Hope you've got an Anti-Missile "B", friend...
Should you be familiar with Flying Buffalo's ever-so-tasteful Nuclear War card game, you will recognise the card above. Yet, even when the game was invented in 1965 (by Doug Malewicki), the aircraft shown had already been cancelled - strategic thinking (and defensive technology) had moved on while it was under development. Even though a brief outbreak of political dick-waving during the 1960 presidential election seemed to offer the program some hope, the harsh realities of post-election budgeting resulted in it being killed off. Of the two prototypes retained for research, one was lost in a fatal mid-air collision in 1966, and the other now resides in non-flying condition in a museum at Wright-Patterson AFB in Ohio.
The real thing, or at least the XB-70 prototype.
This is without doubt from the same stable as the RA-5C Vigilante, though it also carries something of Concorde about it. It exudes the same confident, sleek futurism. It looks like something from an episode of Thunderbirds, a fantasy of 10-year-old sci-fi fans everywhere. Despite its destructive function, it's a thing of beauty, waiting only to be perversely sexualised by J. G. Ballard. This is what a big, fast aircraft ought to look like...
Some video. Apologies for the awful music; it appearsto be obligitary for
aviation videos on YouTube to have teeth-gridingly dreadful soundtracks.
Development
In the late 1950s, when the requirement was issued for a supersonic long-distance bomber, the only effective defence against such aircraft was the jet interceptor, so the Valkyrie was designed for speed at altitude. But achieving and sustaining Mach 3, and being able to carry enough fuel to reach distant targets and return afterwards, were conflicting requirements, especially using the technology of the time. Investigations into the possibility of nuclear powered aircraft had led into a dead end; if you don't want your crews to die of radiation poisoning, you have to carry too much shielding to make the design viable, and the consequences of a crash on friendly territory become terrifying. The initial designs included such attempted solutions as boron-enriched "zip fuel" carried in huge drop tanks (the "floating panels" shown on the schematic below).
Early ideas for the deep penetration bomber program.
The breakthrough in the design of the XB-70 was to use the peculiar characteristics of supersonic flight to help, rather than hinder, the areodynamic characteristic of the airframe. It is possible to manipulate the shockwaves produced by the sharp surfaces of the vehicle in supersonic airflow, so that they produce high pressure areas beneath the craft ("compression lift"). This requirement determined the underslung mounting of a triangular phalanx of air intakes for the Valkyrie's six engines, which in turn gives the plane its distinctive appearance - a long thin forward fuselage, thrusting out like a swan neck, bears the cockpit way out beyond the main body. An additional measure to increase efficiency at high Mach was to allow the outboard section of wing to cant downwards, creating a "tunnel" of airflow beneath the craft, and moving the centre of lift forward to reduce the amount of pilot input required to maintain the aircraft in a correct attitude.
Looking more like the end product.
The need to reduce weight also produced design innovations. Without availability of the sort of composite materials which were used in later aircraft (such as the civilian Beechcraft Starship I described a couple of weeks ago), the airframe weight was brought down - and the problems of high temperatures during supersonic flight tackled - by use of "sandwich" panels, consisting of two layers of stainless steel separated by honeycomb foil.
These innovations increased the efficiency, and decreased the weight, of the design sufficiently to obviate the need for drop tanks (the boron-enrichment was also dropped, but one of the bomb-bays was repurposed as an additional fuel tank). North American's design was accepted in early 1958 as the basis for the B-70 program. To reduce costs some systems, including the engines and escape capsules, were shared with the XF-108 Rapier interceptor program, also being developed by North American.
Artist's impression of the (never built) XF-108, and you can see
North American's design fingerprints all over it.
The project, however, was soon in trouble. Surface-to-air missile technology was developing rapidly, and thinking on bombing was changing. The requirement for a fast, high level delivery vehicle was disappearing in favour of high endurance subsonic bombers (such as the existing B-52) which could remain on patrol for long periods, or of low level attacks for which the B-70's high-altitude speed advantage was irrelevant. Nuclear weapon delivery over long distance was most effectively supplied by Intercontinental Ballistic Missiles; the Valkyrie had lost its mission. In late 1959 the program was effectively cancelled, though the construction of a prototype was to continue for research purposes.
At this point, politics briefly intervened. During the 1960 presidential election, the Democratic challenger, John F Kennedy, seeking to take over from Dwight Eisenhower, attempted to characterise the Republicans as weak on defence. The curtailment of the B-70 program was one of his bullet points, and prompted the Republican candidate, Richard M Nixon, to counter with a promise to reinstate the program. Even before the election, the Air Force returned the project to active status and further money was pledged by President Eisenhower, resulting in the ordering of a second prototype.
"I will reinstate the B-70 program."
"No, Senator, I will reinstate the B-70 program!"
Once Kennedy had won the election, however, the realities of the strategic situation and the vast amount of money that would be involved in continuing with the redundant B-70 program, resulted in a second and final termination of the project as anything other than an advanced technology testbed. A final attempt in Congress to restart the project - orchestrated by the notorious Air Force General Curtis LeMay and members with B-70 work potentially assigned to their districts - failed.
Harrison Storms, chief engineer of the XB-70 project, also designed the
Apollo Command Module, as well as having a ridiculously brilliant name.
Apollo Command Module, as well as having a ridiculously brilliant name.
So when the first prototype flew on 21 September 1964, it was as a research platform, with its crew reduced to two pilots, the navigator and bombardier stations having become supernumary. The maiden flight was not without incident - the undercarriage failed to retract, and one of the engines had to be shut down during flight. When the Valkyire landed, one set of wheels locked up and caught fire. Further flights - the Valkyrie broke the sound barrier on the third test in October - also showed up problems with the honeycomb skin, but these problems had been overcome by the time the second prototype took to the air in July 1965, and in January 1966 this aircraft attained Mach 3 for the first time. Prototype No.1 only surpassed Mach 3 once, but damaged the leading edge of its wing in doing so, and was limited to Mach 2.5 thereafter.
XB-70 No.1, rolling out at North American.
Tragedy
Despite the cancellation of the bomber program, the Valkyrie, with its spectacular performance and striking appearance, remained a glamorous aircraft. So on 8 June 1966, after the No. 2 prototype had completed a research flight, it carried out a prearranged rendez-vous with four other aircraft powered by engines from General Electric - F-4 Phantom, F-5 Freedom Fighter, T-38 Talon jet trainer, and F-104 Starfighter - for a publicity shoot.
The disastrous flight. There is no video of the actual collision, as the photo
shoot was over by the time the incident took place.
The five aircraft entered a tight formation and for twenty minutes, flew around at 20,000 feet whilst being filmed from a chase plane. The formation was just about to break up when disaster struck. Tucked under and to the right of the XB-70's was an F-104 flown by Joe Walker, a senior NASA test pilot who was classed as an astronaut as a result of flying at an altitude of over 100km (in an X-15 rocket plane). For reasons not fully understood, Walker allowed his plane to drift in too close to the huge Valkyrie, and the tail plane of his Starfighter made contact with the right wingtip of the bomber, flipping over. The much smaller aircraft then slid across the top of the XB-70, shearing off both vertical stabilisers (tails) and damaging both wings before exploding. The XB-70 was now uncontrollable, and went into a flat spin before pancaking into the desert four miles below. The pilot, North American test pilot Al White, managed to eject, but was seriously injured on landing (and from getting his arm trapped in the capsule as it closed). The co-pilot, Major Carl Cross, failed to eject from the doomed plane and was killed. It had been his first Valkyrie flight.
Just after the impact - the burning F-104 has disintegrated, while the
fatal damage to the XB-70's tail structure is easily visible.
The End...
With only one remaining airframe, and that limited to Mach 2.5 for safety reasons, the testing program was wound up in early 1969 and the first prototype flown to Dayton, Ohio, where it remains an exhibit at the National Museum of the US Air Force.
Like Concorde, the XB-70 is now nothing more than a museum piece.
... Or Was It?
It sometimes seems that there is a conspiracy theory to cover almost everything, and there are people who believe that the XB-70 program did not fully end with the two known prototypes. Allegedly, owing to initial plans to construct a third, somewhat modified prototype, which was cancelled at an early stage of construction, there was a full spare set of six engines which has never been accounted for. The idea is that this set of engines was utilised to complete an aircraft - supposedly designated SR-3 - which formed part of an ultra-secret "two-stage-to-orbit" space project codenamed "Blackstar". In this supposed project, the XB-70 derivative functions as the carrier aircraft for a spaceplane released at around 100,000 feet. This, it is suggested, was intended to be a replacement for the shuttle project.
This all seems rather unlikely. I am not an expert on the technical aspects of these things, but given that the exact design of the XB-70's underside was critical in producing the compression lift which allowed sustained Mach 3 flight, it seems unlikely that a spaceplane could be slung under the fuselage without major redesign. Furthermore, the lengthy gap between the end of the XB-70 project (1966) and the requirement for a shuttle replacement post-Challenger (early 1990s) makes the connection between the alleged SR-3 and the old bomber project seem strained. The "missing" engines seem to tie in with an incident when one of the prototypes ingested part of its own air intake, damaging all the engines - it seems more than possible that the spare set was substituted for the damaged one.
Artist's impression of the Blackstar spaceplane slung from an SR-3
XB-70 derivative. And monkeys might fly out of my behind...
XB-70 derivative. And monkeys might fly out of my behind...
But it would be nice it were true. The XB-70 was an extraordinary aircraft; in my opinion one of the most beautiful ever built, and an extraordinary technical achievement. But it had the misfortune to be produced at a time when it was becoming clear that sheer speed was no longer the trump card in aircraft design, military or civilian. Just as the B-70s lighting performance proved not to fit the changing strategic requirements of the late 1950s and early 60s, its distaff cousin Concorde would find that expensive and fast was beaten by cheap and slow in the passenger jet market.
The North American Aviation team did go on to build a supersonic heavy bomber - the B-1 Lancer, another project killed off and resuscitated more often than Doctor Who - but by then the company had merged with Rockwell, which would eventually be absorbed into Boeing. The B-1 didn't look that much like the XB-70, either, being a swing wing design and, to my eyes, rather bland (though, compared to the brutal B-2 Spirit, it's an oil painting). So the B-70 remains as a largely unrealised dream project, an icon of an unrealised future.
A B-1 Lancer operating over Afghanistan.
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