Air Force Maj. Gen. Joe Engle flew 16 research flights in the famed X-15 rocket plane in the 1960s; went on to fly the prototype space shuttle Enterprise during the Approach and Landing Tests and two orbital space shuttle missions. (NASA photo)
Joe Engle Recalls the Legacy of the X-15 Rocket Plane
On the eve of one of NASA's major space science milestones – the landing of its Mars Science Lab Curiosity rover on the red planet – retired Air Force test pilot and NASA astronaut Maj. Gen. Joe H. Engle recalled several earlier spaceflight milestones of which he was a part during a recent visit to NASA's Dryden Flight Research Center.
Milestones are something Gen. Engle understands as he frequently reached them during his experiences as an X-15 pilot, a pilot of the prototype space shuttle Enterprise during the 1977 Approach and Landing Tests at Edwards Air Force Base, Calif., and as commander of two space shuttle orbital missions.
During a colloquium presentation before NASA Dryden employees Aug. 2, Engle recalled his experiences during 16 flights in the rocket-powered X-15 as an Air Force pilot assigned to the joint NASA, Air Force, Navy and North American Aviation program. He flew in the X-15 to an altitude of 280,600 feet, at age 32 becoming the youngest pilot ever to qualify as an astronaut. Three of his X-15 flights exceeded the 50-mile altitude requirement for an astronaut rating.
"It was the ultimate flying machine," he said. "No airplane can live up to what the X-15 did."
A key contribution of the X-15 flight research program was to help engineers develop confidence that an unpowered spacecraft could glide to a safe landing on Earth. Also, the maneuvers to slow the X-15 were nearly identical to those of the space shuttle from Mach 6 to landing. Reaction controls, essentially small rockets used for directional control in space, also were proven on the X-15.
Engle was one of the beneficiaries of his X-15 work when he later piloted Enterprise and operational space shuttles.
The X-15 program's 199 flights during a nine-year period contributed to advances in aerospace technology such as materials, hypersonic aerodynamics, astronomy and spaceflight. Launched from beneath the wing of a modified B-52, the X-15 was the first piloted aircraft to exceed Mach 4, 5 and 6. Information from the X-15 program contributed to the development of the Mercury, Gemini, Apollo and the Space Shuttle programs.
"My first flight was a highlight. It was a relatively benign profile as far as speed and altitude, but benign in the X-15 was several orders of magnitude faster and higher than I'd ever been. Altitude flights were the ones I enjoyed. All X-15 flights were as exciting and busy as can be. There just wasn't time to sit and look around much." Engle said.
Engle was one of the beneficiaries of his X-15 work when he later piloted Enterprise and operational space shuttles, noting that the X-15 flights were a highlight of his career.
From June to October 1977 he was the commander of one of two crews that flew the Enterprise Approach and Landing Tests. Engle had another opportunity to validate the vehicle's landing characteristics in late 1981 during the second orbital shuttle mission, STS-2. The mission was cut short and he was required to manually fly the orbiter from orbit to a landing – the first and only pilot to accomplish that task.
He would later command a second orbital mission, STS-51I, on space shuttle Discovery that deployed three communication satellites and performed a successful on-orbit rendezvous and manual repair of a disabled communications satellite.
"STS-2 had a failure early on in its systems that required us to land after two days. We were totally busy and saturated with work and we didn't have time to look at or enjoy anything. In fact, we didn't have time to get any sleep. On 51I I there were times in the missions when you would be able to float over to a window and look out the window down on Earth. I think that was one of the most awesome sights," he said.
Following his colloquium presentation at NASA Dryden Aug. 2, Engle joined NASA pilot Jim Less during a pilot-proficiency flight in a NASA F/A-18 the following day, visited XCOR Aerospace at the Mojave Air and Spaceport in Mojave, Calif., and was honored at the Lancaster JetHawks baseball team's Aerospace Appreciation Night Aug. 4. The event was highlighted by a pre-game flyover of a NASA F/A-18 flown by Dryden pilot Troy Asher.
XCOR, developer of the Lynx suborbital reusable launch vehicle, is a flight provider in NASA's Flight Opportunities Program managed at Dryden. Engle enjoyed seeing an entry into the next generation of spacecraft.
"With a small company it's easier to engage the entire team in all the phases of development," he said. "Their jobs overlap and they help each other. It is a wonderful environment to ensure the most efficient and safest machine."
"The previous re-entry profiles I have flown are not that different from what they will be doing (with the Lynx)," said Engle. "The problems of re-entry are not that different and in some cases they are very similar."
Jay Levine, editor, The X-Press
NASA Dryden Flight Research Center