New Fuzing Enhancements for the GBU-57: What They Mean for U.S. Military Strategy

The U.S. Air Force (USAF) is actively pursuing enhancements to the GBU-57/B Massive Ordnance Penetrator (MOP), a 30,000-pound class bunker-busting bomb designed to neutralize deeply buried and fortified targets. Recent developments have centered on the integration of advanced fuzing systems, particularly a new “smart fuze,” intended to improve the weapon’s precision and adaptability in complex operational environments.

B-2 drops GBU-57. USAF

The GBU-57/B MOP is a specialized munition developed to address the challenge of targeting hard and deeply buried targets (HDBTs), such as underground military facilities and nuclear infrastructure. The weapon is composed of several key components: the BLU-127/B warhead, the KMU-612/B tail kit (which includes GPS-assisted inertial navigation), and the fuzing system. The USAF’s current efforts focus on upgrading the fuzing mechanism to enhance the bomb’s lethality and reliability, particularly in scenarios where the exact depth or configuration of the target is uncertain.

In 2024, the Air Force tested a new smart fuze known as the Large Penetrator Smart Fuze (LPSF), which was developed under the LPSF Quick Reaction Capability program initiated in 2018. This program was launched in response to an urgent operational requirement to improve the MOP’s effectiveness against evolving threats. The LPSF is designed to optimize detonation timing after the bomb has penetrated the ground, thereby increasing the likelihood of neutralizing deeply buried targets. This capability is particularly critical when intelligence on the target’s structure is limited or imprecise.

The integration of the LPSF into the MOP system required significant testing and validation. According to the Office of the Director, Operational Test and Evaluation (DOT&E), two full-scale tests were conducted in fiscal year 2024 to address integration issues with the B-2 Spirit stealth bomber, the only aircraft currently certified to deploy the MOP operationally. These tests aimed to ensure that the new fuze could be effectively employed within the constraints of the B-2’s bomb bay and operational parameters. The second of these tests included the use of the LPSF in a full-scale testbed, marking a significant milestone in the fuze’s development.

Despite these advancements, the program has faced challenges, particularly related to funding and scheduling. The DOT&E report noted that subscale lethality testing was reduced by approximately 50% due to budget reallocations and increased testing costs. Certification tests originally planned for fiscal years 2021 and 2022 were delayed to 2023 and 2024. These delays have prompted recommendations for improved funding stability and resource allocation to avoid further setbacks.

In parallel with the fuze development, the Air Force Life Cycle Management Center (AFLCMC) issued a contracting notice in July 2025 seeking industry input on various aspects of MOP production and sustainment. This includes the development and integration of new fuzes, production of KMU-612E/B tail kit variants, and support for other unspecified MOP components. The notice also emphasizes the need for obsolescence support and validation, highlighting the Air Force’s intent to maintain and modernize its existing MOP inventory.

The total number of MOPs in the USAF’s arsenal remains classified, but historical data suggests that the inventory is relatively limited. As of 2015, Boeing had delivered at least 20 units, and recent reports indicate efforts to expand production capacity, including the establishment of new facilities in Oklahoma. The B-21 Raider, the next-generation stealth bomber, is expected to be capable of carrying the MOP, although it may be limited to a single bomb per sortie due to size and weight constraints.

The pursuit of improved fuzing technology for the GBU-57/B reflects broader strategic considerations. As adversaries increasingly invest in hardened underground facilities, the ability to effectively target and destroy such sites becomes a critical component of deterrence and operational capability. The MOP, with its enhanced smart fuze, represents a key asset in this domain, offering the potential to hold at risk a wider array of high-value targets.

The USAF’s efforts to upgrade the GBU-57/B MOP with advanced fuzing systems underscore the evolving nature of precision strike capabilities. While technical and budgetary challenges persist, the integration of smart fuzes like the LPSF marks a significant step toward enhancing the effectiveness of one of the most powerful conventional weapons in the U.S. arsenal. Continued investment in testing, production, and sustainment will be essential to ensure that the MOP remains a viable tool for addressing future threats in an increasingly complex strategic environment.