Bombers, Rotordynes and a fistful of Buccaneers

Bernard Woolley

Just Leo said:
My understanding of the difficulty in intercepting the SR-71 is that the relatively small radar signature rendered missile defenses into tail-chase mode, where they were not sufficiently ranged to catch up. The B-70 air intakes offered considerable radar return and offered the ability to launch missiles in a timely fashion on a collision course intercept, negating much of the speed advantage.
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The problem with hitting the B-70 is the fact that in the time it takes for a missile battery to react the bomber will have flown quite a distance. It will either have flown out of range, or have gotten within the minimum range of the missile system.
If the battery does manage to engage it will end up in a tail chase and while it will gain on the bomber (presuming no use of ECM, chaff, or maneuvering) the SAM will run out of fuel well before it gets within lethal range.

However I'm pretty sure I'm preaching to the converted and that I can type this until my fingers fall off and I won't convert anyone. :D
 

Mote

JN1 said:
To catch a target a missile needs to be going significantly faster to catch it. Even a Mach.5 missile is going to run out of fuel when chasing a Mach.3 target because it doesn't have enough of an overtake speed.
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Eh, that's entirely dependent on range and of course presumes a stern chase rather than a head-on engagement. If, for example, you have a 40 mile range at Mach 5 and 75,000 feet, then as long as you begin that particular engagement segment at 16 miles or less, you will overtake and destroy (ignoring any other factors). Typhon/Super Talos had/was to have an average speed of 1,157.5 m/s (Mach 3.9) at 70,000 feet out to 250 nautical miles (in a document stating maximum range not implied, so range could have been shorter or longer; I suspect that, if anything, longer), in a flight of 400 seconds. In a tail chase against a Mach 3 target at the same altitude, that gives it a successful overtake range of 57.6 nautical miles (possibly further given higher average speeds closer in, or lesser depending on time of boost). Of course, if it is fired in a head on intercept geometry, the range is rather longer and if it is fired at a passing target, it's somewhere in the middle.

I'm going to drop this from further on though because I really hate having to do math :p

The Sea Dart GWS 30 Mod 0 of the '60s has a top speed of Mach 2.0+ and a range of 40nm, which means it hasn't a hope of hitting a Mach.3+ target. The Bloodhound Mk.II could do Mach 2.7 and there are no confirmed performance figures for the Mk.III, though it is known that it would have been faster and have a range of 75 miles.
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Mach 2+ but based in part on RP.25 which was Mach 3 or 4 iirc, so who knows how fast the + actually is. But I did label it as merely possible.
 

Bernard Woolley

If you fire a missile head on at a B-70, or SR-71 then the plane is going to evade and change direction violently. It's not an ICBM RV after all which will continue blindly on only effected by physics.
 
PhilKearny

PhilKearny

Neither the SR-71 nor the B-70 was capable of violent manuevers. There was a reason the B-70 was cancelled, beyond its exorbitant cost--it was vulnerable to interception.

If you use the search function, you can see this discussion has been hashed over numerous times.
JN1 said:
If you fire a missile head on at a B-70, or SR-71 then the plane is going to evade and change direction violently. It's not an ICBM RV after all which will continue blindly on only effected by physics.
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Bernard Woolley

Indeed, we have discussed it at length over on HPCA.

However I'm now going to leave this discussion as I feel it is going in circles. I and a couple of others are saying 'no it can't' while others are saying 'yes it can'. Unless we can somehow get an SR-71 and an SA-5 and test this out in the real world neither side is going to change its mind.
I wonder if an email to the USAF and the Russian Air Force might help with that idea?
 

danderson

Think of it like this.

So an SR-71 is cruising at Mach 3.5 or whatever, although I guess that's kinda meaningless without knowing the equivalent ground speed.

The missile battery sees it on the radar. The missile will take X seconds to accelerate to the point where it can actually start to close with the SR-71. It will also take however many seconds to get to 85,000 ft, or however high the SR-71 flew. And then it has to finish closing with the SR-71.

Now in the time it takes to actually close, will the SR-71 still be in range?
 

Just Leo

The co-equivalence of the XB-70 and the SR-71 would be the cause of circular argument. The SR-71 was determined, by the CIA and USAF, to have a good degree of invulnerability to then current threats, and achieved some production and service. It was high, fast and stealthy. The USAF determined that the XB-70 would not possess a satisfactory survival rate to merit production. I saw one taking the sun out at Wright-Pat. Retired. We don't need a test. The USAF checked the numbers.

To date, I know of no aircraft that violently manoevers at Mach 3.2.
 

Riain

SAMs don't fire on stern chase, they are fired into a pre-calculated intercept area where the plane is predicted to fly into. This is why so many SAMs are EO and not IR guided, so they can be used in head-on attacks.
 

FlyingDutchman

Mote said:
Eh, that's entirely dependent on range and of course presumes a stern chase rather than a head-on engagement. If, for example, you have a 40 mile range at Mach 5 and 75,000 feet, then as long as you begin that particular engagement segment at 16 miles or less, you will overtake and destroy (ignoring any other factors). Typhon/Super Talos had/was to have an average speed of 1,157.5 m/s (Mach 3.9) at 70,000 feet out to 250 nautical miles (in a document stating maximum range not implied, so range could have been shorter or longer; I suspect that, if anything, longer), in a flight of 400 seconds. In a tail chase against a Mach 3 target at the same altitude, that gives it a successful overtake range of 57.6 nautical miles (possibly further given higher average speeds closer in, or lesser depending on time of boost). Of course, if it is fired in a head on intercept geometry, the range is rather longer and if it is fired at a passing target, it's somewhere in the middle.
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AFAIK the S-200 (which was discussed earlier) had a topspeed of Mach 4 and certainly not a average speed of Mach 4. Considering the SR-71 starts at a cruising speed of Mach 2+ and at x-thousand metres while the missile starts at 0 speed and altitude, any missile intercepting from the ground is at a huge disadvantage.

I wouldn't know how succesfull a S-200 with it's nuclear payload would be. Considering it's 25 kT according to Wiki, that would be slightly bigger then Fat Man.

Stuart Slade wrote the following on the HPCA board. He considers the chance of even the S-400 slim against a SR-71 or B-70.
I understand this has been discussed in threads on this forum in the past, but I can't remember stuff like this being mentioned in them.
Your maths are a biit off here; even if the 240 miles figure is correct, the aircraft takes only 6.8 minutes to cross the danger zone (at these speeds, a tail-chase is out of the question. However, the 240 miles figure isn't correct. 240 miles is its maximum horizontal range under idea conditions. Likewise, it's operational ceiling, 131,000 feet, is its maximum operational ceiling, essentially when the missile is fired straight up. Without access to the S-400s actual performance graph (which is classified and likely to remain so) we don't know exactly what its range is at a target flying at 85,000 feet. However, we can make an estimate and applying the usual mathematics, we can estimate its range against a target flying at 85,000 feet as 84.25 miles. This means a target flying at Mach 3.2 will cross the danger zone in 2 minutes and 23 seconds

Before anybody asks, the equivalent data for a production-standard B-70 doing Mach 3.4 at 90,000 feet are a missile range of 75 miles and a crossing time of almost exactly two minutes.

That isn't the end of the story. Missiles don't just have a maximum range, they have a minimum range as well. We don't know what the minimum range of a S-400 is but typically long-range, high-altitude missiles have correspondingly long minimum ranges. Also, radars don't look straight up so there is a radar blind zone over the heads of the missile battery. What this means is that the danger zone isn't a semi-circle or a semi-sphere but a shape that looks more like a half-donut. So, the danger zone isn't measured from the outside of the semi-circle to the launch battery but from the outer edge of the danger zone to the outer edge of the blind zone. This cuts the engagement time down still further.

S-400, when it finally works which it doesn't at the moment, is undoubtedly an effective weapon but it is struggling at the limits of its performance when faced with an SR-71 or a B-70. By the time one adds in reaction times and the command loops involved, I would rate its chances against either aircraft as being marginal.
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http://www.tboverse.us/HPCAFORUM/phpBB3/viewtopic.php?f=6&t=6770&start=20
 

Just Leo

There was no production standard B-70. The real XB-70 achieved mach 3.08 and 77,000 feet, in a test. Not bad. It wasn't loaded with weapons during testing. Hypothetical production machines may have been of lower, not higher, performance, since the solution to structural weakness and corrosion problems may have increased weight. Correcting the problem with ejection modules might also increase weight. The fact that Admiral Slade stretched his figures for his hypothetical argument casts a pall on the verity of his conclusions.
 

MKSheppard

Hi there everyone! I'm the owner of the said alternatewars site.

It's nice to see that some of my hard OCRing work is being used in arguments. :D

Several years ago, I had the opportunity to visit Wright-Patt and to see the XB-70A in person for the first time. I also spent about a week scanning in documents at the USAFM archives.

There were to be three aircraft built originally for the flight test program:
Air Vehicle #1 and Air Vehicle #2. These were designated XB-70A.

Air Vehicle #3; which was to be the XB-70B. Alternately it was also known as the YB-70 -- it would have carried an early version of the AN/ASQ-28 Bomb/Nav computer, as well as a four man crew to test out early electronics integration and to do bomb drop tests.

However, A/V #3 was cancelled, and errors in the construction of air vehicle #1 caused one of the fuel tanks to be permanently sealed off (it leaked like crazy); and a speed/altitude limit to be imposed (due to it using early production honeycomb skin); meaning it was restricted from sustained Mach 3 flight (it could hit it for short bursts), due to skin problems -- the skin actually was in danger of delaminating from it's honeycomb core.

A/V #2, being built later in the program, benefited from the mistakes made in A/V #1's construction, and was significantly better performing due to the problems with the stainless steel honeycomb construction being corrected.
A/V #2 proved that the B-70 as designed could cruise indefinitely at Mach 3 as long as it had fuel by doing a 30 minute flight at Mach 3 (which was when the engineers calculated maximum skin expansion and heating would occur).

However, before we could fully explore the envelope of Mach 3 flight, A/V #2 was lost in a mid-air collision with a F-104.

A/V #1 went on to do some research for NASA before being flown to the USAF Museum.

So. Enough talking.

Here's the Statistics for the B-70, which you see most commonly quoted (the specs are from Baugher).

Maximum speed 1982 mph at 75,550 feet, 1254 mph at 35,000 feet.
Landing speed 184 mph.
Service ceiling 75,500 feet. Initial climb rate 27,450 feet per minute.
Combat range 3419 miles, maximum range 4290 miles.
Dimensions: Wingspan 105 feet, Length 196 feet 6 inches, Height 30 feet 8 inches, wing area 6297.15 square feet.
Weights: Empty weight 231,215 pounds, 521,056 pounds gross weight, 534,792 pounds maximum.

You can compare them with the planned B-70A model (as of 8 June 1960):

B-70 SAC Page 1
B-70 SAC Page 2
B-70 SAC Page 3
B-70 SAC Page 4
B-70 SAC Page 5
B-70 SAC Page 6
B-70 SAC Page 7

Some things to note:

If you have read Jenkin's book on the B-70; you might have noticed this line:

Some reports indicate that A/V-3 and production aircraft would have had another fuel tank in each wingtip, but the structural complexity of adding weight into this movable panel might have been extreme. It is likely that the fuel in the wingtip tanks would have been used during climbout, with the tanks remaining empty once the tips were lowered.

If you looked at Page Two of the SAC you would have noticed that the wingtips contain these movable fuel tanks, with 670 gallons of fuel in each wingtip.

Another thing you might notice are the power listings that they have for the J93-GE-3 on Page Three: 29,500 lbf per engine.

The January 1972 SAC for XB-70A Air Vehicle 1 has the YJ93-GE-3 producing 28,000 lbf maximum.

That's 9,000 lbf more of installed thrust on the B-70A over the prototypes.

Page Four of the SAC has the following flight profile for the B-70A's Design Mission II:

Takeoff weight of 554,609 lbs with 347,710 lbs of fuel, 10,000 lbs of bombs and 900 lbs of IRCM decoys.

Cruise out towards the target at 1,721 knots knots at 65,000 feet slowly climbing to 77,700 ft cruise altitude as the plane lightens up (Mach 2.998).

By the time it's over the target area, the B-70A weighs only 240,892 lbs; and is doing 1,731 knots at 85,100 feet when it drops it's bomb(s).

What's really interesting is that in the XB-70B A/V 3 Characteristics sheet for 9 May 1963; it says that A/V 3 would have:

"CRUISE at max speed 1,721 knots at 65,000-73,100 ft alt min A/B."

If we assume that minimum afterburner is 21,500 lbf from each engine (just above military power); then that means that the B-70A has a power reserve of 48,000 lbf thrust that it can use to either climb very high to 85,000~ feet, or stay at 75,000 feet and go faster.

And of course, it's got a load factor of 2.0 Gees throughout it's envelope.

That's more than enough to mess up SAM trajectories.

The Tsybin RSR, a Soviet Blackbirdski Mach 2.8~ aircraft came up with two methods during it's development to evade the evil Capitalist SAMs.

One was to do a barrel roll -- the RSR would end up at an altitude of 137,800 feet at the top of the roll.

The other method was to do a climbing turn on the order of 2.5Gs.
 

MKSheppard

SAM performance is not a basic cylinder that extends to maximum range and goes up to maximum altitude.

HQ-2BEnvelopeSmall.gif


Image is from Jane's Land-Based Air Defences.

Altitude from 0 feet to 88,580 feet. Mach 3 is about 885 m/sec.

This is a much more nuanced view than the simple 27 km maximum altitude and 34 km maximum range quoted for the HQ-2B.

You can see how if you're tooling around in something that resembles the B-70; you've reduced the engagement envelope; in much the same manner you would if you were flying around in a B-2 and evading enemy radars.

And this is from simple speed alone -- it doesn't take into account on-board ECM.
 

MKSheppard

This was found and posted on Secret Projects co.uk by SOS. I've OCRed the paper and cleaned up the images somewhat. I do wish he had posted higher resolution, non JPG scans though... :cry:


THE STRATEGIC ASPECT OF SUPERCRUISING FLIGHT
BY Ben R. Rich
For Delivery at the SUPERCRUISE MILITARY AIRCRAFT DESIGN CONFERENCE
17 through 20 February 1976

THE STRATEGIC ASPECT OF SUPERCRUISING FLIGHT

The vulnerability of aircraft to missiles and radar controlled guns was vividly demonstrated in the 1973 Mid East War where 443 aircraft were destroyed in eighteen days. Simulations show that the survivability of aircraft increase primarily with increases of speed, altitude, maneuverability and ECM. These have been confirmed by experience with the SR-71, the only United States supercruising military aircraft. There are other secondary factors that contribute to survivability such as the various aspects of stealth and size, reaction or response times, etc.

The physical and aerodynamic requirements for efficient supersonic flight vehicles ail result in increases of flight altitude with increase in flight speed and vice versa. Speed increase is necessary to meet the mass flow requirements of air breathing propulsion systems. Super-cruiser parametric studies show that as cruise speed increases above Mach 2.0, altitudes for efficient cruise exceed 50,000 feet.

Let us now review the threat to vehicles which cruise at high Mach number and high altitude. Figure 1 depicts Soviet missiles, gun, and aircraft capability vs. altitude. Shown on the right hand column are typical cruise altitudes for strategic aircraft as a function of speed. The data show that for altitudes below 60, 000 feet, aircraft aire vulnerable to a multiplicity of weapon systems. Focusing on the USAF's only current supercruising aircraft -- the YF-12/SR-71 series, which cruise above Mach 3. 0 and 80,000 feet -- I will limit my comments to these aircraft. The aircraft has maneuver capability better than 2. 5 g's. The double delta planform of the SR-71, as shown in Figure 2, is designed, with sharp leading and trailing edges; no right angle intersections, inclined vertical fins, etc. to achieve a low radar cross section. The aircraft, illustrated in Figure 3, is constructed, with over 20 percent of its surface area, of high temperature composite material to give a radar cross section under 10 square meters. The anti-radar design background was given in a paper delivered by Kelly Johnson to the Radar Camouflage Symposium at Wright-Patterson Air Force Base on October 3, 1975, entitled "Reduction of Radar Cross Section of Large High Altitude Aircraft. " (5)

Air-to-Air Threat

Currently, there is no real operational air-to-air threat to the SR-71. Let us consider the Soviet's most advanced aircraft, the MiG-25 FOXBAT. Figure 4 provides an overview of the main elements of the intercept problem. Figure 5 gives the operational steady state and zoom envelopes of the FOXBAT. If you assume the pilot sitting in the cockpit on alert, the FOXBAT climbout and missile performance are shown in Figure 6. The data show that it takes 8 minutes from brake release to reach its maximum steady state cruise altitude, assuming no maneuvering. Also shown are the FOXBAT radar and the AA-6 missile characteristics with its aerodynamic and seeker limits. The shaded area shows the limited attack zone against a cruising SR-71. To better appreciate the time and distances involved, Figure 7 shows the FOXBAT climb characteristics on a head-on, fly-over attack against penetrators approaching at speeds up to Mach 6. Just during the time required for the FOXBAT to reach its cruise altitude (8 minutes), the Mach 3.2 aircraft has penetrated 240 nm, while Mach 6 attacker has penetrated 480 nm. The data assumes no evasive maneuvering by either aircraft and instantaneous reaction by the FOXBAT.

The effect of maneuvering is shown in Figure 8. This figure assumes that the SR-71 makes a 45 degree weave maneuver. Using FOXBAT performance characteristics, from airborne alert, and for various start locations, the figure shows that no clearly successful intercept can be made. It can be generally concluded that the air-to-air intercept problem is at the present time extremely marginal versus a high supersonic Mach number maneuvering target.

Surface-to-Air Threat

The Surface-to-air missile intercept problem also needs to be considered. Figure 9 shows the SA-2 missile footprint for three nonmaneuvering target speeds/altitude combinations. The way increasing speed/altitude reduces SA-2 capabilities is apparent from the diminished size of the vulnerable area. If you take a vertical cut of this same SA-2 envelope, Figure 10, the effect of speed and altitude are shown. No intercept is possible at speeds above Mach 3.2 and altitudes above 90, 000 feet.

Any type of maneuver considerably reduces the SA-2 capability as was shown in the Viet Nam war. In the several hundred flights over the Hanoi -Haiphong areas, no losses or damage were experienced. Discussions with regards to the SA-5 GAMMON missile exceed the classification of this paper. The above discussion is limited to nonnuclear missiles, no attempt will be made to discuss the nuclear threat.

Strategic Applications for Supercruise Aircraft

There are three strategic missions for a supercruising aircraft: reconnaissance, surveillance, and offense or strike.

The SR-71 is currently performing the reconnaissance and surveillance mission for the USAF Strategic Air Command. The aircraft has been operational in the South East Asia Theatre for over seven years. During the Viet Nam war, it made several hundred combat flights over North and South Viet Nam. During the 1967 Mid East war, operating from the Continental United States, the SR-71 completed several successful overflights of the Suez-Sinai battlefronts. In all these operations, the SR-71 suffered no loss or damage from any hostile action. Since its first flight in 1964, the aircraft has approximately 5, 500 hours over Mach 3.0.

Let me show you how we can exploit supercruising for the strike concept.
During 1965-1966, the YF-12 interceptor successfully demonstrated the firing of missiles from over Mach 3. 0/80, 000 feet. The YF-12 successfully launched 13 AIM-47 missiles (Hughes GAR-9). Twelve successful shots, direct hits or lethal near misses, were achieved on subsonic drone targets flying at sea level to 40, 000 feet over land and sea. The one failure was attributed to a guidance malfunction.

Figure 11 shows a strike version of the SR-71 -- called the Bx -- with four AGM-69A SRAM missiles. The range of the SRAM missile can be extended by a factor of 4 when launched at Mach 3. 0 and 80,000 feet, as shown in Figure 12. This significant improvement in range derives from the large potential and kinetic energy imparted to the missile by the high altitude and high speed of the aircraft at cruise. The current SRAM is a nuclear missile with no terminal guidance. The CEP's are therefore not sufficiently accurate for high target kill probabilities; for example, at 100 nm range the CEP is approximately 1,500 feet and at 300 nm it is approximately 3,600 feet. However, with pre-launch navigational update and new improved gyros, these CEP's can be halved. Accuracy can be further improved, of course, by terminal guidance, the discussion of which is the subject of other papers.

In summary, the super cruise concept when applied to the strategic strike mission can be complementary to the B-1 mission. It provides a highly survivable weapon system and could dilute the Soviet defense system.

Conclusions

Although the discussion has been on strategic missions, the lessons learned from the SR-71's operation can be applied to a Tactical Supercruiser or an Advanced Tactical Fighter. Significant improvements have been made during the last few years in supersonic aerodynamics, propulsion, materials, avionics and stealth technologies. All these items tend to improve performance and survivability for advanced supersonic aircraft. There can be no doubt that the SR-71 survivability factors: supersonic speed, high altitude, high stealth, maneuverability and ECM will also provide a high probability of survival to aircraft performing tactical missions.

(Will repost the pictures later I'm tired)
 
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