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MHD/EHD/Lorentz Plasma Thrust Propulsion for Airships

Posted by: sanman - Wed Sep 16, 2009 4:27 am
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MHD/EHD/Lorentz Plasma Thrust Propulsion for Airships 
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Post MHD/EHD/Lorentz Plasma Thrust Propulsion for Airships   Posted on: Wed Sep 16, 2009 4:27 am
Hi,

I've been reading about JP Aerospace for some years now, and their particular focus on light-than-air solutions, like balloons, airships, etc.

I'm wondering if anyone from there would care to comment on the idea of using an airship's uniquely large surface area for MHD/EHD/Lorentz propulsion. I'm not asking about this in connection with spaceflight really, but rather about its feasibility for propelling lighter-than-air vehicles for aerial transportation.

We've all read about how a blunt body passing through a plasma medium experiences significantly reduced drag, and of course few aircraft are as blunt-bodied as balloons and airships. So I'm imagining that these types of vehicles might benefit more than most from plasma aerodynamics. The very large size of the craft's surface area would compensate for the lower coupling efficiency of electromagnetic Lorentz force, to improve its performance.

Has anybody ever come up with a concept design for having an airship's hull produce a Lorentz force, so that the craft's entire body would become a propulsion system, directing the flowstream around it?

One of the tricks I'd read about, is that you should have a telescoping probe projecting far forward from your aircraft, producing an electrical arc to ionize the air ahead of it. You can also have it firing a counterflow plasma jet in the forward direction, which can also efficiently ionize the flowstream.

But rather than merely having your airship traveling through a locally ionized plasma enevelope, it should also be able to exert an electromagnetic Lorentz force on that ionized flowstream, using it to propel itself along. This would amount to a propulsion system with no moving parts, with associated reduction in wear and tear, maintenance, and failure risk. This type of propulsive force would easily facilitate vectored thrust, which would improve the handling/maneuvering capabilities of the craft, which would be crucial near the ground.

Furthermore, such combustion-free propulsion would be pollution-free, as well as being able to work in other atmospheres, such as on Mars or Venus, or in the thin upper atmosphere of the Earth. If the airship was a sufficiently streamlined lifting body, perhaps it could ascend to the upper atmosphere where it could stay for long duration. Military uses might include deployable stratellites, or surveillance drones with long loiter times, or even BMD radars with a long-horizon view.

I'm then wondering what configuration of magnetic and electrical elements would be optimal for producing this type of propulsion setup. If the airship was a dirigible/zeppelin, or even a hybrid airship with semi-rigid hull, then a large magnetic coil could be incorporated into the superstructure in order to produce magnetic field lines around the ship to exert force on the plasma flowstream. I'm also imagining that the ship's skin itself would have to be able to carry current or hold a charge to project an electric/electrostatic field to similarly produce electric field lines that would also similarly act on the plasma.

I've read that new materials under development like graphene-impregnated polymers could be highly impermeable to gas molecules, thus reducing the loss of lifting gas, thus facilitating long-duration stays in the upper atmosphere. Graphene also seems to have particularly high electrical conductivity, which might facilitate generating electric fields through the skin, and also potentially in harvesting solar energy.

I was thinking however that the best type of powerplant for such an electrically-powered craft would be a nuclear-electric power source, such as a SAFE-400 reactor coupled with a Stirling engine.

What do you all think of what I've said? Comments? Critiques?


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Post Re: MHD/EHD/Lorentz Plasma Thrust Propulsion for Airships   Posted on: Wed Sep 16, 2009 7:33 pm
The US Military is looking into MHD aircraft and spacecraft in combination with beamed energy propulsion. It has something like a 30 year technology horizon, but hypersonic shock tube tests are already underway.

There was a recent Spaceshow interviewwith the lead investigator.

It occured to me that beamed energy would solve all of JP's energy consumption problems.

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Post Re: MHD/EHD/Lorentz Plasma Thrust Propulsion for Airships   Posted on: Thu Sep 17, 2009 12:16 am
When I had the opportunity to talk to JP he said this is being worked on and is planned for at least one of the airships (not sure if he meant ascender, the orbiter, or both when we were talking about it). According to him, the technology to do it is well understood and the only reason it hasn't been done yet is because the aerospace industry is so risk-adverse. That being said, his timeframe for actually completing the program is ~20 years so a 10+ year technology is not unreasonable.

EDIT: actually, i'm pretty sure he's just talking about the drag reduction. I think they still plan on using propellers to control the DSS and ascender vehicles

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Post Re: MHD/EHD/Lorentz Plasma Thrust Propulsion for Airships   Posted on: Thu Sep 17, 2009 12:53 am
MHD propulsion has been tested for submarine propulsion, but, as far as I've heard, is not suitable. Considering that the density of conductor in sea water is high, whereas air isn't a good conductor, I would expect that if MHD propulsion were going to succeed anywhere, it would be in submarine propulsion. That it hasn't done so makes me skeptical of the chances of success for an airship.


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Post Re: MHD/EHD/Lorentz Plasma Thrust Propulsion for Airships   Posted on: Thu Sep 17, 2009 1:10 am
Hmm, sounds interesting, but I'd wonder if an onboard power supply isn't the better way to go. It seems like beamed energy would be a very tenuous way to do power an aircraft. In the case of an airship, its buoyancy would provide its aerodynamic stability, which would make it the simplest and least risky of any type of aircraft for hosting an onboard nuclear reactor. Modern advances like Doppler radar and LIDAR would make it easy to track any turbulence or adverse atmospheric conditions that might pose a threat, to further ensure safety.

But all of these unpowered forms of flight/launch -- whether catapults, ground-based laser heating.of propellant block, magnetic railgun acceleration, etc -- seem too risky in their own right, hence nobody has built anything like that yet. Anyway, I was talking about EHD/MHD for conventional air travel, and not for launching anything into space. I was thinking more along the lines of the proposed 'Walrus' program, but with the advantages of EHD/MHD that I proposed. A Walrus-type heavy-lift vehicle seems capable of lifting a heavier power supply capable of powering the EHD/MHD, whether that be fuel cells, or turbines, or ultracapacitors..

In my opinion EHD/MHD has the best chance of being demonstrated on an airship, as compared to any other type of platform, due to the uniquely high surface area and blunt volume of an airship, and its relative safety as an aerial platform.


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Post Re: MHD/EHD/Lorentz Plasma Thrust Propulsion for Airships   Posted on: Fri Sep 18, 2009 4:25 am
Here's an interesting technology useful for nuclear-electric propulsion:

http://en.wikipedia.org/wiki/Alkali-met ... _converter

I'm imagining that a Walrus-sized craft could have tens of megawatts available from this for MHD propulsion purposes.


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Post Re: MHD/EHD/Lorentz Plasma Thrust Propulsion for Airships   Posted on: Wed Sep 30, 2009 4:20 am
Oh! This will work! I am working on a flying model! Standby, EHD propulsion will surely work below the Crona Pressure range. Special Ion pumps will work at lower pressures you just watch! :)

Monroe

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