To neutralize Iran’s nuclear program, the US used its ‘stealth’ B-2 bombers, which flew inside Iran on June 21 and dropped the GBU-57 Massive Ordnance Penetrator (MOP) on two nuclear sites – Fordo and Natanz.
A total of 14 MOPs were launched by seven B-2 Spirit stealth bombers on the designated targets. This marked the first combat use of these deadly 30,000-pound bombs that can penetrate 200 feet (60 meters) before detonating.
Nearly three months later, a successor to this unique munition—called the Next-Generation Penetrator (NGP) is already here.
The US Air Force Life Cycle Management Center’s (AFLCMC) Munitions Directorate at Eglin Air Force Base in Florida awarded a two-year contract to Applied Research Associates (ARA) for designing and prototyping the successor of the enormous MOP bunker-busting bomb last week. The contract was confirmed by the company, which stated that it will work on the air-to-ground Next Generation Penetrator.
ARA will “serve as the System Design Agent for the development of a prototype air-to-ground Next Generation Penetrator weapon system,” said a company press release published by the defense firm. “ARA will also produce and test sub-scale and full-scale prototype munitions. This effort will evaluate capabilities against hard and deeply buried targets that pose critical challenges to US national security.”
Notably, ARA will develop the next bunker buster bomb in close collaboration with Boeing, which is the prime contractor for the GBU-57 MOP. Boeing will assist with the overall integration, design, and construction of the new bomb’s tail kit.
The only aircraft authorized to use MOPs operationally at this time is the stealthy B-2 bomber, which is limited to carrying two of them on a single flight.
The B-2, as well as the next-generation B-21 Raider, could be the potential carriers of the NGP. However, the B-21 would be able to carry just one of the new bombs since the Raider is smaller.
The development of the NGP follows the rise to prominence of the GBU-57 after its combat debut in Iran.
The satellite imagery published in the aftermath of the attack showed six large craters and grey ash covering the mountainside of the facility, indicating multiple penetration points. Experts said the bombs had caused “very significant damage” to the underground halls, with vibration-sensitive centrifuges likely obliterated.
Now, with the development of the NGP, the USAF has taken a step towards expanding the bunker-busting capability significantly.
To make sense of what the NGP would look like, it is crucial to understand the GBU-57 MOP.
The MOP is a precision-guided “bunker buster” bomb developed as part of the “Big BLU” program that was initiated in 2002. Its development intensified after the invasion of Iraq in 2003, which revealed flaws in the existing weapons against targets that were deeply buried underground. The GBU-57 MOP went into service in 2011.
The GBU-57 MOP’s warhead belongs to the BLU-127 family. Interestingly, depending on the type, the warhead includes between 2,082 and 2,600 kilograms (4,590 and 5,732 pounds) of high explosive out of its 13,600 kilograms (30,000 pounds) of mass. The warhead constitutes only roughly 20 percent of the total weight of the bomb.
The GBU-57 MOP features a dual-mode guidance system that targets with high accuracy using a GPS (Global Positioning System) and an Inertial Navigation System (INS). The subsequent, more advanced variants of GBU-57 MOP use an adaptive fuze system that can detect structural voids during penetration. It also times its detonation for maximum internal destruction—making it deadlier.
The GBU-57 is a special weapon. It is the only bomb of its sort in the world, capable of penetrating 200 feet before detonating. In fact, according to a recurring discourse surrounding the weapon, the MOP was designed especially to destroy Iran’s deeply-buried nuclear facilities, as explained by the EurAsian Times earlier.
While the MOP dealt a significant blow to the Iranian facilities, it has not destroyed the West Asian country’s nuclear program, and the need for a heavy bunker buster is only amplified amid rising security threats. The US still needs to be prepared to face evolving threats from adversaries like Iran, North Korea, China, and Russia, who are increasingly relying on underground infrastructure to protect critical assets.
This is where the NGP comes into the picture.
NGP & What Do We Know About It?
The Next-Generation Penetrator (NGP) program emphasizes a lighter, more versatile design compared to its predecessor, potentially allowing integration with a broader range of aircraft platforms, including the smaller B-21 Raider.
The NGP is envisioned as a successor to the existing GBU-57 MOP, focusing on enhanced capabilities to strike hard and deeply buried targets, such as underground laboratories, tunnels, military facilities, or protective shelters for high-value enemy personnel.
These targets could pose significant challenges to security, including fortified nuclear sites or command centers buried deep beneath mountains or reinforced structures.
Interestingly, the US started working on the next-generation bunker buster bombs almost as soon as the GBU-57 MOP began entering service in the early 2010s.
The development of this new bunker buster will be informed by lessons learned from recent military applications. Since the program is still in its infancy, certain technological aspects are classified or restricted. However, the information available emphasizes accuracy, penetration, and adaptability in contested areas, where the enemy employs very-long-range anti-air or air defense missiles.
The NGP program stems from a 2012 Hard Target Munitions Analysis of Alternatives and a 2019 follow-up study, which identified the need for improved penetrators.
The USAF issued requirements for the NGP in a contracting notice in February 2024, saying: “The United States Air Force (USAF) is seeking to identify capable vendors for the development of a prototype penetrator warhead design capable of defeating Hard and Deeply Buried Targets (HDBT).”
“Additionally, the USAF is seeking to identify vendors specialized in the design, development, and production of precision guidance systems for potential integration into this class of penetrator weapon,” it added.
The program gained momentum after the GBU-57 MOP was dropped on Iran in June 2025. Though the value of the contract has not been disclosed, the Air Force’s 2026 budget request included about $107 million for NGP development in August 2025, with $120.8 million allocated in fiscal 2025 and $73.7 million in 2026. The design, development, and testing of the new weapon are expected to continue through 2027.
In its February 2024 notice, the USAF said that the NGP designs must provide blast, fragmentation, and penetration capabilities, building on prior penetrator technologies.
Further, it called for a terminal accuracy of Circular Error Probable 90% (CE90) within 2.2 meters, even in GPS-degraded or denied environments. This implies that the munition must strike within 7.2 feet (2.2 meters) of a designated impact site at least 90% of the time, which is believed to be a very stringent requirement.
The USAF has also communicated that the weapon should have Advanced Guidance, Navigation & Control (GNC) technologies for high precision in contested areas. The developers of the NGP are likely to focus on potential integration of embedded fuze systems, including void-sensing fuzes to optimize detonation by detecting breaches into large voids or counting penetrated layers.
The fuze technology is critical for bunker-buster bombs, as they must penetrate a hard surface before exploding. The notice also noted that the NGP design should integrate lessons learned from previous penetrator warhead programs.
“The prototype penetrator warhead design effort should allow integration of technologies acquired and lessons learned under previous penetrator warhead developments to meet performance requirements for the HDBT target set.”
The NGP will also likely integrate rocket boosters for standoff strike capabilities. For perspective, the GBU-57 MOP is not powered, which is why it needs to be dropped at close ranges.
Although the 2024 contracting notice does not say so, the USAF has separately said that it is interested in the addition of a powered standoff capability to the NGP.
In fact, the early planning documents from 2010 and the 2024 RFI suggest the NGP could include a rocket booster or similar propulsion to allow release from greater distances, reducing risk to aircraft from air defenses.
Additionally, the NGP would be required to have improved performance against harder and deeper targets than the MOP.
It is safe to assume that the NGP’s development reflects the US military’s emphasis on maintaining superiority against proliferating underground threats. When it replaces the GBU-57 MOP, the NGP will become the most powerful bunker buster in the world—and help the USAF take a step ahead of its adversaries.
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