NASA has shown a keen interest in 3D printed rocket components lately with a series of tests that have had considerable success, with printed parts in test firings working as well as those made by conventional methods. In the latest test firing on August 22, the largest 3-D printed rocket engine component yet tested by NASA withstood ten times the thrust previously generated by an engine using printed components.
NASA has hopes for the 3D printing process in terms of facilitating the manufacture of parts in space as well as reducing the cost of designing and building rocket engines on Earth. Having shown that such components can not only be made, but can work under test conditions, the agency is now striving to make the components larger and more powerful.
The injector component used in most recent test was built by Directed Manufacturing Inc. of Austin, Texas, though NASA owns the design. It was built by using a laser to selectively melt layers of nickel-chromium alloy powder. This allowed the engineers to make an injector with 28 elements for channeling and mixing propellants inside the rocket engine.
Previous 3D printed injectors have been small, but this one is similar to those designed for the RS-25 engines that will power the giant Space Launch System (SLS) rocket booster intended for launching the manned Orion spacecraft and deep space missions.
One significant point about the new injector is that the printing process allowed it to be redesigned in two parts, instead of the 115 in the original, which greatly reduced costs.
"We took the design of an existing injector that we already tested and modified the design so the injector could be made with a 3-D printer," says Brad Bullard, the propulsion engineer responsible for the injector design. "We will be able to directly compare test data for both the traditionally assembled injector and the 3-D printed injector to see if there's any difference in performance."
In the test firing, the injector burned liquid oxygen and hydrogen gas. The rocket firing generated a record 20,000 pounds of thrust, which is ten times more than has been produced by a 3D printed injector, and withstood temperatures of 6,000⁰ F (3,300⁰ C) and pressures of 1,400 psi. Preliminary data indicates that the injector worked perfectly.
"This entire effort helped us learn what it takes to build larger 3-D parts – from design, to manufacturing, to testing," says Greg Barnett, lead engineer for the project. "This technology can be applied to any of SLS's engines, or to rocket components being built by private industry."
NASA will now inspect the data and the component to learn more about how it fared during the firing.