Can a Supersonic Submarine Be Powered by Lasers?

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Researchers at China’s Harbin University recently claimed they managed to achieve silent propulsion using laser power, which would enable silent supersonic submarines in the future. However, professor of mechanical engineering at McGill University Andrew Higgins, who also uses lasers for propulsion in space, explains that the technology probably couldn’t propel a submarine, as reported by Business Insider.

Many nations worldwide have been working on developing submarine technology that will make the already stealthy underwater vehicle even more silent to avoid detection, with efforts including the reduction of noise emanating from mechanical components like propellers and generators. The Harbin University researchers tried taking this approach to the next level by switching to lasers for propulsion – they published a paper claiming that this technology could one day allow Chinese submarines to travel at supersonic speeds and give them a major advantage against adversaries.

The Chinese researchers reportedly advanced two-decade-old technology first developed by the Japanese, which uses lasers to make plasma and then to make a detonation wave inside the water. They also claim that a two-megawatt laser, which can be powered easily on a regular submarine, could generate 70,000 newtons of thrust (equivalent to a commercial jet engine).

The researchers concluded their article by expressing their intention to deliver supercavitation (a coating of bubbles around an object) to help reduce drag and make objects travel faster in water.

As attractive as these claims seem, Higgins explains that supercavitation using lasers is not even possible for missiles, with submarines even further from using such technology. He also expressed his skepticism that the output claimed for the propellor is way larger than the energy put into the laser that powers it – “Even with the high efficiencies of today’s lasers, this approach would never be as efficient as a propeller, so there is no net propulsive gain.”

He concluded by stating that supercavitation is an acoustic giveaway and will nullify the submarine’s stealth ability.