Nuclear thermal engines use the heat of a nuclear reactor to heat a propellant. Although early Russian designs used ammonia or alcohol as propellant, the ideal working fluid is the liquid form of the lightest element, hydrogen. Nuclear engines would have twice the performance of conventional chemical rocket engines. Although successfully tested in both Russia and America, they have never been flown due primarily to environmental and safety concerns.
|Eng-engineslink||Thrust(vac)-kgf||Thrust(vac)-kN||Isp-sec||Isp (sea level)-sec||Designed for||Status||YaRD OKB-670||170,000||1,667.00||470||430||First Stages||Developed 1958-1960|