XB-70 Questions

[KJ_Lesnick]

From what I remember the two biggest problems with the XB-70 was that

1: It was very expensive by itself
2: The USAF was supposed to either select WS-125 or WS-110 (what would become the B-70) and funded both (Even after by 1956 it was realized WS-125 was not a feasible strategic bombing aircraft)
3: US Military spending was excessive

That being said, my question revolves around the XB-70 and whether it'd have any chance of being developed either...
1: Immediately after it was believed to be an unfeasible strategic weapons delivery platform?
2: After it was realized it was possible to achieve continuous supersonic flight with improved aerodynamics, and propulsion?

[philp]

I think one of the main problems besides the expense was the change in tactics required by the Soviet air defense, especially the SAM threat.

However, I always thought some of the learnings could have gone into the SST programs.  Whether you can convert a XB-70 to a commercial plane or not.

[Joe C-P]

High speed and altitude were no longer considered protection against SAMs. Part of it was Gary Powers being shot down.

[rickshaw]

High speed and altitude were no longer considered protection against SAMs. Part of it was Gary Powers being shot down.

The problem was that the U-2 lacked one of those two qualities and so the SAMs were effective against it.  When combined, high altitude and high speed make a very complex defensive problem indeed, particularly when coupled with manoeuvrability. Mr.Powers and his compatriot U-2 pilots flew a jet powered sail plane and was attempting to tax the maximum range out of it, to get across the fUSSR.  That meant he was flying a predictable course at a low speed, which made the interception problem fairly straight forward (as it was, most of the SAMs missed and it was the shockwave rather than fragments which knocked him out of the sky).   The XB-70 OTOH, particularly in wartime would be flying at high altitude, high speed and manoeuvring all over the sky and using ECM.   The early SAMs wouldn't have been able to cope - unless they carried nuclear warheads perhaps and even then, it would need to get fairly close to be effective.

What really killed the XB-70 was that the ICBM promised to be cheaper, easier to build and couldn't effectively be defended against.   It also offered the promise that you wouldn't have the problems associated with trying to get the delivery system's crew back home, after they had dropped their bombs.  A not inconsequential concern in a society which believed that nuclear war was simply a bigger, badder version of the wars that had gone before it.

[KJ_Lesnick]

JoeP

High speed and altitude were no longer considered protection against SAM's.

The U-2 flew at 0.9 Mach, the XB-70 could officially do Mach 3 at 75,000 feet, and in reality, it might have been able to do Mach 4 at at least 95,000 feet

• A book called "Valkyrie: North American XB-70" by Steve Pace had a statement on Page 6 (right-side, mid/lower) that the GE X-279E were rated for Mach 4
  
• The same book had a diagram on page 41 (upper) depicting an inlet which could produce at least 14-15 clearly defined shockwaves (assuming it's accurate)
  
• Walt Spivak said the inlets were good for Mach 4 performance (he was the Chief Engineer on the B-70)
  

Either of these speeds would result in a great deal of trouble in interception


rickshaw

When combined, high altitude and high speed make a very complex defensive problem indeed, particularly when coupled with manoeuvrability.

Yeah and the B-70 could pull 2-3g's even when at speed and altitude if I recall right.

The XB-70 OTOH, particularly in wartime would be flying at high altitude, high speed and manoeuvring all over the sky and using ECM.

Exactly, you throw all of them together and it makes intercept highly improbable.  The SA-2 could probably be defeated without too much difficulty provided it was using a conventional warhead, there was a variant called the SA-2E which had a provision for a 15-kt warhead (dunno how many were built); the SA-3 might have been limited to lower altitudes, but the SA-5 would be a formidable danger.

What really killed the XB-70 was that the ICBM promised to be cheaper, easier to build and couldn't effectively be defended against.

I thought a big role in the massive support for it however was due to a desire to cut down the costs of the bombers (which included the B-70 and WS-125 concurrently being developed) being developed.

It also offered the promise that you wouldn't have the problems associated with trying to get the delivery system's crew back home, after they had dropped their bombs.

Why was that such a big deal?  I assume if you flew fast enough the bombs would detonate behind you and you'd be moving fast enough to escape the blast?

[rickshaw]

JoeP

High speed and altitude were no longer considered protection against SAM's.

The U-2 flew at 0.9 Mach, the XB-70 could officially do Mach 3 at 75,000 feet, and in reality, it might have been able to do Mach 4 at at least 95,000 feet

• A book called "Valkyrie: North American XB-70" by Steve Pace had a statement on Page 6 (right-side, mid/lower) that the GE X-279E were rated for Mach 4
  
• The same book had a diagram on page 41 (upper) depicting an inlet which could produce at least 14-15 clearly defined shockwaves (assuming it's accurate)
  
• Walt Spivak said the inlets were good for Mach 4 performance (he was the Chief Engineer on the B-70)
  

Either of these speeds would result in a great deal of trouble in interception


rickshaw

When combined, high altitude and high speed make a very complex defensive problem indeed, particularly when coupled with manoeuvrability.

Yeah and the B-70 could pull 2-3g's even when at speed and altitude if I recall right.

The XB-70 OTOH, particularly in wartime would be flying at high altitude, high speed and manoeuvring all over the sky and using ECM.

Exactly, you throw all of them together and it makes intercept highly improbable.  The SA-2 could probably be defeated without too much difficulty provided it was using a conventional warhead, there was a variant called the SA-2E which had a provision for a 15-kt warhead (dunno how many were built); the SA-3 might have been limited to lower altitudes, but the SA-5 would be a formidable danger.

The SA-5 is an unknown but going by what I know about it's radars, it wouldn't at that time be any surprise

What really killed the XB-70 was that the ICBM promised to be cheaper, easier to build and couldn't effectively be defended against.

I thought a big role in the massive support for it however was due to a desire to cut down the costs of the bombers (which included the B-70 and WS-125 concurrently being developed) being developed.

It also offered the promise that you wouldn't have the problems associated with trying to get the delivery system's crew back home, after they had dropped their bombs.

Why was that such a big deal?  I assume if you flew fast enough the bombs would detonate behind you and you'd be moving fast enough to escape the blast?

The aircraft would still need to fly long distances within Soviet airspace.  While most energy would be devoted to intercepting incoming threats, they wouldn't pass up an opportunity to eliminate an outgoing one if it presented it.  Any time inside enemy airspace means you are vulnerable to attack.  There would be some attrition.  Much easier to keep the crew at home, deep in a hole than in the cockpit of an aircraft over enemy airspace.  Given American concerns about ensuring the safety of their servicemen, it would be doubtful they would be cynical enough to suggest they, "keep flying East and find a nice Mongolian woman to settle down with..."

[albeback]

I'm by no means an expert on the subject but, I do wonder of the "vulnerable to SAMs" argument is a bit of a red herring? The actual performance of the XB-70 was at least similar to the SR-71 which, successfully evaded all attempts to intercept it during its long career.

[pyro-manic]

But had they entered service, a missile capable of reliably intercepting it would surely have been developed. The Soviets could not have afforded to not have one in that case. A version of the S-200 or S-300 missile seems reasonable and realistic.

[rickshaw]

I'm by no means an expert on the subject but, I do wonder of the "vulnerable to SAMs" argument is a bit of a red herring? The actual performance of the XB-70 was at least similar to the SR-71 which, successfully evaded all attempts to intercept it during its long career.

Wellll, it did and it didn't.  Depends on who you talk to about the SR-71.  The reality is that by about 1972 the SR-71 wasn't putting itself into situations where it actually faced SAMs.  Manned interceptions were rumoured to have been accomplished by the Lightnings of the RAF flying ballistic trajectories over the head of the SR-71, while the Swedes claimed they could intercept it with Viggens.   The MiG-25 had the performance to do it as well, and had the missile armament to make sure of it.   The SR-71 wasn't invulnerable, just a difficult target.

As Pyro suggests, if the B-70 had entered service, a means of interception would have been developed.  The fUSSR simply couldn't afford not to.  Existential threats tend to do spur that sort of effort.   That is the nature of the offensive-defensive contest.   One side develops something, the other develops a counter to it, ad infinitum.

[KJ_Lesnick]

rickshaw

The SA-5 is an unknown but going by what I know about it's radars, it wouldn't at that time be any surprise

Yeah, it was a nasty weapon.  I'm not sure how easy we could have jammed it admittedly

The aircraft would still need to fly long distances within Soviet airspace.

True enough

While most energy would be devoted to intercepting incoming threats, they wouldn't pass up an opportunity to eliminate an outgoing one if it presented it.

Of course, even if they've wiped a city or some strategic target off the map, spite would still be a good enough motivator to destroy it.

There would be some attrition.

It's the inevitable cost of war

Much easier to keep the crew at home, deep in a hole than in the cockpit of an aircraft over enemy airspace.

Personally, I don't like risking people's lives for nothing, but I realize it'll happen.  The question is simply how many will die.  Regardless, if I recall those silos can be destroyed by heavy enough nukes.  That means they'd die anyway so whether they die in a hole or in a cockpit of an airplane over enemy airspace is really the question from what it appears.

But had they entered service, a missile capable of reliably intercepting it would surely have been developed.

True, but the Soviets seemed to seriously believe the B-70 could only do Mach 3, and the SR-71 Mach 3.2 even though they were both faster.  I can't think of any other reason the MiG-25 would have been built as it was.  The Mach gauge on the MiG-25 is arranged (admittedly all the way around) as either

- 02 04 06 08 1 02 04 06 08 2 02 04 06 08 3 and then back around to 02 04 06 08
- 01 02 03 04 05 06 07 08 09 1 01 02 03 04 05 06 07 08 09 2 01 02 03 04 05 06 07 08 09 3 then back around to 01 02 03 04 05 06 07 08 09

So mach numbers of 3.2 looked like 0.2 so with the needle going all the way up like that I would not be surprised if 3.5 or 3.8 would be the max speed as the engines would sustain fatal damage when pushed beyond the limit.  Weird to build an interceptor with that performance around intercepting a plane that's hypersonic (A-12), and the XB-70 was capable of cruising 2-5 tenths of a mach faster than the Bat could and could dash probably a 1-3 tenths faster.

A version of the S-200 or S-300 missile seems reasonable and realistic.

True enough

As Pyro suggests, if the B-70 had entered service, a means of interception would have been developed.  The fUSSR simply couldn't afford not to.  Existential threats tend to do spur that sort of effort.   That is the nature of the offensive-defensive contest.   One side develops something, the other develops a counter to it, ad infinitum.

Do you think they could have produced a counter that could have been un-defeatable by the XB-70 (i.e. jamming to hinder tracking, lock-on, breaking the lock, maneuvering and speed) over a 10 year period (The B-70 was supposed to serve 10 years).

[rickshaw]

Do you think they could have produced a counter that could have been un-defeatable by the XB-70 (i.e. jamming to hinder tracking, lock-on, breaking the lock, maneuvering and speed) over a 10 year period (The B-70 was supposed to serve 10 years).

No.

The leap-frogging would occur.  You jam?  We build a home-on-jamming missile.  You break lock-on, we develop multiple tracking radar which are integrated with the missile (it accepts multiple frequency reflections).  You manoeuvre, we develop either equally manoeuvrable missiles or a multitude of launch sites so no matter where you go, there is a missile covering it.

However, the question would have to be asked - why bother when building an effective ABM defence is nearly impossible?   Even if the Soviets do build one, then you build MIRV'ed missiles which swamp it.

ABM defence is very difficult problem, despite what the proponents claimed and continue to claim.  It can easily be defeated with decoys or swamped by large numbers of MIRVs.   Even getting the anti-missile-missiles into the right region of space as the incoming missiles at the right time is incredibly difficult.  Today, despite what the USAF might claim or the US Government believes, the physics haven't changed.   Against a few missiles from North Korea you might have some chance, against what the fUSSR could field, there is none.

[Madoc]

Cost.  Pure and simple.  McNamara brought bean counting to the Pentagon like nothing else.  He looked at the costs of an ICBM force versus fielding B-70s as well and decided to kill the more immediately expensive one.  Doing so also further demonstrated his mastery over the Pentagon's generals - something he was rather keen on demonstrating no matter how much it affected our military capabilities.

[KJ_Lesnick]

rickshaw

No.

So it could have held up 10 years?

The leap-frogging would occur.

Well that's obvious -- the question is did the Russians really understand how fast we were capable of flying?

You jam?  We build a home-on-jamming missile.

How good were the Russians at that?

You break lock-on, we develop multiple tracking radar which are integrated with the missile (it accepts multiple frequency reflections).

I assume the US was capable of developing this, could the Russians?

You manoeuvre, we develop either equally manoeuvrable missiles or a multitude of launch sites so no matter where you go, there is a missile covering it.

Good point and Pye Wacket was pretty agile; admittedly wouldn't it be possible to develop a Pye-Wacket that could use a radar-seaker for hunting missile sites?

However, the question would have to be asked - why bother when building an effective ABM defence is nearly impossible?

Good point, and truthfully continuing along the "bigger higher faster farther" attitude, it's economically unsustainable.   

Even if the Soviets do build one, then you build MIRV'ed missiles which swamp it.

Of course they could hit the payload bus before it could release them all...

[SJPONeill]

When the struggle is for national survival, a small nuclear SAM warhead will put paid to any speed and altitude issues; also the B-70 would have still need main operating bases to fly from i.e. major first strike targets...the ICBM was and is a better option - just not one as cool...

[KJ_Lesnick]

SJPONeill

When the struggle is for national survival, a small nuclear SAM warhead will put paid to any speed and altitude issues

Especially when PENAID's are involved... deterrence however will only revolve around the threat of their use.  Actual launching is suicide and the enemy could perform a sneak attack on the site by low-altitude penetration (hey if we could do it; they could).

Bombers could be used as a deterrence not just by threatening their use but having them fly near enemy airspace with refueling periodically carried out mid-air before the aircraft would return home

the B-70 would have still need main operating bases to fly from i.e. major first strike targets...

True, but they could be refueled in the air a bit.  The question would ultimately come down to the following
1: The fact that the crew would get tired (admittedly having a pilot and co-pilot could help that)
2: The fact that I'm not sure if the plane had a toilet (when you gotta defecate, you have to defecate)
3: If the tanker bases were taken out (honestly a large sea-plane tanker should have been pursued as it would have fixed this up)
4: The crew would eventually run out of water and food

the ICBM was and is a better option - just not one as cool...

Well it would (and did) deal with the issue of bombers getting ever larger and faster.