Mk 21A reentry vehicle


Lorenzo von Matterhorn
Jan 31, 2009
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Boeing Fears End Of Its Work On New Air Force ICBM As Lockheed Wins Reentry Vehicle Deal
Boeing has publicly questioned the Air Force's contracting processes and a formal protest could lead to delays in the development of the new ICBMs.
23 Oct 2019

Lockheed Martin has won a new contract to mature the technology and conduct risk reduction work on the Mk 21A reentry vehicle, which will carry a W87-1 nuclear warhead and sit atop the U.S. Air Force's future intercontinental ballistic missile, or ICBM. The missile is under development now under the Ground Based Strategic Deterrent program, or GBSD. This comes amid turmoil in the GBSD effort, with Boeing recently announcing that the Air Force effectively canceled its contract related to that missile, making Northrop Grumman the de facto winner of the competition.

The Air Force awarded the Mk 21A contract on Oct. 23, 2019, according to a press release from Lockheed Martin. The deal is worth approximately $108 million over the next three years, but includes a provision for a one-year option after that, valued at another $30 million. The United States originally developed the Mk 21, armed with the W87 warhead, for the LGM-118A Peacekeeper ICBM, but began using them on the LGM-30G Minuteman III after the Peacekeeper's retirement in 2005. The W87-1 that GBSD ICBMs will use is a product improved version of the older warhead that is safer and more reliable thanks to the use of insensitive explosives, but most of the exact specifics of the updates are classified.


The W87 is an American thermonuclear missile warhead. It was created for use on the LGM-118A Peacekeeper ICBM, 50 of which, with up to 10 warheads per missile, were deployed 1986–2005. Starting in 2007, 250 of the W87 warheads from now-retired Peacekeeper missiles were retrofitted onto much older Minuteman III missiles, with one warhead per missile.[1]

Design of the W87 started in February 1982 at Lawrence Livermore National Laboratory and production of the warhead began in July 1986 and ended in December 1988.[2] Its design is reportedly somewhat similar to the W88, though that warhead was designed at Los Alamos National Laboratory. The weapons were refurbished for a lifespan by the National Nuclear Security Administration's Life Extension Program.[3]

The W87 design includes all modern safety features, including the insensitive high explosives LX-17 and PBX-9502 (primary component TATB), a fire-resistant pit, and advanced arming and fuzing safety features.

The original yield of the W87 was 300 kilotons, but has the announced ability to be upgraded to a yield of 475 kilotons, presumably by using more HEU in the fusion secondary stage tamper. It is not known if that upgrade was completely tested and ready to implement, or merely designed.
[allowed by the technologically beautiful testing infrastructure I've previously linked to here involved in the cough, cough, "Life Extension Program" and the supercomputer simulations enabled by that program? I'd bet so. - W]

The exact dimensions of the W87 are classified, but it fits inside the Mk. 21 reentry vehicle, which is a cone with base diameter of 22 inches (56 cm) and a length of 69 inches (180 cm). The weight is believed to be between 440 and 600 pounds (200 and 270 kg).