the point about it being impossible is that an object needs to be moving at 17,000 mph to be able to leave the gravitaional pull. be it the shuttle, 747 or a brick. once in space a jet could conceivably operate in space if chemical propellant were put through the engines midway. however the rudder and aerilions would not control where the thing is going!
Here's an interesting fact about space, which has very little to do with your question, but I'm going to say it anyway.
What scientists refer to as "space" is only just over 60 miles away (under 100km), so travelling at 60mh straight upwards in my Peugeot 106, it would only take about an hour to reach space!
caladon- the only way a jet would work in space is if you turned it into a rocket. whilst conceivably possible this would be monstrously inefficient, as the forward motion is normally generated by hydraulic damming acting as a cushion for the jet to push against. turning the jet into a rocket chamber you would only have the compressor vanes to push against, which would lose you about half your power.
yes, the whole fusealage would need to contain fuel, but it is conceivably possible, thats my point....
and indiesinger, don't get caught by speed cameras on your way up!
Thanks darth vader I tried again earlier - with the windows up - but it started getting a bit hot, so I will try again at night when the sun disappears.