Form 12a: Fill & Download for Free

The USAF actually explored the use of the SR-71 as a pure interceptor (it was actually called the YF-12A, and was quite different than the SR), but it took a really long time to take-off, so the concept really wasn’t pursued any farther than building three prototypes of the interceptor version of the SR. Yes, the turning radius sucked, but it was able to intercept things pretty quickly once it got airborne. The YF had an extremely capable radar (which eventually became the AWG-9 in the F-14), and some very long-range missiles (which eventually morphed into the AIM-54 Phoenix), but it wasn’t very maneuverable; IIRC, it’s turning radius was about 100+ miles at speed.One of the prototype YF-12A’s with an AIM-47 Falcon missile staged next to it.The AIM-47 Falcon (GAR-9) next to a YF-12A with it’s missile bays open. The SR carried sensor pallets where the missile bays are on the the YF.So, the YF-12A would’ve done very well shooting down relatively unmaneuverable Soviet bombers, but it would’ve done horribly if it actually had to go up against a real fighter.

Lockheed’s YF-12A Interceptor: First flew back in 1964. Sister ship to the famed SR-71A BlackBird it was as fast as the reconnaissance version only it was armed to 8 AIM-47 air-to-air missiles all internally.A number of engineers who worked on both birds said that the wrong aircraft went into production. But the then Secretary of Defense, Robert S. McNamara cancelled the YF-12A stating that it was so advanced as to not have a target worthy for it!It was a aircraft that could’ve been guarding the Continental US and most of North America right now effectively but never saw production and only a couple of prototypes were produced.

“Could the SR-71 Blackbird really outrun its own missiles?”Okay, history lesson time.Despite what all the other answers are saying about the SR-71 never carrying missiles, this isn’t strictly true. The SR-71 was the final configuration in a family of very similar airplanes, all of which trace their lineage back to the A-12 Oxcart.The A-12 was designed as replacement for the U-2, and was basically the CIA’s single occupant version of the SR-71 (which is flown strictly by the US Air Force.) The airframe and performance specifications are nearly identical. While it is true that the SR-71 doesn’t carry any armament, the A-12 did have a payload capacity of 2,500 lbs, (ostensibly for reconnaissance equipment, but we’ll get to that.) And, importantly, of the initial production run of eighteen airframes, three were configured as interceptors, sent to the Air Force for testing, and designated YF-12A.Interceptors carry missiles, so the three YF-12As had their reconnaissance bays re-worked to store air-to-air missiles and a fire control system. This means that there was indeed a platform in the SR-71 family that was capable of firing missiles, and that capacity not only existed as a prototype, but had successful operational testing to the point where a fleet of 93 were ordered by the US Air Force as continental defense interceptors, (basically to shoot down nuclear bombers far before they could get state side.) Vietnam was well underway at this time, so the Secretary of Defense, Robert McNamara, put the project on ice and it never materialized beyond the three YF-12A prototypes.But the YF-12A is pretty close to a dead ringer for the SR-71, and it did have missiles that were specifically designed for it as a platform. So if we’re willing to gloss “SR-71” in the original question as “YF-12A,” we can then ask, “could the YF-12A really outrun its own missiles?”The answer to that is, “no.” The YF-12A carried the AIM-47 Falcon long range air-to-air missile, which was a direct precursor to the AIM-54 Phoenix which was deployed on the F-14 Tomcats in the US Navy in an actual interceptor capacity. The AIM-54 had an actual production run, so it’s specifications are fairly standardized. The important point here being that the AIM-54 had a range of 190 km and a speed of Mach 5 (faster than nearly any bullets.) The SR-71 was renowned for being able to speed away from surface launched missiles, and effectively run them out of fuel, but the scenario is a little different when you consider air-launched long range interceptor missiles.I point all this out because the AIM-47 and the YF-12A were never actively in service, so the specifications for the AIM-47 never fully materialized. On paper it was supposed to have a top speed of Mach 6, but changing fuel types reduced that to Mach 4. The effective rated top speed for the YF-12A (and thus the Blackbird family in general) is Mach 3.35. So a YF-12A firing it’s own missile, could not keep up with it, even with the slower speed of the AIM-47.But because the A-12/YF-12A developed into the SR-71, and the AIM-47 developed into the AIM-54, we can ask another question, which is, “could the SR-71 outrun the AIM-54, which is the grandchild of the missile it almost carried, if the AIM-54 was fired at the SR-71 from a nominal engagement range?”This gets really interesting because we can now formulate this question in terms of equipment and practice that actually exist. Basically, supposing for whatever reason an SR-71 is spying on someone who has F-14s with AIM-54s, could the F-14 sortie and actually take down the SR-71 with its long range air-to-air missile? (This scenario has legitimate merit, by the way, because we haven’t replaced the SR-71 with any other spy plane, so if we had to use something for reconnaissance other than satellites, that would be it, and also, Iran has a bunch of F-14s from when they were allies with the US. So an American overflight of Iran with an SR-71 that gets intercepted by a F-14 with AIM-54s, while profoundly unlikely to ever happen, is not outside the realm of real possibility.)The AIM-54 has a minimum launch distance of 3.7 km, and the F-14’s radar has a maximum range of 370 km. Since the AIM-54’s maximum range is 190 km, we’ll suppose an easy number that’s closer than half of that range but still well BVR for the Tomcat. So let’s imagine the F-14 picks up the SR-71 at 50 km away, the SR-71 is speeding directly away from the F-14, (so we don’t have to negotiate maneuvering with our math,) and the F-14 fires the AIM-54. We’re assuming the AIM-54 stays at Mach 5 for the entire flight, (apparently it will fly higher in altitude and then use gravity as an assist during the later portions of the flight, but for the sake of argument we’ll normalize this to just a flat velocity,) which works out to be 1.715 km/s. The Blackbird, with a 50 km head start is going Mach 3.35, or roughly 1.15 km/s. So now we just have to figure out if the Blackbird can make it another 140 km before the missile catches up.It takes the SR-71 a total of 121.74 seconds to get to 190 km away from the launching point, given the 50 km head start. It takes the AIM-54 a total of 110.79 seconds to reach the same distance, at which point we presume it runs out of fuel or kinetic energy. If I wanted to get really fussy about the math I could tell you at what distance the missile hits, or even at what range would the SR-71 would already have to be in order for the missile to not catch up, but I believe those would be related rates problems and I don’t have the tools to casually throw that together for a Quora answer.The relevant point here though, is that it’s close. In this scenario the Blackbird gets hit, but nearly right up at the end of the missile’s range. If you fired from a little further out, the Blackbird would get away. In actual combat conditions, with a little bit of maneuvering, even though the missile catches up, it might not actually get on target with the fuel it has left. Also, when the missile is already going Mach 5 and the plane it’s trying to hit is going a good fraction of that speed as well, the fragmentation/blast-wave/continuous-rod-circle might hit too much air resistance to cause meaningful damage. Interceptor missiles aren’t actually meant to shoot down high-speed interceptors, they’re meant to shoot down bombers, which go a good bit slower and don’t have all those Mach numbers getting in the way of whatever you want to do to them.So on the whole? I’d say it’s probably a wash. The SR-71, in the right conditions, might be able to out sprint the stamina of an interceptor missile, and intercepting at that speed is probably dicey anyway, but the missile definitely goes faster, if that’s the overall question you’re looking to have answered.