"To come out in plain words and say it, it isimpossible because if you carry enough fuel to thrustlong enough to travel at say nine tenths the speed oflight you could
never have enough fuel to stop. You would have to keep
traveling forever. "

That a really good reason, but there's one that's an
even bigger problem:
Space Isn't Empty.

IIRC, the density of the interplanetary medium is
about 1 atom of hydrogen per cubic meter. That's not
much in the way of resistance, but let's say the front
of the vehicle presents a face of 10 square meters.
That means every meter distance travelled it will, on
average, collide with 10 atoms of hydrogen. Now, let's
pretend that you get this machine to go only HALF the
speed of light. That means you will collide with
149,896,271 atoms of hydrogen every second.
You're dead. The kind of kinetic energy of 150 million
atoms slamming into your ship at 1/2 c EVERY SECOND
will eventuate in your ship becoming incredibly hot
and radioactive. And God ferbid you hit a grain of
sand at that speed - it would slice right through your
ship so fast - dead meat.

So: you're going to go all star trek on me and
postulate a huge "deflector array"? Where's the energy
going to come from for that? And besides, as you
approach C, your time dilation kicks in, so you have
some tiny fraction of time to deal with microscopic
bits of grit travelling at relativistic speed.

Deflecting it will require even MORE energy, and WHERE
is that going to come from? A small little lonesome
bit of crap is floating in space, minding it's own
dull business as it had for 4.6 billion years, when
suddenly Mr HotShot space truck comes blasting out of
nowhere saying "You have to get out of my way RIGHT
NOW" the energy required to do that would pretty much
not only vapourise the little piece of grit, which
would result in even MORE heat and radiation, on top
of all the other radiation. And if you're travelling
at say, 99% of c, you're looking at 300 million atoms
of hydrogen slamming into your machine at nearly light
speed - something it takes insane amounts of energy on
earth to do, just to get a few atoms in an
accellerator up to any appreciable speed.

Now multiply that energy by 300 million EVERY SECOND
and talk to me about some silly notion of a deflectorshield.
Quite simply, Mr Patterson is correct: It Just Ain't
Gonna Happen. Period. Not now, Not later, not ever.

HOWEVER: I do think that we can, and should, get out
of the gravity well. But I think a more likely way
than building ships that travel near c, would be to
evolve a special class of "humans" who have a genetic
code that is largely impervious to radiation (there
are bacteria that have this feature), eat rocks and
ice in the asteroid belt, have enourmous wing spans
that collect solar radiation and can live in a vacuum.
Once they eat the asteroid belt, they can grow bigger
wings and go work on the Kuiper Belt and then it's off
to the Oort cloud.Sound ridiculous? Yeah, It is. But it's one HELL of a
lot more achievable than travelling at c... That's
just a stupid hollywood fantasy.

Mister Studebaker