China’s test flight of a long-range hypersonic glide vehicle late last year was described in the media as close to a “Sputnik moment” in the race to develop new ultrafast maneuvering weapons. But even as senior U.S. military officials publicly fretted about missiles that are, for the moment at least, effectively invincible, the Pentagon was quietly making strides on an entirely novel way to help shoot down these weapons.
Late last December the U.S. Department of Defense’s Missile Defense Agency (MDA) gave the green light to a pair of contractors—L3Harris Technologies and Northrop Grumman—to pivot from design to prototype fabrication of a Hypersonic and Ballistic Tracking Space Sensor (HBTSS) system. This technology is intended to solve one of the Pentagon’s most vexing technical challenges: how to detect and track the hypersonic glide vehicles that exploit blind spots in today’s radar networks.
Both Russia and China have fielded hypersonic glide vehicles, in 2019 and 2020 respectively, but the U.S. is not expected to deploy a comparable offensive weapon until 2023. In contrast to ballistic missile payload trajectories, hypersonic glide vehicles can maneuver on the way to a target. This makes it extremely difficult to track them. These weapons start their journey when a large rocket boosts them to an altitude near the edge of space and releases them. Then the glide vehicles divert to a flatter trajectory—either exiting the atmosphere or staying just within it—and sail on unpowered. They use aerodynamic lift to skip across the atmosphere to their targets at hypersonic speeds. This near-space trajectory and the ability to shift course let hypersonic glide vehicles evade the combination of space and terrestrial sensors used to track ballistic missiles. The Pentagon can detect the launch—but the hypersonic glide vehicle then slips out of view until late in the weapon’s flight because of ground radar’s line-of-sight limitations. As a result, defensive systems have little, if any, time left to halt an incoming weapon.
HBTSS is intended to solve this problem by continuously tracking long-range missiles from launch to impact. It will also have the ability to hand off critical information to ships, aircraft and ground forces, enabling them to fire their own missiles at incoming threats. The detection system relies on a new network of orbiting sensors, a critical part of a dense and multilayered constellation of satellites the Pentagon has already begun placing in low-earth orbit. Experimental and prototype payloads were sent into orbit last June, and initial operational payloads are slated for launch in 2022 and 2023. These sensors detect heat signatures to identify missile launches and will give the U.S. military the ability to track targets, described as cradle-to-grave target custody.
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