I don't think there is much value in trying to use the moon as a base to go to Mars. That's going into one gravity belt and having to get back out of it again. And the moon doesn't have a lot to offer as a resource base.

We do need different types of propulsion to get to Mars. I wrote one of the first Ph.D. theses on that in the 1960s.

I want to get to the moon. I want to go to Mars.

Buzz Aldrin doesn't think we need to go back to the Moon - that we should go straight on to Mars. I'm more on the side that says we should go back to the Moon. I think there's a lot we can utilise the Moon for scientifically.

I'm going to go out there and just keep trying to get better.

But I don't think we'll go there until we go back to the moon and develop a technology base for living and working and transporting ourselves through space.