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Could the SR-71 Blackbird really outrun its own missiles? Great Article!

dougcjohn

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Found this a great read... I personally learned something that I wasn't aware.

Question was posted: Could the SR-71 Blackbird really outrun its own missiles?
Every reply was blasted stating the SR-71 didn't carry missiles... til an old Air Force Pilot with great history added to the story.

Pasted in article in case the URL Link goes offline, the paste didn't appear to have the whole path.

Article by Matthew Ramada,
Retired US Air Force command pilot; Current aviation safety contractor for the government;
Chair of… and Damien Leimbach, USAF avionics technician, U-2s

“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.
 

dougcjohn

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Discussion on other thread... that slipped into historical behavioral and cause & effect of involvement in warfare. This is one example of all the development that was secretly being developed & tested for purposes of warfare advantages in the name of defense.

Still this is a fascinating read; enjoyable exploring historical events that transpired within my own lifetime that went unnoticed.
 
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R.Perry

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I only see one problem with his engagement, first you would have needed to get the F14 within 50 km of the SR71 and at altitude. The SR71 notoriously flew above 80,000 feet. Once detected you would need to get the F14 in range, and that could be very difficult. Example you detect the SR71 entering your airspace at 80k feet at 150 km traveling M3.5. You scramble two F14s with AIM 54 missles, by the time they get off the deck and to at altitude the SR71 most likely has a 100 to 150 km lead and no F14 is going to catch it, actually no aircraft could. That is why it was so successful, it had a very low radar signature so by the time it was detected it was out of range of SAM's and any interceptor aircraft.
 

dougcjohn

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I only see one problem with his engagement, first you would have needed to get the F14 within 50 km of the SR71 and at altitude. The SR71 notoriously flew above 80,000 feet. Once detected you would need to get the F14 in range, and that could be very difficult. Example you detect the SR71 entering your airspace at 80k feet at 150 km traveling M3.5. You scramble two F14s with AIM 54 missles, by the time they get off the deck and to at altitude the SR71 most likely has a 100 to 150 km lead and no F14 is going to catch it, actually no aircraft could. That is why it was so successful, it had a very low radar signature so by the time it was detected it was out of range of SAM's and any interceptor aircraft.
If on alert ready pad, you’re correct... be out of range before altitude. In his example, he’s greatly simplified to the point where both are at cruise speed, same vector and 50km apart.

In that situation, 50km is minimal margins... 70km it’ll tap AIM54 fuel before catch.

I wasn’t aware of the YF-12A being a SR71 clone.

Side tid-bit, was a good show 1-3 seasons in ‘70’s focused around the SR71 and the building events of late ‘50’s in VietNam. Good show, enjoyed the Airbase and cultural lifestyle.
 

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The YF-12 was not a “clone” of the SR-71. If anything, the SR-71 was an upgraded “clone” of the YF-12.

As for out running its own missiles, I’m going to take a leap here and say it probably could. Two reasons for that leap; (1) The top speed of the SR-71 is still classified so the max speed is not known to anyone other than those that worked directly with it.

(2) I was a flight instructor back in 1989-1992 and one of my “students” was an Air Force Major. He flew the SR-71. Many may not be aware that military pilots are generally not FAA certified pilots. Their pilot credentials are only valid when flying military aircraft on military missions. Because of that most of them enroll in civilian pilot courses at some point in their military careers, usually just before separating from the military.

During the course of his civilian flight instruction I tried to find out how fast the -71 would go. The usual and disappointing response of “that’s classified” was received but an intriguing tidbit of “a lot faster than people know” was obtained. It was so fast a 360* standard rate turn would encompass almost half the geographical U.S.

Over time what I’ve learned about the SR-71 has it more of a maneuverable space craft than an airplane. That it was “decommissioned” strongly suggests the Air Force developed something that flies faster and higher than the -71. The military is not noted for getting rid of something that works well and having nothing to fill the void. They even still use the M2 on the battlefield. The cartridge works so well Barrett developed a couple long range sniper rifles to make use of it.
 
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dougcjohn

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The YF-12 was not a “clone” of the SR-71. If anything, the SR-71 was an upgraded “clone” of the YF-12.

As for out running its own missiles, I’m going to take a leap here and say it probably could. Two reasons for that leap; (1) The top speed of the SR-71 is still classified so the max speed is not known to anyone other than those that worked directly with it.

(2) I was a flight instructor back in 1989-1992 and one of my “students” was an Air Force Major. He flew the SR-71. Many may not be aware that military pilots are generally not FAA certified pilots. Their pilot credentials are only valid when flying military aircraft on military missions. Because of that most of them enroll in civilian pilot courses at some point in their military careers, usually just before separating from the military.

During the course of his civilian flight instruction I tried to find out how fast the -71 would go. The usual and disappointing response of “that’s classified” was received but an intriguing tidbit of “a lot faster than people know” was obtained. It was so fast a 360* standard rate turn would encompass almost half the geographical U.S.

Over time what I’ve learned about the SR-71 has it more of a maneuverable space craft than an airplane. That it was “decommissioned” strongly suggests the Air Force developed something that flies faster and higher than the -71. The military is not noted for getting rid of something that works well and having nothing to fill the void. They even still use the M2 on the battlefield. The cartridge works so well Barrett developed a couple long range sniper rifles to make use of it.
Interesting angle on it... the author from his credentials and limited share... sounds like he was involved and intimately involved in the U2 projects, and possibly one of the pilots in the testing.

He makes the statement, they had the recon bays reconfigured for missiles... that sounds like SR71 being reconfigured for a small number of YF12. Although I'd agree, what cycles to what, and what next great idea spawned another... the final SR71 or YF12 could very well have fed the other. Back in the 50's the rate of development and methodologies applied from table napkin chatter by a team of Engineers to the design tables was rapid... it was a period of extreme creativity and science. Many things feed and received mods from other discoveries. The powerplants were another amazing group of engineering designers. They guys were the "root" core of modern day avionics.

All the stories involved probably have merit along the history trail... and an amazing trail it is too.
 
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dougcjohn

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Just for giggles, the fastest "recorded" manned airplane occurred with the X-15.
Rocket Power... what he’d get again just on drop ignition... 6-8Gs... scary craft for the Test Pilots. The X15 and it's siblings introduced and important period!
 
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dougcjohn

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Just for giggles, the fastest "recorded" manned airplane occurred with the X-15.
Lol... and I never quite understood how, but didn't the X15 get used in the movie Creature from the Black Lagoon... something about attracting the Aliens. I may be mixing a few oldies too.
 
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PatR

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Don’t remember that one for the X-15. I do recall it was a terrible movie for its special effects. The costume designer should have been black balled.
 

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Just for giggles, the fastest "recorded" manned airplane occurred with the X-15.
Come on Pat, you are a lot smarter than that. The implication that the X-15 has was the fastest worked in the 1960's, I know you highlighted recorded. One thing us ASW guys had was some pretty neat stuff for tracking objects. How is stealth aircraft tracked, heat signature, not radar. Now I don't know how fast the SR71 will travel but the M3.5 that I mentioned is most likely a cruise speed, top speed, as you said is classified.

Ever hear of Aurora?
 
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PatR

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Most certainly, although I doubt that name is one actually assigned to such an aircraft.

I stand by my X-15 speed record reference because of using the word “recorded”. Precisely why the word was chosen as a qualifier. We can look it up and find it’s still factual. The SR-71 holds the speed record for the fastest “air breathing” aircraft. I am absolutely certain we have flown much faster.

As for the -71’s public speed, I would not be surprised if that wasn’t the best “loiter” speed. That beast doesn’t have jet engines, it has modified rocket engines.

Ever see videos showing the -71’s shock diamonds in the thrust plume under full thrust? Absolutely amazing.
 
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R.Perry

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We tracked a SR71 from the Aleutians to it's approach to Beale, the speed was incredible. Only reason we could track him was IFF. It was a truly amazing aircraft, if you want to call it that. When you have a bird that can operate in the Stratosphere and get close to the Mesosphere you are getting close becoming an astronaut. I don't have a clue as to the SR71 ceiling, but it is up there a ways.
 
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