Evolution of SpaceX Starship Raptor Engine.
Pretty cool evolution of the SpaceX Raptor engines that they developed for the Starship rockets. The first version 3 Raptor just came off the assembly line. Lighter, more powerful, clean, no more need for heat shields or a fire suppression system in the engine bay.
Amazing how they were able to get rid of all the external piping and wiring. The next flight coming up will still be using the older ones. Not sure how long it will be before the first rocket flies using the new engines. They currently use 33 engines on the booster and 6 engines on the ship (39 total).
What is the Raptor
Raptor is a family of rocket engines developed and manufactured by SpaceX. A notable trait of this engine family is the use of a full-flow staged combustion cycle (FFSC). They are powered by cryogenic liquid methane and liquid oxygen, a mixture known as methalox.
SpaceX’s super-heavy-lift Starship uses Raptor engines in its Super Heavy booster and in the Starship second stage. Starship missions include lifting payloads to Earth orbit and is also planned for missions to the Moon and Mars. The engines are being designed for reuse with little maintenance.
Raptor is the third full-flow staged combustion engine in history and the first such rocket engine to power a vehicle in flight
Performance stats for each version:
| Raptor Performance at level | Raptor 1 | Raptor 2 | Raptor 3 |
| Thrust | 185tf | 230tf | 280tf |
| Specific impulse | 350s | 347s | 350s |
| Engine mass | 2080kg | 1630kg | 1525kg |
| Engine + vehicle-side commodities and hardware mass | 3630kg | 2875kg | 1720kg |
Design of Raptor Engine
Raptor is designed for extreme reliability, aiming to support airline-level of safety required by the point-to-point Earth transportation market. Gwynne Shotwell claimed that Raptor would be able to deliver “long life… and more benign turbine environments”
Raptor Engine Propellants
Raptor is designed for deep cryogenic propellants—fluids cooled to near their freezing points, rather than their boiling points, as is typical for cryogenic rocket engines. Subcooled propellants are denser, increasing propellant mass as well as engine performance. Specific impulse is increased, and the risk of cavitation at inputs to the turbopumps is reduced due to the higher propellant fuel mass flow rate per unit of power generated. Cavitation (bubbles) reduces fuel flow/pressure and can starve the engine, while eroding turbine blades. The oxidizer to fuel ratio of the engine is approximately 3.8 to 1.
Liquid methane and oxygen propellants have been adopted by many companies, such as Blue Origin with its BE-4 engine, as well as Chinese startup Space Epoch’s Longyun-70.
Manufacturing and materials
Many components of early Raptor prototypes were manufactured using 3D printing, including turbopumps and injectors, increasing the speed of development and testing. The 2016 subscale development engine had 40% (by mass) of its parts manufactured by 3D printing. In 2019, engine manifolds were cast from SpaceX’s in-house developed SX300 Inconel superalloy, later changed to SX500.
Raptor 3 is designed for rapid reuse, eliminating the need for engine heatshields while continuing to increase performance and manufacturability.
