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Input: "I'm still kind of in shock " says Edward Geist  a researcher specializing in Russia at the Rand Corp. "My guess is they're not bluffing  that they've flight-tested this thing. But that's incredible."
The U.S. did go on to investigate the idea of a nuclear-powered missile   Geist  says. Known as the Supersonic Low Altitude Missile  the idea was more like a nuclear-powered drone aircraft. "It was actually supposed to fly around autonomously and drop nuclear gravity bombs "  Geist  says.
The nuclear reactor that would keep SLAM aloft would also spew radioactive exhaust   Geist  says. At the time  that was advertised as a feature  not a bug  because it would have had the added benefit of polluting the Soviet countryside.
"It was supposed to be really  really dirty "  Geist  says.
The U.S. got as far as actually building the nuclear engine for Project Pluto  a development project at the Nevada Test Site. The reactor was tested a number of times in the early 1960s  and it performed well. But by that point  awareness had grown about the dangers of nuclear fallout  and arms control treaties were coming into place   Geist  says. Those concerns were among the reasons the project died in 1964.
The type of reactor used in Project Pluto was particularly messy because it exposed the nuclear fuel directly to the outside air.  Geist  says the new Russian missile may use a different system that keeps the fuel somewhat isolated from the air. But   he  quickly adds  that wouldn't make it safe.
"There are a bunch of different ways to do it  and frankly  they're all terrible "  Geist  says.
 He  suspects that the Russian design would involve what's known as a "fast reactor " which is more efficient  but also less safe  than most nuclear reactors. If the missile crashed or the reactor failed  it would trigger a major incident.
"It's just crazy they field-tested this thing "  he  says.
 Geist  says  he  expects Russia's provocations to continue. "They're sending us a message that they are not OK with our U.S. missile defense posture "  he  says.
That message? "They're willing to go full Strangelove on us "  Geist  says.

Experts Aghast At Russian Claim Of Nuclear