Rocketdyne H-1
| An H-1 engine at the Udvar-Hazy Center | |
| Country of origin | United States | 
|---|---|
| First flight | 27 October 1961 | 
| Last flight | 15 July 1975 | 
| Designer | Rocketdyne | 
| Manufacturer | Rocketdyne | 
| Application | First stage | 
| Successor | RS-27 | 
| Status | Retired | 
| Liquid-fuel engine | |
| Propellant | LOX / RP-1 | 
| Cycle | Gas-generator | 
| Configuration | |
| Chamber | 1 | 
| Performance | |
| Thrust, sea-level | 900 kN (200,000 lbf) | 
| Thrust-to-weight ratio | 102.47 | 
| Chamber pressure | 700 psi (4,800 kPa) | 
| Specific impulse, vacuum | 289 s (2.83 km/s) | 
| Specific impulse, sea-level | 255 s (2.50 km/s) | 
| Burn time | 155 seconds | 
| Dimensions | |
| Length | 2.7 m (8.8 ft) | 
| Diameter | 1.5 m (4.9 ft) | 
| Dry mass | 1,000 kg (2,200 lb) | 
| Used in | |
| Saturn I, Saturn 1B | |
The Rocketdyne H-1 was a 205,000 lbf (910 kN) thrust liquid-propellant rocket engine burning LOX and RP-1. The H-1 was developed for use in the S-I and S-IB first stages of the Saturn I and Saturn IB rockets, respectively, where it was used in clusters of eight engines. After the Apollo program, surplus H-1 engines were rebranded and reworked as the Rocketdyne RS-27 engine with first usage on the Delta 2000 series in 1974. RS-27 engines continued to be used up until 1992 when the first version of the Delta II, Delta 6000, was retired. The RS-27A variant, boasting slightly upgraded performance, was also used on the later Delta II and Delta III rockets, with the former flying until 2018.