
China's new submarine engine - smacktoward
http://www.popsci.com/china-new-submarine-engine-revolutionize-underwater-warfare
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Animats
That's a nice application for brushless motors with variable-frequency AC
drive. The motor is so simple - it's just windings and the propeller ring. No
seals, no gears, and no bearings that carry heavy loads. All of those things
give trouble underwater. The drive electronics is more complex, but drives for
variable-frequency AC motors are well-debugged now. Every drone has several of
them, and electric cars have big ones.

Some pictures of existing units: [1] They're mostly used as steerable
thrusters for boats that need to be highly maneuverable, such as ferries.
They're becoming very popular for ROVs, because they're much lower maintenance
than existing thrusters used at depth.

[1]
[https://www.youtube.com/watch?v=Te_xejpriFM](https://www.youtube.com/watch?v=Te_xejpriFM)

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JKCalhoun
Guessing E/M noise might be extremely significant though? I suspect there are
other ways, besides microphones, to detect a sub.

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coryrc
Salt water dissipates EM very well.

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bsder
E, yes. M, no.

And this thing seems like it would generate an _enormous_ magnetic field.

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caycep
I don't know how accurate they are, but a lot of the military
analyst/journalist blogosphere (i.e. Tyler Rogoway, War is Boring, etc) have
been pointing out that that US Navy, with its nuclear blinders on, risks
having its sub and carrier fleets badly disrupted by a swarm of newer, cheaper
AIPs. While there are limitations in range and payload etc etc etc, the swedes
were able to inflict disproportionate damage in war-games in their AIP sub.

There are other thoughts on the current administration and their ability to
see their way out of a Thucydides trap with a rising nation who also happens
to be our largest trading partner...and the ability of the Pentagon to
maintain primacy with the destruction of American STEM advantages...

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adventured
The US doesn't need to maintain primacy, it has thousands of nuclear warheads.
It needs to slash ~$250 billion off of its defense budget and invest that into
infrastructure and healthcare over the next ten years instead. The US should
pull back from trying to hold on to its status as the sole military superpower
and focus that tax revenue on its own people. We gain absolutely nothing from
trying to outpace the entire planet in regards to military dominance. Asia can
deal with China (or not), Europe can deal with Russia (or not), the US should
play a secondary role to whatever extent it can afford to (which is to say, it
can't afford to do much and shouldn't be trying to).

None of that is going to happen, of course. The US will ride the military
superpower party to the end of the line, where it's financially forced to cut
back. That won't take more than a decade or two to conclude at this point
(given the soon-to-be routine $1+ trillion deficits due to inbound entitlement
costs). The US will properly cede its European military position to European
nations and it'll cede its Asia military position to Asian nations.

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microcolonel
> The US doesn't need to maintain primacy, it has thousands of nuclear
> warheads.

A military whose first line of defence is nuclear weapons is not a functioning
military. I don't think you want what you say you want. We all wish the
military were cheaper, but that doesn't mean it should be at any cost.

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justicezyx
> A military whose first line of defense is nuclear weapons is not a
> functioning military.

What's the relevance of this statement towards OP? Reducing nuke does not harm
US' strategic supremacy at all. The current arsenal is plainly too much...

It's dead simple to reduce cost and still maintain the same strategic
position.

But you know what, USA won't do it...

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vacri
The GP was saying to reduce conventional forces because of the nukes, not the
other way around.

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mannykannot
I wanted to know more about the rim-driven thruster technology, and a quick
search revealed that it is being deployed in a number of areas where hub-
driven electrical thrusters would otherwise have been used. One manufacturer's
blurb[1] states that they use no seals, so I am curious as to what sort of
bearing is used - could the rotor be magnetically suspended within the stator,
at least while turning?

It also states that their device is symmetrical and so is equally efficient in
either direction. My understanding is that, for optimal efficiency, a ducted
propulsor should be narrower at the exit, but I guess there is no particular
difficulty in making a rim-driven thruster of this form if its primary use is
one-directional.

[1]
[http://www.tsltechnology.com/marine/thrusters.htm](http://www.tsltechnology.com/marine/thrusters.htm)

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phkahler
The comparison to the Red October is unfounded, this totally has a propeller.

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simonh
In the book the drive is not described as propeller-less, only in the movie.

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vilhelm_s
On the other hand, the system described in the book is not shaft-less, so it
_still_ doesn't correspond to this new Chinese technology!

> "They called it a tunnel drive. You know how out West they have lots of
> hydroelectric power plants? Mostly dams. The water spills onto wheels that
> turn generators. Now there's a few new ones that kind of turn that around.
> They tap into underground rivers, and the water turns impellers, and they
> turn the generators instead of a modified mill wheel. An impeller is like a
> propeller, except the water drives it instead of the other way around.
> There's some minor technical differences, too, but nothing major. Okay so
> far? "With this design, you turn that around. You suck water in the bow and
> your impellers eject it out the stern, and that moves the ship." Tyler
> paused, frowning. "As I recall you have to have more than one per tunnel.
> They looked at this back in the early sixties and got to the model stage
> before dropping it. One of the things they discovered is that one impeller
> doesn't work as well as several. Some sort of back pressure thing. It was a
> new principle, something unexpected that cropped up. They ended up using
> four, I think, and it was supposed to look something like the compressor
> sets in a jet engine."

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simonh
The drive in the Red October itself is never described in any detail though.
That description is of a US experimental system that American engineer was
familiar with, not the actual Russian system. Other than the fact it sucks in
water and ejects it out the back, we know nothing else, and that fits the
Chinese system fine. So nitpicking like this is simply not justified.

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SkyMarshal
Fwiw, the rim-driven pump-jet the article is talking about is not the same
thing as the caterpillar drive [1] from Hunt For Red October, to which the
article compares it.

That said, this could be a similarly effective improvement to the submarine's
acoustic signature and stealthiness.

[1]:[https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive](https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive)

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phkahler
The problem with MHD is that it's inefficient and gets even less so when used
to pump sea water. It would be less impractical if there were a lot more salt
in the ocean.

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teapot01
Working link here: [http://www.scmp.com/news/china/article/1580226/shanghai-
san-...](http://www.scmp.com/news/china/article/1580226/shanghai-san-
francisco-100-minutes-chinese-supersonic-submarine)

Note also, misleading title. Supercavitation technology has been around for a
long time, the Chinese have solved some of the technical issues regarding
scaling up to full size Submarine and steering. Still no solution to range and
many of the related issues. Also unlikely to be put into service any time
soon.

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mannykannot
This appears to be about an entirely different technology. The original
article appears to be about the use of rim-driven electrical ducted
propellers.

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teapot01
Odd, I couldn't get the link to work so I googled the title and that was the
prominent result.

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neom
I didn't know about Supercavitation so that was still really interesting.
thanks.

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wyldfire
What of the turbulence just from the sub passing through the water? Can we
distinguish it from the background noise?

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clouddrover
It's doubtful our sonar would even pick it up. And if it did, it would sound
like whales humping, or some kind of seismic anomaly. Anything but a
submarine.

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oceanswave
A fourth million dollar computer tells you you're chasing an earthquake but
you don't believe it and you come up with this on your own?

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mberger
If I understand this right, aren't they putting the motor around the prop?
While it cuts down on noise, doesn't it increase, or at least give it a
distinct, magnetic signature?

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hwillis
The magnetic field of an electric motor only does any useful work when it is
inside the motor. There is no stray flux that would be usefully detectable.

Also, magnetic fields don't self propagate, really. That means they fall off
extremely quickly with distance unlike electromagnetic waves.

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coredog64
Magnetometers are already used to detect submarines [0]. Maybe it isn't so
much about the flux from the motor being detectable, but it's additional
interference with the Earth's magnetic field.

[0]
[https://en.m.wikipedia.org/wiki/Magnetic_anomaly_detector](https://en.m.wikipedia.org/wiki/Magnetic_anomaly_detector)

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simonh
They're used to detect the hull, which is why Titanium is valuable for use in
military submarine hulls as its non-magnetic. Fun fact, much of the Titanium
used in US submarine hulls was sourced from - er - the USSR. The needed the
foreign exchange more than it was worth denying the Titanium to the US.

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jonalmeida
Silly question, what other applications would work for rim-driven turbines
work? The naive side of me wants to see how it would work on a plane.

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basicplus2
"Oops! Something went wrong. Please scroll down to find your content..."

Nowhere to be found

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tomhoward
Popsci has geo-restricted content.

This should allow you to access it from anywhere:

[http://archive.is/mSo7F](http://archive.is/mSo7F)

