Genetically engineered space voyagers?

Listening to the History Channel's excellent series The Universe, they emphasized that low gravity and radiation can conspire to produce deadly effects to humans. The immune system doesn't seem to work as well in low gravity. Virulent organisms seem to be more deadly in space and in places like the space station.

To begin with, the radiation may increase the rate of mutation, both in human cellular and immune system function and in the rate and type of virus formation, producing deadlier strains. (In fact, I'm mildly surprised that returning space station astronauts haven't brought back deadlier virus.)

These problems and others may show that normal humans just do not have the make up and temperament to survive more than short voyages, possibly to the Moon and back. We may end up relegated to mainly to low Earth orbit.

We've already seen the effects of Soviet experiments at long duration isolation in mock-space station environments here on Earth. Most last a few months then the mini-society breaks down.

It may be necessary to create a new type of human that is resistant to viruses and bacteria and radiation and the effects of low gravity and long periods of isolation in a small space if we want to become space faring.

The only way around this may be to stumble upon some kind of advanced technology which will jump the gap from chemical rockets and ion drives to a new type of propulsion.

Only then will space travel become feasible for normal humans, I believe.