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Full-Flow

Short answer: 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.

VideoWrite-up1 sources
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What should you know about Full-Flow?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. Fuel and oxidizer each have one.

    DD-446-F01 · Write-up · Exhibit A (Preburners)

  2. Enter the chamber as gas.

    DD-446-F02 · Write-up · Exhibit B (Gases)

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

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!

Burned-in captions, read frame by frame (see transcript.md) · 24.6s Reel ·

Video coming soonFull-Flow · Instagram Reel
Full-Flow: In a Full-Flow Engine, All Fuel and Oxidizer Pass Through Preburners Instagram Reel · · 24.6s

The write-up

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

  1. Exhibit A

    Preburners

    Fuel and oxidizer each have one.

  2. Exhibit B

    Gases

    Enter the chamber as gas.

  3. Exhibit C

    Turbines

    Run cooler.

  4. Exhibit D

    Pressure

    High chamber pressure.

  5. Exhibit E

    Raptor

    First to fly.

Questions people ask about Full-Flow

What passes through preburners?

Full flow.

Source: Write-up · Exhibit A (Preburners) · Wikipedia: Staged combustion cycle

In what form do they enter the chamber?

Hot.

Source: Write-up · Exhibit B (Gases) · Wikipedia: Staged combustion cycle

Which engine first flew it?

SpaceX.

Source: Write-up · Exhibit C (Turbines) · Wikipedia: Staged combustion cycle

What runs cooler?

Split flow.

Source: Write-up · Exhibit D (Pressure) · Wikipedia: Staged combustion cycle

What does it enable?

Performance.

Source: Write-up · Exhibit E (Raptor) · Wikipedia: Staged combustion cycle

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. What passes through preburners?

    1. All fuel and oxidizer
    2. Only fuel
    3. Only oxidizer
    4. Nothing
    Show the answer

    Answer: A. All fuel and oxidizer Full flow. Source: Write-up · Exhibit A (Preburners) · Wikipedia: Staged combustion cycle

  2. In what form do they enter the chamber?

    1. Gas
    2. Liquid
    3. Solid
    4. Plasma
    Show the answer

    Answer: A. Gas Hot. Source: Write-up · Exhibit B (Gases) · Wikipedia: Staged combustion cycle

  3. Which engine first flew it?

    1. Raptor
    2. Merlin
    3. RS-25
    4. F-1
    Show the answer

    Answer: A. Raptor SpaceX. Source: Write-up · Exhibit C (Turbines) · Wikipedia: Staged combustion cycle

  4. What runs cooler?

    1. Turbines
    2. Nozzle
    3. Tanks
    4. Fins
    Show the answer

    Answer: A. Turbines Split flow. Source: Write-up · Exhibit D (Pressure) · Wikipedia: Staged combustion cycle

  5. What does it enable?

    1. High pressure
    2. Lower thrust
    3. Solid fuel
    4. Smaller tanks
    Show the answer

    Answer: A. High pressure Performance. Source: Write-up · Exhibit E (Raptor) · Wikipedia: 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/

Permalink: https://detailenjoyer.com/case/full-flow/ · Last updated

Markdown version

Cite a single fact by its ID, for example DD-446-F01 → https://detailenjoyer.com/case/full-flow/#DD-446-F01