Soviet air defences and the SR-71

[CNH]

Apparently the SR 71 was able to evade Soviet air defences simply because it travelled too fast.

The reason I am interested in this is that there were proposals in 1960/61 for a British ramjet missile (OR 1182) which would fly at speeds in excess of M = 2 and at high altitude. A report was produced by the RRE (Royal Radar Establishment) which said that such a missile would be vulnerable to the Soviet air defences. I have the feeling that the report was written in such a way as to discredit the idea of using a ramjet missile. A couple of questions then.

Firstly, if the SR 71 was able to evade the defences so easily, surely a ramjet missile would have a fairly good chance of also evading the defences.

Secondly, to mirror the threat so speak, would Bloodhound have been capable of intercepting a Mach 2 missile at altitude?

 

[DrRansom]

The S-71 was vulnerable to air defenses, the route planners avoided over flying known SAM sites.

 

[CNH]

"2) Based on evidence available today would such a weapon have been vulnerable to Soviet Air Defences...?"

Not quite.We knew the capabilities of Bloodhound in 1960; the question is whether it too could intercept a M2 target. If it couldn't, why assume the Soviets could?

 

[Airplane]

My friend told me about sitting on the ramp in his F-104 listening to the tower communicating with a Blackbird (his only encounter with one which tells you how rare it was even in the community) and one of the things he was surprised to hear was the blackbird pilot say, "Descending through one hundred thousand." I want to say that was his Alaska deployment and the Habu was coming from the direction of Russia. Perhaps that has some bearing on the lack of shoot downs. You kids today think they're inventing new stuff! It's all been done before.

 

[CJGibson]

I think UK air defence was more about destroying the carrier aircraft rather than the M3 ASM. All superseded by the ballistic missile. Command-Guided Bloodhound might have had a chance if launched in time, but I think the dead time would be too much. See Battle Flight. I know a guy who knows a guy, so will ask.

Chris.

 

[FighterJock]

I thought I heard year's ago that one MiG-31 Foxhound had actually locked onto the SR-71 but the pilot did not fire the missile, was there any truth in that rumor?

 

[red admiral]

The S-71 was vulnerable to air defenses, the route planners avoided over flying known SAM sites.

Indeed, the key difference is in CONOPs as a SR-71 will avoid overflight and not descend. Hence most SAM shots end up being tail chases and there is a limited engagement window. With an air-to-surface missile it is heading towards the SAM site (assuming colocated with target) and slows down as it descends to lower altitude. The main challenge then becomes fusing for a high closing speed.

Its a very different situation to shooting at a high altitude SR-71 that is trying to avoid the SAM.

The same arguments apply to today's hypersonic weapon projects...

 

[steelpillow]

"In excess of Mach 2" is barely relevant here, the Habu was in a totally different performance class - "in excess of Mach 3". For its first few flights, it was theoretically able to outrun the SAMs of the day but the theory was untested. Missions avoided SAM sites as far as possible besides flying ridiculously high. A crew member on one early flight recalls that it was detected and a SAM launched. The Habu lit out for home, the Machmeter going uber-classified and the SAM failing to stay the chase. The pilot had to ease back on the throttle before his ship melted.

British ramjets developed ten years and more earlier, and the missiles which they drove, maxed out at rather lower speeds. But as it was more or less a head-on interception, it was the climb to altitude that mattered. And here, a Mach 2 interception at altitude would have depended more on the radar early-warning system than on ultimate performance. Probably an easy kill unless hysteresis (delay) in the semi-active radar homing or proximity fusing system was a problem, though obviously the altitude one has in mind would be a bit important too.

Likewise, a Soviet SAM that could shake up a Blackbird crew above 100,000 ft would make easy meat of a Mach 2 cruiser.

 

[CNH]

these are some excerpts from a report produced by CGWL in December 1960. Sorry these go on for some length:

The advent of C. W. radar techniques and of semi--active C. W. homing systems, has opened up a major breakthrough in defence against low-level attack.
Given nuclear warheads, a very effective defence for cities by heavy S.A.G.W. could be provided against medium or high attack by both manned winged aircraft and undermanned winged guided weapons. The chance of a kill per S.A.G.W. fired would be of the order of 80 percent against such targets.
The same heavy S.A.G.W. system deployed for the paragraph above but using H.E. warheads, could also provide a good defence against both manned and unmanned low-level attack, if the acquisition and TIR radars are sited either on buildings or towers 100 ft. above the ground.
A light S.A.G.W. system using semi--active C. W. homing and H. E. warheads are mounted on 50-100 ft. towers or buildings could provide a good defence against both manned and unmanned low-level attack. The chance of a kill per S.A.G.W. fired would be of the order of 50 percent against manned aircraft and 30 percent against unmanned guided missiles.
The cost of missiles, launches, and their radars to give this gave the defence to a city of 1M inhabitants, but not including supporting costs such as crew accommodation, roads, power, etc, but not including the national early warning system, would be of the order of £7-12M per city at UK prices. With the supporting services this might be increased to £10-15M. To provide this for a total of, say, 50 Russian cities so located as to be within range of this type of attack would cost £500-£750M.
…
Raising the speed of the manned aircraft to supersonic figures - say Mach 2 - would give it very little extra protection against S.A.G.W. Defence, except in the case of attack against Coastal towns where early warning is difficult.

 

[Zoo Tycoon]

In the late seventies, to mid eighties Concorde was used as a real Mach 2 target for UK air defence. There's a well reported account of a Lightning interception but the full story behind these trials has yet to be told. I was told by a former member of the flight test crew that there were around twenty flights over quite a few years. Many of the early flights were done as a genuine unexpected Mach 2 intruder, and a good number of these got zero response from UK air defence. Although an interception should have been possible the flights illustrated the shear difficulty associated with actually doing this. Several quite fundamental rethinks later a single successful interception was achieved I think in 85. What it took to do this is still unclear and probably will remain so.

 

[CJGibson]

"The main challenge then becomes fusing for a high closing speed."

One reason for nuclear warheads. Probably the reason.

Chris

 

[sienar]

How much did the SR-71s low RCS actually help?

 

[Zoo Tycoon]

A quick search of the web illustrates the difficulties of a man aircraft interception of the Mach 2 Concorde using an F4 Phantom which I assume failed. The pilot of the F4 remarks that he had just "one whole second" opportunity in the entire interception profile in which to lock up his radar. Presumably this is due to what's left from initial warnings, scramble, climb, manoeuvre, and close. In another he noted that following one turn he made the target was 150 miles further away than he expected.

Now if you have a Mach 3 SR71 to catch with inherently only 2/3 of the action time due to speed and something less again due to a lower detection range from the reduced radar signature, this problem is changing from very difficult to near impossible.

Hence bring on the SAMs, the largest perimeter acquisition range you can achieve, head on collision course all the way, minimal time to launch, massive climb rate and this probably forms the basic operational requirements for the S200 - 400 systems. Nuclear warhead because your only going to get one chance to get this right.

 

[DrRansom]

"The main challenge then becomes fusing for a high closing speed."

One reason for nuclear warheads. Probably the reason.

Chris

Can you explain further? What is the challenge with high-speed fusing?

I thought that nuclear warheads were for reducing accuracy requirements for missile end-game maneuvers, not for fusing.

 

[steelpillow]

Can you explain further? What is the challenge with high-speed fusing?

I thought that nuclear warheads were for reducing accuracy requirements for missile end-game maneuvers, not for fusing.

In a word, timing. At high speeds, a direct hit is rare - one or other machine will be first the point where their paths cross and a fraction of a second will represent more than the length of the craft. Adjusting the speed or direction can never be precise enough to ensure exact timing, so missiles use proximity fuses, which trigger once you get close enough for the blast of a near-miss to knock out the enemy. Well, that's OK for subsonic, but at Mach 2 plus the slightest delay in the complex distance-sensitive fusing system means you will miss your chance. The only hope is to up your explosive power, and the only way to do that without weighing several tons is to go nuclear.

 

[CNH]

Although it's surprising how small the 'kill radius' is for say a 5kT warhead.

 

[DrRansom]

Now that you put it that way, I get it. A missile closing speed vs a supersonic target can be 1000 m/s or more. A small time delay would mean a major difference in warhead detonation location.

 

[CJGibson]

Well, you can read all about nuclear warheads vs aircraft in Battle Flight.

Chris

 

[phil gollin]

.

Simple question - did the SR-71 ever actually overfly the Soviet Union (rather than along its borders) ?

 

[steelpillow]

Simple question - did the SR-71 ever actually overfly the Soviet Union (rather than along its borders) ?

Yes indeed. That's why they launched a SAM at it.

 

[TomS]

Simple question - did the SR-71 ever actually overfly the Soviet Union (rather than along its borders) ?

Yes indeed. That's why they launched a SAM at it.

Source?

I ask because the general consensus (including some explicit statements buy the US government) is that the Blackbirds (SR-71 and A-12) never actually flew missions over the Soviet Union, just around the edges. It did fly over other places (Vietnam, Laos, etc.) where the Soviets could have taken shots at it, but not over the Soviet Union proper.

 

[steelpillow]

Simple question - did the SR-71 ever actually overfly the Soviet Union (rather than along its borders) ?

Yes indeed. That's why they launched a SAM at it.

Source?

I ask because the general consensus (including some explicit statements buy the US government) is that the Blackbirds (SR-71 and A-12) never actually flew missions over the Soviet Union, just around the edges. It did fly over other places (Vietnam, Laos, etc.) where the Soviets could have taken shots at it, but not over the Soviet Union proper.

It was and probably still is US government policy to deny that such Habu overflights ever took place, they are not a reliable source. Remember the U-2 and Gary Powers. But I have to say I cannot recall the journal I read the account in and it was a while ago, so I may be wrong about the location.

 

[flanker]

Eh, Libya definitely fired at them and North Korea too i believe, but never heard of such thing for Soviet Union. Reading tales from MiG-31 pilots SR-71's were very careful to only fly along the borders.

 

[kaiserd]

Eh, Libya definitely fired at them and North Korea too i believe, but never heard of such thing for Soviet Union. Reading tales from MiG-31 pilots SR-71's were very careful to only fly along the borders.

It would have been and would be massive news if a Blackbird ever more than brushed soviet airspace; as such it appears far more likely it never happened.
In terms of claimed effectiveness of MIG31 and other Soviet systems against the SR71 it's difficult to know exactly how effective they would actualy have been (and difficult to get unbiased answers given the national & professional pride involved in both sides)
However given that SR71 bombers (and of course the B70) were never fielded it would suggest that high speed high altitude penetration, even as high & fast as a Blackbird, was seen as a dead end by the US airforce.

 

[Jeb]

I attended a presentation by a former SR-71 pilot and I'm 98% positive that he said the same, that they skirted borders but never (intentionally, I'd interject) made any (significant, I'd assume) border incursions into the Soviet Union. It was a most interesting presentation; I came away with details about Blackbird ops that I'd never heard before.

 

[coldwarpod]

I thought I heard year's ago that one MiG-31 Foxhound had actually locked onto the SR-71 but the pilot did not fire the missile, was there any truth in that rumor?

from Flying the SR-71 Blackbird: In the Cockpit on a Secret Operational Mission
By Richard H. Graham

 

[Archibald]

I attended a presentation by a former SR-71 pilot and I'm 98% positive that he said the same, that they skirted borders but never (intentionally, I'd interject) made any (significant, I'd assume) border incursions into the Soviet Union. It was a most interesting presentation; I came away with details about Blackbird ops that I'd never heard before.

Border penetration flights. Playing cat and mouse with the SAMs. No full overflight of the USSR.

There are some subtle differences.

Case 1: Border penetration flights. Example: IRIAF RF-4 Phantoms in the mid-70's. SR-71s most of the time. ROCAF U-2s over the PRC until 1968 (and plenty other ROCAF aircraft, incidentally)

Case 2: U-2 flights before Power shoot down: going from Pakistan to Turkey via a big loop into the Soviet airspace. Not sure the SR-71 ever used that trick over USSR ?

Case 3: "Grand slam" - what Power atempted to do, starting in Pakistan and landing in Norway. Did not went too well. This is also what SR-71s did over North Korea and North Vietnam.

Some facts:
- SR-71 range was much shorter than U-2 for obvious reasons
- SR-71 and A-12 (AFAIK) were never allowed to perform more than "case 1" missions, not only over USSR but also over the PRC.

- border penetration flights consist of using the surprise effect to take air defence off guards. Any tactical recon aircraft could do that at low level (RF-101, RF-4, and even subsonic platforms). SR-71 could also do using extreme altitude and speed.

 

[F-14D]

I attended a presentation by a former SR-71 pilot and I'm 98% positive that he said the same, that they skirted borders but never (intentionally, I'd interject) made any (significant, I'd assume) border incursions into the Soviet Union. It was a most interesting presentation; I came away with details about Blackbird ops that I'd never heard before.

Border penetration flights. Playing cat and mouse with the SAMs. No full overflight of the USSR.

There are some subtle differences.

Case 1: Border penetration flights. Example: IRIAF RF-4 Phantoms in the mid-70's. SR-71s most of the time. ROCAF U-2s over the PRC until 1968 (and plenty other ROCAF aircraft, incidentally)

Case 2: U-2 flights before Power shoot down: going from Pakistan to Turkey via a big loop into the Soviet airspace. Not sure the SR-71 ever used that trick over USSR ?

Case 3: "Grand slam" - what Power atempted to do, starting in Pakistan and landing in Norway. Did not went too well. This is also what SR-71s did over North Korea and North Vietnam.

Some facts:
- SR-71 range was much shorter than U-2 for obvious reasons
- SR-71 and A-12 (AFAIK) were never allowed to perform more than "case 1" missions, not only over USSR but also over the PRC.

- border penetration flights consist of using the surprise effect to take air defence off guards. Any tactical recon aircraft could do that at low level (RF-101, RF-4, and even subsonic platforms). SR-71 could also do using extreme altitude and speed.

There was a big constraint on A-12/SR-71 operations that actually preceded their first flights. After the Francis Gary Powers U-2 incident, which was a worldwide humiliation for the US, the US promised that it would never again send a reconnaissance aircraft over Soviet territory. This was made publicly and repeatedly and IIRC, even directly made by the President as well. As a result, although Blackbirds would come up really close to the line, they didn't penetrate (although they would "look in" from just outside).

If a Blackbird had crossed the line and the Soviets could prove it, it would be a tremendous propaganda victory, especially if one came down inside the USSR, either by malfunction or hostile action (if that would have been possible against an "all up" Blackbird). The Soviets usually launched fighters if they had time if they saw one coming on the off chance they could take advantage of such a situation.

In fact, in June of 1987 an SR-71 over international waters suffered an engine explosion and had to descend and slow down. For a while it wasn't certain they'd be able to stay in the air, so they turned and entered Swedish airspace. Two Viggens, later augmented by two more, intercepted the Blackbird. The Soviets meanwhile sent MiG-25s which according to reported communications intercepts had orders to force it into Soviet airspace and then force a landing or shoot it down. The Swedes, though, had decided to render aid and provided an escort "to an aircraft in distress". Even the Soviets were not going to engage in a battle with Swedish aircraft in Swedish airspace and so withdrew. The Viggens escorted the Blackbird to Danish airspace where USAF/NATO aircraft took over. This remained classified for 30 years, but eventually was acknowledged in the open and in a ceremony the US awarded medals to the pilots of the Swedish aircraft.

 

[Archibald]

CRAP !!! Lot of adrenaline was probably expended by the Swedish, American and Soviet pilots that day...