A Blue Origin BE-4 engine arrived at ULA's factory in Decatur, Ala. Credit: ULA via Twitter

WASHINGTON — Blue Origin this week delivered a BE-4 rocket engine to United Launch Alliance. ULA will use two BE-4s in the main stage of its future Vulcan Centaur rocket

In a celebratory tweet July 1 with the hashtag #CountdowntoVulcan ULA announced that a BE-4 engine arrived at its rocket factory in Decatur, Alabama.

“The engine delivered is the first pathfinder engine to be mated with the Vulcan Centaur and will support ULA’s testing,” a Blue Origin spokesperson told SpaceNews. “We are planning on delivering the second engine in July.”

A pathfinder is a development engine.  Blue Origin has not said when a flight-qualified engine will be delivered.

The BE-4 uses liquid oxygen and liquefied natural gas propellants and generates 75,000 horsepower. The engine was developed by Blue Origin with some financial support from ULA.

ULA announced in September 2018 its selection of the BE-4 as Vulcan’s main engine. The vehicle was projected to make its first launch in 2020 but engine delays set ULA back.

ULA set a 2021 target to fly its first Vulcan Centaur mission and needs two production-quality engines to build the launch vehicle for that mission. Flying Vulcan Centaur in 2021 is an imperative for ULA as it tries to win one of two contracts that the U.S. Space Force will award this summer to launch dozens of national security satellites between 2022 and 2027.

According to sources, frustration has been mounting at ULA as the company’s future is tied to the success of Vulcan Centaur and there is no room for error when it comes to the main engine.

ULA CEO Tory Bruno told SpaceNews in February that most of Vulcan’s major components except the main engine are in production. He called the engine “the hardest part” and said Blue Origin was doing its best to stay on track and overcome “big technical challenges this past year.”

Bruno said the BE-4 is a “powerful and complicated machine” that can power a cruise ship. “It’s a pretty big engineering feat.”

Sandra Erwin writes about military space programs, policy, technology and the industry that supports this sector. She has covered the military, the Pentagon, Congress and the defense industry for nearly two decades as editor of NDIA’s National Defense...