Tractor beam is capable of analysing space debris

A team headed by Paul Stysley at NASA’s Goddard Space Flight Center has received $100,000 (£62,777) to study three experimental methods for capturing particles and transporting them via laser light to an instrument.

‘The original thought was that we could use tractor beams for cleaning up orbital debris,’ Stysley said. ‘But to pull something that huge would be almost impossible — at least now. That’s when it [occurred] that perhaps we could use the same approach for sample collection.’

The first experiment centres around an ‘optical tweezers’ method of using two counter-propagating lasers. By alternately strengthening or weakening the intensity of one of the light beams, in effect, heating the air around the trapped particle, researchers have shown in laboratory testing that they can move the particle along the ring’s centre. This technique, however, requires the presence of an atmosphere.

Another technique employs optical solenoid beams whose intensity peaks spiral around the axis of propagation. Testing has shown that the approach can trap and exert a force that drives particles in the opposite direction of the light-beam source. Unlike the optical vortex method, this technique relies solely on electromagnetic effects and could operate in a space vacuum.

The third technique is only theoretical and has never been demonstrated in the laboratory. It involves the use of a Bessel beam, which unlike normal laser beams, appears as rings of light surrounding a central dot. In theory, the laser beam could induce electric and magnetic fields in the path of an object. The spray of light scattered forward by these fields could pull the object backward, against the movement of the beam itself.

‘We want to make sure we thoroughly understand these methods,’ said Stysley. ‘Once we select a technique, we will be in position to then formulate a possible system.’