Originally Posted By: paul
My question is, if it is possible at all to reach the nearest Stars without referring to unproven hypothesis and technologies which probably will never be developed.
(Like FTL, "free Energy").

no , its not possible.

without using free energy theres no space travel to other stars.

Sorry, the above is just silly. Unmanned travel to other star systems is well within current technology, so long as you're not in a rush to get there. In fact, several human probes are already traveling faster than escape velocity and will (in thousands of years) pass other stars. No need for exotic energy sources, just 1960's rocket propulsion and the odd gravitation sling was all that was needed.

As for human travel, the generation ship idea's been around for a long time - out of our current technological capabilities, but is capable of moving a human colony using a Hohmann (minimal energy) transfer orbits that are well within the energy levels that could be provided by an orion drive, fusion drive, VASIMR, etc. Several other projects have been designed, but never implemented, that could potentially send humans to nearby stars within a human lifetime (Project Longshot and Daedalus, for example). These were based on existent tech, or tech expected to be developed in the near-term.

And people seem to forget, you can leave a significant portion of your "propulsion" at home - laser-powered solar sails are near tech that could "easily" get a space craft over the 1%C mark. Doesn't reduce the amount of energy needed to slow down on the other end (nor return, if that is your goal), but it does cut down on fuel use dramatically. It even makes a "fly buy" mission "fuel free" (ignoring reactors and steering).

BTW, what do you mean by "free energy"?


EDIT: by "laser powered solar sails" I'm referring to where you have a solar-sail powered craft, and use orbital lasers to provide propulsion above what the sun provides. Because they lasers stay in earth orbit, the fuel needed to run them stays "at home" and need not be carried.

Edited by ImagingGeek (05/19/10 07:54 PM)