Supersonic – underwater?

| February 20, 2024


No, we are not referring to the finances of the SST – multiple news reports say the U.S. Navy is doing research on a super-sonic submarine.

The sleek jet is expected to play an instrumental role in bringing back supersonic commercial air travel. But what if I tell you that researchers are working on a submarine that could travel more than three times faster than the X-59 jet?

But there’s a simple solution to overcome drag underwater – a bubble. The researchers are working on a technology called supercavitation that envelopes a submerged vessel inside an air bubble to mitigate drag. You’ll be surprised that the technology is not new. The Soviets developed it during the Cold War era for a torpedo named Shakval. The Soviet torpedo reached a speed of 370km/h (around 230mph), making it a lot faster than any other conventional torpedo.

In theory, the technology can help the submarine hit supersonic speed underwater, or about 5,800km/h (~3600mph). If developed, the supersonic submarine would cut down the journey time from New York to London to just 50 minutes. Furthermore, the 5300-mile distance between San Francisco and Tokyo will be covered in 90 minutes by the radical submarine. Luxury

Sounds incredible. I would point out that ‘supersonic’ is a slippery term, as sound travels ‘WAY faster in salt water than in air, and the speed  is far more variable.

In the oceans the speed of sound varies between 1,450 and 1,570 metres (about 4,760 to 5,150 feet) per second. It increases about 4.5 metres (about 15 feet) per second per each 1 °C increase in temperature and 1.3 metres (about 4 feet) per second per each 1 psu increase in salinity.

So, depending on depth, temperature etc. that 3600mph may or may not be supersonic in water. Either way, it’s interesting to think a sub could go faster than a plane.

Now, so far, this is somewhat theoretical – the pic below is of a “second order supercavity” in a 12″ wide tank. Note the best the Russian torpedo hit was about 10% of the speed of sound, equivalent to about 100mph in the air.

Both China and the US are working on this, and no doubt the Russians have continued their work.  One suspects the actual usage of such a drive would be very noisy and I am sure a whale strike would be catastrophic. I am willing to stick my neck out and say we will see this appear first in faster torpedoes, not submarines. Maybe some of you folks with more knowledge that I – almost everyone – can shed more light on it?




Category: Navy, Science and Technology

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If it comes to pass, won’t somebody have to learn to drive the sub all over again? Or will they have to slow down for maneuvers. The crashes will be spectacular and expensive.


My first thought was what a crash into a lost shipping container would look like at mach 3. My second thought was how stupid expensive this whole thing would be. Hard pass.


A crash into a school of jellyfish is gonna be a disaster.

Green Thumb

Or anything else with mass.

And I will not even step into the argument of negative environmental impact.


Jellyfish were the squishiest thing I could think of. It’d sure be fun to watch!


They would be in quite a jam.

Skivvy Stacker

Your parents are very disappointed in you…

Slow Joe

But, is maximum speed the only choice?
Can a slower speed by achieved without compromising the bubble? The Shkval torpedo does.


I would imagine the speed would still be pretty high to maintain said bubble even if they slowed down.


With diversity hiring and affirmation action promotions, I don’t think American companies will figure this out.


Don’t worry, a brilliant young Ethiopian/Asian/Inuit/Rhodesian/Siberian-American transwoman lesbian will be at the forefront of this.


Well, the traditional diversity hires will be pissed.


There are a lot bigger things in the Sea/Ocean than in the air, most of which don’t go above a certain altitude. The reverse is true in the water the deeper you go the bigger the mess will be!

Skivvy Stacker

I guess the only solution would be to operate these submarines ABOVE the ocean.

Wait a second….

Veritas Omnia Vincit

The issues that might prove insurmountable in the near term are the control surfaces, anything that would provide control has to actually pierce the bubble creating more than a little drag and at those speeds the forces exerted on anything that needed to be outside the bubble would be tremendous.

The other issue is a power source large enough to provide meaningful range, torpedoes are one thing large thousands of tons submarines are rather something else.

About ten years ago the Cavitation and Bubbly Flows Research Group at University of Michigan suggested a minimum propulsion of around 45-50 mph was required just to get the bubble started…

Interesting research no doubt…I suspect I’ll be long dead before it comes to fruition. Which doesn’t mean we shouldn’t continue to research it, it just means it will be a while before you’ll be able to get a ticket to London on one….


Anyone remember the Concorde, or the American SST program? Just like this project, off-the-chart cool factor but seriously impractical.


I’ve only three real travel regrets: I never visited NYC before the towers fell, I joined the army instead of the navy (I still got to travel, but the destinations seemed a lot less fun), and I never flew on the Concorde.


First one built will go to the ‘kraines to patrol the Black Sea.


Has anyone asked the whales if we can make some noise?

VOV nailed it, drag from control surfaces and power requirements are off the chart.

President Elect Toxic Deplorable Racist SAH Neande

So….water-to-solid surfaces interaction is a drag (pun intended).
So……air-to-solid interaction is less of a drag.
Build an air bubble around the sub.
BUT!….how are you going to keep the sub in the air bubble? Drag the air bubble along with you? Wouldn’t there be an air (bubble)-to-water interaction that would create its own drag? Thus slowing down this whole “good fairy” ideal theory?
Are you going to create a continuous air bubble in front of/around the sub? Which would create its own set of mechanical problems.
Sounds too complicated and messy to me.


Does the Navy have to give 10% off the top of the budget to the Big Guy?


The first sub will be named the Sonic.
Sub Sonic.


Supersonic is a good idea for planes, because whales don’t fly. Submarines? I’ll pass.

Slow Joe

I don’t know. I have seen a couple of whales flying commercial in the Miami to Denver route.


Did they get smaller in the thinner air?


Did they need those seat belt extensions?


Don’t geese bring down airliners?


Whales get a free seat on Southwest Airlines…


Its called supercavitation and Russia has done it, sort of. The VA-111 Shkval (Squall) torpedo could reportedly reach speeds of 230 MHP.

Impressive, but they just couldn’t guide the things.


Maneuver could use thrusters instead of control surfaces.

The propulsion might be two-axis moveable like some modern fighters.

The bubble generator surface/implement could have a variable geometry to produce maneuver through asymmetry. (Vary the drag on opposite sides)

But I would expect sonar isn’t going to work for beans for guidance. Even if remotely wire guided, the thing is going to mask anything quiet.

MAD guidance?


How much water is displaced at that speed? Gotta make a hell of a ripple.


What happens when a supersonic sub hits a “previously unmapped” underwater mountain?

I love the idea of a supersonic submarine (particularly for its R&D potential in other areas) and genuinely hope they pull this off… I’m just not sure I trust the people in charge to do it right. One single mistake – a huge possibility in a realm we seem to understand even less than outer space – and the risk-averse morons will see this whole thing go the way of the Comanche.

Skivvy Stacker

Oh, hell; we’ll have Green Peace bitching about Dolphins going deaf from all the under water sonic booms, and the fish having their floatation bladders all busted up by cavitation bubbles making them gassy.