Which is odd, considering they made it work perfectly well in the sixties.
http://www.designation-systems.net/dusrm/m-49.html.
Not to mention the Moscow defence ring, and other projects-
http://www.ausairpower.net/APA-Rus-ABM-Systems.html
And I have to query your definition of "precision" if you think laser beams don't qualify.
Back to the beginning, the planned service version DC-Y as a launch vehicle, the full scale version, would have been a potential Shuttle replacement with much less turnaround time and cost; probably smaller payloads, less efficient as a rocket- there are good reasons for staging after all- but so much more reusable that overall costs would have gone down; incrementally, we're not talking order of magnitude leaps, but enough to make space access more viable.
I don't think the bureaucratised NASA of the early eighties would have known what to do with a working pebble bed nuclear thermal rocket; the big dreams had kind of lain down and gone
ppthbbbt, post non-Apollo. It would either have made or broken them, if they could have come up with mission plans to make use of it or not.
We are basically looking at outpost emplacement, carrying heavy payloads to far away places and being repurposed as a settlement power plant after landing; was the supporting hardware, space suits and space tools, remotely ready? Did they have a non blue sky, not produced by an SF writer plan for a long haul spaceship? Doubt it.