Company Stoke Space carried out the tests of the high-efficiency engine it is developing for the first stage of the fully reusable launch vehicle. The Kent, Washington-based company announced June 11 that it had conducted a brief engine run on June 5 at a test site in Moses Lake, Washington. Designed to produce up to 100,000 pounds of thrust, the engine rose to 50% of rated thrust during the two-second test.

The aim of the test was to see how the engine starts and shuts down, Stoke’s CEO Andy Lapsa said in an interview. “All the complexity and the big risk lies in the startup and shutdown transition,” he said. “The testing period was short because the goal was to demonstrate the transition process and then return.”

The engine uses a design called full-flow staged combustion; here, both engine fuel and oxidizer (liquefied natural gas and liquid oxygen, respectively) pass through separate pre-combustion chambers before entering the main combustion chamber. This approach provides greater efficiency and longer engine life, but is more difficult to develop. It is currently only used in the Raptor engines that power SpaceX’s Starship.

Lapsa said Stoke chose this approach because it was necessary for rapid reusability of launch vehicles. “In a world of rapid reuse, you need high performance,” he said. “Full-flow combustion provides the highest possible performance under the least stressful conditions.”

Engine testing currently focuses on transient conditions during startup and shutdown. The company is building a larger test bed that will allow for longer testing, including a full proficiency testing campaign, to be completed this summer.

Stoke plans to use seven engines in the first stage of the fully reusable medium-lift launch vehicle Nova it is developing. The upper stage uses a completely different propulsion technology: liquid oxygen and liquid hydrogen fuel, with an engine housed in a heat shield that is actively cooled to allow the upper stage to return for powered landing. The company tested this system with a prototype hopper flight last September.

Lapsa said there are some similarities between turbocharging and upflow engines in areas such as the technology and analysis tools used in the engines’ turbomachines. “Other than that, it’s a completely new and different system.”

Stoke are making progress in other aspects of the car. He said avionics and flight software were used in engine tests and the company “iterated the design at the upper level.” The study is being funded by $100 million in Series B funding the company raised last October.

“All systems are working and the last big question mark I felt on my shoulders was the first stage engine and that was the engine going through the transients and coming back,” he said.

Following the shelter test last September, Lapsa said the company has an internal goal to begin orbital testing in 2025 and has a desire to accelerate this program as much as possible. He declined to provide an updated schedule after the engine test, saying it would depend on when the company can begin work on the launch pad at Cape Canaveral Launch Complex 14, which the Space Force dedicated to Stoke last year.

He noted that the tests were carried out just 18 months after the company started designing the engine. “I think over time you’ll see that purely high-speed multiple rockets will make others obsolete, I think these high-performance engines that make this mission possible will eventually make less efficient options obsolete as well,” he said. . “I think it’s an important technological mountain to climb, and I’m very excited to be on that mountain.”