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November 10, 2020
Defense Primer: Ground Based Strategic Deterrent
(GBSD) Capabilities
Figure 1. Notional GBSD Launch
Status of Minuteman III
MMIII first entered service around 1970 and has undergone
several life extension programs over the past 50 years, the
most recent of which occurred in the late 2000s and
included a replacement booster and missile guidance
computer. In the next decade, both of these components
may face reliability concerns as they reach the end of their
intended lifespan, known as aging out, as indicated in
Figure 2. A 2016 Pentagon study recommended replacing
MMIII rather than conducting another life extension. The
study concluded that the replacement system (GBSD)
would meet current and expected threats, maintain the
industrial base, insert more reliable technology, produce a
modular weapon system concept, and reduce life cycle cost.
Source: https://www.northropgrumman.com/GBSD/
Figure 2. Projected Decrease in Operational
Minuteman III Missiles
On September 8, 2020, the United States Air Force awarded
Northrop Grumman Corporation a $13.3 billion contract to
develop a new nuclear missile, the Ground Based Strategic
Deterrent (GBSD), intended to replace the 50-year old
Minuteman III (MMIII) Intercontinental Ballistic Missile
(ICBM). (For details on the U.S. nuclear force structure, see
CRS Report FL33640, U.S Strategic Nuclear Forces:
Background, Developments, and Issues, by Amy Woolf.)
MMIII has been deployed as the ground-based leg of the
U.S. nuclear forces structure (the “Triad”) since 1970. The
Air Force expects GBSD to begin replacing MMIII in 2029.
As the missile moves toward production and deployment,
Source: Mark Gunzinger, Carl Rehberg, and Gil ian Evans, Sustaining
issues for Congress include whether to authorize and
the US Nuclear Deterrent: The LRSO and GBSD, Center for
appropriate funding for this program and, if so, to provide
Strategic and Budgetary Assessments.
oversight as the program progresses and is implemented.
Capabilities of GBSD
What Is an ICBM?
According to the Department of Defense (DOD), an ICBM
Modularity: What Is It and Why Is It Important in
is a missile that has a minimum range of 5,500 km, or
Lowering Lifecycle Costs?
roughly 3,400 miles. Although some countries use road or
In contrast with MMIII missiles, the GBSD employs a
rail mobile launchers for their ICBMs, U.S. ICBMs are silo
modular design and open architecture, allowing for the
based; they are buried in protective launch facilities in
replacement of aging and outdated components. According
North Dakota, Montana, Wyoming, Colorado, and
to the Air Force, this modular approach would reduce the
Nebraska. An ICBM can hit its target on another continent
lifecycle cost of GBSD and provide flexibility for
in approximately 30 minutes. During the first three minutes,
improvements throughout the life of the weapon system.
the missiles flight is powered by its three-stage solid fuel
Unlike in many current DOD systems, open systems
motors. After the powered portion of flight, it follows a
architectures allow the Air Force to control the intellectual
ballistic trajectory toward its target, on a parabolic
property of the system, including the system’s source code.
trajectory. Once the President authorizes the launch of a
This allows multiple vendors, in addition to the contract
missile, it cannot be recalled or destroyed in flight. The
winner Northrop Grumman, to compete for and complete
same is true for nuclear missiles launched from U.S.
future upgrades and improvements to the system. These
submarines. In contrast, U.S. bombers could return to their
types of upgrades might become important as technology
bases after launch, without releasing their weapons,
evolves and could allow for improvements in the safety and
although the weapons could not be recalled after their
reliability of the missile system. They could include better
release from the bomber.
guidance systems or new types of countermeasures that
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Defense Primer: Ground Based Strategic Deterrent (GBSD) Capabilities
might allow the missile to penetrate an adversary’s ballistic
missile and affect its flight range and payload capabilities.
missile defensive systems.
Modern rocket boosters, like the Navy’s D5 Submarine
Launched Ballistic Missile, use composite material to save
Consequently, modularity may provide benefits in the
weight and increase potential payload. GBSD’s boosters
maintenance of a weapon system because it would allow
use a composite material, making GBSD significantly
the Air Force to modify and possibly improve the initial
lighter than the MMIII. Most notably, this will increase the
design of the missile by upgrading and replacing smaller
missile’s throw weight, which is a measure of the weight of
systems, of modules, without redesigning the entire weapon
the payload that the missile can deliver to a particular
system. This could potentially be a more cost-effective way
range. The Air Force asserts that the greater throw weight
to support the missile’s intended 50-year life cycle than the
will allow GBSD to carry different payloads and give it
life extension programs that replaced aging parts in the
more flexibility for future missions. Specifically, as
MMII. Also, the Air Force would not have to go back and
adversaries develop ballistic missile defensive systems in
pay the original vendor to open software to add the new
the future, the increased throw weight could potentially
piece into the system architecture in the future.
allow the Air Force to develop countermeasures that would
help the missile overcome the defenses.
Improved Security
The Air Force has noted that, with MMIII, most of the
At this time, the Air Force does not plan to deploy the
maintenance conducted on the warhead or the Missile
GBSD with more than one warhead per missile. However,
Guidance Computer currently requires that the launcher
the added throw weight could preserve that option for the
closure door (the access door directly above the missile) be
future. If it deployed multiple warheads on each missile, the
open. This introduces a security vulnerability by increasing
Air Force might be able to deploy fewer missiles but still
the possibility of unauthorized observation or access. To
cover the same number of targets. Currently, the United
counter this, during MMIII maintenance operations, the Air
States disperses single-warhead missiles across a large area
Force assigns additional Security Forces to the crew to help
of the upper Midwest, which both reduces the value of each
protect the warhead. With the modular design of GBSD,
individual missile and complicates an adversary’s ability to
much of the maintenance can be conducted with the
attack the entire force. A smaller number of multiple
launcher closure door closed. The Air Force states that
warhead missiles could change this calculus but also might
deploying the GBSD would mitigate the security risks
provide a less costly alternative for the GBSD force.
during maintenance compared to the current MMIII.
Considerations for Congress
Potential Manpower Savings
There are objections to authorizing and funding the GBSD
The three current MMIII bases in the Air Force (Minot
that come from both some Members of Congress and
AFB, Malmstrom AFB, and FE Warren AFB) require
former defense officials who argue that nuclear weapons
greater numbers of security forces personnel compared with
are outdated and ICBMs are destabilizing. Other critics note
other units in the Air Force. The GSBD’s modularity that
the costs of the “nuclear bow-wave” during the
enables most maintenance to be done with the launcher
modernization scheduled over the next decade that a 2019
closure door closed could also allow for a reduction in the
CBO study estimated to be $234 billion for just the three
number of Security Forces personnel required at the bases.
major programs: B-21 Bomber, submarine, and ICBM.
In addition to fewer required Security Forces, the Air Force
Some argue that cutting down from a Triad to a Dyad may
expects the maintenance needs of a new weapon system to
be the best way to help control costs while still maintaining
be greatly reduced. Finally, although the final layout of how
a nuclear deterrent force. That would likely mean
the system will be set up has not been publicized, there are
eliminating the ICBM leg and cancelling the GBSD
indications to suggest that fewer Launch Control Centers
program. The Air Force notes President Obama’s 2010
(LCCs) will be required. Current requirements have 15
Nuclear Posture Review, which stated, “Retaining all three
LCCs at each of the three missile bases for a total of 45
Triad legs will best maintain strategic stability at reasonable
LCCs. Each LCCs is manned continuously by two missile
cost, while hedging against potential technical problems or
combat crew members. If fewer LCCs are needed in GBSD,
vulnerabilities.” If Congress chooses to fund this program,
it could lead to the need for fewer missile operators. It is
potentially one of the biggest challenges would be to ensure
premature to estimate the potential total manpower savings,
the program stays on schedule and on budget.
but it may be reasonable to assume there will be some.
Benji Johnson, U.S. Air Force Fellow
Improved Throw Weight
The MMIII engines use heavy steel casings to house the
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missile propellant. These casings add to the weight of the
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Defense Primer: Ground Based Strategic Deterrent (GBSD) Capabilities
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