Magnetic Thrusters: The FUTURE of Propulsion Technology

A very intriguing propulsion drive has the potential to transform both underwater and aerospace vehicles. Titled the Magneto Hydrodynamic Thruster, it has no moving parts and is completely silent. It works by utilizing electrodes that provide a magnetic and electric field, and this can accelerate a conductive fluid. Fictional movies like The Hunt for Red October have dramatized the performance of the MHD thruster, and it was a concept that was a A couple years later in the 90s in real life, the Yamato-1 came out from Japan. It utilized a similar type of propulsion that was completely silent by itself, and could glide through the water without any moving parts. Conceptually this drive seems to be perfect, but it's far from that, because it needs to be cryogenically cooled, it requires huge amounts of power, and it can still be magnetically detected. Not to mention that it had diesel generators that produced an acoustic signature. In the end, the Yamato can only obtain a speed of 8 knots, which is not very comparable to modern submarines. But if this drive can be advanced, it could offer greater maneuverability, increase cavitation limits, and offer a positive ecological impact because it does not produce any noise. And in theory, a nuclear powered MHD submarine has the potential to reach over 100 knots, which is twice the speed of the fastest submarine in the world. So even though this drive was dramatized in fictional stories, it actually has a lot of potential, and there are new advancements that can make it even more viable today. To understand this, we have to look at how MHD thrusters even work. These drives utilize the Lorentz force, and this is basically a push that magnetic and electric fields give to moving charges. You can design the drive with the direction of the magnetic force using the right hand rule, and this is calculated using a current density and a magnetic flux density. Depending on the volume and geometry, you can see different variations of this formula, and these drives work on the principle of utilizing an anode and cathode. In this example, we can see a MHD pump moving liquid metal at a pretty noticeable flow rate. One of the best compositions out there is gallium, indium, and tin. It is highly conductive, has a good temperature range, and a low viscosity, meaning that it has a good flow rate, and this can be used in efficient conversions of kinetic energy into electricity, or vice versa. So it's great for isolated systems like nuclear reactors or even cooling. In the future, an MHD nuclear power generator with liquid metal could directly convert thermal energy into electricity without rotating parts, and in theory this could be more efficient than steam power generation. But the system is really hard to build, and so far it's only in research phase. The seawater MHD thruster also has a very similar design. It has an intake, two electrodes, and this induces a current in a perpendicular magnetic field and creates flow. However, we are talking about seawater as the medium instead of liquid metal, and now the game has completely changed. That is because seawater has much lower conductivity, so the drive has to work much harder, meaning that it has to move larger volumes to obtain the same propulsive effect as a liquid metal drive. And this is why we see very high amperage for Tesla field in the old Yamato-1 just to obtain 8 knots. Now that was all the way back in 1992, and we are seeing advances in high temperature superconducting magnets, which can handle over 20 Tesla in a similar setup. These are powerful magnets made from high temperature superconducting materials, so there is zero electrical resistance, and they can carry 150 times the current of copper. However, so far we have to cool these materials to cryogenic temperatures, minus 196 degrees Celsius, so you have to use liquid nitrogen or helium, which makes the system a lot more complicated. But this is only half the challenge in an MHD drive, because the electrodes typically form oxygen and hydrogen gas bubbles on its surface, and this causes the electrodes to corrode in seawater, which is bad for efficiency and lifespan. The good news is that we have pretty advanced computational fluid dynamics, which basically is computer simulation, and this can optimize a fluid channel design. So if you can develop a superconducting magnet that can get around the corrosion problems, then you are definitely in business, but you would still need a very high energy source. Now thankfully in a lot of submarines there are modern pressurized water nuclear reactors. The Ohio class submarine utilizes an S8G PWR nuclear reactor that can generate over 45 megawatts of power, so in theory it is possible to supply huge amounts of power to an HTS magnetic MHD drive system. So at least conceptually we know how to build this drive, and to nobody's surprise HRL Laboratories under DARPA has claimed that they have built an MHD pump that can survive seawater's corrosive environment. More specifically they have found a durable electrode coating. If it's built out of a superconducting material, then it could have a very high magnetic field, meaning that it could provide a substantial propulsive force. Another really notable advancement we have seen is the 36MW HTS superconducting propulsion motor. This was developed under the US Navy, and it was designed to meet the power requirements of the future DDG-1000 class ships. It offered significant advantages including being less than half the size and weight of a conventional copper motor. So there is no doubt that the Navy has some knowledge on how to develop a cryogenically cooled MHD drive system with high temperature superconducting magnets. There was also the release of new electrodevelopment from DARPA's program. Now the question is whether or not they're going to develop a prototype in a nuclear powered submarine, because in my opinion I think that's the only way that you're going to get a high enough energy source to make this all viable. And whether or not that will be publicly known, well that's another question. This does not mean that the MHD drive will be breaking any speed records anytime soon. Even with a streamlined design in a 45MW reactor, you might be able to achieve 20 knots with 30% efficiency, which is definitely not too bad, but it can get outperformed by a mechanical propeller. So the system is really dependent on new energy innovations. Now NASA is experimenting with MHD prototypes that can control the air. That means a futuristic hypersonic craft could steer the plasma and reduce drag, maybe even generate electricity from it. If possible, then it could supersede passive aerodynamic structures. There is a lot of research going into controlling shockwaves and reducing heating during atmospheric entry for space vehicles, so there is no doubt that there is a future for MHD propulsion. Furthermore, there are space engines like the VASMIR that utilize MHD principles, and this could be revolutionary for space travel, which I will definitely cover in another video. Ultimately the MHD design can be utilized in a lot of different applications, but it is still hugely bottlenecked by its energy source. So once again, thanks for watching, please like the video if you did enjoy it, and make sure to subscribe to my channel.