Relativity’s 3D printed engine has completed a mission duty cycle test

Relativity Space said Monday that the company has successfully completed a full-life firing test of its Aeon 1 rocket engine, running it at full power for 187 seconds.

Testing at NASA’s Stennis Space Center in Mississippi took place with all key engine components, including turbopumps, injector and combustion chamber, operating in a flight-like configuration. Surprisingly, the company has achieved this milestone forward of the program: Relativity aimed to complete this mission work cycle test before the end of 2020.

“Despite the coronavirus, we are on track,” Relativity CEO Tim Ellis said in an interview. “The test of the mission’s duty cycle engine is actually two months ahead of schedule. So I think it really demonstrates how 3D printing’s approach to building a rocket is blazing fast.”

Move fast

It’s safe to say that Relativity, which aims to 3D print nearly all of its rockets, is moving fast. I visited the company’s engine testing facilities in February, when the pandemic hadn’t stopped that kind of trip yet. At the time, David Giger, who is leading development on the company’s Terran 1 rocket, spoke about the company’s ongoing thrust chamber assembly tests. Relativity, he said, would begin full-scale engine testing that summer.

Then, the pandemic struck. Life has stopped. Stennis was effectively closed for a few weeks due to the virus and, later that summer and fall, would be affected by no fewer than six tropical storms and hurricanes. On a nearby test bed, NASA is working to perform a hot fire test of its main stage of the space launch system. Initially, the agency targeted July, but citing COVID-19’s double hit and weather delays, the agency targeted no earlier than the end of 2020 for this test.

Due to all of this and the near-universal slip in nearly every rocket development project, I didn’t expect Relativity Space to start testing the Aeon 1 engine this summer. But the company, in fact, did, starting in late August. And surprisingly, just 56 days later, it went from low-power, seconds-long tests to full-power, long-lasting firing of a brand new engine. As of early November, Relativity has tested the engine a total of 400 times, Giger said.

Ellis attributed the success of the Aeon 1 engine to its team of engineers and technicians, the software’s prediction models, and the ability to quickly iterate and 3D print new parts as needed. What is perhaps most impressive is that Relativity has stayed true to its timeline despite having to invent many technologies needed to additively produce nearly the entirety of its rocket.

Bigger rocket

Successful testing bodes well for the ongoing development of the Terran 1 rocket, which presents a challenge as this rocket will now be larger than originally anticipated. In 2019, due to customer demands, Relativity scaled its rocket to nearly double the volume available for payloads. It expanded the diameter of the fairing at the top of the rocket to 3 meters and the height to 7 meters. Although this is smaller than the fairing used in large rockets like the Falcon 9, in the “small satellite” launch vehicle class it is quite large.

Upgrading the Relativity to a larger fairing required a more powerful engine with a gas generator cycle. The original Aeon engine had 17,000 pounds of thrust at sea level, and the new version dramatically increases horsepower up to 23,000 pounds. And now the company has been able to validate this larger and more powerful engine design.

The Terran 1 rocket, with a lifting capacity of 1.25 tons to low Earth orbit, is powered by a first stage with nine Aeon engines. Success with engine testing gives the company confidence that it can reach its goal of launching the first Terran 1 rocket in 2021, said Zach Dunn, Vice President of Factory Development. The next step is integrated stage testing, which will take place next year, followed by a launch from Space Launch Complex-16 at Cape Canaveral Air Force Station in Florida.

“The vehicle itself for our first flight is in the press,” Dunn said. “I absolutely see the key milestones along with the engine lined up to support a flight next year on time.”

Relativity’s first launch will be a demonstration mission and will not have a paying customer on board. Ellis said this will allow the company to enter orbit faster and validate its launch system. Meanwhile, Relativity has acquired customers for its $ 12 million launch vehicle, including a high-profile Lockheed Martin mission to demonstrate cryogenic storage of hydrogen in space.

“We have been super-humbled and excited about the customer interest in Terran 1,” Ellis said. “We won’t be talking about specific contract numbers, but it could definitely be said that we’re one of the best-selling rockets in space flight history.”

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