NASA evaluates tractor beams for sample collection

Posted by Kate Taylor

A team of NASA scientists is looking at ways of using Star Trek-style tractor beams to reel in scientific samples in space.

Paul Stysley and his team are studying three experimental methods for corralling particles and transporting them via laser light to an instrument for analysis.

"Though a mainstay in science fiction, and Star Trek in particular, laser-based trapping isn't fanciful or beyond current technological know-how," says Stysley.

"The original thought was that we could use tractor beams for cleaning up orbital debris. But to pull something that huge would be almost impossible - at least now. That's when it bubbled up that perhaps we could use the same approach for sample collection."

Current techniques such as using aerogel to gather samples have been generally successful, but are costly, and have a limited range and sample rate. A tractor beam, though, could continuously and remotely capture particles over a longer period of time.

The first method the team plans to study is the use of 'optical tweezers', which involves the use of two counter-propagating beams of light. The resulting ring-like geometry confines particles to the dark core of the overlapping beams.

By alternately strengthening or weakening the intensity of one of the light beams - in effect heating the air around the trapped particle - it's possible to move the particle along the ring's center. This technique, however, requires the presence of an atmosphere.

Another technique employs optical solenoid beams, whose intensity peaks spiral around the axis of propagation, creating a force that pulls particles back along the entire beam of light. Unlike the optical vortex method, this technique relies solely on electromagnetic effects and could operate in a vacuum.

The third technique, using a Bessel beam, has never been demonstrated in the lab. While normal laser beams when shined against a wall appear as a small point, Bessel beams generate rings of light surrounding the central dot. 

According to theory, the beam could induce electric and magnetic fields in the path of an object, so that the spray of light scattered forward by these fields pulls the object backward.

"We want to make sure we thoroughly understand these methods. We have hope that one of these will work for our purposes," says team member Barry Coyle.

"We're at the starting gate on this. This is a new application that no one has claimed yet."