The propulsion system from Earth to Mars could just be a scaled-up version of the systems we've been using to send probes to Mars for decades.
Yes, it would be wisest to send at least two trips, so that equipment can be ready for the crew when they arrive. (Especially if you're making return-trip fuel from local resources.)
Radiation is a problem for a manned mission to Mars, but I understand the numbers work out to less lifetime risk of cancer than smoking. (So send former smokers without any cigs and you've improved their expected lifespan.)
> The propulsion system from Earth to Mars could just be a scaled-up version of the systems we've been using to send probes to Mars for decades.
You would have to send a Mir-sized object (in order to accommodate humans on their way up) on a transfer orbit to Mars, with the required shielding and supplies to keep the crew alive for at least 6 months, plus fuel for braking when they need to inject themselves into Martian orbit (or, at least, to circularize the orbit after atmospheric braking). Doing this with chemical rockets is possible, but operational NTRs would decrease the time for the trip and expose the crew to less radiation.
I am not sure the numbers for radiological risk are that low. Besides, the longer they stay en-route, the higher the risk from a CME catching them. If they are on Mars, at least they have a planet to shield them 50% of the time.
Yes, it would be wisest to send at least two trips, so that equipment can be ready for the crew when they arrive. (Especially if you're making return-trip fuel from local resources.)
Radiation is a problem for a manned mission to Mars, but I understand the numbers work out to less lifetime risk of cancer than smoking. (So send former smokers without any cigs and you've improved their expected lifespan.)
Take a look at http://en.wikipedia.org/wiki/Mars_Direct and its descendants. Many of the problems have been solved, with an expected 10-year timeline.