Using atmosphere as propellant

Discuss the technical details of an "open source" community-driven design of a polywell reactor.

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DeltaV
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Postby DeltaV » Fri Jul 09, 2010 5:56 am


GIThruster
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Postby GIThruster » Fri Jul 09, 2010 6:31 am

"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

GIThruster
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Postby GIThruster » Fri Jul 09, 2010 10:47 pm

"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

GIThruster
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Postby GIThruster » Fri Jul 09, 2010 10:56 pm

"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

DeltaV
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Postby DeltaV » Sat Jul 17, 2010 6:57 am


DeltaV
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Postby DeltaV » Sat Jul 17, 2010 9:39 pm


zapkitty
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Postby zapkitty » Sat Jul 17, 2010 11:22 pm


DeltaV
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Postby DeltaV » Tue Jul 20, 2010 6:58 am

Figure 7 from
M. Frantz, "A Focusing Property of the Ellipse", American Mathematical Monthly, 101 (1994), p 250-258
Image
Everything tends to end up on the line containing the foci. Flatter ellipses concentrate wavefronts faster. The paper assumes photons and a perfect reflecting surface. Shock waves in a gas are probably more prone to dispersal, but the general effect could be similar.

zapkitty
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Postby zapkitty » Tue Jul 20, 2010 8:29 am

It all depends on your parameters, of course, but is an arc the best way of transfering MWe to MWt to kN?

I'd wonder if, given the known efficiency of impellers in converting MWe to kN, if it might be more efficient to accept the downconversion mass penalty and just use blades until you're going fast enough to switch to a microwave heated fanjet and then later on to ramjet mode... all the while using MHD techniques when and where appropriate... both the impellers and the jet should operate at as high a voltage as you can afford to save downconverter mass....

And of course once you run out of air you switch modes to microwave electrothermal thruster...

.... still say it'll be simpler and cheaper to use polywell to build an SSTO that hauls your ass to orbit in 10 minutes and leave the mucking about in atmosphere to craft specialized for that purpose... :)

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Postby WizWom » Tue Jul 20, 2010 2:05 pm

As an engineer, of course the obvious thing to do is BUILD the thing, and test it. Especially if its something as simple as an elliptical arcjet.
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DeltaV
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Postby DeltaV » Wed Jul 21, 2010 2:49 am


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Postby kunkmiester » Wed Jul 21, 2010 6:21 am

You could also just build something so freaking big the mass penalty for down conversion is negligible. :twisted: :roll:

Anyone ever build a DC motor to run at a million volts? What would be the mass penalty of that sort of thing?
Evil is evil, no matter how small

DeltaV
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Postby DeltaV » Wed Jul 21, 2010 6:31 am

It has to fit in my backyard, or there's no point.

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Postby GIThruster » Tue Jul 27, 2010 2:57 am

"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

DeltaV
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Postby DeltaV » Tue Jul 27, 2010 3:24 am



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