Chinese Subs May Be Propelled Silently By Lasers

If sharks with lasers on their heads weren’t bad enough, now China is working on submarines with lasers on their butts. At least, that’s what this report in the South China Morning Post claims, anyway.

According to the report, two-megawatt lasers are directed through fiber-optic cables on the surface of the submarine, vaporizing seawater and creating super-cavitation bubbles, which reduce drag on the submarine. The report describes it as an “underwater fiber laser-induced plasma detonation wave propulsion” system and claims that the system could generate up to 70,000 newtons of thrust, more than one of the turbofan engines on a 747.

The report (this proxy can get around the paywall) claims that the key to the system are the tiny metal spheres that direct the force of the cavitation implosion to propel the submarine. Similar to a magnetohydrodynamic drive (MHD), there’s no moving parts to make noise. Such a technology has the potential to make China’s submarines far harder to detect.

Looking for more details, we traced the report back to the original paper written by several people at Harbin Engineering University, entitled “Study on nanosecond pulse laser propulsion microspheres based on a tapered optical fiber in water environment“, but it’s still a pre-print. If you can get access to the full paper, feel free to chime in — we’d love to know if this seems like a real prospect or just exaggerated reporting by the local propaganda media.

[Image via Wikimedia Commons]

62 thoughts on “Chinese Subs May Be Propelled Silently By Lasers

    1. I would have thought that cavitation produces more noise too? The pistol shrimp, which uses cavitation to catch prey, generates a loud cracking noise of up to 210 dB at the source.

      1. Cavitation propulsion is very noisy but that is actually good.
        Think spark-gap radio transmitter – so loud and broadband nobody else can hear anything. Same with cavitation propulsion – so loud nobody else can hear anything.

      2. Yeah, the idea that this runs silently at that power output by blasting enough laser energy into the water to open up a cavity under extreme pressures… Is ludicrous. Kind of sad to see people so credulous

        1. I would wonder if the point is not silent running, but fast running with no openings for drive screws. This could (possibly) allow the creation of a submarine that can dive deep and travel fast, but at the tradeoff of being easily detectable.

          There might be a market for this technology for non-military deep-sea submarines for various industrial and survey uses.

          1. OOOH, I think you’re definitely on to something: everyone is going nuts about hypersonics and how to defend against them. This “super-cavitation”, if it does result in VERY high speeds underwater, is the marine equivalent of hypersonics.

            It’s not about the noise but in being able to strike (or out-run) faster than the enemy (US) can react! This is huge if true BUT China is well known for their exaggeration on this front.

      1. Akchewally, it’s the same thing.

        Low pressure bubble in water. Bubble collapses, collapse makes noise.

        Supercavitation is making the bubble ‘super’ and sustaining. Still makes noise – a lot of noise’ as the edges collapse.

        1. Is the concept not that the edges don’t collapse, so there is a permanent bubble around the hull? Otherwise you’d need a shit ton of sacrificial air as well, right?

          1. The back collapses and the front is refilled.

            Yes, you need a gas generator to keep replenishing the bubble.

            In this laser thingamajiggy the laser generates more gas by vaporizing more sea water.

  1. Put me down as doubtful.

    Most submarines design is about reducing cavitation at the propellers since that is a major cause of noise, so we are going to design a propulsion system based on cavitation?

    Doesn’t really sound credible,

    1. And, yes, I know about this, but unlike the Chinese information it wasn’t DIRECTLY associated with a military use, so the Soviets let it be published in the open literature:

      August 25, 2020

      A 1962 paper translated as Method of Edge Waves in the Physical Theory of Diffraction was of particular interest. Many U.S. scientists simply saw the paper and incorporated it into their own research, or they rebuffed it and went about their day. But there was one team of engineers who saw the paper and saw it as potentially groundbreaking.

    2. i can’t make heads or tails of this tech but china’s military isn’t really in the business of winning through main force (or hasn’t been so far). advertising a capability or interest may be useful for attaining their actual goals (deterrent / stabilizing or destabilizing influence, depending). with war looking more likely every day, the ability to obviate the war — to make it so obvious who would win that they don’t bother fighting — could prove much more valuable than direct material force or surprise.

    1. The problem with supercavitation is that the torpedos can’t track and can’t steer. Not unlike a hypersonic missile.
      The G.D. Ruskies are _real_ proud of them, but ‘Rusky navy’. Grain of salt the size of Russian national yearly vodka consumption.
      Propaganda intended for domestic Russian consumption.
      Sort of like this story, except this is for mainland Chinese patriots. Help them get over not invading Taiwan.

      A super loud submarine blindly going fast isn’t really useful. It’s called the silent service for a reason. First one with a target, wins.
      Unless the sub can outrun anti-submarie warfare aircraft, it would boggie right into a couple of homing torpedos, dropped in it’s path. Would never hear them, until the very loud noise ruins their day.

        1. Maybe not all hypersonic missiles are steerable. Seems like the Russian hypersonic missiles deployed so far do not seem very agile resulting in the Patriot shootdowns in the Ukraine. Supercavitation for submarine propulsion might be good for weapons but probably not the sub itself. I see problems with heating and durability of the hull in that environment. Not to mention noise and a huge gas release that would seem to be detectable.

  2. “70,000 newtons of thrust, more than one of the turbofan engines on a 747.” is incorrect.
    Those jet engines produce about 4 times that thrust. Misreading the SCMP, or confusing the silly lbf unit with N?

    And much of the rest of that doesn’t sniff right either. Something is lost in translation, or the Harbin University propagandists are taking lessons from MIT on writing release copy.

  3. Actually, Chinese are far more ahead in fluid dynamics research compared to US, UK and highly developed parts of EU (France, Germany, Italy). Recently I’ve bought hypersonic cavitation electronic toilet cleaning brush and it does wonders compared to Domestos. I’ve been trying to get rid of yellowing and frozen brown jelly for years and it did the job in one go.

    1. Did you at least try a conventional bidet toilet seat first?
      I know you’re Chinese and these were invented by the Japanese, put your prejudice away for a second.

      ‘Hypersonic cavitation’ sounds uncomfortable.

      I will admit, ‘frozen brown jelly’ sounds concerning.
      See your doctor. The good kind, not the quacks dispensing ‘traditional Chinese medicine’.

  4. so, superheating water won’t make any noise? If anything it would make it more detectable. And constant pulsing of 2 Megawatt lasers through fiber optics? This thing would be in the shop more than on the open sea.

    China taking a play from the Russian handbook “make enemy think you have very useful weapon system with breakthrough technology”. Physics wins in the end. Any system like this will make noise, be difficult to maintain, and with that kind of power requirement will make reactor noise something detectable.

      1. How was it a fiasco though? Even after one MiG-25P was ‘acquired’ for inspection, it was concluded the Soviets still made a capable interceptor despite the crude nature of it’s construction. In any case, the MiG-25PD/PDS and Su-27 that came after it were even more formidable and the F-15 was well placed to deal with the new threats.

        1. Simple, to counter the MIG25 which was super fast in a straight line and handled like a brick, the US developed the F15 platform which is very agile and powerful and could will the interceptor role as well as the air superiority role. Improved interceptor capabilities were overcome with stealth technology. The SU27 was much later and a response to the F15/F16 and it’s debatable how effective a response it was. We will see shortly when the Ukraine puts F16s and NATO air defense systems together for the first time against Russian technology in Russian hands. Submarine survivability today is all about detection, your submarine is not going to outrun strategic bombers or long range anti submarine missiles. If you are found, you will be killed. In all out super power conflicts, I would expect at sea use of tactical nukes so I dont care how fast your sub is. Also, if they have mastered megawatt fiber lasers underwater I would be very surprised, especially if it lasts more than a month.

          1. You haven’t changed my opinion. Fast interceptors are still a dangerous military threat, good old ‘boom and zoom’ tactics and all that. Anyway, the MiG-25 served (if anything else) as the impetus for America to counter it with an outstanding combat aircraft – one that is still being built in an evolved form over 50 years later.

  5. Sometimes publishing is done defensively. This is to publicise details so that other adversaries know that you have the capability, but not what and how many systems are using it.

    I’m very curious how this is quiet, as a pulsed laser would likely create a very specific and easily identifiable frequency in the water it’s cavitating.

    1. If you read the source material, you see they don’t have the capability, aren’t even within a generation of the capability, and the research paper itself doesn’t even go to submarine propulsion.

      And there’s a focus on sub propulsion when this would be just as viable for ships too.

      1. You would have to explain for a surface ship how it would be better than a conventional turbine system. Doubt it would be more reliable. Noise matters much less for surface combatants. Also necessitates a nuclear power plant with high output limiting it to the biggest classes like carriers, cruisers, and subs. China is having a hard enough time fielding a reliable deep water Navy to match their adversaries, chasing stuff like this will not help. I think most Naval power is soon going to be very vulnerable to UAV and missile systems of the future. These days your antimissile defenses cannot afford to miss once or it is a platform kill of a multibillion dollar ship. I think the US is likely to move toward unmanned possibly AI controlled global reach systems (hypersonic delivery of UAV swarms) that is going to brutalize naval systems.

  6. That paper discusses manipulating 20-50 micrometer polystyrene microspheres using 8-50 microjoule nanosecond-long laser pulses.

    From the paper:

    “The system can effectively control the generation of laser energy and spot, so as to achieve accurate microsphere propulsion.”

    “… the study of PS microsphere propulsion using a conical fiber laser propulsion system has potential application prospects in underwater laser cleaning and underwater microstructure manipulation.”

    Concluding with: “We believe that the findings of this study can provide experimental and theoretical foundations for underwater laser propulsion research.”

    It’s a long, long stretch to moving submarines.

    Yep, straight from the typical university propaganda playbook.

  7. Cavitation = Noise. A submarine tries to reduce cavitation as much as possible. There will always be come cavitation be we never want a lot of it. This is why we don’t use a flank bell everywhere we go.

  8. China. Maybe I’m to old to see the pattern every time a new report from China comes to the other side:
    a) The report contains the word “propaganda”… b) China do/has/made/got something …c) commenters: nah! no, noway. d) Also commenters : propaganda! Happily this is not the case :)

  9. Lasers from the butt? I suppose at a time when mainstream “news” organizations are trying to out-do each other with Pecker headlines, this is inevitable. However, in the Navy a “butt” is a large cask of fresh water for drinking. As in the chatter around the scuttlebutt.

  10. 1. Article starts out talking about propulsion – but it’s super cavitation. Which is a drag reduction method, not propulsion.

    2. Enjoy your 50kt sub that can be heard from 500 mile away. You won’t even hear the torpedo that kills you.

    1. Also ‘no moving parts’ doesn’t mean ‘silent’.

      This thing is supposed to be a steam rocket – that’s not going to be quiet underwater.

      *And* you still run into the same problem normal sub have – to run the propulsion on high you need your powerplant on high. And your power plant has moving parts.

      For example, a nuke can run low and slow without using it’s circulation pumps (natural convection) but as soon as you kick it in the arse those pumps come on and it’s loud.

      1. You could do like the plutonium breeders at Hanford did, and once you get it going and you’re running into cooling problems, just run the outside water (in their case the Columbia, in this case the external seawater) as your coolant and you don’t need pumps.
        (the radioactive plume from this was detectable 100 miles off the coast.)

        1. Subs do use outside cooling water in the secondary loop – it’s seawater.

          But you need to move water around inside the reactor and that takes pumps. If you try to just flush seawater through either you still need to pump it or try to ramscoop – and you be flushing highly radioactive water out the back and destroy your reactor and turbines – seawater steam would be I credibly corrosive.

          Standford still uses a closed primary loop – the river is the open secondary. And both loops still need pumps at high powers.

  11. I have to concur with prior comments. That’d be a fast sub with a lot of thrust, but not remotely stealthy. It would just be a matter of technicians (or their computers) learning to recognize another loud sound that doesn’t resemble anything natural. And, yes, cavitation like turbulence is traditionally bad but can be controlled to reduce drag. There’s a lot of studies on crocodilian and cetacean hydrodynamics and golf ball and windmill aerodynamics to back that up.

  12. Might not work but still though.. having those LASER you can always use them to shoot holes in missiles and ships!, LASERS are always handy.

    Incidentally, AFAIK high power military LASERS have a limited number of times they can fire before the tube has to be replaced. Bit like barrels on guns. Now sure it might be a few hundred times, but when you would try to use them as propulsion then how far would you get? So this might be one of those ‘if only we had/could..’

  13. interesting. in my opinion large vessels already have a similar concept to reduce drag with cavitation. basically under the hull air is pumped out under the vessel to reduce drag. I presume the air bubbles create a specific noise decibel that can be detected with sophisticated instruments.

  14. Given the number of times HaD has been had by stories in the South China Morning Post that involve extraordinary claims, often involving topics of considerable military advantage that a reasonable nation would like to keep secret, it would be a good policy to never use it as a primary source.

  15. New site name: Chinesepropogandaaday

    Seriously, what has happened to this site? Are there no new electronics projects being built anywhere so you have to stoop to posting nonsense like this?

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