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Hypersonic Missile Defense: Issues for Congress
The Missile Defense Agency (MDA) and Space
Development Agency (SDA) are currently developing
elements of a hypersonic missile defense system to defend
against hypersonic weapons and other emerging missile
threats. These elements include the tracking and transport
layers of the Proliferated Warfighter Space Architecture
(PWSA) and various interceptor programs. As MDA and
SDA continue to develop these systems, Congress may
consider implications for oversight and defense
authorizations and appropriations.
Background
Hypersonic weapons, like ballistic missiles, fly at speeds of
at least Mach 5, or roughly 1 mile per second. Unlike
ballistic missiles, hypersonic weapons do not follow a
ballistic trajectory and can maneuver en route to their
target. Russia reportedly fielded its first hypersonic
weapons in December 2019, while some experts believe
that China fielded hypersonic weapons as early as 2020.
The United States does not have any fielded hypersonic
weapons. (For an overview of hypersonic weapons
programs in Russia, China, and the United States, see CRS
Report R4581 1, Hypersonic Weapons: Background and
Issuesfor Congress, by Kelley M. Sayler.)
The maneuverability and low flight altitude of hypersonic
weapons could challenge existing detection and defense
systems. For example, most terrestrial-based radars cannot
detect hypersonic weapons until late in the weapon's flight
due to line-of-sight limitations of radar detection. This
leaves minimal time for a defender to launch interceptors
that could neutralize an inbound weapon. Figure 1 depicts
the differences in terrestrial-based radar detection timelines
for ballistic missiles versus hypersonic weapons.
Figure I. Terrestrial-Based Detection of Ballistic
Missiles vs. Hypersonic Weapons
Source: CRS image based on an image in Gliding missiles that fly
faster than Mach 5 are coming, The Economist, April 6, 2019,
https://www.economist.com/science-and-technology/20I 9/04/06/
gliding-missiles-that-fly-faster-than-mach-5-are-coming.
U.S. defense officials have stated that both existing
terrestrial- and space-based sensor architectures are
insufficient to detect and track hypersonic weapons; former
Updated February 5, 2025
Under Secretary of Defense for Research and Engineering
Mike Griffin has noted that hypersonic targets are 10 to 20
times dimmer than what the U.S. normally tracks by
satellites in geostationary orbit.
The Proferated Warfighter Space
Archktecture
SDA developed the PWSA, formerly known as the National
Defense Space Architecture, to unify and integrate next
generation capabilities across [the Department of Defense
(DOD)] and industry. According to SDA, the PWSA aims
to be a single, coherent proliferated space architecture with
seven layers, which include the data tracking and transport
layers depicted in Figure 2 and discussed below. Other
layers include the custody layer to support the targeting of
mobile ground assets; the battle management layer to
provide space-based command and control; the navigation
layer to provide alternate positioning, navigation, and
timing for potential GPS-denied environments; the
deterrence layer to detect potentially hostile actions in deep
space; and the support layer to facilitate satellite operations
for the other PWSA layers. Once fully fielded, the PWSA is
to include 550 satellites and provide full global coverage.
Tracking Layer
SDA states that the tracking layer is to provide global
indications, warning, tracking, and targeting of advanced
missile threats, including hypersonic missile systems. As
part of this layer, SDA is developing an architecture of
Wide Field of View (WFOV) satellites, which are to
eventually provide global coverage. SDA requested $108.7
million for Tranche 0 tracking activities in FY2025 and
$1.5 billion for Tranche 1 tracking activities (also known as
Resilient Missile Warning Missile Tracking - Low Earth
Orbit).
Working in tandem with the SDA's tracking satellites will
be the Hypersonic and Ballistic Tracking Space Sensor
(HBTSS), previously known as the Space Sensor Layer,
which is being developed by MDA in collaboration with
SDA. HBTSS is to provide more sensitive, but more limited
(or Medium Field of View [MFOV]) coverage, compared to
WFOV. For this reason, WFOV is intended to provide
cueing data to HBTSS, which could then provide more
specific, target quality data to a ground-based interceptor.
MDA requested $76 million for HBTSS in FY2025.
The Space Force's Space Systems Command (SSC) is
developing a third set of tracking satellites called Resilient
Missile Warning Missile Tracking - Medium Earth Orbit
(MEO). According to SDA, the MEO satellites will add
low-latitude coverage and track custody and enhance
resilience in the nation's missile defense architecture. The
Space Force requested $846.3 million for Resilient Missile
Warning Missile Tracking - MEO in FY2025.](ViewImageLocal?handle=hein.crs/govesjr0001&div=1&collection=&method=preview&ext=.png&size=3)
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