Because of the huge expense and perceived need for gargantuan launch vehicles that don’t yet exist, the conventional wisdom in the space community is that a human mission to Mars is many years off, perhaps not to be achieved until 2030 or so. But space adventurer Dennis Tito is about to announce a plan to do one privately about five years from now.

What’s the catch? Well, first of all, there are no plans to land on the planet itself, which is one of the hardest parts of a Mars mission, due to its thin atmosphere, demanding a lot of propellant that must be hauled all the way there. In fact, there are no plans to even go into orbit around the planet, which itself would also be costly in propellant, both to enter and depart. The mission is much simpler — a two-person flyby on a so-called “free return” trajectory, allowing it to get back to earth without the need for an engine burn at Mars. The total trip time will be about a year and a half. It would be the ultimate human adventure to date.

Is it possible? Yes, in theory, if SpaceX delivers on their promise of the Falcon Heavy, the proposed launch vehicle for the mission. For a non-stop sprint to the Red Planet and back, one or two of them probably have adequate performance. The proposed spacecraft seems to be the existing SpaceX Dragon, which has only been used for cargo missions to the International Space Station so far, but is planned for crew delivery within three years. While those are low-earth-orbit (LEO) missions, SpaceX claims that the heat shield is capable of coming all the way back from earth-escape velocities (over twice the energy of a LEO entry), such as would be the case for a moon or Mars mission. The life support system will be provided by Paragon, which is the contractor for ISS crew delivery missions as well. Given that a Dragon is priced at about sixty million, and a Falcon Heavy flight at $120M, one can imagine a total mission cost of less than half a billion dollars, perhaps quite a bit less, putting it in the reach of many wealthy individuals.

The question is, will it be possible in practice? That’s more problematic.