Soviet hypergolic heavy-lift orbital rocket

Proton has been flying since 1965, carrying Soviet and then Russian heavy payloads on a toxic mix of nitrogen tetroxide and hydrazine — propellants that have caused several serious accidents over the decades. It made over 400 flights in total but has been winding down: its February 2026 launch of the Elektro-L 5 weather satellite ended the longest gap in the rocket's history, following nearly three years on the ground.