http://www.projectrho.com/rocket/enginelist.php#id--Gaseous_Core_Nuclear_Thermal_Rocket http://en.wikipedia.org/wiki/Gas_core_reactor_rocket How practical would this be? How much of a technological leap would be needed to achieve this? Would it make outer solar system missions possible? Could the technology be used for non space applications? I bring this up because Discovery One from 2001: A Space Odyssey apparently uses something like this.