https://www.yahoo.com/finance/news/thermal-nuclear-engine-could-us-230600114.html Ultra Safe Nuclear Corporation (USNC) has designed a new thermal nuclear engine it says could carry astronauts to Mars in just three months—and back to Earth in the same amount of time. By using ceramic microcapsules of high assay low enriched uranium (HALEU) fuel, USNC's thermal nuclear engine could cut the trip in half even from optimistic estimates.
If we'd been willing to use nuclear pulse propulsion, we could have colonized the solar system by now. But the threat of having nuclear weapons in space was too great.
Those ships wouldn't land. They'd go back and forth between Earth orbit and other destination. Besides, containment in the event of a disaster is an engineering problem, not an inherent deal breaker.
Oh, I think I didn't get you right! You were talking about something like this here? https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) If yes, my comment with the Challenger Disaster was, of course, incorrect.