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From: kpmancus@phoenix.Princeton.EDU (Keith P. Mancus)
Newsgroups: sci.space
Subject: Building a fusion-based rocket
Message-ID: <7473@phoenix.Princeton.EDU>
Date: 29 Mar 89 22:12:13 GMT
Reply-To: kpmancus@phoenix.Princeton.EDU (Keith P. Mancus)
Organization: Princeton University, NJ
Lines: 53


	I've been trying to figure out how to get a "heat-pump" effect
to use the fusion system to pump up a heat exchanger to a reasonable
temperature.  That is, assume that our fusion source will remain at
the boiling point of water regardless of what mass flow of coolant
we pass through it.  What coolant should we choose to allow a
production of temperature of ~3000 K on the other end?

	To see this more clearly, see the following picture.

	|----------|	->	   ------		->	  -----------
	|		   ------------| 2  |-------------|			|
	|		   ------------|	|-------------|			|
	|		   |		   ------			  |			|
	|	1	   |							  |		3	|
	|		   |			  ------		  |			|
	|		   |--------------|    |----------|			|
	|		   |--------------| 4  |----------|			|
	|----------|			  ------		  -----------


	1>  This is the fusion reactor.  Presumably it uses liquid D2O
		at very high temperature.  Ideally it should run at 650 C
		or so, and very high pressure.  It vaporizes the working fluid.

	2>	This compressor compresses the working fluid (presumably a
		metal or mixture of metals -- NaK perhaps?) to much higher
		pressure.  In doing so it also raises the temperature.

	3>	This is the combustion chamber.  The working fluid, at high
		(preferably > 2000 C) temperature, goes through a heat exchanger
		which heats reaction mass (probably but not necessarily H2)
		and lets it flow through a standard rocket nozzle.

	4>	The working fluid is now liquid again.  It flows through a
		nozzle at (4) which drops it back to low pressure.  It
		then reenters (1) as a low pressure liquid again.

	This is basically a heat pump cycle, but at high temperatures.  We
certainly can't use water or Freon as the working fluid!  I haven't
worked out yet just how much of the energy producing the high temperature
at (3) comes from the heat at (1) and how much comes from the electrical
energy put in the compressor at (2).  We assume that a second cycle
operates between (1) and a low temperature radiator to produce the
electrical energy (through a turbine generator).
	Still in the thinking stage....



-- 
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-Keith Mancus <kpmancus@phoenix.princeton.edu>  <- preferred
              <kpmancus@pucc.BITNET>