On June 26, 2023, a new version of the solid rocket booster being developed for NASA's Space Launch System (SLS) encountered an unexpected anomaly during a test firing at Northrop Grumman's test site in Promontory, Utah. This test marked the first demonstration of the Booster Obsolescence and Life Extension (BOLE) version of the five-segment solid rocket booster.
During the test, the solid rocket booster was fixed in a horizontal position and ignited for a duration of just over two minutes, simulating conditions similar to those it would face during an actual launch. Approximately 100 seconds into the test, observers noted exhaust venting from the side of the nozzle, which was followed by the scattering of debris in the area, as documented in NASA's live webcast of the event. A moment of surprise was audible on the broadcast, with one viewer exclaiming, “Whoa!” as the debris was expelled.
Despite the incident, the motor continued to operate and burn for the remaining duration of the test. In a statement issued shortly after the test, Jim Kalberer, vice president of propulsion systems at Northrop Grumman, acknowledged the anomaly, stating, “While the motor appeared to perform well through a harsh burn environment, we observed an anomaly near the end of the two-plus minute burn.” However, neither NASA nor Northrop Grumman officials provided further details regarding the specifics of the anomaly during the webcast.
Kalberer emphasized the significance of the test, noting that the company is “pushing the boundaries of large solid rocket motor design.” The BOLE design represents a significant advancement, replacing the traditional steel casings used in shuttle-era solid rocket motors with innovative carbon fiber composite designs. Furthermore, this new version incorporates a new propellant formulation and other technological advancements, resulting in a performance increase of over 10%, enabling the SLS to carry an additional five metric tons of payload for upcoming lunar missions.
Despite the promising developments, the future of the BOLE design remains uncertain. NASA's fiscal year 2026 budget proposal suggests the potential cancellation of the SLS program after the Artemis 3 mission. Although a provision in the Senate version of a budget reconciliation bill proposes funding for two additional SLS missions through Artemis 5, it does not clarify the long-term future of the vehicle beyond that point.
This incident marks the second occurrence in less than a year where a solid rocket booster manufactured by Northrop Grumman faced a nozzle issue. During the second launch of United Launch Alliance’s Vulcan rocket in October 2024, one of the two GEM 36XL solid rocket boosters—significantly smaller than the BOLE—lost its nozzle. While this affected the booster’s performance, it did not hinder Vulcan from completing its mission. A manufacturing defect in one of the internal parts of the nozzle was identified as the cause, leading to fixes confirmed in a test firing at Northrop's site in February.
As advancements in rocket technology continue, the implications of these tests and designs will play a critical role in the future of space exploration, particularly for missions aimed at returning humans to the Moon and beyond.
