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RE: More nuclear propulsion...



Years ago, Robert Heinlein, an author of speculative fiction with a surprising record of foresight/prediction, opined that the first practical application of fusion would be spacecraft.  In his analysis, he included transit times for continuous boost spacecraft, and Mars was about a week's travel time.
 
If I recall correctly, the analysis can be found in the book "Universe" and its updated re-release "Expanded Universe"
 
Dave Neil
-----Original Message-----
From: JPreisig@AOL.COM [mailto:JPreisig@AOL.COM]
Sent: Friday, February 07, 2003 11:21 PM
To: radsafe@list.vanderbilt.edu
Subject: More nuclear propulsion...

Hmmmmm,

      This is from:   jpreisig@aol.com    .

      Howdy Radsafe people...  Hope all is well in your neck of the woods.
      So, I guess we (the USA) are down to 3 (???) space shuttles.
      I guess it is time to build 3 to 5 new space shuttles, or whatever
      spacecraft NASA is proposing to build next.  I suppose we (the USA) can
      build these spacecraft over the next 5 or 10 years.  Let's use existing
      technology to improve the next set of spacecraft.  Existing shuttles are
      10 to 20 years old???  How many flights should a shuttle make, before it
      is retired from the fleet???

      Dr. Cohen is pretty correct.  Nuclear propelled spacecraft need never get
      close to Earth again, after they are launched the first time.  We could have
      spacecraft that bring materials up to the space station (or the moon???)
      and then have nuclear-powered spacecraft that go out into space
      from the space-station or moon.  Maybe someday we'll even do nuclear
      refueling at the space station.

            I'd prefer a nuclear propelled spacecraft based on fusion, but fission
      propelled spacecraft may have to do for now.  The US fusion community
      has just jumped back into the ITER fusion program, funding-wise, with
      a schedule lasting another 10-15 years.  I may be quite old before we see
      any commercial fusion energy.  The US is also continuing to fund
      existing fusion programs (NSTX at Princeton's Plasma Lab, etc. ---
      see their web-site).

           I guess some of my crude calculations (described on radsafe)
      resulted in nuclear propulsion-based one-way trip times to Mars of about
      one or two weeks.  So, in a total time of one month (trip to Mars), how
      much Cesium, Strontium (fission fragments, etc.) does one create by
      fissioning U-235 or Plutonium???  Not very much, I'll bet.  So much for
      any big hazard, if one doesn't run the reactor all that often, and if one
      refuels periodically.

           One big aspect of nuclear propulsion that is being somewhat ignored,
      is that nuclear propulsion gives one available energy (and power) to
      give improved (and more-controlled) flight (dynamics) performance.
      A spacecraft (with nuclear propulsion) re-entering the Earth atmosphere
      and experiencing difficulties might (with some warning) be able to go back
      into space, and perhaps wait for a rescue shuttle.

           Clearly, one might not get 1000 times more energy from nuclear
      propulsion (over chemical systems) but a factor of 5 to 100 might be nice.
      Maybe that is too much available energy, but nuclear propulsion
      systems will have energy (inefficiency) losses also.  I am very sorry to
      to hear of the recent lost shuttle.

           In other news, Brookhaven National Laboratory has a new director ---
     see their web-site for details.  A chemist (Ray Davis), formerly at
     Brookhaven, won the Nobel Prize (in Physics --- with several other people)
     for his work in cosmic ray research.  The people at RHIC (the Relativistic
     Heavy Ion Collider at Brookhaven) are now colliding deuterons with Gold.
     There is a link on BNL's Main Web-page to see how AGS/RHIC is
     running.  Some of the experiments at RHIC are PHENIX, STAR, BRAHMS,
     PHOBOS, etc.  The BNL web-pages have links to the web-sites of
     these experiments.  Browse at will???

           Have a good weekend....

                               Regards,             J.R. Preisig,   Ph.D.