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Space Technology

Fuel Free Spacecrafts Using Graphene 265

Posted by samzenpus from the to-the-stars-and-beyond dept.
William Robinson writes: While using a laser to cut a sponge made of crumpled sheets of Graphene oxide, researchers accidentally discovered that it can turn light into motion. As the laser cut into the material, it mysteriously propelled forward. Baffled, researchers investigated further. The Graphene material was put in a vacuum and again shot with a laser. Incredibly, the laser still pushed the sponge forward, and by as much as 40 centimeters. Researchers even got the Graphene to move by focusing ordinary sunlight on it with a lens. Though scientists are not sure why this happens, they are excited with new possibilities such as light propelled spacecraft that does not need fuel.
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Fuel Free Spacecrafts Using Graphene More

Fuel Free Spacecrafts Using Graphene

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  • Can't be fuel-free forever (Score:4, Interesting)

    by Ken_g6 ( 775014 ) on Monday June 01, 2015 @06:12PM (#49818629)

    Instead, they think the graphene absorbs laser energy and builds up a charge of electrons. Eventually it can't hold any more, and extra electrons are released, pushing the sponge in the opposite direction. Although it's not clear why the electrons don't fly off randomly, the team was able to confirm a current flowing away from the graphene as it was exposed to a laser, suggesting this hypothesis is correct (arxiv.org/abs/1505.04254).

    He thinks a graphene-powered spacecraft is an interesting idea, but losing electrons would mean the craft builds up a positive charge that would need to be neutralised, or it could cause damage.

    So they'd need to carry hydrogen and split off its electrons or something to neutralize the charge.

    • Even More Thrust (Score:3, Interesting)

      by Roger W Moore ( 538166 )

      So they'd need to carry hydrogen and split off its electrons or something to neutralize the charge.

      Actually this could provide more thrust. Use sunlight to propel the craft until it has built up a large enough electric charge that the efficiency of the thrust begins to drop (since it will take an increasing amount of energy to expel the electrons from something with a large positive charge) and then introduce a stream of neutral gas into the sponge. This should strip the electrons off the gas and the remaining positively charge ions will then be repelled by the positive graphite and provide even more th

      • Re:Even More Thrust (Score:4, Interesting)

        by Baloroth ( 2370816 ) on Monday June 01, 2015 @07:40PM (#49819111)

        Existing ion thrusters already use ionized Xenon for propulsion, so it's definitely a possibility (charge the graphene using this technique, ionize the Xenon and use that to neutralize the graphene, use the Xenon as ion thruster fuel). However, electrons are very nearly massless, so unless they're somehow exciting them with massive amounts of energy, the propulsion from the electrons is unlikely to be significant.

        • Re:Even More Thrust (Score:4, Insightful)

          by Giant Electronic Bra ( 1229876 ) on Monday June 01, 2015 @09:40PM (#49819601)

          The key point with ion drives is they don't eject charged particles. They strip the electrons from Xe, accelerate it towards a grid anode (essentially this is a lot like a CRT) and then the electrons hook back up with the Xe ions on the way out, neutralizing them. So you end up with a high speed stream of neutral atoms, not ions. The spacecraft never develops an overall charge.

          And lest anyone be fooled, electric charges are VERY powerful, you would generate a negligible amount of delta V before your spacecraft's propulsion system completely stopped working. Nor does any fancy juggling act change that, if you lose negative charges you've got a huge problem.

        • However, electrons are very nearly massless, so unless they're somehow exciting them with massive amounts of energy, the propulsion from the electrons is unlikely to be significant.

          It depends on what you compare it to. Since this process was hitting the graphite with photons it makes sense to compare the thrust produced to that created purely by bouncing photons off a material. Electrons might be light but they have more mass than a photon and so the thrust should be significantly higher.

      • Re:Even More Thrust (Score:5, Informative)

        by Anonymous Coward on Monday June 01, 2015 @08:09PM (#49819227)

        Not any ordinary Xenon, but 136Xe.
        In the various Ion Engines designed, built, and occasionally functioning, 136 Xe is the propulsive gas of choice, and pretty much all of the (Unclassified) Literature on the Subject refer only to it.
        Under Plasma conditions, Xenon is anything but inert, and there is at least one (Relatively) stable 136xe-3He compound that is only chemically stable when Ionized.
        This is also true with certain Helium Hydrides, but for Propulsion purposes, one needs as much Nuclear Mass that is easily Ionized to High Charge States as possible.

        They wouldn't let us play with Radon.

      • Re:Even More Thrust (Score:4, Informative)

        by serviscope_minor ( 664417 ) on Tuesday June 02, 2015 @02:43AM (#49820387) Journal

        Of course this means that you need to have a fuel source but it's likely to be far more efficient than current rocket fuel plus there it no need for it to be something explosive like hydrogen

        I'm assuming we're referring to space propulsion not launch since the former requires very high thrustand so the efficient techniques don't generally work. Given that, Hydrogen isn't explosive: it requires oxygen for that and there's none of that in space. A tank full of liquid hydrogen in space is pretty inert as these things go.

    • What they don't say, is that the graphene sponge was used by Qui-Gon to clean up Anankin's wound. And since the midi-chlorians hate lasers (or light-sabers, for that matter) cutting through them, they preferred to move the sponge away.

      Mystery solved. You heard it here first.

    • Re: (Score:2)

      by T.E.D. ( 34228 )

      So they'd need to carry hydrogen and split off its electrons or something to neutralize the charge.

      Or they could just periodically zap the crap out of nearby objects with all their pent-up charge. It would probably temporarily stop the ship, but every design has its flaws. If we could dig up the Yamamoto and stick one of these engine/gun thingys in it, this could really help save the human race from those pesky Gamelons [wikipedia.org]

  • Explanation seems to violate charge conservation.. (Score:5, Insightful)

    by PaulBu ( 473180 ) on Monday June 01, 2015 @06:12PM (#49818631) Homepage

    Where the heck those extra electrons came from? Absorbing photon momentum (more efficient solar sail) sounds feasible, but "accumulating electrons" from nowhere and then emitting them in one direction (where light came from) ... less so.

    Paul B.

    • Re:Explanation seems to violate charge conservatio (Score:5, Funny)

      by binarylarry ( 1338699 ) on Monday June 01, 2015 @06:19PM (#49818675)

      Lets test your hypothesis by creating a slashdot poll.

    • Re: (Score:2)

      by tomxor ( 2379126 )

      Where the heck those extra electrons came from?..."accumulating electrons" from nowhere and then emitting them in one direction...

      Isn't that the opposite of what the phosphors used in a CRT do when hit by electrons? Is it too much to think the reverse is possible?

      • Re:Explanation seems to violate charge conservatio (Score:5, Informative)

        by PaulBu ( 473180 ) on Monday June 01, 2015 @06:45PM (#49818839) Homepage

        Well, CRT face is (weakly) grounded, so e- kinetic energy can excite atom for subsequent photon emission, but its charge will happily leak into the ground.

        There is no "ground" anywhere next to flying spacecraft!

        Actually, on reading the preprint, yes, electrons come from under the Fermi level, get lost in the process and graphene foam (or, spacecraft carrying it) *will* become charged -- it was pointed out in the article as well, but I did miss it on quick read.

        AC below actually paints a rather dramatic picture of what can happen next! :)

        Paul B.

        • Re: (Score:2)

          by tomxor ( 2379126 )

          Yeah i read that bit too and i get it now... however doesn't that mean the effect also diminishes as the charge builds? eventually completely stopping.

          Sounds like it basically need a battery, i wonder if that could be solved by coupling this with a photovoltaic material? Sorry my solid state physics kinda sucks :P

          • Re: (Score:2)

            by tomxor ( 2379126 )
            LoL... no i does work, photovoltaic and photoelectric are different effects of the same phenomenon right? i guess there is not simple closed form way to get those electrons back without getting all fusiony.

      • Re: (Score:2)

        by tlhIngan ( 30335 )

        Isn't that the opposite of what the phosphors used in a CRT do when hit by electrons? Is it too much to think the reverse is possible?

        No, the electrons go through a circuit, which is the entire point.

        In a CRT, the output of the flyback transformer is a really high voltage, which connects to the CRT face through a heavily insulated plug. If you take a look at any CRT, there's a thick heavy cable in the middle of the body that runs to the flyback transformer. Inside the CRT, the electron gun is at negative po

    • Re: (Score:3, Funny)

      by Anonymous Coward

      Clearly it collects the electrons from the hydrogen particles in the interstellar gas. Of course, the now-charged hydrogen gas follows it around until it gains critical mass and... FOOM! New sun!

    • Maybe from this other recently discovered process?
      http://cleantechnica.com/2013/... [cleantechnica.com]

      • That may be correct but the article you linked has an incredibly misleading title. This process does not convert photons into electrons it simply imparts the photon's energy to one or more electrons which, in the case of thrust, causes them to be ejected from the graphite. The coupling of electrons to photons is extremely well understood, in fact it is the second most accurately tested scientific theory ever discovered (the first being special relativity). The only way to create electrons from photons is to

    • Where the heck those extra electrons came from?

      They could easily come from all the material which is surrounding the graphite. As the charge builds up on the graphite due to all the electrons being expelled it will develop an increasingly strong electric field eventually will pull electrons from the walls of the chamber. Since the vacuum will also not be perfect the remaining gas molecules could also transfer charge by moving back and forth between the graphite and the chamber walls.

      A similar effect exists in the LHC where the electrons are 'helped'

    • Isn't this just plain photoelectric effect but the novel thing is that thrust is generated because the electrons are apparently all released in the same direction?

      So I imagine it isn't really 'fuel free' in the sense of that it would still need some source of electrons eventually.

    • It doesn't 'violate' charge conservation. You build up a positive charge as you run. Pretty soon the positive charge becomes so huge that your thruster ceases to work. You can make it work again by neutralizing your charge.

  • We already have solar sails, but this could make them work much better. Real question is what happens if you paint one side. A solar sail with one side painted and the other painted with graphene might be really cool.

    • A solar sail with one side painted and the other painted with graphene might be really cool.

      Hmmm ... you mean "really cool" in the "it will do more useful stuff" sense of the word? Or in the sense of adding a spoiler and neon running lights to a beat up Honda Civic "might be really cool"?

      Or maybe the painted side could have a jolly roger on it to play space pirate?

      Honestly, is painting one side functional?

      • Or in the sense of adding a spoiler and neon running lights to a beat up Honda Civic "might be really cool"?

        Oh, you've seen my whip. Pretty badass, huh?

      • Or in the sense of adding a spoiler and neon running lights to a beat up Honda Civic "might be really cool"?

        To this [hotrod.com] or this [lucasoil.com] 1999 Civic SI? Sure.

        Running BFG street tires, Eibach coil-over suspension and 17 psi of boost, we ran over 211 mph at Area 52. ... Though the engine has produced as much as 728 hp at 29 psi of boost, the boost was run at only 13-14 psi for the record runs.

        Reportedly, there are (obviously, not completely stock, but many street-legal) Civics out there with 500-1000+ HP.

        • Oh, don't get me wrong .. I get there are some actual badass Civics out there. I've seen all the Fast and the Furious films. ;-)

          But I've also seen the piece of crap cars with all of the stickers and none of the mods with the cheap-ass plastic spoiler held on with duct tape and rolling on bald tires.

          I don't know which of these two painting one side of the graphene this sail gets us.

  • Fuelless (Score:3)

    by Mantrid42 ( 972953 ) on Monday June 01, 2015 @06:14PM (#49818651)
    So it's not really fuel free, the fuel just happens to be on the ground (or wherever you put the laser).

  • As history has shown us (Score:4, Funny)

    by Diac ( 1515711 ) on Monday June 01, 2015 @06:16PM (#49818663)

    All great discoveries can be summed up with three simple letters... WTF

  • "The most exciting phrase to hear in science, the one that heralds new discoveries, is not Eureka! (I found it!) but rather, 'hmm... that's funny...'" - Isaac Asimov

  • Twofer (Score:5, Informative)

    by Dan East ( 318230 ) on Monday June 01, 2015 @07:06PM (#49818929) Journal

    A quick search on converting photons to electrons turned this up:

    http://cleantechnica.com/2013/... [cleantechnica.com]

    A new discovery by researchers at the ICFO has revealed that graphene is even more efficient at converting light into electricity than previously known. Graphene is capable of converting a single photon of light into multiple electrons able to drive electric current.

    So that could be where the extra electrons are coming from.

    • Re: Twofer (Score:3, Informative)

      by Anonymous Coward

      I guess they really mean each photon excited multiple electrons and not creates. It takes a lot more energy to create one.

  • Who cares, it flies! (Score:3)

    by Tablizer ( 95088 ) on Monday June 01, 2015 @07:31PM (#49819057) Journal

    Though scientists are not sure why this happens...

    Combine it with an EM drive: double the speed & double the mystery. Maybe if you mix baffling with confounding you get a multiplier effect instead of just doubling. (That's the way the entropy seems to work with compounded software bugs.)

  • I figured this out when I was like seven years old. You just hook up one of these to a space ship and fly straight to Jupiter.

    https://upload.wikimedia.org/w... [wikimedia.org]

  • I'm just sharing a curious idea that came to my mind while reading the summary, what if we mount laser on the spacecraft that got a "graphene sail". I mean, AFAIK laser doesn't generate any trust (if it was the case, we could probably use fuel-free laser engine). And laser on graphene generate trust.

    Please help me find where's the error, my brain hurt.

    • Re: (Score:2)

      by hey! ( 33014 )

      Well, without actually reading the article itself I'll venture an opinion of course. If you carried the fuel and lasers yourself it wouldn't be like the sailor blowing on his own sail at all; it's be like the sailor facing the stern and blowing his ship forward. That's because the ship would still be powered by the rearward expulsion of electrons.

      The advantage of the system with an external laser is (I presume) that even though it is no doubt very energy inefficient, since all you're expelling is electron

  • light pushes the fins of a radiometer in a vacuum - could this be a similar phenomenon??

    http://upload.wikimedia.org/wi... [wikimedia.org]

  • Achievement unlocked! (Score:5, Funny)

    by Jeremi ( 14640 ) on Monday June 01, 2015 @08:40PM (#49819377) Homepage

    Do you ever get the paranoid feeling that someone is occasionally modifying the laws of physics in order to advance the plot?

    "Oh look, they're going to be stuck on Earth for an excruciatingly long time due to the exponential-propellent-scaling problem. Let's add a new capability to graphene that will give them a work-around for that."

    I claim that two years ago the exact same graphene experiment would have shown no unexpected results; but now in 2015 we see this suspiciously useful behavior appear. I'm not sure how to test my hypothesis though :)

  • As much as 40 cm huh? (Score:5, Funny)

    by mark-t ( 151149 ) <markt AT nerdflat DOT com> on Tuesday June 02, 2015 @01:13AM (#49820213) Journal
    I'm no physicist, but I'm pretty darn sure a spaceship's gotta move a whole lot further tan 40 cm to get anywhere.

    • Re: (Score:2)

      by T.E.D. ( 34228 )
      That's true: An actual physicist would have stated the motion as relative to another object. There's no such thing as absolute motion, unless you still believe in the aether.

      • There's no such thing as absolute motion, unless you still believe in the aether.

        In which case, you're measuring motion relative to the aether.

    • Well, as long as your space travel goal is 40cm or less, we've got you covered!

      It's kind of like expecting to do work on an iPad. Sure, you can do all sorts of things, as long as your standards are low enough and your definition of "work" is exceptionally loose.

  • The plural of craft is crafts - when you're talking about embroidery, woodcarving & the like.

    When you're talking about vessels, it's just craft.

  • I've been hearing about the hypothetical possibility of spacecraft where at least part of the drive capacity is fueled by energy beamed to it from earth or some other large "stationary" (i.e. not attempting to change orbit) object in the form of laser light, for ages.

    That doesn't make this any less neat - it sounds like what they've found, if they can harness it from theoretical science to proper working technology, is a much more *efficient* way of consuming the energy being thus beamed - but the basic ide

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