This is an upload of Nyrath's USAF Orion mod (see forum post).
My changes have been to just tweak it so it runs in KSP v1.0.5.
At least, mostly run. The GUI hasn't worked since the release of 0.8, so you have to set up bomb control using control groups. This is incompatible with the USAF Orion TD Edition. One or the other, not both.
This is the 10m full scale Orion engine planned for USAF use. It was the smallest Orion size put forward by General Atomic, and it pretty much the same as the version they tried to sell NASA on. Basically, 10m fits on top of Saturn V lower stages, so you can pretend you're going to loft it up before enaging propulsion-by-nuke. There's plenty about what an Orion drive is in the forum posts, especially the links to Nyrath's atomicrockets site.