Relatively new poster, long time Lurker...<br /><br />Been reading posts, and some over at Astronautix.com and edu-ma-cating myself on various launch and propusion technologies.. neat stuff, and it all reminds me that I should have paid more attention in math classes... But that's another story...<br /><br />I got to thinking about Nuclear Thermal propulsion and have a question..<br /><br />GIVEN: Mention the word "Nuclear" and the project is as dead as last weeks mackeral before it even gets started... No reactor of any kind is going to be built in the US or any other place I'm aware of for at least the next 30 years... maybe longer. Whether the hazards are real or imagined is irrelevant.. emotion trumps any reality involved. And of COURSE there ARE real risks and hazards in using nuclear fission to heat a reaction mass... again, put that partly aside...<br /><br />My question is;<br />"How hard would it be, really, given todays technology"?<br /><br />Or, asked another way; "How close could we be if not for the emotional response to the word "Nuclear""?<br /><br />I noticed some "projects" as late as the early 1990's under Nuclear Thermal engines.. and one VERY impressive Russian "design" from 1962-70, the RD-600, with 200,000 kgf and 2000 sec/ISP. Also the "Timberwind" US designs dated "1990".<br /><br />How close were any of them to a "flyable" engine? <br />I know the Nerva program had at least a few test-stand firings, but how far was/is nuclear thermal from something that could lift a useful payload?<br /><br />Curious to read any discussion! (even if it's "hey, you idiot, we just talked about this! ")<br /><br />Paul F.