Tag Archives: North American X-15

These Images Document The Heat Damage To The X-15A Hypersonic Aircraft After Its Record Breaking Mach 6.7 Flight

Aerodynamic heating at Mach 6.72 (4,534 mph) almost melted the airframe.

On Oct. 3 1967 the North American X-15A-2 serial number 56-6671 hypersonic rocket-powered research aircraft achieved a maximum Mach 6.72 piloted by Major Pete Knight.

Operated by the United States Air Force and the National Aeronautics and Space Administration as part of the X-plane series of experimental aircraft in the 1960s, the X-15 was a missile-shaped vehicle built in 3 examples and powered by the XLR-99 rocket engine capable of 57,000 lb of thrust.

The aircraft featured an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage.

The X-15 was brought to the launch altitude of 45,000 feet by a NASA NB-52B “mothership” then air dropped to that the rocket plane would have enough fuel to reach its high speed and altitude test points. Depending on the mission, the rocket engine provided thrust for the first 80 to 120 sec of flight. The remainder of the normal 10 to 11 min. flight was powerless and ended with a 200-mph glide landing.

An interesting account of Oct. 3, 1967 record flight was written by Flight Engineer Johnny G. Armstrong on his interesting website. Here’s an excerpt:

As the X-15 was falling from the B-52 he lit the engine and locked on to 12 degrees angle of attack. He was pushed back into his seat with 1.5 g’s longitudinal acceleration. The X-15 rounded the corner and started its climb.

During the rotation as normal acceleration built up to 2 g’s Pete had to hold in considerable right deflection of the side arm controller to keep the X-15 from rolling to the left due to the heavier LOX in the left external tank. When the aircraft reached the planned pitch angle of 35 degrees his scan pattern switched from the angle of attack gauge to the attitude direction indicator and a vernier index that was set to the precise climb angle.

The climb continued as the fuel was consumed from the external tanks, then at about 60 seconds he reached the tank jettison conditions of about Mach 2 and 70,000 feet. He pushed over to low angle of attack and ejected the tanks. He was now on his way and would not be making an emergency landing at Mud Lake.

“We shut down at 6500 (fps), and I took careful note to see what the final got to. It went to 6600 maximum on the indicator. As I told Johnny before, the longest time period is going to be from zero h dot getting down to 100 to 200 feet per second starting down hill after shutdown.”

Final post flight data recorded an official max Mach number of 6.72 equivalent to a speed of 4534 miles per hour.

From there down Pete was very busy with the planned data maneuvers and managing the energy of the gliding X-15. He approached Edwards higher on energy than planned and had to keep the speed brakes out to decelerate.

On final approach he pushed the dummy ramjet eject button and landed on Rogers lakebed runway 18. He indicated he did not feel anything when he activated the ramjet eject and the ground crew reported they did not see it. Pete said that he knew something was not right when the recovery crew did not come to the cockpit area to help him out of the cockpit, but went directly to the back of the airplane.

Finally when he did get out and saw the damage to the tail of the X-15 he understood. There were large holes in the skin of the sides of the fin with evidence of melting and skin rollback. Now we are talking Inconel-X steel that melts at 2200 degrees F. Later analysis would show that the shock wave from the leading edge of the ramjet’s spike nose had intersected the fin and caused the aerodynamic heating to increase seven times higher than normal. So now maybe we knew why the ramjet was not there.

X-15-2 after the record flight (#189) on Oct. 3, 1967. The aircraft achieved the record without any NASA marking. The aircraft was painted in white that covered an ablative material that protected the fuselage. The Martin Marietta’s MA-25S ablative would erode slowly shedding the heat of aerodynamic friction. Pink in color, the ablative the MA-25S ablative reacted when exposed to liquid oxygen burned by its XLR-99 rocket engine. For this reason it was sealed under white paint. More details here.

The following 48-sec footage shows the extent of the damages to the X-15-2 aircraft. Noteworthy, the ramjet detached from the aircraft at over 90,000 feet and crashed into the desert over 100 miles from Edwards Air Force Base.

Here are some details.

Wing leading edge burns.

Reaction Control System thrusters.

Two holes appeared on the fuselage along with burns.

The nose of the aircraft shows ablative damages as well as a result of frictional heating.

The X-15A-2 never flew again after the record flight. It is currently preserved and displayed at the United States Air Force Museum, Wright-Patterson AFB, Ohio.

The top image shows the damage to one of the two ventral UHF antennas of the X-15.

That Time An X-15 Rocket Plane Entered Hypersonic Spin At Mach 5 And Broke Apart Killing USAF Test Pilot.

U.S. Air Force test pilot Maj. Michael J. Adams was killed during X-15 Flight 191 on Nov. 15, 1967.

The North American X-15 was a hypersonic rocket-powered aircraft 50 ft long with a wingspan of 22 ft. operated by the United States Air Force and the National Aeronautics and Space Administration as part of the X-plane series of experimental aircraft in the 1960s.

It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage. It was powered by the XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., pilot-controlled and  capable of developing 57,000 lb of thrust.

The aircraft was brought to the launch altitude of 45,000 feet by a NASA B-52 “mothership” then air dropped to that the rocket plane would have enough fuel to reach its high speed and altitude test points. Depending on the mission, the rocket engine provided thrust for the first 80 to 120 sec of flight. The remainder of the normal 10 to 11 min. flight was powerless and ended with a 200-mph glide landing.

The X-15 was air dropped by a NASA B-52 “mothership”

The X-15 was capable of climbing to the edge of space at an altitude in excess of 300,000 feet at speed of more than 4,500 miles per hour (+7,270 km/h). Actually, the target altitude for X-15 flights was set at 360,000 feet because there were concerns about the reentry from 400,000 feet, that was the maximum altitude the rocket plane was theoretically able to reach.

Two types of flight profiles were used during test flights depending on the purposes of the mission: a high-altitude flight plan that called for the pilot to maintain a steep rate of climb, or a speed profile that called for the pilot to push over and maintain a level altitude.

For flight in the dense air of the usable atmosphere, the X-15 used conventional aerodynamic controls but to maneuver in the thin air outside of the appreciable Earth’s atmosphere, where flight control surfaces were useless, the X-15 used a reaction control system (RCS) made of hydrogen peroxide thrust rockets. Those located on the nose of the aircraft provided pitch and yaw control; those on the wings provided roll control. A similar system was used on the Space Shuttle Orbiter, decades later: indeed, experience and data gathered from the X-15 program contributed to the development of the Mercury, Gemini, Apollo and Space Shuttle manned spaceflight programs.

Cutaway drawing of the North American X-15.
1/20/62

Needless to say, handling the rocket-powered aircraft at the edge of space was particularly challenging.

 

X-15-3 (56-6672) made 65 flights during the program. It reached attaining a top speed of Mach 5.65 and a maximum altitude of 354,200 feet.

Official records say that only 10 of the 12 X-15 pilots flew Ship #3; eight of them earned their astronaut wings during the program (in fact, U.S. Air Force pilots who flew the X-15 to altitudes above 50 miles all received Astronaut Wings): Robert White, Joseph Walker, Robert Rushworth, John “Jack” McKay, Joseph Engle, William “Pete” Knight, William Dana, and Michael Adams all earned their astronaut wings in Ship #3.

Out of three X-15s built by North American for the program, Ship #3 is the only X-15 that has not survived, as it was lost on Nov. 15, 1967.

X-15-1, serial number 56-6670, is now located at the National Air and Space museum, Washington DC. North American X-15A-2, serial number 56-6671, is at the United States Air Force Museum, Wright-Patterson AFB, Ohio.

Here’s the story of that last mission:

On 15 November 1967, Ship #3 was launched over Delamar Lake, Nevada with Maj. Michael J. Adams at the controls. The vehicle soon reached a speed of Mach 5.2, and a peak altitude of 266,000 feet.

During the climb, an electrical disturbance degraded the aircraft’s controllability. Ship #3 began a slow drift in heading, which soon became a spin. Adams radioed that the X-15 “seems squirrelly” and then said “I’m in a spin.”

Through some combination of pilot technique and basic aerodynamic stability, Adams recovered from the spin and entered an inverted Mach 4.7 dive. As the X-15 plummeted into the increasingly thicker atmosphere, the Honeywell adaptive flight control system caused the vehicle to begin oscillating. As the pitching motion increased, aerodynamic forces finally broke the aircraft into several major pieces.

Adams was killed when the forward fuselage impacted the desert. This was the only fatal accident during the entire X-15 program.  The canopy from Ship #3, recovered during the original search in 1967, is displayed at the San Diego Aerospace Museum, San Diego, California.

Parts of the crashed X-15-3, serial number 56-6672, recovered in 1992 by Peter Merlin and Tony Moore (The X-Hunters) are on display at the Air Force Flight Test Center Museum at Edwards.

According to NASA, the X-15s made a total of 199 flights over a period of nearly 10 years (from June 1959 to Oct. 1968) and set world’s unofficial speed and altitude records of 4,520 miles per hour or Mach 6.7 (set by Ship #2) and 354,200 feet (set by Ship #3).

Image credit: NASA

Watch C-17, A-10 and HC-130J Aircraft Operate From Delamar Dry Lake Bed (the original emergency landing site for the X-15)

U.S. Air Force landed and took off from the Delamar Dry Lake Bed, the emergency landing site for the X-15.

C-17 Globemaster III airlifters from 57th Weapons Squadron, A-10 Thunderbolt IIs from the 66th Weapons Squadron, HC-130J from the 34th Weapons Squadron as well as HH-60Gs belonging to the 66th Rescue Squadron took part in USAF Weapons School squadrons composite mission application and combat search and rescue operations at the Delamar dry lake bed on the NTTR (Nevada Test and Training Range).

Referred to as “Texas Lake” dry lake bed because of its resemblance to the state of Texas from the air, Delamar Lake landing strip was established in 1943 and, in the 1960s it was designated emergency landing sites for the North American X-15, a rocket-powered, missile-shaped manned aircraft operated by the U.S. Air Force and NASA capable to reach the edge of space at an altitude between 100,000 and 300,000 feet at speed exceeding 4,500 MPH (+7,270 km/h) .

In fact, the dry lake bed was located underneath the Delamar Dry Lake Drop Zone where the X-15s brought to the launch altitude of 45,000 feet under the wing of a B-52 bomber, were dropped at a speed of Mach 0.8.

The Delamar Lake Landing Strip consists of a 15,000 ft long runway; still, considered the lack of obstacles, aircraft can land in any direction.

Along with making “unprepared landing strip operations” training possible, dry lakes can be particularly useful also in case of emergency: the huge lakebed can minimize the damage to a plane forced to land there. Here is what happened when a B-1 Lancer performed a crash landing on the Rogers Dry Lake at Edwards Air Force Base in 1989. Here you can find a U.S. Air Force C-5 Galaxy airlifter making a successful emergency landing once again at Rogers Dry Lake in 2001.

 

The story of the pilot who flew the North American X-15 experimental rocket aircraft at the edge of outer space

Designed to study the problems of hypersonic flight, the North American X-15, carrying only 90 seconds worth of fuel could reach Mach 5+ and altitudes between 100K and 300K feet.

The North American X-15 was a rocket-powered, missile-shaped manned aircraft operated by the U.S. Air Force and NASA as part of the X-plane series of experimental aircraft.

Brought to the launch altitude of 45,000 feet under the wing of a B-52 bomber and dropped at a speed of Mach 0.8, the X-15 was capable to reach the edge of space at an altitude between 100,000 and 300,000 feet at speed exceeding 4,500 MPH (+7,270 km/h) .

The U.S. Air Force pilots who flew the X-15 to altitudes above 50 miles all received Astronaut Wings, but  NASA decided not to give the same award to the civilian pilots who made the same achievement, a decision that caused controversy within the aerospace community as explained by John Anderson and Richard Passman in their book X-15 The World’s Fastest Rocket Plane and the Pilots who Ushered in the Space Age.

Among those pilots there was Joe Walker, who flew the maximum altitude flight in the X-15 on Aug. 22, 1963.

The flight path of that mission was carefully planned with climb angles and fuel cut off calculated to reach the goal. In fact as told by Anderson and Passman, the engine thrust could vary from 57,000 pounds to 60,000 pounds, and a difference of 1,500 pounds would result in a 7,500 feet altitude change. One second in fuel cut off time would result in a 4,000 feet altitude change, while if the climb angle was off by one degree, a 7,500 feet change in altitude would occur.

Moreover NASA planned maximum altitude for X-15 flights was at 360,000 feet safety reasons: even if the aircraft could go well above 400,000 feet there was concern about the reentry from that altitude.

Since aircraft experienced APU problems the flight was delayed for two weeks, but on Aug. 22 the launch went well and Walker could closely follow the flight plan. The propellants were depleted at 176,000 feet at a speed of 5,600 feet per second, but two minutes after the burnout the X-15 was still soaring upward on a ballistic trajectory to 354,200 feet, 67 miles high.

Then, after reaching the peak altitude, Walker began descending and headed to Edwards Air Force Base, where he landed after a flight of 11 minutes and 8 seconds.

Even if Walker flew higher than the 50 miles required by the Astronaut Wings at that time, he didn’t receive the award.

In the 1960s the U.S. Air Force set a limit of space at 50 miles (80 km) but according to FAI (the World Air Sports Federation, the world governing body for air sports, aeronautics and astronautics world records) the limit of the outer space is at 100 kilometers (62.1 mi). Nevertheless, Walker exceeded both limits and, even though he didn’t receive the Astronaut Badge,  he was the first American civilian to make any spaceflightand the second civilian overall, and the first human to make multiple spaceflights (the one on Aug. 22 and the preceding one, on Jul. 19, when he reached the altitude of 65.8 miles (105.9 km).

NB-52A & X-15

After his involvement on the X-15 program, Walker continued its flying activity as an experimental pilot. On Jun. 8, 1966, he was at the controls of an F-104 flying in formation with another North American product, the XB-70, for a General Electric photo shoot of a family of airplanes powered by GE engines. Flying too close to the XB-70, Walker’s F-104 was caught in the trailing vortex of the large airplane and flipped onto the top of the bomber.

Walker perished in the subsequent fireball depicted by some famous pictures.

As recalled by Anderson and Passman, on Aug. 23 2005, NASA reversed his policy and awarded with Astronaut Wings the three civilian pilots who flew the X-15 above 50 miles: William Dana (the only one still alive at the time of the ceremony), Jeff McKay and Joe Walker.

Finally Walker achieved official astronaut rating, 42 years after his record and 39 years after he died.

Image credit: NASA and U.S. Air Force