This is dumb, dumb, dumb.
There is only one reason this is described as a "one-way" mission; Mankind's incredibly stupid reliance on chemical rockets. Chemical rockets *will not* allow us to explore any of outer space in a meaningful way, with the possible (and expensive) exception of near earth orbit.
We already have the technology to jet where-ever we want around the solar system. Project Orion.
There was a BBC show on it.
The short story: It was a design to use small nuclear explosives to push up against an abalative impact plate with shock absorbs. One pulse every 120 seconds. Significant levels of acceleration, and a mass to energy ratio that would make any rocket scientist blush. We could *easily* send a million ton spacecraft to Mars, with more than sufficient fuel to return several massive (10s of thousands of tons) spacecraft back to earth.
We could do round trips every 6 months without blinking an eye, with the added side effect of using much of the world's weapons grade nuclear fuel. Enhancements to the design switched from Fission to Fusion; at which point Orion spacecraft would be able to start to move around interstellar space. Early designs using current materials could achieve 0.05-0.1c . Designs using future materials (or possible relying upon non-solid ablative surfaces (this includes a plate that is sprayed with an oil solution before each blast)) could theoretically achieve .8c . This would make round-trips to Alpha Centauri possible.
How do you get around the nuclear radiation issues? Simple. First, there's no serious issue with radiation in space; build it in orbit, and there's not much to worry about. Second, the fallout/radiation from direct planetary launches would be dwarfed by weapons tests that occurred in the past, and probably by fossil fuel plant emissions, as well. The total fallout released from a planetary launch of a 6,000 ton vehicle would be equal to a 10-megaton nuclear blast (roughly one worldwide instance of cancer per launch), even using thermonuclear blasts. Further refinements to the technology could significantly reduce that; and mankind has pursued far less interesting pursuits that have caused a great deal more fallout (and heighted rates of cancer) than a real, "nuclear" space program.
In an ideal world, we'd build a few *huge* orion stations, and launch them into orbit. I'm talk multi-million ton hulks. The fallout from these launches would be significant, but would still be smaller in magnitude than the fallout from the various nuclear weapons tests that occurred during the cold war. These stations would contain the industrial complex needed to build additional ships, and smaller vessels capable of mining the needed materials from the moon. Hopefully, there are sufficient levels of fissionable and fusible materials on the moon. At that point, man kind could return to using chemical rockets as ferries to get into space; to deliver small cargos and personnel to the constructions stations.
How would you pay for this venture? That begs the question: Whats the best way to profit of a massive nuclear pulse drive in space? To move asteroids! Mining of the asteroid belt would be a serious proposition, and the low gravity (and lack of atmosphere) makes the usage of our Orion drives even more palpable. It would be necessary to figure out a cheap way to return these metals to earth; however, initial studies have suggested that even very small asteroids (1 mile diameter) can contain tens of trillions of dollars of metals.
The loss rate would be terrific, but one could imagine breaking asteroids into 500 m chunks, surrounding them with layers of ceramic heat shield, and them aiming them for the middle of the ocean, Siberia, or other wasteland type area. I have a feeling we can devise a more elegant solution over time.
This could happen in our lifetime. We could already be living this if NASA hadn't given up on Orion in the 1960s because of the Nuclear Test Ban Treaty. This is the future of space travel, not tiny chemical rockets which cost tens of thousands of dollars to move a kilogram.