A critical test of a powerful new rocket booster designed for NASA’s Space Launch System (SLS), the backbone for the Artemis program aiming to return humans to the Moon, encountered an unexpected anomaly. This test, simulating a full launch burn, is a vital step in developing more capable engines for future deep space missions, proving that even in advanced rocketry, testing is where engineers learn and refine designs. Key takeaways include the test’s purpose in validating an upgraded booster, the specific anomaly observed near the end of the burn, and how the collected data is crucial for refining the design.
Building rockets is a bit like stress-testing a bridge before anyone drives on it. You push it to its limits to find any weaknesses. That’s essentially what happened on June 26 at Northrop Grumman’s facility in Promontory, Utah. Engineers were conducting a “static fire” test – firing a giant rocket engine while it’s bolted down – for about two minutes, mimicking the incredible forces it would experience during a launch.
The focus was on the Demonstration Motor-1 (DM-1), the first full-scale test of Northrop Grumman’s Booster Obsolescence and Life Extension (BOLE) upgrade. Think of BOLE as a next-generation engine designed to replace and improve upon the solid rocket boosters currently used on SLS. This enhanced motor promises greater lifting power, over 10 percent more performance than the current boosters, essential for heavier payloads on future Artemis missions.
As the fiery test neared its conclusion, around 100 seconds into the burn, observers witnessed an unusual outburst of flames erupting from the top of the engine’s nozzle. A few seconds later, an even larger burst emerged from the main exhaust plume. While the primary burn seemed to continue as planned until the end, the visual anomaly was noticeable enough to elicit reactions from the test operators.
Powerful flame from a large solid rocket booster during a static fire test for NASA's Space Launch System (SLS) and Artemis program.
“While the motor appeared to perform well through the most harsh environments of the test,” said Jim Kalberer, Northrop Grumman’s vice president of propulsion systems, in a statement, “we observed an anomaly near the end of the two-plus minute burn.” He stressed that for a new design of this magnitude – the largest segmented solid rocket booster ever built – tests like this are invaluable for collecting data and iterating on the design.
The Space Launch System is NASA’s super heavy-lift rocket foundational to the Artemis program, which aims to land astronauts on the Moon again and eventually send humans to Mars. SLS cleverly utilizes upgraded systems from the Space Shuttle era. Its massive core stage and RS-25 engines are direct descendants of shuttle technology, as are the five-segment solid rocket boosters that provide the initial, tremendous push off the launch pad.
These trusted, heritage boosters powered the first Artemis mission, Artemis 1, and are planned for upcoming missions like Artemis 2 and Artemis 3. However, as components become harder to source (“obsolete”), and as NASA looks to increase SLS capability for missions like Artemis 9 and beyond (on the planned SLS Block 2), upgrades like the BOLE motor become necessary.
Diagram illustrating the segmented design and internal components of a solid rocket booster used on NASA's SLS rocket for Artemis missions.
The BOLE engines feature newly manufactured parts, lightweight carbon fiber composite casings, and optimized propellant efficiencies. Thursday’s test gathered data from over 700 sensors, measuring everything from temperature and pressure to structural integrity, as the booster generated over 4 million pounds of thrust. This wealth of information is now being analyzed by engineers.
Discovering anomalies during testing isn’t necessarily a setback; it’s part of the process. It’s far better to find potential issues on a test stand than during an actual launch. The data from this DM-1 test will guide Northrop Grumman and NASA in refining the BOLE design, ensuring maximum reliability and performance for future flights. However, the path forward for the BOLE booster, and indeed the later versions of SLS it’s designed for, faces broader uncertainty. NASA’s proposed budget for 2026 includes language suggesting potential changes or cancellation for the SLS program after Artemis 3. This makes the successful development and testing of components like BOLE critical for demonstrating capability and securing the program’s future trajectory, whatever it may be.
Ultimately, tests like the DM-1 static fire, even with unexpected moments, are crucial steps in the complex journey of developing rockets capable of sending humanity further into space than ever before. Every test provides lessons that push the boundaries of engineering and bring us closer to our ambitious exploration goals.
