In a milestone for 3D printing, a rocket engine with a 3D-printed component helped put a US Space Force early warning satellite into orbit last week. The RL10 has been a mainstay of American spaceflight. The fact that its manufacturer, Aerojet Rocketdyne, would use 3D printing to make even a minor part of the RL10, much less the core main injector, shows how far additive manufacturing has come.

Why 3D Printing Makes Better Rocket Engines

When it comes to extreme conditions, there is nothing like the environment of a rocket launch. Liquid hydrogen and liquid oxygen at -423°F enter the engine’s injector where they mix and flow into the thrust chamber. The combustion gases reach temperatures exceeding 5,000°F and shoot out of the rocket’s nozzle. Each RL10 generates around 24,000 pounds of thrust and intense vibrations but must still relight after long periods in microgravity.

To withstand these conditions, rocket engines have complex designs that require a lot of manual labor to produce in low volumes. And that is what makes additive manufacturing so attractive to companies like Aerojet Rocketdyne which wants to go beyond the 3D-printed core main injector that flew on last week’s launch.

“By producing these components with 3-D printing, we expect to reduce lead time by 35-50%, and overall engine cost by 25-35%,” Aerojet Rocketdyne CEO Eileen Drake said after an earlier test fire.

The RL10C-X development program uses 3D printers to make injectors, nozzles, and thrust chambers. Traditionally, thrust chambers are made from an array of drawn nickel-alloy tubes that highly skilled workers spend months brazing together.

Using a copper alloy and a selective laser melting 3D printer, Aerojet Rocketdyne made a thrust chamber with only two primary parts in less than a month. Moreover, the thrust chamber has better heat transfer properties thanks to a 3D design that could never have been produced using traditional methods.

“We continue to look for ways to insert additive manufacturing into our liquid rocket engine designs to not only reduce their cost, but to open up creative design spaces that the additive manufacturing process enables,” Drake said.

Seal of Approval for a Space Age Workhorse

Aerojet Rocketdyne executive Jim Maser said after the launch that their investment in additive manufacturing “enabled us to provide more affordable RL10 engines that deliver the same performance and reliability our customers have come to expect.”

More than 475 RL10 rocket engines have launched into space since 1963. Early flights in the Apollo Program used upper stages built around the RL10. NASA’s Viking landers and the Voyager spacecraft were pushed into interplanetary space by the RL10-powered Centaur upper stage. Whenever an Atlas V or Delta IV puts a national security payload into orbit, RL10s are providing the final thrust to get them there.

You do not mess with that kind of track record which is why the first flight of 3D-printed rocket parts is such a milestone.