U.S. long-range B-2 stealth bombers launched airstrikes targeting underground bunkers used by Yemen’s Houthi rebels.

The U.S. military unleashed B-2 stealth bombers to target underground bunkers used by Yemen’s Houthi rebels early Thursday, a major escalation in the American response to the rebels’ attacks on Mideast shipping lanes that appeared to be a warning to Iran as well.

While it wasn’t immediately clear how much damage the strikes caused, the attack appeared to be the first use of the B-2 in combat in years and the first time the flying wing targeted sites in Yemen.

In announcing the strikes against the Houthis, who have been attacking ships for months in the Red Sea corridor over the Israel-Hamas warin the Gaza Strip, U.S. Defense Secretary Lloyd Austin made a point to offer a warning likely heard in Tehran as well.

    • talEnglish
      51·
      1 month ago

      Oh, that’s an interesting thought. That topic was in the news recently relating to the prospect of Israel doing a strike on Iran’s underground nuclear facilities, discussion of whether Israeli warplanes could carry a bomb capable of penetrating Iranian nuclear bunkers. The answer was that they couldn’t carry a huge bomb, but I commented that with the precision of modern guided bombs, they might be able to just strike the same place multiple times, and I saw a subsequent article also raising that possibility, so it’s not just me.

      I remember reading an interesting comment on Reddit some years back on how Iran was actually a world leader in UHPC, though, and I have no idea whether they’ve provided that to the Houthis; it might be specific to Iran.

      https://en.wikipedia.org/wiki/Types_of_concrete#Ultra-high-performance_concrete

      Ultra-high-performance concrete

      Ultra-high-performance concrete is a new type of concrete that is being developed by agencies concerned with infrastructure protection. UHPC is characterized by being a steel fibre-reinforced cement composite material with compressive strengths in excess of 150 MPa, up to and possibly exceeding 250 MPa.[5][6][7] UHPC is also characterized by its constituent material make-up: typically fine-grained sand, fumed silica, small steel fibers, and special blends of high-strength Portland cement. Note that there is no large aggregate. The current types in production (Ductal, Taktl, etc.) differ from normal concrete in compression by their strain hardening, followed by sudden brittle failure. Ongoing research into UHPC failure via tensile and shear failure is being conducted by multiple government agencies and universities around the world.

      goes looking for something more-authoritative than a Reddit comment

      Yeah, looks like it.

      https://www.machinedesign.com/markets/defense/article/21833836/super-concrete-shielding-iranian-nukes

      Super concrete shielding Iranian nukes?

      June 14, 2012

      Some of the world’s experts in ultrahigh-performance concrete (UHPC) are working in Iran, a country regularly beset by earthquakes. They want to use the material, a mix of Portland cement, silica fume, quartz flour, fine silica sand, and either steel or plastic-reinforcing fibers, to build durable bridges, sewer pipes, dams, and other structures.

      But U.S. military officials and others around the world are worried the Iranians will use the high-strength material to protect nuclear-weapons labs and to build other military bases and underground bunkers.

      UHPC’s compression strength is on the order of 30,000 psi, while that of normal concrete is just 4,000 psi. And UHPC has a tensile strength of 1,000 psi, far above normal concrete’s 400 psi. Strength is critical for defensive structures. Tests of a 13-ton bunker-busting bomb, for example, showed it could penetrate 180 ft of ordinary concrete, but only get through 25 ft of concrete that was twice as strong. So it’s possible that the same bomb might only dent UHPC, with its compressive strength seven times that of normal concrete.

      EDIT: The author deleted his comment (unfortunately; I think that it was insightful), but the gist of it was that it raised the point that it might be possible that the B-2 was necessary to carry a large, bunker-busting bomb.

      EDIT2: He was also correct when he said that the B-2 was one of the only aircraft capable of carrying some large, penetrating weapon; the MOP appears to fit that bill.

      • Billy@lemmy.dbzer0.comEnglish
        32·
        1 month ago

        Interesting stuff.
        I deleted it since I started doubting what I wrote and didn’t really have the time to look into it.

        • talEnglish
          3·
          1 month ago

          The New York Times stated that this was specifically asked the Pentagon, given the phrasing of their announcement and got a no-comment. It’s certainly a good thought.

          https://www.nytimes.com/2024/10/17/us/politics/houthis-strike-stealth-bombers.html

          “This was a unique demonstration of the United States’ ability to target facilities that our adversaries seek to keep out of reach, no matter how deeply buried underground, hardened or fortified,” Mr. Austin said in a statement late Wednesday night. “The employment of U.S. Air Force B-2 Spirit long-range stealth bombers demonstrate U.S. global strike capabilities to take action against these targets when necessary, anytime, anywhere.”

          Attacking so-called hardened buried sites generally requires the use of specially built bombs that have much thicker steel cases and contain a smaller amount of explosives than similarly sized general-purpose bombs. The heavy casings of such “bunker buster” bombs allows the munition to stay intact as it punches through soil, rock or concrete before detonating.

          The B-2 is the only warplane that can carry the largest of this class of weapon in the Pentagon’s inventory: a 30,000-pound GPS-guided munition called the GBU-57 Massive Ordnance Penetrator, or MOP, that contains the equivalent of about 5,600 pounds of TNT. A Pentagon spokesman declined to say whether that weapon was used in the attack on Wednesday.

          EDIT: Reading the above, maybe the situation is basically both of the two guesses here combined.

          It’s a message to Iran, and the reason that the B-2 specifically is involved in that message is because it can drop very large bunker-busters, which could presumably penetrate Iranian facilities.