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Space Technology

ESA Moves Forward on New Electric Engine 201

Posted by ScuttleMonkey from the advanced-thrusting dept.
museumpeace writes to tell us the ESA is reporting that they have confirmed the principle behind a new space thruster. Plasma Double Layers, first discovered by Australian researchers Christine Charles and Rod Boswell, may help to develop a new electric engine that gives more thrust than traditional engines while still maintaining efficiency. From the article: "In essence, a plasma double layer is the electrostatic equivalent of a waterfall. Just as water molecules pick up energy as they fall between the two different heights, so electrically charged particles pick up energy as they travel through the layers of different electrical properties."
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ESA Moves Forward on New Electric Engine More

ESA Moves Forward on New Electric Engine

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  • Does this mean we won't be needing the space elevator? :-)

    • No. (Score:5, Informative)

      by everphilski ( 877346 ) on Wednesday December 14, 2005 @05:50PM (#14259461) Journal
      Because these are very low thrust engines, they can't hold a candle to gravitational forces. Where they shine in interplanetary and stationkeeping (orbit and orientation) applications.

      -everphilski-

      • very low thrust? (Score:3, Insightful)

        by j1m+5n0w ( 749199 )

        Calculations suggest that a helicon double layer thruster would take up a little more space than the main electric thruster on ESA's SMART-1 mission, yet it could potentially deliver many times more thrust at higher powers of up to 100 kW whilst giving a similar fuel efficiency.

        I would hesitate to call this a "very low thrust" engine, since 100kw is somewhere around 140 horsepower. It may not be enough to escape earth's gravity (if not, maybe the mars or the moon?), but I wouldn't discount the possibilit

        • http://www.boeing.com/defense-space/space/propul/ S SME.html [boeing.com] SSME has ~12 *million* horsepower. If you scaled up the ESA's labscale engine - its about maybe a tenth of the size - you are talking about 1,400 horsepower. There is no comparison.

          However in interplanetary space this method of propulsion shines since it is very mass efficient. You can grab a stable fuel source like a noble gas and a long-term energy generator like a nuclear power plant and have a long term voyager-style mission, whereas with con

          • Re:very low thrust? (Score:3, Interesting)

            by j1m+5n0w ( 749199 )

            SSME has ~12 *million* horsepower. If you scaled up the ESA's labscale engine - its about maybe a tenth of the size - you are talking about 1,400 horsepower. There is no comparison.

            I think you're comparing the 815 pound weight of Smart-1 (which is the weight of the whole probe including thrusters, fuel, batteries, scientific equipment, etc...) to the 7,774 pound weight of SSME, without fuel.

            Also, the SSME is built to lift a very heavy space shuttle (and worse, its 4 million pounds of fuel) to orbit. Of

            • Ion engines tend not to work so well in atmospheres anyway. But they're excellent ways to cruise around in space. Especially ones that can generate a bit more thrust than the ones we use now.
        • I would hesitate to call this a "very low thrust" engine, since 100kw is somewhere around 140 horsepower. It may not be enough to escape earth's gravity (if not, maybe the mars or the moon?), but I wouldn't discount the possibility immediately without more information (like what do these thrusters weigh, and how much propellant do they need to carry).

          Once you're in orbit, the amount of thrust becomes a reasonably insignificant detail. The overriding concern is whether or not your craft can produce the neces
          • Once you're in orbit, the amount of thrust becomes a reasonably insignificant detail. The overriding concern is whether or not your craft can produce the necessary Delta-V to reach the required escape trajectory. Since it seems unlikely that the ESA would be investigating these devices as a replacement for ION engines if their performance was sub-par to IONs, it stands to reason that these engines will have no difficulty reaching the required Delta-V.

            Delta v is the main concern, but thrust is important too,

        • Re:very low thrust? (Score:4, Informative)

          by roystgnr ( 4015 ) <roy&stogners,org> on Wednesday December 14, 2005 @07:05PM (#14260015) Homepage
          I would hesitate to call this a "very low thrust" engine, since 100kw is somewhere around 140 horsepower.

          Thrust is not measured in kilowatts (or horsepower, or any unit of power). It's measured in units of force, like Newtons.

          I'd say you're comparing apples to oranges, but it's even worse than that. How is force related to energy? By the equation Energy = Force * Exhaust Velocity. The higher your exhaust velocity is (and on mass-efficient rockets like these, it's huge), the lower your thrust is for the same energy input. Other posters have already pointed out how many orders of magnitude more power typical chemical rockets use, but those huge ratios actually *understate* how much more thrust they produce.
          • Energy = Force * Exhaust Velocity

            As long as I'm nitpicking units, I shouldn't be screwing up my own - that should say Power (energy per time) on the left of the equation, not energy.
          • Supposedly this engine is supposed to have much higher thrust than normal Ion engines... but I can't find anywhere that gives the thrust levels is is theorized to achieve. Low Thrust engines are limited to certain types of interplanetary missions - if this thing can give a higher thrust at a comparable Isp (i.e. fuel efficiency) that would open up all sorts of new uses for electric propulsion (manned mars missions, missions to the outer planets, etc)

            has anyone found a quote for the thrust levels they ex
        • it could potentially deliver many times more thrust at higher powers of up to 100 kW whilst giving a similar fuel efficiency.
          I don't understand this use of the word "efficiency." Are they saying it does much more work with the same amount of fuel? To me that sounds like a great gain in efficiency.
          • I would say that efficiency in this contect is thrust / fuel consumption rate.

            For example, lets say that both engines could get the craft to 20000km/hr. They both use the same mass of propellant, but the new engine gets you up to speed 100 times faster.

          • Re:very low thrust? (Score:3, Informative)

            by Andy Dodd ( 701 )
            The problem with propulsion in space is that not only do you have to worry about energy efficiency, you almost always need to worry about mass efficiency. i.e. how much mass you need to shoot out the back of your spacecraft to make its forward velocity increase by a certain amount. In fact, in the long term for spacecraft that orbit the Earth or operate anywhere near the Sun, mass efficiency is the ONLY thing that matters. You can constantly get energy from the Sun via solar cells, or from a long-lived n
    • Actually, the combination of a space elevator and a good, medium thrust ion engine would be pretty cool. The elevator gets you off the planet (the ion engine can't do that) and gives you a nice initial velocity in the direction of your choice, then you can use the ion engine for maneuvering, changing orbits and slowing down when you get there.

  • A question for the physicists ... (Score:5, Interesting)

    by eldavojohn ( 898314 ) * <eldavojohn@noSpAM.gmail.com> on Wednesday December 14, 2005 @05:46PM (#14259426) Journal
    Ok, I RTFAed so don't be mad at me. I'm still not clear on something though stemming from this excerpt from the article:
    Calculations suggest that a helicon double layer thruster would take up a little more space than the main electric thruster on ESA's SMART-1 mission, yet it could potentially deliver many times more thrust at higher powers of up to 100 kW whilst giving a similar fuel efficiency.
    Is this saying that the energy used to propel the shuttle can now be deferred to depending on an electric source (for the 100kW)? I'm wondering if I should be excited about this new technology or if I should just give them a pat on the back for finding a different and possibly slightly better way to power an engine? I guess it's comparable in size but can rely more on electricity instead of solid fuel for thrust, correct?

    • Re:A question for the physicists ... (Score:5, Informative)

      by Lumpy ( 12016 ) on Wednesday December 14, 2005 @05:53PM (#14259491) Homepage
      Imagine probe. Ok now imagine proe with nicely size Nuclear reactor in place of the big propellant tanks.

      Now imagine voyager rebuilt with this technology and having the ability 30 years later to still apply thrust vectors.

      Understand now? current thrusters are more volatile and are a crap shoot every time they fire them, espically on deep space probes that have not fired the engines in 15 years.

      This has less chances of freezing up, only one valve to worry about and no nasty easy leaking hydrogen. This is something that is really cool for probes and long term missions.

      • Re:A question for the physicists ... (Score:5, Informative)

        by david.given ( 6740 ) <dg@cowlark.com> on Wednesday December 14, 2005 @06:13PM (#14259647) Homepage Journal
        Understand now? current thrusters are more volatile and are a crap shoot every time they fire them, espically on deep space probes that have not fired the engines in 15 years.

        Actually, hydrazine chemical rockets these days are pretty much a solved problem. Cassini's main engine is not substantially different from the Apollo lander's main engine; IIRC, they're hypergolic hydrazine thrusters using helium to pressurise the tanks (and blow the hydrazine out). They're reliable and can cope with long periods of inactivity.

        Of course, they're still chemical rockets, which inherently suck. But they're not nearly as shoddy as you make out.

        • Re:A question for the physicists ... (Score:5, Informative)

          by Lumpy ( 12016 ) on Wednesday December 14, 2005 @06:21PM (#14259713) Homepage
          Every time they fire the thrusters on a probe they hold their breath because the risk of not firing is higher than they like. espically on thrusters that need to be on off on off on off wait 5 years on off on off wait 3 years.... etc.. the more you use it the more you have failures. This setup reduces the failure potential significantly and offers a HUGE advantage of a long thrust period if you need it. Imagine a probe that after hitting the Heliopause that can point it's self in the direction of travel and then kick in the thrusters until all fuel is spent.. this would give it a nice kick to get going out there much faster. heck a voyager probe redesigned with these engines could pass voyager in 1/2 the time it took voyager to get where it is now. There is a huge increase in the amount of thrust (time) compared to the chemical setups.

          rnted when you are out of argon you are done, but it takes much less argon to give you X grams of thrust than it does in a chemical rocket. (chem rockets certianly have a much bigger kick in the pants for a shorter amount of time though)

          • actually chemical rockets are better... (Score:4, Informative)

            by EccentricAnomaly ( 451326 ) on Wednesday December 14, 2005 @09:35PM (#14260725) Homepage
            Cassini has to fire its main engines once every 400 days in order to flush corrosion from the cat beds that might clog the lines otherwise... This has never been much of a problem to do as small maneuvers can be planned without messing up the interplanetary trajectory.

            Actually for interplanetary missions chemical rockets are far less risky than low thrust systems. This is because chemical rockets instantly change you from one safe trajectory to another.. low thrust engines make this change over several days and as a reult there are often periods where if the engine fails the spacecraft would be left on an unstable orbit that is likely to crash into something or be thrown into an escape trajectory. JIMO and Dawn both had major problems trying to design trajectories that always left enough time to recover from possible engine failures without crashing.

            It all comes down to control authority... bigger thrust gives you more control authority and you can much more easily recover from unexpected trajectory perturbations.

        • Of course, they're still chemical rockets, which inherently suck. But they're not nearly as shoddy as you make out.

          So we're talking more of a game of blackjack as opposed to a crap shoot [insidervlv.com]? Sticking with the gambling theme that is.

      • The question that the OP was asking was is this just a better ion engine or is it a real replacement for a chemical engine akin to methane/O2 engine.

        IOW, the OP is simply trying to determine if this is an incremental improvement or major improvement.

        I am not qualified to answer it, but I am sure that others here are. But from what I have read here and elsewhere this is a good deal more than an incremental.
      • Now imagine voyager rebuilt with this technology and having the ability 30 years later to still apply thrust vectors.

        You couldn't fly Voyager with a low thrust engine... or at least it would end up being a much more massive spacecraft and be able to carry fewer instruments. If we built Voyager today it would still have chemical rockets and would be pretty much the same expect for better computers and instruments.
        • Other than the lack of a good electricity source that will last for thirty years in deep space, why couldn't you build a Voyager with ion engines? Or did you mean that to supply juice thirty years after launch you'd probably have to use a nuclear reactor, making the probe heavier?
    • Hmm, 100 kW. not bad for an electric thruster, but still only 134 horsepower. When compared with the Space Shuttle main engine's 12,000,000 horsepower, that isn't very much.
      • Comment removed based on user account deletion

    • Energy sources (Score:5, Informative)

      by everphilski ( 877346 ) on Wednesday December 14, 2005 @05:58PM (#14259538) Journal
      Energy source for the SSME is combustion (Hydrogen and Oxygen)

      Energy source for this engine is electricity, or rather an energy potential... solar cells, nuclear power plant, etc.

      Two different concepts. Two different ballparks. While the article states that this method will deliver "many times more thrust" than ESA's "SMART-1" thruster (70 mN, thats mili-newtons) http://www.aoe.vt.edu/~cdhall/Space/archives/00034 3.html [vt.edu] ... even 10*5 times more thrust is only 5 newtons (read: not much). Scale it up to a SSME sized engine and your talking maybe 25-50 newtons. SSME thrust is measured in MILLIONS of newtons.

      So basically, different tech that won't scale to drive a vehicle out of a gravity well. But it is useful for orbital/stationkeeping/interplanetary maneuvers if you have the time.

      -everphilski-
      • I wonder if it could be used to extend the life of optical reconnaissance satellites.
      • even 10*5 times more thrust is only 5 newtons (read: not much).

        To put this in perspective for the non-physicists amongst us, that's just over half the force of gravity as measured at the Earth's surface. It will *not* get you off the ground, no way, no how.
        • Well, that's not at all obvious. For a 1 kg object, the force due to gravity is 9.8 Newtons. But, for a 2 kg object, the force is double that. Theoretically, if one could make a 5 Newton thruster( and everything else), which was much less than .5 kg, it actually could get off the ground.

          The only problem is that fuel+thruster+nuclear reactor+payload is usually more than one pound. Quite a lot more, in fact. For example, Cassini was about 5600 kilograms, and that ignores an electrical power source suffic
      • Also, there's a much higher terminal velocity for plasma/electric engines than for chemical rockets, because the propellant leaves the nozzle at much higher velocities than exhaust does from a chemical rocket. There's a limit to how fast a chemical rocket can go, theoretically - something along the lines of 25,000-ish miles per hour. The only way to make things go faster than that is to either use gravitational slingshot, or plasma/electric drives, which will have a much higher terminal velocity.

        • Re:Energy sources (Score:3, Insightful)

          by ceoyoyo ( 59147 )
          Exhaust velocity doesn't impose a maximum velocity. Get on a train, stand on a skateboard, throw a basketball and see if you roll in the opposite direction a bit. Even if the train is going faster then you threw the basketball.

          The reason you want an exhaust velocity as fast as possible is that the momentum your ship gains is equal in magnitude (and opposite in direction) to the momentum of your exhaust. Momentum is mass times velocity. Mass is kind of a pain, because you have to accelerate it, so you wa
    • Somehow I doubt this engine will get anything into orbit. I believe the electrical engine in the SMART-1 mission referred to provides a thrust that is equal to the weight of a piece of a4 paper. So delivering many times more thrust would probably add up to a whole stack of paper.

      These engines are usuful in space, though. Probes don't have to bring any fuel, just solar panels.

      Also, an engine can not make something go faster than the speed at which it spews out stuff. The charged particles from on electrical
      • TFA states that Argon gas was pumped into the chamber. So, instead of chemical propellents, does this propulsion system need a constant supply of Argon? I can't imagine there being much Argon out in space to be scooped up in any quantities to replenish that which is used to create the plasma. Anyone with more knowledge care to comment?
        • The advantage of ION engines is the the exit gas is going a so much faster that it provides on the order of 10,000x as much thrust as chemical rocket's gas per unit weight, so you only need ~1/10,000th as much of it. The point is if your old craft was 80% fuel by weight then your new craft can be can have .01% that much propellant and get the same delta V.

          Granted the Argon gas does not provide any energy, but chemical energy storage is not all that efficient when compared to fission or solar power (only
      • Yes, an engine can make something go faster than the speed at which it spews out stuff. However, the faster you spew stuff out, the less stuff you have to spew to change your velocity a given amount.

    • Re:A question for the physicists ... (Score:5, Informative)

      by Millyways ( 262662 ) on Wednesday December 14, 2005 @06:00PM (#14259557) Homepage
      The plasma thruster is designed to deliver low amounts of thrust over long periods of time with low fuel consuption. They are best suited to use on interplanetary probes and that kind of thing, not for reaching escape veolcity.

      One of the most interesting things about this new thruster (developed here at the ANU) is that by using the double layer the need for any metal parts coming in contact with the plasma is reduced. This greatly increases relabily through reduced erosion of the thruster.

      See: http://prl.anu.edu.au/SP3/research/HDLT [anu.edu.au] for more info

    • Re:A question for the physicists ... (Score:5, Informative)

      by lilmouse ( 310335 ) on Wednesday December 14, 2005 @07:05PM (#14260012)
      Ok, a few more answers to your question that I haven't seen yet:

      The plasma drive is good because it's efficient. A chemical rocket is terribly inefficient, so you have to carry a lot more fuel then you'd like to for a given amount of ability to thrust.

      We already have an ion drive that's very efficient, but it's got a *very* low rate of thrust - essentially, it can't accelerate quickly. It's got great mileage, but you it'll take you 10 minutes to go from 25 to 75. The new drive still has great mileage. It's slightly bigger, but you can go from 25 to 75 in only 2.5 minutes (or whatever). To carry the analogy a bit further, a chemical rocket has *terrible* mileage, but you can get to 75 in about 2 seconds...

      Low mileage is great - it means your intersteller probe (or interplanetary probe) can get some really high speeds built up. It just takes a while to get there. However, it doesn't have enuf thrust to get you out of a gravity well - great mileage, but you can't drive up a hill.

      It's a pat on the back for an ion drive that gives many more times the thrust of the old model, which means your probe can do things like turn quicker, get up to speed quicker, and make emergency adjustments a little better (altho if we calculate that badly, you can probably kiss your probe goodbye). Not revolutionary, but a big step.

      The fact that it uses electricity is convenient for a lot of reasons; ion drives are really cool. More information here:

      http://en.wikipedia.org/wiki/Ion_drive [wikipedia.org]

      --LWM

    • It sounds to me... (Score:5, Informative)

      by jd ( 1658 ) <imipak@ y a hoo.com> on Wednesday December 14, 2005 @07:26PM (#14260117) Homepage Journal
      ...that they've rediscovered the tandem accelerator. This is basically two electric grids placed one after the other, arranged in such a way that the first grid gives particles one round of acceleration, but doesn't decelerate the particle on the other side. The second grid then accelerates the particle but again is screened so that it doesn't slow it down once the particle has gone past it.


      The principle was popular in particle accelerators for a while - I worked at Daresbury some time back, which was a 20 MeV tandem accelerator. It's cheap and easy. A variant, only with reversed electrical fields, was used in old-fashioned thermionic valves. In that configuration, they were termed deflection grids. CRTs use the same technology to steer electrons towards the correct place on the screen.


      Not sure why anyone would need to prove the idea would work in space, since we already use the technology in vaccuum and we already know tandem accelerators can produce greater acceleration than a single grid.


      I would be much more interested in knowing if it were practical to ionize oxygen then use this technique to improve the oxygen/nitrogen ratio in the engine. If you could, it would improve engine efficiency and may help in reducing the complexity of the engine electronics and mechanics.

      • I would be much more interested in knowing if it were practical to ionize oxygen then use this technique to improve the oxygen/nitrogen ratio in the engine. If you could, it would improve engine efficiency and may help in reducing the complexity of the engine electronics and mechanics.

        Sorry that I don't remember why (something to do with atomic mass and ionization energy) but, Mercury is the most effective propellant for Ion engines, and Xenon is second, Argon is almost as good as Xenon. They usually use X

      • Re:It sounds to me... (Score:3, Interesting)

        by ceoyoyo ( 59147 )
        Sort of, except there aren't any metal grids. No grids, not so much chance for them to erode away and your engine to break. Apparently you can get a lot more thrust out of it too.

  • Hello!? Ion engines are NOT traditional thrusters. (Score:5, Funny)

    by flowerp ( 512865 ) on Wednesday December 14, 2005 @05:50PM (#14259463)
    Would the article submitter PLEASE not call ion engines "traditional thrusters"?

    Now back to thrusting my girlfriend traditionally.

  • Sweet! (Score:3, Funny)

    by Anonymous Coward on Wednesday December 14, 2005 @05:50PM (#14259468)
    I can't wait to put one of these bad-boys in my Civic!

    • Re:Sweet! (Score:2, Funny)

      by greenegg77 ( 718749 )

      I can't wait to put one of these bad-boys in my Civic!

      And given the 134 horsepower someone else figured out for that engine, you'll like, quadruple your horsepower!

  • Basic kinetics... (Score:4, Insightful)

    by sac13 ( 870194 ) on Wednesday December 14, 2005 @05:55PM (#14259512)
    In essence, a plasma double layer is the electrostatic equivalent of a waterfall. Just as water molecules pick up energy as they fall between the two different heights...

    Water molecules do not pick up energy as they fall. There potential energy is simply converted into kinetic energy. However, they had the energy all along in the form of potential energy.
    • more bad science.... and from the official esa too *tsk* *tsk*

      -everphilski-

    • Re:Basic kinetics... (Score:4, Insightful)

      by iabervon ( 1971 ) on Wednesday December 14, 2005 @07:00PM (#14259985) Homepage Journal
      It's not really meaningful to say that the water molecules had potential energy; the system had potential energy as a result of the water molecules being away from the ground, but falling causes that potential energy to become localized in the water. Of course, there's not much else that can happen to gravitational potential energy in the reference frame of the planet, but in the case of charged particles in electric fields, that potential can come out in lots of ways: like moving the particles, moving the device, or causing current to flow in the device. It doesn't make sense to say that the potential energy is in a particular part of the system, when it can become kinetic energy in any of a number of parts depending on how it is released.

    • Re:Basic kinetics... (Score:3, Insightful)

      by m50d ( 797211 )
      Only some of it, some of it will come from reducing the potential energy of the Earth (in fact you could say that it's only the system as a whole that has potential energy, neither the water drop or the Earth has any in isolation). So looking at the water drop on its own, it's picked up energy.

  • BBC also han an article, with nifty pics too! (Score:5, Informative)

    by Khyras ( 876851 ) <tehshmuck@hotmail.com> on Wednesday December 14, 2005 @06:10PM (#14259628)
    Read about this on the BBC article, with diagram [bbc.co.uk] This morning... Sounds like it's greatest use will be in deep space missions. It still hold potential for other use if we can find a more efficient way to use it.

  • MPDT (Score:4, Interesting)

    by AKAImBatman ( 238306 ) <akaimbatman AT gmail DOT com> on Wednesday December 14, 2005 @06:12PM (#14259634) Homepage Journal
    The real question is: How do these thrusters stack up to MPDTs (Magnetoplasmadynamic thrusters)? The article is light on technical details like Isp, engine life, potential design issues, fuels, etc. MPDT is a great upcoming technology. But if this new tech can best it by having a shorter development track and equivalent performance, then let's leapfrog the MPDT technology altogether! :-)

  • yeah but..... (Score:2, Funny)

    by Anonymous Coward
    ...can it go to Ludicrus Speed?

  • Exactly how is this different from the Ion Engines (Score:3, Interesting)

    by alexfromspace ( 876144 ) on Wednesday December 14, 2005 @06:19PM (#14259700) Homepage Journal
    The ion engines rely on the same principle of accelerating propellant through its electromagnetic properties. Plasma is an ionic gas, and propellant is gas too. The only difference I could imagine is that the method of ionization itself produces thrust. Is this indeed the source of higher energy efficiency? The description of two levels sounds like two varying magnetic fields which cause magnetically charged particles (plasma) to accelerate, and the divergence sounds like magnetism applied to aerodynamics. Perhaps this is another source of higher efficiency. If so, this really is groundbreaking.
  • a new space thruster. Plasma Double Layers, first discovered by Australian researchers Christine Charles and Rod Boswell, may help to develop

    Anyone else notice that these names seem like code references for the Rosecrutians and Roswell? Duh. I've seen TV, I know what's going on, here.

  • still need fuel (Score:3, Insightful)

    by Khashishi ( 775369 ) on Wednesday December 14, 2005 @07:00PM (#14259986) Journal
    Plasma needs to come from somewhere. Even if you have some renewable energy source like a solar panel, eventually you will run out of ions to exhaust.

  • Double Layers Well-known, Still Fascinating (Score:5, Informative)

    by Markus Registrada ( 642224 ) on Wednesday December 14, 2005 @07:47PM (#14260217)
    Charles and Boswell didn't discover double layers in 2003. Double-layers have been known (albeit under various names) for decades. Look closely at a candle flame and you might be able to make out a concentric pair of them. Double layers have also been made in near-vacuum plasma apparatus in laboratories and even in popular toys, for decades, where, incidentally, they accurately model astronomical events at many scales. I wonder what it was those two really did do in 2003...

    (Astronomers are, as a rule, mystified by plasma-dynamic events, leading them to talk about "hot gases", "stellar plumes", "galactic jets", "magnetars", "dark matter", "dark energy", and worse. For most, their only exposure to anything like plasma in school was an unphysical mathematical construct called MHD, so they are worse off than if they'd skipped class. (Hawking is often quoted, with no trace of irony, saying "the greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.") For those of us even a little more familiar with real plasma effects, astronomical press releases are no end of hilarity.)

    Plasma double layers aren't mysterious. They develop naturally as the diffuse particles containing ions tend toward equilibrium. Variation in composition, ionicity, and density in a diffuse plasma gather at boundary layers between regions, making the space between the boundaries much more uniform, and concentrating mass, electric fields, and current flow. Highly-stressed double layers tend to explode; on the sun they call it a "coronal mass ejection". On another star it may be called lots of things.

    In one of those plasma ball toys, you can see double-layer tubes connecting the electrode in the center with the transparent ball. You see them because the current density is high enough to put the plasma it runs through in "glow-discharge" mode, exactly as in a neon sign or St. Elmo's Fire. The other two modes are "invisible" and "arcing". The former is common throughout the universe (and detectable only indirectly, as you might imagine) such as between the earth and the sun, between star systems, and even between galaxies. The latter is what you see in a lightning bolt, on the surface of the sun, or in one of those spotlights they used to use at movie premieres. Astronomical glow-discharge events (with the exception of earth's polar aurorae) are usually confused with "shock waves".

    The most beautiful astronomical glow-discharging double-layer structure I know of is M2-9 in Ophiucus [hubblesite.org]. "In this image, neutral oxygen is shown in red, once-ionized nitrogen in green, and twice-ionized oxygen in blue."

    • Plasma explanation for dark matter? There is no need for mysterious dark matter, or dark energy. Diffuse mass in the universe is subject to non-gravitational forces, sure, but we call 'em "electromagnetic". (Some physicists even studied them in school, evidently as undergrads.)

      It's not just the press releases that are funny. Even the captions on APOD pages get pretty silly.
    • Nice! An electric universe troll got moderated interesting. I can't wait for it to get hit with an insightful mod.
      • Plasma dynamics is not synonymous with "Electric Universe", "Holoscience", nor whichever catastrophism cult you're reviling today. That they have latched onto plasma phenomena means no more than that nature worshippers prefer herbal medicine; herbs came first, and (lately, as of old) are as interesting to Merck. That said, mainstream astronomy does have a problem. If astronomy were a real science, it would engage instead of circling the wagons.

        For a serious peek at the role of plasma dynamics in the sol

  • So, how does this compare... (Score:4, Interesting)

    by wjsteele ( 255130 ) on Wednesday December 14, 2005 @08:05PM (#14260288)
    to the Variable specific impulse magnetoplasma rocket? [wikipedia.org]

    What I'm thinking about is that this "new" Ion engine has a higher thrust and/or a higher specific impusle than a standard Ion engine (like the one on Deep Space 1.) But how does it actually rate against the VASIMR style engine and does it have the flexibility of it? (That is, can it adjust it's SI/Thrust depending on the situation - orbital maneauvering vs. cruising.)

    Bill
  • Rod Boswell and his plasma thruster. He's slow, but he get's 'em there!

  • If you don't know much about the ion engine used in Deep Space I, look here [space.com] before posting.

    The article mentions that this new thruster design's "fuel efficiency" is comparable to the ion engine. This means that it has to propel about the same amount of ionized gas away to get the same amount of thrust (presumably at a similar velocity). However, I didn't see anything about "energy efficiency". Does it require a lot more electricity to get the same amount of thrust? For a space probe, 100kV is a LOT. The D

  • Pick up energy? (Score:3, Insightful)

    by wertarbyte ( 811674 ) on Thursday December 15, 2005 @04:23AM (#14262632) Homepage

    Just as water molecules pick up energy as they fall between the two different heights,

    They are not picking up anything, they are just transforming potential into kinetic energy.

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