On: Project Orion

[KineticLensman]

That doesn't sound part of Niven's Known Space canon.

However, 'Footfall' by Niven and Pournelle does have an Orion, as does Invisible Sun, by Charles Stross.

Nothing obvious in [0]

[0] https://en.wikipedia.org/wiki/List_of_stories_featuring_nucl...

[AtlasBarfed → KineticLensman]

It was a Niven / Pournelle mashup. Also, Lucifer's Hammer is a fun read I recall.