The following is the June 24, 2024, Congressional Research Service report, Hypersonic Missile Defense: Issues for Congress.
From the report
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.
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.
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.”
Download the document here.
