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

[JPreisig at aol.com]

Dear Radsafe:

     This is from:  jpreisig at aol.com     .


     Hello Radsafe:


          If a fission-propelled spaceship cannot escape the Earth's gravity 
on
its own, then perhaps such a spaceship could be launched <initially> into
space with a chemically propelled rocket <old, dependable, familiar>.
The fission-propelled spaceship might be launched into space with one
rocket, or it might be launched into space in several pieces, and assembled
together in space.  Assembly crews could be housed in a space station,
which the USA and Russians have already had in space.  Once the fission-
spacecraft is in space, it could use various chemically driven <smaller>
spaceships to get to the Earth or to other planet surfaces.  The 
fission-spacecraft
could be left in space for a long time, if necessary.

      Apparently NASA-USA is working on a new rocket launch system which is
expected to be ready in the next 5 to 7 years.  The mission objectives are
eventual trips to the Moon and/or Mars.  So, indeed, astronaut flight crews
may eventually be spending up to three years in space.  Oh my.

     A fission reactor for the fission-propelled spaceship could be designed 
using
MCNP, MCNPXX or whatever computer codes are available for this purpose.
There is some self-shielding in the reactor due to water or whatever other 
fluid
<and reactor solid parts> is used to moderate the neutrons.  Fission neutrons
are pretty much knocked down to thermal neutron energies <approximately>
by a twelve inch Bonner <spectrometer> sphere, so I don't think neutrons are
too bad of a radiation problem for such a spaceship.

     Gamma radiation from the reactor is a whole another issue.  As the 
reactor
is turned on, there will be growth of the gamma generating radioisotopes
during any space trip, with not much decay-off during the trip.  Gamma 
shielding needs to be well planned, in accordance with the length of the
mission<s>.  One can place the reactor at some distance from most of the 
crew, but some astronauts/crew members will have to deal with the reactor in
close proximity.  Guess everyone will have to assume their fair share of
the doses.

     Geez, a central reactor with the crew placed radially at some distance 
from the reactor.  Wonder what that would look like???

     The notion of a saucer shaped spaceship springs from mechanical
stabilty considerations.  That's classical mechanics <i.e. physics> ---
see books by Kleppner and Kolenkow and or Jerry Marion.  A cylindrical
shaped spacecraft is not mechanically stable.  The saucer shape allows the 
crew 
to normally be at some distance from the reactor.  Time, distance and 
shielding, don't you know....

     The spaceship will probably have to carry some water, or whatever fluid,
which will be used for cooling and/or propulsion associated with the reactor.
By the way, how does one cool a reactor in space???  I guess I have my own
ideas about cooling a fission reactor in space.  Space is very cold, no????
Some water in the reactor is necessary for neutron moderation.
Some other water may be fed into the reactor <in a separate water loop>,
heated in the reactor and eventually be forced out of the reactor, exiting 
the 
spacecraft to propel the spacecraft.  Relatively clean water exits the 
spacecraft
as propellant.  Clearly other spacecraft drive mechanisms are possible.

     So, that's all for now.  I've NEVER read any Heinlin/Heinlein.....

     The <Asian> Indians are starting to launch rockets into space now.
Very interesting.

     I hope you all are having a great day and/or week.  And if you have the 
notion that someone is paying me right now to work on this stuff, that notion
is not correct.  See you <ALL????> on OUR spacecraft....

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



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