Nature inspires new satellite docking method

Researchers at the University of Washington have found that beds of thousands of tiny pulsating artificial ‘hairs’ can provide a precise method for steering small satellites to docking stations on larger vessels.

Beds of thousands of tiny pulsating artificial ‘hairs’ can provide a precise method for steering small satellites to docking stations on larger vessels, according to a study led by researchers at the University of Washington.

The technique is inspired by biology, patterned after the action of the small hairs, or cilia, that line the windpipe and keep it clear of mucus.

It could come into wide use in future space missions as technicians begin to deploy swarms of ‘picosatellites’, which are tiny spacecraft small enough to fit in the palm of one’s hand. According to Karl Böhringer, assistant professor of electrical engineering and leader of the effort to adapt the technology for use in space, picosatellites are designed to do maintenance, repair and observation work for larger satellites or space stations.

‘Such small satellites will have to dock frequently and quickly for refuelling or to download data,’ Böhringer said. ‘This appears to be a very quick, efficient way to accomplish that. In addition, the space cilia are lightweight and relatively low cost.’ The microcilia were originally developed by Gregory Kovacs and John Suh at Stanford University with funding from the US Defence Advanced Research Projects Agency (DARPA).

In creating the devices, Suh deposited layers of a polymer on a flat silicon plate and then, using micromachining processes, carved out units, or cells, containing four cilia each, which are 0.5 millimetres tall.

Each cilium contains a titanium-tungsten heating element. When at rest, the cilia curve up and away from the silicon plate, but when current is applied to the heating element the cilia are forced to flatten. By turning cilia facing the same direction on and off in sequence, Böhringer can reportedly prompt them to act like thousands of tiny fingers that move in pulsating waves to nudge objects in any of eight directions.

Böhringer, UW graduate student Mason Terry and recent graduate Joel Reiter tested the cilia’s potential using an air table to simulate the weak gravity of space and a small aluminium block as a picosatellite.

In experiments, the cilia arrays were able to manoeuvre the block. Böhringer calculates that a patch of cilia 50 centimetres across would be adequate to steer a 40-kilogram satellite.

The one downside, he said, was that the process used more electricity than he would have liked. However, he is confident that can be addressed with some design changes.

‘We’ve shown that this is workable, which is the important thing,’ he said. ‘Now we’ll just have to wait to see if this is the direction agencies like NASA and the Air Force want to go.’