
'Fluid cloak' to help submarines leave no wake - ColinWright
http://www.newscientist.com/article/mg21128234.700-fluid-cloak-to-help-submarines-leave-no-wake.html
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jedc
I'm a former Navy submarine officer.

While this idea is nice, it's a marginal risk factor. It's difficult to detect
a wake, and you can only detect them when a submarine is near the surface.

What _really_ matters is being quiet. Noise transients can be heard for miles,
and whether a submarine is shallow or deep. And that's why 50+ years of
research has focused on making and keeping submarines quiet.

So while this technology is interesting, it's not very useful for Navy
submarines.

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inportb
Well, the turbulent flow in the wake generates _some_ noise.

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orbitingpluto
If your average sea creature could read, they would be ecstatic about any
development reducing engine/wake noise... it's getting too noisy out there.

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relix
I'm not sure how this would be practical in any way. They're only hiding the
effects of the body moving through fluids, not the effects of what's moving
the body in the first place.

In the case of submarines, the only way to create propulsion is to push water
out the backside. I'm pretty sure this alone would create a visible wake: see
what it looks like by running a boat's engine without it actually moving.

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hugh3
My general feeling is that if this were _really_ practical, there's no way
we'd be hearing about it. The technology, and its author, would be quietly
vanishing into the Naval Research Laboratory.

I wonder what _does_ happen in those situations, actually. If I, as a
university academic, invented something that could make a submarine
undetectable, I'd be willing to consider any cash offers to keep it secret
that the US Navy might be willing to make. But how do I approach 'em?

I've never heard of this kind of thing happening... but then again, I
wouldn't, would I?

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btilly
_My general feeling is that if this were really practical, there's no way we'd
be hearing about it._

It is not practical.

From the article, a sphere 1 cm across could only stay wake and drag free at
speeds of no more than 1 cm/second. If the object is bigger, the limiting
speed goes down even more.

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ch
While I do think these scientists are persuing a worthwhile endeavour, it does
feel like the complexity of this approach is so great that it would never be
useful under normal operational scenarios. Perhaps some HN submariners would
like to comment on the utility of this approach?

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dhughes
Years ago there was a lot of buzz about MHD (Magnetohydrodynamics) but I guess
it's still just science fiction but it sounds like it would help a lot with
reducing turbulence.

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listic
I suspect this is of marginal utility nowadays, because submarines are visible
from the satellites, right?

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pge
Submarines (submerged) are not visible by satellite. Satellites also orbit
(reconaissance satellites would rarely be geosynchronous), so even if they
could see submarines, they would only see them when their courses intersected.

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geuis
I find it remarkable that within a matter of only a few years, such
advancements are being in various fields generally under the umbrella of
"invisibility". Ranging from electromagnetic wave propagation over nano-scale
materials to controlling fluid dynamics to create visual invisibility to sound
cloaks and now something that works similarly in water.

Talk about living in the age of wonders.

