How the SR-71 Navigated at Mach 3 Without GPS

Flying at 2,200 mph at the edge of space, the SR-71 Blackbird had a massive problem: GPS didn't exist yet. So how did it know exactly where it was?

Enter the Astro-Inertial Navigation System (ANS), affectionately known as the "R2-D2" of the Blackbird. Behind the cockpit sat a highly sensitive automated telescope. Because the atmosphere at 80,000 feet is incredibly thin, the sky is black enough to see stars in broad daylight.

Using a specialized blue filter, the telescope tracked three major stars simultaneously. By mathematically comparing those stars to a built-in celestial database, it could pinpoint the jet's location instantly. This incredible system guided the Mach 3 spy plane within 300 feet of its target over thousands of miles.

It was the original, unhackable GPS, conquering the world using ancient physics.