Maj. Gen. Joe Engle flew 16 research flights in the X-15 rocket plane in the 1960s and went on to fly the prototype space shuttle Enterprise during the Approach and Landing Tests and two orbital space shuttle missions. (NASA Photo) › View Larger Image
Engle and X-15 Pilots Verified, Validated the Methods to Reach the Space Age
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 his involvement in several earlier spaceflight milestones during a recent Dryden visit.
Milestones are something 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, and as commander of two space shuttle missions.
Engle attended a number of events in the Antelope Valley including a tour and colloquium at Dryden, a visit to XCOR Aerospace at the Mojave Air and Space Port and as an honoree at the Lancaster JetHawk's baseball team Aerospace Appreciation Night. Dryden pilot Troy Asher and Tom Jones, Dryden Supersonics project manager, provided another highlight of the event with two pre-game flyovers in a NASA F/A-18.
Engle had 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 the X-15 to an altitude of 280,600 feet and became the youngest pilot to qualify as an astronaut at age 32. Three of his X-15 flights exceeded the 50-mile altitude requirement for an astronaut rating.
"It was the ultimate flying machine. No airplane can live up to what the X-15 did," he said.
A key contribution of the X-15 was developing confidence that an unpowered spacecraft could glide to a safe landing. 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.
Engle said he was impressed with the cooperation among partners during the X-15 program and that the X-15 flights were a highlight of his career.
"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. 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.
From June to October 1977 he was the commander of one of two crews that flew the Enterprise Approach and Landing Tests. The Enterprise was released from the back of a special modified NASA 747 Shuttle Carrier Aircraft and had a two-and-a-half minute glide test from 20,000 feet to landing.
Engle had another opportunity to validate the vehicle's landing characteristics in late 1981 during the second orbital space 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-51-I, 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 51-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.
At XCOR, which along with the Mojave Air and Space Port sponsored the Aerospace Appreciation Night, he toured the facilities and sat in a mock up of XCOR's Lynx suborbital, reusable, launch vehicle. The Lynx is intended to be a highly reliable and safe mode of transportation to space. XCOR is a flight provider in NASA's Flight Opportunities program managed at Dryden.
The Mach 4, two-seat, Lynx launch vehicle looks similar to a high performance futuristic fighter jet and will take off from the runway like a conventional aircraft, but using four liquid oxygen and kerosene engines. The fully reusable rocket engines will propel the Lynx to the edge of space, where it will carry participants and/or scientific upper atmosphere and microgravity experiments. The company is ambitious and is planning for its flight tests to begin at the Mojave Air and Space Port next year and then produce additional Lynx vehicles for operations from other locations around the country - and the world.
Engle had suggestions and answered questions from company representatives.
Dan DeLong, XCOR vice president and chief engineer, agreed that talking to Engle was productive.
"Our hypotheses and estimates were corroborated. Nothing was surprising, but it feels good that there are no blind alleys. He also gave us a heads up on what to look for during the flight test program," DeLong said.
Engle also enjoyed seeing an entry into the next generation of spacecraft.
"I enjoyed seeing their approach. With a small company it's easier to engage the entire team in all the phases of development. Their jobs overlap and they help each other. It is a wonderful environment to ensure the most efficient and safest machine. I think they are doing some innovative and creative things with that vehicle. Of course, I enjoyed sitting in the [Lynx] cockpit and imagining what might be of value to look back to from previous programs like the X-15. The previous re-entry profiles I have flown are not that different from what they will be doing. The problems of re-entry are not that different and in some cases they are very similar," Engle said.
Engle's experiences bridge the X-15 and shuttle programs. Research from the X-15 and other experimental vehicles from Edwards and Dryden may help provide clues for solving some of the current and future mysteries uncovered by new vehicles that will expand people's views of Earth and beyond.
By Jay Levine