@cstross Spartan, it is a long time ago, might have been intended to take out the warhead, later the manoeuvring bus, above the atmosphere. Or to stress the Russian economy while feeding capitalist Americans. Or all of the above.
A collimated beam/pulse of neutrons from near ground level would have to be moving very very fast for its half life to leave it effective, which would make interesting energy release on the way. And cartridges might be no cheaper than Sprints, if even possible.