Remember Dennis Tito? He's the millionaire who became the first space tourist back in 2001, who bought himself a ticket on a Soyuz heading to the International Space Station. Now he's got some big new space plans: he wants to send two people on a Mars flyby mission in 2018. If he can pull it off, there's lots of interesting things that will happen even if you ignore the fact that two people will swing around Mars.
First off, and most importantly, I'm pretty sure this mission would be the first to have a confirmed two-person sex act in space. That's because this 501-day mission will be crewed by a male and female pair, and they're looking for a married couple, ideally. Almost two years in a cylinder about the size of a Winnebago with sleek, sexy space-jammies on? There will be some space on-it-getting.
This would be the longest single space mission ever, though not by as much as one would think. Valeri Polyakov spent 437 days on the Mir in 1994-95, so it's reasonable to think this mission duration is achievable. The 2018 date is important, as that's when Mars and Earth will be unusually close together, allowing for a round trip time of less than a year and a half as opposed to two to three years.
The mission plan calls for using a free-return trajectory, which allows for essentially a free (as in no fuel needed) return trip to Earth. Apollo 13 used a slightly modified version of this trajectory to get their wounded spaceships back from the moon, and this is a very sensible plan for this mission. It does mean that actual time around Mars won't be substantial (though at about 100 miles above the surface, it should be dramatic), as they won't actually be entering orbit, but that's not really what this particular mission is about.
The current plan calls for use of SpaceX hardware, specifically the Falcon 9 heavy-lift rocket and the yet-to-be-flown manned version of the Dragon capsule. Additionally, early renderings show the use of an inflatable orbital module, similar to what's being developed at Bigelow Aerospace.
If this is the configuration used, it would make a great template for a variety of future intra-solar-system spacecraft. The layout would be akin to a larger, modernized Soyuz, and this would likely be the first big, long-term use of an inflatable module. I'm assuming exhaustive testing would be done on a similar unit on the ISS or an independent Earth-orbiting unit first, of course.
There's also the radiation-shielding issues to work out, which may prove the biggest hurdle.
The interesting thing about the whole mission is how plausible it actually is. The goal is actually fairly modest, though it does push the limits of currently available technology. Heat shielding on the Dragon would have to upgraded for non-orbital re-entry speeds, there'd be lots of life-support and supply issues to work out, but there's nothing really pie-in-the-sky here. Except maybe whatever freeze-dried pies they elect to take with them.
I hope this will happen; a flyby is a great, relatively low-risk way to prove many unknowns about making such a journey to Mars. We did this with Apollo 8 around the Moon in 1968 before the Apollo 11 landing, and it makes sense to do this prior to a full Mars-mission.
So, even if we ignore the Mars part of this, there's lots of interesting possible firsts: longest manned mission, furthest manned mission, first ex-orbit use of inflatable modules, first ex-orbit use of the Dragon, likely some new firsts for radiation shielding and many new methods of crew sanity-keeping, feeding, and the like.
It'd be the second married couple in space, but the first mixed-gender two-person crew, and, yes, I'm predicting the first, and likely repeated, two-person sex acts in space.
Let's throw these crazy kids around Mars.