https://crsreports.congress.gov
Updated October 3, 2022
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 some experts believe
that China fielded hypersonic weapons as early as 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 1. 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
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, the NDSA is to include 550
satellites and provide full global coverage.
Tracking Layer
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 $81.3 million for Tranche
0 tracking activities in FY2023 and $499.8 million 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 and the U.S. Space Force. 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.” MDA
requested $89.2 million for HBTSS in FY2023.
Section 1682 of the FY2020 NDAA (P.L. 116-92) tasks the
director of the Missile Defense Agency to “develop a
hypersonic and ballistic missile tracking space sensor
