Hypersonic Missiles Just Aren't Accurate

Photo credit: TASS - Getty Images
Photo credit: TASS - Getty Images

From Popular Mechanics

The U.S. is joining Russia and China in developing an entirely new type of weapon system: hypersonic weapons. Unlike ballistic missiles, which travel even faster, hypersonics are designed to remain within Earth’s atmosphere, traveling at speeds of up to Mach 20. But the Union of Concerned Scientists warns these weapons, described in the press as highly accurate, face serious technical challenges to actually be precise.

Hypersonic weapons are designed to achieve speeds of up to 15,000 miles an hour. While ballistic missiles launch their warheads on a ballistic profile that sees them briefly travel through space, hypersonic weapons remain in the atmosphere. The advantage: They fall between anti-ballistic missile defenses and traditional, anti-aircraft missile defenses. Hypersonics are—for now, anyway—difficult to defend against.

But atmospheric flight at high Mach numbers is problematic. The faster an object travels through air, the greater the amount of heat-generating friction. The SR-71 Blackbird strategic reconnaissance plane traveled at Mach 3, but due to air friction, it experienced skin temperatures of up to 600 degrees Fahrenheit. Ballistic missile warheads partially avoid this heat buildup by spending most of their flight time traveling through low-Earth orbit.

As the Union of Concerned Scientists points out, hypersonic weapons traveling at Mach 5-plus experience a whole new level of heat buildup. While a ballistic missile warhead might spend only seconds exposed to air friction, hypersonic weapons experience air friction throughout their entire flight. Chemical reactions with the surrounding air even create a plasma around the hypersonic weapon, which can interfere with the object’s ability to reference GPS or receive outside course correction commands.

That’s not all. Hypersonic travel is so brutal that an object traveling at such speeds slowly tears itself apart during flight as the speed magnifies heat, wind, and other environmental factors. This gradually alters a hypersonic weapon’s flight dynamics, making accuracy an increasingly difficult problem.

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