NASA strapped a rocket plane to a B-52's wing and it flew to the edge of space

Before NASA could send astronauts into orbit, it needed to understand what happened to aircraft and pilots at the very edge of the atmosphere, at speeds and altitudes no conventional aircraft could reach. The vehicle it built to find out was the North American X-15, a rocket-powered research aircraft designed to fly faster and higher than anything before it. The aircraft it chose to carry the X-15 into the sky was the B-52 Stratofortress.

The Mothership

Two B-52s were modified for the X-15 programme: NB-52A ‘The High and Mighty One’ (serial 52-0003) and NB-52B ‘Balls 8’ (serial 52-0008). A pylon was mounted under the right wing of each bomber, designed to carry the X-15 in a semi-recessed position beneath the wing. The B-52 would take off with the X-15 attached, climb to approximately 45,000 feet, accelerate to around 500 miles per hour, and then release the rocket plane. Once dropped, the X-15's own rocket engine would ignite and the aircraft would accelerate and climb far beyond anything the B-52 could achieve.

Mach 6.7 And The Edge Of Space

Over nearly a decade of flight testing, from 1959 to 1968, the X-15 made 199 flights, all launched from a B-52 mothership. Balls 8 served as the launch aircraft for 140 of those 199 flights. The X-15 reached a maximum speed of 4,520 miles per hour, Mach 6.7, and a peak altitude of 354,200 feet, more than 67 miles above the Earth's surface. At that altitude, the sky is black, the curvature of the Earth is visible, and the aircraft is technically in space by most international definitions. Several X-15 pilots, including Neil Armstrong, who would later command Apollo 11, earned astronaut wings for flights that exceeded 50 miles in altitude.

The Data That Built The Space Programme

The X-15 programme was not just about setting records. Every flight generated aerodynamic, thermal, and physiological data that fed directly into NASA's human spaceflight programmes. The X-15 tested heat-resistant materials, reaction control systems for manoeuvring in near-vacuum conditions, and the effects of extreme speeds and altitudes on airframes and pilots. This data was used in the design and development of the Mercury, Gemini, and Apollo spacecraft, and later contributed to the development of the Space Shuttle's thermal protection system and re-entry profile.

A Bomber That Helped Reach The Moon

The B-52 was designed to carry nuclear bombs across oceans. Instead, one of its most significant contributions to history was carrying a small black rocket plane under its wing and dropping it into the upper atmosphere. Balls 8 flew its last X-15 mission in 1968 and continued serving NASA as a launch platform for other experimental vehicles for decades afterward, finally retiring in 2004 after 53 years of service. It is now on permanent display at the Edwards Air Force Base museum in California, a Cold War bomber that, in an unexpected turn of history, helped build the road to the Moon.