Lockheed SR-71 / YF-12 Blackbird

Could it be that the SR-72 is needed to test new 6th generation fighter engines? Since it can fly faster and higher than anything in the inventory?
 
Hydroman said:
I briefly worked with the late and very nice Joe Vida at the B-2 CTF in the 90s and who was apparently the high-time RSO in the SR community. He did tell me a few great stories regarding North Korea missions. In general, it does seem the SR maxed out at almost M3.5.

He did tell me a story about returning from a mission and they were to land at McGuire AFB, they contacted the tower related to landing, the young tower Sgt asked their position and Joe stated they were just coming across the west coast of Africa at 90kft, M3.35. I thought I would share this, the Sgt had a moment of silence as well then responded.
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According to an issue of "Wings of Fame" The A-12 was able to reach Mach 3.6 and 97,000 feet in early testing. I'm aware of the limits frequently mentioned for suspecting that's impossible (TET, shock angle, etc.) but thought I'd pass it along. Mary Shaefer, who was the head of the flight dynamics portion of the NASA Blackbird effort, didn't dismiss it but said the two figures might not have been on the same flight. (On USENET back in the day.)
 
Sferrin said:
According to an issue of "Wings of Fame" The A-12 was able to reach Mach 3.6 and 97,000 feet in early testing. I'm aware of the limits frequently mentioned for suspecting that's impossible (TET, shock angle, etc.) but thought I'd pass it along. Mary Shaefer, who was the head of the flight dynamics portion of the NASA Blackbird effort, didn't dismiss it but said the two figures might not have been on the same flight. (On USENET back in the day.)
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Thanks for the info, I knew the A-12 had much higher performance than the SR.
 
The above discussion got me looking at the NRO and CIA declassified libraries and I've found a little gem of a document, related to A-12 vs SR-71 performances, the year their fates crossed: 1966.
 

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Sferrin said:
According to an issue of "Wings of Fame" The A-12 was able to reach Mach 3.6 and 97,000 feet in early testing. I'm aware of the limits frequently mentioned for suspecting that's impossible (TET, shock angle, etc.) but thought I'd pass it along. Mary Shaefer, who was the head of the flight dynamics portion of the NASA Blackbird effort, didn't dismiss it but said the two figures might not have been on the same flight. (On USENET back in the day.)
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The Blackbird achieved its maximum speed in 1976, when it set a speed record. The coldest day was chosen, and the aircraft had minimal fuel. This speed was 3,529.56 km/h or Mach 3.3 or 2,194 mph. They wanted to reach 2,200 mph, but they fell short by 6 mph. The SR‑71 pilot himself said so. In various dubious sources, we read about Mach 3.5, Mach 3.6, Mach 4, Mach 4.5 and so on. But there is no evidence to support this. The A‑12 is lighter than the SR‑71 and therefore can fly 3000 feet higher, but it practically cannot fly faster. They have the same thrust, dimensions, and aerodynamic shape. I saw a page from a NASA document where the difference in maximum speed between the A‑12 and the SR‑71 was stated as “up to 20 (twenty, not two hundred! ) mph.”

I think that saying “in fact, the SR‑71 or the A‑12 sometimes flew faster than that SR‑71, which set the record in 1976, but this is still classified” is the same as saying “in fact, the F‑15 can accelerate and climb faster than the F-15 Streak Eagle, but this is classified.”
 
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A12 said:
The Blackbird achieved its maximum speed in 1976, when it set a speed record. The coldest day was chosen, and the aircraft had minimal fuel. This speed was 3,529.56 km/h or Mach 3.3 or 2,194 mph. They wanted to reach 2,200 mph, but they fell short by 6 mph. The SR‑71 pilot himself said so. In various dubious sources, we read about Mach 3.5, Mach 3.6, Mach 4, Mach 4.5 and so on. But there is no evidence to support this. The A‑12 is lighter than the SR‑71 and therefore can fly 3000 feet higher, but it practically cannot fly faster. They have the same thrust, dimensions, and aerodynamic shape. I saw a page from a NASA document where the difference in maximum speed between the A‑12 and the SR‑71 was stated as “up to 20 (twenty, not two hundred! ) mph.”

I think that saying “in fact, the SR‑71 or the A‑12 sometimes flew faster than that SR‑71, which set the record in 1976, but this is still classified” is the same as saying “in fact, the F‑15 can accelerate and climb faster than the F-15 Streak Eagle, but this is classified.”
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As I said, this was in testing, not an official record-setting flight. Also, there was a stretch in the last record-setting flight where they did reach 2,242 mph.
 
Hydroman said:
Thanks for the info, I knew the A-12 had much higher performance than the SR.
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I put this information together back around 2007....


The Blackbirds were optimized to cruise at Mach 3.2, subject to compressor inlet temperature limits.

These are fastest known Blackbird flights:

YF-12A (60-6936) – Mach 3.14 (2,070 mph), USAF, official, 1 May 1965

SR-71B (61-7956) – Mach 3.27 (2,158 mph), NASA, unofficial, 14 December 1995 and 4 March 1997

A-12 (60-6928) – Mach 3.29 (2,171 mph), CIA, unofficial, 8 May 1965

SR-71A (61-7972) – Mach 3.32 (2,193 mph), USAF, official, 27 July 1976



The Blackbirds were designed to fly as high as 90,000 feet but typically operated between 70,000 and 85,000 feet based on a combination of fuel, sensor payload, and mission requirements.


Highest known flights:

YF-12A (60-6936) – 80,257 feet, USAF, official, 1 May 1965

SR-71B (61-7956) – 84,700 feet, NASA, unofficial, 18 October 1994

SR-71A (61-7972) – 85,068 feet, USAF, official, 27 July 1976

SR-71A (61-7953) – 86,700 feet, USAF, unofficial, circa 1968 (based on test report)

SR-71A (61-7953) – 89,650 feet, USAF, unofficial, circa 1968 (anecdotal, via Mervin Evenson)

A-12 (60-6932) – 90,000 feet, CIA, unofficial, 14 August 1965 (from declassified CIA reports)
 
I wonder if the YF-12A or SR-71A could've reached 100,000ft in height?
 
Based on the normal takeoff / landing speeds in the 200-250 KIAS speeds, I doubt 310 is the high altitude / high Mach stall speed. However, it is probably a high Mach directional stability limitation. You might be able to do the 2g pull, then ride the 310 line up and over an altitude of 90K+. But loss of control due to a yaw departure is just a catastrophic as a aero stall at those Mach numbers.
 
If the SR‑71 or the A‑12 could have performed a zoom climb to reach an altitude of more than 100,000 feet, the test pilots would certainly have done so during test program. Because this is a very important capability. If they didn’t do it, it means it was dangerous for this plane. In 1966, the SR-71 (M-21) launched the D‑21 drone, but the D-21 slammed down on the SR-71 causing it to pitch up. The air pressure immediately ripped the fuselage forebody. Although the air pressure at an altitude of 80,000 feet was actually very low — even at Mach 3.2, it was only 350–400 KEAS.
 
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A12 said:
If the SR‑71 or the A‑12 could have performed a zoom climb to reach an altitude of more than 100,000 feet, the test pilots would certainly have done so during test program. Because this is a very important capability. If they didn’t do it, it means it was dangerous for this plane.
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I don't disagree that this type of maneuver could be risky. But I do disagree with the statement "this is a very important capability". For the A-12 / SR-71 reconnaissance mission, I would argue that this capability is completely unnecessary, thus not worth risk in demonstrating with a rare national security asset operating at the edge of its extreme flight envelope.

If we were talking about the F-12 interceptor mission, the discussion about a zoom climb capability might be different
 
In 1975, Lockheed attempted to determine the feasibility of extending the Blackbird’s speed and altitude capabilities. The results of several studies concluded the airplane’s maximum speed limit could be extended to Mach 3.5 for short periods of time. The only structural limit to speeds above Mach 3.5 was a KEAS limit of 420, set by inlet duct pressures and temperatures that exceeded acceptable values. Limited inlet-capture area and excessive engine compressor inlet temperatures also limited operations at higher Mach numbers.

Similar studies addressed the possibility of achieving flight in the SR-71 well above 85,000 feet. Results indicated the SR-71 could briefly reach an altitude of about 95,000 feet in a zoom climb profile. The proposed mission could have been accomplished with an airplane at a gross weight of 85,000 pounds. According to the proposed flight profile, the pilot would accelerate from Mach 3.2 to Mach 3.5 at an altitude of 80,000 feet, then zoom to 95,000 feet as speed decreased to normal cruise Mach numbers. The airplane would subsequently settle back down to an altitude of about 84,000 feet. Sustained flight at altitudes above 85,000 feet was limited by wing surface area and engine thrust capabilities.



Scott Kenny said:
No, I think a Blackbird could zoom climb up there. It won't stay up there, but a 2gee pull up at Mach 3.2 should do the job to get you there for a heartbeat.

Probably fall out of the sky to about 30,000ft to restart the engines, however.
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F119Doctor said:
I don't disagree that this type of maneuver could be risky. But I do disagree with the statement "this is a very important capability". For the A-12 / SR-71 reconnaissance mission, I would argue that this capability is completely unnecessary, thus not worth risk in demonstrating with a rare national security asset operating at the edge of its extreme flight envelope.

If we were talking about the F-12 interceptor mission, the discussion about a zoom climb capability might be different
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Exactly what I was thinking.

The F-12 would likely need to do such a zoom climb, but not the recon Blackbirds.
 
NMaude said:
What about the cancelled B-12 variant? Would it have used a zoom-climb to launch an AGM-69A SRAM for a long-range shot?
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I don't believe so. The graphs from that study imply steady-state flight, and launching from M3 and 85kft gave a ~500nmi down range and ~250nmi cross range.
 
Scott Kenny said:
I don't believe so. The graphs from that study imply steady-state flight, and launching from M3 and 85kft gave a ~500nmi down range and ~250nmi cross range.
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With performance like that it's surprising and disappointing that the B-12A never went into production, it would've given the Soviets a major case of heartburn.
 
Whisperstream said:
In 1975, Lockheed attempted to determine the feasibility of extending the Blackbird’s speed and altitude capabilities. The results of several studies concluded the airplane’s maximum speed limit could be extended to Mach 3.5 for short periods of time. The only structural limit to speeds above Mach 3.5 was a KEAS limit of 420, set by inlet duct pressures and temperatures that exceeded acceptable values. Limited inlet-capture area and excessive engine compressor inlet temperatures also limited operations at higher Mach numbers.
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Are you sure it was Lockheed and not some other organization? Not everything written on paper is trustworthy. An example of the greatly inflated projected performance of the SR‑71 was already given earlier.

Actually the Blackbird could easily reach a speed of Mach 3. Higher speeds—up to Mach 3.3—were achievable under favorable conditions, i.e., in the cold stratosphere—that is, when it was flying over Vietnam or over the Middle East. There, it routinely reached Mach 3.1–3.2 and altitude up to 24 km. When the SR-71 was flying near Murmansk (in the north of the USSR), its speed ranged from 2,900 to 3,200 km/h. The altitude is up to 22 km. These are the results of many years of observations by the Soviet air defense system. Although one retired pilot used to tell stories about Mach 3.49 during flights along the northern border of the USSR.

I read a discussion on a forum where there was one person from the SR‑71 technical team. In their department, they received records of every flight. He said that over many years he had never seen anything higher than Mach 3.2, and all the stories about Mach 3.5 and the like are just pilots’ fantasies.
 
A12 said:
I read a discussion on a forum where there was one person from the SR‑71 technical team. In their department, they received records of every flight. He said that over many years he had never seen anything higher than Mach 3.2, and all the stories about Mach 3.5 and the like are just pilots’ fantasies.
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And did that list include all A-12 early test flights or just SR-71? The notion that it could cruise at Mach 3.2-3.3 but would explode into fiery bits at Mach 3.4 is laughable.
 
Scott Kenny said:
Really expensive way to deliver 3-4 SRAMs, though.
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Not when you consider that they had like a 500nm range when launched from an SR-71Bx.

Sferrin said:
And did that list include all A-12 early test flights or just SR-71? The notion that it could cruise at Mach 3.2-3.3 but would explode into fiery bits at Mach 3.4 is laughable.
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According to a pilot one exceeded M3.5 running away from a SA-5 above Libya in '86. Inlet duct temperatures and engine longevity probably weren't his primary concerns at the time.
 
A12 said:
Are you sure it was Lockheed and not some other organization? Not everything written on paper is trustworthy. An example of the greatly inflated projected performance of the SR‑71 was already given earlier.
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Sources:

Determination of Extended Speed Thermodynamic Effects, Lockheed Report No. SP-4347, March 1975.

Determination of Extended Speed Aerodynamic Effects, Lockheed Report No. SP-4399, August 1975.

Lockheed SR-71 Supersonic/Hypersonic Research Facility Researcher’s Handbook, Volume 2, Technical Description, Lockheed Advanced Development Company, Palmdale, Calif., 1995.
 
Forest Green said:
According to a pilot one exceeded M3.5 running away from a SA-5 above Libya in '86. Inlet duct temperatures and engine longevity probably weren't his primary concerns at the time.
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Yes, but 20 years later, the Soviet report on these events was declassified and published (the Soviets had all the information about the air defense situation). In reality, the SR‑71’s speed was not Mach 3.5 but Mach 3.15. And the SA‑5 was not used against the SR‑71 at all. Three SA-2 missiles were launched, but they failed to shoot it down. Brian Shul (the pilot of that same SR-71) is a fabricator who had no idea he could be exposed a few years later.
 
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Forest Green said:
A Soviet document may not be the most trustworthy source, probably why it's omitted from the Wikipedia page. Doesn't really make sense to go slower than cruise speed to evade a missile.
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Blackbird crews didn't rely on speed to evade SAMs. The Blackbird's defensive avionics suite did a lot of heavy lifting during those encounters.
 
Ballistic climbs over 100,000 ft should be well within the Blackbird's capabilities, since lesser aircraft can do it. However, the real issue are maintaining control at those altitudes and the ability to restart both engines in-flight while coming down. Did the Blackbird have an APU that could operate at that altitude? Could it maintain control at slower speeds while the engines were flamed out? If it can't then kinematic performance (which it does have) does not matter.
 
With the current state of play I wonder if the truth will come out while many of us are vertical enough to appreciate it.
 
Desertfox said:
Ballistic climbs over 100,000 ft should be well within the Blackbird's capabilities, since lesser aircraft can do it. However, the real issue are maintaining control at those altitudes and the ability to restart both engines in-flight while coming down. Did the Blackbird have an APU that could operate at that altitude? Could it maintain control at slower speeds while the engines were flamed out? If it can't then kinematic performance (which it does have) does not matter.
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While it might have been technically possible to zoom an SR-71 to altitudes above 100,000 feet, there would never be a practical reason to do so. It would also be a recipe for destruction of the aircraft and loss of the crew. Even with the addition of reaction control thrusters I would expect the Blackbird to suffer complete loss of control and, eventually, catastrophic structural failure.
 

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