Los Alamos Scientist's Insights On The GBU-57 Massive Ordnance Penetrator

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Sometime around 2012, Gary Stradling looked into a deep hole at the White Sands Missile Range in New Mexico and pondered the future of the 30,000-pound GBU-57/B Massive Ordnance Penetrator (MOP) bunker buster bombs, America's largest conventional weapon. The hole was made during testing of the MOP and Stradling, at the time, was division chief of the Nuclear Detection Division of the J9 directorate at the Defense Threat Reduction Agency (DTRA). While he was not involved in MOP testing, Stradling was 'intensely interested in the science of earth penetrating munitions having had professional engagement in related subjects at different times in my highly-varied career.'
Me, standing at the edge of a MOP crater on a mountain top at White Sands Test Range, where detailed studies of massive earth penetrators were studied for effectiveness against deeply buried targets by the Defense Threat Reduction Agency (DTRA) —formerly Defense Nuclear Agency.… pic.twitter.com/JYq1V2xO6q
— Gary Stradling (@gary_stradling) June 24, 2025
In addition to leading the Hypervelocity Impact team at Los Alamos National Laboratory (LANL), he served as a science advisor, detailed from LANL to the Nuclear Forces Policy Office of the Secretary of Defense. He later served with the Office of Military Applications at LANL and is now retired. We spoke to Stradling about his observations of the testing that led up to the MOP and its recent use against Iranian nuclear facilities during Operation Midnight Hammer, which resulted in 14 being dropped by B-2 Spirit stealth bombers on two very hardened locations that were key to Iran's capacity to produce nuclear weapons. The questions and answers were lightly edited for clarity. You can read more about the fascinating 15-year development of the MOP in our deep dive here.
Q: Talk about how researchers dug into the mountain and blew it up. Can you provide more details about that?
A: Well, the mountain in White Sands, they specifically picked mountainous areas that were solid rock, and they used state-of-the-art tunneling technology to make the kind of cavities in the mountain that you would put this kind of [Iranian nuclear] facility in. I think that there is a lot of work that DOD has done in these kinds of facilities that is highly classified, and I couldn't talk to you about it. This is very sophisticated work. It is not casual, and it's not speculative. These are real experts who are doing the work. Careful, technical, quantitative work to be able to deliver this kind of war-fighting capability to the services.
Q: Describe the scene as you were looking into the MOP hole.
A: The picture that you have of me is standing at the entrance hole where the MOP went into the mountain that had a crosshair on it, and the hole was really close to the crosshair, and it was a big hole, and I'm standing right at the edge of the barrier to keep people from falling into this big hole. And the hole went down into a chamber that had been mined into the hard rock below that was intended to simulate, or to be very much like these hardened facilities.
Q: When you were looking at this hole, what were you thinking in terms of what the weapon could be used for? And did you ever imagine that it could be used as accurately as it was in Operation Midnight Hammer?
A: Well, during my time at Los Alamos in the nuclear weapons directorate, when I came back to Los Alamos in 2000, I was in what was called the Military Applications Office and worked closely with STRATCOM and developmental ideas for how nuclear weapons could be used for some of these applications. So I had the opportunity to look at what it really takes for a weapon to penetrate into the ground. And one of the things that became clear to me was that this is not just something that if you hit it harder, you go deeper, or if you make it bigger, you go deeper. There are real limitations to how deep you can get into rock when you plunge something into it.
It's very interesting to have gone from that background, that computational background, to standing over such a hole that had been blown into a mountain. One of the things that has been discussed is, can you do what they call multiple miracles – sequential miracles? If you can drop a weapon – if you've got three B-2s up there – and they each drop a weapon that can vector itself to a very highly accurate position in a mountain, and you can penetrate with one and blow a hole, and then all of that material is suspended. And you have another one come in immediately afterwards and penetrate through much softer material, until you get into hard material, and you penetrate that, and then you explode, and you levitate all that material. Then you bring a third one in after it, you could start thinking about digging really deeply in. Now, I've got no idea whether this operation, Midnight Hammer, I think, is the term that was used, whether that was such a sequential process with that kind of accuracy [it was, each hole got six MOPs]. But, gee, that's awesome, to be able to have subsequent devices, avoid the blast of the previous ones, and yet penetrate in and, like a sledgehammer, drive through again and again into a harder material.
Q: So you have to make sure that the subsequent MOPs don't get affected by the overpressure and explosive force of the previous ones, right?
A: Right. So you'd have to have those in a sequence that took all of that into account. You're surely going to have suspended material. But if you can avoid the shock from the initial explosion for the second and third penetrators – you know that that is really highly, highly tuned delivery, and we have gotten very good now. I'm not saying that I know anything about that. I'm just saying that that was part of the discussion during the time that I was working on it, could we actually do these sequential miracles and get these things on target? And when we watch Elon Musk land rocket ships, we go, maybe we're in that kind of a world.
Q: When you were there, what was the sense of whether these so-called multiple miracles would ever come to pass?
A: Oh, I think everybody was optimistic and skeptical simultaneously. We know how hard these jobs are.
Q: You talked about doing computational work. What were you considering as you were doing computational work on how these things could achieve the maximum effectiveness?
A: Early in my career, I was diverted to a project called the Hypervelocity Impact Project … It was a project at Los Alamos that mirrored other things that had been going on in other places. There was a place in Germany where you take small particles and you accelerate – you put a charge on small iron particles and you accelerate them through a very large electric field using a Van de Graaff accelerator. And so we had particles that were growing between five and 50 kilometers per second that were not just atoms, but they were chunks of iron, very small chunks, but they were macroscopic. And then we measured the impact craters into different kinds of materials, and we calculated what those impacts would look like. So we gained a pretty good idea of how effective such a technique would be.
One interesting fact about the MOP: The US appears to have tested it against a real underground facility just 30 kilometers south of the site of the world's first nuclear weapons test. Thread from a recent OSINT side quest. 1/10 pic.twitter.com/M9yLZ5lRiX
— Fabian Hinz (@fab_hinz) June 25, 2025
So later, when I came back from the Pentagon and was in the Military Applications Office, people were talking about using penetrators with nuclear weapons, a theoretical discussion. I don't know if there ever was a nuclear penetrator program. And so I got a chance to study the physics of the penetrators. The question of how much acceleration or deceleration could nuclear weapons tolerate? Because, as one of these MOP devices goes into a solid rock mountain is going to decelerate rapidly, and if you've got fragile stuff inside the casing, you could break it. So those are the the kind of questions that you had to deal with. And of course, you can design just about anything because we have very clever people, but that's one of the questions.
So how deep can you go with a penetrator? If you just have a solid piece of tungsten, and you deliver it at infinite velocity, would it go all the way through the Earth? And the answer is no, it would go a certain depth, and then would stop. Even if it was solid tungsten, three feet in diameter and 30 feet long, there is going to come a point where it's going to lose all of its momentum, and that energy will be dissipated into sort of a half sphere. So understanding that there are limitations to penetrators, and there are limitations to what kind of forces, shock forces that the explosive package can tolerate, is part of the question. So that was very interesting for me, then to be standing on this mountain, looking down in this hole, and then touring the … facility that had had the experience of having a MOP device dropped on it.
Q: What year was that?
A: Probably 2012 or 2013.
Q: Is there a concern that radioactive materials like enriched uranium could be disturbed by the force of the MOPs?
A: If you're blasting into a facility that has nuclear materials, it's always possible for some of that material to vent out as that shock wave goes through the material and finds ways to you know, you don't know whether it is completely enclosed or whether you've got ventilation ducts or whatever. But I frankly don't think that's a big issue. It's enormously overplayed by the green community that the amount of material that you'd have and its effect on anything is. My sense is that it's very small.
Q: You mentioned that you have experience in developing the signatures to look for radioactive materials and enrichment. Can you talk about that?
A: There is a large national and international technology effort to understand, detect and analyze signatures of nuclear proliferation. This has been an ongoing DOD/DOE effort for decades; the IAEA in Vienna does some of this. The U.S. has a large nuclear monitoring system that at one point was under my purview. I funded that and the staff who were the DOD overseers of that. There are contractors who do this work. Some of the national laboratories do a lot of work on that.
So, there are seismic sensors and where they're positioned and how they're monitored and analyzed can tell you whether you see a lot of seismic activity on the Earth. And you have to understand the geology of the Earth. And then when you see signals, you will see if there's a nuclear explosion or an earthquake. You will see it across what is becoming a vast array of seismic sensors today, and you could do a lot of analysis on the nature of the explosion and its location. So that's one very interesting thing. Can you tell if Iran conducts a nuclear test? If North Korea conducts a nuclear test? Pakistan, India, etc. If they conduct a nuclear test, there is a lot that this community is going to know about it.
And so also, if somebody conducts a nuclear test, you have more than seismic activity. You can watch the mining activity using overhead imagery. You can smell – you can sniff the air and see whether there are radioactive materials that have particular characteristics that would result from a nuclear test. And if there's a fair amount, you can know about the nuclear test by knowing what the salad of isotopes is that comes off of the test. And so you've got their half lives, and you can detect what their isotopes are, and so on. So there is a great deal of work that goes on.
The office that I had at DTRA was a relatively small office compared to the work being done at the Department of Energy and at the Air Force, and also other international partners that work in this area.
Q: And as chief of the DTRA office developing technologies for detecting nuclear proliferation, particularly clandestine nuclear testing, that's where your experience comes in with how to find this stuff, correct?
A: Right. The Proliferation Technology Office really had responsibility for figuring out how to enhance, how to make better our capability to know exactly what potential proliferators were doing and what activities they were conducting. There's a huge effort across the intelligence community to know who the scientists are and what kind of technologies are going there, and whether we could embargo technologies to slow down the spread – a huge effort going on from early days to try to limit the spread of nuclear weapon technology, the kinds of things that are at the cutting edge now. Can you sense? Can you smell the air? How close can you get to the event? Where can you take a sample? Can you measure something seismically? Can you see a flash if there's a nuclear explosion? Can you see a flash from space? And would that flash tell you? Would it tell you with confidence that it was a nuclear flash, or might it be something else? Might it be a meteorite? So those are the kinds of things that the Proliferation Technologies Office cared about.
And we weren't alone. DOE has groups working on that, and has an organization that works on that, and also people at Los Alamos here up on the Hill are actively working in some of those areas. And I actually contracted as a DTRA manager. I contract with Los Alamos to help me in some of those areas.
Q: As far as we know, Iran is still not at the threshold of creating a nuclear weapon. What are the kinds of things that would have been done to get a sense of what's happening in Fordow and Natanz and Isfahan, and what might be happening now in the wake of these attacks?
A: The time it takes to refine uranium is much less once you have a few percent concentration. The time it takes to go from natural uranium to a few percent is long. The time it takes to go from 8% to weapons-grade is short. And I think that legislators and the general public just don't appreciate that the process of refinement can go very fast in the late stages. It's not linear in any sense.
Q: If you were a betting man, what would you say the odds are of the Iranians having a nuclear device sometime this year?
A: Howard, I can see your headline right now. Dr. Stradling, former DTRA blah, blah, blah says the Iranians … I actually would not make such a guess, such a headline. I would just say I think that to presume that they don't have one is overly optimistic. To presume that they don't have sufficient nuclear material, to presume that they don't have a tested device, we may not have intelligence that tells us they do, but to presume that they don't is, I think, overly optimistic, and I really love President Trump. He's my kind of guy. I mean, he has amazing huevos and a determination to do good in a way that I see good, and yet he wants to have positive reports. And I understand him saying, 'Somebody told me that this was the best, you know, the best penetrating attack ever in the history of mankind,' and that's the way he talks. But I don't want him to be embarrassed by finding out later that the uncertainty of the battlefield still applies, even to this latest attack on the Iranian nuclear facilities – that things don't go as well as we expected, and that's the nature of warfare.
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