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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Using atmosphere as propellant

Postby DeltaV » Fri Jun 11, 2010 7:31 am


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Re: Using atmosphere as propellant

Postby zapkitty » Fri Jun 11, 2010 1:06 pm


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Re: Using atmosphere as propellant

Postby Stoney3K » Fri Jun 11, 2010 1:42 pm

Because we can.

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Slightly OT: Skylon's Sabre engines.

Postby Nik » Fri Jun 11, 2010 3:09 pm


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Postby WizWom » Fri Jun 11, 2010 6:19 pm

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Re: Using atmosphere as propellant

Postby DeltaV » Fri Jun 11, 2010 6:46 pm


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Postby Stoney3K » Fri Jun 11, 2010 6:51 pm

Because we can.

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Postby DeltaV » Fri Jun 11, 2010 7:04 pm


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Postby DeltaV » Fri Jun 11, 2010 7:11 pm


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Postby WizWom » Fri Jun 11, 2010 7:12 pm

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Postby DeltaV » Fri Jun 11, 2010 7:21 pm


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Postby Stoney3K » Fri Jun 11, 2010 7:28 pm

Because we can.

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Postby DeltaV » Fri Jun 11, 2010 7:55 pm


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Postby Stoney3K » Fri Jun 11, 2010 8:12 pm

Because we can.

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Postby D Tibbets » Fri Jun 11, 2010 9:26 pm

Decellerating from oprbit requires either atmospheric drag/ friction or ejection of a gas. The helium produced from a Polywell could provide very efficient thrust, but the power would be tiny. If you accelerate or eject the helium through nozzels, even at 100,000 ISP,you would only have perhaps 10^ 23helium nuclei per second* (~10 GW). That would be ~ 1 mole or 4 grams of helium per second. 4 grams * 100,000 ISP= ~400 Kg of thrust. Not enough to make a significant difference on a re-entry thermal load, and way to little to counteract gravity after you decellerated more than a tiny amount below orbital velocity. Once into the dense atmosphere (and subsonic?) electric fans might provide enough thrust to hover.
So you need a stored working fluid to provide de-orbiting thrust if you want to avoid the problems of atmospheric friction. If a mixed fusion product can provide enough thrust at say 5,000 ISP, then you may be able to budget for the on board fuel (working fluid) to avoid re-entry heating.

*Actual numbers would probably be closer to 1/10th of this.

Dan Tibbets
To error is human... and I'm very human.


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