Submarines haunt the dreams of sailors around the world.
Secretive, stealthy, and able to strike from out of nowhere, they remain the greatest threat
to surface ships.
Thankfully, submarines are limited in just how fast they can move, typically with a top
speed of 29 mph (46 kmh), which is well short of a typical destroyer's top speed of 40 mph
(64 kmh).
Lagging behind their potential prey, submarines must typically intercept their targets or
lurk in sea lanes and wait for an enemy to stumble into them.
But what if subs could move much, much faster than they currently do?
Hello and welcome to another episode of The Infographics Show- today we're taking a look
at supersonic submarines- the US Navy's new Superweapon.
Moving underwater can be more difficult and energy intensive than cruising along the surface,
thanks to the huge amount of drag that water exerts on a vessel and denser water a submarine
encounters the deeper it dives.
Thus while speedboats can zip along the surface of the ocean at speeds of up to 90 mph (150
kmh), anything traveling beneath the waves must exert exponentially larger amounts of
energy to move as fast- something traditional submarines are incapable of doing.
Yet in June of this year it was revealed that Chinese hackers had stolen sensitive data
from a US contractor that had been working on a top secret program to develop a supersonic
missile to be launched from a submarine.
While the data was only sensitive in nature and not classified, it did hint at a major
avenue of research the US was undertaking, and hinted that the US Navy was not just interested
in supersonic missiles, but supersonic submarines as well.
For US/China observers though, the revelation was no surprise, as in 2014 China had made
claims of huge technological breakthroughs in developing their own supersonic submarines.
But just how can you move a submarine through the water at supersonic speeds without huge
amounts of energy or absolutely destroying the ship in the first place?
Let's take a look at both the US and China's approaches to the problem.
The US proposal involves using something called supercavitation- a technology that the Soviet
Union developed in the 1960s for super-fast torpedoes.
The Soviet approach to moving a torpedo at hundreds of kilometers an hour was to add
a special segment to the nose cone of a torpedo filled with pressurized gas, that gas in turn
is ejected at extremely high pressures and creates a bubble around the torpedo.
A rocket motor, rather than a traditional propeller, then pushes the torpedo along,
and since it's avoiding drag from water the torpedo could reach incredible speeds.
The design was a success, but because of the need to maintain a gas bubble, the range of
the torpedo was only a few miles.
By scaling the technique up dramatically, the US hopes to be able to cocoon an entire
submarine in a gas bubble, and then use powerful rocket motors to blast across the ocean at
speeds faster than sound.
The physics involved show that the concept could work, and already does at smaller, torpedo
scales, yet so far the US has been unable to overcome several obstacles.
One of those being the difficulty in maintaining the integrity of a large enough bubble around
the submarine, and keeping it from 'pulsating' dangerously.
During current, smaller scale tests, the bubble tended to expand and contract to such extremes
that parts of the submarine model made frequent contact with water.
At extreme speeds that would be disastrous and could rip a submarine apart, or at the
very least create so much friction that the submarine would go wildly off course.
To overcome the problem scientists are experimenting with moderating the rate of gas release at
the tip of the submarine.
China's approach to the problem uses traditional supercavitation techniques with a new technique
that involves spraying a special liquid membrane onto the vessel's hull to reduce its friction
with water.
The vessel would gradually speed up with this membrane being constantly sprayed on as it
was worn away.
Once hitting about 62 mph (100 kmh), an air bubble could be formed and maintained.
China's solution would entail the use of a synthetic lubricant of sorts to help a vessel
'slip' through the water.
It also provides a possible fix to one of the biggest practical challenges facing supercavitating
vessels: how do you steer it?
Moving at such incredible speeds, if you were to extend a fin or control surface into the
water it would be immediately snapped off, and the force exerted might throw your submarine
into a spin which would lead to disaster.
Yet by moderating the flow of their liquid membrane the Chinese could ensure that one
side of the submarine's bubble experiences slightly more drag than the other, which would
allow a sub to turn, dive, or rise as it sped along at the speed of sound.
If it truly works, it would be an elegant solution to one of the biggest practical hurdles
facing this entire concept.
Yet a supersonic submarine would not make for a very good offensive weapon, as submarines
are in fact extremely vulnerable assets who's best defense is stealth.
A submarine crossing the ocean at supersonic speeds may be able to get from San Francisco
to Shanghai in 100 minutes, but it will generate so much noise that even a deaf sailor would
hear it.
That would make a supersonic sub extremely easy prey for surface anti-submarine ships,
or other hostile attack subs.
That's why the technology will likely not be used for offensive purposes, but rather
for logistical ones.
Supersonic subs that could cross the Pacific in just over an hour would be idea for quickly
moving personnel and resources to conflict areas, and would be incredibly appealing for
the US which faces the prospect of coming to the aid of its NATO allies in Europe in
case of war against Russia.
For decades Russia has counted on the fact that in the case of war, it might be able
to force a cease fire favorable to its interests by quickly overwhelming European defenders
and then digging in before the bulk of US forces could arrive weeks later from America.
Faced with the prospect of a difficult war against an entrenched enemy, and the massive
civilian casualties it would cause, NATO might be more inclined to simply acquiesce to part
of Russia's demands rather than wage a very costly war.
Yet a supersonic underwater transport vehicle could change all of that by giving the US
the ability to move large amounts of personnel and equipment across the Atlantic in a matter
of hours.
That would make a US buildup possible in days, rather than the weeks it would currently take
to ship American attack helicopters and armor across the ocean.
Such a fast transport system would also give US leaders a capability they have dreamt of
for decades- the ability to put boots on the ground nearly anywhere in the world within
hours.
As one US military officer once noted, the ability to place a company of US Infantry
anywhere in the world within a few hours would stop a lot of wars before they started.
Supersonic submarines could be revolutionary tools for any nation's navy, yet the technical
challenges are formidable and its unlikely that they will be overcome anytime soon.
Some worry that the pilfering of US secrets by China may erode the US's military edge
over its potential adversary, but the continued theft of low-level secrets by Chinese hackers
merely points at a culture that is more adept at trying to steal revolutionary new technologies
than to invent its own- something which should be of serious concern for Chinese military
planners.
Would you ever take a ride on a supersonic sub?
What other military uses might a supersonic submarine have?
Let us know in the comments!
Also, be sure to check out our other video How Deep Can Submarines Go?
Thanks for watching, and as always, don’t forget to like, share and subscribe.
See you next time.