The X-43A was a small, unmanned test aircraft built by NASA with one goal: to achieve incredible speed. Part of the Hyper-X program, it aimed to prove that a scramjet could operate in real flight, not just inside a wind tunnel. Rather than launching from a runway, the X-43A was carried to high altitude by a B-52, then boosted by a Pegasus rocket to several thousand miles per hour. Only after the booster separated did its scramjet engine ignite. Unlike conventional rockets, the scramjet didn’t ca