What is the fastest theoretical speed possible for a maned spacecraft

Question

I was reading how pioneer 10 accelerated to 132,000km/h using the gravity pull of jupiter , i wanted to know using current technology and techniques what sort of speeds could be achieved by a maned craft

Answer 1

If you could use repeated sling shots to accelerate the craft then any speed up to c. It ain't the speed that'll kill ya but the acceleration so if the gravitational assist was performed so as the keep the G's on the craft and occupants below about 6 (I think it's above that that fighter pilots pass out due to the blood exiting the brain). and could repeat the process over and over then very high speeds could be achieved. So to give a value from the question if a man was inside pioneer 10 with life support he'd be alive.

Answer 2

What we can do and what is allowed are two different things.

If we really wanted, we could propel a city sized ship up to 10% of the speed of light, however we would do it with nuclear fission propulsion. Unfortunately nuclear detonations in space are banned, and launching large amounts of fissile material is seen as risky in the case of a failed launch.

It really is a bit of a shame, have a read about the Project Orion:

http://en.wikipedia.org/wiki/Project_Ori...

For chemical rockets, the fuel and propellant is such a huge mass that just a tiny fraction of the rocket is actual payload. To get to any sort of decent velocity, even 0.1% of c, would require a simply vast amount of fuel and would still take 4365 years to get to our closest star.

We won't be going anywhere fast with chemical rockets, the only way to get anywhere now is with fusion powered rockets, or perhaps a fission powered rocket lauched from the moon.

Answer 3

150,000 mph so far for unmanned... Although this is relative as is all "speed" in space...

Answer 4

0.999999999c give or take a few 9's.

Answer 5

Of course the theoretical limit is the speed of light, c, or 186,000 miles per second (300,000,000 m/s). However the practical limit is set by the amount of reaction mass needed.

There is a troublesome relationship between the amount of reaction mas needed at launch to the payload. This is known as the mass ratio. For a given final speed, the equation is:

V = Ve ln(M/m)

where Ve is the exhaust velocity and M/m is the mass ratio. For the space shuttle, Ve = about 4400m/s. So to get up to 1/10 of the speed of light (where relativist effects would still be negligible, you would need a mass ratio of e^(30,000,000/4400) or about 1.25 x 10^2961. You would need that much more reaction mass in your rocket than the payload of the man and his capsule and the motor. You could improve the situation by having a higher exhust velocity, but it needs a h**l of a lot of improving!

Conclusion, Interstellar travel is impractical with current technology.

Answer 6

In terms of straight line speed I can't think of any reason for there to be a limit of any kind, assuming they are flying in a complete vacuum with no resistance at all (which is supposedly what space is). The issue is how to achieve that speed. If you are using gravitational pull to accelerate the spacecraft, the astronauts would die at something like 8G give or take a G or 2.

Using some other kind of propulsion, it would be limited only by the power unit as far as I can see.