Prior to the United States entrance into the manned space program with the launch of Alan Shepard, Jr. in a suborbital mission on May 5, 1961, our country made a very ambitious effort to place man at the fringes of outer space with a more conventional airplane approach. It was known as Project X-15.
In 1952, the National Advisory Committee for Aeronautics (NACA) wanted to begin testing manned rocket powered airplanes at speeds of Mach 5 or greater. Mach 5 is equal to five times the speed of sound or also known as hypersonic speed! NACA later became the National Aeronautics and Space Administration better known as NASA.
Two years later, NACA, the navy, and the air force began a project best known as the X-15. Its goal was to pilot the X-15 rocket plane at speeds up to 1.25 miles per second, and reach an altitude of at least 47.35 miles above the Earth’s surface.
The X-15 was 50 feet long, and weighed 30,000 pounds with propellant, and about 15,000 pounds without. It also had a relatively small wing span of 22 feet.
The test flights would be at six dry lakebeds within 300 miles of Edwards Air Force Base in California. There would be a total of 199 test flights. The first one commenced on June 8, 1959. The last one took place on October 24, 1968. All flights would end at Edwards, California.
The flights of the X-15 would consist of the rocket plane being mated to the bottom of a wing of a B-52 Bomber. Then when the bomber reached a designated altitude of about 45,000 feet, the X-15 would be dropped. After falling a safe distance, the pilot of the X-15 would ignite its engine, and the test flight would begin. At the conclusion of the flight, the X-15 would make an unpowered landing on the dry lakebed in Edwards, California.
There were 12 test pilots of the X-15. Most notable were Neil Armstrong who later became the first man to set foot on the lunar surface on Apollo 11 on July 20, 1969; and Joseph Engle, a space shuttle astronaut.
On August 22, 1963, Pilot Joseph Walker, on flight number 91, took the X-15 to a new world record altitude of 354,200 feet or about 67.083 miles. He also hit a top speed of 3,794 miles per hour or about 1.054 miles per second.
According to simulations, however, it was thought that the X-15 could reach an altitude of 450,000 feet or about 85.23 miles, but it was decided that under these conditions extremely dangerous situations might prevail.
On test flight number 188, Pilot William “Pete” Knight reached the fastest speed ever in the X-15. He hit 4,520 miles per hour or about 1.256 miles per second. He also reached an altitude of 102,100 feet.
— Kansas Skies, Bob Everoski