Reflecting on the extensive work carried out by the NESC over two decades, Director Tim Wilson has pinpointed three pivotal assessments from the 1,200 undertaken. These selections stand out for their profound potential to enhance human life and propel the NESC’s mission forward. Wilson elaborates on the far-reaching implications of these projects.
**2013-2019: Enhancing Safety Through Frangible Joint Analysis**
In response to a request from the Commercial Crew Program, the NESC embarked on a rigorous empirical investigation into frangible joints, crucial for ensuring the safety of human spaceflight. “These joints are integral to numerous programs, and understanding their design margins has been key to safeguarding flight crews and securing mission success,” Wilson explains. These joints are designed for clean separation of launch vehicle stages and payload fairings. Through conducting over 140 tests on various designs and analyzing more than 100 million lines of data, the NESC has been instrumental in refining models, enhancing design sensitivity, and improving reliability estimates. This foundational work has significantly contributed to subsequent evaluations for major programs like the Space Launch System, Orion, and Launch Services. Moreover, the establishment of the FJ Working Group has fostered a technical community within the agency, ensuring a proactive approach to understanding and mitigating risks associated with frangible joint technologies.
**2018-2021: Unraveling the Mystery of Pilot Breathing Issues**
Faced with a surge in physiological episodes among pilots of the U.S. Navy’s F/A-18 fleet, leading to mission aborts, the cause remained elusive. “It was a challenging issue, but our team managed to provide compelling insights,” Wilson remarks. Over three years, the NESC’s Pilot Breathing Assessment (PBA) team developed innovative instrumentation to monitor pilot physiological states and their interaction with aircraft life support systems. By conducting tests with NASA pilots in instrumented F/A-18 and F-15 aircraft, equipped with advanced sensor systems, the team was able to identify interactions that could negatively affect cognitive and physiological functions. With over 100 flights and 250 million data points, the team discovered mismatches in breathing pressures and airflows, which increased pilots’ efforts to breathe adequately. The findings not only advance aviation safety but also have direct implications for NASA’s fleet and the International Space Station, enhancing human system integration in modern aircraft.
**2020-2023: Addressing the Unconservatism in COPV Analysis**
The NESC has dedicated significant effort to decipher the complex behaviors of composite overwrapped pressure vessels (COPVs), widely used in spaceflight. A recent investigation revealed a critical oversight in the damage tolerance analyses of COPV liners using linear-elastic fracture mechanics (LEFM), especially concerning the effects of autofrettage (AF). AF involves subjecting a COPV to high pressures to pre-stress the inner surfaces, thereby reducing susceptibility to operational stresses. The team discovered that treating the AF cycle separately from subsequent elastic cycles in LEFM analysis resulted in overly optimistic life predictions. This was because cracks that formed during compressive cycles post-AF remained open, allowing a greater stress range to contribute to crack growth. By providing corrective measures to NASGRO, the software used for fracture and fatigue crack growth analysis, the team has made significant strides in ensuring the safety of future crew members. “I am confident that the enhancements made by our team will play a crucial role in safeguarding crew members, who may never realize the extent to which these improvements have contributed to their safety,” Wilson asserts, highlighting the broader impact of this work.