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Magnetoplasmadynamic Thruster

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Squidhat

Fri Aug 14 2009, 10:45PM

Registered Member #2295 Joined: Fri Aug 14 2009, 10:17PM
Location:
Posts: 3

Hello,
I'm new here, and truth be told, not very good at electronics. I just have a few quick questions right now (then off to more lurking), but first, I'll lay out what I'm doing.
I'm in the design process of building a MagnetoPlasmaDynamic Thruster (MPD or MPDT) that uses Lithium as a fuel source. I'm putting it in the electromagnetic projectile accelerators section because it uses the Lorentz force to shoot out plasma as a "projectile".
To work, it needs to be able supply a large current over a gap (under high vacuum and across vaporized lithium). Voltages of around 31kv, and a current of about 500 or more amps. The quick questions are:
Is there any way to keep 31kv and 500/500+ amps going for exactly one minute (lots of times) that is remotely cheap (high schooler budget)?
Can I implement a high voltage power supply and high current power supply in the same pulsing circuit, or do I have to go with a capacitor?

Below is a link to a website that has a circuit planned out. I could use this, but I want to get rid of the air core transformer, in the very least.

http://www.myelectricengine.com/projects/mpdthruster/ignition/ignition.html#construction

[Edit: Fixed URL]

big5824

Fri Aug 14 2009, 10:52PM

Registered Member #1687 Joined: Tue Sept 09 2008, 08:47PM
Location: UK, Darlington
Posts: 240

500 amps??? dont you mean miliamps? you would need a personal power plant to run at 31kv 500A.....

even if you do mean 500mA, thats still over 15KW, a supply like that is probably wayyyy over your budget.

On a highschool budget i imagine the best you will get is around 15mA at 30kv from a flyback, which i know can be used for lifters etc so it could work for this

aonomus

Fri Aug 14 2009, 11:12PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

And yes, for a quick sanity check, 31kV at 500A is 1.5 megawatts. The guy who made his thruster did it in pulsed mode, and especially so because in space you won't have nearly that much power, except for a slow charge. Good luck trying to find that on a highschooler budget.

If you want to try to get higher currents, you might look at trying to design a high voltage power supply, but if this is your first project, I would not recommend continuing as its pretty dangerous to just jump into it.

If you are really up to it, this can produce 15kV at 500mA, solid state (or you could just find a pole pig transformer, but again, equally lethal).

And if you find that too intimidating, you might want to read up about voltage multipliers, and marx generators.

hvguy

Sat Aug 15 2009, 04:19AM

Registered Member #289 Joined: Mon Mar 06 2006, 10:45AM
Location: Conroe, TX
Posts: 154

Let's see, for that kind of power your looking at two options: 1) capacitor bank or compulsator 2) huge power supply. Since a power supply that large is basically it's own substation, the cap bank sounds a bit more realistic, but not much. 31KV x 500A = 15.5MW and 15.5MW for 1Min is 15500000w x 60sec = 930MJ so if we take losses into account your probably looking at a +1GJ energy storage system, which is DARPA level shit. According to the link you provided, you don't need anywhere near that much energy. You should take a look at your design again...

aonomus

Sat Aug 15 2009, 06:50AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

hvguy wrote ...

31KV x 500A = 15.5MW

Oops, forgot to carry the one.

Anyway, part of a good project is doing some sort of research that can be applied, a 15.5MW 930GJ thruster won't get you anywhere if all you have in space is a limited launch payload with no space for a large nuclear reactor...

Squidhat

Sun Aug 16 2009, 04:15AM

Registered Member #2295 Joined: Fri Aug 14 2009, 10:17PM
Location:
Posts: 3

Right. Hope for the best, prepare for the worst. I was guessing there was no way I could pull off sustained, so I'm kinda prepared to go with a pulsed system. But hey, NASA's working on pulsing this engine at Glenn Research Center.

By the way, I forgot to mention that I'm about 40 mins away from a big Aerospace engineering school (with big labs and equipment), so I could probably use some of their electrical equipment.

And about the nuclear reactor in space: NASA was working on it until the government shut off funding. Almost had a reactor that could produce that energy.

hvguy

Sun Aug 16 2009, 06:10AM

Registered Member #289 Joined: Mon Mar 06 2006, 10:45AM
Location: Conroe, TX
Posts: 154

A good friend of mine worked for NASA at the ASPL on a similar thruster, they did everything in a high vacuum. You may want to consider starting at a relatively low power and investing in a vacuum rig. Either way, good luck!

Squidhat

Sun Aug 16 2009, 11:02PM

Registered Member #2295 Joined: Fri Aug 14 2009, 10:17PM
Location:
Posts: 3

Dang it! Did I not mention that I was gonna have the thing in a vacuum? Well I am.

GrimX9

Thu Sept 23 2010, 02:07PM

Registered Member #3225 Joined: Wed Sept 22 2010, 02:14AM
Location:
Posts: 24

Sorry for thread necro post, dove a little too deep into old threads.

Turkey9

Fri Sept 24 2010, 01:40AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

So what ever happened to this project? Is he still here? Did a device ever get constructed?

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