SpaceTRC / Rocket Engine Atlas
The machines that fly rockets
From Saturn V’s F-1 to Starship’s Raptor, from Rocket Lab’s electric-pump Rutherford to Japan’s LE-9: 19 engines. See how each one works in animated diagrams and compare their numbers.
Values are those given by manufacturers and public technical sources, checked on 2 November 2026. Where sources disagree, the engine’s card carries a note.
How it works
Engine cycles, animated
The real challenge of a liquid engine is pumping hundreds of kilograms of propellant a second against the high pressure of the combustion chamber. How the turbine that drives the pumps is powered defines the engine’s “cycle”. Choose one:
Key concepts
Four numbers to read an engine
Specific impulse (Isp)
A measure of how efficiently an engine uses propellant, expressed in seconds. It equals exhaust velocity divided by standard gravity: 450 seconds means an exhaust velocity of about 4.4 km/s. Chemical rockets top out around 450–460 seconds.
Sea level and vacuum
Atmospheric pressure limits how far the exhaust can expand, so the vacuum version of an engine, with a much larger nozzle, is more efficient: Merlin 1D gets 282 s at sea level and its vacuum version 348 s.
Chamber pressure
Higher pressure lets an engine be smaller and more efficient. RD-180’s 26.7 MPa chamber pressure equals the water pressure about 2.7 km deep in the ocean.
Thrust
Given in kilonewtons (kN); 1 kN is about 102 kilograms-force. Saturn V’s F-1 produced 6,770 kN at sea level, a force of about 690 tonnes.
Atlas
19 engines, as cards
Sort, filter by propellant and pick two engines to compare side by side.
Chart
Thrust and efficiency map
The horizontal axis is thrust (log scale) and the vertical axis specific impulse. Hydrogen engines cluster at the top for efficiency, while solids are the most powerful but least efficient.
Propellants
Why different propellants?
Kerosene and liquid oxygen
A dense fuel that can be stored at room temperature, keeping tanks small. Specific impulse is around 300–340 s. It leaves soot, so reused engines need cleaning.
Liquid hydrogen and liquid oxygen
The most efficient chemical pair (about 450 s). But hydrogen is so light that it needs huge tanks and must be kept at −253 °C.
Methane and liquid oxygen
Burns cleanly, suits reuse and can be made on Mars from carbon dioxide and water. Specific impulse 330–380 s. Starship, New Glenn and Neutron chose it.
Solid propellant
Fuel and oxidizer are combined in a single solid block. Very high thrust and simplicity, but it cannot be shut down once lit and efficiency is low (about 250–270 s).
See the rockets these engines fly in Rocket comparison and the 3D rocket explorer, and try the rocket equation in RocketLab.
- Engine values: manufacturer statements (SpaceX, Blue Origin, Rocket Lab, ArianeGroup, Mitsubishi Heavy Industries, NASA) and related technical summaries; checked on 2 November 2026.
- Raptor 3 thrust: SpaceX, August 2024 performance card (280 tf).
- Cycle diagrams are simplified by SpaceTRC for teaching; real engines also have valves, heat exchangers and ignition systems.
Last updated: 2 November 2026