Burevestnik flew 14,000 km for 15 hours on nuclear power on Oct 21; Gerasimov briefs Putin on 'invincible' evasion capabilities.
Putin orders final preparations post-key trials; unique intercontinental weapon with unlimited range via nuclear propulsion.
Revives 2018 project after 2019 White Sea radiation incident; bolsters Russia's arsenal amid Ukraine war and nuclear drills.