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Three B-2 Spirit stealth bombers prepare for departure during Exercise Bamboo Eagle at Nellis Air Force Base, Nev., on Feb. 10, 2025. U.S. Air Force photo by Senior Airman Bryson Sherard.
The B-2 Spirit bomber first flew on July 17, 1989, yet each of the seven extensively modernized B-2 bombers participating in the successful strike on Iran’s nuclear weapons did something the B-21 Raider will never be able to do—each dropped two 30,000-pound GBU-57 bunker-buster bombs. That’s right, the B-21, which is projected to take over B-2 duties in the early 2030s, can carry only one GBU-57. That it can carry only one is actually a pretty big deal and is a reason to consider having the incredibly capable B-2 join the heavily modernized 1950s-era B-52s in protecting U.S. interests for decades to come.
By being able to carry two GBU-57 bombs, the seven B-2 bombers that struck Fordow and Natanz required far less logistical support than what would have been required for 14 B-21s. Further, while the GBU-57 strike brilliantly took advantage of a weakness in the Fordow facility—its air vents—it also revealed that, as big and powerful as the GBU-57s are, they did need to take advantage of a weakness in Fordow’s formidable defense to be successful. In other words, without the air vent weakness, Fordow—protected by at least 250 feet of rock that, on average, is much tougher than concrete—would likely have been safe from being destroyed or significantly damaged by only 12 GBU-57 bunker busters.
This suggests a need for even more powerful bunker busters, which, given the physics of deep penetrators, means developing larger and heavier bunker busters that capitalize on the fact that a bunker buster’s ability to penetrate increases faster on a percentage basis than its weight. Illustrating this principle, a 2,000-pound GBU-31v(3)b with its Blue-109 warhead can penetrate about two meters of reinforced concrete, while the 30,000-pound GBU-57, which weighs 15 times more than the GBU-31v(3)b, can penetrate 30 times deeper. Hence, a weight increase of 1,400 percent yielded a 2,900 percent increase in penetration.
Bottom line, the B-2’s payload of 60,000 pounds versus the B-21’s much smaller 30,000 pounds is a huge advantage that will allow it to deliver bunker busters in the future even more powerful than the GBU-57. More generally, a bigger payload means that a single B-2 can deliver what it would take two B-21s to deliver, and there are some missions that it will be able to execute that a B-21 cannot.
But the B-21, being smaller and newer, costs less to fly and maintain. And while the B-21’s smaller size likely renders it more vulnerable to scattering and resonance effects that make stealth craft vulnerable to longer wave radars such as VHF, it is said to be stealthier than the B-2. And although no real specifics have been released yet, the Air Force claims that it will have a longer range than the B-2, despite being smaller. If all these claims are borne out, these factors will certainly be a significant advantage.
But let’s not forget that the truly revolutionary B-2 set a very high standard for stealth when it was first built and that, along with regular overhauls to ensure structural strength, it has received billions of dollars of upgrades to its stealth, avionics, and radar. All these upgrades ensure that it remains the stealthiest operational combat plane in the sky. Indeed, it is far stealthier than an F-35 and is even stealthier than an F-22. And with future upgrades, it can continue to fly for decades to come. And when it comes to range, it could end up being the case that a B-2 carrying only 50 percent of its max payload, 30,000 pounds, has a greater range than the B-21 carrying its max payload, the same 30,000 pounds.
Consequently, the B-2 is likely to remain the stealthiest operational combat plane flying until the B-21 becomes operational. But even when the B-21 becomes operational, the question becomes just how many missions the B-21 will be able to execute that the B-2 cannot. Sure, it will be stealthier than the heavily modernized B-2 with its upgraded advanced radar-absorbing material. But given the ongoing rapid advancements in counter-stealth technology, any idea that the B-21 is going to deliver a revolutionary new level of stealth that will allow it to fly blithely into the air defenses of peer competitors to drop bombs on targets is unrealistic. Instead, what is much more likely is that there will be a bunch of air spaces that are too risky for either the B-2 or B-21, a bunch of air spaces in which both can successfully conduct combat operations, and a relatively small subset of air spaces that the B-21 can penetrate that would be too risky for the B-2.
What this all adds up to is that the best possible combo for maximizing U.S. air power would be maintaining and modernizing as many as possible of the 19 B-2 bombers currently in service to serve alongside the B-21 for the foreseeable future. This would allow us to continue to benefit from the B-2’s much, much larger payload while leveraging the claimed lower operational costs of the B-21 and its ability to conduct strikes into that subset of air spaces too risky for the B-2.
That adopting this course might mean reducing the number of B-21s we buy won’t make the manufacturer happy, but defense procurement should be about delivering the most bang for taxpayer dollars, not happy contractors.
Views expressed in this article are opinions of the author and do not necessarily reflect the views of The Epoch Times.
Mike Fredenburg writes on military technology and defense matters with an emphasis on defense reform. He holds a bachelor’s degree in mechanical engineering and master’s degree in production operations management.
