NASA's nuclear thermal propulsion.

https://www.newswise.com/articles/uah-modeling-the-spacecraft-for-nasa-s-nuclear-thermal-propulsion-idea

Seems a good idea to me. And nice to know there's a low risk if there's an accident.  And aprently, the radiation from the nuclear propulsion system is less than the astronauts would receive from a longer duration conventionally powered mission.

"Nuclear thermal propulsion (NTP) can help achieve the goals of low weight, high power and good economy. An NTP engine uses low enriched uranium (LEU) to heat a lightweight propellant such as liquefied hydrogen to 2,800 degrees Kelvin through channels in the core. The expanding gas exits the nozzle, providing thrust. If something goes awry and the craft crashes to Earth, the engine design and use of LEU reduce the chance of a catastrophic nuclear incident to near zero, as well as making flight safer for the crew."

"The heartbeat of the program at this time is demonstrating that the reactor elements can be manufactured such that they will function in and survive the intense environment internal to the engine,” says Dr. Dale Thomas, The University of Alabama in Huntsville's eminent scholar in systems engineering, who is the principal investigator for a UAH research grant with NASA’s NTP Program Office. Under the management of NASA researcher Dr. Bill Emrich, who teaches nuclear propulsion as an adjunct UAH faculty member, that testing is underway at NASA’s Marshall Space Flight Center (MSFC) in the Nuclear Thermal Rocket Element Environmental Simulator "