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 Post subject: Coronal effect?
PostPosted: Sat Sep 15, 2018 7:13 pm 
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I have seen an interesting claim raised on my CotI Hard Space thread:

Quote:
I have had an idea that could make plasma rockets much more efficient - I call it the coronal engine.

One of the great mysteries of the sun is why its corona is way hotter than its surface - the smart money is there being a magnetic induction mechanism being involved.

So what if we use really powerful electromagnets to heat our plasma - we still need to learn the mechanism from studying the sun - and then chuck it out of the back of our rocket. We would need to use electromagnetic and electrostatic forces to contain and direct the plasma.

Outcome - much higher exhaust velocities, more efficient use of fuel, higher achievable thrust without the need for ship sized fusion reactors.


Quote:
A fusion rocket may be possible using magnetic constriction and magnetic fields to direct the fusing plasma, but you will need a fission power plant to provide the energy to power the magnets and initiate the partial fusion. I'm not even convinced you will need to achieve fusion, there is definitely a mechanism whereby hydrogen plasma can be heated to millions of degrees involving magnetism - the Sun's corona is proof of that.


What is your opinion on this?

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 Post subject: Re: Coronal effect?
PostPosted: Sun Sep 16, 2018 3:20 pm 
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Sounds like VASIMR to me.

In any case, the usual caveats about There Ain't No Such Thing As A Free Launch apply: there is a lot of loose energy in the vicinity of the sun. What may seem like a trivial discharge path on that scale may be much more difficult to recreate in the lab or on a ship.


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 Post subject: Re: Coronal effect?
PostPosted: Sun Sep 16, 2018 4:17 pm 
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thrash wrote:
Sounds like VASIMR to me.

In any case, the usual caveats about There Ain't No Such Thing As A Free Launch apply: there is a lot of loose energy in the vicinity of the sun. What may seem like a trivial discharge path on that scale may be much more difficult to recreate in the lab or on a ship.

Interesting. VASIMR is pretty fuel-efficient but has much lower acceleration than what this setting calls for.

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 Post subject: Re: Coronal effect?
PostPosted: Mon Sep 17, 2018 6:32 am 
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I'm not sure what is being suggested. What is the point of heating hydrogen to such temperatures, if not to achieve fusion? If the hydrogen is an inert propellant expelled using power from fission

(a) you want a high velocity, not high temperature, and a high temperature is at best an awkward intermediate to be converted to velocity by cooling in a rocket nozzle, and

(b) you would need to fission several kilograms of fission fuel to accelerate a steam of hydrogen to the sort of exhaust velocities obtainable in principle from fusion. If the spent fuel is jettisoned your specific impulse is subject to the theoretical limit for fission fuel, and if it is carried along that eats into payload, which is worse. No way does this end up in the performance range of a fusion drive.

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