Originally Posted By: paul
manned interstellar travel

Paul, I was referring to this comment:

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

That is, as I pointed out, silly. Even with 1960's tech we could send stuff to other stars - it just takes an eternity to get there. No need for any magical free energy, just chemical rockets, gravity and time.

I'd also point out that you've never defined what you mean by "free energy". I have a hunch, but I don't want to put words into your mouth.

Originally Posted By: paul
and how fast can you accelerate the ship , that is manned?

3-5G's is sustainable for modest periods of time, 1G for eternity.

At 1G acceleration you get to the authors asked for 4.4%C in just shy of 16 days.

Originally Posted By: paul
how many generations will pass before the ship approaches the deceleration point?

Depends on your speed of travel. At a fast enough speed, anywhere is reachable in a human's life-time, as measured by ship-time. Acceleration to near-C, at a constant 1G, takes about 1 year.

Originally Posted By: paul
what new magical propulsion do we now use that was not used then that would get us there faster?

We've had working ion engines for over a decade, and vasimr has been demonstrated. Both of those are far more fuel efficient, and enjoy ISPs thousands of times better, than chemical rockets. Heck, Orion was considered possible with 60's tech - and was developed to the point of experimental models flown on conventional explosives.

And I'd point out that this thread was never about today's tech, but rather the orion system and potential alternatives. There is no reason an orion drive couldn't reach 4.4% c, all using conventional fissile materials. You'd need a lot of it, but you could get there.

Originally Posted By: paul
dont forget if your going to use nuclear power to do the job... how much fuel will you need?

Fusion, fission or RTG's?. The answer varies wildly, depending on which one, and what fuel. And what drive you're using, how fast you're flying, how big your ship is, how far you're going, etc.

Originally Posted By: paul
do we have that much fuel?


Originally Posted By: paul
so one false move and its lights out.
do we already have a nuclear power station in space?

Several RTG's.

Originally Posted By: paul
just what would you use to power such a short lived journey if you dont use free energy?

What free energy?

Originally Posted By: paul
just suppose your distant future family members are still living and actually have succeded in keeping there muscle and bone structure in tact , what would the effects of slowing the spacecraft down have on them , as for the last 30 or 40 generations in your family have never experienced any deceleration on their bodies.

What keeps you from generating centripetal force? Centripetal force = "artificial gravity" for all eternity when you're spinning in a vacuum.

Originally Posted By: paul
will they never get a cold or a virus in the thousands of years that would wipe them all out?

Almost guaranteed to be zero. Pathogens evolve in very well understood fashions, usually requiring passage between several separate populations or even multiple species. A small isolated population is not one which'll breed new pathogens. Small isolated populations make good victims of existing diseases, but poor incubators for making new ones.

Originally Posted By: paul
what would be the odds that any of them would survive the first year?

Depends on how well things are built, etc.

Originally Posted By: paul

now or course there are no supply shipps trailing them or manufacturing ships or farm ships.

Why not? If you can launch 1 frigging huge ship into space, there is no reason you cannot launch more.

Originally Posted By: paul
so your going to have to make everything that might break down as you travel...this includes every manufacturing process on earth.

Not really. You only need those manufacturing processes required to replace ship-board items. No need for 747 manufacturing on the ship. By standardizing parts as much as possible, manufacturing capacity can be minimized.

And you forget the possibility of self-replicating prototypers (simple version of which have been demonstrated several times in the 2000's). These devices produce any parts needed, and assemble them - including what is required to replicate themselves. All you need is energy and raw material.