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39 days to Mars possible now with nuclear-powered VASIMR.



 
 
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  #1  
Old October 14th 15, 04:19 PM posted to sci.space.policy,sci.astro,sci.physics,rec.arts.sf.science
Thomas Koenig
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Posts: 47
Default 39 days to Mars possible now with nuclear-powered VASIMR.

Robert Clark schrieb:

Yes. You can reject more heat at higher temperatures. But for two systems
operating at the same temperature,


What does that mean?

A thermodynamic cycle does not operate at a single temperature
(unless it does nothing).

the one having lower waste heat, i.e.,
better efficiency, will require smaller radiators.

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  #2  
Old October 14th 15, 05:57 PM posted to sci.space.policy,sci.astro,sci.physics,rec.arts.sf.science
Thomas Koenig
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Posts: 47
Default 39 days to Mars possible now with nuclear-powered VASIMR.

Fred J McCall schrieb:
Thomas Koenig wrote:

Robert Clark schrieb:

Yes. You can reject more heat at higher temperatures. But for two systems
operating at the same temperature,


What does that mean?


Stephan-Boltzmann Law. Look it up.


You graciously snipped the second part of my post, so let me
explain a little bit more.

A thermodynamic cycle opertes between two distinct temperatures.
To say that a (power) system operates at a specific temperature
has no meaning.
  #3  
Old November 8th 15, 03:36 PM posted to sci.space.policy,sci.astro,sci.physics,rec.arts.sf.science
Thomas Koenig
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Posts: 47
Default 39 days to Mars possible now with nuclear-powered VASIMR.

Robert Clark schrieb:

Haven't taken it that far frankly. But a possibility might be the heat
exchangers planned for the Skylon:


These are a nice concept, but unfortunately will not work for you.

What you want to do is to use the exhaust stream, which travels at
supersonic velocity, and use that for coolig. This runs into the
problem of compressive heating (aka adiabatic temperature increase
upon compression) of the gas, and loss of specific impulse from
slowing down the

What they do is to slow down the incoming air, which also increases
the temperature up to rather high temperatures (~1350K), and
then use the liquid hydrogen to cool down the air to save work on
compression and increase efficiency. Nice concept (if ambitious).
 




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