Ground Based Strategic Deterrent

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Lorenzo von Matterhorn
Jan 31, 2009
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Ground Based Strategic Deterrent
The Ground Based Strategic Deterrent (GBSD) is a US land-based intercontinental ballistic missile system in the early stages of development, slated to replace all 450 Minuteman III missiles in service with the United States Air Force from 2027 onward.


A request for proposal for development and maintenance of a next-generation nuclear ICBM was made by the US Air Force Nuclear Weapons Center, ICBM Systems Directorate, GBSD Division in July 2016. The GBSD would replace the Minuteman III in the land based portion of the US nuclear triad. The new missiles, to be phased in over a decade from the late 2020s, are estimated over a fifty-year life cycle to cost around $86 billion. Boeing and Northrop Grumman competed for the contract. In August 2017, the Air Force awarded 3-year development contracts to Boeing and Northrop Grumman for $349 million and $329 million, respectively. One of these companies was to be selected to produce a ground-based nuclear ICBM in 2020. In 2027, the GBSD program is expected to enter service and remain active until 2075.

On 25 July 2019, Boeing announced it would not place a bid for the program, citing Northrop's recent acquisition of Orbital ATK (now Northrop Grumman Innovation Systems), Boeing's supplier of solid rocket motors. Northrop signed an agreement to firewall Boeing's proprietary data after acquiring Orbital ATK. The Air Force has since halted funding for the Boeing project, leaving only Northrop Grumman as a bidder.

In December 2019, it was announced that Northrop Grumman won the competition to build the future ICBM. Northrop won by default, as their bid was the only bid left to be considered for the GBSD program. The Air Force said that they will "proceed with an aggressive and effective sole-source negotiation" in reference to Northrop's bid.


In March 2019 the W87 mod 1 thermonuclear warhead was selected for GBSD, replacing the W78 warhead currently used in Minuteman III. It is unclear if the W78 will be fitted to GBSD or if some other arrangement such as moving W87-0s to GBSD first will be made, but the estimated first production unit date was moved to 2030, a delay from the initial estimated entry into service date of 2027.

The W78 thermonuclear warhead is the warhead used on most of the United States LGM-30G Minuteman III intercontinental ballistic missiles (ICBMs), along with the MK-12A reentry vehicle which carried the warhead. Minuteman IIIs initially deployed with the older W62 warhead; the W78 was deployed starting in December 1979 onto 300 missiles, three warheads per missile. Declassified records indicate a total of 1,083 W78s were produced.

The W78 was designed at Los Alamos National Laboratory starting in 1974. The design is thought to combine the secondary (fusion) stage design of older ICBM warheads such as the W50 with a more modern primary stage (see Teller-Ulam design for more details).

The W78 has a publicly announced yield of 335–350 kilotons of TNT (1.40–1.46 PJ).

Dimensions of the W78 are unknown, but it fits within the MK-12A reentry vehicle, which is conically shaped, 21.3 inches in diameter at its base and 71.3 inches long. The W78 is estimated to weigh 700–800 pounds (317–363 kg).

The W78 Lives On
Joint Test Assembly flight tests evaluate the Minuteman III’s aging warhead. The W78 warhead, which was designed by Los Alamos and is one of the two types used to arm Minuteman III ICBMs, will turn 40 in 2019. One way to evaluate the health of the aging W78 is by Joint Test Assembly (JTA) flight tests. These joint Department of Energy-Department of Defense tests gather key data from the sophisticated sensors inside the missile, the reentry vehicle (RV), and the W78 warhead tucked inside the RV. These data provide weapons scientists and engineers a way to assess the warhead’s ability to survive and function while traveling through multiple severe environments: the extreme violence of launching; accelerating within seconds to Mach 23 (about 18,000 miles per hour); entering the frigid vacuum of space; then reentering the atmosphere at speeds that threaten to break up or burn up the reentry vehicle and its warhead.

The key to a JTA, however, is that it uses a mock nuclear warhead: surrogate materials have replaced all of the nuclear materials inside. For example, the W78’s plutonium pit is replaced with a pit of non-nuclear material, making this mock-warhead incapable of generating any nuclear yield. The mock warhead is otherwise all but identical to a real warhead. All types of nuclear warheads are flight-tested using JTAs. Because Los Alamos designed the W78 (and the W88, W76, and B61 warheads), it provides the mock warheads for those JTA flight-tests. Although the mock warhead is technically a “dud,” JTAs are still one of the best ways to provide confidence that the W78 remains safe, secure, and reliable.

W87-1 Modification Program
NNSA resumed work on a W78 warhead replacement, designated as the W87-1, in fiscal year (FY) 2019 following the 2018 Nuclear Posture Review. By replacing the legacy W78, the W87-1 will maintain continuity for the ground-based leg of the U.S. nuclear deterrent. The warhead is named the W87-1 to reflect that it has a similar primary design to the W87-0 and will fly in a similar reentry vehicle. The W87-1 is based on a previously-tested nuclear component and will include an insensitive high explosive primary that had been designed and tested with advanced safety features. The warhead will be fielded by FY 2030 on the U.S. Air Force (USAF)’s Ground Based Strategic Deterrent. The W87-1 will not provide new military capabilities, yet it will provide enhanced safety and security compared to the legacy W78. The W87-1 will be certified without the need for additional underground nuclear explosive testing.

Air Force Eyes Adding Nuclear-Armed Hypersonic Boost-Glide Vehicles To Its Future ICBMs
At present, all other hypersonic weapons of this type that the US military is developing are conventionally armed.
AUGUST 19, 2020
The U.S. Air Force is at least researching what it might take to develop a nuclear-armed hypersonic boost-glide vehicle with a range equivalent to a traditional intercontinental ballistic missile, or ICBM. This vehicle could potentially go on top of the service's future Ground-Based Strategic Deterrent ICBMs, which are now in development. Publicly, the hypersonic weapons programs now in progress across the U.S. military are all conventionally-armed.

Aviation Week was first to report on this potential nuclear hypersonic weapon effort on Aug. 18, 2020, based on information the Air Force Nuclear Weapons Center had included in a request for information posted online six days earlier. That document, which was marked "For Official Use Only" and has since been taken offline, outlined seven potential upgrade tracks for an ICBM with a “modular open architecture."

This is understood to refer to the forthcoming Ground-Based Strategic Deterrent (GBSD), because the existing Minuteman III IBCM was not designed with these features in mind. One of those areas of interest is “thermal protection system that can support [a] hypersonic glide to ICBM ranges."

"GBSD does have an open architecture. It gives us an ability to incorporate emerging technologies we need to counter whatever threats we face in the future," Air Force Lieutenant General Richard Clark, the Deputy Chief of Staff for Strategic Deterrence and Nuclear Integration, said in response to a specific question about a potential nuclear-armed hypersonic payload during a virtual event hosted by the Air Force Association's Mitchell Institute on Aug. 19, 2020. "So as we bring the system [GBSD] online, we will ensure that we have the ability to roll different technologies in and incorporate that into GBSD."

In response to a follow-up question from Steve Trimble, Aviation Week's Defense Editor and good friend of The War Zone, Clark explicitly said that a nuclear-armed hypersonic boost-glide vehicle was not in the minimum "threshold" requirements for the GBSD program. However, as Trimble astutely pointed out, this only raises questions about what the program's more ambitious "objective" requirements might include.

Maneuverable reentry vehicle
Advanced Maneuverable Reentry Vehicle (AMaRV) was a prototype MARV built by McDonnell-Douglas Corp. Four AMaRVs were made and represented a significant leap in Reentry Vehicle sophistication. Three of the AMaRVs were launched by Minuteman-1 ICBMs on 20 December 1979, 8 October 1980 and 4 October 1981. AMaRV had an entry mass of approximately 470 kg, a nose radius of 2.34 cm, a forward frustum half-angle of 10.4°, an inter-frustum radius of 14.6 cm, aft frustum half angle of 6°, and an axial length of 2.079 meters. No accurate diagram or picture of AMaRV has ever appeared in the open literature. However, a schematic sketch of an AMaRV-like vehicle along with trajectory plots showing hairpin turns has been published.

AMaRV's attitude was controlled through a split body flap (also called a "split-windward flap") along with two yaw flaps mounted on the vehicle's sides. Hydraulic actuation was used for controlling the flaps. AMaRV was guided by a fully autonomous navigation system designed for evading anti-ballistic missile (ABM) interception.

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.




Northrop Wins $13.3B Contract to Design New ICBMs
Sept. 8, 2020
Northrop’s design for the Ground-Based Strategic Deterrent will replace the 400 Minuteman III missiles that are scattered in silos around Montana, North Dakota, and Wyoming, as well as 200 or so additional missiles used as replacements, for testing, and for other development.

The contract covers weapon system design, qualification, test and evaluation, and nuclear certification, Northrop said in a Sept. 8 release. Missiles are supposed to be ready for initial deployment by 2029.

The Air Force will start construction to accommodate the new weapons at F.E. Warren Air Force Base, Wyo., as soon as 2023, followed by Malmstrom Air Force Base, Mont., in 2026, and Minot Air Force Base, N.D., in 2029. Northrop will begin delivering missiles in fiscal 2029 if the program remains on track.

Research and development is slated to cost nearly $22 billion overall, not including the cost of purchasing the missiles. An independent Pentagon cost estimate pegged the price tag around at least $85 billion, though it could eventually total much more.

The Air Force touts GBSD as a forward-looking program that is paving the way for new military techniques in three-dimensional printing and rapid software upgrades. Those features could make it possible to add a more maneuverable, hypersonic warhead in the future.

The missiles are expected to last until 2075 as the United States enters a new era in nuclear deterrence with Russia, China, North Korea, and other nuclear states.

“The increased accuracy, extended range, and improved reliability will provide the United States a broader array of options to address unforeseen contingencies, giving us the edge necessary to compete and win against any adversary,” Gen. Timothy M. Ray, head of Air Force Global Strike Command, said in a release.

GBSD is one piece of the Air Force’s broad effort to overhaul its nuclear arsenal. It is also buying a new nuclear bomber, Northrop’s B-21; buying new air-launched cruise missiles known as the Long-Range Standoff Weapon from Lockheed Martin or Raytheon; creating a new variant of the B61 gravity bomb; outfitting the F-35 Joint Strike Fighter to carry nuclear weapons; and designing a modern network to control and communicate with nuclear forces.