Nuclear spaceship

[lkm]

Here's the abstract for the Grooved ring reactor paper from IAC-08.

http://www.iafastro.net/iac/archive/file/IAC-08/abstract/IAC-08.C4.7.-C3.5.6.pdf

[lkm]

I've been reading the Roadmaps and Priorities report and I found it odd that TA01 1.5.5 Nuclear Launch was found non credible by the panel.
1.5.5 was a a Nuclear Combined Cycle engine and listed as a game changing concept and propulsion system in the draft report. Because the panel decided it was non-credible it has the lowest possible QFD score of -38 because the benefit and alignment  scores were zeroed out while it still was the most challenging concept imagined.
For comparison RBCC and TBCC scored 150 and in space nuclear thermal scored 274 and if you directly combine their scoring and NBCC is credible then it would score 268 and be a high priority technology.
So the question is, is NBCC credible or not and if so what should it have scored?