Bunker buster

Röchling shells were bunker-busting artillery shells, developed by the German engineer August Coenders, based on the theory of increasing sectional density to improve penetration. They were tested in 1942 and 1943 against the Belgian Fort d'Aubin-Neufchâteau.{{cite web|url=http://derelicta.pagesperso-orange.fr/aubin3.htm|title=Les étranges obus du fort de Neufchâteau (suite)|website=derelicta.pagesperso-orange.fr|language=fr|access-date=11 June 2016}}{{Cite news |date=28 September 2024 |title=’Banned’ Bunker-Buster Bombs used by Israel to kill Hezbollah chief Hassan Nasrallah: 7 things to know |url=https://www.livemint.com/news/world/israels-85-bunker-buster-bombs-used-to-kill-hezbollah-hassan-nasrallah-understanding-the-geneva-banned-weapon-11727527180860.html |access-date=2 March 2025 |work=Mint}}

In World War II the Luftwaffe developed a series of unguided rocket-propelled armor-piercing bombs for use against shipping and fortifications.

File:U-Boat Pen Grand Slammed.jpg after being hit by a Grand Slam. Note the figure standing on the pile of rubble.]]

File:Disney bomb impact test.png striking the German, Valentin U-boat pen. The bomb was one of a number dropped on the bunker during post-war testing{{harvnb|Project Ruby|1946|p=214}}]]

In World War II, the British designer Barnes Wallis, already famous for inventing the bouncing bomb, designed two bombs that would become the conceptual predecessors of modern bunker busters: the five tonne Tallboy and the ten tonne Grand Slam. These were "Earthquake" bombs—a concept he had first proposed in 1939.{{Cite web|title=Earthquake Bombs |publisher= Barnes Wallis Foundation|url=https://www.barneswallisfoundation.co.uk/portfolio/earthquake-bombs/|access-date=2020-11-27|language=en-GB}} The designs were very aerodynamic, allowing them to exceed the speed of sound as they fell from 22,000 ft (6,700 m). The tails were designed with offset fins causing the bombs to spin as they fell. Using the same principle as a spinning top, this enabled them to resist being deflected, thereby improving accuracy. They had casings of high grade steel, much stronger than the typical World War II bomb so that they would survive hitting a hardened surface, or penetrate deep into the ground.

Though these bombs might be thought of as "bunker busters" today, the original "earthquake" theory was more complex and subtle than simply penetrating a hardened surface. The earthquake bombs were designed not to strike a target directly, but to impact beside it, penetrate under it, and create a 'camouflet', or large buried cavern, at the same time as delivering a shock wave through the target's foundations. The target then collapses into the hole, no matter how hardened it may be. The bombs had strong casings because they needed to travel through rock rather than reinforced concrete, though they could perform equally well against hardened surfaces. In an attack on the Valentin U-Boat pens at Farge, two Grand Slams went through the 15 ft (4.5 m) reinforced concrete hardening{{sfn|RAF staff|2005}}—equalling or exceeding the best current penetration specifications.

The British Disney bomb (officially "4500 lb [2,000 kg] Concrete piercing/Rocket Assisted Bomb", also known as the "Crab") was a World War II device designed to be used against U-boat pens and other super-hardened targets. Devised by Captain Edward Terrell RNVR of the Admiralty's Directorate of Miscellaneous Weapons Development,{{sfn|Terrell|1958|pp=197–212}} it had a streamlined hardened case and weighed about {{convert|4500|lb|abbr=on}} including the rocket assembly. The actual explosive content was about {{convert|500|lb|kg|abbr=on}}.

For accuracy, the bombs had to be dropped precisely from a pre-determined height (usually {{convert|20000|ft|m|abbr=on}}).{{harvnb|Burakowski|Sala|1960|p=556}} They would free-fall for around 30 seconds until, at {{convert|5000|ft|m|abbr=on}}, the rockets were ignited, causing the tail section to be expelled. The rocket burn lasted for three seconds and added {{convert|300|ft/s|m/s|abbr=on}} to the bomb's speed, giving a final impact speed of {{convert|1450|ft/s|m/s mph|abbr=on}},{{harvnb|Project Ruby|1946|p=18}} approximately Mach 1.29.Other sources mention a striking speed of {{convert|2400|ft/s|m/s mph|abbr=on}}. ({{harvnb|Johnsen|2003|p=45}}, {{harvnb|Burakowski|Sala|1960|p=556}}) Post-war tests demonstrated that the bombs were able to penetrate a {{convert|14|ft|8|in|m|adj=on}} thick concrete roof,{{harvnb|Project Ruby|1946|p=23}} with the predicted (but untested) ability to penetrate {{convert|16|ft|8|in|m}} of concrete.

Post war, the US added a form of remote guidance to the Tallboy to create the Tarzon, a {{convert|12,000|lb|kg|abbr=on}} bomb deployed in the Korean War against an underground command center near Kanggye.

Image:Alihangar1.jpg, Kuwait in 2005]]

The US BLU-109 bomb is intended to penetrate concrete shelters and other hardened structures before exploding. It entered service in 1985. Israeli F-15I fighter jets are believed to have used BLU-109s in the strikes that killed Hezbollah leader Hassan Nasrallah in Beirut on 27 September 2024.{{cite news |title=Israel likely used U.S.-made 2,000-pound bombs in Nasrallah strike, visuals show |url=https://www.washingtonpost.com/world/2024/09/29/israel-bomb-beirut-nasrallah-death/ |newspaper=The Washington Post |date=29 September 2024}}{{cite news |title= US-made 2,000-pound bombs likely used in strike that killed Hezbollah chief Nasrallah, CNN analysis shows|url=https://edition.cnn.com/2024/09/30/middleeast/israel-attack-nasrallah-2000-pound-bombs-intl/index.html |work=CNN |date=30 September 2024}}

During Operation Desert Storm (1991), there was a need for a deep penetration bomb similar to the British weapons of World War II, but none of the NATO air forces had such a weapon. As a stop-gap, some were developed over a period of 28 days, using old 8 inch (203 mm) artillery barrels as casings. These bombs weighed over two tons but carried only {{convert|647|lb|kg|abbr=on}} of high explosive. They were laser-guided and were designated "Guided Bomb Unit-28 (GBU-28)". It was proven effective for the intended role.{{Cite web|url=https://www.theweek.com/articles-amp/464752/why-pentagon-beefing-bunker-buster-bombs|title=Why the Pentagon is beefing up its 'bunker buster' bombs}}

An example of a Russian bunker buster is the KAB-1500L-Pr. It is delivered with the Su-24M and the Su-34 aircraft. It is stated to be able to penetrate 10–20 m of earth or 2 m of reinforced concrete. The bomb weighs {{convert|1500|kg|lb|abbr=on}}, with {{convert|1100|kg|lb|abbr=on}} being the high explosive penetrating warhead. It is laser guided and has a reported strike accuracy of {{convert|7|m|ft|abbr=on}} CEP.{{cite web|url=http://ausairpower.net/APA-Rus-GBU.html#mozTocId118525 |title=Soviet/Russian Guided Bombs |date=11 August 2009 |website=Air Power Australia |last1=Kopp |first1=Carlo }}

The US has a series of custom made bombs such as the Paveway series of laser-guided bombs to penetrate hardened or deeply buried structures:

More recently, the US has developed the {{convert|30,000|lb|kg|abbr=on}} GBU-57.

Turkey is another country known to be developing bunker busters, such as the SARB-83 and NEB-84.

File:USAF MOP test release crop.jpg during a test at White Sands Missile Range in New Mexico, U.S.]]

The traditional fuze is the same as a classic armor-piercing bomb: a combination of timer and a sturdy dynamic propeller on the rear of the bomb. The fuze is armed when the bomb is released, and detonates when the propeller stops turning and the timer has expired.

Modern bunker busters may use a traditional fuze, but some also include a microphone and microcontroller. The microphone listens, and the microcontroller counts the number of floors until the bomb breaks through the desired numbers of floors.

Northrop Grumman is working on the Hard Target Void Sensing Fuze (HTVSF), an electronic and cockpit programmable fuze capable of destroying deeply buried and targets. It provides multiple delay arming and detonation times, as well as a void-sensing capability, which allows for precision activation of the fuze for {{convert|2000|and|5000|lb|kg|adj=on}} weapons to explode when they reach an open space in a deeply buried bunker.{{cite web |url=http://www.globalsecurity.org/military/library/news/2011/04/mil-110405-atk01.htm |title=ATK Awarded Contract for Hard Target Void Sensing Fuze (HTVSF) Engineering & Manufacturing Development (EMD) Phase |work=ATK |date=5 April 2011 }}

{{cite web |url=https://news.northropgrumman.com/news/releases/northrop-grumman-awarded-110-million-for-us-air-force-hard-target-void-sensing-fuze |title=Northrop Grumman Awarded $110 Million for US Air Force Hard Target Void Sensing Fuze |website=Northrop Grumman Newsroom |date=February 28, 2020 |archive-url=https://web.archive.org/web/20200303153124/https://news.northropgrumman.com/news/releases/northrop-grumman-awarded-110-million-for-us-air-force-hard-target-void-sensing-fuze |archive-date=March 3, 2020 |url-status=dead }}

File:Image-GBU-24 Missile testmontage-gi BLU-109 bomb.jpg on a weapons test]]

The extra speed provided by a rocket motor enables greater penetration of a missile-mounted bunker buster warhead. To reach maximum penetration (impact depth), the warhead may consist of a high-density projectile only. Such a warhead carries more energy than a warhead with chemical explosives (kinetic energy of a projectile at hypervelocity).

{{main|Nuclear bunker buster}}

The nuclear bunker buster is the nuclear weapon version of the bunker buster. The non-nuclear component of the weapon is designed to greatly enhance the penetration into soil, rock, or concrete to deliver a nuclear warhead to a target. These weapons would be used to destroy hardened, underground military bunkers deeply buried. In theory, the amount of radioactive nuclear fallout would be reduced from that of a standard, air-burst nuclear detonation because they would have relatively low explosive yield. However, because such weapons necessarily come into contact with large amounts of earth-based debris, they may, under certain circumstances, still generate significant fallout. Warhead yield and weapon design have changed periodically throughout the history of the design of such weapons. An underground explosion releases a larger fraction of its energy into the ground, compared to an explosion at or above the surface which releases most of its energy into the atmosphere.

• T-12 Cloudmaker
• Disney bomb
• Rochling shell
• Impact depth

{{reflist|group=lower-alpha}}

{{reflist|30em}}

• {{cite book |author=Air Proving Ground Command Eglin Field |date=31 October 1946 |title=Comparative Test of the Effectiveness of Large Bombs against Reinforced Concrete Structures (Anglo-American Bomb Tests – Project Ruby) |publisher=US Air Force |location=Orlando, Florida |url=https://apps.dtic.mil/sti/pdfs/ADA065940.pdf |access-date=9 June 2011 |ref={{harvid|Project Ruby|1946}} |archive-date=8 October 2012 |archive-url=https://web.archive.org/web/20121008041357/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA065940&Location=U2&doc=GetTRDoc.pdf |url-status=live }} "Running parallel with the development of large bombs was a project for obtaining high striking velocities by means of a rocket assisted 4,500-lb [2,000 kg] British bomb called the Disney. (...) As early as June 1945, the concrete V-weapon structure at Watten was used as a target".
• {{cite book |last1=Burakowski |first1=Tadeusz |first2=Aleksander |last2=Sala |year=1960 |title=Rakiety i Pociski Kierowane |trans-title=Rockets and guided missiles |language=pl |publisher= Wydawnictwo Ministerstwa Obrony Narodowej (Ministry Of National Defense Publishing House)|location=Warsaw |volume=Część 1 – Zastosowania (Volume 1 – applications) |pages=556–557 }} Figure 280, p. 558, provides a detailed diagram of the Disney bomb (with its internals).
• {{cite book |last=Johnsen |first=Frederick A. |year=2003 |title=Weapons of the Eighth Air Force |publisher=MBI Publishing |location=St. Paul, MN |isbn=0-7603-1340-7 |url=https://books.google.com/books?id=S5USfmKSCD4C&pg=PA45|page=45 }}
• {{Cite web |author=RAF staff |date=6 April 2005 |url=http://www.raf.mod.uk/bombercommand/grandslam.html |work=Royal Air Force Bomber Command 60th Anniversary |title=Grand Slam Raids |archive-url=http://webarchive.nationalarchives.gov.uk/20070706011932/http://www.raf.mod.uk/bombercommand/grandslam.html |archive-date=6 July 2007}}
• {{cite book |last=Terrell |first=Edward |year=1958 |title=Admiralty Brief: the story of inventions that contributed to victory in the Battle of the Atlantic |publisher=Harrap }}

• {{cite journal |last=Alekseevskii |first=V. P. |title=Penetration of a rod into a target at high velocity |journal=Combustion, Explosion, and Shock Waves (Fizika Goreniya i Vzryva) |year=1966 |volume=2 |issue=2 |pages=99–106 |doi=10.1007/BF00749237 |s2cid=97258659 |issn=0010-5082}}
• {{cite book |last=Bernard |first=Robert S. |title=Depth and Motion Prediction for Earth Penetrators |volume=ADA056701 |year=1978 |type=Report |publisher=Army Engineer Waterways Experiment Station Vicksburg |url=https://apps.dtic.mil/sti/pdfs/ADA056701.pdf |access-date=2015-12-07 |archive-date=2012-10-08 |archive-url=https://web.archive.org/web/20121008185905/http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA056701 |url-status=live }}
• {{cite book |last=Parsch |first=Andreas |title=Directory of U.S. Military Rockets and Missiles fitted with bunker busting bombs to extend distances and to have horizontal as well as vertical movement and control. (Appendix 4) |year=2006 |chapter-url=http://www.designation-systems.net/dusrm/app4/blu-106.html |access-date=27 June 2011 |chapter=Textron (Avco) BLU-106/B BKEP (Boosted Kinetic Energy Penetrator) }} US rocket-boosted submunition against runways and hardened aircraft shelters.
• {{cite book |last=Young |first=C.W. |title=Penetration equations |volume=SAND94-2726 |year=1997 |type=Report |location=Albuquerque NM |publisher= Sandia National Laboratories |url=https://fas.org/sgp/othergov/doe/lanl/lib-www/sand/972426.pdf |quote=This is a standalone report documenting the latest version of the Young/Sandia penetration equations and related analytical techniques to predict penetration into natural earth materials and concrete.}}
• {{cite book |last=Young |first=C.W. |title=The Development Of Empirical Equations For Predicting Depth Of An Earth Penetrating Projectile |volume=SC-DR-67-60 |year=1967 |type=Report |location=Albuquerque NM |publisher= Sandia National Laboratories }}

• [https://fas.org/man/dod-101/sys/smart/gbu-28.htm Guided Bomb Unit-28 (GBU-28) BLU-113 Penetrator]
• [http://news.bbc.co.uk/2/hi/science/nature/2970205.stm BBC: 'Bunker buster' missiles aim at Moon]
• [https://web.archive.org/web/20060426214022/http://alsos.wlu.edu/adv_rst.aspx?query=bunker+buster&selection=keyword&source=all&results=10 Annotated bibliography for nuclear bunker buster bombs from the Alsos Digital Library for Nuclear Issues]
• [https://web.archive.org/web/20071215044224/http://digital.library.unt.edu/govdocs/crs/search.tkl?q=%22bunker+busters%22&search_crit=fulltext&search=Search&date1=Anytime&date2=Anytime&type=form Read Congressional Research Service (CRS) Reports regarding Bunker Busters]
• [http://www.ucsusa.org/global_security/nuclear_weapons/nuclear-bunker-buster-rnep-animation.html Video against usage (produced by Union of Concerned Scientists)]
• [https://www.youtube.com/watch?v=XbtzpqZOtB8 Video of bunker buster bomb in action]
• [https://web.archive.org/web/20090123094119/http://www.shimon-yanowitz.com/afew/Tunnel-Busters.htm Tunnel buster bomb]

Category:Aerial bombs

Category:Anti-fortification weapons