As a national laboratory supporting the Department of Energy’s National Nuclear Security Administration, Lawrence Livermore has an enduring mission in stockpile stewardship: ensuring the safety, security, and reliability of the nation’s nuclear weapons. The cutting-edge scientific and technological capabilities needed for stockpile stewardship are enabling rapid development of advanced conventional (nonnuclear) weapons, which are increasingly part of the nation’s defense strategy.
Everything that Laboratory scientists and engineers have learned through fulfilling our stockpile stewardship assignments is being brought to bear in developing conventional munitions for the Department of Defense. There was certainly nothing conventional, though, about the approach they took to develop a conventional warhead for the U.S. Air Force. Designed to travel at very high speeds, the new warhead is encased inside a Livermore-designed aeroshell made of carbon-epoxy fiber. In 2013, the warhead was successfully detonated in a heavily instrumented test on the sled track at Holloman Air Force Base in New Mexico to determine how well it operated in simulated flight conditions exceeding Mach 3. (See Shaking Things Up for the Nation’s Defense.)
The development program showcased Livermore expertise in material sciences and engineering, high explosives, systems engineering, and computer simulation as well as Livermore’s experimental facilities. New conventional weapons systems must meet stringent performance requirements and cost constraints. On both counts, Laboratory engineers fully delivered, as they did earlier this decade in developing the BLU-129/B carbon composite bomb for the Air Force.
The five-year development effort of the new warhead gave our Air Force sponsors and others an opportunity to view the Laboratory’s capabilities in the critically important area of advanced conventional weapons. In this instance, we offered nearly the full spectrum of munitions development activities, from early warhead designs and aerodynamics simulations to high-explosive formulation and testing at the High Explosives Applications Facility (HEAF). We showed how using advanced engineering and physics codes, coupled to some of the world’s most powerful supercomputers, significantly increased the pace of development. We demonstrated a strong correlation between the results of computational simulations and those from materials, structural, and environmental tests. For example, our codes accurately predicted how candidate materials and designs would perform under extreme conditions in shaker tests. Conducted at the Laboratory’s remote testing facility, Site 300, these experiments subjected the warhead and aeroshell to severe heat, shock, and vibration. Other detonation tests were performed at HEAF, Site 300, and Eglin Air Force Base in Florida.
Using computers as a virtual test bed has become a hallmark of Livermore research, allowing us to examine problems more deeply and better understand experimental results. We can simulate exposure to extreme environments where experiments would simply be too difficult, dangerous, or expensive. Prior to the high-speed sled test, computational engineers realistically simulated the stresses and strains on the sled as well as the high temperatures surrounding the aeroshell as the sled hurtled down the track. Results from both experiments and simulations gave the engineering team confidence that the aeroshell’s structural and thermal properties would be more than sufficient for the 10-second sled test and that the warhead would detonate as predicted.
The development effort also demonstrated the Laboratory’s long-established practice of quickly assembling experts in diverse fields to form a cohesive team. For the sled test, we brought together scientists and engineers proficient in high explosives, aerodynamics, materials science and engineering, systems engineering, and supercomputing simulation. What’s more, we leveraged our close working relationship with a California-based manufacturer of carbon-epoxy aeronautical products. We worked closely with this company to significantly reduce the time and expense for developing and manufacturing the aeroshell.
I believe strongly in the Laboratory’s approach to advanced conventional weapons development, which takes advantage of all that computation has to offer. In the current era of budget constraints, our approach is rigorous yet cost-effective and ensures that materials and designs are optimized before large-scale testing is done. It reduces the number of laboratory tests and field experiments required to consider even small design changes. It also creates space for design options to converge into an innovative weapon design—one that is ready for the battlefield years earlier than was previously possible. I am confident that Livermore scientists and engineers are showing the way toward smarter, more cost-effective pathways of designing and testing complex engineering systems.