Full-duration test of Aeon 1 – 3D printed rocket engine.

Relativity Space said Monday that the company has successfully completed a full-duration test-firing of its Aeon 1 rocket engine, running it at full power for 187 seconds.
The test at NASA’s Stennis Space Center in Mississippi took place with all of the engine’s key components—including turbopumps, injector, and combustion chamber—operating in a flight-like configuration. Surprisingly, the company met this milestone ahead of schedule—Relativity had been targeting completion of this mission duty cycle test before the end of 2020.

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

Moving fast

It is safe to say that Relativity, which aims to 3D print nearly the entirety of its rockets, is moving fast.  David Giger—who is leading development of the company’s Terran 1 rocket—talked about the ongoing tests of the company’s thrust-chamber assembly. Relativity, he said, would begin full-scale engine tests that summer.

Then the pandemic hit and life ground to a halt. 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 stand, NASA is working to perform a hot-fire test of its Space Launch System core stage. Originally, the agency had targeted July, but citing the double whammy of COVID-19 and weather delays, the agency is targeting no earlier than the end of 2020 for this test.

Because of all this, and the near-universal slippage in nearly all rocket development projects, I did not expect Relativity Space to begin test-firing the Aeon 1 engine this summer. But the company has done so—starting in late August. And remarkably, just 56 days later, it moved from tests at low power, lasting a few seconds, to a full-power, long-duration firing of a brand-new engine. Through early November, Relativity has test-fired the engine a total of 400 times, Giger said.

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

Larger rocket

The successful tests augur well for the ongoing development of the Terran 1 rocket, which represents a challenge as this rocket will now be larger than originally anticipated. In 2019, due to customer requests, Relativity resized its rocket to nearly double the available volume for payloads. It expanded the diameter of the fairing at the top of the rocket to 3 meters and height to 7 meters. While this is smaller than the fairing used in big rockets like the Falcon 9, in the class of “small satellite” launch vehicles it is quite large.

Relativity’s move to a larger fairing necessitated a more powerful engine with a gas generator cycle. The original Aeon engine had a thrust of 17,000 pounds at sea level, and the new version boosts the power considerably to 23,000 pounds. And now the company has been able to validate this larger, more powerful engine design.

The Terran 1 rocket, with a lift capacity of 1.25 tons to low Earth orbit, is powered by a first stage with nine Aeon engines. Success with the engine testing gives the company confidence that it can hit its target 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 happen 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 being printed now,” Dunn said. “I absolutely see key milestones along with the engine lining 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 get to orbit faster and validate its launch system. In the meantime, Relativity has been accruing customers for its $12 million launch vehicle, including a high-profile Lockheed Martin mission to demonstrate cryogenic storage of hydrogen in space.

“We’ve been super-humbled and excited about the customer interest in Terran 1,” Ellis said. “We’re not going to talk about specific contract numbers, but you could definitely say we’re one of the most pre-sold rockets in history of spaceflight.”

Credit : Arstechnica.com