How engineers used a B-52 to rapidly advance our understanding of supersonic flight.
The Challenge: The engineers have designed and developed a new aircraft that can fly five times the speed of sound (Mach 5), but it does not carry enough fuel to take off from a runway and climb to its operational altitude.
The Answer: launch it from another aircraft—the “mother ship”—that will carry it to its operational altitude so it can begin the flight from there. This article outlines a brief history of two B-52 aircraft that would support the X-15 program, one of which would continue in the role as a “mother ship” for another 35 years.
While the B-52 was not the first “mother ship” (a modified B-29 Superfortress bomber was used to launch the Bell X-1 and Chuck Yeager on the first supersonic flight in 1947), this is a brief history of two B-52s that defined and lived the role for nearly fifty years.
By the time the North American X-15 hypersonic test aircraft was ready for testing, the B-52 Stratofortress was available, and two B-52s were transferred to Edwards AFB to act as mother ships for the X-15.
The B-52s required extensive modifications. Due to the low fuselage ground clearance and landing gear arrangement of the B-52, the X-15 had to be mounted on a pylon under the wing of the aircraft, between the right inboard engine and the fuselage. An 8-feet section had to be removed from the right wing flap to allow room for the X-15’s vertical stabilizer.
In addition to the wing-mounted pylon, the aircraft were outfitted with liquid oxygen and hydrogen peroxide tanks in the bomb bay area to fuel the X-15 fuel tanks prior to launch. A launch control station was installed behind the cockpit with all of the instrumentation and controls needed to launch the test aircraft. Also, because the X-15 (and other test aircraft) were not visible from the cockpit, a small window was installed at the launch control station to allow the operator to see the X-15 cockpit. The first bomber modified was the third and last B-52A produced, serial number B-52A-0003. After modification in 1959, it was redesignated NB-52A and named “The High and the Mighty.”
The second was originally delivered to the Air Force in 1954 as an RB-52B, serial number B-52B-0008, equipped to be a reconnaissance aircraft. It was transferred to Edwards AFB in 1958 and modified to become an NB-52B. This aircraft was dubbed “Balls Eight” because, in a serial number, a series of zeros were referred to as “balls.”
Between 1959 and 1968, these two aircraft flew more than 60 captive carry and 199 X-15 launch missions. There were three X-15s in the program, one of which was destroyed in a crash. Today one of the remaining X-15s is on display at the National Air and Space Museum and the other can be seen and the National Museum of the Air Force.
NB-52A-0003 was retired in 1969 shortly after the end of the X-15 program, having flow 69 of the launch missions plus. Initially, it was stored at Davis Monthan AFB, but later given a home at the Pima Air & Space Museum in Tucson, Arizona. NB-52A-0003 is oldest B-52 in existence.
Balls Eight would deliver nearly 50 years of dedicated service to research and development. Retired in 2004, Balls 8 is now on display at the entrance to Edwards Air Force Base.
“It has been asserted that the Boeing NB-52B Stratofortress, carrying Air Force serial 52-0008, can lay claim to being the airplane that has seen and participated in more history than any other single airplane.
For forty-five years, the NB-52B was a fixture at Edwards Air Force Base. While the NB-52B is most famous for launching the three North American X-15 rocket planes, it continued to serve in the role of launch platform for a multitude of programs until its final mission on November 16, 2004.”(1)
In addition to the X-15, Balls Eight also carried and launched the Martin Marietta X-24 and other lifting body aircraft, followed by HiMAT, the Pegasus rocket and the unmanned scramjet-powered X-43, among others.
The Martin Marietta X-24A was a piloted, unpowered experimental aircraft developed to test lifting body concepts for unpowered reentry and landing—technology that would later be applied to the Space Shuttle.
Rockwell’s Highly Maneuverable Aircraft Technology (HiMAT) was an unmanned, powered NASA program to explore a range of technologies including canards, composite materials, digital flight controls, and remote piloting for use in future fighter aircraft.
Pegasus is an air-launched rocket designed to carry small satellites into low Earth orbit. First launched from Balls Eight in 1990, it remains active as of 2015. The four-stage rocket was launched at 40,000 feet. Later flights have been launched from a modified Lockheed L-1011.
Balls Eight’s last program was launching another hypersonic vehicle—the X-43A hypersonic research aircraft in 2004.
Balls Eight was finally retired on December 17, 2004 after 49 years in the air, having become the oldest active B-52 in service at that time. Balls Eight was also the only variant still flying other than the H model. Because of its specialized use, however, and many hours spent in being modified for each new mission, it had accumulated fewer flight hours than any other operational B-52 still in service.
Ref1: Balls Eight – History of the Boeing NB-52B Stratofortress Mothership by Brian Lockett (published April 26, 2015) is available from several online book sellers.