The RS-25, built by L3Harris’ Aerojet Rocketdyne division, is one of four engines that make up the SLS core stage. Together, they generate more than 2 million kilograms of thrust at lift-off, making the SLS the most powerful rocket ever developed by NASA.
The latest test, carried out at NASA’s Stennis Space Center in Mississippi, saw the engine fire for more than 500 seconds, roughly the same duration it would burn during launch – reaching 111 per cent of its rated power level. The successful test demonstrated the engine’s performance and reliability, confirming its readiness for integration into the Artemis V launch vehicle.
“As we approach America’s 250th anniversary next year, it’s fitting that we’re advancing the Artemis program, which captures the pioneering spirit of our nation,” said Kristin Houston, president of space propulsion and power systems at L3Harris. “By leveraging advanced manufacturing techniques, we’re delivering engines that are more cost-effective while maintaining the power and reliability needed to propel Artemis missions to the Moon and beyond.”
The RS-25 has a long heritage, having originally served as the Space Shuttle Main Engine (SSME). Between 1981 and 2011, it powered 135 shuttle missions before being adapted for NASA’s next-generation exploration architecture.
When the shuttle program ended, NASA retained 16 flight-proven RS-25s for future use. These engines have since been upgraded with modern avionics and controls to support the first four Artemis missions.
Starting with Artemis V, NASA will begin flying newly produced RS-25 engines, designed specifically for the SLS and built using additive manufacturing (3D printing) and other advanced techniques.
These innovations have reduced production costs by around 30 per cent compared to the shuttle-era engines, while maintaining the same thrust and reliability standards. The successful test marks the second flight-ready RS-25 to emerge from L3Harris’ modernised production line – a significant milestone for the program.
Under the Artemis program, NASA aims to establish a sustained human presence on and around the moon later this decade, with the Artemis V mission set to deliver astronauts and cargo to the Gateway Lunar Space Station and continue building the infrastructure needed for future Mars expeditions.
The Space Launch System, combined with the Orion spacecraft and commercial landers, forms the backbone of this long-term effort to extend human exploration deeper into space.
Australia is contributing to Artemis through the Australian Space Agency, which is supporting lunar surface technologies, autonomous systems, and communications capabilities.
As NASA and its international partners look ahead to the next era of space exploration, the RS-25 remains a powerful link between the legacy of the space shuttle and the ambitions of deep-space flight.
“This engine has taken astronauts to low Earth orbit,” Houston said. “Now, it will help take humanity back to the Moon – and one day, to Mars.”