ARNOLD AIR FORCE BASE, Tenn. -- Writers across various websites and periodicals have used an array of adjectives to describe the splendor of the XB-70 Valkyrie.
When perusing internet search results on the aircraft, XB-70 knowledge seekers are likely to come across descriptors such as “sleek,” “futuristic,” “advanced,” “exotic,” “ambitious,” “unusual” and “fast.”
One word, however, regardless of author or year of publication, appears frequently in association with the XB-70 – “experimental.”
Although only two were ever built, the XB-70 has seemingly achieved a legendary status in the pantheon of military flying machines.
Arnold Engineering Development Complex played a significant role in the development of the planned supersonic bomber, which made its maiden flight 60 years ago this month.
The XB-70 was conceived for the U.S. Air Force Strategic Air Command in the 1950s. According to the National Museum of the United States Air Force, it was around the middle of that decade that Air Force officials expressed their desire to see the development of a new bomber that could fly faster and higher than the B-52 it would replace.
With its planned cruise speed of Mach 3 – three times the speed of sound – and an operating altitude of 70,000 feet, it was believed the XB-70 was just the aircraft to meet this challenge.
To achieve its Mach 3 performance, the XB-70 was designed to “ride” its own shockwave, akin to a surfer riding an ocean wave. The shape resulting from this design used a delta – or triangular-shaped - wing on a slab-sided fuselage that contained six jet engines to power the aircraft. The outer wing panels were hinged.
Beginning in the late 1950s and continuing through the mid-1960s, testing was conducted at Arnold Air Force Base, headquarters of AEDC, in support of the XB-70 program. The majority of this work was accomplished before the first Valkyrie was completed.
The first user airbreathing engine test in the 16-foot transonic wind tunnel at Arnold AFB occurred on March 25, 1958, on one of the nozzles proposed for the XB-70 aircraft.
The following year, a model of the Valkyrie underwent testing in Tunnel A of the von Kármán Gas Dynamics Facility at Arnold AFB. Scale models of bombs were dropped from the model of the proposed XB-70 in the wind tunnel to assess their aerodynamic characteristics.
In 1961, YJ93 turbojet engine development tests were started in further support of XB-70 development, as the YJ93 was designed to serve as the powerplant for the Valkyrie.
Plans for the XB-70 would soon shift. In 1961, before the first XB-70 prototype was even built, the bomber program was canceled due to funding limitations. According to the National Museum of the United States Air Force, the expense of the Valkyrie coupled with concerns that its survival could not be guaranteed against future Soviet defenses led to this decision.
But the XB-70 wasn’t completely grounded. While the bomber program had been canceled, officials still saw value in the Valkyrie. The U.S. Air Force ordered a pair of XB-70s to be used as research aircraft for the study of aerodynamics, propulsion and other subjects related to large supersonic aircraft. With this renewed purpose, construction was subsequently completed on two prototypes.
This change in course did not quash XB-70-centric testing at Arnold.
Beginning in August 1962, tests on a scale version of the XB-70 inlet with a full-scale 30,000-pound-thrust class YJ93 engine installed were conducted in the 16-foot supersonic wind tunnel at Arnold. This test article weighed 210,000 pounds and measured 75 feet in length, making it one of the largest models ever texted at the installation.
These tests subjected the engine/inlet combination to a broad range of simulated flight conditions at high speeds and altitudes to assess engine/inlet compatibility.
Following its completion, the first XB-70 prototype was rolled out from its factory near Palmdale, California, before a crowd of several thousand onlookers on May 11, 1964.
That same month, several months before the XB-70 took to the sky for the first time, the pilots who were to perform the first test flights operated the YJ93 engine while it was being tested under simulated flight conditions in the Rocket Test Facility at Arnold AFB. This was done to help the pilots familiarize themselves with the performance characteristics of the engine.
The first XB-70 made its first flight – a relatively short trip from Palmdale to Edwards Air Force Base, California – on Sept. 21, 1964. The aircraft achieved Mach 3 flight in October 1965.
The second XB-70 made its first flight in July 1965. According to NASA, it achieved Mach 3 for the first time in January 1966. However, in June of that year, this second Valkyrie was destroyed following an accidental midair collision with an F-104N Starfighter during a photoshoot in California.
In 1967, the U.S. Air Force transferred the remaining XB-70 to NASA in support of the National Supersonic Transport Program, according to the National Museum of the United States Air Force. The aircraft was used by the receiving agency as its primary aircraft to investigate SST operations. The American SST program was canceled in 1971.
The final XB-70 flight took place on Feb. 4, 1969. The now-retired Valkyrie was flown from Edwards AFB to Wright-Patterson Air Force Base, Ohio, to be displayed in what was then known as the Air Force Museum, now known as the National Museum of the United States Air Force.
According to NASA, the first XB-70 prototype made 83 flights totaling 160 hours and 16 minutes, while the second made 46 flights totaling 92 hours and 22 minutes.