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MHD in Air

11/16/2017 4:41 PM

Basic question: Is ionization of air possible to sufficient extent with Tesla coils, etc. to produce a conductive low temperature plasma that can be induced to flow by the use of a non-stationary magnetic field.

Suppose this ionized gas will be in a large tube (but not too large?), and coils are affixed on the circumference of the tube. Magnetic pulses are directed to each coil in sequence. Timing would obviously need to be worked out.

Secondary question is, how much thrust in air could be possible at various altitudes.

Yes, this is yet another hare-brained scheme, the rest of the rabbits in the warren were too busy to talk this afternoon.

Based on the Lorentz force, MHD thrusters, Hall effect thrusters, and the like, I think this thing is a dog that won't hunt, does everyone agree? What if combined with high temperature combustion of a type that enhances ionization by many orders of magnitude?

Just having a brain storm on an exo-planet right now, probably dodging glass and/or steel rain on a really hot one.

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#1

Re: MHD in air

11/16/2017 5:30 PM

Sort of like a rail gun but with plasma? I like it!

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#2

Re: MHD in air

11/16/2017 5:35 PM

Oh so many acronyms when you get into ion thruster theory and technology.

Ok, before we start - MPD (or MPDT) is a Magnetoplasmadynamic thruster, HET is a Hall effect thruster, what is MHD?

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#3

Re: MHD in air

11/16/2017 5:50 PM

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#4
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Re: MHD in air

11/16/2017 5:56 PM

Well this is just cool...

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#8
In reply to #4

Re: MHD in air

11/16/2017 6:28 PM

Thanks... Care to guess what my 16 year old son and I are going to build?

I just showed him your video, he smirked and said "cool, how soon?" Tomorrow I order parts.......

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#12
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Re: MHD in air

11/17/2017 2:31 AM

Sounds like fun....I think I would modify the projectile....

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#13
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Re: MHD in air

11/17/2017 5:42 AM

Another fun project....and cheap too....

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#14
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Re: MHD in air

11/17/2017 8:22 AM

1) Not any guidance on how to get that nozzle absolutely concentric by hand drilling. Certainly wouldn't want any built-in side thrust.

2) No mention of the fuse to ignite the mixture.

When young, I was great fan of Jetex reusable, solid fuel rocket motors. They had their ignition problems and used a very thin, fragile wick with a copper wire core. I still have some Jetex motors and the fuel pellets (nitroguanidine), but all the igniting wick has long since deteriorated. Hard to think of a way to ignite the pellets via a very small nozzle. They were a slow ignite, slow burn fuel.

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#24
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Re: MHD in air

11/18/2017 4:18 PM
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#26
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Re: MHD in air

11/19/2017 5:47 PM

Bizarre remark. And the reason ........ ?

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#28
In reply to #14

Re: MHD in air

12/04/2017 2:01 PM

Word of caution , one Jet X contained inside any glass bottle will shatter it and send pieces into you.

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#29
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Re: MHD in air

12/04/2017 2:46 PM

I think you will find that you are talking about something completely different. Jetex and Jet X - two different things. Glass bottle? What on earth ........ ?

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#30
In reply to #14

Re: MHD in air

12/04/2017 3:53 PM

Estes rocket motors I had as a child used a thin pyrophoric coating on a thin wire, used a 12V battery for ignition. It was similar to the stuff used in "sparkler" firework. Maybe magnesium coated with some sort of protective layer that burned off when the wire got hot.

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#19
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Re: MHD in air

11/17/2017 11:21 AM

I sometimes think he gets these ideas from :

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#23
In reply to #19

Re: MHD in air

11/17/2017 1:40 PM

I have a copy of that book for "entertainment purposes".

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#5

Re: MHD in air

11/16/2017 5:59 PM

Guys, guys, guys.... This is about propulsion, not weapons.

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#6
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Re: MHD in air

11/16/2017 6:16 PM

A howitzer is simply a single-stroke propulsion engine.

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#9
In reply to #6

Re: MHD in air

11/16/2017 6:39 PM

You said it much better than I!

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#7
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Re: MHD in air

11/16/2017 6:19 PM
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#15
In reply to #7

Re: MHD in air

11/17/2017 9:16 AM

That is great for outer space, small payload, or larger systems where the engines are MUX.

I am more interested to see if some sort of plasma gun/fuel gun combo will produce far more thrust (at normal atmospheric pressure up to say 10,000 m altitude).

Why? Glad you asked...perhaps this might be a harbinger of lowering freight costs, reducing road traffic etc. Or maybe usher in a new era of thrill seekers wanting lighter

than air tourism.

Things to rule out: Lithium (although it has the highest specific impulse in plasma engines to date) - cost factor

Anything toxic in the environment we also rule out by default.

Nitrogen, oxygen, carbon dioxide (obtained by recovery from burning tires only) are OK.

The challenge will be to produce the most specific impulse with any prototype engine.

Gentlemen, start your engines (and your engineering). You have only two weeks to the finished product.

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#21
In reply to #15

Re: MHD in air

11/17/2017 11:36 AM

First we had Uber, then Google self driving cars, then Uber flying taxicab. Next week we will have plasma engined scootie coots.

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#22
In reply to #21

Re: MHD in air

11/17/2017 11:40 AM

Look. Do you want your Jetsons car or not?

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#10

Re: MHD in air

11/16/2017 9:17 PM

My understanding is MHD or magnetohydrodynamic propulsion is the acceleration of a conductive fluid through a magnetic field by an electrical current flowing through the fluid. The direction of flow, electric current, and magnetic field are all mutually perpendicular. The conducting fluid is propelled by the Lorentz force.

MHD thrusters have been proposed for submarine propulsion where salt water is the conducting fluid and the advantage is not generating much noise.

https://www.ijser.org/paper/Performance-analyses-of-MHD-Thruster-using-CAE-tools.html

A spacecraft version is the MagnetoPlasmaDynamic (MPD) thruster.

"A magnetoplasmadynamic (MPD) thruster (MPDT) is a form of electrically powered spacecraft propulsion which uses the Lorentz force (the force on a charged particle by an electromagnetic field) to generate thrust. It is sometimes referred to as Lorentz Force Accelerator (LFA) or (mostly in Japan) MPD arcjet.

Generally, a gaseous material is ionized and fed into an acceleration chamber, where the magnetic and electrical fields are created using a power source. The particles are then propelled by the Lorentz force resulting from the interaction between the current flowing through the plasma and the magnetic field (which is either externally applied, or induced by the current) out through the exhaust chamber. Unlike chemical propulsion, there is no combustion of fuel. As with other electric propulsion variations, both specific impulse and thrust increase with power input, while thrust per watt drops.

There are two main types of MPD thrusters, applied-field and self-field. Applied-field thrusters have magnetic rings surrounding the exhaust chamber to produce the magnetic field, while self-field thrusters have a cathode extending through the middle of the chamber. Applied fields are necessary at lower power levels, where self-field configurations are too weak. Various propellants such as xenon, neon, argon, hydrogen, hydrazine, and lithium have been used, with lithium generally being the best performer.

According to Edgar Choueiri magnetoplasmadynamic thrusters have input power 100–500 kilowatts, exhaust velocity 15–60 kilometers per second, thrust 2.5–25 newtons and efficiency 40–60 percent.[1][2]

One potential application of magnetoplasmadynamic thrusters is the main propulsion engine for heavy cargo and piloted space vehicles (example engine {\displaystyle a^{2}} for Manned mission to Mars).[1][2]

An MPD thruster during test firing

In theory, MPD thrusters could produce extremely high specific impulses (Isp) with an exhaust velocity of up to and beyond 110000 m/s, triple the value of current xenon-based ion thrusters, and about 25 times better than liquid rockets. MPD technology also has the potential for thrust levels of up to 200 newtons (N) (45 lbF ), by far the highest for any form of electric propulsion, and nearly as high as many interplanetary chemical rockets.[citation needed] This would allow use of electric propulsion on missions which require quick delta-v maneuvers (such as capturing into orbit around another planet), but with many times greater fuel efficiency.[3]"

https://en.wikipedia.org/wiki/Magnetoplasmadynamic_thruster

MPD would be useful is space where reaction mass is at a premium. In the atmosphere, reaction mass (air) is plentiful, and other forms of propulsion are more efficient.

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#11
In reply to #10

Re: MHD in air

11/17/2017 12:05 AM

Did you write all this yourself?

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#17
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Re: MHD in air

11/17/2017 10:01 AM

Please note the quote marks and the referenced link.

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#18
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Re: MHD in air

11/17/2017 11:14 AM

Juuuust checkin'.

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#16
In reply to #10

Re: MHD in air

11/17/2017 9:35 AM

Interesting summary.

Apparently, it would be easier to use fuel/air combustion waves in a tube.

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#20
In reply to #10

Re: MHD in air

11/17/2017 11:22 AM

I certainly agree with your comment, although NASA appears to be working on something like this for VTOL aircraft (most likely drones).

I suspect your "normal" gas turbine style turbo fan jet engine has about the highest specific thrust to weight ratio, and the highest available specific impulse with respect to pounds thrust/fuel lb consumed. The high turn down ratio makes them suitable for most all aspects of flight in ANY aircraft. The oriented duct versions are very interesting, but they might not be as suitable for use with lighter than air craft.

How about if the entire engine pod (which can be large or small??) could be gimbal mounted, even to the point of thrust reversal when docking?

Or simply use a high efficiency gas turbine (maybe even closed Brayton cycle) to power the entire craft, capture the CO2 and water (to whatever extent is convenient), use the CO2 for hydrogen lift bag blanketing sheath gas, use the water as cycle coolant, and the vapor for lift outside the lift bags but inside the envelope? The vapor would condense on selected portions of the skin, and cascade back to storage as coolant, or storage as selective ballast.

The lift bags need to be variable volume, withdrawing hydrogen or adding from time to time to assist with buoyancy against load, lift compensation, balancing for attitude control, etc. A redundant compressor system for the hydrogen. Obviously hydrogen purity monitoring is non-optional in any situation.

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#25
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Re: MHD in air

11/18/2017 4:30 PM

Maybe you could make a lighter than air , uh aircraft, that transformed into a more aerodynamic shape as it gains speed...

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#27
In reply to #25

Re: MHD in air

11/20/2017 9:06 AM

That is interesting! I know a buddy that might get sidetracked off our LENR experiments for this.

Suppose we use "muscle" polymer, and make the thing expand out blimpy style for take-off and landing, and compress to a lean profile for higher speed.

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