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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 National Defense Space Architecture (NDSA)
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 China is expected to
field its first in 2020. The United States is not expected to
field hypersonic weapons before 2023. (For an overview of
hypersonic weapons programs in Russia, China, and the
United States, see CRS Report R45811, Hypersonic
Weapons: Background and Issues for 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/2019/04/06/
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
Updated January 13, 2021
insufficient to detect and track hypersonic weapons; former
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.
National Defense Space Architecture
SDA developed the National Defense Space Architecture to
unify and integrate next generation capabilities across [the
Department of Defense (DOD)] and industry. The NDSA
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 NDSA
layers. Once fully fielded, as is planned by 2025, the NDSA
would encompass 550 satellites and provide full global
coverage.
Tracking Layer
SDA began the process of building the tracking layer-
which is to provide global indications, warning, tracking,
and targeting of advanced missile threats, including
hypersonic missile systems-through the Tracking
Phenomenology Experiment (TPE). The TPE objective is to
develop a missile sensor algorithm capable of tracking
hypersonic weapons. In parallel, SDA plans to develop
eight satellites as part of a Wide Field of View (WFOV)
architecture. SDA then intends to expand this architecture
to provide global coverage. SDA requested $72.4 million
for TPE and related programs in FY2021.
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 and funded by 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.
By 2023 SDA plans to expand the tracking layer to include
70 WFOV and MFOV satellites, which, according to SDA
director Dr. Derek Tournear, will give us enough coverage
in low-Earth orbit so that we can have essentially regional
persistence.
:tps://crsreports.congress.go](ViewImageLocal?handle=hein.crs/govebti0001&div=1&collection=&method=preview&ext=.png&size=3)
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