The F-1 rocket engine was Rocketdyne’s kerosene and liquid-oxygen engine, and a single F-1 produced 1.5 million pounds of thrust, according to the Smithsonian National Air and Space Museum. Five F-1s powered the first stage of the Saturn V, giving that stage a combined 7.5 million pounds of thrust. The engine burned refined kerosene (RP-1) with liquid oxygen (LOX).
The F-1 suffered from combustion instability, a violent vibration that destroyed an entire engine in 1962, according to the National Aeronautics and Space Administration (NASA). Engineers spent more than three years on the fix. From 1967 to 1973, the 65 F-1s that flew on 13 Saturn V rockets had no combustion instability problems.
What the F-1 Engine Was
The F-1 was the engine that powered the first stage of the Saturn V, and Rocketdyne built it to burn refined kerosene with liquid oxygen. A single F-1 produced 1.5 million pounds of thrust, according to the Smithsonian National Air and Space Museum. The Saturn V carried five of them.
The fuel was refined kerosene, designated RP-1. The oxidizer was liquid oxygen, shortened to LOX.
The five engines had two different jobs on the stage. One F-1 sat fixed in the center. The four outboard F-1s could gimbal, which let them steer the rocket during the climb.
During a launch, the first-stage engines burned for just over two and a half minutes. After that burn, the first stage was jettisoned into the Atlantic.
For a plain-language primer on how a liquid engine turns propellant into thrust, read our guide to how rocket engines work.
F-1 Engine Numbers at a Glance
The F-1’s public figures cover thrust, propellants, burn time, engine layout, test history, and flight history. The table below lists them, with figures from NASA and the Smithsonian.
| Item | Figure |
|---|---|
| Thrust per engine | 1.5 million pounds |
| F-1 engines on the Saturn V first stage | 5 |
| Combined first-stage thrust | 7.5 million pounds |
| Fuel | Refined kerosene (RP-1) |
| Oxidizer | Liquid oxygen (LOX) |
| First-stage burn time in flight | Just over 2.5 minutes |
| Engine layout | 1 fixed center engine, 4 gimbaled outboard engines |
| 1963 test engine | 4 start tests, 192.6 seconds of total burn time |
| Flight use | 65 engines on 13 Saturn V rockets, 1967 to 1973 |
| Combustion instability in flight | None reported across those 65 engines |
| Not covered on this page | Weight, dimensions, chamber pressure, specific impulse, turbopump power, total engines built |
The combined thrust figure is simple multiplication. Five engines at 1.5 million pounds each equals 7.5 million pounds.
The Saturn V stood about 36 stories tall and weighed roughly 6.5 million pounds. Set 7.5 million pounds of thrust against that 6.5-million-pound figure, and the five F-1s pushed with about 1 million pounds more than the rocket weighed. That works out to a thrust-to-weight ratio of roughly 1.15 to 1.
The flight count checks out the same way. Thirteen Saturn V launches with five F-1s each comes to 65 engines, which matches the 65 F-1s that flew.
The 1963 test figure shows how ground testing compared with a mission. Four starts totaling 192.6 seconds averages a little over 48 seconds per start. The combined 192.6 seconds is longer than one flight burn of just over two and a half minutes, which is just over 150 seconds.
The F-1’s Job on the Saturn V First Stage
The five F-1s carried the Saturn V from the launch pad to roughly 40 miles of altitude at about 6,000 mph. They did that in a burn of just over two and a half minutes.
Steering on the first stage came from the four outboard F-1s. Because they could gimbal, the flight could be guided during the climb. The center F-1 stayed fixed.
When the burn ended, the spent first stage was jettisoned and fell into the Atlantic.
To see how the Saturn V’s first stage stacks up against other rockets, read our comparison of the largest rockets.
Development History of the F-1
The dates below trace the F-1 from contract to flight.
- 1958: The Air Force renewed the F-1 contract and raised the thrust target to 1.5 million pounds.
- August 1958: NASA’s Abe Silverstein began negotiations to move management of the engine from the Air Force to NASA.
- 1960: According to NASA, the F-1 showed combustion instability from its first firing.
- 1961: Rocketdyne fired a prototype F-1.
- 1962: Combustion instability destroyed an entire engine in a test that NASA sources date to June or July.
- 1963: A test engine completed four start tests totaling 192.6 seconds of burn time.
- Mid-1960s: The F-1 and the J-2 engine used concentric-tube injectors based on NASA Lewis Research Center designs.
- 1967 to 1973: 65 F-1s flew on 13 Saturn V rockets with no combustion instability problems.
The 1.5-million-pound target written into the 1958 contract renewal is the same thrust the Smithsonian gives for a single F-1. The goal set in 1958 was the figure the engine delivered.
Combustion Instability in the F-1 Rocket Engine
Combustion instability was a violent vibration in the F-1, caused by pressure swings from the burning propellant. NASA says the F-1 suffered from it from its first firing in 1960.
Once instability began, it could burn through the thrust chamber in milliseconds. In 1962, it destroyed an entire engine.
That 1962 loss came the year after Rocketdyne fired a prototype. NASA’s history of solving combustion instability covers the 1962 test.
How Engineers Fixed the Instability
Engineers fixed the F-1’s instability by adding copper dividers, called baffles, to the injector plate. The flat injector plate was too far along in development to redesign from scratch. The baffles sat between the injector holes and split the plate into compartments.
Proving the fix required a way to cause the problem on demand. Engineers detonated a small bomb inside the engine as it ignited, which induced instability on purpose. The baffles seemed to solve the problem.
The work took time. Rocketdyne program manager Sonny Morea led the effort, which ran more than three years.
A second line of work came from NASA’s Lewis Research Center. Lewis recommended concentric-tube injectors, and by the mid-1960s the F-1 and the J-2 both used concentric-tube injectors based on Lewis designs.
The F-1 Flight Record
From 1967 to 1973, 65 F-1 engines flew on 13 Saturn V rockets without a single combustion instability problem. Five years separate the 1962 engine loss from the first Saturn V flight in 1967. Each of those 13 launches put five F-1s through a burn of just over two and a half minutes.
The F-1’s record offers a template for reading any claim that an engine is “flight proven.” Look for three numbers or facts:
- How many engines flew. For the F-1, the count is 65.
- How many launches they flew on. For the F-1, the count is 13 Saturn V rockets.
- Whether the failure found in testing ever returned in flight. For the F-1, combustion instability did not.
An engine description that gives only a launch count, without the engine count or the fate of its known test failures, leaves out two of those three answers.
The F-1 Next to Later Engines
The F-1 is not in current service. Its last flights were the Saturn V launches of 1973.
The F-1 still works as a reference point when you read about newer engines. Three questions from its history can guide that reading:
- Which propellants does it burn? The F-1 burned RP-1 with LOX.
- How much thrust does each engine make, and how many engines share the load? The F-1 made 1.5 million pounds, with five on one stage.
- How was the injector shown to be stable? The F-1 team induced instability with a small bomb and tested the baffled injector plate against it.
Chamber cooling is a separate design question, covered in our regenerative cooling explainer. For related topics covered elsewhere on OrbitalIntel, read our explainers on the SLS rocket, the Artemis program, Falcon 9, and the N1 moon rocket.
For the source material behind this page, read NASA’s account of solving F-1 combustion instability and the Smithsonian’s story on the F-1 rocket engine.