Tag Archives: National Aeronautics and Space Administration

11 April 1975

A formation of NASA's five Lockheed F-104 Starfighters, 11 April 1975. (NASA/Bob Rhine)
A formation of NASA’s five Lockheed F-104 Starfighters, 11 April 1975. (NASA/Bob Rhine)

11 April 1975: “The only time the five ship fleet of NASA Dryden’s F-104 Starfighters was ever airborne at the same time. Pilots were: F-104N #811-Bill Dana; F-104N #812-Tom McMurtry; F-104A #818-Einar Enevoldson; F-104A #820-Gary Krier; and F-104B #819-Fitz Fulton and Ray Young. Photo taken from T-38 #821 flown by Don Mallick.”

Wernher von Braun: 23 March 1912–16 June 1977

Wernher von Braun, Director, Marshall Space Flight Center (NASA)
Dr. Wernher von Braun, Director, Marshall Space Flight Center, 1 May 1964. (NASA)

23 March 1912: Wernher Magnus Maximilian Freiherr von Braun, rocket engineer, was born at Wyrzysk, Province of Posen, in the German Empire, in what is now Poland. He was the second of three children of Magnus Alexander Maximillian von Braun, head of the Posen provincial government, and Emmy Melitta Cécile von Quistorp.

Wernher von Braun, at center, with his brothers, Magnus (left) and Sigismund (right). (NASA)

Wernher von Braun originally wanted to be a musician and composer, having learned to play the cello and piano at an early age. After reading a speculative book on space flight, though, his interests shifted.

In 1929, the 17-year-old von Braun joined Verein für Raumschiffahrt, the German rocketry association. He worked with Hermann Oberth in testing liquid-fueled rockets, based on successful rockets designed by Dr. Robert H. Goddard in the United States.

Rudolf Nebel (left) and Wernher von Braun with small liquid-fueled rockets, circa 1930. (Unattributed)
Rudolf Nebel (left) and Wernher von Braun with small liquid-fueled rockets, circa 1930. (Unattributed)

Von Braun graduated from Technische Hochschule Berlin in 1932, with a degree in mechanical engineering (Diplom-Ingenieur). Two years later, he received a doctorate in physics (Dr. phil.) at Friederich-Wilhelm University of Berlin. He also studied at ETH Zürich.

In Germany before World War II, Dr.-Ing. von Braun worked on the problems of liquid-fueled rockets and developed the Aggregat series of rockets, including the A4, which would become known as the V-2 (Vergeltungswaffe 2) military rocket. The German Army’s Ordnance Department gave von Braun a grant to further study liquid-fueled rockets, which he pursued at an artillery range at Kummersdorf, just south of Berlin

As rocketry work expanded, the tests were eventually moved to the Peenemünde Military Test Site on the island of Usedom on the Baltic coast, where von Braun was technical director under Colonel Dr. Ing. Walter R. Dornberger.

Wernher von Braun with a number of German officers at Peenemunde, March 1941. (Left to right) Oberst Dr. Walter Dornberger, General Friederich Olbricht, Major Heinz Brandt, von Braun; others not identified. (Bundesarchiv, Bild 146-1978-Anh.024-03/CC-BY-SA 3.0)
Prof. Dr.-Ing. Wernher von Braun with a number of German officers at Peenemünde, March 1941. (Left to right) Colonel Dr. Ing. Walter Dornberger (partially out of frame), General der Infanterie Friederich Olbricht*, Major Heinz Brandt, Prof. Dr. von Braun; others not identified. (Bundesarchiv, Bild 146-1978-Anh.024-03/CC-BY-SA 3.0) [*General Olbricht developed Operation Valkyrie, the plot to assassinate Hitler and overthrow the Nazi regime.]
Aggregat 4 prototype (probably V-3) ready for launch at Prüfstand VII, August 1942. (Bundesarchiv)

The first successful launch of the A4 took place 3 October 1942. By the end of World War II, Nazi Germany had launched more than 3,200 V-2 rockets against Belgium, England, France and The Netherlands.

V-2 rocket launch at Peenemünde, on the island of Usedom in the Baltic Sea. (Bundesarchiv)

As World War II in Europe came to a close and the collapse of Nazi Germany was imminent, von Braun had to choose between being captured by the Soviet Red Army or by the Allies. He surrendered to the 324th Infantry Regiment, 44th Infantry Division, United States Army in the Bavarian Alps, 2 May 1945.

Dornberger, Herber Axter, von Braun and Hans Lindenberg, 3 May 1945. (U.S. Army)
Major-General Dr. Ing. Walter R. Dornberger; Lieutenant-Colonel Herbert Axster, Dornberger’s chief of staff; Prof. Dr.-Ing. Wernher von Braun (with left arm in cast); and Hans Lindenberg, chief propulsion engineer; at Reutte, Austria, 3 May 1945. (Technician 5th Class Louis Weintraub, U.S. Army)

Under Operation Paperclip, Wernher von Braun and many other scientists, engineers and technicians were brought to the United States to work with the U.S. Army’s ballistic missile program at Fort Bliss, Texas, White Sands Proving Grounds, New Mexico, and the Redstone Arsenal, Huntsville, Alabama.

A-4 Number 3 is prepared for launch at White Sands Proving Grounds, New Mexico, 10 May 1946. With a burn time of 59 seconds, the rocket reached an altitude of 70.9 miles (114.1 kilometers) and traveled 31 miles (49.9 kilometers) down range. (The Space Race – Rockets)

Sufficient parts and materiel had been transferred from Germany to construct more than one hundred V-2 rockets for testing at White Sands. Over a five year period, there were 67 successful launches, but it is considered that as much knowledge was gained from failures as successes.

Dr. von Braun with V-2 rocket compnents in Texas, circa 1945. (Unattributed)
Dr. von Braun with V-2 rocket components at White Sands Proving Grounds, New Mexico, 1 November 1946. (Thomas D. McAvoy)

In 1950, von Braun and his team were sent to Redstone Arsenal, Huntsville, Alabama, where they worked on more advanced rockets. The first production rocket was the short-range ballistic missile, the SSM-A-14 Redstone, which was later designated PGM-11. This rocket was capable of carrying a 3.8 megaton W39 warhead approximately 200 miles (322 kilometers) The first Redstone was launched at Cape Canaveral Air Force Station, 20 August 1953.

Compare the military Redstone SSM-A-14 in this photograph to the Mercury-Redstone rocket in the photograph below. This rocket, CC-1002, was the first Block 1 tactical rocket. (MSFC-580069)

Modified Redstone MRLV rockets were used to launch the first Mercury spacecraft with NASA astronauts Alan Shepherd and Gus Grissom. Von Braun later worked on the U.S. Army’s Jupiter-A intermediate range ballistic missile. A modified Jupiter-C was used to launch Explorer 1, the United States’ first satellite.

Explorer 1 launch, Launch Complex 26A, Cape Canaveral Air Force Station, 1 February 1958, 03:48:00 UTC. (NASA)
Explorer VII/Juno II launch, from LC-5, Cape Canaveral Air Force Station, 13 October 1959. (NASA MSFC-5900711)
Mercury-Redstone 4 (Liberty Bell 7) launch at Pad 5, Cape Canaveral Air Force Station, 12 20 36 UTC, 21 July 1961. (NASA)

Wernher von Braun traveled to Germany in 1947 to marry his cousin, Maria Irmengard Emmy Luise Gisela von Quistorp, and then returned to the United States. He became a naturalized citizen of the United States of America in 1955.

The von Braun family, circa 1955 (U.S. Army)
Prof. Dr. von Braun with his family, circa 1957. Left to right, Maria Luise von Braun, Margrit Cécile von Braun, Dr. von Braun and Iris Careen von Braun. (U.S. Army)

In 1960 von Braun and his team were transferred from the Army Ballistic Missile Agency to NASA’s new Marshall Space Flight Center at Redstone Arsenal. He was now able to pursue his original interest, manned flight into space. Work proceeded on the Saturn rocket series, which were intended to lift heavy payloads into Earth orbit. This resulted in the Saturn A, Saturn B and the Saturn C series, ultimately becoming the Saturn V moon rocket.

Saturn SA-1 accelerates after liftoff, 27 October 1962. (NASA)
Apollo-Saturn IB AS-201 launch from Pad 34, Kennedy Space Center, 26 February 1966. (NASA)

With the Apollo Program coming to an end, Dr. von Braun left NASA in 1972. A year later, he was diagnosed with kidney cancer. Wernher von Braun died of pancreatic cancer, 17 June 1977 at the age of 65 years.

Apollo 4 Saturn V (AS-501) on the launch pad at sunset, the evening before launch, 8 November 1967. (NASA)
Saturn V first stage F-1 engines running, producing 7.5 million pounds of thrust. Ice falls from the rocket. The hold-down arms have not yet been released. (NASA)
Dr. von Braun pauses in front of the Apollo 11/Saturn V at the Kennedy Space Center (KSC). (NASA MSFC-6901046)

© 2019 Bryan R. Swopes

16 March 1966, 16:41:02.389 UTC, T plus 0.389

Gemini VIII lifts off from Launch Complex 19, Kennedy Space Center, 17:41:02 UTC, 16 March 1966. (NASA)
Gemini VIII lifts off from Launch Complex 19, Cape Kennedy Air Force Station, 16:41:02 UTC, 16 March 1966. (NASA)

16 March 1966: At 16:41:02.389 UTC (12:41:02 p.m. Eastern Standard Time), forty years to the day after the launch of Dr. Robert Goddard’s first liquid-fueled rocket, Gemini VIII, with command pilot Neil Alden Armstrong and pilot David Randolph Scott, lifted off from Launch Complex 19 at the Cape Kennedy Air Force Station, Cape Kennedy, Florida, aboard a Titan II GLV booster. Their mission was to rendezvous and dock with an Agena Target Vehicle launched earlier aboard an Atlas rocket.

Gemini VIII/Titan GLV-8 accelerates toward Low Earth Orbit, 16 March 1966. (NASA, MSCF-9141927)

Gemini VIII entered a 86.3  × 146.7 nautical mile (99.3 × 168.8 statute miles/160 × 271.7 kilometers) elliptical orbit. The spacecraft was traveling at 17,549 miles per hour (28,242 kilometers per hour).

The Gemini Agena Target Vehicle seen from Gemini VIII, 16 March 1966. (David R. Scott, NASA)

The docking, the first ever of two vehicles in Earth orbit, was successful, however after about 27 minutes the combined vehicles begin rolling uncontrollably. The Gemini capsule separated from the Agena, and for a few minutes all seemed normal. But the rolling started again, reaching as high as 60 r.p.m.

The astronauts were in grave danger. Armstrong succeeded in stopping the roll but the Gemini’s attitude control fuel was dangerously low.

David R. Scott and Neil A. Armstrong, flight crew of Gemini VIII. (NASA)

The pilots’ report reads:

     Shortly after sending encoder command 041 (recorder ON), roll and yaw rates were observed to be developing. No visual or audible evidence of spacecraft thruster firing was noted, and the divergence was attributed to the GATV.

     Commands were sent to de-energize the GATV ACS, geocentric rate, and horizon sensors, and the spacecraft Orbital Attitude and Maneuver System (OAMS) was activated.

     The rates were reduced to near zero, but began to increase upon release of the hand controller. The ACS was commanded on to determine if GATV thruster action would help reduce the angular rates. No improvement was noted and the ACS was again commanded off. Plumes from a GATV pitch thruster were visually observed, however, during a period when the ACS was thought to be inactivated.

     After a period of relatively stable operation, the rates once again began to increase. The spacecraft was switched to secondary bias power, secondary logics, and secondary drivers in an attempt to eliminate possible spacecraft control-system discrepancies. No improvement being observed, a conventional troubleshooting approach with the OAMS completely de-energized was attempted, but subsequently abandoned because of the existing rates.

     An undocking was performed when the rates were determined to be low enough to precluded any recontact problems. Approximately a 3 ft/sec velocity change was used to effect separation of the two vehicles.

     Angular rates continued to rise, verifying a spacecraft control-system problem. The hand controller appeared to be inactive. The Reentry Control System (RCS) was armed and, after trying ACME-DIRECT and then turning off all OAMS control switches and circuit breakers, was found to be operative in DIRECT-DIRECT. Angular rates were reduced to small values with the RCS B-ring. Inspection of the OAMS revealed that the no. 8 thruster had failed to open. Some open Attitude Control and Maneuver Electronics (ACME) circuit breakers probably accounted for the inoperative hand controller noted earlier. All yaw thrusters other than number 8 were inoperative. Pitch and roll control were maintained using the pitch thrusters. . .

      All four retrorockets fired on time. . . .

GEMINI PROGRAM MISSION REPORT, GEMINI VIII, Gemini Mission Evaluation Team, National Aeronautics and Space Administration, Manned Spacecraft Center, Houston, Texas, , MSC-G-R-66-4, Section 7 at Pages 7-21 and 7-22

The mission was aborted and the capsule returned to Earth after 10 hours, 41 minutes, 26.0 seconds, landing in the Pacific Ocean at N. 25° 12′, E. 136° 05′. U.S. Air  Force pararescue jumpers (“PJs”) parachuted from a Douglas C-54 transport and attached a flotation collar to the Gemini capsule. The astronauts were recovered by the Gearing-class destroyer USS Leonard F. Mason (DD-852), about three hours later..

The Gemini VIII spacecraft is displayed at the Neil Armstrong Air and Space Museum, Wapakoneta, Ohio.

Gemini VIII with flotation collar. (NASA)

The two-man Gemini spacecraft was built by the McDonnell Aircraft Corporation of St. Louis, Missouri, the same company that built the earlier Mercury space capsule. The spacecraft consisted of a series of cone-shaped segments forming a reentry module and an adapter section. It had an overall length of 18 feet, 9.84 inches (5.736 meters) and a maximum diameter of 10 feet, 0.00 inches (3.048 meters) at the base of the equipment section. The reentry module was 11 feet (3.353 meters) long with a maximum diameter of 7 feet, 6.00 inches (2.347 meters). The Gemini re-entry heat shield was a spherical section with a radius of 12 feet, 0.00 inches (3.658 meters). The weight of the Gemini spacecraft varied from ship to ship. Gemini VIII weighed 8,351.31 pounds (3,788.09 kilograms) at launch. Spacecraft 8 was shipped from the St. Louis factory to Cape Kennedy on 2 January 1966.

Artist’s concept of Gemini spacecraft, 3 January 1962. (NASA-S-65-893)

The Titan II GLV was a “man-rated” variant of the Martin SM-68B intercontinental ballistic missile. It was assembled at Martin’s Middle River, Maryland plant so as not to interfere with the production of the ICBM at Denver, Colorado. Twelve GLVs were ordered by the Air Force for the Gemini Program.

Titan II GLV, (NASA Mission Report, Figure 3-1, at Page 3–23)

The Titan II GLV was a two-stage, liquid-fueled rocket. The first stage was 70 feet, 2.31 inches (21.395 meters) long with a diameter of 10 feet (3.048 meters). It was powered by an Aerojet Engineering Corporation LR87-7 engine which combined two combustion chambers and exhaust nozzles with a single turbopump unit. The engine was fueled by Aerozine 50, a hypergolic 51/47/2 blend of hydrazine, unsymetrical-dimethyl hydrazine, and water. Ignition occurred spontaneously as the components were combined in the combustion chambers. The LR87-7 produced approximately 430,000 pounds of thrust (1,912.74 kilonewtons). It was not throttled and could not be shut down and restarted. Post flight analysis indicated that the first stage engine of GLV-8 had produced an average of 461,080 pounds of thrust ( kilonewtons).

The second stage was 25 feet, 6.375 inches (7.782 meters) long, with the same diameter, and used an Aerojet LR91 engine which produced approximately 100,000 pounds of thrust (444.82 kilonewtons), also burning Aerozine 50. GLV-7’s LR91 produced an average of 102,735 pounds of thrust ( kilonewtons).

The Gemini/Titan II GLV VIII combination had a total height of 107 feet, 7.33 inches (32.795 meters) and weighed 345,359 pounds (156,652 kilograms) at ignition.

The Atlas-Agena Target vehicle takes off at Launch Complex 14, 17:00:00 UTC, 16 March 1966. (NASA)
The Atlas-Agena Target Vehicle takes off at Launch Complex 14, Cape Kennedy Air Force Station, 15:00:03 UTC, 16 March 1966. (NASA)

© 2019, Bryan R. Swopes

10 March 1959

North American Aviation X-15A 56-6670 carried aloft by Boeing NB-52A Stratofortress 52-003. The absence of frost on the fuselage of the X-15 shows that no cryogenic propellants are aboard for this captive flight. The chase plane is a Lockheed F-104A-15-LO Starfighter, 56-0768. This Starfighter suffered an engine failure on take off at Edwards AFB, crashed and was destroyed, 30 June 1959. (NASA)

10 March 1959: With North American Aviation’s Chief Engineering Test Pilot Albert Scott Crossfield in its cockpit, the X-15 hypersonic research rocket plane was airborne for the first time. X-15A 56-6670 was carried aloft under the wing of the Boeing NB-52A Stratofortress drop ship, 52-003, for a series of captive flights. The purpose was to verify that all the systems on both the X-15 and the B-52 were properly functioning up to the point that the drop would occur.

The NB-52A Stratofortress flight crew, left to right: Harry W. ("Bill") Berkowitz, NAA, Launch Panel Operator; Captain John E. ("Jack") Allavie, USAF, Pilot; Captain Charles C. Bock, Jr., USAF, Aircraft Commander, at Edwards AFB, 7 February 1959. (U.S. Air Force)
The NB-52A Stratofortress flight crew, left to right: Harry W. (“Bill”) Berkowitz, NAA, Launch Panel Operator; Captain John E. (“Jack”) Allavie, USAF, Pilot; Captain Charles C. Bock, Jr., USAF, Aircraft Commander, at Edwards AFB, 7 February 1959. (U.S. Air Force via Jet Pilot Overseas)
North American Aviation X-15A 56-6670 carried aloft by Boeing NB-52A Stratofortress 52-003. The absence of frost on the fuselage of the X-15 shows that no cryogenic propellants are aboard for this captive flight. (NASA)

Fully settled in my tiny flight office, I could speak by radio to the B-52 pilot, Charlie Bock, who was about thirty feet away in the nose of the mother plane, out of sight. . .

As we sat, waiting at the end of the long runway while chase planes took off and circled, the clock on the instrument panel of the X-15 showed 0955. . . On signal, B-52 pilot Charlie Bock cobbed the eight engines, standing hard on the brake pedal. As the engines wound up to full military power, the X-15 trembled and the noise was tremendous. Through my radio earphones I heard Bock call a countdown for the benefit of the official movie cameramen who would record  every inch of the takeoff:

“Five . . . four . . . three . . . two . . . one. BRAKE RELEASE.”

One hundred thirty tons of aluminum, fuel, Inconel X, five men and the hope of a nation began rolling down the long runway. . .

As we rolled, the huge runway distance markers flashed by, clocking our path: 14,000 . . . 13,000 . . . 12,000 . . . 8,000. When the X-15 air-speed indicator reached 170 knots, I noted only a minor vibration. We would continue the takeoff. 6,000 . . . 5,000 . . . 4,000, and we broke ground. It was smooth and gentle, like the take-off of an airliner. The air-speed indicator crept up to 260 knots. The parched brown desert fell away. . . .

Always Another Dawn: The Story of a Rocket Test Pilot, by A. Scott Crossfield and Clay Blair, Jr., The World Publishing Company, Cleveland and New York, 1960, Chapters 34 and 35 at Pages 316–321.

X-15A 56-6670 under the wing of NB-52A 52-003 at high altitude. Scott Crossfield is in the cockpit of the rocketplane. Air Force Flight Test Center History Office, U.S. Air Force)
X-15A 56-6670 under the wing of NB-52A 52-003 at high altitude. Scott Crossfield is in the cockpit of the rocketplane. (Air Force Flight Test Center History Office, U.S. Air Force)

The gross weight of the combined aircraft was 258,000 pounds (117,000 kilograms). After a takeoff roll of 6,200 feet (1,890 meters) the B-52/X-15 lifted of at 168 knots (193 miles per hour/311 kilometers per hour). During the 1 hour, 8 minute flight the the B-52 climbed to 45,000 feet (13,716 meters) and reached a speed of 0.83 Mach (548 miles per hour/881 kilometers per hour).

The X-15A rocketplane was designed and built for the U.S. Air Force and the National Advisory Committee for Aeronautics (NACA, the predecessor of NASA) by North American Aviation, Inc., to investigate the effects of hypersonic flight (Mach 5+). Design work started in 1955 and a mock-up had been completed after just 12 months. The three X-15s were built at North American’s Los Angeles Division, at the southeast corner of Los Angeles International Airport (LAX), on the shoreline of southern California.

Test pilot Albert Scott Crossfield with X-15 56-6670 attached to the right wing pylon of NB-52A 52-003 at Edwards Air Force Base. (North American Aviation Inc.)

The first flight took place 8 June 1959, again, with Scott Crossfield in the cockpit of the Number 1 ship, 56-6670.

While earlier rocketplanes, the Bell X-1 series, the the Douglas D-558-II, and the Bell X-2, were airplanes powered by rocket engines, the X-15 was a quantum leap in technology. It was a spacecraft.

Like the other rocketplanes, the X-15 was designed to be carried aloft by a “mothership,” rather than to takeoff and climb to the test altitude under its own power. The carrier aircraft was originally planned to be a Convair B-36 intercontinental bomber but this was soon changed to a Boeing B-52 Stratofortress. Two B-52s were modified to carry the X-15: NB-52A 52-003, The High and Mighty One, and NB-52B 52-008, Balls 8.

From 8 June 1959 to 24 October 1968, the three X-15s were flown by twelve test pilots, three of whom would qualify as astronauts in the X-15. Two would go on to the Apollo Program, and one, Neil Alden Armstrong, would be the first human to set foot on the surface of the Moon, 20 July 1969. Joe Engle would fly the space shuttle. Four of the test pilots, Petersen, White, Rushworth, and Knight, flew in combat during the Vietnam War, with Bob White being awarded the Air Force Cross. Petersen, Rushworth and White reached flag rank.

One pilot, John B. (“Jack”) McKay, was seriously injured during an emergency landing at Mud Lake, Nevada, 9 November 1962. Michael James Adams, was killed when the Number 3 ship, 56-6672, went into a hypersonic spin and broke up on the program’s 191st flight, 15 November 1967.

Scott Crossfield prepares for a flight in the North American Aviation X-15A. Crossfield is wearing a David Clark Co. MC-2 full-pressure suit and MA-3 helmet, which he helped to develop. (NASA)

Flown by a single pilot/astronaut, the X-15 is a mid-wing monoplane with dorsal and ventral fin/rudders and stabilators. The wing had no dihedral, while the stabilators had a pronounced 15° anhedral. The short wings have an area of 200 square feet (18.58 square meters) and a maximum thickness of just 5%. The leading edges are swept to 25.64°. There are two small flaps but no ailerons. The entire vertical fin/rudder pivots for yaw control.

Above 100,000 feet (30,840 meters) altitude, conventional aircraft flight control surfaces are ineffective. The X-15 is equipped with a system of reaction control jets for pitch, roll and yaw control. Hydrogen peroxide was passed through a catalyst to produce steam, which supplied the control thrusters.

The forward landing gear consists of a retractable oleo strut with steerable dual wheels and there are two strut/skids at the rear of the fuselage. The gear is retracted after the X-15 is mounted on the NB-52 and is extended for landing by its own weight.

X-15A cockpit with original Lear Siegler instrument panel. (NASA)

The rocketplane’s cockpit featured both a conventional control stick as well as side-controllers. It was pressurized with nitrogen gas to prevent fires. The pilot wore an MC-2 full-pressure suit manufactured by the David Clark Company of Worcester, Massachusetts, with an MA-3 helmet. The suit was pressurized below the neck seal with nitrogen, while the helmet was supplied with 100% oxygen. This pressure suit was later changed to the Air Force-standardized A/P22S.

The X-15 is 50.75 feet (15.469 meters) long with a wing span of 22.36 feet (6.815 meters). The height—the distance between the tips of the dorsal and ventral fins—is 13.5 feet (4.115 meters). The stabilator span is 18.08 feet (5.511 meters). The fuselage is 4.67 feet (1.423 meters) deep and has a maximum width of 7.33 feet (2.234 meters).

North American Aviation, Inc. X-15A 56-6670 on Rogers Dry Lake, Edwards Air Force Base, California. (NASA)

The X-15s were built primarily of a nickel/chromium/iron alloy named Inconel X, along with corrosion-resistant steel, titanium and aluminum. Inconel X is both very hard and also able to maintain its strength at the very high temperatures the X-15s were subjected to by aerodynamic heating. It was extremely difficult to machine and special fabrication techniques had to be developed.

Since the X-15 was built of steel rather than light-weight aluminum, as are most aircraft, it is a heavy machine, weighing approximately 14,600 pounds (6,623 kilograms) empty and 34,000 pounds (15,422 kilograms) when loaded with a pilot and propellants. The X-15s carried as much as 1,300 pounds (590 kilograms) of research instrumentation, and the equipment varied from flight to flight. The minimum flight weight (for high-speed missions): was 31,292 pounds (14,194 kilograms) The maximum weight was 52,117 pounds (23,640 kilograms) at drop (modified X-15A-2 with external propellant tanks).

Initial flights were flown with a 5 foot, 11 inch (1.803 meters)-long air data boom at the nose, but this would later be replaced by the “ball nose” air sensor system. The data boom contained a standard pitot-static system along with angle-of-attack and sideslip vanes. The boom and ball nose were interchangeable.

Two Reaction Motors Division XLR11-RM-5 four-chamber rocket engines installed on an X-15. (NASA)

Delays in the production of the planned Reaction Motors XLR99 rocket engine forced engineers to adapt two vertically-stacked Reaction Motors XLR11-RM-5 four-chamber rocket engines to the X-15 for early flights. This was a well-known engine which was used on the previous rocketplanes. The XLR11 burned a mixture of ethyl alcohol and water with liquid oxygen. Each of the engines’ four chambers could be ignited individually. Each engine was rated at 11,800 pounds of thrust (58.49 kilonewtons) at Sea Level.

The Reaction Motors XLR99-RM-1 rocket engine was throttleable by the pilot from 28,500 to 60,000 pounds of thrust. The engine was rated at 50,000 pounds of thrust (222.41 kilonewtons) at Sea Level; 57,000 pounds (253.55 kilonewtons) at 45,000 feet (13,716 meters), the typical drop altitude; and 57,850 pounds (257.33 kilonewtons) of thrust at 100,000 feet (30,480 meters). Individual engines varied slightly. A few produced as much as 61,000 pounds of thrust (271.34 kilonewtons).

The XLR99 burned anhydrous ammonia and liquid oxygen. The flame temperature was approximately 5,000 °F. (2,760 °C.) The engine was cooled with circulating liquid oxygen. To protect the exhaust nozzle, it was flame-sprayed with ceramic coating of zirconium dioxide. The engine is 6 feet, 10 inches (2.083 meters) long and 3 feet, 3.3 inches (0.998 meters) in diameter. It weighs 910 pounds (413 kilograms). The Time Between Overhauls (TBO) is 1 hour of operation, or 100 starts.

Thiokol Reaction Motors Division XLR99-RM-1 rocket engine. (U.S. Air Force)

The XLR99 proved to be very reliable. 169 X-15 flights were made using the XLR99. 165 of these had successful engine operation. It started on the first attempt 159 times.

The highest speed achieved during the program was with the modified number two ship, X-15A-2 56-6671, flown by Pete Knight to Mach 6.70 (6,620 feet per second/4,520 miles per hour/ kilometers per hour) at 102,700 feet (31,303 meters). On this flight, the rocketplane exceeded its maximum design speed of 6,600 feet per second (2,012 meters per second).

The maximum altitude was reached by Joe Walker, 22 August 1963, when he flew 56-6672 to 354,200 feet (107,960 meters).

The longest flight was flown by Neil Armstrong, 20 April 1962, with a duration of 12 minutes, 28.7 seconds.

North American Aviation X-15A-1 56-6670 is on display at the Smithsonian Institution National Air and Space Museum. X-15A-2 56-6671 is at the National Museum of the United States Air Force.

North American Aviation Inc./U.S. Air Force/NASA X-15A 56-6670 hypersonic research rocketplane on display at the National Air and Space Museum. (NASM)

© 2019, Bryan R. Swopes

21 February 1961

Project Mercury astronauts with Convair F-106B-75-CO Delta Dart 59-0158. (NASA)
Project Mercury astronauts with Convair F-106B-75-CO Delta Dart 59-0158. (NASA)

21 February 1961: Final training begins for Mercury 7 astronauts. Alan Shepard, Gus Grissom and John Glenn are selected for the initial flights. Left-to-Right: Scott Carpenter, Gordon Cooper, John Glenn, Gus Grissom, Wally Schirra, Alan Shepard and Deke Slayton.

The aircraft in the photograph is a Convair F-106B-75-CO Delta Dart, 59-0158, a two-place supersonic interceptor trainer.

© 2015, Bryan R. Swopes