SCOTT SIMON, HOST:
An explosion in northwestern Russia is bringing new attention to Russian claims that they've produced a nuclear-powered, nuclear-armed missile with global range. Now, Russia acknowledged that there was an explosion on August 8 - days later admitted it occurred during testing of a, quote, "nuclear isotope power source." At least five people have died. Authorities in neighboring Norway captured traces of radioactive iodine in the air shortly afterward.
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PRESIDENT VLADIMIR PUTIN: (Speaking Russian).
SIMON: Vladimir Putin unveiled the project last year.
EDWARD GEIST: It is quite surprising that the Russians are choosing to diversify their arsenal while pursuing nuclear-powered cruise missiles sort of technology.
SIMON: That's Edward Geist, policy researcher at the RAND Corporation. Nuclear-powered cruise missiles are appealing because they're hard to stop, and they don't need to refuel.
GEIST: The question of just how far it could fly is actually a very good one. So Putin said, in his speech, something to the effect that it could travel tens of times as far as a conventional cruise missile, whatever that means. It would suggest a flight time of a few days to maybe, like, a couple of weeks at the outside. But it's very different than forever.
SIMON: Forever or at least indefinitely - that's what the U.S. was shooting for in the 1950s and '60s with Project Pluto. American engineers imagined a weapon that was as big as a house and could fly at supersonic speeds just above treetops.
GEIST: It's normally called a nuclear cruise missile. But strictly speaking, it was less a cruise missile than - it was supposed to be an autonomous bomber, essentially. The project was the Supersonic Low-Altitude Missile, or SLAM. And it was exactly what it sounded like.
SIMON: Say we're standing in a field in Siberia when the Pluto SLAM passed overhead.
GEIST: The - I suppose the merciful part was that if you were standing directly under it and it was flying as low as it was supposed to fly, at least some of the time, you might not actually have survived very long to even find out exactly what the longer-term consequences would be. It was suggested that the sonic boom alone would be highly destructive. You would actually be subject to nontrivial injuries possibly just from the sound if it had made. The exhaust was - it was suggested that it would actually, you know, cook the chickens in the chicken coop as the thing flew over. And that, of course, is just totally eliding the fact that it was supposed to carry something between 16 and 24 gravity-dropped hydrogen bombs.
SIMON: The building-sized missile with a deadly sonic boom propelled by an unsealed nuclear reactor spewing lethal radioactive exhaust and dropping H-bombs - the U.S. built and tested reactors at a site in Nevada. The Pluto SLAM was never flight-tested.
GEIST: When they first conceived this in the '50s, there were these ideas like, we'll just sort of fly it around in a - in, like, a figure-eight pattern or something. And then we'll ditch it in the deepest part of the ocean (laughter) that we can find. And so by the early '60s, when these test reactors are being built, it was already clear that that sort of thing was probably not going to be acceptable.
SIMON: So the U.S. ended Project Pluto in 1964, same year a film called "Dr. Strangelove" hit theaters. Transcript provided by NPR, Copyright NPR.