[ RadSafe ] Fission, fusion; Spacejet

[Brennan, Mike (DOH)]

Hi, Joseph.

The problem with using reactors to power a launch from the ground is not
power, but power density (basically how much power you can get from a
given volume or mass of power plant, including everything that is needed
to make the plant work.)  Reactors are pretty good at producing a lot of
power for a long period of time, but not so good at producing a HUGE
amount of power over a short period of time (NOTE: I know that I am not
using the exactly correct terms, but any unit-purists out there, please
cut me some slack).  

If you absolutely MUST use nuclear energy to launch from Earth's
surface, there are two schemes I am aware of.  One uses lasers from
ground stations to propel a craft into orbit (the materials to use on
the craft that will allow the light to impart that much momentum without
the material burning through is, as yet, left as an exercise for the
reader).  The other it Project Orion,
http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion), which
has its own set of technical issues.  I, personally, like the suggestion
one person had that someone do the Environmental Impact Statement for
launching an Orion ship, then stack all the paper in the statement, and
just climb the pile into low earth orbit. 
 

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of
JPreisig at aol.com
Sent: Friday, August 26, 2011 6:41 AM
To: radsafe at health.phys.iit.edu
Subject: [ RadSafe ] Fission, fusion; Spacejet

Hello Radsafe:
 
      From:     _jpreisig at aol.com_ (mailto:jpreisig at aol.com)    .
 
 
      Hope you all are well.
 
      Google on  jet AND mach 10
 
                  or perhaps  spacejet AND mach 10   and perhaps you
will 
read  about the US
      spacejet/spaceplane which just achieved Mach  10 velocities after 
being dropped from a
      large airplane.  So, it was not a  launch from the ground and was 
chemically propelled
      (ramjet system???).
 
              Too bad fusion isn't working already.  One could envision
a 
hot (or perhaps  warm)
      fusion system which is very controllable in  energy.  Just make
more 
fusions (D, T etc.)
      and make more energy for liftoff from the  ground.  And perhaps,
if 
liftoff from the ground isn't
      presently possible, then one could have a  chemically propelled
and 
fission propelled hybrid
      rocket/spaceship for going to Mars or  wherever.  Drop the
spacecraft 
from a large airplane in
      the Earth's high atmosphere and let the  spacecraft leave the
Earth 
behind under its own power???
 
      As for a fission/chemical hybrid spaceship,  maybe this is
possible 
also.  Drop it from a large airplane 
     also???  I need to invoke what Tim Allen  might say here again for 
this situation: the fission
     spaceship needs more power!!!!!   Why  bother having one fission 
reactor on board when one
     could have 4-10 reactors using highly enriched  fuel and/or high 
energy neutron fission.  Six 
     reactors could be used to assist in the launch or  propulsion of
the 
spacecraft out of Earth
     orbit.  The other four reactors could be used  to supply power for
the 
rest of the mission
 
     For launch or Earth orbit escape purposes,  how do you squeeze a
great 
deal of energy out of
     a reactor over a short time period???  I  don't specifically know
the 
answer....Clearly having
     the control rods pulled out of a reactor will  allow the reactor to

provide much energy/power.
 
     Perhaps a new type of reactor is needed.   Have a reactor with the 
usual core containment
     and control rods.  But perhaps have uranium  spheres(???) suspended
in 
water which travel
     around the reactor core in pipes.  Thus you  would have cooling
water 
circulating through the 
     reactor core as usual.   And then also  have a uranium fuel 
circulation system???
     Maybe not... I don't think you can get much  of the energy from 
uranium 235 out all that
     quickly.  Too bad.  Fusion seems to work  better (if it ever
works???) 
in this space travel
     application.  Still, multiple fission  reactors working with
enriched 
uranium and/or fast
     fission neutrons might be one way to go...
 
         Fundamentally,  fission/fusion energy sources should provide
about 
a factor of about 1000
     (barring efficiency adjustments) improvement over  chemical
propulsion 
systems.
     Yet, one can have considerable burning of chemical  fuel in a short

time for launching space
     vehicles.  Such short time capabilty might be  had with fusion
energy 
power systems also.
     Perhaps this is a downside for fission energy  systems.  The factor
of 
1000 is without including
     uranium enrichment and/or fast neutron fission  factors --- factor
of 
1000 is in energy, not
     velocity.
 
          Some of these here  radsafe list e-mail postings are now
showing 
up, translated into
      Russian --- I saw some Russian radsafe  postings (via websearch)
the 
other day.
 
          On an unrelated  topic, the USGS (US Geological Survey) had a 
website news item
      which suggested some human cancers are due  to parasites picked up
in 
the
      environment.  Wonder  how true  this is ???
 
           Wonder what  the US spacejet will do next???
 
           Have a good  weekend!!!!
 
 
 
                   Regards,    Joseph R. (Joe) Preisig, PhD
 
 
 
 
 
 
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