Plasma channel has recently had a MHD series of videos the past season. The first design had an efficiency of 0.0054% while the latest was quite respectable at 0.05644%. The thruster is quite massive but it's nonetheless a very nice design. There's finally becoming a surge of interest on social media for MHD as of late.
Yes I have been following his development. Do you know how efficiency was calculated? I don't recall it being discussed in the video. All I saw were static tests at which propulsive efficiency is zero.
@@williamfraser Well this is the thing with Plasma Channel. It's geared for entertainment over showing fully transparent performance metrics necessary for everyone to truly evaluate for themselves the merit of the work. It's a UA-cam career effect of sorts. And you're right, it's not a thruster, its a pump on a pedestal in a tub of mystery water. _" Do you know how efficiency was calculated?"_ I am calculating efficiency myself based on the simple kinetic energy power formula from KE = 1/2 mv^2 to P = 1/2 * dm/dt * v^2 using mass flow rate instead of mass to get some ballpark figures for pump power / input power. TBH, I don't trust PC's flow rate numbers because he doesn't share volumes. He doesn't address units of his ruler or methods for calculation, just asserts his final numbers...and the flow across the ruler is turbulent, circulating and tumbling in the tub... I can only imagine he did a frame by frame analysis of flow only at the center of the flow rather than integrated across the flow cross section, because honestly how would this setup do that? PC's first design used 25V@12A = 300W and claimed to achieve exhaust velocity of 35 cm/s and flow rate 250 mL/s. In a previous video he claimed 75-100g of thrust with this design and 3W/g. PC's "BRM" design used 25V30A = 750W and claimed 47 cm/s exhaust fluid velocity at 3650 mL/s flow rate. Here he claims 0.2W/mL/s, annoying that he uses inconsistent units. Using data from design 2, I solve KE = 1/2mv^2, where m = 1050 kg/m^3 * 0.00365 m^3/s = 3.8325 kg/s mass flow rate , and v = 0.47 m/s. I found mass flow rate by choosing my own salinity of the salt water. You can use 3.5%, I used 8% or 1050 kg/m^3. Plasma Channel never clarifies %wt of his mixed mystery salt water. Sea water makes the most sense, but I just assumed a salinity closer to brine to get the best results. The numbers should only differ by less than 3% anyway, so it is fairly inconsequential in lieu of the staggering levels of error and uncertainty in the vid. So depending on the salinity, and hinging on how he calculates flow rate, his 750W MHD pump is imparting 0.42W of output power to seawater, or 0.48W to brine. So efficiency calculated this way would be between 0.055% and 0.064%. _"All I saw were static tests at which propulsive efficiency is zero."_ Yeah it's definitely not a thruster, he even anchored it to a pedestal. It should be treated as an MHD pump. I'd like to see it made to be laminar with a pipe of known dimensions and sufficient length added to the inlet to make proper steady-state measurements and examine the true flow rate and pressure. A static pressure test would compliment it as well, as a pump.
for efficiency the positif and negatif plate may can be inside container with hole in the bottom and up to capture the gas and uses as fue for fuell cell.
On page 39 of the yamato-1.pdf you can find online, Yohei Sasakawa views MHD propulsion as having super-high-speed benefits where screw drives thrust diminishes due to cavitation and other limits. Interestingly in this video, you make the remark that MHD drives are insensitive to fluid flow velocities, which seems to be true from that one catamaran paper. This seems to me that rather than replacing screws, they would make for a good multi-stage design, where a screw deals with slow inlet fluids, and an MHD generates fluid pressure immediately after it. Actually this seems pretty similar to a jet engine, only without compression, because fluids.
Current carriers are in the fluid itself which is moving orthogonal to the electric field... So presumably lorentz force applied is going to end up being rotated (about B axis)at some angle relative to the avg flow direction resulting in something roughly like a cos(k*v) relative efficiency. Anyways just a hypothesis
Great work on all your MHD stuff! I'm wondering what effect Hydrophobic and hydrophilic coatings might have on the electrodes and magnets..? Could a hydrophobic coating on the electrodes still allow current flow, but protect the electrodes from corrosion..? Hydrophilic on the magnet..? visa-versa, etc-etc..? Then the hull effects: Hydrophobic leading and hydrophilic trailing ..? etc Studies show philic giving better results, (less turbulent) but a phobic front wasn't tried. Off the shelf Hydrophobic coating: NeverWet superhydrophobic
Fantastic video once again. Those 3d printed hull models were beautiful, but I found myself most captivated by the characteristic curves and data visualization you put together for us, very nice! Looking forward to your next video on efficiency. I imagine it will spur many discussions in the comments. Also, given the Yamato was the control and worst performer across the full range, do you have a clearer picture what on Earth the purpose of such a hull was vs where you were half a year ago during the RC tests when you described the design as baffling that it seemed to entirely emphasize course stability? I still hold the opinion that they were aware of the limitations of the technology and the funding constraints, and instead focused on the feasibility of portable cryogenics. I don't know if course stability is a bigger consideration at low speeds or high speeds, but a second baffling decision was to publish their results using a purely DC-driven design as opposed to an AC-driven design which would have simplified their system and reduced conversion losses of the AC diesel generators. @manipulativer even pointed out in the RC video that Mitsubishi was well-aware of the efficiency benefits of an AC-driven MHD. That comment makes it difficult for me to believe such a possibility wasn't apparent at the time. Maybe there was a private investor that benefitted from the Yamato hull design with a more efficient MHD implementation. Along that line of thought, what organizations did the Yamato-1 team work for after the study, and were all the funding sources publicly disclosed? And is there any visible AC MHD thruster works that could be used to compare relative efficiency beside the intuition that it overcomes the shortfalls that DC has?
I am still no closer to understanding their choice in hull shape. I don't know enough about course stability to appreciate how important it really was, or how many other options were considered. I suppose from a PR perspective the shape they chose is a better match for the futuristic image of the project. Seeing the ship in its current static display is an impressive sight, and sacrificing a knot in the name of inspiration of future generations isn't that bad. The DC choice was based on the use of the superconducting coils which generate a static field. Future efficiency improvements will depend almost entirely on improvements in superconducting materials and higher magnetic field strength.
@@williamfraser _"Future efficiency improvements will depend almost entirely on improvements in superconducting materials and higher magnetic field strength."_ I don't know about that. Yamato-1's Yohei Sasakawa longs for better permanent magnets (and this was in the 90s) without painstakingly battling with such significant hoop stress issues in superconductors. I would bank on working fluid conductivity improvements being far easier to realize and commercialize than better superconductors to improve magnetic field strength, critical current density, and high critical temperatures. Like we discussed many months ago, supersaturated brine solutions into a duct would dramatically improve efficiency much like a stronger magnetic field would. There are also yet unrealized configurations of MHD that can take advantage of superconductive liquid metal alloys like Galinstan, where a momentum transfer transmission can retain the precious working fluid from being lost to the ocean. And most importantly (to me at least) the efficiency of other modes of MHD like AC, or pulsed DC systems that eliminate the conduction losses and electrolysis losses of any working fluid. And I can't even get into plasma ionocraft-MHD drives either, very exotic.
@@williamfraser Reposting deleted comment and pruning to make YT comment deleter happy... "I am still no closer to understanding their choice in hull shape. " I found a publication that goes into great detail the design of the hull. Published and printed in '97 by Ship & Ocean foundation in Kobe, Japan, there is a yamato-1 pdf on the Sasakawa Peace Foundation's website. Navigate to page 100 (Chapter 8 Hull and Outfit). After the pretext, they discuss each individual design requirement leading them to the particular hull shape where course stability is also mentioned (page 108 onward). "The DC choice was based on the use of the superconducting coils which generate a static field." Yes, after reading the 163 page publication, it's apparent the design is suitable only for DC. However I should point out that not all superconducting coils will always be static. This one was brittle, had hoop stress challenges, stored 23MJ of energy for a 4T design with 500 turns of wire, and was inclined to quenching itself if current was not charged up gradually and in small increments to avoid a dramatic expansion from throwing the coil out of the superconducting state. So it makes sense to go DC given a type II superconductor like NbTi was already a compromise at the time to make the 3d saddle coil geometry they wanted. It was a huge compromise that allowed the project to be feasible which meant not choosing Nb3Sn which would have put propulsive efficiency in line with screw props, albeit with bigger project risks. That being said, They claimed to have considered AC superconducting coils but chose not to use it in the Yamato-1 because "a practical application of an AC superconducting magnet was not available". So considered but not ventured. Perhaps there was more to this kept undisclosed within Mitsubishi Heavy Industries that was not covered in the publication, as this is all that made it to the print for AC MHD.
Another thought: If you want to add sails what about a magnetic keel? I'm thinking north in front with its own electrodes and south at the back with a second (distant) set of swapped electrodes??
thrust generated - craft velocity = actual thrust. maybe you can never go faster than the thrust you are generating - drag. in my head it sounds right as their has to be some proportional componant to the relative velocity. if you think of the propulsion acting on an area over time, then the speed of the water would reduce the time it ewas exposed to the area and would as such require a larger area of influance in order to maintain a constant thrust. the force trancefer between craft on medium is not instant but over a period of time. however or therefor the thrust might not top out at the stationary thrust value but at a proportian amount to the velocity. hope this is understandable and maybe even right.
Would love to see a final project. I hope you keep going
Plasma channel has recently had a MHD series of videos the past season. The first design had an efficiency of 0.0054% while the latest was quite respectable at 0.05644%. The thruster is quite massive but it's nonetheless a very nice design. There's finally becoming a surge of interest on social media for MHD as of late.
Yes I have been following his development. Do you know how efficiency was calculated? I don't recall it being discussed in the video. All I saw were static tests at which propulsive efficiency is zero.
@@williamfraser Well this is the thing with Plasma Channel. It's geared for entertainment over showing fully transparent performance metrics necessary for everyone to truly evaluate for themselves the merit of the work. It's a UA-cam career effect of sorts. And you're right, it's not a thruster, its a pump on a pedestal in a tub of mystery water.
_" Do you know how efficiency was calculated?"_
I am calculating efficiency myself based on the simple kinetic energy power formula from KE = 1/2 mv^2 to P = 1/2 * dm/dt * v^2 using mass flow rate instead of mass to get some ballpark figures for pump power / input power. TBH, I don't trust PC's flow rate numbers because he doesn't share volumes. He doesn't address units of his ruler or methods for calculation, just asserts his final numbers...and the flow across the ruler is turbulent, circulating and tumbling in the tub... I can only imagine he did a frame by frame analysis of flow only at the center of the flow rather than integrated across the flow cross section, because honestly how would this setup do that?
PC's first design used 25V@12A = 300W and claimed to achieve exhaust velocity of 35 cm/s and flow rate 250 mL/s. In a previous video he claimed 75-100g of thrust with this design and 3W/g.
PC's "BRM" design used 25V30A = 750W and claimed 47 cm/s exhaust fluid velocity at 3650 mL/s flow rate. Here he claims 0.2W/mL/s, annoying that he uses inconsistent units.
Using data from design 2, I solve KE = 1/2mv^2, where m = 1050 kg/m^3 * 0.00365 m^3/s = 3.8325 kg/s mass flow rate , and v = 0.47 m/s.
I found mass flow rate by choosing my own salinity of the salt water. You can use 3.5%, I used 8% or 1050 kg/m^3. Plasma Channel never clarifies %wt of his mixed mystery salt water. Sea water makes the most sense, but I just assumed a salinity closer to brine to get the best results. The numbers should only differ by less than 3% anyway, so it is fairly inconsequential in lieu of the staggering levels of error and uncertainty in the vid.
So depending on the salinity, and hinging on how he calculates flow rate, his 750W MHD pump is imparting 0.42W of output power to seawater, or 0.48W to brine.
So efficiency calculated this way would be between 0.055% and 0.064%.
_"All I saw were static tests at which propulsive efficiency is zero."_
Yeah it's definitely not a thruster, he even anchored it to a pedestal. It should be treated as an MHD pump.
I'd like to see it made to be laminar with a pipe of known dimensions and sufficient length added to the inlet to make proper steady-state measurements and examine the true flow rate and pressure. A static pressure test would compliment it as well, as a pump.
for efficiency the positif and negatif plate may can be inside container with hole in the bottom and up to capture the gas and uses as fue for fuell cell.
On page 39 of the yamato-1.pdf you can find online, Yohei Sasakawa views MHD propulsion as having super-high-speed benefits where screw drives thrust diminishes due to cavitation and other limits.
Interestingly in this video, you make the remark that MHD drives are insensitive to fluid flow velocities, which seems to be true from that one catamaran paper. This seems to me that rather than replacing screws, they would make for a good multi-stage design, where a screw deals with slow inlet fluids, and an MHD generates fluid pressure immediately after it. Actually this seems pretty similar to a jet engine, only without compression, because fluids.
Current carriers are in the fluid itself which is moving orthogonal to the electric field... So presumably lorentz force applied is going to end up being rotated (about B axis)at some angle relative to the avg flow direction resulting in something roughly like a cos(k*v) relative efficiency. Anyways just a hypothesis
Great work on all your MHD stuff!
I'm wondering what effect Hydrophobic and hydrophilic coatings might have on the electrodes and magnets..?
Could a hydrophobic coating on the electrodes still allow current flow, but protect the electrodes from corrosion..?
Hydrophilic on the magnet..?
visa-versa, etc-etc..?
Then the hull effects:
Hydrophobic leading and hydrophilic trailing ..? etc
Studies show philic giving better results, (less turbulent) but a phobic front wasn't tried.
Off the shelf Hydrophobic coating: NeverWet superhydrophobic
Fantastic video once again. Those 3d printed hull models were beautiful, but I found myself most captivated by the characteristic curves and data visualization you put together for us, very nice!
Looking forward to your next video on efficiency. I imagine it will spur many discussions in the comments.
Also, given the Yamato was the control and worst performer across the full range, do you have a clearer picture what on Earth the purpose of such a hull was vs where you were half a year ago during the RC tests when you described the design as baffling that it seemed to entirely emphasize course stability?
I still hold the opinion that they were aware of the limitations of the technology and the funding constraints, and instead focused on the feasibility of portable cryogenics. I don't know if course stability is a bigger consideration at low speeds or high speeds, but a second baffling decision was to publish their results using a purely DC-driven design as opposed to an AC-driven design which would have simplified their system and reduced conversion losses of the AC diesel generators. @manipulativer even pointed out in the RC video that Mitsubishi was well-aware of the efficiency benefits of an AC-driven MHD.
That comment makes it difficult for me to believe such a possibility wasn't apparent at the time. Maybe there was a private investor that benefitted from the Yamato hull design with a more efficient MHD implementation. Along that line of thought, what organizations did the Yamato-1 team work for after the study, and were all the funding sources publicly disclosed? And is there any visible AC MHD thruster works that could be used to compare relative efficiency beside the intuition that it overcomes the shortfalls that DC has?
I am still no closer to understanding their choice in hull shape. I don't know enough about course stability to appreciate how important it really was, or how many other options were considered. I suppose from a PR perspective the shape they chose is a better match for the futuristic image of the project. Seeing the ship in its current static display is an impressive sight, and sacrificing a knot in the name of inspiration of future generations isn't that bad.
The DC choice was based on the use of the superconducting coils which generate a static field. Future efficiency improvements will depend almost entirely on improvements in superconducting materials and higher magnetic field strength.
@@williamfraser _"Future efficiency improvements will depend almost entirely on improvements in superconducting materials and higher magnetic field strength."_
I don't know about that. Yamato-1's Yohei Sasakawa longs for better permanent magnets (and this was in the 90s) without painstakingly battling with such significant hoop stress issues in superconductors.
I would bank on working fluid conductivity improvements being far easier to realize and commercialize than better superconductors to improve magnetic field strength, critical current density, and high critical temperatures. Like we discussed many months ago, supersaturated brine solutions into a duct would dramatically improve efficiency much like a stronger magnetic field would. There are also yet unrealized configurations of MHD that can take advantage of superconductive liquid metal alloys like Galinstan, where a momentum transfer transmission can retain the precious working fluid from being lost to the ocean.
And most importantly (to me at least) the efficiency of other modes of MHD like AC, or pulsed DC systems that eliminate the conduction losses and electrolysis losses of any working fluid. And I can't even get into plasma ionocraft-MHD drives either, very exotic.
@@williamfraser Reposting deleted comment and pruning to make YT comment deleter happy...
"I am still no closer to understanding their choice in hull shape. "
I found a publication that goes into great detail the design of the hull. Published and printed in '97 by Ship & Ocean foundation in Kobe, Japan, there is a yamato-1 pdf on the Sasakawa Peace Foundation's website. Navigate to page 100 (Chapter 8 Hull and Outfit). After the pretext, they discuss each individual design requirement leading them to the particular hull shape where course stability is also mentioned (page 108 onward).
"The DC choice was based on the use of the superconducting coils which generate a static field."
Yes, after reading the 163 page publication, it's apparent the design is suitable only for DC. However I should point out that not all superconducting coils will always be static. This one was brittle, had hoop stress challenges, stored 23MJ of energy for a 4T design with 500 turns of wire, and was inclined to quenching itself if current was not charged up gradually and in small increments to avoid a dramatic expansion from throwing the coil out of the superconducting state. So it makes sense to go DC given a type II superconductor like NbTi was already a compromise at the time to make the 3d saddle coil geometry they wanted. It was a huge compromise that allowed the project to be feasible which meant not choosing Nb3Sn which would have put propulsive efficiency in line with screw props, albeit with bigger project risks.
That being said,
They claimed to have considered AC superconducting coils but chose not to use it in the Yamato-1 because "a practical application of an AC superconducting magnet was not available". So considered but not ventured. Perhaps there was more to this kept undisclosed within Mitsubishi Heavy Industries that was not covered in the publication, as this is all that made it to the print for AC MHD.
Another thought:
If you want to add sails what about a magnetic keel?
I'm thinking north in front with its own electrodes
and south at the back with a second (distant) set of swapped electrodes??
Have you measured the current of the drive when it’s running on the water?
Also measured relative to the speed.
thrust generated - craft velocity = actual thrust. maybe you can never go faster than the thrust you are generating - drag. in my head it sounds right as their has to be some proportional componant to the relative velocity. if you think of the propulsion acting on an area over time, then the speed of the water would reduce the time it ewas exposed to the area and would as such require a larger area of influance in order to maintain a constant thrust. the force trancefer between craft on medium is not instant but over a period of time. however or therefor the thrust might not top out at the stationary thrust value but at a proportian amount to the velocity. hope this is understandable and maybe even right.
A pill shape is better for fluid flow and conforms to magnetic field curves .
A ship hull should right itself.