QUESTION:
We are constructing a Mars Habitat.  We have to heat the homes on Mars.  We
were wondering, instead of using a nuclear reactor to make electricity (as
nuclear reactors usually are used for), could we use the heat it makes to
boil water into steam and then pump the steam to the houses on Mars?  And,
would it be possible to transport a nuclear reactor to Mars on a spacecraft?

The ANSWER comes from Steve Wall on June 26, 1997:
Good thinking! It is actually much more efficient to use water to transfer
the heat than it is to use electricity.  In fact, using electricity to heat
things is pretty wasteful most of the time, and even nuclear reactors
usually boil water and turn that into electricity in some way.  So your way
is much more direct - and the more directly you change energy from the form
it starts out in to the form you need it in, the less you waste.

It is possible to transport some types of nuclear reactors to Mars - in
fact, the Viking landers we sent to Mars in the 1970's used nuclear heat
generators called Radioisotope Thermoelectric Generators, or RTG's, to power
them.  These RTG's don't boil water, but they do create heat directly.  Look
at these addresses for more information:

http://www.jpl.nasa.gov/galileo/messenger/oldmess/2RTG1.html
http://starfire.ne.uiuc.edu/~space/

Ask your school librarian or your teacher for help if you need it.

There are some dangers in launching nuclear materials into space, though,
and if you are planning a large habitat you need to think about what might
happen if something goes wrong when you launch.  If the launch fails, you
don't want to spread large amounts of nuclear materials into the ocean or
onto land, because they are dangerous.