We don't have the technology to get a person to Mars or to land them when they get there. We probably have the technology to build a spaceship that they could die in on the way there - but that's the closest that we realistically have.

Surviving on the way to Mars isn't a huge leap in difficulty over a space station, and we have those on lock.

There's much greater radiation exposure away from Earth's magnetic field. I believe this is still an unsolved problem. Proposed solutions for shielding are heavy and expensive.

You just have to keep the lights on and not die of cancer for six months. The radiation isn't that bad.

Edit: The specific number is under 2 millisievert per day. And "One sievert carries with it a 5.5% chance of eventually developing fatal cancer based on the linear no-threshold model."

I though shielding with water was the way forward there.

In science fiction novels...

It's much harder if you include the return trip.

You have to keep things going for 3 years, but I think such a trip is still pretty straightforward with our current abilities.

But wow what a drawn-out load of nothing a mission like that would be.

No resupply, no spares - no chance.

There's room on board for literal tons of spares.

> We’re currently at a few billion to put a whole horde of them on Mars I believe.

Uh... don't count your Mars shots before they're hatched. Even getting robot probes to Mars is very very hard. Only about half of Mars missions have been successful. In fact, since the fall of the Soviet Union only one organisation has succeeded in putting working probes on the Martian surface: NASA/JPL.

I don't think it's impossible that SpaceX will get there, but certainly not soon and not for "a few billion". If they succeed at all, it will require drawing on years on investment and expertise by NASA.

https://mars.nasa.gov/mars-exploration/missions/historical-l...

https://www.bbc.co.uk/news/science-environment-53589767