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Updated December 21, 2021
Defense Primer: Ground Based Strategic Deterrent
(GBSD) Capabilities
Figure 1. Notional GBSD Launch
flight. The same is true for nuclear missiles launched from
U.S. submarines. In contrast, U.S. bombers could return to
their bases after launch, without releasing their weapons,
although the weapons could not be recalled after their
release from the bomber.
Status of Minuteman III
The U.S. Air Force first deployed Minuteman ICBMs in the
1960s. Minuteman III, the first of the class to carry multiple
warheads, entered the force in the early 1970s. The Air
Force has replaced and updated many of the component
systems on the missile—a process known as life-
extension—several times over the past 50 years. The most
recent life-extension program occurred in the late 2000s and
Source: https://www.northropgrumman.com/GBSD/
included, among other things, a replacement booster and a
.
new missile guidance computer. The Air Force has noted
The Ground Based Strategic Deterrent (GBSD) is intended
that both of these components may face reliability concerns
to replace the Minuteman III (MMIII) Intercontinental
as they reach the end of their intended lifespans over the
Ballistic Missile (ICBM) in the U.S. nuclear force structure.
next decade (see Figure 2). After conducting a
MMIII has been deployed as the ground-based leg of the
comprehensive Analysis of Alternatives (AOA) in 2014, the
U.S. nuclear triad—land-based ballistic missiles,
Air Force determined that it would replace MMIII with a
submarine-launched ballistic missiles, and nuclear-capable
new missile system. When compared with a life-extended
bombers—since 1970. (For details, see CRS Report
Minuteman III, the replacement system (the Ground Based
RL33640, U.S. Strategic Nuclear Forces: Background,
Strategic Deterrent, GBSD) would meet current and
Developments, and Issues, by Amy F. Woolf.) The Air
expected threats, maintain the industrial base, insert more
Force expects GBSD to begin replacing MMIII in 2029. As
reliable technology, produce a modular weapon system
the missile moves toward production and deployment,
concept, and reduce life cycle cost.
issues for Congress include whether to authorize and
appropriate funding for this program and, if so, whether to
Figure 2. Projected Decrease in Operational
provide oversight as the program progresses and is
Minuteman III Missiles
implemented.
What Is an ICBM?
The United States began deploying nuclear-armed
intercontinental ballistic missiles in 1959, and it has
maintained these systems “on alert” in a position to launch
promptly since that time. Missiles designated as ICBMs are
those that have been tested to a range greater than 5,500
km, or roughly 3,400 miles. Although some countries use
road or rail mobile launchers for their ICBMs, U.S. ICBMs
are based in hardened concrete silos, known as launch
Source: Mark Gunzinger, Carl Rehberg, and Gil ian Evans, Sustaining
facilities, located in North Dakota, Montana, Wyoming,
the U.S. Nuclear Deterrent: The LRSO and GBSD, Center for
Colorado, and Nebraska. An ICBM can reach targets
Strategic and Budgetary Assessments.
around the globe in approximately 30 minutes after launch.
During the first three minutes, the missile’s flight is
Capabilities of GBSD
powered by three solid fuel rocket motors. After the
powered portion of flight, the missile follows a parabolic
Modularity: What Is It and Why Is It Important in
trajectory toward its target. It releases its warhead during
Lowering Lifecycle Costs?
the mid-course portion of its flight, and the warhead
In contrast with MMIII missiles, the GBSD employs a
continues to the target.
modular design and open architecture, allowing for the
replacement of aging and outdated components. According
Once the President authorizes the launch of any U.S.
to the Air Force, this modular approach would reduce the
nuclear-armed missile, it cannot be recalled or destroyed in
lifecycle cost of GBSD and provide flexibility for
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Defense Primer: Ground Based Strategic Deterrent (GBSD) Capabilities
improvements throughout the life of the weapon system.
Improved Throw Weight
Unlike in many current DOD systems, open systems
The MMIII engines use heavy steel casings to house the
architectures allow the Air Force to control the intellectual
missile propellant. These casings add to the weight of the
property of the system, including the system’s source code.
missile and affect its flight range and payload capabilities.
This allows multiple vendors, in addition to the contract
Modern rocket boosters, like the Navy’s D5 Submarine
winner Northrop Grumman, to compete for and complete
Launched Ballistic Missile, use composite material to save
future upgrades and improvements to the system. These
weight and increase potential payload. GBSD’s boosters
types of upgrades might become important as technology
use a composite material, making GBSD significantly
evolves and could allow for improvements in the safety and
lighter than the MMIII. Most notably, this will increase the
reliability of the missile system. They could include better
missile’s throw weight, which is a measure of the weight of
guidance systems or new types of countermeasures that
the payload that the missile can deliver to a particular
might allow the missile to penetrate an adversary’s ballistic
range. The Air Force asserts that the greater throw weight
missile defensive systems.
will allow GBSD to carry different payloads and give it
more flexibility for future missions. Specifically, as
Consequently, modularity may provide benefits in the
adversaries develop ballistic missile defensive systems in
maintenance of a weapon system because it would allow
the future, the increased throw weight could potentially
the Air Force to modify and possibly improve the initial
allow the Air Force to develop countermeasures that would
design of the missile by upgrading and replacing smaller
help the missile overcome the defenses.
systems, of modules, without redesigning the entire weapon
system. This could potentially be a more cost-effective way
The Air Force plans to deploy the GBSD with one warhead
to support the missile’s intended 50-year life cycle than the
per missile. However, with the greater throw weight
life extension programs that replaced aging parts in the
available on GBSD, the Air Force could, potentially, deploy
MMII. Also, the Air Force would not have to go back and
it with two or three warheads per missile in response to
pay the original vendor to open software to add the new
changes in the international security environment.
piece into the system architecture in the future.
Moreover, some argue that if the Air Force deployed
multiple warheads on each missile, it might be able to meet
Improved Security
targeting requirements with a smaller number of deployed
The Air Force has noted that, with MMIII, most of the
missiles. Currently, the United States disperses single-
maintenance conducted on the warhead or the Missile
warhead missiles across a large area of the upper Midwest,
Guidance Computer currently requires that the launcher
which both reduces the value of each individual missile and
closure door (the access door directly above the missile) be
complicates an adversary’s ability to attack the entire force.
open. This introduces a security vulnerability by increasing
A smaller number of multiple warhead missiles could
the possibility of unauthorized observation or access. To
change this calculus but also might provide a less costly
counter this, during MMIII maintenance operations, the Air
alternative for the GBSD force.
Force assigns additional Security Forces to the crew to help
protect the warhead. With the modular design of GBSD,
Considerations for Congress
much of the maintenance can be conducted with the
Some Members of Congress have questioned the need to
launcher closure door closed. The Air Force states that
fund and deploy GBSD missiles; some have suggested that
deploying the GBSD would mitigate the security risks
the Air Force consider, again, whether it could life extend
during maintenance compared to the current MMIII.
the Minuteman III instead. They, along with analysts
outside government, have argued that a delay in GBSD
Potential Manpower Savings
could ease financial pressures caused by the simultaneous
The three current MMIII bases in the Air Force (Minot
recapitalization of U.S. land-based, sea-based, and air-
AFB, Malmstrom AFB, and FE Warren AFB) require
delivered nuclear weapons. The Congressional Budget
greater numbers of security forces personnel compared with
Office (CBO) has estimated that the three major
other units in the Air Force. The GSBD’s modularity that
programs—the GBSD, the Columbia Class submarines, and
enables most maintenance to be done with the launcher
the B-1 bomber—could cost $234 billion over the next
closure door closed might also allow for a reduction in the
decade. Some analysts outside government and some
number of Security Forces personnel required at the bases.
former defense officials have also suggested that the United
In addition to fewer required Security Forces, the Air Force
States reduce or eliminate its ICBMs because their
expects the maintenance needs of a new weapon system to
vulnerability to attack could make them destabilizing in a
be greatly reduced. Finally, although the final layout of how
crisis. On the other hand, those who support the GBSD
the system will be set up has not been publicized, there are
program have noted that every Nuclear Posture Review
indications to suggest that fewer Launch Control Centers
conducted since the end of the Cold War has endorsed the
(LCCs) will be required. Current requirements have 15
nuclear triad, with President Obama’s 2010 NPR stating
LCCs at each of the three missile bases for a total of 45
that “retaining all three Triad legs will best maintain
LCCs. Each LCCs is manned continuously by two missile
strategic stability at reasonable cost, while hedging against
combat crew members. If fewer LCCs are needed in GBSD,
potential technical problems or vulnerabilities.”
it could lead to the need for fewer missile operators. It is
premature to estimate the potential total manpower savings,
Benji Johnson, U.S. Air Force Fellow
but it may be reasonable to assume there will be some.
Amy F. Woolf, Specialist in Nuclear Weapons Policy
IF11681
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Defense Primer: Ground Based Strategic Deterrent (GBSD) Capabilities
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