A Blog for Dallas Area Catholics

Flightline Friday: The YF-12A and USAF’s quest for a Mach 3 interceptor February 7, 2014

Throughout the 1950s, the United States spent tens of billions of very fat dollars developing a comprehensive defense against manned, air-breathing aircraft.  The nation was wallpapered with air defense radars, very expensive distant early warning radar sites were constructed in the high arctic, and thousands of interceptor aircraft were manned and at alert 24 hours a day.  Air defense bases ranged from Thule, Greenland near the Arctic Circle to Galena Air Base in western Alaska to bases all over the lower 48.  The Army had scores of land-based air defense missile sites with their own massive infrastructure.

The primary threat at that time was Soviet manned bombers armed with thermonuclear devices. Since even one of these bombers getting through would mean an unmitigated national catastrophe, the defense was oriented towards a 100% kill ratio.  Of course, such is very difficult to obtain, and over time, doubts about the perfect effectiveness of the air defense network gradually undermined support for it, but in the late 50s, support was still strong and the system was being built up to a huge climax.

One problem defense planners faced was the threat of supersonic bombers.  Throughout the 50s, all bombers had been subsonic, ranging from the 2000 B-29 copies the Soviets made by using captured US bombers (the Tu-4), to the 600 mph Tu-95 and Myasischchev M-4.  There was a democrat-orchestrated scare in the 1956 presidential election of a looming “bomber gap,” claiming that the US had fallen badly behind the Soviets in numbers of long range bombers. Such was furthest from the truth, the Soviets never had more than 200 strategic bombers at any one time throughout the history of the Cold War, compared to Strategic Air Command’s massive fleet of over 2000 bombers, but such was not clearly known at the time.

Even these high subsonic bombers posed a grave threat to the US air defense system. In the mid-50s, all US interceptors were subsonic themselves.  They had perhaps a 100 mph speed advantage over the bombers.  This was sufficient to deal with the obsolete Tu-4 (B-29 copies), but not for the new jet powered bombers.  The USAF thus instituted a program to develop a new generation of supersonic interceptors, with the goal being at least Mach 2 performance.  This was eventually achieved in the F-106, as I stated a few weeks ago.

Any interceptor needs to have at least twice the top speed of its target in order to have a credible response.  This may sound excessive, but in reality is the bare minimum needed.  This is because bombers tend to have cruising speeds very near their top speeds, while small fighter aircraft generally cruise at the same speeds as the bombers.  In order to overhaul a maneuvering or fleeing target, 2x speed is really necessary if the fighter is going to make the intercept before exhausting its fuel.  There are a lot of complex factors involved in all this, but the 2x rule of thumb is a pretty good one.

It should be obvious, then, that even the brand new Mach 2.3 capable F-106 were not going to be sufficient to deal with a

F-108 mockup

notional Soviet supersonic bomber.  The Soviets were working on such, but never got a truly strategic, supersonic bomber into service until the 1980s, but the US did not know that at the time.  USAF had fielded a new supersonic medium bomber, the B-58 Hustler, in service, and if the US could field such a craft, it was feared the Soviet could, too.  Thus, USAF began a program in 1958 called the Long Range Interceptor-Experimental (LRIX) to develop a Mach 3+ capable interceptor that would have a good capability against a Mach 1.5 bomber and a marginal capability against a Mach 2 bomber.  This program was being run in conjunction with a new bomber competition to field a Mach 3 bomber, which resulted in the glorious XB-70 Valkyrie.  Contracts for both the new bomber and the LRIX interceptor, now called the F-108, were issued to North American Aviation.

The F-108 program was really going along pretty smoothly, with the design continually refined during the period 1958-1960, when it was cancelled by the Eisenhower Administration.  U-2 overflights had convinced Ike that the Soviets had only a trifling bomber force, and that the Soviets were putting most of their emphasis into what they called long range rocket artillery, better known as intercontinental ballistic missiles.  He thus disfavored air defense in favor of the US Army’s fledgling Nike Zeus ballistic missile defense system (for a great overview of that system, see this).  The beautiful and very capable F-108 was consigned to the “might have been” category.

In spite of this cancellation, however, USAF remained convinced that the Soviets would likely field a supersonic bomber in the near future, since USAF was pressing ahead with its plans for the B-70.  In addition, the vast majority of the interceptor force, circa 1960, still consisted of subsonic and barely supersonic aircraft (the latter being the F-102).  All of these slower interceptors were really not sufficient to deal with even the Tu-95 “Bear” bombers it was known the Soviets were putting into service.  Furthermore, their avionics were ancient and they were rapidly aging out.  A replacement was needed to complement, and eventually supplant, the great F-106 Delta Dart.  The desired aircraft would be very much like the F-108, combining Mach 3 speed with advanced radars and other avionics to produce a new “ultimate interceptor.”

Luckily for the Air Force, the CIA had engaged the famous Clarence L. “Kelly” Johnson and his Lockheed Skunk Works to produce just that kind of aircraft.  Intended as a replacement for the U-2 reconnaissance plane, the “A-12” was a technological triumph of the highest order.  It was a product only the US aerospace industry, at its incredibly peak circa 1960-1970, could produce.  Telling it’s story would require a whole ‘nuther post, so we’ll move on.

The A-12 was the progenitor of the well known SR-71 Blackbird, the Mach 3.5, 90,000 ft+ aircraft that was famously shot at hundreds of times, but never shot down.

YF-12 with “chopped chines”

As top USAF leadership observed the A-12 project developing in the early 60s, they realized they had the aircraft they had always wanted for an interceptor, and, wonderfully enough, it’s development had been paid for by someone else’s budget.  It was quickly seen that the A-12, with it’s incredible performance and long range, would make an ideal interceptor.  The Air Force commissioned some modifications be made to remove the reconnaissance equipment and replace it with missiles and a fire control radar, and the YF-12A was born.

The YF-12A as produced had a top speed of 2100 mph (Mach 3.2, a little less than the SR-71 due to aerodynamic changes for the interceptor role), a peak altitude of around 85,000 ft (ditto), and a 3000 mile range.  All were huge improvements over the F-106.  In addition, the YF-12A incorporated very advanced avionics, including the world’s first look-down shoot-down fire control radar, the AN/ASG-18, and two very early, very rudimentary infra-red search and track devices at the leading edges of the now incomplete forward chines.  The YF-12 had a much larger nose to incorporate this radar with it’s 40″ diameter dish.  The “chines” which ran around the nose of the A-12 and SR-71, which served both an aerodynamic and a “stealth” or radar cross section reduction role, stopped about even with the leading edge of the canopy.

YF-12A with AIM-47 missile

The YF-12A was armed with 3 AIM-47 Falcon missiles, each with either a 250 kt nuclear warhead (guaranteed kill radius – over 1 mile) or 400 lb of conventional high explosive.  The AIM-47 was the first air-to-air missile with it’s own radar seeker, making it the first true “fire and forget” missile.  It had a range of over 100 nm.  An alternative weapon for the YF-12 was a ground attack version of the AIM-47 called the AGM-76 Falcon.  This also came with either a 250 kt warhead or a large conventional one, and had a similar range.  The AGM-76/YF-12 combination was to be used to take out Soviet radar sites and SAM batteries, allowing the B-70 fleet easier access to Soviet airspace.  The Valkyrie’s would have carried some of those same missiles, themselves.

During testing, AIM-47s launched from YF-12As scored a 100% kill ratio, with the one “failure” being due to a problem with test equipment, not the missile.  The look-down shoot-down capability was proved when a YF-12 flying at Mach 3.2 and 74,000 ft shot down a target just 500 ft off the ground – an extremely successful performance at that time.

The YF-12A first flew, out at Groom Lake (Area 51) in August, 1963.  By late 1964 testing was complete and the aircraft was ready to enter service.  Several speed and altitude records had already been set with the three test aircraft. USAF requested, and Congress approved, funding for 93 production F-12B models.

But, this is one of history’s greatest villains and incompetents, Robert Strange McNamara, entered in.  McNamara had an inveterate hatred of the Air Force, ever since he had unsuccessfully opposed the USAF becoming a separate service in 1947.  He especially disliked anything related to manned bombers and air defense.  He also, by this time, had by his lies and temporizing statements, managed to help guide the US into the Vietnam War.  That war was gobbling up vast swaths of the defense budget, already.  He needed more money for the large standing army he had created, to go fight the war that creation made all but inevitable (since Kennedy created a very large, standing, peacetime army, we have not gone 10 years without that Army being used in a ground conflict somewhere).

So, even though, for three consecutive years, Congress approved funding for the F-12B interceptor, McNamara, quite illegally, refused to spend it.  It was an early example of that lawless rule by decree that progressives so favor, and which we see in spades in our current ruling junta.   So the F-12 never entered squadron service, and became another aviation afterthought.  The Air Force never got it’s Mach 3 interceptor.

In a sense, however, McNamara was right.  The US never did have to fend off invading waves of Soviet bombers (nor missiles, thank God).  But if we had, we would have had to do it, well into the 1980s, with 1950s vintage aircraft, and only a few hundred of those.  Incredibly, in this country today, at this moment, there are not even 50 aircraft assigned to air defense.  Thus, 9/11, at least to some degree.

Proposed front cockpit for production F-12B – very similar to F-108, and very advanced for its day