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October 17, 2011

Laser activated ablation propulsion could rescue astronauts and move space junk

New Scientist - In Sinko's original plan for removing space junk, spacecraft carry thrusters with two types of propellant, each responding to a different laser wavelength. To fire a thruster, a laser beam is shone on it, vaporising propellant to create thrust and so push the spacecraft onto a new course. The propellants fire in different directions, so the spacecraft can be steered.

Sinko and Schlecht say that if those space-junk thrusters were scaled down and fitted onto a spacesuit, with tubes to vent propellant away from the astronaut, you would have a way to retrieve a spacewalker who is spinning into the void. You could even apply small thrusters to astronauts' toolboxes - one was lost during a spacewalk in 2008.

Existing rescue systems - spring-loaded or gas-driven tethers that can be fired towards an astronaut - can't reach more than 100 metres. And astronauts venturing outside the International Space Station must wear a jet pack of nitrogen thrusters. But none of these safety measures can help an astronaut who is incapacitated. The laser activated system would work for incapacitated astronauts.

Journal of Propulsion and Power, vol 27 - Reversed-Thrust Laser Propulsion and Astronaut Retrieval




Sinko and Schlecht's calculations suggest their technique will work. By pulsing a carbon-dioxide laser on a 1-kilogram thruster for 200 seconds, they reckon they can move an astronaut back towards safety at 1 metre per second

A space-based laser ablation propulsion system has the potential to produce a paradigm shift in the management of space resources. This paper outlines practical considerations for in-space use of a laser ablation propulsion system for generating an attractive force between two space objects. Limitations of energy delivery to the target are determined, and mass removal and impulse generation are calculated as functions of range for a variety of laser wavelengths. A unique in-space application is proposed for a reversed-thrust system: emergency retrieval of astronauts and tools on-orbit.

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