[ RadSafe ] [RadSafe]Mission to Mars---Fission Propulsion

[JPreisig at aol.com]

Dear Radsafe:

     This is from:   jpreisig at aol.com   .


     Radsafers <Happy 2009>,

          Thanks to Jerry Lahti for discussing NERVA and publication 
    NASA-TM X-2440.  Maybe someday I'll get my hands on this document.
    Project cancelled in 1972???  Too bad --- I know there are University
    research projects still focussed on fission/fusion space propulsion at
    Michigan, Princeton, etc.  I'm sure NASA, etc. is still making progress
    in this area, even if it is not being too vocal about it.  Tactical flight
    velocity advantages over the Soviets, etc. are still a consideration in 
all
    this.  Perhaps Jane's Aeronautical publications out of Great Britain would
    be helpful????

         Yes, shielding of a spaceship space crew and reactor would be
    necessary for space flight.  And of course some shielding for solar 
flares,
    cosmic rays, etc. for the spacecraft would be necessary also.
     The American Geophysical Union <not really a trade union, but rather
     a scientific society like the HPS> has publications and AGU Meetings
     which have sections dedicated to solar flares, ionosphere, etc. for 
those 
     with interest in those things.  Membership is something like 20 dollars
     per year in the USA which includes subscriptions to Physics Today and
     EOS, a weekly AGU newsletter.  See their website.  Other AGU publications
     cost extra.

           As for "gamma modelling from large sources", another topic on
     Radsafe, sure take your best shot at making an analytical or numerical
     calculation, first.  Make measurements also.  Then do yourself a big 
favor,
     buy a copy of MCNP from Oak Ridge or Los Alamos, and set up the
     problem on MCNP.  A good analyst can probably set up the basic geometry
     in one day.  With today's PC's one can probably set up an overnight MCNP
     run which will give excellent statistics by the next morning.  Then 
modify
     the problem's detector positions as needed, and run MCNP again.
     Compare ALL results --- modelling CAN BE DONE on such a problem
      readily!!!!

           Neutron problems??? --- Use MCNP also.  Use calibration equations
      given in the papers by Eisenhauer and Schwartz <USA> and Hunt
      <Great Britain>.  If necessary, make measurements using Bonner Spheres
      and activation detectors --- see Patterson and Thomas's book for
      background on all this.  Analyze the neutron data using BON4/BON5 or
      whatever unfolding code for neutron data you have.  BON4/BON5 is
      available from Oak Ridge <RSICC --- Radiation Shielding Information 
Center>.
      A PC version of BON4/BON5 might be available from H. Kahnhauser
      <a manager> at Brookhaven Lab.   I've discussed the problems with
      BON4/BON5 and its data graphics in the Radsafe archives.  When in
      doubt with BON4/BON5, plot the flux density/fluence data by hand on
      graph paper.  You'll see nice neutron cascade, evaporation neutron peaks
      and thermal neutron peaks in your BON results, just like the
      big USA national laboratories get.  Neutron data normalization should be
      properly done with respect to an array of all <7 or whatever?> Bonner
      detectors --- data normalization with respect to only one detector is 
not
      good enough.  The factors "C or c" in the Bonner unfolding equation, 
      referred to in Patterson and Thomas's book are calibration factors and 
these
      can be found empirically or by another less empirical way.  My goodness,
      I'm not going to tell you all in one e-mail how to do all this to the
      one percent Percent Average Error level in BON4/BON5.  Kahnhauser has
      my Bonner Multisphere Spectrometer procedure at Brookhaven.  Who he
      chooses to share such a document with is D.O.E.'s <USA> business.

            Sorry, I've started to go off on all this a bit.  LOUHI, BUNKI, 
etc. are 
      all probably pretty good neutron unfolding etc. codes.


             Some USA business-man is financing his own spacecraft flight
      effort.

             Have a good week at work.


             Regards,     Joseph R. <Joe> Preisig, Ph.D.


P.S.      To the guy in Paris, the lone geoscientist on Radsafe????, my MA and
             Ph.D are in geophysics.  I'm sure there are other geoscientists
             on Radsafe also!!!  Do not feel so alone!!!!


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