Hitting a Bullet with a Bullet

Since the early 2000s, the U.S. Department of Defense's (DoD's) Missile Defense Agency (MDA) has developed, demonstrated and fielded the Ground-based Midcourse Defense (GMD), an anti-ballistic missile system designed to detect and intercept incoming ballistic warheads. Once launched, the trajectory of these unpowered warheads is largely defined by the Earth's gravity, making it possible for GMD to accurately track the threats and ultimately, "hit a bullet with a bullet."

"In the early 2010s, our government noted that near peer adversaries had started developing hypersonic weapons," said Tyler St. Onge, Director, Business Development, Northrop Grumman. "These new weapons featured maneuvering, booster-launched warheads traveling at speeds in excess of Mach 5. That makes them different and more dangerous than the ballistic missile threats that MDA has been preparing for all these years."

Hypersonic weapons come in two categories:

• Hypersonic cruise missiles, which are powered by high-performance, air-breathing engines known as scramjets
• Hypersonic boost-glide weapons, which comprise a maneuverable glide vehicle launched on a ballistic missile or rocket booster

Both types of weapons are notionally preprogrammed to fly to a specified target.

"When the enemy launches a booster stack, it's difficult to know if that warhead is going to follow a ballistic path or a hypersonic path," said Tyler.

With a traditional intercontinental ballistic missile, he explained, the warhead separates from its booster, then continues on a parabolic, gravity-driven trajectory to its target. By contrast, a hypersonic weapon separates from its booster after the peak of its trajectory, accelerates toward the Earth using gravity, then performs a pitch maneuver to begin a flatter trajectory called the glide phase.