North American Aviation X-15A-2 56-6671 on Rogers Dry Lake. In addition to the lengthened fuselage and external tanks, the nose wheel strut is longer and the windshields have been changed to an oval shape. A wheeled dolly supports the aft end of the rocketplane. (NASA)
3 November 1965: Major Robert A. Rushworth made the first flight of the modified X-15A-2 rocketplane, Air Force serial number 56-6671. After a landing accident which caused significant damage to the Number 2 X-15, it was rebuilt by North American Aviation. A 28-inch (0.71 meter) “plug” was installed in the fuselage forward of the wings to create space for a liquid hydrogen fuel tank which would be used for an experimental “scramjet” engine that would be mounted on the the ventral fin. The modified aircraft was also able to carry two external fuel tanks. It was hoped that additional propellant would allow the X-15A-2 to reach much higher speeds.
The first flight with the new configuration was an “envelope expansion” flight, intended to test the handling characteristics of the X-15A-2, and to jettison the tanks (which were empty on this flight) to evaluate the separation and trajectory as they fell away from the rocketplane in supersonic flight.
Boeing NB-52A Stratofortress 52-003, The High and Mighty One, with North American Aviation X-15A-2 56-6671 mounted to the pylon under its right wing. The external propellant tanks have been brightly painted to aid tracking after they are jettisoned. (U.S. Air Force)
The X-15A-2 was dropped from the Boeing NB-52A Stratofortress 52-003, over Cuddeback Lake, 37 miles (60 kilometers) northeast of Edwards Air Force Base in the Mojave Desert of southern California. This was the only time during the 199-flight X-15 Program that this lake was used as a launch point.
The X-15 was released at 09:09:10.7 a.m., PST. Bob Rushworth ignited the Reaction Motors XLR99-RM-1 rocket engine and it ran for 84.1 seconds before its fuel supply was exhausted. This engine was rated at 57,000 pounds of thrust (253.549 kilonewtons).
The X-15 climbed to 70,600 feet (21,519 meters) and reached Mach 2.31 (1,514 miles per hour/2,437 kilometers per hour.)
The test flight went well. The external tanks jettisoned cleanly and fell away. The recovery parachute for the liquid oxygen tank did not deploy, however, and the tank was damaged beyond repair.
Rushworth and the X-15A-2 touched down on Rogers Dry Lake after a flight of 5 minutes, 1.6 seconds.
Captain Charles Elwood (“Chuck”) Yeager, U.S. Air Force, with “Glamorous Glennis,” the Bell XS-1. (U.S. Air Force/National Air and Space Museum)
14 October 1947: At approximately 10:00 a.m., a four-engine Boeing B-29 Superfortress heavy bomber, piloted by Major Robert L. Cardenas, took off from Muroc Air Force Base (now known as Edwards Air Force Base) in the high desert north of Los Angeles, California. The B-29’s bomb bay had been modified to carry the Bell XS-1, a rocket-powered airplane designed to investigate flight at speeds near the Speed of Sound (Mach 1).
A Bell XS-1 rocketplane carried aloft in the bomb bay of a modified Boeing B-29-96-BW Superfortress, serial number 45-21800. (NASA)Captain Chuck Yeager with the Bell XS-1 on Muroc Dry Lake, 1947. (Chuck Yeager collection)
Air Force test pilot Captain Charles Elwood (“Chuck”) Yeager, a World War II fighter ace, was the U.S. Air Force pilot for this project. The X-1 airplane had been previously flown by company test pilots Jack Woolams and Chalmers Goodlin. Two more X-1 aircraft were built by Bell, and the second, 46-063, had already begun its flight testing.
Captain Yeager had made three glide flights and this was to be his ninth powered flight. Like his P-51 Mustang fighters, he had named this airplane after his wife, Glamorous Glennis.
Bob Cardenas climbed to 20,000 feet (6,096 meters) and then put the B-29 into a shallow dive to gain speed. In his autobiography, Yeager wrote:
“One minute to drop. [Jack] Ridley flashed the word from the copilot’s seat in the mother ship. . . Major Cardenas, the driver, starts counting backwards from ten. C-r-r-ack. The bomb shackle release jolts you up from your seat, and as you sail out of the dark bomb bay the sun explodes in brightness. You’re looking at the sky. Wrong! You should have dropped level. The dive speed was too slow, and they dropped you in a nose-up stall. . .
Cockpit of Bell X-1, 46-062, Glamorous Glennis, on display at the National Air and Space Museum. (Photo by Eric Long, National Air and Space Museum, Smithsonian Institution)
“I fought it with the control wheel for about five hundred feet, and finally got her nose down. The moment we picked up speed I fired all four rocket chambers in rapid sequence. We climbed at .88 Mach. . . I turned off two rocket chambers. At 40,000 feet, we were still climbing at .92 Mach. Leveling off at 42,000 feet, I had thirty percent of my fuel, so I turned on rocket chamber three and immediately reached .96 Mach. . . the faster I got, the smoother the ride.
“Suddenly the Mach needle began to fluctuate. It went up to .965 Mach—then tipped right off the scale. . . .”
—Brigadier General Charles E. Yeager, U.S. Air Force (Retired), Yeager, An Autobiography, by Chuck Yeager and Leo Janos, Bantam Books, New York, 1985, Pages 120, 129–130.
In his official report of the flight, Yeager wrote:
Date: 14 October 1947
Pilot: Captain Charles E. Yeager
Time: 14 Minutes
9th Powered Flight
1. After normal pilot entry and subsequent climb, the XS-1 was dropped from the B-29 at 20,000′and at 250 MPH ISA. This was slower than desired.
2. Immediately after drop, all four cylinders were turned on in rapid sequence, their operation stabilizing at the chamber and line pressure reported in the last flight. The ensuing climb was made at .85–.88 Mach, and, as usual, it was necessary to change the stabilizer setting to 2 degrees nose down from its pre-drop setting of 1 degree nose down. Two cylinders were turned off between 35,000′ and 40,000′, but speed had increased to .92 Mach as the airplane was leveled off at 42,000′. Incidentally, during the slight push-over at this altitude, the lox line pressure dropped perhaps 40 psi and the resultant rich mixture caused chamber pressures to decrease slightly. The effect was only momentary, occurring at .6 G’s, and all pressures returned to normal at 1 G.
3. In anticipation of the decrease in elevator effectiveness at speeds above .93 Mach, longitudinal control by means of the stabilizer was tried during the climb at .83, .88, and .92 Mach. The stabilizer was moved in increments of 1/4–1/3 degree and proved to be very effective; also, no change in effectiveness was noticed at the different speeds.
4. At 42,000′ in approximately level flight, a third cylinder was turned on. Acceleration was rapid and speed increased to .98 mach. The needle of the machmeter fluctuated at this reading momentarily, then passed off the scale. Assuming that the offscale reading remained linear, it is estimated that 1.05 Mach was attained at this time. Approximately 30% of fuel and lox remained when this speed was reached and the meter was turned off.
5. While the usual light buffet and instability characteristics were encountered in the .88–.90 Mach range and elevator effectiveness was very greatly decreased at .94 Mach, stability about all three axes was good as speed increased and elevator effectiveness was regained above .97 Mach. As speed decreased after turning off the motor, the various phenomena occurred n reverse sequence at the usual speed, and in addition, a slight longitudinal porpoising was noticed from .98–.96 Mach which controllable by the elevators alone. Incidentally, the stability setting was not changed from its 2 degree nose down position after trial at .92 Mach.
6. After jettisoning the remaining fuel and lox a 1 G stall was performed at 45,000′. The flight was concluded by the subsequent glide and a normal landing on the lake bed.
CHARLES E. YEAGER Capt., Air Corps
Chuck Yeager and flown the XS-1 through “the sound barrier,” something many experts had believed might not be possible. His maximum speed during this flight was Mach 1.06 (699.4 miles per hour/1,125.7 kilometers per hour).
Bell X-1 46-062 in flight. Note the “shock diamonds” visible in the rocket engine’s exhaust. (Photograph by Lieutenant Robert A. Hoover, U.S. Air Force)
The Bell XS-1, later re-designated X-1, was the first of a series of rocket powered research airplanes which included the Douglas D-558-II Skyrocket, the Bell X-2, and the North American Aviation X-15, which were flown by the U.S. Air Force, U.S. Navy, NACA and its successor, NASA, at Edwards Air Force Base to explore supersonic and hypersonic flight and at altitudes to and beyond the limits of Earth’s atmosphere.
The X-1 is shaped like a bullet and has straight wings and tail surfaces. It is 30 feet, 10.98 inches (9.423 meters) long with a wing span of 28.00 feet (8.534 meters) and overall height of 10 feet, 10.20 inches (3.307 meters). Total wing area is 102.5 square feet ( 9.5 square meters). At its widest point, the diameter of the X-1 fuselage is 4 feet, 7 inches (1.397 meters). The empty weight is 6,784.9 pounds (3,077.6 kilograms), but loaded with propellant, oxidizer and its pilot with his equipment, the weight increased to 13,034 pounds (5,912 kilograms). The X-1 was designed to withstand an ultimate structural load of 18g.
The X-1 is powered by a four-chamber Reaction Motors, Inc., XLR11-RM-3 rocket engine which produced 6,000 pounds of thrust (26,689 Newtons). This engine burns a mixture of ethyl alcohol and water with liquid oxygen. Fuel capacity is 293 gallons (1,109 liters) of water/alcohol and 311 gallons (1,177 liters) of liquid oxygen. The fuel system is pressurized by nitrogen at 1,500 pounds per square inch (10,342 kilopascals).
The X-1 was usually dropped from a B-29 flying at 30,000 feet (9,144 meters) and 345 miles per hour (555 kilometers per hour). It fell as much as 1,000 feet (305 meters) before beginning to climb under its own power.
The X-1’s performance was limited by its fuel capacity. Flying at 50,000 feet (15,240 meters), it could reach 916 miles per hour (1,474 kilometers per hour), but at 70,000 feet (21,336 meters) the maximum speed that could be reached was 898 miles per hour (1,445 kilometers per hour). During a maximum climb, fuel would be exhausted as the X-1 reached 74,800 feet (2,799 meters). The absolute ceiling is 87,750 feet (26,746 meters).
The X-1 had a minimum landing speed of 135 miles per hour (217 kilometers per hour) using 60% flaps.
Bell X-1 46-063 with its Boeing B-29 Superfortress carrier aircraft, 45-21800. (Flight Test Historical Foundation)
The three X-1 rocketplanes made a total of 157 flights with the three X-1. The number one ship, Glamorous Glennis, made 78 flights. On 26 March 1948, with Chuck Yeager again in the cockpit, it reached reached Mach 1.45 (957 miles per hour/1,540 kilometers per hour) at 71,900 feet (21,915 meters).
The third X-1, 46-064, made just one glide flight before it was destroyed 9 November 1951 in an accidental explosion.
The second X-1, 46-063, was later modified to the X-1E. It is on display at the NASA Dryden Research Center at Edwards Air Force Base.
Glamorous Glennis is on display at the Smithsonian Institution National Air and Space Museum, next to Charles A. Lindbergh’s Spirit of St. Louis.
Bell X-1, 46-062, Glamorous Glennis, on display in the Milestones of Flight gallery at the National Air and Space Museum, Washington, D.C. (Photo by Eric Long, National Air and Space Museum, Smithsonian Institution)
Viking 1 launch (Chicago Tribune)Viking 1 launch (AP Wirephoto/Baltimore Sun)
3 May 1949: at 9:14 a.m., Mountain Daylight Saving Time (15:14 UTC), the Viking 1 rocket was launched from the White Sands Proving Grounds in southern New Mexico. The rocket carried a 460 pound (210 kilogram) instrumentation payload.
This was the first launch of a U.S.-designed and -built rocket capable of carrying a payload to space.¹
Viking 1 surrounded by the service gantry. The rocket is angled to the north by 3°. (Drew Ex Machina)
Although the planned engine run time was 65 seconds, Viking 1’s engine shut down after 54.5 seconds. At that time, the rocket had reached a speed of 2,350 miles per hour (3,780 kilometers per hour). After the engine shut down, Viking 1 continued to climb on a ballistic trajectory to an altitude of 50 miles (81 kilometers). As it fell back to Earth, 291 seconds after launch, the rocket broke up and was scattered across many miles of the Proving Grounds.
Viking 1 was a single-stage liquid-fueled rocket. It was built by the Glenn L. Martin Company for the Naval Research Laboratory. It was constructed primarily of aluminum. The skin was rolled into a cylinder and welded. It was 47 feet, 7.5 inches (14.516 meters) long, 2 feet, 8 inches (0.813 meters) in diameter, with a fin span of 9 feet, 2.5 inches (2.807 meters). Each fin had an area of 15 square feet (1.39 square meters). The rocket had a gross weight of 10,824 pounds (4,910 kilograms).
A Reaction Motors XLR10-RM-2 rocket engine. (Reddit)
Viking 1 was powered by a Reaction Motors Inc. XLR10-RM-2 engine. It’s propellant was a mixture of ethanol and water, mixed at a ratio of 95:5. The oxidizer was liquid oxygen. The engine produced 20,800 pounds of thrust (92.523 kilonewtons) at Sea Level, and 24,800 pounds (110.316 kilonewtons) in vacuum. Fuel was fed to the engine by a turbopump driven by high-pressure hydrogen peroxide steam. Turning at 10,000 r.p.m., the turbopump provided propellant at a rate of 110 pounds (50 kilograms) per second.
Static test firing of the Viking 1 rocket engine. (Drew Ex Machina)
The engine was mounted on gymbals which were controlled by gyroscopes. By rapidly angling the engine exhaust away from the rocket’s centerline, the engine was able to stabilize the rocket. A British Pathé news film (available on YouTube) showing the launch of Viking 2 illustrates this:
¹ “Space” is defined as being above the von Kármán Line, the boundary between the Earth’s atmosphrere and outer space, at an altitude of 100 kilometers (62.14 miles)
