G1 Engine
Methalox gas-generator rocket engine designed for manufacturability, testability, and operational simplicity.
Overview
The G1 is a methalox rocket engine developed by Tomorrow for use on the L1 launch vehicle. It uses liquid methane (LCH₄) and liquid oxygen (LOX) as propellants in a gas-generator power cycle.
The injector at the heart of the G1 is of the coaxial swirl type, chosen for its excellent atomisation and combustion stability. Propellants are fed by a turbopump assembly driven by the gas generator exhaust.
Regenerative cooling is employed to manage the thermal environment within the thrust chamber, routing propellant through channels in the chamber wall before injection.
G1 Sea Level
The sea-level variant features an expansion ratio optimised for low-altitude performance. It serves as the primary propulsion system for the L1 first stage, where nine engines operate in a clustered configuration.
The lower expansion ratio nozzle prevents flow separation at sea-level ambient pressures, ensuring stable combustion from ignition through stage separation.
G1 Vacuum
The vacuum variant incorporates an extended nozzle with a higher expansion ratio, maximising specific impulse for upper-stage applications where atmospheric backpressure is minimal.
Both variants share common turbomachinery, injector, and combustion chamber assemblies — only the nozzle extension differs, simplifying manufacturing and qualification.
Design Philosophy
The G1 engine is designed around three core principles: manufacturability, testability, and operational simplicity. Every design decision prioritises reliability and ease of production.
The coaxial swirl injector provides excellent propellant mixing without the complexity of pintle or impinging-jet designs. Regenerative cooling eliminates the need for ablative liners, enabling engine reuse potential. The torch igniter provides reliable, repeatable ignition across all operating conditions.
G1
| General | |
|---|---|
| Manufacturer | Tomorrow |
| Application | Booster & upper stage |
| Associated LV | L1 |
| Status | In development |
| Liquid-Fuel Engine | |
| Propellant | LOX / LCH₄ |
| Cycle | Gas-generator |
| G1 Sea Level | |
| Thrust class | 60+ kN |
| Isp (sea level) | ~285 s |
| Isp (vacuum) | ~310 s |
| G1 Vacuum | |
| Isp (vacuum) | 338 s |
| Design | |
| Injector | Coaxial swirl |
| Cooling | Regenerative |
| Ignition | Torch igniter |