YF-12A / F-12B
-12A actually flew, the F-12B would have been built had McNamara not axed it.
-12A was an outgrowth of the CIA
's A-12 high-speed interceptor design. The YF
-12A was different in a number of ways. For one, it did not feature composite tailfins, using more conventional titanium pieces, and featured no RCS
-specialized-technology including RAM wedges. The aircraft featured a two-seat cockpit with the fire-control-officer occupying the rear seat situated which quite simply did not exist on the A-12, with the cockpit raised somewhat to improve visibility as part of USAF
specifications (even though it actually didn't make much of a difference as the plane didn't feature a clear-bubble canopy)
a larger nose to house the massive AN
-18 radar system and the associated heat-shield to go with it, and IRST-scanners to work with the radar and cutback chines since the radar and IRST's in their initial configuration couldn't see through the chines properly. Three of the chine bays were fitted to carry the GAR-9/AIM-47 long-range air-to-air missile with the forward right chine bay carrying some of the equipment associated with the fire-control-system, and the camera bay and some additional area cut out of the fuselage behind the landing gear to carry a fourth missile bay. Because the different nose configuration and raised cockpit reduced directional stability, the aircraft was fitted with two fixed fins under each engine-nacelle and one extendable/retractable fin under the centerline which extends out when the gears go up. The AN
-18 with it's look-down/shoot-down and look-up/shoot-up capabilities made it extrordinarily effective at not just shooting down ordinary bombers, or even high-speed bombers, but low altitude aircraft flying low over the deck, and was even tested to evaluate it's capabilities against shooting down ICBM's. Using the look-down/shoot-down capability the AN
-18 and AIM-47 pair shot down targets from 40,000 feet all the way down to 500 feet, coming in opposite directions with enormous closure rates with only one miss, which was chalked down to a missile failure rather than the target successfully evading the missile. The success rate against ICBM's were and are classified.
To enable the YF
-12A to be rapidly started in a hurry to be able to start it and get it to the runway and into the air in a reasonable ammount of time, a chemical-start system which uses a chemical reaction to spin the J-58's rapidly up to speed.
The F-12B would have been a production model of the YF
-12A. It would have looked more like the SR
-71, featuring chines, as the radar-design was modified, featuring a new flat antenna that could now see through the chines, with all the large fire-control hardware equipment inside the plane's nose and fitted with properly profiled IRST scanners. The plane to my knowledge would have still featured a slightly raised cockpit as before, and was to still mount ventral fins under the engine-pods, but the central fin was deleted. The airplane was also to carry a fuel capacity that would have more closely reflected that of the SR
-71. To my knowledge the plane also would have also, likely, featured a bob-tail like the SR
-71, and may have been fitted with systems that would have allowed the plane to start at least one engine on it's own. The central missile-bay was to have been deleted with all four missiles carried in chine-bays. To reduce size, the new AIM-47B was to have been fitted with folding fins to allow it to fit in a slightly smaller bay.
There is some data to suggest that the F-12B had been considered for ground-attack roles, as it's radar could look down and shoot-down. To my knowledge, the idea of using the AN
-18 radar for hitting ground targets had been thought of before the YF
-12 was even built, when the radar platform was to have been part of the F-108 Rapier design, which in addition to being a two-man interceptor capable of operating outside of the SAGE network, was also to have been used as an XB-70 escort, carrying a modified AIM-47A with a neutron-kill warhead to neutralize nukes (I checked, it's not classified-- it's in a book I have)
, and also an AIM-47 derivative using a different seeker, but the same warhead, engine and airframe known as the AGM-76A. The AN
-18 would have been programmed with additional modes for this to work, but to my knowledge was deemed do-able even when the F-108A Rapier was around. It is only logical to conclude that the F-12A could have been fitted with the AGM-76A variant and used for ground attacks during the war of it's time, Vietnam, in addition to it's interceptor role. The AIM-47 to the best of my knowledge was originally designed with a 250-kt thermonuclear warhead, but during the YF
-12A program was re-fitted with a conventional warhead. Had the design entered service, I'm not sure if it would have had the nuclear-tipped variant as an option in an "end of the world" intercept scenario with a swarm of bombers coming in over the pole.
Unfortunately a number of factors contributed to the YF
-12/F-12B, and even the whole A-12/SR-71 program's demise . One was the fact that interceptors were considered outdated as ICBM's were unstoppable and many people chose to believe that ICBM's would completely replace bombers. The other was Robert McNamara and the fact that the YF
-12 program revealed how vulnerable the TFX program would be if the Russians developed a counterpart. Rather than realize the error of his ways, and either find another purpose for the F-111, replace it, modify it etc, he decided to simply take out the F-12 program. After all, the F-111 was his wet dream, lots of parts commonality, cheaper than building two or three specialized fighters which would be far more effective, and it looked good on graphs and charts. First he, selected the F-106X, which by most purposes was a pretty impressive outgrowth of the F-106. I'm pretty sure if it entered service it would have been given another designation as it was dramatically different than the regular F-106X... it featured bigger, more powerful engines, a pretty much completely re-designed inlet-system, complete titanium structure, the AN
-18 radar system, with a modified weapons bay (featuring a single AIM-47A in the center bay, and 2 x AIM-26's in the left and right bay)
, a canard, a raised cockpit with better visibility, and fuel-bladders in the wings. To my knowledge the real thing that made this design work was the use of mass-injection pre-compressor-cooling (MIPCC)
which is actually not all that different from water-injection, except in this case, it's not to boost thrust, it's to keep the engine from melting at high Mach numbers -- the F-106X was capable of Mach 5, although I'm not sure for how long it could hold that speed for. The design would cost a cool billion to build, while the YF
-12A already had been built and been tested, and money spent already, the F-12B would only cost 360 million to get it into service. Quite accurately showing McNamara's flawed judgement as a result of his sheer desire to get rid of the F-12B. In McNamara's final act of vindictive stupidity, he ordered *ALL
* the large-scale tooling on not just the YF
-12A, but the A-12, the M-21, and the SR
-71 (He also may have had it in for Kelly Johnson, also accounting for such actions)
, essentially killing every single blackbird program in one fell-swoop and making it impossible to build a new variant, or a better version (at least, not easily-- you theoretically COULD take one plane apart, and measure each part and make molds and tooling based on it)