Researchers in China are reporting that they’ve taken a big step
towards creating a supersonic submarine. This technology, which
could just as easily be applied to weaponized torpedoes as military
or civilian submarines, could theoretically get from Shanghai to San
Francisco — about 6,000 miles — in just 100 minutes. If all this
doesn’t sound crazy enough, get this: This new advance by the
Chinese is based on supercavitation , which was originally developed
by the Soviets in the ’60s, during the Cold War.
As you may already know, it’s a lot harder for an object to move
quickly through water than air. This is mostly due to increased drag.
Without getting into the complexities of fluid dynamics, water is
simply much thicker and more viscous than air — and as a result it
requires a lot more energy for an object to push through it. You can
experience the increased drag of water yourself next time you’re in a
swimming pool: Raise your hand above your head, and then let it
fall towards the water. (Or alternatively, if there are people
sunbathing nearby, do a belly flop.)
Anyway, much like a small-engined car is ultimately limited by its
ability to cut through wind resistance (drag), a submarine or
torpedo needs insane amounts of power to achieve high velocity
through water. This is why, even in 2014, most submarines and
torpedoes can’t go much faster than 40 knots (~46 mph). Higher
speeds are possible, but it requires so much power that it’s not
really feasible (torpedoes only have so much fuel).
How a normal torpedo works, vs. a supercavitation torpedo
Enter supercavitation, a technique devised by the Soviets in 1960
with the explicit purpose of creating high-speed torpedoes.
Supercavitation gets around the drag of water by creating a bubble
of gas for the object to travel through. The USSR’s research
resulted in the Shkval torpedo, which uses a special nose cone to
create the supercavitation envelope, allowing it to travel through the
water at speeds of up to 200 knots (~230 mph, 370 kph) — much,
much faster than the standard torpedoes fielded by the US.
The only other countries with supercavitational weapons are Iran
(which probably reverse-engineered a Russian Shkval), and
Germany with its fantastically named Superkavitierender
Unterwasserlaufkörper (“supercavitating underwater running body”).
The US is researching its own supercavitational torpedo, but there’s
very little public information available.
Which brings us neatly onto China. Unlike previous approaches,
which have to be launched at high speed (~60 mph) to create the
initial supercavitation bubble, the method described by the Harbin
Institute of Technology in China uses a “special liquid membrane”
that reduces friction at low speeds. This liquid is constantly
showered over the object to replenish the membrane as it’s worn
off by the water. Once the torpedo/submarine/vessel gets up to
speed, it sounds like it uses the same gas-through-nose-cone
technique to achieve supercavitation. (Details are a bit vague at this
point.)
Read our featured story: The science of beam weapons
In theory, supercavitation could allow for speeds up to the speed of
sound — which, underwater, is a heady 1,482 meters per second, or
3,320 mph. At that speed, you could go from Shanghai to San
Francisco (about 6,000 miles) in well under two hours. Suffice it to
say that there isn’t a country in the world that wouldn’t love to have
a submarine that can circumnavigate the world in half a day —
especially a country with nuclear missiles, like China, Russia,
France, the UK, or the US.
The nose cone of a Russian Shkval (Squall) torpedo. Note the vents
for escaping gases, which combined with the flat nose create a
supercavitation bubble.
In practice, though, it’s a) very difficult to steer a supercavitating
vessel (conventional methods, such as a rudder, won’t work without
water contact) — and b) developing an underwater engine that’s
capable of high velocity over long distances is very, very difficult.
You can’t use a jet engine underwater, sadly — and generally,
rockets only have enough fuel for a few minutes, not hours. Nuclear
power might be a possibility as far as supersonic submarines go,
but that’s just a guess.
towards creating a supersonic submarine. This technology, which
could just as easily be applied to weaponized torpedoes as military
or civilian submarines, could theoretically get from Shanghai to San
Francisco — about 6,000 miles — in just 100 minutes. If all this
doesn’t sound crazy enough, get this: This new advance by the
Chinese is based on supercavitation , which was originally developed
by the Soviets in the ’60s, during the Cold War.
As you may already know, it’s a lot harder for an object to move
quickly through water than air. This is mostly due to increased drag.
Without getting into the complexities of fluid dynamics, water is
simply much thicker and more viscous than air — and as a result it
requires a lot more energy for an object to push through it. You can
experience the increased drag of water yourself next time you’re in a
swimming pool: Raise your hand above your head, and then let it
fall towards the water. (Or alternatively, if there are people
sunbathing nearby, do a belly flop.)
Anyway, much like a small-engined car is ultimately limited by its
ability to cut through wind resistance (drag), a submarine or
torpedo needs insane amounts of power to achieve high velocity
through water. This is why, even in 2014, most submarines and
torpedoes can’t go much faster than 40 knots (~46 mph). Higher
speeds are possible, but it requires so much power that it’s not
really feasible (torpedoes only have so much fuel).
How a normal torpedo works, vs. a supercavitation torpedo
Enter supercavitation, a technique devised by the Soviets in 1960
with the explicit purpose of creating high-speed torpedoes.
Supercavitation gets around the drag of water by creating a bubble
of gas for the object to travel through. The USSR’s research
resulted in the Shkval torpedo, which uses a special nose cone to
create the supercavitation envelope, allowing it to travel through the
water at speeds of up to 200 knots (~230 mph, 370 kph) — much,
much faster than the standard torpedoes fielded by the US.
The only other countries with supercavitational weapons are Iran
(which probably reverse-engineered a Russian Shkval), and
Germany with its fantastically named Superkavitierender
Unterwasserlaufkörper (“supercavitating underwater running body”).
The US is researching its own supercavitational torpedo, but there’s
very little public information available.
Which brings us neatly onto China. Unlike previous approaches,
which have to be launched at high speed (~60 mph) to create the
initial supercavitation bubble, the method described by the Harbin
Institute of Technology in China uses a “special liquid membrane”
that reduces friction at low speeds. This liquid is constantly
showered over the object to replenish the membrane as it’s worn
off by the water. Once the torpedo/submarine/vessel gets up to
speed, it sounds like it uses the same gas-through-nose-cone
technique to achieve supercavitation. (Details are a bit vague at this
point.)
Read our featured story: The science of beam weapons
In theory, supercavitation could allow for speeds up to the speed of
sound — which, underwater, is a heady 1,482 meters per second, or
3,320 mph. At that speed, you could go from Shanghai to San
Francisco (about 6,000 miles) in well under two hours. Suffice it to
say that there isn’t a country in the world that wouldn’t love to have
a submarine that can circumnavigate the world in half a day —
especially a country with nuclear missiles, like China, Russia,
France, the UK, or the US.
The nose cone of a Russian Shkval (Squall) torpedo. Note the vents
for escaping gases, which combined with the flat nose create a
supercavitation bubble.
In practice, though, it’s a) very difficult to steer a supercavitating
vessel (conventional methods, such as a rudder, won’t work without
water contact) — and b) developing an underwater engine that’s
capable of high velocity over long distances is very, very difficult.
You can’t use a jet engine underwater, sadly — and generally,
rockets only have enough fuel for a few minutes, not hours. Nuclear
power might be a possibility as far as supersonic submarines go,
but that’s just a guess.
Li Fengchen, a professor at the Harbin Institute, says their
technology isn’t limited to military use. Yes, supersonic submarines
and torpedoes are top of the list — but the same tech could also
boost civilian transport, or even boost the speed of swimmers. “If a
swimsuit can create and hold many tiny bubbles in water, it can
significantly reduce the water drag; swimming in water could be as
effortless as flying in the sky,” says Li.
As always with such advanced (and potentially weaponized)
technology, it’s hard to say how far away it is from real-world use.
If civilian researchers are making good progress, then it’s a fairly
safe bet that the military is even further along. Wang Guoyu, another
Chinese researcher, told the South China Morning Post: “The
primary drive [for supercavitation] still comes from the military, so
most research projects are shrouded in secrecy.”
technology isn’t limited to military use. Yes, supersonic submarines
and torpedoes are top of the list — but the same tech could also
boost civilian transport, or even boost the speed of swimmers. “If a
swimsuit can create and hold many tiny bubbles in water, it can
significantly reduce the water drag; swimming in water could be as
effortless as flying in the sky,” says Li.
As always with such advanced (and potentially weaponized)
technology, it’s hard to say how far away it is from real-world use.
If civilian researchers are making good progress, then it’s a fairly
safe bet that the military is even further along. Wang Guoyu, another
Chinese researcher, told the South China Morning Post: “The
primary drive [for supercavitation] still comes from the military, so
most research projects are shrouded in secrecy.”
-Extreme Tech
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