Engineers based their design on the Mercury capsule, but made it larger so that two astronauts could travel together.

The astronauts are travelling at relativistic velocities, so that the journey only takes 1.5 years from their perspective.

Then the astronauts lay down tube II rather than travelling back in tube I, the first tube they produced.

Exy had sailed more miles than an astronaut would travel to the moon.

In effect the astronaut would have traveled into the future, said Dr. J. Richard Gott, a Princeton astrophysicist.

How would astronauts travel these distances?

However, surviving astronaut Brent (James Franciscus) believes he has traveled to another planet.

The Atlantis would have maneuvered so that its cargo bay faced the Columbia's, and astronauts would have traveled from one to the other.

But since then, only five other British-born astronauts have travelled into outer space - and all of them have had to switch their nationality to become American citizens.

Then the astronauts would travel for ever.