DARPA’s silent MHD magnetic drives for replacing naval propellers

https://www.naval-technology.com/features/darpa-silent-mhd-magnetic-drives-for-replacing-naval-propellers/

by bookofjoe • 3 years ago

100 100 3 years ago

rektide2• 3 years ago

If power and efficiency issues are resolved,

My gut feel is that this is a pretty grossly inefficient system by nature. Inducing current in seawater just to give magnetic traction something to push off against seems semi absurd.

eqmvii• 3 years ago

semi absurd is kinda why DARPA exists!

ChrisMarshallNY• 3 years ago

The Register used to make fun of DARPA, saying things like “where every laugh is a mad cackle.”

beambot• 3 years ago

While we all communicate using TCP/IP, invented as a DARPA program for robust communication in the event of nuclear conflict...

imglorp• 3 years ago

What? VLSI, VHDL, Multics, Hypertext, GaAs semiconductors, autonomous navigation, GPS, and packet switched networking were a few things they funded. Totally absurd, right? For every successful tech, they probably explored scores that didn't pan out. Basic, high risk research has huge payoffs across society even if you don't like who's funding it or why.

bombcar3• 3 years ago

I mean rockets are absurd - burn gas to throw it behind you to push off against. Works in space (the NYT regrets the error).

https://www.nytimes.com/2001/11/14/news/150th-anniversary-18...

MilStdJunkie2• 3 years ago

That's very true, but "efficient" isn't usually an adjective thrown at a rocket.

marcosdumay3• 3 years ago

Purely-electric devices tend to have this property that if you maximize or minimize something with no clear theoretical limitation, your efficiency grows all the way to 1.

On the case of this, my gut feeling tells me that making the magnet really, really big will do it.

phkahler• 3 years ago

By using AC you can induce current in the water and avoid the need for electrodes, but low efficiency. By using high strength permanent magnets they can trade those.

zrail• 3 years ago

Isn't this the plot for Hunt for Red October?

2OEH8eoCRo0• 3 years ago

Yes. "Caterpillar drive". Fantastic book and movie.

atonse3• 3 years ago

I have watched the movie dozens of times. I really need to read the book.

atonse3• 3 years ago

Yes! I was thinking that as I read it. Alec Baldwin even says magneto hydrodynamic drive.

Yet another example of Tom Clancy’s incredible knowledge of the intricacies of what the military had on their radar and working that into great stories.

jasonwatkinspdx2• 3 years ago

Magneto Hydrodynamic Drives have been a publicly researched concept since the 60s. Magnetic pumps are used routinely in industry. You're definitely exaggerating how visionary Clancy was.

ckozlowski• 3 years ago

I recently re-read The Hunt For Red October, and what struck me was that there actually wasn't and mention of Magneto-hydrodynamic drive. As I recalled, the book describes a series of propellers in a duct. Certainly interesting for isolating sound, but it struck me as much more simplistic from the superconducting systems described in the movie.

No shade intended towards Mr. Clancy however. I got the impression that he was quite lauded for not simply describing tech (which other thriller writers did as well) but getting into the nuts and bolts of how they operated. That was what really set him apart.

tbrownaw• 3 years ago

I thought that was ducted props?

cwillu2• 3 years ago

The book has ducted props (which is where the distinctive noise comes from, a unexpected resonance from the length of the duct), the movie substituted MHD for the impeller.

ethbr02• 3 years ago

It was published by the (US) Naval Institute Press, their first published work of fiction. [0]

And yes. https://m.youtube.com/watch?v=SMCoIwsaRVw&t=1m31s

[0] https://en.m.wikipedia.org/wiki/The_Hunt_for_Red_October#Com... https://en.m.wikipedia.org/wiki/United_States_Naval_Institut...

temporallobe• 3 years ago

Beat me to it. Happens to be my favorite movie, ever. I’ve watched it so many times and I’m still not sick of it. What’s so beautiful about it is that it’s pure storytelling without a preachy agenda, though the irony is that it’s very much about politics and patriotism.

lunatuna• 3 years ago

The book is even better. I watched the movie about a half dozen times before I read the book and was amazed that I liked the book more. And I still think the movie is great.

jdougan• 3 years ago

It’s Tom Clancy’s future, we just live in it.

yellowapple• 3 years ago

"Can you ping, Washily? One ping only, pleashe."

cwillu2• 3 years ago

The Vilnius Schoolmaster deserves to be quoted correctly: “Give me a”, not “Can you”

SkyMarshal• 3 years ago

“If we meet the right shot, this will work. If we get some… buckaroo?…”

He needed someone on the US side to figure out he was defecting and meet him with a plan to help. He gave it 1 chance in 3. Loved that moment you reference when he realizes he did indeed meet the right shot.

efitz• 3 years ago

Engage the caterpillar dive, Vasily!

swader999• 3 years ago

"The thing about a new propulsion system, Captain, is its silence... and you don't have to touch a thing. It's all moved by electric currents and magnetic fields. Just one more step towards making submarines even more silent. The next 'Red October', if you will."

mLuby• 3 years ago

Wouldn't the intense electro-magnetic signature of this drive make it highly detectable in an otherwise quiet ocean?

mrcode0072• 3 years ago

Bay area waters were (are?) used as a naval magnetic silencing range. Most navy ships have degaussing coils that calibrate with magnetosphere

https://www.dropbox.com/s/qansmciigewti4n/IMG_2957.JPG?dl=0

murillians• 3 years ago

Degaussing in a bay is much different from trying to cancel out 20T(!!!) of EM signature

gpm6• 3 years ago

If they meet their 90% efficiency target, that's exceeding the efficiency of a normal boat. Just the propeller losses are higher than that (at ~80% efficient [1]).

If it's just some REBCO super-conducting magnets and conductive surfaces it might be reasonably inexpensive too. And without moving parts it could be a maintenance win as well.

I'm no sailor, but at first glance this seems like it would potentially replace all propulsion on boats/ships big enough to justify cooling REBCO. Obviously conditioned on actually reaching that fairly outrageous target.

[1] https://www.britannica.com/technology/naval-architecture/Act...

aardvarkr• 3 years ago

I agree that an innovation of this magnitude would have a huge impact on naval propulsion if it were publicly available though I’d imagine the tech would be locked down to a ridiculous level. It’s likely destined to only appear in nuclear submarines.

cyberax3• 3 years ago

Yeah, no. Once it's known that it's possible to achieve, some enterprising company will quickly replicate it.

Unless, of course, it needs unobtainable levels of power.

jandrese2• 3 years ago

I'm not sure it would be restricted so much as just way too expensive to be practical. There is also the practical considerations of generating 20T magnetic fields out in the real world and around people.

mikewarot2• 3 years ago

I suspect the Navy actually does have room temperature superconductors[1] ... which could make this a practical technology.

[1] https://patents.google.com/patent/US20190058105A1/en

jasonwatkinspdx2• 3 years ago

There's no reason to assume that. A ton of things DARPA pathfinds are commercialized, including the globe spanning network we're using to converse atm.

AustinDev• 3 years ago

The majority of DARPA research is public and you can get copies of the software or specs via an email typically.

jandrese2• 3 years ago

I'm taking that 90% efficiency figure with a grain of salt since that is the paper calculation in a technology that is still very experimental.

ajnin• 3 years ago

MHD is nothing new though, so if it has not yet replaced propellers I'm guessing it is because of practical issues like corrosion, electrolysis and so on alluded to in the article that DARPA seems to have found solutions for but which are not going to be available for the general public for obvious reasons.

Also it's all electric so it poses the usual problems like the added complexity of an on-board electric generator or the added weight and cost of a battery system.

hef19898• 3 years ago

So, the USN actually did park that Soviet sub captained by James Bond in a creek somewhere. I knew it!

gpm6• 3 years ago

Per the article the previous generation was only roughly 30% efficient, which makes it just not competitive with propellers.

Swapping out your diesel motor with rotating shafts going through your hull and an alternator to generate electricity for a diesel generator that just generates electricity is reducing complexity, not adding it.

denton-scratch• 3 years ago

because of practical issues

Like fitting supercooled tesla-power magnets to a moving vehicle, perhaps.

the added complexity of an on-board electric generator

But you don't need that if the vessel is electric-powered, like a nuclear-powered sub; and I believe some modern warships use a traditional motor to drive a generator, which drives an electric motor for propulsion (i.e. an electric ship powered by a fossil-fuel generator).

_trampeltier• 3 years ago

Yamato-1 looks so fast. I saw this ship in Kobe and i felt like in a Science Fiction movie. But ..

these ships were only able to reach speeds of 15 km/h.

https://en.m.wikipedia.org/wiki/Yamato_1

vba616• 3 years ago

The 70,000 ton Yamato battleship could go 50 km/h circa 1940:

https://en.m.wikipedia.org/wiki/Yamato-class_battleship

layer8• 3 years ago

Not to speak of its later wave-motion engine: https://yamato.fandom.com/wiki/Wave-motion_Engine_(2199)

kcplate• 3 years ago

I wonder if it sounds like whales humping or a seismic anomaly…

bowmessage• 3 years ago

Well, it's claimed to be silent, so probably not.

But, I went straight to whales as well, this could be a great option for a quiet whale watching boat.

nocoiner• 3 years ago

For a second… for a second, I thought I heard…

Singing.

tuatoru• 3 years ago

From the whales' point of view, if it is silent it would be great if every boat had it.

1. https://www.nhm.ac.uk/discover/news/2022/july/underwater-noi...

2. https://www.theguardian.com/environment/2022/apr/12/ocean-of...

3. Woods Hole, 2005: https://www.whoi.edu/oceanus/feature/how-to-see-what-whales-...

mattkrause• 3 years ago

(These are Red October references)

ljoshua• 3 years ago

You’ll just have to speed up the recording to 10x to find out… :)

tjmc2• 3 years ago

Ask Jonesie

jimjimjim• 3 years ago

It was Paganini

anonymousiam• 3 years ago

Very cool, and although the submarine may be silent, the magnetic anomaly could theoretically be detected and tracked.

mr_toad• 3 years ago

It won’t be completely silent because you’re still jetting a lot of water out the back of the submarine.

exabrial• 3 years ago

This is probably classified, but just how sensitive are MAD systems? A football field ship is a big chunk of metal and we’re ankle to detect them at some depth. One that has a 20 tesla magnet seems like painting a target on your own aft.

gpm6• 3 years ago

Wikipedia has some numbers - obviously there could be a difference between them and reality but they are a plausible starting point.

https://en.wikipedia.org/wiki/Magnetic_anomaly_detector#Oper...

fwlr• 3 years ago

I remember this technology being a plot point in a Clive Cussler novel, and then being standard issue on new boats in most Cussler novels after that. I see Tom Clancy also featured it in his books even earlier. It’s always cool when you first learn about some tech from near-future action novels and then later that tech becomes real; feels very futuristic.

fnord77• 3 years ago

are these power hungry?

wondering if it could replace the propeller on self-propelled hydrofoil surfboards

MagicMoonlight• 3 years ago

The idea of a boat with no moving parts is weird.

Since we’re already this deep into science-fiction, could we superheat air and then run the plasma through this in order to create a land or air vehicle with no moving parts?

gpm6• 3 years ago

It's been done, without superheating anything https://news.mit.edu/2018/first-ionic-wind-plane-no-moving-p...

The interesting question is could you do it efficiently and with sufficient thrust - I don't know.

ARandomerDude• 3 years ago

The world trembled at the sound of our rockets. Now they will tremble again at the sound of our silence.

desireco42• 3 years ago

I doubt this would be practical taking into account how strong magnetic field has to be.. I am wondering... am I missing something or nobody seriously thought about it?

bruce343434• 3 years ago

The MHD drive does not have moving parts, reducing noise and vibration, making it harder to detect via sonar

Uh what? Sonar is active detection, using the bouncing of emitted sound waves, no? Then I don't see how a silent engine makes it harder to detect via sonar if the signals will still bounce just as hard from the hull.

andkenneth• 3 years ago

There is passive sonar too, which is just listening.

regularfry• 3 years ago

Relevant to this: unimaginably vast amounts of effort have gone into making propellers a little bit quieter so they are harder to hear while still allowing reasonably high speeds. A lot of that is to do with avoiding cavitation at the prop tip, which is a) noisy, and b) very destructive. no prop, no prop noise...

fl7305• 3 years ago

A submarine is like a ninja. It tries to sneak around undetected.

Using active sonar is like placing a siren on your head.

rkangel• 3 years ago

What you are describing is active sonar. The downside of active sonar is that it also clearly reveals your own position.

As such, modern submarine warfare relies mostly on passive sonar - very sensitive microphone arrays (sometimes towed behind) to listen for audio signatures of surface and subsurface ships.

This means that submarine navies (and anti-submarine surface fleets to some degree) put a high priority on the ability to run quietly. A lot of work is put into things like propellor design to minimise the noise but there's a limit to how far you can go to eliminate cavitation and other noise sources. MHD, which would just be water flowing through a pipe, can potentially be much quieter.

HPsquared• 3 years ago

Passing electric current through seawater... Electrolysis will occur, producing hydrogen and chlorine gas (and some oxygen too).

It's not all positive, the are some negatives to this technology as well!

dr_dshiv• 3 years ago

Can something like this work for airships? Ionize and push air with all the solar electricity their surface area could generate?

typedef_struct• 3 years ago

"Captain, they've escaped." "How?" "Drove into freshwater"

AlbertoGP• 3 years ago

A couple of years ago someone built a model submarine with an actual MagnetoHydroDynamic drive:

“Magnet Powered Submarine - The Hunt for Red October IRL!” https://www.youtube.com/watch?v=nFsiydplCtw

The corresponding blog entry includes the STL files for 3D-printing the submarine’s hull:

https://www.kjmagnetics.com/blog.asp?p=red-october

DARPA’s silent MHD magnetic drives for replacing naval propellers

Related Stories