"Modeling the Performance of the Burevestnik Nuclear-Powered Cruise Missile":

https://bpb-us-e1.wpmucdn.com/sites.mit.edu/dist/6/1499/file...

Much more informative than I thought. So it's not Pluto, it's something like variant 2 of the NB-36's engine, a direct air cycle nuclear turbojet. A bit less insane than Pluto, but it raises a whole other herd of questions.

I'm a huge booster of nuclear propulsion in aviation. Although the "floor mass" of a nuclear system is high, the power density of the system as a whole is so high it might as well be aliens. For subsonic heavy lift - and I do mean heavy - a nuclear-electric system is probably the ideal propulsion system. And with dozens or hundreds of ducted fans that you can stick in any damn place, you get to play with a lot of aerodynamic tricks that are just plain tiresome when you are dealing with ducts and ducts of hot gases blasted from a centralized reaction engine: active laminar flow controls; blown flaps; entirely solid-state control actuation via differential power; all kinds of tricks with lifting surface geometries; the sky's the limit.

That said: the Direct Air Cycle as envisioned by variant 2 of the XB-36 was, admittedly, insane, and Project Pluto on the SLAM was in a whole other league - an engine that could never, ever, be flight tested. Reminiscent of the Rocketdyne Arbit/Clapp tripropellant engine of the same era . . although I think I would rather stand next to a Pluto engine running full bore than get anywhere near a reaction engine blown full of liquid fluorine and molten lithium. The Russki bird is (probably) a DAC nuke turbojet, dialing down the crazy just a touch.

But then the question: it's a giant non-stealth subsonic thing. I realize it has endurance to fly at any altitude for any length of time - at least until salt spray eats the inside of the core - but subsonic, it will get intercepted, and since it's a nuke, it's going to be no-holds-barred when it comes to what you use to knock the thing down. Sprint missiles had nuke payloads for essentially the same reason. So I'm not sure what the mission profile of this thing looks like. At least with Pluto, terrain hugging Mach 3+, you were going to have a very hard time catching up with it before it zoomed off below the horizon again, and by that time in this kind of fight AWACS is having the very worst of days.