BE-4

The BE-4 is a powerful rocket engine built by Blue Origin that burns methane and oxygen to lift heavy rockets off the launch pad. It is one of the first American engines of its kind to fly, and it helped end U.S. reliance on a Russian-made engine.

Quick facts

• Maker: Blue Origin, with production in Huntsville, Alabama, and testing in Florida and originally near Van Horn, Texas.
• Fuel: liquid methane (essentially liquefied natural gas, or LNG) burned with liquid oxygen (LOX) — a combination nicknamed “methalox.”
• Sea-level thrust: about 2,460 kN (550,000 lbf) on early versions, uprated to roughly 2,847 kN (640,000 lbf) on later ones. Thrust is the pushing force the engine creates.
• Throttle range: 40 to 100 percent of full power.
• Chamber pressure: about 140 bar (14,000 kPa).
• Specific impulse (Isp): about 340 seconds — a measure of how efficiently the engine turns fuel into thrust.
• Dry mass: about 5,400 kg (11,900 lb).
• Steering: the engine can swivel (gimbal) up to 5 degrees in any direction.
• Reusability: designed for up to roughly 100 flights.

What it is and how it works

An engine like the BE-4 works by pumping its two liquid propellants into a combustion chamber, where they burn to create hot, high-pressure exhaust. That exhaust is squeezed out through a nozzle at enormous speed, and the rocket gets pushed in the opposite direction — the same reason a balloon shoots forward when you let the air out.

The clever part is how the BE-4 powers its own pumps. It uses an “oxygen-rich staged-combustion cycle.” First, nearly all of the oxygen (plus a little fuel) is burned in a smaller chamber called a preburner. The hot gas from that burn spins a turbine — a wheel of blades — and a single turbine drives both the fuel pump and the oxygen pump. Instead of throwing that gas away, the engine routes the still-energetic, oxygen-rich gas into the main chamber and finishes burning it. Almost no propellant is wasted, which is why the engine reaches such high efficiency and pressure.

The BE-4 also pressurizes its own tanks using a method called autogenous (self) pressurization: it taps off some methane, turns it to gas, and uses that to push on the tanks. This removes the need for a separate high-pressure helium system. Because the engine can throttle deeply down to 40 percent, swivel to steer, and relight in flight, it is well suited to landing and reusing a rocket booster.

Why it matters

The BE-4 is notable for combining three modern strengths in one operational engine: methane fuel, oxygen-rich staged combustion, and reusability. Methane burns cleaner than kerosene (a fuel known as RP-1) and leaves less soot, which makes a reused engine easier to inspect and fly again. Methane can also be cheaper, and in theory it could even be produced off Earth, such as from resources on Mars.

Oxygen-rich staged combustion is extremely efficient but was historically a technology mastered mainly by Russian engine makers. The BE-4 helped bring that capability to American industry. Strategically, it also ended U.S. dependence on the Russian-made RD-180 engine that once powered United Launch Alliance’s Atlas V rocket — an important national-security goal.

Where it is used

• Vulcan Centaur (ULA): uses two BE-4 engines on its first stage. It flew the engine for the first time on January 8, 2024, launching Astrobotic’s Peregrine lunar lander. A second certification flight in October 2024 again flew two BE-4 engines, leading to certification for U.S. Space Force missions.
• New Glenn (Blue Origin): a heavy-lift, reusable rocket powered by seven BE-4 engines on its first stage. It first flew on January 16, 2025.
• National security: the BE-4 replaced the Russian RD-180 as the U.S.-built first-stage engine for security launches, through Vulcan.

Note that the BE-4 is different from Blue Origin’s BE-3, a hydrogen-fueled engine that powers New Shepard and the upper stage of New Glenn.