[zunzun]

A 3,000 mile long trail of diffuse atmospheric radioactive contamination produced by the white-hot nuclear powered solid-state scramjet engine, followed by a crash of the spent nuclear fuel into Kamchatka. The crash site will have to be off-limits for millennia, increasingly leaching into the groundwater there with every rain storm and blowing about every dry season.

[londons_explore]

I think it's conventionally fuelled, just can carry a nuclear warhead.