US Air Force develops Next Generation Penetrator to replace GBU-57 MOP on B-21 Raider strategic bomber
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As reported by The War Zone on June 24, 2025, the U.S. Air Force has accelerated efforts to develop a new air-delivered munition known as the Next Generation Penetrator (NGP), which is intended to succeed the GBU-57/B Massive Ordnance Penetrator (MOP). This decision follows the first operational employment of the GBU-57/B during Operation Midnight Hammer, in which B-2 Spirit stealth bombers dropped a total of 14 MOPs on Iranian nuclear facilities. Twelve munitions were dropped on the Fordow enrichment complex, while two were aimed at Natanz.Follow Army Recognition on Google News at this link
The B-21 Raider stealth bomber, still in development, is projected to be the primary delivery platform for the NGP, although it is only expected to carry one MOP-sized munition per sortie, compared to the B-2’s capacity of two. (Picture source: US DoD)
According to the Air Force’s February 2024 contracting notice, the Next Generation Penetrator is being designed with a maximum warhead weight of 22,000 pounds and must be capable of delivering blast, fragmentation, and deep penetration effects. While the gross weight and external dimensions of the complete munition remain unspecified, the NGP will likely be smaller than the 30,000-pound GBU-57 to better align with the internal payload bay limitations of the B-21 Raider stealth bomber. Unlike the GBU-57/B Massive Ordnance Penetrator (MOP), which is an unpowered gravity bomb, the Next Generation Penetrator (NGP) may feature powered standoff capability to enable delivery from a safer distance, especially in highly contested airspaces. Integration with the B-21 is a key consideration, since the new platform is expected to replace the B-2 and carry a significantly greater share of the long-range strike mission. Currently, the B-2 is the only operational aircraft cleared to deliver the MOP, and it can carry just two per sortie, a constraint that would double the number of required aircraft if translated to the B-21.
The contracting notice also specifies stringent performance requirements for the NGP’s guidance and navigation systems. These include a terminal accuracy of CE90 within 2.2 meters, meaning the weapon must impact within 2.2 meters of the intended target at least 90% of the time, even in GPS-degraded or denied environments. This level of accuracy far exceeds that of conventional GPS-assisted Joint Direct Attack Munition (JDAM) bombs, whose error margins can increase to over 30 meters when GPS signals are unavailable. The Air Force is encouraging the integration of advanced Guidance, Navigation, and Control (GNC) systems, including technologies capable of operating autonomously and maintaining precision under electromagnetic disruption. In addition, the NGP is expected to include embedded fuze technology, with particular interest in void-sensing and floor-counting fuzes. These would allow the munition to detect when it has penetrated into internal spaces of an underground facility and detonate at the optimal point for maximum structural damage. This capability is especially vital when detailed pre-strike intelligence on facility layout and depth is limited or incomplete.
The NGP effort builds on more than a decade of analysis and past development experience. The program requirements draw on findings from the 2012 Hard Target Munitions (HTM) Analysis of Alternatives (AoA) and a 2019 excursion update. Unlike the GBU-57, which was initially developed as a rapid reaction capability outside a formal program of record, the NGP is being approached as a long-term, scalable program. It may eventually constitute a family of systems rather than a single munition, with variants tailored for different target sets and delivery platforms. The NGP is also tied to the broader Long Range Strike (LRS) system-of-systems concept, which includes the B-21 bomber and the AGM-181A Long-Range Stand-Off (LRSO) nuclear cruise missile. According to contracting documents, the Air Force plans to take delivery of around 10 subscale test articles and three to five full-scale prototypes within 18 to 24 months of contract award. The contracting process is being managed under the Eglin Wide Agile Acquisition Contract (EWAAC), and integration requirements include compatibility with the BRU-72/B release interface and 1760 connector standards. System design maturity is expected to reach a Technology Readiness Level (TRL) of 5 to 6 by the end of the prototype phase, with a goal of achieving validated performance through sled and static testing.
The GBU-57/B Massive Ordnance Penetrator, now undergoing a phaseout trajectory, remains the largest conventional bunker-buster munition in the U.S. arsenal. Weighing 30,000 pounds and measuring 20.5 feet in length, the MOP includes a BLU-127/B penetrating warhead weighing around 5,000 pounds, approximately 20% of the total munition weight. It is guided by a GPS-assisted inertial navigation system and uses specialized fuzing to survive high-speed impacts through hardened material before detonating inside a target. Its exact penetration capability is classified, but estimates suggest it can reach at least 60 meters into reinforced concrete, with some sources suggesting even greater depth. Despite its size and capabilities, the MOP has drawbacks, including its unpowered trajectory that requires bombers to fly relatively close to their targets, and its limited production rate. Recent reports suggest efforts are underway to triple or even quadruple the annual production capacity of MOPs, though the current stockpile remains small.
Operation Midnight Hammer marked the first time that MOPs were used in actual combat, after more than a decade of deterrence-oriented deployment. B-2 bombers delivered the 14 GBU-57s during night strikes between June 21 and 22, 2025, after this bomb was selected for this operation due to its precision-guided capabilities and capacity to engage deeply buried infrastructure. Satellite imagery confirmed precise impacts at both Fordow and Natanz, with visible craters indicating successful delivery, but some experts raised doubts about the overall effect. Reports from U.S. intelligence sources and foreign analysts suggest that the core of Iran’s nuclear infrastructure may have survived, particularly at Fordow, which lies about 30 meters deeper than MOP’s published penetration threshold. This perceived limitation has prompted debate about the effectiveness of even the most powerful conventional bunker-busters against well-engineered underground targets. In response, the Department of Defense emphasized that battle damage assessments were still ongoing and that early conclusions lacked full corroboration from the intelligence community. Nevertheless, lessons from this operation are reportedly being integrated into the NGP’s development process, especially as the Pentagon plans for potential future conflicts involving other deeply hardened targets, such as those found in China, North Korea, or Russia.
Bunker-buster bombs have been part of the U.S. inventory since the 1991 Gulf War, when the GBU-28 was fielded using modified artillery barrels to penetrate hardened Iraqi shelters. Since then, systems such as the GBU-37 and GBU-72/B have expanded this category, offering different levels of weight and penetration capabilities. The GBU-72/B, a 5,000-pound class precision-guided bomb, was used operationally in recent strikes against Houthi forces in Yemen. These weapons employ delayed fuzing to maximize internal structural damage after penetrating surface defenses. Bunker-busters serve a distinct role in U.S. strategy by enabling strikes on fortified positions without the use of nuclear weapons. Their effectiveness depends on a combination of delivery platform survivability, munition design, intelligence on target layout, and terminal guidance precision.
Globally, the trend toward constructing more elaborate and deeply buried infrastructure is increasing the demand for advanced penetrator capabilities. China’s 1,500-acre underground military complex near Beijing, believed to house strategic command infrastructure, and the construction of over 320 hardened missile silos between 2021 and 2025 illustrate this shift. According to analysis published in the Bulletin of the Atomic Scientists, these silos are designed to accommodate DF-41 intercontinental ballistic missiles and are supported by hardened command-and-control networks. In a November 2024 RAND report, analysts concluded that the U.S. may need to conduct long-range conventional strikes on Chinese buried inland facilities if surface and maritime assets cannot be neutralized early in a conflict. Furthermore, analysis by the Atlantic Council highlighted the importance of standoff-capable munitions in overcoming modern integrated air defense systems. These operational considerations underscore the relevance of the NGP, not only as a technical upgrade, but as a critical capability within U.S. strategic planning for future high-intensity conflicts.
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As reported by The War Zone on June 24, 2025, the U.S. Air Force has accelerated efforts to develop a new air-delivered munition known as the Next Generation Penetrator (NGP), which is intended to succeed the GBU-57/B Massive Ordnance Penetrator (MOP). This decision follows the first operational employment of the GBU-57/B during Operation Midnight Hammer, in which B-2 Spirit stealth bombers dropped a total of 14 MOPs on Iranian nuclear facilities. Twelve munitions were dropped on the Fordow enrichment complex, while two were aimed at Natanz.
Follow Army Recognition on Google News at this link
The B-21 Raider stealth bomber, still in development, is projected to be the primary delivery platform for the NGP, although it is only expected to carry one MOP-sized munition per sortie, compared to the B-2’s capacity of two. (Picture source: US DoD)
According to the Air Force’s February 2024 contracting notice, the Next Generation Penetrator is being designed with a maximum warhead weight of 22,000 pounds and must be capable of delivering blast, fragmentation, and deep penetration effects. While the gross weight and external dimensions of the complete munition remain unspecified, the NGP will likely be smaller than the 30,000-pound GBU-57 to better align with the internal payload bay limitations of the B-21 Raider stealth bomber. Unlike the GBU-57/B Massive Ordnance Penetrator (MOP), which is an unpowered gravity bomb, the Next Generation Penetrator (NGP) may feature powered standoff capability to enable delivery from a safer distance, especially in highly contested airspaces. Integration with the B-21 is a key consideration, since the new platform is expected to replace the B-2 and carry a significantly greater share of the long-range strike mission. Currently, the B-2 is the only operational aircraft cleared to deliver the MOP, and it can carry just two per sortie, a constraint that would double the number of required aircraft if translated to the B-21.
The contracting notice also specifies stringent performance requirements for the NGP’s guidance and navigation systems. These include a terminal accuracy of CE90 within 2.2 meters, meaning the weapon must impact within 2.2 meters of the intended target at least 90% of the time, even in GPS-degraded or denied environments. This level of accuracy far exceeds that of conventional GPS-assisted Joint Direct Attack Munition (JDAM) bombs, whose error margins can increase to over 30 meters when GPS signals are unavailable. The Air Force is encouraging the integration of advanced Guidance, Navigation, and Control (GNC) systems, including technologies capable of operating autonomously and maintaining precision under electromagnetic disruption. In addition, the NGP is expected to include embedded fuze technology, with particular interest in void-sensing and floor-counting fuzes. These would allow the munition to detect when it has penetrated into internal spaces of an underground facility and detonate at the optimal point for maximum structural damage. This capability is especially vital when detailed pre-strike intelligence on facility layout and depth is limited or incomplete.
The NGP effort builds on more than a decade of analysis and past development experience. The program requirements draw on findings from the 2012 Hard Target Munitions (HTM) Analysis of Alternatives (AoA) and a 2019 excursion update. Unlike the GBU-57, which was initially developed as a rapid reaction capability outside a formal program of record, the NGP is being approached as a long-term, scalable program. It may eventually constitute a family of systems rather than a single munition, with variants tailored for different target sets and delivery platforms. The NGP is also tied to the broader Long Range Strike (LRS) system-of-systems concept, which includes the B-21 bomber and the AGM-181A Long-Range Stand-Off (LRSO) nuclear cruise missile. According to contracting documents, the Air Force plans to take delivery of around 10 subscale test articles and three to five full-scale prototypes within 18 to 24 months of contract award. The contracting process is being managed under the Eglin Wide Agile Acquisition Contract (EWAAC), and integration requirements include compatibility with the BRU-72/B release interface and 1760 connector standards. System design maturity is expected to reach a Technology Readiness Level (TRL) of 5 to 6 by the end of the prototype phase, with a goal of achieving validated performance through sled and static testing.
The GBU-57/B Massive Ordnance Penetrator, now undergoing a phaseout trajectory, remains the largest conventional bunker-buster munition in the U.S. arsenal. Weighing 30,000 pounds and measuring 20.5 feet in length, the MOP includes a BLU-127/B penetrating warhead weighing around 5,000 pounds, approximately 20% of the total munition weight. It is guided by a GPS-assisted inertial navigation system and uses specialized fuzing to survive high-speed impacts through hardened material before detonating inside a target. Its exact penetration capability is classified, but estimates suggest it can reach at least 60 meters into reinforced concrete, with some sources suggesting even greater depth. Despite its size and capabilities, the MOP has drawbacks, including its unpowered trajectory that requires bombers to fly relatively close to their targets, and its limited production rate. Recent reports suggest efforts are underway to triple or even quadruple the annual production capacity of MOPs, though the current stockpile remains small.
Operation Midnight Hammer marked the first time that MOPs were used in actual combat, after more than a decade of deterrence-oriented deployment. B-2 bombers delivered the 14 GBU-57s during night strikes between June 21 and 22, 2025, after this bomb was selected for this operation due to its precision-guided capabilities and capacity to engage deeply buried infrastructure. Satellite imagery confirmed precise impacts at both Fordow and Natanz, with visible craters indicating successful delivery, but some experts raised doubts about the overall effect. Reports from U.S. intelligence sources and foreign analysts suggest that the core of Iran’s nuclear infrastructure may have survived, particularly at Fordow, which lies about 30 meters deeper than MOP’s published penetration threshold. This perceived limitation has prompted debate about the effectiveness of even the most powerful conventional bunker-busters against well-engineered underground targets. In response, the Department of Defense emphasized that battle damage assessments were still ongoing and that early conclusions lacked full corroboration from the intelligence community. Nevertheless, lessons from this operation are reportedly being integrated into the NGP’s development process, especially as the Pentagon plans for potential future conflicts involving other deeply hardened targets, such as those found in China, North Korea, or Russia.
Bunker-buster bombs have been part of the U.S. inventory since the 1991 Gulf War, when the GBU-28 was fielded using modified artillery barrels to penetrate hardened Iraqi shelters. Since then, systems such as the GBU-37 and GBU-72/B have expanded this category, offering different levels of weight and penetration capabilities. The GBU-72/B, a 5,000-pound class precision-guided bomb, was used operationally in recent strikes against Houthi forces in Yemen. These weapons employ delayed fuzing to maximize internal structural damage after penetrating surface defenses. Bunker-busters serve a distinct role in U.S. strategy by enabling strikes on fortified positions without the use of nuclear weapons. Their effectiveness depends on a combination of delivery platform survivability, munition design, intelligence on target layout, and terminal guidance precision.
Globally, the trend toward constructing more elaborate and deeply buried infrastructure is increasing the demand for advanced penetrator capabilities. China’s 1,500-acre underground military complex near Beijing, believed to house strategic command infrastructure, and the construction of over 320 hardened missile silos between 2021 and 2025 illustrate this shift. According to analysis published in the Bulletin of the Atomic Scientists, these silos are designed to accommodate DF-41 intercontinental ballistic missiles and are supported by hardened command-and-control networks. In a November 2024 RAND report, analysts concluded that the U.S. may need to conduct long-range conventional strikes on Chinese buried inland facilities if surface and maritime assets cannot be neutralized early in a conflict. Furthermore, analysis by the Atlantic Council highlighted the importance of standoff-capable munitions in overcoming modern integrated air defense systems. These operational considerations underscore the relevance of the NGP, not only as a technical upgrade, but as a critical capability within U.S. strategic planning for future high-intensity conflicts.
