Warren Ellis –

The human race has had the technical ability to send a crewed mission to Mars for decades.

All the human race is currently missing is the proven technical ability to get a crewed mission there safely, in a decent period of time, without the crew dying, landing without the crew dying, keeping everyone alive on the surface, launching back to orbit safely, and getting everyone back to earth again without the crew dying.

If you want to just stick a bunch of engines and fuel tanks to a shipping container and fire it in the general direction of Mars on a straight injection, then von Braun of the SS wrote that technical specification in 1948.