Hi All

NuclearSpace is definitely a very game web-site for suggesting using Orion and/or gas-core reactors to get into orbit. I personally have no problems with either modality - if we want battleship mass nukers sent into space, then it's the way to go.

However Saturn-V mass launch vehicles are kind of imposing, and explosive propulsive units are questionable in these days of global terror. I read a piece by Steve Howe in the July/August 2002 "Analog" which takes a more moderate view. He advocates solid-core NTRs for launch vehicles.

The old NERVA and Kiwi series of NTRs had 'hot' exhausts - but not too 'hot' mind you. However there have been advances in materials science that enable fuel elements that have no radioisotope leakage even after running at 3300 K for the 10 minutes needed for orbit.

Also the NERVA and Kiwi programs never had a propulsion chamber rupture and nor will their descendents due to the mechanical strength an NTR needs.

I think a safe SSTO NTR is doable. Ironically re-entry could be the most dangerous time of all. After 'Columbia' it could be a hard sell, but surely it's time something better than chemical rockets got us into orbit.

With an NTR perhaps an air-breathing hybrid with a semi-powered descent is more reasonable? Cuts out the 'Coulmbia' factor then.

Adam