Forums

Laser, graphene, propulsion

Started by amdx June 13, 2015
I heard about this on a Science 360 broadcast this morning.
A laser pointed at a graphene sponge propels it forward.
(not quite the same as skysail)
The researchers have several theories as to why.
They do note the sponge emits electrons after being charged with
the laser. My read says the electrons are only emitted from one side, 
the side the laser hits. Hmm?
Also works with focused sunlight and different wavelengths.

My question and it is probably to simple for the researches not to have 
pointed out;
  Does a laser beam have a charge?
If yes, wouldn't the like charges repel, causing the movement?
(negatively charged laser beam negatively charged graphene sponge repel 
each other)


  http://arxiv.org/ftp/arxiv/papers/1505/1505.04254.pdf

               Mikek
On Sat, 13 Jun 2015 07:12:19 -0500, amdx <nojunk@knology.net> Gave us:

>I heard about this on a Science 360 broadcast this morning. >A laser pointed at a graphene sponge propels it forward. >(not quite the same as skysail) >The researchers have several theories as to why. >They do note the sponge emits electrons after being charged with >the laser. My read says the electrons are only emitted from one side, >the side the laser hits. Hmm? >Also works with focused sunlight and different wavelengths. > >My question and it is probably to simple for the researches not to have >pointed out; > Does a laser beam have a charge? >If yes, wouldn't the like charges repel, causing the movement? >(negatively charged laser beam negatively charged graphene sponge repel >each other) >
They did discover that a graphene sheet (read one molecule thick) has a lattice far larger than a Helium atom, yet no Helium will pass through it. They are talking about using it to line balloons with. Perhaps the light impinges in a similar way yet will not pass. "None shall pass..." "Have at ye, then!" "It's merely a flesh wound."
On 6/13/2015 8:12 AM, amdx wrote:
> I heard about this on a Science 360 broadcast this morning. > A laser pointed at a graphene sponge propels it forward. > (not quite the same as skysail) > The researchers have several theories as to why. > They do note the sponge emits electrons after being charged with > the laser. My read says the electrons are only emitted from one side, > the side the laser hits. Hmm? > Also works with focused sunlight and different wavelengths. > > My question and it is probably to simple for the researches not to have > pointed out; > Does a laser beam have a charge? > If yes, wouldn't the like charges repel, causing the movement? > (negatively charged laser beam negatively charged graphene sponge repel > each other) > > http://arxiv.org/ftp/arxiv/papers/1505/1505.04254.pdf > > Mikek
"Bulk graphene." Talk about marketing-speak. (I guess the Chinese funding agencies have gone Hollywood just like ours.) Of course it's useless as a skysail, for two reasons. First, it's actually a rocket mechanism--the thrust is due ejecting mass (electrons). Second, it will charge up very rapidly until the current is reduced to zero. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On a sunny day (Sat, 13 Jun 2015 07:12:19 -0500) it happened amdx
<nojunk@knology.net> wrote in <mlh6kq$a76$1@dont-email.me>:

>I heard about this on a Science 360 broadcast this morning. >A laser pointed at a graphene sponge propels it forward. >(not quite the same as skysail) >The researchers have several theories as to why. >They do note the sponge emits electrons after being charged with >the laser. My read says the electrons are only emitted from one side, >the side the laser hits. Hmm? >Also works with focused sunlight and different wavelengths. > >My question and it is probably to simple for the researches not to have >pointed out; > Does a laser beam have a charge? >If yes, wouldn't the like charges repel, causing the movement? >(negatively charged laser beam negatively charged graphene sponge repel >each other) > > > http://arxiv.org/ftp/arxiv/papers/1505/1505.04254.pdf > > Mikek
Without looking I do remember that burning of material by laser from an object in space causes the action - reaction to push uit away. That is very old and tried. Ahy should sponges be different? \ ---------->[ object ] / -----> motio n <--- ejecta
On Sat, 13 Jun 2015 09:30:48 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> Gave us:

>First, it's actually a rocket mechanism--the thrust is due ejecting mass >(electrons).
The laser makes it FART!
On 6/13/2015 8:58 AM, Jan Panteltje wrote:
> On a sunny day (Sat, 13 Jun 2015 07:12:19 -0500) it happened amdx > <nojunk@knology.net> wrote in <mlh6kq$a76$1@dont-email.me>: > >> I heard about this on a Science 360 broadcast this morning. >> A laser pointed at a graphene sponge propels it forward. >> (not quite the same as skysail) >> The researchers have several theories as to why. >> They do note the sponge emits electrons after being charged with >> the laser. My read says the electrons are only emitted from one side, >> the side the laser hits. Hmm? >> Also works with focused sunlight and different wavelengths. >> >> My question and it is probably to simple for the researches not to have >> pointed out; >> Does a laser beam have a charge? >> If yes, wouldn't the like charges repel, causing the movement? >> (negatively charged laser beam negatively charged graphene sponge repel >> each other) >> >> >> http://arxiv.org/ftp/arxiv/papers/1505/1505.04254.pdf >> >> Mikek > > Without looking I do remember that burning of material by laser > from an object in space causes the action - reaction to push uit away. > That is very old and tried. > Ahy should sponges be different? > > > \ > ---------->[ object ] > / -----> motion > <--- ejecta >
They say it is not burning, 1 watt laser on graphene that has been prepped at 800C. It's an easy read, not that I have a great understanding of the subject. Take a minute and check it out. Mikek --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com
On 6/13/2015 8:30 AM, Phil Hobbs wrote:
> On 6/13/2015 8:12 AM, amdx wrote: >> I heard about this on a Science 360 broadcast this morning. >> A laser pointed at a graphene sponge propels it forward. >> (not quite the same as skysail) >> The researchers have several theories as to why. >> They do note the sponge emits electrons after being charged with >> the laser. My read says the electrons are only emitted from one side, >> the side the laser hits. Hmm? >> Also works with focused sunlight and different wavelengths. >> >> My question and it is probably to simple for the researches not to have >> pointed out; >> Does a laser beam have a charge? >> If yes, wouldn't the like charges repel, causing the movement? >> (negatively charged laser beam negatively charged graphene sponge repel >> each other) >> >> http://arxiv.org/ftp/arxiv/papers/1505/1505.04254.pdf >> >> Mikek >
> "Bulk graphene." Talk about marketing-speak. (I guess the Chinese > funding agencies have gone Hollywood just like ours.) > > Of course it's useless as a skysail, for two reasons. >
Didn't mean to say it was a skysail.
> First, it's actually a rocket mechanism--the thrust is due ejecting mass > (electrons). > > Second, it will charge up very rapidly until the current is reduced to > zero. >
So,you are saying, all the electrons in the graphene will be depleted then you're coasting? That's logical, but, I did not see that the graphene fell in the vertical vacuumed tube because of depletion. See page 4 illustration for Vertical tube, no mention of running out of charge.
> Cheers > > Phil Hobbs > >
--- This email has been checked for viruses by Avast antivirus software. http://www.avast.com
On 6/13/2015 12:01 PM, amdx wrote:
> On 6/13/2015 8:30 AM, Phil Hobbs wrote: >> On 6/13/2015 8:12 AM, amdx wrote: >>> I heard about this on a Science 360 broadcast this morning. >>> A laser pointed at a graphene sponge propels it forward. >>> (not quite the same as skysail) >>> The researchers have several theories as to why. >>> They do note the sponge emits electrons after being charged with >>> the laser. My read says the electrons are only emitted from one side, >>> the side the laser hits. Hmm? >>> Also works with focused sunlight and different wavelengths. >>> >>> My question and it is probably to simple for the researches not to have >>> pointed out; >>> Does a laser beam have a charge? >>> If yes, wouldn't the like charges repel, causing the movement? >>> (negatively charged laser beam negatively charged graphene sponge repel >>> each other) >>> >>> http://arxiv.org/ftp/arxiv/papers/1505/1505.04254.pdf >>> >>> Mikek >> > >> "Bulk graphene." Talk about marketing-speak. (I guess the Chinese >> funding agencies have gone Hollywood just like ours.) >> >> Of course it's useless as a skysail, for two reasons. >> > Didn't mean to say it was a skysail. > >> First, it's actually a rocket mechanism--the thrust is due ejecting mass >> (electrons). >> >> Second, it will charge up very rapidly until the current is reduced to >> zero. >> > > So,you are saying, all the electrons in the graphene will be depleted > then you're coasting?
No, it'll peter out well before that. A 1-cm cube in free space has a capacitance of a bit under 1 pF (a 1-cm radius sphere is 1.12 pF iirc). Saying 1 pF to be generous, it will charge to a million volts after emitting 1 microcoulomb of electrons, which weighs about 5 femtograms. If it's photoemission from visible light that's causing the effect, it'll shut down much earlier than that, at about 2 volts, because the emitted electrons can't have more kinetic energy larger than 2 eV, and so can't escape from the potential well. The mass of an electron (mc**2) is 511 keV, or 9E-31 kg. If KE = 0.5 mv**2 = 2 eV = 3.2E-19 J, the momentum is at most p = mv = sqrt(2 m KE) = sqrt(2 * 9E-31 kg * 3E-19 J) = 8e-25 kg m/s per electron, or 4e-6 kg m/s per coulomb. If the sponge weighs 10 mg (1E-5 kg), that sounds medium zippy--a coulomb of electrons would get the sponge moving at v = p/m = (4E-6 kg m/s)/( 1e-5 kg) = 0.4 m/s. However, at 2 volts that 1 pF only gets you 2 pC, i.e. enough electrons to get the sponge moving at 0.8 pm/s, i.e. one hydrogen atom diameter every two minutes. And it's still rocket propulsion.
> > That's logical, but, I did not see that the graphene fell in the > vertical vacuumed tube because of depletion. > See page 4 illustration for Vertical tube, no mention of running out of > charge. >
There is no way in the world that electron emission from an insulated solid body can support its weight. It's off by many orders of magnitude (see above). The total specific impulse available would support its mass against gravity for 0.8 pm/s / 9.8 m/s**2 = 80 femtoseconds. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On Sat, 13 Jun 2015 09:30:48 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 6/13/2015 8:12 AM, amdx wrote: >> I heard about this on a Science 360 broadcast this morning. >> A laser pointed at a graphene sponge propels it forward. >> (not quite the same as skysail) >> The researchers have several theories as to why. >> They do note the sponge emits electrons after being charged with >> the laser. My read says the electrons are only emitted from one side, >> the side the laser hits. Hmm? >> Also works with focused sunlight and different wavelengths. >> >> My question and it is probably to simple for the researches not to have >> pointed out; >> Does a laser beam have a charge? >> If yes, wouldn't the like charges repel, causing the movement? >> (negatively charged laser beam negatively charged graphene sponge repel >> each other) >> >> http://arxiv.org/ftp/arxiv/papers/1505/1505.04254.pdf >> >> Mikek > >"Bulk graphene." Talk about marketing-speak. (I guess the Chinese >funding agencies have gone Hollywood just like ours.) > >Of course it's useless as a skysail, for two reasons. > >First, it's actually a rocket mechanism--the thrust is due ejecting mass >(electrons). > >Second, it will charge up very rapidly until the current is reduced to zero. > >Cheers > >Phil Hobbs
The classic spinning pinwheel radiometer was assumed to spin from light pressure, until someone noticed that the direction was wrong. It turned out to be a thermal effect against the gas in the bulb. https://en.wikipedia.org/wiki/Radiometer -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Sat, 13 Jun 2015 07:12:19 -0500, amdx <nojunk@knology.net> wrote:

>I heard about this on a Science 360 broadcast this morning. >A laser pointed at a graphene sponge propels it forward. >(not quite the same as skysail) >The researchers have several theories as to why. >They do note the sponge emits electrons after being charged with >the laser. My read says the electrons are only emitted from one side, >the side the laser hits. Hmm? >Also works with focused sunlight and different wavelengths. > >My question and it is probably to simple for the researches not to have >pointed out; > Does a laser beam have a charge? >If yes, wouldn't the like charges repel, causing the movement? >(negatively charged laser beam negatively charged graphene sponge repel >each other) > > > http://arxiv.org/ftp/arxiv/papers/1505/1505.04254.pdf > > Mikek
As Phil notes, the numbers don't work. As far as space propulsion goes, it's just a very inefficient electron gun. Ions work a lot better. A xenon atom has a lot more mass than an electron. To keep the spacecraft from charging up positive, and sucking the electrons back, you need to fire out some protons anyhow. I hope the graphene fad ends soon, along with buckyballs and nanotubes and stuff. I wonder what's next. Fig 1 looks to me like a piston in a cylinder, pressurized from below by crud boiled out from the graphene sponge. -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com