Blue Origin BE-4

History

The Blue Origin BE-4, also known as Blue Engine 4, is a reusable liquid-propellant rocket engine developed and manufactured in the United States. It powers the first stages of the United Launch Alliance Vulcan Centaur and Blue Origin New Glenn launch vehicles.

The engine burns liquefied methane with liquid oxygen and uses an oxygen-rich staged-combustion cycle. Blue Origin designed it for repeated operation, deep throttling, and in-flight restart.

Development began in 2011. The first completed engine appeared in 2017, and the BE-4 made its first orbital flight aboard Vulcan Centaur in January 2024.

Development and testing

Blue Origin began developing the BE-4 in 2011 but did not publicly announce the program until September 2014. That month, United Launch Alliance selected the engine for the launch vehicle that became Vulcan Centaur. Two BE-4 engines would replace the Russian-built RD-180 used by the Atlas V. The early program and its planned 2.45 MN thrust level were described by The Space Review.

By April 2015, development had been divided into two parallel efforts. One tested full-scale powerpacks containing the valves and turbopumps that supplied propellant to the engine. The other tested subscale injector hardware. Blue Origin had completed more than 100 component tests by September 2015. A powerpack test device exploded during this period, after which the company constructed two larger redundant test stands.

The first complete BE-4 was assembled in March 2017. The engine completed its first hot-fire test in October 2017, operating for three seconds at 50 percent thrust. A March 2018 test reached 65 percent thrust for 114 seconds. Testing reached full power in August 2019.

United Launch Alliance formally confirmed the BE-4 as the Vulcan engine in September 2018. In July 2020, Blue Origin delivered the first pathfinder engine for Vulcan integration testing. This was development hardware rather than a flight-qualified engine, as reported by SpaceNews.

The first two flight engines were delivered for integration with Vulcan in October 2022. Qualification testing was completed by the end of April 2023. On 30 June 2023, another BE-4 exploded ten seconds into a test and damaged the test stand.

Flight service and continued development

Two BE-4 engines powered the first Vulcan Centaur launch on 8 January 2024. The engines completed their work successfully and sent the vehicle toward its planned trajectory. This was the first flight of the BE-4.

Seven BE-4 engines powered New Glenn on its first launch on 16 January 2025. They operated during the ascent, although the reusable first-stage booster was lost during atmospheric re-entry.

In November 2025, Blue Origin announced an improved maximum sea-level thrust of 2,847 kN. During a New Glenn static-fire test in May 2026, an explosion destroyed the rocket. Blue Origin later traced the event to a valve in one of its BE-4 engines.

Design

Combustion system

The BE-4 burns liquefied methane and liquid oxygen. It uses a single oxygen-rich preburner in a staged-combustion cycle. Hot gas from the preburner drives one turbine connected to both the methane and oxygen pumps before entering the main combustion chamber.

The combustion chamber is regeneratively cooled. Propellant circulates through cooling passages around the chamber before combustion, carrying heat away from the chamber walls.

Propellant and pressurization systems

The engine uses hydrostatic bearings in its turbopumps instead of conventional ball or roller bearings. A thin film of fluid supports the rotating components. This arrangement was selected to reduce wear and support repeated use.

Methane also permits autogenous tank pressurization. In this system, heated gaseous propellant pressurizes the vehicle tanks, reducing the need for a separate stored gas such as helium.

Reusability and control

The BE-4 was designed for as many as 100 flights. It can be restarted in flight through a head-pressure start of the turbine. Testing demonstrated throttling to at least 40 percent power, followed by a rapid return to full thrust. These features support vertical landing and reuse of the New Glenn first stage.

Operational history

The BE-4 entered flight service with United Launch Alliance on Vulcan Centaur in January 2024. Vulcan uses two engines on its first stage. The engine began flying on Blue Origin vehicles in January 2025, when seven units powered the first New Glenn through ascent.

Blue Origin operates separate production flows for engines intended for Vulcan and New Glenn. The engine remains in production for both launch systems.

Variants

• BE-4: Sea-level engine used by Vulcan Centaur and New Glenn. The original production rating was approximately 2,460 kN, followed by an improved rating of 2,847 kN announced in 2025.
• BE-4U: Proposed vacuum-optimized upper-stage version for an early New Glenn configuration. Blue Origin abandoned this arrangement and selected vacuum-optimized BE-3 engines for the second stage.

Operators

• Blue Origin: Uses seven BE-4 engines on the reusable first stage of each New Glenn launch vehicle.
• United Launch Alliance: Uses two BE-4 engines on the first stage of each Vulcan Centaur launch vehicle.

Specifications (improved BE-4)

General characteristics

• Type: Reusable liquid-propellant booster engine
• Manufacturer: Blue Origin
• Fuel: Liquefied methane
• Oxidizer: Liquid oxygen
• Cycle: Oxygen-rich staged combustion
• Turbomachinery: Single turbine driving the fuel and oxidizer pumps
• Cooling: Regeneratively cooled combustion chamber

Performance

• Sea-level thrust: 2,847 kN (640,000 lbf)
• Throttle range: 40–100 percent
• Chamber pressure: 14 MPa (140 bar)
• Specific impulse: Approximately 340 seconds
• Gimbal range: ±5 degrees
• Vulcan burn duration: 299 seconds
• New Glenn ascent burn duration: 191 seconds