having to stop and the propellant used in combination with Relativity.

    Bummer #1: You have to stop, so half of your fuel and propelant must be saved in order to stop the craft.

    Bummer #2: You still need to carry propellant (what you are going to push away from) in addition to your fuel. The more propellant you carry the more energy it takes to accelerate the craft. Ultimately, you reach a point at which carrying more propellant will just slow you down more.

    Bummer #3: At .5c relativity predicts your inertial mass will have increased to %150 your mass at rest. So you'll have to %50 more work to accelerate.

    Add these up into a nasty equation, and you get to roughly .5c. If you throw in a passanger, a craft, engines, parts, etc and make the equation slightly more realistic, you get to around .1c.
  • you won't sent a probe with constant acceleration to the Ooort cloudes.
    BTW: if you would do it, you would need less than a year to reach them ... not 50 years.
    Constant acceleration is interesting for manned missions, giving some artificial gravity.
    Of course for a probe send to Alpha Centauri you liked it to be there fast, but you pointed out correctly that you would need an imense amount of AM to have it under constant acceleration. Also you ned some extra mass, like water, as the propellant. Very fast you have hughe masses again.
    Regards,
    angel'o'sphere
  • It's really too bad, because we had the chance to show the world a true "good guys vs bad guys" scenario, and we flubbed it

    I really hate this half ass apologetic bullshit

    We would have been completely justified in carpet bombing the entire country and killing every single Japanese citizen if it would have saved a single Allied life.
    The thing the apologists always forget is that this was their fucking war
    They murdered relatives of mine. Please spare me the bullshit about the innocent civilians as well. They put their government in power and they wanted this war. Their atrocities in Manchuria were as bad if not worse than what the Nazi's did. And don't even talk about their treatment of prisoners of war. They were (and still are to a point) absolutely convinced that it didn't matter what they did to these "subhumans" since they were so superior.
    It is only the fact that the Chinese didn't have the same pull in Congress as the Jewish community that allowed them to this day to avoid responsibility for their actions.

    We (the US) showed them far beyond an ideal good guys vs bad guys scenario. We Rebuilt their fucking country for them, covered all their bills, taught them how to succeed in the modern world, provide their defense. Who the fuck else in the history of the world has done anything approaching that level of charity?!?

    If we had treated them fairly for their disgusting crimes against humanity, treachery, and cowardice we would have done as the Romans in Carthage and devestated their land so that nothing would ever grow there again.
    But we didn't do a fucking thing out of vengeance. If they had won the war (and the after war against Germany cause you know that fight would have happened) then we (non-japanese) would all be dead or enslaved right now. They got off far easier than they deserved.
    ---CONFLICT!!---
  • One other thing to consider is that if you just drop a 1 kg ball of antimatter onto the ground, the entire mass of antimatter isn't going to all annihilate simultaneously, since the outer layer is going to come into contact with matter before the inner part of the antimatter ball is. For the maximum yield, the idea would be to have every particle of antimatter contact an equal-mass particle of matter simultaneously, but that's clearly not a trivial task (if it's even feasible).

    Eventually all of the antimatter in such a "ball" would annihilate with regular matter, but certainly not all at once -- the initial contact with, say, the atmosphere would cause maybe the outer 5% of the antimatter ball to annihilate "simultaneously", however, this would cause a gigantic enough explosion, and the rest of the antimatter would be dispersed into a cloud that, shortly thereafter, would start reacting with atmosphere. It would be an explosion that would take 10-15 seconds to actually occur! :) Sort of like a gigantic sparkler...

    My numbers are probably off but I think my theory is correct. I *think*. :)
  • An antimatter explosion would probably look more or less identical to a nuclear explosion. In fact, any sizable explosion in atmosphere will produce a mushroom cloud; the particle mechanics involved with nuclear and antimatter explosions differ, but the large-scale effect is the emission of lots of EM radiation (light and heat and all across the spectrum), as well as a great deal of kinetic energy (the shockwave). A 20 megaton hydrogen bomb explosion and a 20 megaton antimatter bomb explosion would probably be mostly indistinguishable.
  • An interplanetary spaceship called "ICANN" ?
    Is this some sort of B Ark ?
  • actually that's not true, because at the beginning of August the US only had three nuclear bombs in their enitre arsenal, and they used two of them in combat. remember it took two weeks at minimum to build a complete nuclear device, so basically they just bluffed japan into thinking they had a whole lot more. a bugg
  • "How's the new confinement chamber coming along?"
    "Well... there's good news and there's bad news."
    "What's the good news?"
    "Cheap space travel for all."
    "...and the bad?"
    "Ermm... You'll never know about it..."

  • ...aside from the gamma radiation we'll all be fine. Hmmmmm....

  • Anti-matter propulsion, neural-nanonics, h4wt habitat chyks, Norfolk tears... Bring it all on! Except for the undead. They might ruin it for the good kids.

  • You have on the order of 10^-9 kilos of antimatter

    I think you'll find that you are out by a factor of 1000. The post said 10nano-grammes - not 10nano-kilos. The other point is that should it not be 2x E=mc^2 for AM conversion - as there is 10^-9 grammes of anti-matter and the equivalent matter converted to energy.

  • by spiro_killglance ( 121572 ) on Tuesday May 29, 2001 @12:24AM (#191925) Homepage
    You keep the antiprotons in a vacuum suspended by electric and magnetic fields, for example in a Penning trap.

    Penning trap + diagram [aip.org]

  • Ah, they were suicide balloonists, trained to float through the skys like a deadly horde of jellyfish, waiting for the chance to swoop down on helpless American fighters and explode.
    I sure hope that your attempt at humor since at the time there were two reported cases of these balloons making it to America. PBS' Nova did a special on this back in the early 90s (or late 80s) on the one that killed a group of people in the Pacific North West.
    Anyway, on topic; I think that it's about time that the insurance companies started to take a greater look at the risks of the networked machine. Since the article didn't go into too much detail on how the risk was asset, I'm sure that an NT box behind a properly configured firewall would have the same low-low rates as a Linux box.
  • Look what happened last time we "negotiated" peace and left an aggressor nation unoccupied. It was as I recall from my history classes, that was the end of WWI.
    Funny how if there is a I, there needs to at least be a II. Of course, 52 Million dead later, that war came to a close.

    Fact, 80,000 killed in the first bomb and 70,000 killed in the second bomb.

    Fact, for 3 weeks (in early 1945) american bombers firebombed Tokyo, attacking CIVILIANS, leaving 120,000 dead. While the A-bomb did it in one moment, extreme casualties could have still been inflicted using regular munitions.

    If you take the 1:1 Casualty ratio of the invasions of Okinowa (sp?) and Iwo Jima, and estimate that Japan had 6 million solders on the home islands, with there mountainous terrain, it paints a grip picture. The U.S. only lost about 317,000 dead in WWII.

    Finally Where is your "proof" that the American Government requested peace negotiations one week before they dropped the bomb? Negotiations were attempted before Germany fell (early May, 1945) but with no luck. Where is your evidence that the generals were going to allow their country to "give up"? I would love to see it (or point me in the right direction)

    Disclaimer-I wish the 2nd world war had never happend. IMO-no good came out of it, and it COULD have easily been prevented if the U.S. was a little more proactive in world affairs instead of sitting on there hands for 5+ years. Yes, Hindsight is 20/20, but if the murder of millions of Jews and the invasion of Poland, France, and Russia isn't a sign, then nothing is.
  • First, please tell me where you learned that the U.S. Started Negotiations one week before dropping the bomb. If that is true, then the situation changes. To my knowledge that is not true.

    I think in WWII we did learn from our mistakes. We occupied the agressor countries, and helped rebuild them. (I also think now we should leave Germany and Japan, but that's beside the point) The mistake was this, after WWI we did not occupy Germany. (we also forced them to pay war reparaitions sp? to the tune of $20B)

    Please expand your arguement on why the U.S. should have to risk something in order for it to be war and not murder. By not dropping the bomb, America risked fighting a prolonged invasion of the Japanese homeland, which we can only speculate about the outcome. You looked at it from a Tactical perspective (the single plane), not a Strategic one (further fighting, which could have taken months)

    What is wrong with a deeterministic view of history? I was just quoting casualty figures. Period. Nothing more, nothing less. I don't see what that has to do with free choice. Free choice for who?
  • Wouldnt you be crushed by your own wieght??
  • To put things in perspective, my father remembers Sputnik. My grandfather got around town in a horse and buggy.

    I remember when we had the ability to put men on the moon. makes me feel old.
    _O_

  • Good post :) But, a few comments.

    Dear god, a tonne of anti-matter???? We're trying to get to stars, not take them out!. All kidding aside, the proposed mission to alpha centauri mentioned in the article - the only mission for which they proposed using pure antimatter/matter annihilation - was to take 1 gram of antimatter, to push a several hundred ton spacecraft at 0.4c to alpha centauri.

    A minor nitpick, even our best theories about the production of antimatter couldn't get us above a 50% yield, because whenever we produce an antiproton, we also produce a proton.

    Even still, antimatter for long distances would still be, for all but the biggest cases, too expensive for direct matter/antimatter annihilation, given our current electricity costs and our estimated near-future production efficiencies. However, that wasn't what the article was dealing with - their short-term proposals were for antimatter-induced microfusion/microfission. This deals with only nanograms to milligrams of antimatter. It is much more feasable. :) Microfission/microfusion basicly *is* a fission/fusion drive, but is one that takes no activation energy (apart from the antimatter) and is very easy to control.

    Now I'm curious, let me do a quick search for solar wind energies... Hmm, well, in most places the solar wind is 1GeV or lower... but there are acceleration effects at the heliosphere which produce energies up to 102 GeV (that's a pretty impressive natural particle accelerator!). Anyways, its an idea :)

    - Rei

    P.S. - For all practical purposes, without a space elevator, a solar sail is economicly impossible (if it is even feasable, given stability issues), if the issue of lifting material from the earth is required (just think of how much a day's worth of water costs for an astronaut, even including water recycling). The only way to build such a thing would be to do it in space, from asteroids and the like. I had a theory (others have probably come up with it before, I'm sure :) ) about constructing useful shapes from asteroids... it requires a one-time investment in focusable mirrors orbiting near the sun. You take an asteroid and then spin it incredibly quickly (how quickly depending on the dimensions of what you want). You then keep light constantly focused on it at high temperatures. It'll steadily melt inwards, and flatten into a disc (which can then be cut up into sheet metal) after being cooled (cooling may or may not prove to be difficult to do in a reasonable amount of time). Or, additionally, after being cooled, it can be spun again on a different axis, heated again, and thus formed into a very long rod (only minorly ellyptical) which can be cut up and used. Regardless, I think that'd be our only feasable way to aquire the nessisary quantities of raw materials in space in a reasonable amount of time.
  • Just a couple things.

    1. I've never heard of lunar mass drivers before, but I'm quite interested :) Care to elaborate?

    2. Stability problems are, of course, a big issue. There's a limit to how much rotational force you can supply before impurities, irregularities, and a simple lack of forces holding the asteroid together start causing it to fragment. However, I have little doubt that you can at least stretch one quite notably with a properly calculated rotational speed on a good axis, to bring it down to a workable width, even if not paper-thin :) (mining a whole asteroid is quite difficult, you pretty much need to mine it from the inside so that every action you do doesn't push you away from it) (if it is a disc, it'd be no effort to shoot holes in it while still soft, as an anchor point, or to slice into workable segments with a laser). Additionally, there is one issue I was considering that might arise, which is, if it is thinned to much, I'd imagine it would start to become slightly parabolic from solar wind. No big deal, though :)

    - Rei
  • Wow! That's a great idea! I once toyed with the idea of doing that (from earth), and came to the conclusion that, with all of the wind resistance you'd encounter it wasn't feasable (I never thought about it from a low-g, no atmosphere source :) ). My basic premise was to use a huge rail gun - half in the ground and half above - to propel it - pretty much the simplest way you could convert electricity into vertical thrust rapidly. And, that works even better once you consider how easy it is to collect free electricity on a no-atmosphere body (more sunlight, lower average surface temperatures = far easier to establish a heat differential with mirrors focusing on a single point). Most people, when they think of solar power, simply think of solar cells, but in reality, they're merely the simplest/least complext way to harness electricity from sunlight, not the most efficient. Most large-scale solar power plants on earth are based on mirror arrays. But this would work much better on low-atmosphere bodies. :) (you'd probably want a web of metal running along the surface of the ground to act as a heat sink)

    The only real issue would be to build a self-sustaining colony, an issue I've thought a lot about in the past. What NASA really needs to be spending money on is the advancements in automation needed for this - which have immediate commercial benefits at the same time. Automated mineral collection, automated refining, automated part construction (advancement on 3d printers), automated assembly. All things which have huge benefits for the here and now :) You can't simply rely on sending a team of 200 people there with blow torches and 500 tons of parts to build a sustainable colony (god, we know how bad biosphere experiments failed here on earth, so you better have a lot of mechanical systems to produce your oxygen and such when your "ecosystem" breaks down ;) ) that has enough population and capability to also do mining and to build a large mass driver, in addition to doing repairs, building new things they need that aren't too complex, etc. Without automation increases, with just the bulk-parts-and-people approach, it would cost the GNP of Europe several times over ;) (not just in the parts and weight of people, but in everything needed to keep the people alive until construction is finished and the ecosystem is established - people cost a fortune when they're outside of earth ;) ). But I digress. The key is automation, and Nasa can pay for its research simply by the immediate here-on-earth commercial benefits.

    On the issue of mining asteroids, initially I thought of mining from the inside as being the only feasable issue. Mainly due to the fact that you can't just have a drill-carrying vehicle drive around (well.. in reality, "hop" around) and then drill into the ground. It'd first, whenever it wanted to rip up some rock, need to burn holes into the ground with lasers or the like. Then, it'd need to insert anchors into those holes which grip onto the rock. Then, it could mine around it. Then, when it needed to move, it'd have to do the whole thing over again (eek!). I figured, mine it from the inside, and you can build a scaffolding as you go, and move around along the scaffolding like a warehouse crane. But, then I realized... you could build the scaffolding outside, too :) In fact, that'd probably prove to be the easiest method (and it would look really neat, too!). I wonder what methods SpaceDev (www.spacedev.com) is planning to use for mining that rare-metal rich near-earth asteroid? I should probably check it out :) (if you're not familiar with that story, there's a Near-Earth asteroid that has more gold, platinum, etc, than all of Earth. A private company, SpaceDev, has, as a long range goal, mining it (they currently provide low-cost space solutions for short-term financing)).

    However... you know, I wonder if you're onto something, with the concept that "the weak gravity of the asteroid itself is still enough to cause most crumbled material to return eventually".... I wonder if there is a way to "gently" crumble an asteroid? Then you could leave it alone for a few days, and then come back and sweep up the remains ;) Hmm, I have a feeling I'll be awake thinking about that one tonite, even though I doubt it'll go anywhere :) Of course, I still think it would be neat to run a good physics sim of the concept of melting a spinning asteroid at various speeds to bring it into a moderately thin sheet, and working with that... it'd be nice to know how thin you could get it (for various compositions of metallic asteroids) before it rips itself apart.

    - Rei

  • Ok, first off, a number of people seem to be missing the point on this article (largely because most of them read little more than the introduction, if they made it through that), so I figured I'd cover some of the details better.

    Misconception 1: Antimatter is a poor choice for a propellant because its manufacture is inefficient.

    Indeed, its manufacture is highly inefficient. In fact, its maximum possible manufacturing efficiency is a mere 50% yield, and such a yeild is beyond the wildest expectations of most scientists. But, there is a much greater inefficiency involved here (actually two of them): acceleration energy and relativistic effects. Picture a system where you have 10% of the mass as propellant. Then, you're wasting 10% of your energy merely accelerating the propellant (roughly - the propellant, naturally, will decrease in volume). Now, picture a system where 99% of the mass is propellant. That's a 99% energy loss. Well, even at those weight levels, the best chemical propellants can't get you very fast. To make matters worse, we have relativistic effects which, the faster you go, the larger portion of energy it takes to accelerate you. At 1/2c, energy requirements are doubled. So, mass is an incredibly critical thing. In addition, the speed exhaust particles are propelled is, if anything, more critical, because it sets a maximum theoretical speed for the craft - and for chemical rockets, it is incredibly slow. And to get close to that speed requires massive waste.

    Misconception 2: Antimatter is a great concept for a weapon.

    In actuality, no. Due to the huge manufacturing difficulties mentioned before, it is a poor weapons concept. Even with the proposed efficiency increases, manufacture is expected to cost several billion per gram (a gram of antimatter has roughly the energy potential of 27 of the space shuttle's solid booster rockets). This level of explosive power doesn't really compare at all to a boosted thermonuclear weapon, which isn't that incredibly expensive to build (U235, for boosting, is incredibly cheap, and the rest is a standard hydrogen bomb core). It isn't even that good of an idea for a small stealth weapon, given our current scientific knowledge. Containment for an amount of antimatter that would be enough to take out merely a building hasn't been developed; the smallest containment systems we have for antiprotons are roughly 2m by 1m by 1m. You'd be better off with conventional explosives.

    Misconception 3: Antimatter storage is dangerous

    Not with the amount we're dealing with. The mars mission proposals were planning to use 100 micrograms of antimatter, to start fission/fusion in tiny spheres. If it were to detonate, it'd be a smaller explosion than the challenger had, to say the least. The real worry would be the fissionable material causing a chernobyl-like effect apon a small area (this has happened in the past when we've had nuclear weapons accidentally "detonate" - not a nuclear explosion, of course, but a conventional explosion which scatters the radioactive material around). There'd be no need to do anything like "hiding it behind the moon". We don't worry about space shuttles and satelites blowing up many miles above us. We need to worry even less about this.

    Silly Misconception Someone Made: Antimatter should be manufactured in space so we don't have to ship it up.

    The main concern with shipping things up to space is the mass requirement. The antimatter we're dealing with has almost no mass, relatively - only its containment units do, and they'd need to be brought up even if the antimatter was being produced in space - in addition to *an entire antimatter generation facility*, personell to run it and maintain it, power generation, etc... oy, what an economic nightmare! There are much better things to work on producing in space.

    As for the issue of "converting solar energy to antimatter", well, that's a tricky question. The sun does not release antimatter; that'd be silly. Antimatter has this lovely habit of detonating virtually instant with regular matter (that's why we love it so! :) ). In a chaotic sea of reactions such as the sun, yes, you'll get a little antimatter, and it'll go away just as quickly. Of course, you could harness solar energy to produce antimatter by having a manufacturing station near the sun, but you could harness that energy for a lot of other things too, and we get to the economic feasability issue discussed in the last paragraph.

    Now, a real issue to be investigated from the sun is (and, please, all ye experts on particle accelerators and animatter production, step in and comment (probably badly, sure, but its an idea)) whether or not you could produce antimatter from solar rays, which travel at a good percentage of the speed of light (sorry, no numbers on me right now). Most high-energy particle emissions from the sun are light nucleii, such as hydrogen and helium, but the sun does eject some denser nucleii. It'd be a free source of high-energy collisions, and you might be able to filter anitmatter from that in a fairly simple, low-weight, free-power (the main reason), low maintinence method, if you could set up simple automation. It'd need to automatically stabilize its orbit and adjust its distance from the sun according to conditions, to eject containers from earth when its on the right trajectory, etc, but it is doable. But, in reality, I recommend sticking with antimatter production on earth for now :) I don't see economic viability in bringing it into space at this point.

    - Rei
  • >I've never quite understood this - how can you >store antimatter, why don't the >particle/antiparticle pairs annihilate each >other? I'm grasping at nothingness here, but >I've always visualized antimatter being stored >as a non-gas in a vacuum, out of contact with >the container.

    The trick is to use magnetic confinement, don't allow the antimatter to touch the container.
    Problem is : antimatter produced in accellerators is insanely hot, so you need extremely strong magnetic fields to confine it, at least until you can cool it down. We'll have "regular" nuclear fusion figured out a long time before we can reliably produce antimatter in significant quantities. I'm not even going to mention the safety issues connected to storing considerable amounts of antimatter. Any failure of the confinement field would result in a big badaboom (making Hiroshima look like a fart in a bottle...) - you wouldn't have to much trouble with radiation afterwards though, but when you're vaporised, you tend not to care too much...

  • We can't really complain about the potential military uses of new technologies when assault weapons are on sale to Joe Soap in the worlds more powerful country.
    I'm probably gonna lose some karma, but what the heck.

    Could you define assault weapon? The US Congress has had a hard time doing it, resorting to listing specific weapons by make and model, or enumerating seemingly irrelevant features like flash suppressors and bayonet lugs.

    Hint: If you were going to say an assault weapon is a machine gun, then you miss the point. A military person might expect an assault weapon to be capable of fully automatic fire, but machine guns are not the target of the recent "assault weapon" furor in the US. Fully automatic firearms are already so heavily regulated in the US that it is inpractical for most citizens to own them.

  • by Turing Machine ( 144300 ) on Tuesday May 29, 2001 @01:49AM (#191944)
    One kilogram of antimatter let loose anywhere on the surface of the Earth, or in the atmosphere, will be enough to destroy an entire continent.

    Nope. I think you may have misunderstood what your professor was saying. Total annihilation of 1 kilogram of matter will produce about 8.9E16 Joules of energy (E=mc^2). There are about 4.2E12 Joules in a kiloton of TNT equivalent, so this is roughly equivalent to a 21000 kiloton, or 21 megaton nuclear bomb. A big bang, certainly, but not anywhere near enough to destroy a whole continent. Many nukes of that size (and larger.... 50 MT and up) have been detonated, and as far as I know all the major continents are still here. :-)

    Of course, the kilo of antimatter will also wipe out a kilo of normal matter, doubling the yield, but that's still not enough to vaporize a continent.

  • Well, the last time something was called ICANN, they couldn't. I just hope these guys can...
  • Run the numbers. The amount of energy in any given amount of AM is given by:

    E = m*c^2

    You have on the order of 10^-9 kilos of antimatter, and c ~= 3*10^8, so c^2 ~= 9*10^16. Therefore, the amount of energy is on the order of 10^(16-9) = 10^7 joules.

    So, if you have a spontaneous release of all the antimatter currently in existence, you're talking about the release of a few megajoules of gamma rays. Not too serious, unless you're standing right next to it or are in the immediate vicinity. Certainly not on the order of a tac nuke.

  • I think you'll find that you are out by a factor of 1000.

    Oops. My bad. Should be 10^-12.

    The other point is that should it not be 2x E=mc^2 for AM conversion - as there is 10^-9 grammes of anti-matter and the equivalent matter converted to energy.

    That shouldn't (generally speaking) affect the order of magnitude of the amount of energy produced. Depending on the exact numbers, you'll only get an increase of a factor of 10.

  • by Dan Hayes ( 212400 ) on Tuesday May 29, 2001 @12:02AM (#191969)

    ... that currently, it's really hard to produce - as the article says there are less than 10 nanograms currently produced each year, and the projected yield from Fermilab's new equipment would be no more than 140ng or so. And this requires huge particle accelerators costing billions of dollars.

    And even when you've got these going, the cost to run them is prohibitive. And then there's the problem of keeping them stored for long periods at a time and transporting them. Despite a 100% matter to energy conversion rate antimatter has got to be one of the most inefficient fuel sources out there when you look at the entire picture! We'd be conserving resources by making coal-powered spaceships...

    So Bush is probably going to love this :)

    And an increased capacity to produce antimatter, while way out of our reach at the moment, brings new problems with it. After all, matter-antimatter reactions are far more efficient than even fusion reactions at converting matter to energy, and the military uses for this are obvious, especially to anyone who has read the Night's Dawn trilogy. It wouldn't suprise me if this sort of thing is being investigated somewhere as a speculative new military tool.

    Hopefully, I'm just being paranoid. But given the military's obsession with technological superiority, I doubt it...

  • by sdo1 ( 213835 ) on Tuesday May 29, 2001 @04:23AM (#191970) Journal
    Well, at least when Penn State implodes in on itself and dissapears, we'll have an idea about what happened.

    -S
  • by nick_davison ( 217681 ) on Tuesday May 29, 2001 @11:57AM (#191972)
    For those who don't know...

    The original CAN was built by NASA in the fifties as the prototype crew module for all of the Apollo missions.

    During the late 90s, with the cold war over and budgets dropping, NASA had to make space travel more appealing. As a result, they created the iCAN. Similar to the shuttle, the iCAN's engines, the crew module and all the rest are enclosed in a single module. While it makes upgrading the iCAN harder, it does allow the iCANs to be produced at a lower unit cost. Perhaps the most important advance for the iCAN was the addition of clip on heat shielding that came in a variety of attractive, transulcent shades.

    While the iCAN saved NASA at the time, Russia has been coming up with more and more powerful rockets that, while harder to use, have outpaced the once popular iCAN. As a result, NASA have re-released the iCAN in its new iCAN II form. New features include patterned as well as coloured head shielding and the ability for astronauts to listen to and rip MP3s.

    Note: You will probably see the iCAN II referred to as the ICAN II. Don't be confused by the capitalisation change, it's simply NASA trying to lose the dated late 90's i feel.

  • Umm, exactly what context are we taking this in? You can certainly get fairly close to the speed of light (faster than 1/2, at least) with constant acceleration. Granted, it might take a while with a relatively low thrust drive, but all it requires is enough time and fuel (or a way to make the fuel on the way).

    Then again, I'm more than a bit rusty.
  • by OblongPlatypus ( 233746 ) on Tuesday May 29, 2001 @12:48AM (#191981)

    In Peter Hamilton's Night's Dawn trilogy, they make antimatter in small space stations located very close to the sun. Lots of energy there :)

    Ok maybe "easy" is overstating it, but anyway..

    A much more interesting part of those books is that antimatter is outlawed, due to its potential for mass destruction. I'm no expert on this, but isn't that essentially correct? If larger quantities than a few nanograms are produced, aren't we dealing with something extremely dangerous here?

  • Some researchers have found it may be possible to produce antimatter using femtosecond lasers. Take a look Here [photonics.com].

    Also, for those who didn't understand the linked article too well, there is a nice article [lycos.com] on Lycos.

  • HUMOUR TYPE="in-joke" CLASS="slashdot"
    Hmmm - looks like the ICAN II is not equipped with hexagonal jets. I guess the designers at NASA haven't been spending enough time in 1950s bathrooms to truly understand the subtle complexities of Zarathustra, Odysseyus and why the Trojan horse has "NO MEAT".
    /HUMOUR

  • Sorry to have to correct you on a number of things:

    Just look at Switzerland - the oldest democracy, and they are required to be armed.

    Well actually Switzerland is not the oldest democracy. Anyone who's taken a bit of history knows that Athens was the first state to institute democracy. And even the Roman republic held elections. The first 3 Swiss cantons to create the confederation that eventually grew into the country of Switzerland first banded together in 1391, and the vikings had a system of elected chieftains and kings much earlier than this. As for where one draws the line of real "democracy" - the Swiss have always had a tradition of communal consensus in their government - but there was no established or pan-Swiss standards for this until Napoleon came and reformed the country's federal government in the image of the french republic.

    As for the military tradition here, you're quite right - every man between 18 and 40 is required to do 2 weeks of military service every year. They are required to keep their military weapons and ammunition in their homes so that they can be ready to go to fight at any time. The Swiss Alps are riddled with bunkers, hidden gun batteries, underground tunnels etc. Also every building larger than a house built since the 1950s has to have bomb shelters in the basement - and the local governments maintain lists of how much bomb shelter space there is and who is assigned to what shelters.

    It is interesting to note that the two countries with the lowest rates of violence with firearms in the world are Sweden and Switzerland. Sweden has the lowest personal gun ownership in Europe and Switzerland the highest. Just goes to show what culture does for people.

  • that's an interesting and unusual definition for "oldest". But granted that definition, it still comes down to when you consider a real democracy to begin. Doesn't universal suffrage come into the picture anywhere? Because in Switzerland up until the advent of Napoleon, there was no universal suffrage. There was no common assembly at the federal level - just a very twisted and complex mess of inter-cantonal treaties. And from canton to canton there was no standard of representation - many were governed by "elders" or pseudo-noblemen. Many areas remained under the authority of the church for a long time while still a part of the swiss confederation. While its true that traditionally there was always much more consensus and community input involved than in most feudal states, don't confuse it with full-fleged democracy.

    That being the case, the United States, France and even Great Britain would contend with Switzerland for being the "oldest" democracies.

  • I mean, come on! Even the name sounds desperate. I can just picture it:

    Boss: You've been watching a Star Trek marathon again haven't you? How many times do I have to tell you; you *can't* build anti-matter spacecraft!

    Engineer: I can too! Hey that sounds catchy...
    ________________________________________________ __

  • by megaduck ( 250895 ) <dvarvel AT hotmail DOT com> on Tuesday May 29, 2001 @12:16AM (#191996) Journal

    It blows my mind that we're actually discussing putting a man (or woman) on Mars using an anti-matter propelled craft that will be assembled and launched from an orbiting space station. The fact that we're capable of such a thing absolutely amazes me. It's even more amazing when you realize that space exploration is less than fifty years old.

    To put things in perspective, my father remembers Sputnik. My grandfather got around town in a horse and buggy. I wonder what my kids will get to see...

  • It wouldn't suprise me if this sort of thing is being investigated somewhere as a speculative new military tool.

    Hopefully, I'm just being paranoid. But given the military's obsession with technological superiority, I doubt it...


    I know that I'm going to regret saying this almost as soon as I save it, but I doubt that the US military is looking at making at anti-matter bomb. I mean, realistically speaking, we already have big enough bombs. We already have so much destructive power that we'll never have a need to use even half of it, even in a Really Big War. Building an anti-matter bomb just doesn't make sense, even if we do get more "bang for the buck" than we do with nukes.

    What the military needs is smart weapons. You know the old quote, "Work smarter, not harder." Sure, you could build a single bomb that is capable of levelling a city the size of NYC, Rome, or London. But why? What are the odds that you'll ever need to destroy something that big during combat? The threats to world peace are no longer (for the most part) nations of mindless fanatics. They are individual groups of up to a couple hundred individuals. The weapons that make the most sense are not the ones that indiscriminantly kill hundreds of thousands of people, but the ones that allow you to target a specific building or vehicle in a city filled with hundreds of thousands people.

    Unless, of course, Dubby decides that he needs a way around all those "nook-yoo-ler" weapons treaties (but he's already proven his willingness to break them, so I doubt that's even an issue).

    If you're not paranoid yet, then you're obviously not paying attention.
  • Despite a 100% matter to energy conversion rate antimatter has got to be one of the most inefficient fuel sources out there when you look at the entire picture! We'd be conserving resources by making coal-powered spaceships...

    If we could have done it some other way, NASA wouldn't have needed to put plutonium in their space probes. That was hardly cheap (forget safe), but at the time it was the best way to provide a long term energy source far from the sun. The reason to use antimatter is purely for the amount of energy you can produce per gram by reacting it with matter; the efficiency of the storage/retrieval transaction isn't a concern, as long as enough of the stuff can be produced for a price proportional to the value of the mission.

    If you want to send a ship to another star system, it doesn't matter that you're getting less than 1% of the energy you put into antimatter production, as long as you can produce enough to get the ship there. If interplanetary/stellar travel were to go commercial, they'd have to worry about that.

  • Ok, what we know about modern physics is solely based on experimentation. We don't know why shit works, we just know that is does. Therefore you guys saying this is unfeasable or shouldn't be done, should stfu. Just accept the fact eventually we will be using antimatter drives and be leaving our solar system. Also whoever said it would take a huge amount of time to reach alpha centauri is an idiot. How can it take more years than miles?? Sure it would take a long time, but not billions of trillion of zillions of whatever years. Given constant acceleration and deceleration, prolly take 10-20 years. Which is a long as time, but still no huge ass number like you mentioned. Anyways, I just thought it was funny when you guys were talking like you know shit when I know nobody here does, including myself.
  • Well, maybe they're going to search for new domain names on Jupiter when we run out of them here.

    --
  • by more ( 452266 ) on Tuesday May 29, 2001 @12:54AM (#192030)
    No message.
  • ICANN II just uses 140 nanograms. I wouldn't want it dropped on my house, but it won't vaporize a continent.

  • ICANN II uses 140 nanograms of antimatter for a thirty-day run, but if we want constant acceleration/deceleleration (and I assume we do, so it can reach the Oort Cloud in fifty years), won't it need a lot more antimatter? 140 times 12 gives you the amount of antimatter used in a year, 1680 nanograms. Multiply that by fifty, and you get 84000 nanograms. That still may not sound like a lot, but that's actually a respectable bang - look at the web page mentioned in this news post. Could someone check me, and see if I'm wrong?

  • Okay I'm not sure if anyone has mentioned this or not, but Remeber back in, was it 97?, when seemingly the entire universe was just freaking out over the idea of lauching Plutonium into space in the form of Radioisotope Thermoelectric Generators. Now weather or not the risk was worth it is not my point. My point is, Casssini maybe would have caused a couple of thousand deaths from fallout worst case scenerio, and if I read the article right (as in they may need a kilogram of this stuff) then if this probe/ship messed up ANYTIME during shipment, thats a 43 megaton explosion from what i've heard. Now *I* am not saying we should not advance our technology and explore space, all I am saying is if a little plutonium upsets people imagine how they would protest a anit-matter launch that could prolly destroy the state of Flordia.... Just a thought

God help those who do not help themselves. -- Wilson Mizner

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