# Full-Flow (DD-446)

> Full-flow staged combustion is a rocket engine cycle in which all of the fuel and all of the oxidizer pass through separate preburners that drive the turbopumps, then enter the main combustion chamber as hot gases. Splitting the flow lets the turbines run cooler and supports high chamber pressures. SpaceX's Raptor was the first such engine to fly. The footage shows engine test firings.

- Department: Space (also Tech)
- First published: 2025-01-02
- Last updated: 2025-01-02
- Permalink: https://detailenjoyer.com/case/full-flow/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-446-F01**: Fuel and oxidizer each have one. _(Write-up · Exhibit A (Preburners))_
- **DD-446-F02**: Enter the chamber as gas. _(Write-up · Exhibit B (Gases))_

## Write-up

In a full-flow engine, all fuel and oxidizer pass through preburners. Both enter the main chamber as hot gas.

1. **Preburners**: Fuel and oxidizer each have one.
2. **Gases**: Enter the chamber as gas.
3. **Turbines**: Run cooler.
4. **Pressure**: High chamber pressure.
5. **Raptor**: First to fly.

## Related case files

- [Anatomy of a Combustion Engine (DD-334)](https://detailenjoyer.com/case/anatomy-of-a-combustion-engine/): I linked more engine cycles

## Reel vs. record

- **Note**: The Reel says the design lowers turbopump temperature; more precisely, it lets the turbines that drive the pumps run cooler.

## Video: Full-Flow: In a Full-Flow Engine, All Fuel and Oxidizer Pass Through Preburners

- Duration: 24.6 s · Published: 2025-01-02
- File: https://detailenjoyer.com/assets/videos/DEUXPjkqs_j.mp4

### Transcript

Full-flow rocket engines are an advanced type of liquid rocket engine that uses full-flow staged combustion, a design in which both the fuel and oxidizer [are] preburned in separate preburners before entering the main combustion chamber. [An] advantage of the full-flow design is that it reduces the temperature [of the] turbo pumps [...] fuel and oxidizer are already in gaseous form when they enter. This allows for higher engine pressures and performance without compromising durability. NOW YOU KNOW!

## Questions & answers

**Q: What passes through preburners?**  
A: Full flow. _(Source: Write-up · Exhibit A (Preburners) · Wikipedia: Staged combustion cycle)_

**Q: In what form do they enter the chamber?**  
A: Hot. _(Source: Write-up · Exhibit B (Gases) · Wikipedia: Staged combustion cycle)_

**Q: Which engine first flew it?**  
A: SpaceX. _(Source: Write-up · Exhibit C (Turbines) · Wikipedia: Staged combustion cycle)_

**Q: What runs cooler?**  
A: Split flow. _(Source: Write-up · Exhibit D (Pressure) · Wikipedia: Staged combustion cycle)_

**Q: What does it enable?**  
A: Performance. _(Source: Write-up · Exhibit E (Raptor) · Wikipedia: Staged combustion cycle)_

## Sources

- [Wikipedia: Staged combustion cycle](https://en.wikipedia.org/wiki/Staged_combustion_cycle)

## Cite this case file

Easterling, Marcus. "Full-Flow." The Detail Department (DetailEnjoyer), case file DD-446, last updated Jan 2, 2025. https://detailenjoyer.com/case/full-flow/