The X-15 stands in a unique position in the annals of aviation history as one of the most ambitious projects to ever explore the envelope of aerial performance. Flying a total of 199 missions in only three aircraft, it broke every record in the 1960’s, with a top speed of 4,520 miles an hour (Mach 6.7) and an altitude record of 102, 100 feet – records for a manned aircraft that remain unbroken to this day.
Both aircraft and engine were developed in the mid-1950s but weren’t operational until 1959. Made from a number of heat-resistant alloys and the most advanced developments of its day, the original version used a set of two rockets similar to the Bell X-1 rocket, each with four ventura and delivering 16,000 pounds of thrust. In time, the XLR99 rocket became available, delivering a whopping 57,000 pounds of thrust.