The problem with all space travel is fuel. As The
Hitchhiker's Guide to the Galaxy says, "space is big," and
trying to cover any sort of distance in a reasonable time is hampered
by the fact that you have to drag along a heck of a lot of fuel; then
you have to carry fuel to accelerate the fuel, and fuel to accelerate
the fuel to accelerate the fuel, and the next thing you know you've
got the planet Jupiter in tow.
Enter the Great White Hope of interstellar travel:
the Bussard fusion ramjet. This was first proposed in a
1960 paper by Robert W. Bussard and popularised by
Carl Sagan in the Cosmos television series (1980).
The idea behind the Bussard
ramjet is simple enough. As it travels, the spaceship uses a
gigantic magnetic scoop to collect hydrogen atoms. These are fed
into a fusion reactor, which converts the hydrogen into energy and
propels the ship. Since it gathers fuel as it goes along, the
ship doesn't need any fuel payload and it can keep accelerating
indefinitely until it reaches velocities close to the speed of light.
At such speeds, time slows down for the crew dramatically and it would
be theoretically possible for the ship to reach the centre of the
Galaxy in 20 years (crew time, though it still takes 30,000 years in
real time) and could even circumnavigate the universe within the
crew's lifetime.
That's in theory. In
practice, all is not so rosy in the garden. First there is the
obvious problem that even for a small ship you are talking about
handling energy in quantities that scientists refer to in technical
terms as "bat guano crazy." Then there is the fact that the ship
must be travelling at 6% of the speed of light to even begin working;
and that sort of speed is already in the "What the Hell?" range.
Worst of all, there are all sorts of efficiency problems that start to
get in the way. Only 1% of the hydrogen atoms collected
would be of an isotope useable as fuel. That's a lot of chaff for very little
seed, so acceleration may not get much more than 1/1000th
of a gravity. Then there is the size of the magnetic scoop, which
needs to be upwards of 50,000 kilometers in diameter to collect the
needed fuel and even in the vacuum of interstellar space that can
produce drag like trying to go swimming underwater while pushing a washtub in
front of you. This has lead to some calculations that the ramjet
might not be able to go faster than 16% of the speed of light.
Fast, but warp speed, it ain't.
Of course, all this is a moot
point, as the fusion engine at the heart of the ship hasn't even got
to the back of the envelope stage of development and if it ever does
prove worth building we're talking engineering on a planetary scale.
So, if you were planning on booking passage, I suggest that you opt
for the Queen Mary 2 instead. Regular service already started
and a superb buffet. |
