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)
 
Guys, check your Math:

1791309315607.png

Stall spped at V1 = V0 x Sqrt(g-load)

With a 310kt stall speed at high altitude, the margins for a macho 2g pullup are... t(h)in foiled ;)
 
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
 

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