Mark 7 Bomb
A SMaller, Lighter bomb
The Mark 7, which came out in the middle of the Korean War, borrowed much from the Mark V, but was smaller and designed to be carried by fighter-bomber aircraft, a major improvement in usefulness. As you can see in this unit, from the Hill Aerospace Museum in Utah, the Mark 7 is far less bulbous than earlier bombs. What is not readily visible is the weight: Only 1600 lbs, light by nuclear bomb standards.
Although this at first may appear to be a different view of the same bomb as the prior photograph, this Mark 7 is located at Wings Over the Rockies, an aerospace museum in Denver. Note here the tail of the bomb. The weapon could be carried by fighter-bombers but the bomb was still large for these aircraft and, at fifteen feet in length, long as well, leaving little clearance between the rear of the body of the bomb and the ground. Thus, the bottom fin was retractable and would extend during flight.
A nose-on view of the Mark 7, which was the first bomb to feature automatic core insertion. Some sources say the core was inserted into the front of the unit, others say the rear or from the side. Photo made at Wings Over the Rockies, in Denver.
This looks to be a training unit, located at the Nuclear Museum in Albuquerque. Note the small tabs on the fins–these were added to the design to impart spin to the weapon as it fell. Earlier models featured air brakes, which would flip out from the tail (all of the units here in my images have the fins). However, this unit seems to have something, I’m not sure what, that flips out, visible between the fins.
Another view of the Nuclear Museum’s Mark 7. Note the rectangular access panel that is absent on the other units.
This image, from the National Museum of the US Air Force, in Dayton, gives you a sense of the size of the bomb in relation to the aircraft. The bomb is certainly big but does appear to be about the same size as a large external fuel tank. In use the pilot would, in an attempt to escape from the blast, “drop” the bomb with an upward flying maneuver called “toss bombing” where the plane would approach the target at a low altitude and then would suddenly climb and launch the bomb, sending it higher after its release and then letting it arc down, gaining precious seconds to put distance between the aircraft and the explosion. A second possible maneuver, which probably sounded as crazy to the pilots at the time as it does today, was to launch the bomb even higher on that same upward flying maneuver so that the bomb actually traveled backwards from the previous direction of the plane. Crazy stuff, indeed.
A different and closer view of the Mark 7 at the Air Force Museum. The plane immediately behind the bomb is the Republic F84F, a primary platform for the Mark 7. Behind that plane is the Boeing KC-97L Starfreighter, an in-flight refueling plane (basically a modified B-29). A B-29 could carry only a single Fat Man bomb due to the bomb’s size and 10,000 pound weight. The Mark 7 was so much smaller and lighter, and therefore so much more useful. Between 1645 and 1700 were built (and used by all three military services in the US, a first) and a warhead version was used in the Corporal missile, the Honest John rocket, and others.
Many airplanes modeling kits in the past included nuclear armament–not as common nowadays. The Travis AFB Aviation Museum, where this one is found, had at least eight small models of nuclear weapons.
Explosive Power
18 to 61 kt.
Hiroshima Equivalent Factor
1.2x to 4x
Dimensions
15 feet x 30 inches
Weight
1600 lbs.
Year(s)
1952-1967
Purpose
Smaller, lighter bomb
Nukemap
NUKEMAP is a web-based mapping program that attempts to give the user a sense of the destructive power of nuclear weapons. It was created by Alex Wellerstein, a historian specializing in nuclear weapons (see his book on nuclear secrecy and his blog on nuclear weapons). The screenshot below shows the NUKEMAP output for this particular weapon. Click on the map to customize settings.
Videos
Click on the Play button and then the Full screen button on the lower right (the brackets on a mobile device) to view each video. Click on the Exit full screen button (the “X” on a mobile device) to return.
Further Reading
- Wikipedia, GlobalSecurity.org, and Nuclear Compendium.
- The quote in the essay (above) comes from Bob Considine’s book, General Douglas MacArthur, published in 1964, as quoted in “Douglas MacArthur’s Plan to Win The Korean War” at Warfare History Network. Other information in the essay is drawn from “How the Korean War Almost Went Nuclear” by Carl A. Posey in the Smithsonian’s Air and Space Magazine.
- A New York Times article, published in 1964 indicated that the plan to use Cobalt 60 as a radioactive barrier in Korea was “said to have been supported by Drs. Ernest O. Lawrence, Edward Teller and others associated with atomic research at the University of California. It was seen as a way of ‘sanitizing’ a region without damage to property or loss of life.”
- The Mark 7 bomb was the one of first tactical nuclear weapons, intended to be carried by smaller, short-ranged aircraft and to attack targets nearer to friendly troops. The Council on Strategic Risks has a primer on what makes a weapon “tactical” (vs. “strategic”), offers a short history of tactical nuclear weapons, and includes interesting charts in the numbers and variety of weapons over time.
- “The Secret History of America’s Tactical Nukes,” by Jonathan Guyer, published in Vox in 2022, touches on the history of tactical nuclear weapons and makes the important point that the distinction between ‘tactical” and “strategic” nuclear weapons only came about much later with the negotiations of the arms control agreements.
- The 20th Fighter Wing, became, in 1951, the first unit to carry the Mark 7. “Victor Alert” by Rebecca Grant in Air Force Magazine, tells the story of the unit, soon stationed in Europe, and its role in US nuclear defense strategy.
- Robert F. Dunn (retired as Vice Admiral in the US Navy) recounts his time as a pilot in the 1950s learning the demanding (and, apparently, fun) lofting and over-the-shoulder maneuvers used to drop a Mark 7 in his article, “The Bomb and I,” published at the US Naval Institute. Here is a game simulation video of the maneuver and a video of a real airplane giving it a try.
- “The One-Way Nuclear Mission,” by John Lowery in Air Force Magazine in 2017 offers a clear graphic illustrating the toss-bomb technique with a Mark 7.
- The Mark 7 was tested in a live bomb drop in Nevada on November 1, 1951. The film, “Buster Jangle,” put out by the USAF Lookout Mountain Laboratory in Hollywood, documents (and recreates) this series of tests, of which Buster-Easy used the Mark 7 (start at 46:30 for the Buster-Easy portion of the film). Here is a fact sheet on Buster-Jangle by the Defense Threat Reduction Agency and another video angle on the detonation and yet another and still one more. Also, see the 1982 Defense Nuclear Agency’s history of the Buster-Jangle tests and the tests’ summary at the Nuclear Weapons Archive.
- The now unclassified “History of the Mk 7 Warhead” from August 1967 (collected in the Pfeiffer Nuclear Weapon and National Security Archive) is the Sandia National Lab’s own historical record of the Mark 7 and the other weapons in which its warhead version (the W-7) were used.
- There are far too many nuclear accidents and near accidents to go into detail here on American Nukes but note the list by Kelly M. in the comments to this post which cites an accident with a Mark 7.
- Want to build your own scale model of the Mark 7? You have several choices but the best I’ve found is an early version (1984) of Monogram’s kit #5432, which is a kit of the Republic Aviation F-84F Thunderstreak fighter-bomber–it comes with a Mark 7 as part of its optional armament.
- The warhead version of the Mark 7 was used in the Corporal missile, the Honest John rocket, the BOAR rocket (which also used the entire front of the Mark 7), and the Betty nuclear depth-charge. [Links to American Nukes forthcoming.]