Valentin Glushko, who then held a near-monopoly on rocket engine design in the Soviet Union, proposed the RD-270 engine using unsymmetrical dimethylhydrazine (UDMH) and nitrogen tetroxide (N2O4) propellants to power the newly enlarged N1 design. These hypergolic propellants ignite on contact, reducing the complexity of the engine, and were widely used in Glushko's existing engines on various ICBMs. The full flow staged combustion cycle RD-270 was in testing before program cancellation, achieving a higher specific impulse than the gas-generator cycle Rocketdyne F-1 despite the use of UDMH/N2O4 propellants with lower potential impulse. The F-1 engine was five years into its development at the time and still experiencing combustion stability problems.