Interstellar nuclear-powered transport (1968) [pdf] - https://news.ycombinator.com/item?id=28132756 - Aug 2021 (34 comments) - thanks antondd!
Orion Project [pdf] - https://news.ycombinator.com/item?id=22691219 - March 2020 (1 comment)
Nuclear Pulse Propulsion – Orion and Beyond (2000) [pdf] - https://news.ycombinator.com/item?id=12705705 - Oct 2016 (99 comments)
Project Orion (nuclear propulsion) - https://news.ycombinator.com/item?id=9025611 - Feb 2015 (11 comments)
Project Orion (nuclear propulsion) - https://news.ycombinator.com/item?id=3019627 - Sept 2011 (1 comment)
Project Orion is one of the stupidest, most wonderful ideas ever conceived in America. - https://news.ycombinator.com/item?id=261348 - July 2008 (6 comments)
That's less than I expected - are there other threads?