Plasma-spaffing boffins plan spaceships driven by FRIKKIN' LASERS

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Laser ablation to speed rockets

Russian boffins reckon with the right configuration, lasers can help make rockets more efficient, and could even herald an era of Mach 10 aircraft.

Laser-driven propulsion isn't just the domain of the sci-fi fan. The aim of any rocket propulsion system is to take some kind of mass, and heat it up to generate thrust. The amount of thrust you get is pure Newtownian physics: the thrust is proportional to the amount of mass you eject and the velocity at which it's ejected.

That has a built-in inefficiency, since a spacecraft's top speed is limited by the amount of fuel it can carry, and chemical burns have an upper limit to the heat (and therefore the velocity of the jet).

Laser ablation, in which a laser heats a surface to generate a plume of very high-temperature plasma, has long been researched, but is problematic, according to a paper published over at Applied Optics.

As the Optical Society notes: “the effectiveness of current laser-propulsion techniques is limited by factors including the instability of supersonic gases as they flow through the gas nozzle, as well as the production of shock waves that 'choke' the inlet of the nozzle, reducing thrust”.

What's needed, in other words, is a smoother, more manageable, and less chaotic plume.

Laser ablation to speed rockets

Yuri Rezunkov's model of laser ablation in a rocket

So the Russian researchers (Yuri Rezunkov of the Institute of Optoelectronic Instrument Engineering, and Alexander Schmidt of the Ioffe Physical Technical Institute in Saint Petersburg) propose managing the laser ablation plume so it hugs the interior walls of the rocket nozzle.

This, they claim, can then be coupled with the supersonic gases that flow in a conventional rocket, to get a significant improvement in overall thrust.

The most immediate outcome, if the scheme works and can be engineered into real-life rockets, would be to make conventional launches more efficient. The researchers also reckon their system could be used for supersonic aircraft. ®

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