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  (Source: SlashGear)
The $100,000 award will be used to analyze three laser-based tractor beam techniques, which could gather sample materials in future missions

Optical tweezers have been moving particles for years, and tractor beams are nothing new either. For instance, scientists at the Australian National University announced last year that they were working on a tractor beam method that could move objects over a distance of a meter and a half through the power of light.
 
But tractor beams, for the most part, have only been published ideas that never materialized. NASA is now looking to change that.
 
NASA has funded a study where a $100,000 award will be used to analyze three laser-based tractor beam techniques, which could gather sample materials in future missions.
 
The award was given to Dr. Paul Stysley, of NASA’s Goddard Space Flight Center, and his group, who have found three potential approaches that could bring science fiction to reality.
 
"Though a mainstay in science fiction, and Star Trek in particular, laser-based trapping isn't fanciful or beyond current technological know-how," said Stysley. “Current techniques have proven to be largely successful, but they are limited by high costs and limited range and sample rate. An optical-trapping system, on the other hand, could grab desired molecules from the upper atmosphere on an orbiting spacecraft or trap them from the ground or lower atmosphere from a lander. In other words, they could continuously and remotely capture particles over a longer period of time, which would enhance science goals and reduce mission risk."
 
The first technique involves optical tweezers, where objects can be trapped in the focus of either one or two laser beams. The only noted problem with this method is that an atmosphere is needed to conduct the technique.
 
The other two techniques entail solenoid beams and Bessel beams, which are two specially shaped laser beams. A beam’s intensity usually peaks at its center and tails off gradually, but in a solenoid beam, the intensity peaks in a spiral around the line of the beam. In a Bessel beam, the intensity rises and falls in peaks at higher distances from the beam’s line.
 
While solenoid beams have already showed their usefulness as tractor beams in labs, NASA scientists have their work cut out for them with Bessel beams, which have not been proven as far as tractor beam abilities go.

Source: BBC News



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RE: how do they work?
By Shig on 11/2/2011 3:37:54 PM , Rating: 2
I pulled this from another site, but I don't really understand it.

"Fudan University scientists have worked out how to generate a backward pulling force from a forward propagating beam.

it works only for beams in which the momentum in the direction of propagation is small, as is the case for beams that merely glance off an object. Second, the photons must simultaneously excite several multipoles within the particle, which scatter the beam.

If the scattering angle is just right, the total momentum in the direction of propagation can be negative, meaning the particle is pulled back towards the source and the light becomes a tractor beam."

http://www.technologyreview.com/blog/arxiv/26448/

They mention three techniques, no idea about the other ones.


RE: how do they work?
By AnnihilatorX on 11/3/2011 7:51:36 AM , Rating: 2
The original paper on that link is available in pdf format, it's very Mathematics heavy.

It's something to do with scattering by Bessel beams, and due to its property, at certain angle the scattering will produce a resultant backward force.

If you think sail boat can travel against the wind, the result is not as hard to believe.
http://demonstrations.wolfram.com/SailingAgainstTh...
While in a sail boat the surrounding water gives a helping hand in form of reaction force, I'd imagine in the tractor beam case the scattering force.

So analogy wise:

Wind <-> Propagation beam
Water reaction force <-> Scattering force
Wind direction <-> Propagation beam angle

That's what I think is happening


RE: how do they work?
By YashBudini on 11/4/2011 1:01:32 AM , Rating: 2
You used water reaction force as an example of a scattering force?

The fart scene in Blazing Saddles, now that's a scattering force.


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