DARPA’s silent MHD magnetic drives for replacing naval propellers

If it needs unobtainable levels of power, that means it's not efficient. If it's efficient you can use a diesel generator in place of your diesel engine and obtain the same amount of power.

Well, people are talking about 90% efficiency up-thread. You can't need unobtainable levels of power and still have 90% efficiency, as people move boats around every day.

Also, about the need for a coolant, well, the fixed costs for it are on the order of a few $100/m on most cities nowadays. If people start to use lots of it, the fixed costs will fall to zero. (The variable cost isn't high, but it also doesn't dictate the boat size.)

The government can and does lock down intellectual property for national security reasons.

The US government effectively locked down Juliet Marine Systems' IP, and gave the inventor no compensation for doing so. Took about more than 5 years for the inventor get any relief.

https://www.boatblurb.com/post/the-us-military-ghost-ship-is...

Yeah, that seems to be the way it always goes. It's not actually all that difficult to build an AESA radar in your garage, it's just very hard to get enough of the types of parts needed for a useful one without nation state level funding. The FPGAs they use are on Digikey....for 5-10k ea.

Or on the vessel itself it would have to be shielded for the people and for any equipment.

I've seen experiments where a device using a paddle was put against a person's head and a strong magnetic field emitted. It was a TV reporter for Discovery Channel Canada and her jaw convulsed, she did not look pleased.

I think the experiment was about spirituality of all things. How to induce a feeling of a presence to a person. I believe it was called the God helmet but in the video I saw it was a paddle.

Google scholar shows that that patent 'author' has three patents 1. Piezoelectricity-induced High Temperature Superconductor 2. Craft using an inertial mass reduction device 3. High frequency gravitational wave generator

https://patents.google.com/?inventor=Salvatore+Cezar+Pais

And I think with those three "inventions" one could construct a space-ship that could travel to Alpha Centauri at a meaningful fraction of 'c'.

Extraordinary claims require extraordinary evidence. Whatever is going on here, it's hard to take this document as evidence for a working room temperature superconductor...

the alternator is already there, too, since modern diesel submarines are actually diesel-electric submarines, able to charge batteries with the diesel engine and then shut it off and run from the batteries to go quiet

so, the difference is between props vs. no props, which is big.

> But you don't need that if the vessel is electric-powered, like a nuclear-powered sub

Yep.

> I believe some modern warships use a traditional motor to drive a generator, which drives an electric motor for propulsion

Sure, like a diesel-electric locomotive.

It turns out in some situations it's better to eat the conversion loss from electric generation rather than using a direct mechanical linkage, because then you can use flexible cables and electrical control systems rather than a bunch of mechanical folderol

The book's better, if you liked the movie.

It was actually the first "adult" book I read. Maybe when I was 9? I told my father I was bored of school books, and he handed it to me.

As well as Clancy's other stuff!

Just stop reading at 2000 (last recommended book: The Bear and the Dragon). After that he started phoning it in / lending out the name as ghostwritten brand.

I remember sitting in the dining room at four AM. JUST ONE MORE PAGE.

He did write about using an airliner as a missile years before it happened.

I'm not talking about him coming up with the ideas. But him weaving it as a thing the US Navy had been concerned about the Soviets building – I am saying it's very likely that the US Navy's concern about these drives being used in subs wasn't made up, and maybe some related conversations he had with contacts/sources, that turned out to be one of many seeds that made for a compelling story.

Here's one discussion in the book, clearly describing impellers in a tunnel. https://archive.org/details/huntforredoctobe0000clan_l6h7/pa...

For example, it says the US "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."

Wikipedia says, at https://en.wikipedia.org/wiki/The_Hunt_for_Red_October :

> The movie is a nearly faithful depiction of the novel even though there are many deviations, including Red October traveling up the Penobscot River in Maine to dry dock, the omission of the Royal Navy task force including Ryan's time aboard HMS Invincible, and the "caterpillar drive" being described as a magnetohydrodynamic drive system, essentially, "a jet engine for the water", rather than a drive powered by a series of mechanical impellers inside flow tunnels.

It’s one of the very few cases where I think both are great even though different and I don’t really see a way to improve either.

Reverify distance to server. One ping only.

It's an urban legend. ARPANET was an overgrown university network.

So true. I read once that fundamental physics research on quantum tunnelling in Japan resulted in antennas that immediately reduced satellite dish sizes from meters across to the size of a dinner plate. Now you can connect with a modern smart phone.

I think that was the point.

Uhhh I feel like rocket makers are obsessed with efficiency. A modest half a percent makes a huge difference in fuel fraction & lift capabilities.

Rockets may be broadly inefficient but they are as efficient as we can make them.

You don’t need to cancel it. Most electromagnetic surveillance systems have detection thresholds (e.g. in radar you have distance gate and return signal filters). Same applies for magnetically activated mines. Reducing the signature below detection thresholds is often enough. Alternatively masking the signature with another signal to confuse the detector also often works well.

EDIT: on second thought, if you can build a device to generate 20T you can probably build a contraption to cancel it out as well. It would most likely boil down to the economics or the scale of the contraption required.