CHANG-DIAZ: Well, rockets today are powered by chemistry.
The way it works is that the fuel that you carry on board
actually burns,
actually explodes inside this rocket motor,
and you get a lot of exhaust which is very hot.
That's how the rocket works.
In the rockets that we're developing today,
we use electricity instead of the chemistry of these fuels,
and the electricity comes from a solar panel, a solar collector.
At least when we're near the Earth
and, therefore, near the sun, in a way,
we have plenty of sun to do this job.
The electricity is used to heat the plasma,
and we pretty much heat the plasma
the same way you heat your coffee in your microwave oven.
You just put it in there, and these electromagnetic waves --
microwaves, which we call in an oven --
come in and make the plasma really hot.
And, of course, in a microwave oven,
you don't want to make it too hot.
But in the case of the plasma rocket,
we make it up to millions of degrees.
What happens is that, when you go really far away from the sun,
then the solar panels tend to get really big.
In fact, it gets to the point where the sun is too far away,
and you cannot really use solar power.
At that point, we need another power source
which will be a nuclear reactor,
and this is a very important thing that we have to realize,
that if we really want to explore deep in space,
we need to develop nuclear-electric power plants
to carry us far and deep into the solar system.
The sun will not be strong enough.
You know, when you are out to the orbit of Saturn
or Neptune or maybe even Pluto, the sun is just a bright star --
the brightest star in the sky,
but it's still not a source of power.
