Updated June 24, 2024

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 missilethreats. These elements include the tracking and transportlayers of the Proliferated Warfighter Space Architecture(PWSA) and various interceptor programs. As MDA andSDA 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 ofat least Mach 5, or roughly 1 mile per second. Unlike
ballistic missiles, hypersonic weapons do not follow aballistic trajectory and can maneuver en route to theirtarget. Russia reportedly fielded its first hypersonic
weapons in December 2019, while some experts believethat 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 R45811, Hypersonic Weapons: Background andIssues 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 existingterrestrial- and space-based sensor architectures areinsufficient 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 20times dimmer than what the U.S. normally tracks bysatellites in geostationary orbit.”

Proliferated Warfighter SpaceArchitecture
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 withseven layers,” which include the data tracking and transportlayers depicted inFigure 2 and discussed below. Other layers include thecustody layer to support the targeting of mobile groundassets; the battle management layer to provide space-basedcommand 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.” Aspart of this layer, SDA is developing an architecture ofWide Field of View (WFOV) satellites, which are toeventually 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 EarthOrbit).
Working in tandem with the SDA’s tracking satellites willbe the Hypersonic and Ballistic Tracking Space Sensor(HBTSS), previously known as the Space Sensor Layer,
which is being developed by MDA in collaboration withSDA and the U.S. Space Force. HBTSS is to provide moresensitive, 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 aground-based interceptor. MDA requested $76 million for
HBTSS in FY2025.
The Space Force’s Space Systems Command (SSC) isdeveloping 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

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Hypersonic Missile Defense: Issues for Congress

Space Force requested $846.3 million for Resilient Missile
Warning Missile Tracking - MEO in FY2025.
Section 1682 of the FY2020 NDAA (P.L. 116-92) tasks thedirector of the Missile Defense Agency to “develop ahypersonic and ballistic missile tracking space sensorpayload.” Section 1645 of the FY2021 NDAA (P.L. 116283) requires that integration of the sensor payload into theSDA’s broader space-based sensor architecture begin “assoon as technically feasible.” In 2022, the Space Forceestablished a Combined Program Office to coordinate
missile warning and tracking efforts, including SDA’sPWSA, MDA’s HBTSS, and SSC’s MEO satellites.
Figure 2. Selected Elements of the PWSA

In addition, Section 1664 of the FY2022 NDAA (P.L. 11781) grants the director of MDA “the authority to budget for,direct, and manage directed energy programs applicable”
for hypersonic missile defense, while Section 1662 of theFY2023 NDAA (P.L. 117-263) directs MDA to produce astrategy to use asymmetric capabilities (e.g., directedenergy, microwave systems) to defeat hypersonic missile
threats. The Defense Advanced Research Projects Agency(DARPA) is also working on a program called GlideBreaker, which is to “develop critical component
technology to support a lightweight vehicle designed for
precise engagement of hypersonic threats at very longrange.” DARPA requested $38 million for Glide Breaker inFY2025. Overall, MDA requested $182 million for
hypersonic defense in FY2025.

Issues for Congress

Source: CRS image; not to scale.

Transport Layer
SDA has stated that the PWSA’s transport layer, which isintended to connect the tracking layer to interceptors andother weapons systems on the ground, will “enhanceseveral mission areas including missile defense.” According
to DOD, SDA has awarded prototype agreements for
Tranches 1 and 2 of the transport layer. The transport layer
is to eventually consist of a constellation of approximately
300-500 satellites. SDA requested $1.4 billion for “the datatransport layer, sensor capabilities, and alternate position,navigation, and timing capabilities” in FY2025.

Interceptors
MDA has explored options for neutralizing hostile
hypersonic weapons, including interceptor missiles,
hypervelocity projectiles, directed energy weapons, andelectronic attack systems. In January 2020, MDA issued adraft request for prototype proposals for a HypersonicDefense Regional Glide Phase Weapons Systeminterceptor. This program was intended to “reduce
interceptor key technology and integration risks.” In April
2021, MDA then shifted to the Glide Phase Interceptor(GPI), which is to be integrated with the Aegis Weapon
System. Although GPI was to notionally provide a
hypersonic missile defense capability in FY2034, Section
1666 of the FY2024 NDAA (P.L. 118-31) directs DOD toachieve initial operational capability for the program by
December 31, 2029, and full operational capability byDecember 31, 2032. Lockheed Martin, Northrop Grumman,
and Raytheon Missiles and Defense have been awarded
contracts for the “accelerated concept design” phase of theGPI. In May 2024, DOD signed a formal agreement withJapan to cooperatively develop GPI.

Some analysts have suggested that space-based sensor
layers—integrated with tracking and targeting systems todirect high-performance interceptors or directed energy
weapons—could theoretically present viable options for
defending against hypersonic weapons. The 2019 Missile
Defense Review notes that “such sensors take advantage ofthe large area viewable from space for improved tracking
and potentially targeting of advanced threats, including
hypersonic [weapons].” Other analysts have questioned theaffordability, technical feasibility, and/or utility ofhypersonic weapons defense. In addition, some analysts
have argued that the United States’ current command andcontrol architecture would be incapable of “processing data
quickly enough to respond to and neutralize an incominghypersonic threat.”
Some analysts have also questioned the current division oflabor and level of coordination between the SDA and MDA
on hypersonic missile defense. SDA director Tournear has
previously responded to criticisms of potential redundancies
between the two agencies, stating that both report to theUnder Secretary of Defense for Research and Engineering.
Since October 2022, SDA director Tournear instead reports
to the Assistant Secretary of the Air Force for Acquisition
and Integration. Also in 2022, the Space Force created thecombined program office overseeing missile warning andtracking efforts to address concerns about integration.
Congress may monitor the implications of this reporting
structure and new combined program office for efficiency
and efficacy.

Potential Questions for Congress• Is an acceleration of research on hypersonic missile
defense options both necessary and technologicallyfeasible? Does the technological maturity of hypersonicmissile defense options warrant current funding levels?
• How are SDA, MDA, and SSC collaborating on various
elements of hypersonic missile defense? Are theircurrent roles increasing or decreasing costs and thespeed and efficiency of technology development?
• Does DOD have the enabling capabilities, such asadequate command and control architectures, needed toexecute hypersonic missile defense?
Jennifer DiMascio, Analyst in U.S. Defense Policy
Kelley M. Sayler, Analyst in Advanced Technology andGlobal Security

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Disclaimer
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