Originally Posted by **********

That's exactly right. A long trip would expose travellers to lots of radiation. The ship would have to be huge to carry supplies just to keep people alive for the trip, and the crew would have to be very carefully picked to make sure no one went nuts on the way there.

The ship would also have to bring enough supplies to keep the crew alive on Mars once they got there, plus supplies to build a habitat.

Of course if a probe could find water, everything would change. If they found water, it would reduce the need to bring so much water with them. Water could be used to drink, help plants grow, and be converted to fuel. Everything is feasible, just extremely expensive.