Bulked Up MHD Drive Makes Waves While Standing Still

Looking back through the archives, we actually haven’t seen much in the way of homebrew magnetohydrodynamic drives (MHDs) — which is somewhat surprising, as the core concept isn’t nearly as complicated as its syllable-laden name might indicate. You can see results with little more than a magnet, a couple of electrodes, and a bench power supply. The trick is turning these base components into something that might actually have practical value.

That’s where we find [Jay Bowles], who has gone down a bit of a MHD rabbit hole these last few months. His latest MHD unit is a considerable improvement over its predecessor by all practical metrics, and as an added bonus, really nails the look of a futuristic propulsion unit. Even though the all-electric thruster hasn’t gone on a mission to anywhere more exotic than a table-top aquarium, you could easily imagine a pair of them slung under some top secret stealth watercraft.

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A Magnetohydrodynamic Drive In The Kitchen Sink

The magnetohydrodynamic (MHD) drive certainly sounds like something out of science fiction — using an array of magnets and electrodes, this high-tech propulsion technology promises to silently propel a craft through the water without any moving parts. As long as you can provide it with a constant supply of electricity, anyway.

Of course, as is often the case, the devil is in the details. Even with the obvious scientific and military applications of such a propulsion unit, scaling MHD technology up has proven difficult. But as [Jay Bowles] of Plasma Channel shows in his latest video, that doesn’t mean you can’t experiment with the concept at home. Even better, getting verifiable results is much easier than you’d think.

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The Yamato 1, a sleek grey ship that looks vaguely like a computer mouse or Star Trek shuttlecraft. It has an enclosed cockpit up front with black windows and blue trim. It is sitting on land in front of a red tower at a museum in Tokyo.

Navy Program PUMPs Up Hopes For Magnetic Propulsion

The “caterpillar drive” in The Hunt for Red October allowed the sub to travel virtually undetected through the ocean, but real examples of magnetohydrodynamic drives (MHDs) are rare. The US Navy’s recently announced Principles of Undersea Magnetohydrodynamic Pumps (PUMP) intends to jump-start the technology for a new era.

Dating back to the 1960s, research on MHDs has been stymied by lower efficiencies when compared with driving a propeller from the same power source. In 1992 the Japanese Yamato-1 prototype, pictured at the top of the page, was able to hit a blistering 6.6 knots (that’s 12 kph or 7.4 mph for you landlubbers) with a 4 Tesla liquid helium-cooled MHD. Recent advances courtesy of fusion research have resulted in magnets capable of generating fields up to 20 Telsa, which should provide a considerable performance boost.

The new PUMP program will endeavor to find solutions for more robust electrode materials that can survive the high currents, magnetic fields, and seawater in a marine environment. If successful, ships using the technology would be both sneakier and more environmentally friendly. While you just missed the Proposers Day, there is more information about getting involved in the project here.

Be A Fire Bender With The Power Of Magnets

More often than you think, scientific progress starts with a simple statement: “Huh, that’s funny…” That’s the sign that someone has noticed something peculiar, and that’s the raw fuel of science because it often takes the scientist down interesting rabbit holes that sometimes lead to insights into the way the world works.

[Ben Krasnow] ended up falling down one of those rabbit holes recently with his experiments with magnets and flames. It started with his look at the Zeeman effect, which is the observation that magnetic fields can influence the spectral lines of light emitted by certain sources. In a previous video, [Ben] showed that light from a sodium lamp could be dimmed by a powerful electromagnet. Some of his viewers took exception to his setup, which used an oxy-acetylene flame doped with sodium passing through the poles of the magnet; they thought the effect observed was a simple magnetohydrodynamic effect, and not the Zeeman effect he was supposed to be testing. That led to the experiments in the video below, which started with a candle flame being strongly deflected by the magnet. [Ben] methodically worked through the problem, eliminating variables by going so far as to blow soap bubbles of various gasses within the magnet’s poles to rule out the diamagnetism of oxygen as a cause of the phenomenon. He finally showed that even hot air by itself is deflected, using a simple light bulb and a FLIR camera. It’s good stuff, and well worth a watch.

Spoiler alert: [Ben] is still scratching his head about what’s going on, and we’re looking forward to his conclusions. This isn’t his first rabbit hole expedition, of course; his experiments with creating plasma with high-pressure water were fascinating, as were his DIY superconducting ceramics. Continue reading “Be A Fire Bender With The Power Of Magnets”

A Caterpillar Drive That Actually Looks Like A Caterpillar

[Tom Clancy]’s The Hunt For Red October is a riveting tale of a high-level Soviet defector, a cunning young intelligence analyst, a chase across the North Atlantic, and a new submarine powered by a secret stealth ‘caterpillar’ drive. Of course there weren’t a whole lot of technical details in the book, but the basic idea of this propulsion system was a magnetohydrodynamic drive. Put salt water in a tube, wrap a coil of wire around the tube, run some current through the wire, and the water spits out the back. Yes, this is a real propulsion system, and there was a prototype ferry in Japan that used the technology, but really the whole idea of a caterpillar drive is just a weird footnote in the history of propulsion.

This project for the Hackaday Prize is probably the closest we’re going to see to a caterpillar drive, and it can do it on a small remote-controlled boat. Instead of forcing water out of the back of a tube with the help of magic pixies, it’s doing it with a piston. It’s a drive for a solar boat race, and if you look at the cutaway view, it does, indeed, look like a caterpillar.

Instead of pushing water through a tube by pushing water through a magnetic field, this drive system is something like a linear motor, moving a piston back and forth. The piston contains a valve, and when the piston moves one way, it sucks water in. When the piston moves in the opposite direction, it pushes water out.

The goal of this project is to compete against other solar powered remote-controlled boats. Of course, most of the other boats are using a DC motor and a propeller. This is a weird one, though, and we’re very interested in seeing how the production version will work.