Plasma in a Microwave?

[JMBuilder]

I've seen videos of people putting an open flame in a microwave, placing a glass over it, turning the microwave on, and getting plasma. There was even a video of somebody getting plasma from... a grape? How does this work?

[Tex_NL]

You can find all about it right here.

[JMBuilder]

Could this be used to make creating plasma easier?

[Kryten]

Making plasma is already very easy. You know plasma TVs, or those plasma globes? They aren't just marketing terms.

[JMBuilder]

I know. But for something like an ion engine, would adding a small rocket and zapping the exhaust with microwaves make it even more efficient?

[zxczxczbfg]

What you've basically described is a thermal rocket.

[Bill Phil]

I know. But for something like an ion engine, would adding a small rocket and zapping the exhaust with microwaves make it even more efficient?

The VASIMR uses microwaves to turn argon into a plasma. In fact, I don't think this is plasma as in super-hot, but ionized to the point of having no electrons. So it wouldn't necessarily help your engine's efficiency.

[K^2]

Plasma is usually interesting as a state of matter due to an actual phase transition. This isn't what happening here. Plasma in microwave is a lot more like plasma in fluorescent lights. Except, instead of high voltage being applied between electrodes in a tube, high voltage is generated by high intensity of EM field.

You do need a source of free electrons to get the ball rolling. That's what hot carbon from something burning is good for. I honestly have no idea how or why it works with a grape.

[JMBuilder]

Would applying microwaves to rocket exhaust increase thrust?

[K^2]

Would applying microwaves to rocket exhaust increase thrust?

Short answer, no.

The more detailed answer would say that, yes, you can boost the power a bit, but your limitation will be in power you can deliver, and temperature your rocket engine can withstand. So you are better off just bringing more fuel along in any realistic scenario.

[Bunsen]

You do need a source of free electrons to get the ball rolling. That's what hot carbon from something burning is good for. I honestly have no idea how or why it works with a grape.

A grape split nearly in half and laid split-sides-down, with a tiny bit of skin connecting the two halves, acts as a dipole antenna. Most grapes are of such a size as to get within the ballpark of being a half wavelength at 2.4 GHz, even. The connecting skin quickly heats up from the large currents, and then it either ignites or ceases to conduct and then arcs over. Either way you get a little bit of plasma to seed the process.

[Scotius]

So, basically it is possible to build rocket engine out of microwave and a bunch of grapes? Of course the only way to power up such engine would be with potato batteries

[K^2]

So, basically it is possible to build rocket engine out of microwave and a bunch of grapes?

You have to get creative to find something you can't build a rocket engine out of.

[dharak1]

In reality you can fuel a rocket with anything. You can throw human waste out of a spacecraft to propel it. And correct me if I'm wrong but if you had an extremely dense element it could be extremely efficient per volume unit even just by throwing it out of the back of a rocket. By extremely dense I mean something with a density like 400 tons per cubic meter.

[Scotius]

Yes, but you would still need a power source sufficient to push that slab of denseness away. Speed is expensive

[JMBuilder]

What if you applied microwaves to the rocket exhaust and then used magnets to further propel the plasma?

[WestAir]

Then you would have the VASIMR engine.

[JMBuilder]

More like a chemical-rocket-VASIMR hybrid.

[Malokin]

human waste...400 tons per cubic meter.

You gotta start eating your greens.