Slashdot Mirror
Fuel Free Spacecrafts Using Graphene
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.
The Slashdot community will receive this news with as much derision and scorn as they did news of EM Drive test results.
Now they just need to figure out how to use this to make hoverboards and we'll be all set.
So they'd need to carry hydrogen and split off its electrons or something to neutralize the charge.
(T>t && O(n)--) == sqrt(666)
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.
In case graphene is reduced by the laser then wouldn't that be the fuel anyway, hmm?
drooling tho ...
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.
excitingthingstodo.blogspot.com
So it's not really fuel free, the fuel just happens to be on the ground (or wherever you put the laser).
In that it fails to mention the object was macro-scale, the resulting movement is greater than that would be expected from momentum of the photons, and was not due to ablation of the material. This is far more interesting that pushing tiny things around with a laser.
TFA (I read it) says the leading theory is the extra force over and above a normal solar sail is coming from ejected electrons. TFA quotes an MIT dude:
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.
All great discoveries can be summed up with three simple letters... WTF
Lets test your hypothesis by creating a slashdot poll.
Mod me down, my New Earth Global Warmingist friends!
material vaporization, electron emission.
Don't waste your vote! Vote for whoever you want, unless you live in a swing state it won't matter anyways
Does this mean we'll finally get a version of the Crookes Radiometer that works as a light pressure engine and not just a heat engine? All this space nonsense is abstract to me, I want something I can hold in my own damn hands!
Has anyone else noticed this is by "researchers" in China? The Chinese have a spotty record (at best) of inventing magical experiments that can't be reproduced by anyone else. This may just turn out to be another perpetual motion machine.
"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
Some days it's just not worth chewing through the restraints.
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?
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!
Getting fuel out of the gravity well is horribly inefficient.
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.
This sounds too good to be true... what can't graphene do? When I saw the summary I thought it must be april 1st. "It's a magic sponge!" I'm not even sure I'd believe this from a journal paper done by western researchers.
A quick search on converting photons to electrons turned this up:
http://cleantechnica.com/2013/...
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.
Better known as 318230.
Maybe from this other recently discovered process?
http://cleantechnica.com/2013/...
Better known as 318230.
is this some kind of piezoelectric effect?
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 thrust.
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 - you could probably use Xenon which is a noble gas and so extremely inert and so a lot safer.
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.)
Table-ized A.I.
isn't this already know? how is this different to a light sail?
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...
You are welcome on my lawn.
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' to leave the walls by synchrotron radiation hitting the walls of the beam pipe and are then dragged along by the electric field of a bunch of protons forming a electron cloud. This effect is one of the primary limiting factors on the number of protons we can have in an LHC beam.
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 also create an equal number of positrons. However this requires far higher energy processes ~1 MeV of energy which is many orders of magnitude higher than the energies involved in visible light and would easily break apart graphite which is something they ruled out.
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.
I looked up and found graphene sponge is lighter than Helium. No wonder when laser falls on it, it moves! Whatever magic there might be, it has to obey the principal of momentum. I don't think this would be any different than solar sail, as far as result goes, but one can theorize anything about how it works.
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.
Elok
light pushes the fins of a radiometer in a vacuum - could this be a similar phenomenon??
http://upload.wikimedia.org/wi...
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 :)
I don't care if it's 90,000 hectares. That lake was not my doing.
> that does not need fuel.
How do you power the laser then?
Cue universe reboot anytime now.
Can't the electrons be harvested for electrical power.
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.
A fool and his hard drive are soon parted.
How is this different than a Mylar solar sail?
the sun pushing a solar sail, a laser pushing graphene.
difference?
Who needs a positive charge when traveling through space. Maybe they could bring a bucket of negative charge, to soak the sponges in. When the bucket runs low they could scoop up some more negativity, rinse and repeat.
Another option is balloons. Rub them on the sponges and stick them to the walls.
related? http://en.wikipedia.org/wiki/R...
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.
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 potential and it's slowly accelerated past the deflection coils, then it basically accelerates due to the electric field from the gun to the front of the screen. It hits the phosphor which imparts energy into the phoshor atoms which then do the whole higher-energy state thing and they drop back down to ground state that emits a photon of a specific color.
The electron that hit the phosphor returns back via that nice flyback cable to complete the circuit. Otherwise the screen wouild quickly dim as the phosphor layer takes on a highly negative charge.
Yes, I got the polarities right. Remember electrons flow from negative to positive.
Wouldn't the absorption of the photon actually make a solar sail less efficient? With highly reflective solar sail you get about double the energy of incoming photons.
Suddenly splar sails are starting to look mighty nice for spacecrafts near earth..
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.
File under 'M' for 'Manic ranting'
Finally?
Do you ever get the paranoid feeling that someone is occasionally modifying the laws of physics in order to advance the plot?
Only when I observe the magnetic pattern of the sea floor, and realize we're more than 500,000 years overdue for a magnetic pole flip -- stopped flipping about the same time life demonstrated intelligence. I hope we don't have to pay back the "good fortune" of having our cosmic-ray-shield maintained. Oh, I also get a bit paranoid when thinking of how much it would cost to break up that would-be planet between Mars and Jupiter into manageable chunks for manufacturing materials with no gravity-well tax. And, also when I think about how we have more water cached in Ceres (dwarf planet in the asteroid belt) than exists on Earth, that's just too much "good luck", there's got to be a catch. I hope they didn't have to tow the no-EM-field sparse atmosphere training ground (Mars) very far, it is just about perfect for figuring out how to live in the next step outwards (asteroid belt). How much would a moon full of methane go for on the intergalactic market, do you think? What about a sub-brown dwarf (Jupiter) to complete a gravometric laboratory kit? Saturn's got diamond rain... yikes. Surely they can't charge us for that absolutely huge moon made of the same exact elements as Earth with features clearly visible with the naked eye beaconing us to take a closer look and make the first steps along the red carpet to the stars that's apparently been rolled out for us. The welcome sign has to at least be free, right?
I do believe the Anthropic Principal is enough to explain how we were so "lucky" to find ourselves springing to life in the lush environment of a Goldilocks Zone, but when I examine the rest of this solar system it just seems way too conveniently laid out for us. It's uncanny how if I were to design a solar system for a space faring race to emerge from, this one would pretty much fit the bill completely.
Looks quite similar to the effect that drives a Crookes radiometer (which takes advantage of the fact that it is quite hard to get a perfect vacuum, and works be heating the residual air in the chamber slightly on the hot side). Especially when you consider that graphene sheets have extremely low mass it does not take much energy to heat it to incredible temperatures...
Would be interesting to see how varying the gas pressure in their rig changes the results.
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.
So they discovered that if you shoot something at something, something moves? Is one of them named Zeke, and was the discovery made in his backyard?
Good explanation thanks.
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
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.
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.
At the bottom of the
This story reads more like a spoof, fake or April Fool. Can someone confirm it's neither?
Perhaps this technology can be disruptive in the solar panel construction.
They just have to collect the expelled electrons and fuel them back to the graphene.
I'm pretty sure Galileo wasn't attacked by the church for any of his scientific work.
[ Confidence. The delusion that one knows more than they really do. ]
http://en.wikipedia.org/wiki/S...
Graphene. Layered lubricant. Heat. Vibration within the bulk. So when you have vibrating layers on something (think of a sidewinder) you can have movement.
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.
Is it just my observation, or are there way too many stupid people in the world?
Has this been confirmed by a second party ?
If the graphene is throwing off electrons to generate the propulsive force, it hardly seems likely that this could provide a long term propulsion system. If you add photons to graphene and emit electrons, wouldn't the graphene get seriously positively charged, which should limit how many more electrons can get thrown off?
Only when I observe the magnetic pattern of the sea floor, and realize we're more than 500,000 years overdue for a magnetic pole flip ...
The underlying process seems to be random, so we're not necessarily 500,000 years 'overdue'.
The recent weakening is 'within spec'. If it does flip, it could do so rather quickly.
Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
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 idea of creating such a spacecraft is not new. Still cool though, if it makes the idea more likely to actually be attempted.
it's stuff like this that makes science interesting and fun.
see something odd ball happening,
test, test, and test again to make sure it's happening,
tell everyone that you are seeing this,
let them test it to...
someone's bound to figure out why, and they
get the co-explanation.
someone else get's to figure out how to use it,
everyone wins.
if you see me, smile and say hello.
What I understand is that the lasered piece of graphene shoots out electrons, creating a thrust. But what happens when there are no more electrons ?
Moreover, stripping off all these electrons will ionize the material, which would either cause nuclei to detach as well (like with a plasma thruster) or the resulting positive charge will eventually end up pulling back all the ejected electrons, negating the thrust.
Cue the speed of light jokes....
There was no "ground" anywhere next to my computer when I had it running from a battery-powered inverter, but the CRT monitor worked fine in this arrangement and I don't glow in the dark.
Kid-proof tablet..
This story reminds me of the Crooke's radiometer I had as a child, spinning rapidly (and I really mean rapidly) whenever I place it in sunlight. Check out this site for explanation of Crooke's radiometer (or light-mill). Note: the explanation does not involve electrons.
http://math.ucr.edu/home/baez/physics/General/LightMill/light-mill.html
The fact that the apparent diameter of the Moon and the Sun are virtually the same, resulting in nearly perfect solar eclipses, is also rather surprising, although I don't know that any science breakthrough comes out of that. (Lots of beauty, for those who can fly their Learjet up to Nova Scotia to see the total eclipse of the sun. Also nice if you want to avoid being burned at the stake by King Arthur. And I suppose that's how the Sun's corona was discovered.)
Wait. I'm confused. If it's spitting out electrons that are *part* of it, yes, it'd go positive. It'd also be losing mass (and changing composition) which puts it right back into the "I am fuel and will run out" category.
But if the electrons are merely the photons re-directed out one edge here, then it's a conduit, like a wire, not a charge reservoir or source. Just as a wire doesn't constantly gain positive charge because electrons are moving along it, I don't see why this stuff would either.
And if the photons are coming from outside... well, there's no reason for something that arrives and then leaves to change the net charge of the thing it is passing through/by/along/whatever. Again, just like a wire.
Or do I have this all wrong?
I've fallen off your lawn, and I can't get up.
Don't you just love it with the smell of freshly butchered English in the air ? By the way, there is no plural of Concierge or Aircraft either. Savages.
This kind of 'thruster' simply can't work in any practical way.
Actually that depends. As you remove the electrons the charge will build up which means that you have an increasing electric field. Providing that you kick out the electrons with sufficient energy to escape the field the field will continue increasing and will reach the point where it will breakdown even in vacuum.
For a high enough field strength virtual electron-positron pairs will gain sufficient energy as they are pulled apart to become real. The electron will be attracted back to the craft to neutralize some of the positive charge there and the positron will be repelled out into space creating even more thrust. The result is that after achieving a critical charge the charge will stop increasing.
However you will need a huge charge build up to get this far and you would probably need high energy gamma rays to give the electrons sufficient energy to escape the intense electric field required (otherwise they will not leave the material). Since you are, at this point, essentially converting energy into mass and flinging it out the back of the craft I also expect that your net thrust would be no different than just reflecting the incident photons.
For a solar sail, absorbing the photons would reduce the efficiency, and your ability to steer.