  One
of the most feasible, yet controversial, methods of
powering spacecraft on long journeys is by using nuclear
energy. Our current chemical engines produce relatively
little power. They have to make use of planetary
alignments, or 'launch windows', to provide an extra
gravitational slingshot effect, helping to catapult them
further out into space. Nuclear rockets would be more
powerful and wouldn't need to take advantage of these
chance planetary patterns.
Types of nuclear rocket
There are two types of possible nuclear rocket,
utilising the different types of nuclear reactions:
fission, when atoms split apart; and fusion, when they
join together. Nuclear plants on
Earth produce energy from nuclear fission and the
technology needed to build a rocket powered by fission
is not far beyond our current means. In fact, they could
fly within the next ten years.
Fission-powered rockets
Rockets run by nuclear fission are more fuel efficient,
and so much lighter, than chemical rockets. This means
that, nuclear spaceships could travel twice as fast as
our current chemical spacecraft. A nuclear powered craft
could reach Saturn in as little
a three years, rather than the current journey time of
seven years. What's more, because the fuel lasts longer,
the spacecraft would still have enough energy left to
tour the Solar System for up to 15 years.
 Nuclear
waste
The main problem with fission engines is the controversy
over nuclear waste. The Earth's environment could be
protected by launching these spacecraft with
conventional chemical rockets. Only when the spaceship
was well away from the Earth would the nuclear reactors
fire up, ensuring that the radioactive waste wouldn't
find its way back home. However, the production of
radioactive waste would pose a problem for sending
manned missions on nuclear spacecraft rather than
robotic probes.
Fusion-powered rockets
Nuclear fusion produces even more energy and is the
process that occurs inside stars and thermonuclear
weapons. A propulsion system using nuclear fusion would
be 10 million times more powerful than chemical rockets
and would emit less radiation. There are many obstacles
involved in making fusion-powered rockets, however. In
experiments here on Earth, no one has been able to
create controlled fusion reactions that produce more
energy than they consume. In addition, the optimum fuel
for fusion reactions, Helium 3, is scarce on our planet
and the nearest plentiful source is the
Moon.
Many research projects are currently being conducted
worldwide, and so the mysteries of nuclear fusion may be
soon be solved, finally enabling us to send manned
missions into deep space. However, the best hope we have
of reaching the nearest star, Alpha Centauri, some 25
billion billion miles away, is in a spacecraft powered
by antimatter. |
