ULA orders 116 Aerojet Rocketdyne engines for Vulcan’s upper stage

Aerojet Rocketdyne announced April 11 it has received an order from United Launch Alliance for 116 engines for the upper stage of ULA’s Vulcan Centaur rocket. Aerojet said this was the company’s largest ever contract for the RL10 engine. The large purchase of rocket engines comes on the heels of Amazon’s announcement April 5 that it selected Arianespace, Blue Origin and ULA to launch up to 3,236 satellites for its Project Kuiper broadband constellation. CEO Tory Bruno said ULA plans to fly Vulcan’s first mission late in 2022. Winning the Amazon deal would more than double the annual rate of Vulcan launches to as many as 25 per year, and ULA will ramp up production to meet the demand, Bruno said last week at the Space Symposium. ULA’s engine choice for Vulcan’s upper stage dates back to 2018 when it selected a variant of the RL10, the same engine used to power the upper stages of ULA’s legacy rockets Atlas 5 and Delta 4 Heavy. Over the past 60 years, more than 450 RL10 engines have flown on various ULA heritage vehicles. Due to a congressional mandate to end the U.S. military’s reliance on the Russian RD-180 rocket engine used in the Atlas 5’s first stage, ULA in 2015 announced it would build Vulcan Centaur as its next-generation rocket and selected Blue Origin’s BE-4 engine for the first stage. Each Vulcan Centaur upper stage will use two RL10C-X engines.

A Vulcan Centaur upper stage powered by two RL10 engines. Credit: Aerojet Rocketdyne

Aerojet said the RL10C-X is a variant of the RL1o developed for Vulcan Centaur that will “increase the use of additive manufacturing and introduce other advanced technologies to improve the quality, reliability, affordability and performance.” 

The RL10C-X uses a 3D-printed main injector and main combustion chamber, and has a 94-inch monolithic lightweight composite nozzle. According to Aerojet, the specific impulse, or Isp, of the RL10C-X is 461 seconds, which “puts it near the very top of the RL10 engine family in terms of performance. Specific impulse measures the amount of thrust generated by a rocket engine per unit of propellant consumed per second.

The engine is made at Aerojet Rocketdyne’s facility near West Palm Beach, Florida. The RL10 also powers the upper stage of NASA’s Space Launch System.

During a meeting with reporters at the Space Symposium, Bruno said one of his key “supply chain” concerns is building enough rocket engines for Vulcan to meet the projected demand.

“We are most concerned about the things that are the most complicated to build and take the most time,” he said. “Those are rocket engines and rocket motors. So Blue Origin, Aerojet Rocketdyne and Northrop Grumman are the key places we’ll focus on.” Northrop Grumman supplies Vulcan’s strap-on solid boosters.