Every discussion of a manned mission to Mars inevitably touches on the practicality of a one-way, no-comin'-back trip. Sending a lone astronaut, or a small team, on a trip to a planet roughly 50 million miles away (when the orbits of Earth and Mars are relatively aligned) becomes much more viable when you don't have the carry all of the fuel they'd need to get back. Private spaceflight project Mars One is now moving forward with this idea, and hopes to establish a settlement on Mars in the year 2023.
NASA doesn't currently support the idea of a one-way trip to Mars, but The Atlantic wrote a great feature on a similar plan, from way back in 1962, that NASA probably thought long and hard about before going with the Apollo program. It was named the Cord/Seale plan after two engineers at Bell Aerosystems. After John F. Kennedy charged NASA with reaching the moon by the end of the decade, Cord and Seale proposed a way to make that trip by 1965: Send one astronaut, alone, with no way to get back.
"The pair formulated a plan to build a one-man spacecraft, ten feet wide and seven feet tall, that would be large enough to house a single human occupant. It would be half the weight of John Glenn's Mercury capsule. It would include tools and medical supplies and a battery-powered spacesuit. It would be equipped with enough oxygen for 30 days of space travel and enough water for 12. It would also include a nuclear reactor that would generate electrical power.
As Mary Roach outlines in her book Packing for Mars, a series of nine subsequent launches would head to the moon to provide this ultimate lone ranger with a better living module, better communications equipment, and the nearly 10,000 pounds of the food, water, and oxygen he would need to survive away from Earth. During which time, Cord and Seale figured, NASA would have had time to determine the details of another mission -- a rescue mission, essentially -- that would come to pick him up and bring him home."
Unlike the proposed trips to Mars, the astronaut in Cord and Seale's proposal would, after a few years, make it back to Earth. The political reasoning behind their idea is especially interesting. It was partially based on practicality, but it was also the only way they predicted being able to beat the Russians to the moon. At the time, their reserach suggested Russia could put a man on the moon as early as 1965, and there was no way NASA could launch a two-way trip that quickly.
By 1969, the two engineers predicted a three-man ship could carry two more astronauts to the moon and bring the lone explorer back to Earth with them. Assuming, of course, that he survived his time on the moon. It's not hard to see why NASA passed on the plan and decided on the roundtrip that eventually took place in 1969. As much of a political black eye as it would've been to have the Russians land on the moon first, having an astronaut die, stranded, on the moon, would be both tragic and a PR disaster.
That no doubt plays a role in NASA's hesitance to send astronauts on a one-way trip to Mars, as well, but there are many space experts who support the idea. Read the rest of The Atlantic's piece for more on our plans for Mars; and if you're really into the idea, check out the 99% Invisible podcast episode devoted to the subject.