The U.S. Air Force is taking early but concrete steps toward fielding a successor to its most powerful conventional bunker-busting weapon, the GBU-57/B Massive Ordnance Penetrator (MOP), as it lays the groundwork for what is now officially designated the GBU-76/B Next Generation Penetrator (NGP). A newly released contracting notice shows the service is actively preparing an acquisition and development strategy that could shape the future of deep-penetration strike capabilities for decades.
The effort comes as the Air Force simultaneously signals it will continue upgrading the existing MOP system, which gained renewed public attention after its first reported combat use during Operation Midnight Hammer against deeply buried Iranian nuclear infrastructure last year. That operation underscored both the value and the limitations of current large penetrator weapons, reinforcing the Pentagon’s long-standing requirement for improved capability against hardened subterranean targets.
According to a contracting notice posted by the Air Force Life Cycle Management Center’s Armament Directorate, Attack Division (AFLCMC/EBD), the service is conducting market research to evaluate industry capabilities for the Next Generation Penetrator program. The Air Force intends to award a Multiple Award Indefinite Delivery Indefinite Quantity (IDIQ) contract covering research, development, production, testing, and delivery of the GBU-76/B weapon system.
“All interested vendors shall submit a response demonstrating their capability to support the design, production, testing, and bed down of components and specific activities related to the development, performance and sustainment of the GBU-76/B weapon system,” the notice states, while emphasizing that the effort is currently limited to information gathering for planning purposes.
The structure of the solicitation indicates the Air Force is prioritizing a broad industrial base approach rather than immediately selecting a single prime contractor. That approach is consistent with other recent munitions modernization programs aimed at reducing supply chain risk and accelerating development timelines.
The notice outlines a wide range of anticipated technical tasks, signaling that the GBU-76/B program is expected to push the boundaries of conventional weapons engineering. Key areas include fuze development, explosive formulation, guidance integration, and system-level assembly of complete weapons.
Fuzing is a particularly critical component in large penetrator systems. Unlike standard air-delivered munitions, bunker busters must survive extreme impact conditions—often striking reinforced concrete, rock, or layered geological structures at very high velocity—before detonating at an optimal depth.
Modern penetrator fuzes are designed to “sense” internal structure after impact, sometimes counting structural voids or “floors” within hardened facilities to determine detonation timing. This capability is essential to maximizing internal damage rather than expending energy on surface or near-surface explosions. Reliability is equally important: these systems must remain functional after experiencing extreme deceleration forces and structural deformation during penetration.
The Air Force also highlights interest in integrating an “Alternate Navigation System” to supplement or replace traditional GPS-dependent guidance. This reflects growing concern about operations in contested environments where GPS signals may be degraded, jammed, or entirely denied.
The service has previously indicated that it is exploring advanced Guidance, Navigation & Control (GNC) technologies capable of delivering precision performance in GPS-contested environments. This marks an evolution from earlier penetrator designs, which relied heavily on GPS-aided inertial navigation systems.
The current GBU-57/B Massive Ordnance Penetrator uses a tail-mounted guidance package combining GPS and inertial navigation to achieve high-precision targeting. While effective, the system’s reliance on satellite navigation is increasingly viewed as a vulnerability in modern high-end warfare scenarios.
For the GBU-76/B, the Air Force appears to be prioritizing resilience against electronic warfare and improved terminal accuracy, especially against small or deeply buried aim points such as ventilation shafts, access tunnels, or hardened entry points.
Operational experience is clearly shaping requirements. During Operation Midnight Hammer, U.S. B-2 stealth bombers reportedly dropped multiple MOPs in rapid succession on narrow target points at Iran’s Fordow nuclear site. The tactic involved sequential strikes aimed at progressively penetrating hardened underground infrastructure, demonstrating both the power and precision limitations of existing systems.
Each B-2 Spirit aircraft can carry only two MOPs, constraining the volume of ordnance available per sortie. The operation underscored the importance of accurate first-pass targeting, as repeated strikes are required to achieve full penetration against deeply buried facilities.
The engagement reinforced the value of extreme precision, especially when targeting small entry points leading to large subterranean complexes. It also highlighted logistical constraints inherent in deploying very large penetrators from a limited fleet of stealth bombers.
Although much of the GBU-76/B’s design remains classified or undefined, Air Force planning documents suggest a warhead in the 20,000–30,000 pound class. That places it in a similar category to the GBU-57/B Massive Ordnance Penetrator, which weighs approximately 30,000 pounds and carries a BLU-127/B warhead.
However, the Air Force appears open to a broader range of configurations for the new system. Prior statements have indicated that the service is considering powered penetrator concepts, including the potential use of rocket-assisted propulsion to extend range or enhance terminal velocity.
Such enhancements could improve penetration performance by increasing impact energy, or allow the weapon to be launched from greater stand-off distances. Both options would increase survivability for delivery platforms operating in contested airspace.
The MOP is certified exclusively for use on the B-2 Spirit, and each aircraft can carry only two weapons. This creates inherent limitations in sortie efficiency when targeting hardened facilities requiring multiple penetrator strikes.
The Air Force has repeatedly indicated that any successor system should be compatible with the B-21 Raider. The B-21’s smaller payload capacity means it is unlikely to carry more than one MOP-class weapon per sortie, but its larger projected fleet size—expected to exceed 100 aircraft—would offset per-aircraft limitations.
A lighter or more compact GBU-76/B design could significantly improve flexibility across the bomber fleet, enabling broader employment options and potentially increasing magazine depth per mission package.
Despite the push toward a successor weapon, the Air Force is not retiring the GBU-57/B Massive Ordnance Penetrator. Instead, it is continuing incremental upgrades, including improvements to its tail kit, fuzing systems, and overall reliability.
Budget documentation for Fiscal Year 2027 outlines ongoing MOP enhancements and notes continued investment in stockpile replenishment following operational use. While total inventory numbers remain undisclosed, production is understood to be limited, with Boeing serving as the prime contractor responsible for assembly and integration.
The service is also investing in a new test target known as MS-34 to support validation of penetrator performance against realistic hardened structures. Such testing remains essential despite advances in modeling and simulation, particularly for weapons designed to interact with complex underground environments.
The GBU-76/B program is already drawing early industry participation. In September 2025, Applied Research Associates, Inc. announced it had received a contract to support production and delivery of full-scale NGP prototypes. The company also noted that Boeing will lead tail kit development and system integration activities.
This dual-industry structure reflects a continuation of the existing MOP development model, while also signaling an effort to expand competition and innovation across subsystem domains such as guidance, propulsion, and warhead design.
The broader strategic rationale behind the program is clear. The United States and its allies continue to face an expanding set of hardened and deeply buried targets globally, including missile silos, command bunkers, and subterranean air and naval facilities.
China, Russia, and North Korea have all invested heavily in underground military infrastructure, with particularly rapid expansion observed in China’s intercontinental ballistic missile silo fields and hardened command networks. These developments have intensified demand for conventional weapons capable of neutralizing deeply buried assets without resorting to nuclear options.
At present, the GBU-57/B Massive Ordnance Penetrator remains the only operational conventional weapon in the U.S. arsenal with credible capability against the most deeply hardened targets. However, intelligence assessments have long suggested that certain facilities may still be beyond its reach.
The Air Force is also pursuing a parallel capability known as the Nuclear Deterrent System-Air-delivered (NDS-A), a nuclear-armed bunker-busting concept intended for targets that exceed even advanced conventional penetrator capabilities.
This dual-track approach highlights a persistent capability gap: while advanced conventional weapons like the GBU-76/B may expand the range of feasible strike options, some targets may still require nuclear solutions due to depth, hardening, or redundancy of underground infrastructure.
The Air Force has not publicly defined a fielding timeline for the GBU-76/B Next Generation Penetrator. However, budget projections indicate that prototype development, modeling, and testing efforts are expected to continue through Fiscal Year 2028.
If development proceeds on schedule, the program could transition from prototype to production decisions in the late 2020s. Even then, early operational capability would likely emerge gradually, with initial systems supplementing rather than replacing the existing GBU-57/B Massive Ordnance Penetrator fleet.
The program remains in its foundational stage. But the combination of early contracting activity, defined subsystem requirements, and parallel modernization of legacy systems signals that the United States is preparing for a long-term evolution in its ability to defeat the world’s most hardened underground targets.
