Armed to the teeth: B-70 with underwing Skybolts and SRAM internally

[A Tentative Fleet Plan]

alongside the well publicised 60-megaton 25,000-pound Class A thermonuclear weapon

Edward Teller wet dream, I presume ?

Nope, a definite SAC requirement in 1956 which was being listed as armament for the B-70 as late as 1960. The yield/weight ratio is pretty comparable to the Mk-41, and the AEC was confident it could produce such a weapon.

Strategic Air Command Declassifies Nuclear Target List from 1950s

Declassified Strategic Air Command (SAC) Nuclear Target List from 1950s Includes Contingency Plans to Strike Major Cities in Soviet Bloc and China

nsarchive2.gwu.edu

It was intended for the counter-air role to reliably crater runways. I've realised that this isn't put a crater on the runway, in the way that we've become used to thinking about the task since the 1970s and conventional counter-air weapons. It's put the runway in a crater - the cratering radius for a 60 megaton ground burst is such that if it's delivered to the midpoint of a 10,000-foot runway, the crater will reach both ends.

I must put something up about the US thermonuclear weapons, though I'm not sure where it would best fit.

Flashback?

 

[Yellow Palace]

I must put something up about the US thermonuclear weapons, though I'm not sure where it would best fit.

Apparently I found the answer: on my blog.

Teaser: the 60-megaton bomb came very, very close to being tested.

 

[Archibald]

I'm glad it wasn't tested, really...

 

[Yellow Palace]

I'm glad it wasn't tested, really...

I think you're right - it would probably have been a full-yield (i.e. dirty) test from a barge. The fission yield would have been on the order of 30 to 40 megatons and there would have been significant crater excavation. The resulting fallout would be horrendous.

 

[Archibald]

Tsar bomba shook the entire planet but was (somewhat paradoxically) pretty clean, as far as fallout went...

 

[Onegear7]

In the basement of the former North American Rockwell facility (Boeing) in Seal Beach, CA., is a detailed model of a proposed B-70 type. Not RS or A/B versions.

 

[Archibald]

We want pictures of that thing !

 

[Onegear7]

We want pictures of that thing !

I hesitated to post because when I worked there, no pics were allowed, therefore, I have no photographic evidence. It looked similar to what you guys have speculated, had the aircraft entered service. As a general note, many US aerospace companies keep proposal models, especially the unsolicited variety, locked away in their private libraries. Mostly because they have been forgotten.

 

[Christopher Wang]

As explained in Valkyrie: The North American XB-70 by Graham M. Simons (2011), the XB-70 / B-70 Valkyrie has a pair of tandem 14-foot weapons bays separated by a one-foot section. Due to the placement of the sliding weapons bay doors, each of the weapons bays could only be opened and used one at a time. This meant that the Valkyrie could not carry weapons longer than about 13 feet within its weapons bays.

Since the AGM-69 SRAM has a length of 14 feet (4.27 meters), or 15 feet 10 inches (4.83 meters) with the tail fairing, the SRAM would not have fit inside the Valkyrie's weapons bays ( http://www.designation-systems.net/dusrm/m-69.html ).

It may be possible for the Valkyrie to be modified to carry the SRAM externally in a manner similar to the below illustration, but it would come with the cost of increased drag:

Source: https://media.defense.gov/2020/Nov/23/2002540204/-1/-1/0/B-70%20VARIANTS.PDF

If the Valkyrie had been adopted and used through the 1980s and 1990s, a possible weapon for internal carriage would be the smaller AGM-131 SRAM II. Compared to the original SRAM, the SRAM II has a shorter length of 10 feet 5 inches (3.18 meters) and thus could have fit inside the Valkyrie's weapons bays ( http://www.designation-systems.net/dusrm/m-131.html ).

It may be possible for the Valkyrie to be modified to carry a pair of rotary launchers within its weapons bays, but it is not known how many bombs or missiles the Valkyrie could have hypothetically carried internally with the rotary launchers.

 

[Christopher Wang]

Hypothetically, could the XB-70 / B-70 Valkyrie's six General Electric YJ93 / J93 afterburning turbojets (and their fuel system) be replaced with the same number of afterburning turbofans that could fit in the Valkyrie's existing engine bays?

One engine candidate could be the Pratt & Whitney F119 which powers the F-22 Raptor and was proposed for the B-1R regional bomber concept.

Another engine candidate could be the Pratt & Whitney F135-PW-100 which powers the USAF F-35A Lightning II.

For comparison, these are the dimensions and performances of the J93, F119, and F135:

 

[Archibald]

Glad to be of help, dear beloved moderators

 

[Dilandu]

The more interesting question: what would USAF be forced to sacrifice, to make B-70 (a VERY costly plane, in both production and maintenance) up and running in any reasonable numbers? The money are limited, after all, and B-70 have limited advantages. So... what would get axed to pay for bomber command dream?

 

[Christopher Wang]

Another possible weapon option for the B-70 Valkyrie would have been the AGM-183 Air-Launched Rapid Response Weapon or ARRW.

It should be noted that the ARRW is 22 feet long with a weight of 6,600 pounds; the GAM-87 Skybolt was 38 feet 3 inches long with a weight of 11,000 pounds. Presumably, the Valkyrie could have carried two pairs of ARRWs (four total) externally in tandem on the same underwing pylons as the Skybolt.

 

[Scott Kenny]

Now a B-70 with standoff SRAMs is a little better, although that missile range was unconfortably short.

Not from 70,000ft and Mach 3, but I see that has already been addressed.

The more interesting question: what would USAF be forced to sacrifice, to make B-70 (a VERY costly plane, in both production and maintenance) up and running in any reasonable numbers? The money are limited, after all, and B-70 have limited advantages. So... what would get axed to pay for bomber command dream?

All the B-58s, all ICBMs but Minuteman and only a small deployment of a couple hundred MM, maybe the FB111 as well. Probably also get rid of everything before the B52G/H as well.

 

[Yellow Palace]

Another possible weapon option for the B-70 Valkyrie would have been the AGM-183 Air-Launched Rapid Response Weapon or ARRW.

Apart from the fact that that program didn't start until half a century after the B-70 was cancelled. It might equally well have carried proton torpedoes or enormous wheels of cheese.

The yield/weight ratio is pretty comparable to the Mk-41, and the AEC was confident it could produce such a weapon.

Just to follow up on this - the 60 megaton Class A was planned to be tested, as a full-yield surface burst, as part of the HARDTACK I test series in 1958. It was removed from the programme due to concerns about fallout - not especially because of health concerns, but diplomatic ones. Had it been tested, Bokak - about half-wayu between Wake and Bikini - would have been added to the list of atolls used as nuclear test sites.

 

[Archibald]

Nuclear porn: hardtack, wake, bikini, and bokake (I'll get my coat...)

 

[MadRat]

Hypothetically, could the XB-70 / B-70 Valkyrie's six General Electric YJ93 / J93 afterburning turbojets (and their fuel system) be replaced with the same number of afterburning turbofans that could fit in the Valkyrie's existing engine bays?

One engine candidate could be the Pratt & Whitney F119 which powers the F-22 Raptor and was proposed for the B-1R regional bomber concept.

Another engine candidate could be the Pratt & Whitney F135-PW-100 which powers the USAF F-35A Lightning II.

For comparison, these are the dimensions and performances of the J93, F119, and F135:

No, you are confusing a turbofan low altitude rating versus a turbojet's sea level rating. Like the J79-powered F-16, the turbojet crushes the turbofans performance up high and running hot. Turbojets tend to run stronger performances than their sea level rating up high and running extreme speeds, whereas that same engine is relatively lame in thrust to weight down at sea level and subsonic.

 

[Dilandu]

All the B-58s, all ICBMs but Minuteman and only a small deployment of a couple hundred MM, maybe the FB111 as well. Probably also get rid of everything before the B52G/H as well.

USAF could not allow itself to limit number of ICBM's in 60s. Congress would disband their bomber force and give missiles to Army, if USAF would even suggest anything like that. So no, Minuteman's would be deployed in real-world numbers. Who would be drastically cut is the B-52. I doubt it would even got to B-52H production; most likely production would be terminated much earlier, and by mid-1960s they would already be retiring.

 

[Scott Kenny]

Tsar bomba shook the entire planet but was (somewhat paradoxically) pretty clean, as far as fallout went...

Because they didn't do the usual yield-boosting uranium outer layer, just the fission ignitor and the fusion core.

As explained in Valkyrie: The North American XB-70 by Graham M. Simons (2011), the XB-70 / B-70 Valkyrie has a pair of tandem 14-foot weapons bays separated by a one-foot section. Due to the placement of the sliding weapons bay doors, each of the weapons bays could only be opened and used one at a time. This meant that the Valkyrie could not carry weapons longer than about 13 feet within its weapons bays.

Since the AGM-69 SRAM has a length of 14 feet (4.27 meters), or 15 feet 10 inches (4.83 meters) with the tail fairing, the SRAM would not have fit inside the Valkyrie's weapons bays ( http://www.designation-systems.net/dusrm/m-69.html ).

I suspect that if the Valkyrie had been built, the SRAM would have been made to fit.

 

[Dilandu]

Because they didn't do the usual yield-boosting uranium outer layer, just the fission ignitor and the fusion core.

Yep. The third stage was inert, due to concerns about enormous fallout from full-scale test spreading to other countries and causing international protests. It was reasoned that even 50+ megatons would be impressive enough, and hardly anyone would doubt the Soviet capability of double the yield.

 

[Yellow Palace]

Because they didn't do the usual yield-boosting uranium outer layer, just the fission ignitor and the fusion core.

Note that the proposed US Class A test in 1958 would have been with a uranium third stage, and at sea level, rather than with lead as an airburst. It would have been filthy.

It was reasoned that even 50+ megatons would be impressive enough, and hardly anyone would doubt the Soviet capability of double the yield.

I do - from what I've seen, it's more usual for the 'clean' version to have about one-third the yield of the 'dirty' version, not merely half!

 

[Trident]

Yep. The third stage was inert, due to concerns about enormous fallout from full-scale test spreading to other countries and causing international protests. It was reasoned that even 50+ megatons would be impressive enough, and hardly anyone would doubt the Soviet capability of double the yield.

That and IIRC the reduced yield also enabled burst height to be chosen such that the fire ball - just - did not touch the ground, while still allowing the drop aircraft to escape unharmed. Given how narrow the margin already was between these two criteria, a 100Mt blast could probably not have been detonated high enough.

 

[Christopher Wang]

I suspect that if the Valkyrie had been built, the SRAM would have been made to fit.

As I have mentioned earlier, if the Valkyrie had been adopted and used through the 1980s and 1990s, the smaller AGM-131 SRAM II which had a shorter length of 10 feet 5 inches (3.18 meters) could have fit inside the Valkyrie's weapons bays. There is also the possibility of external carriage underneath the Valkyrie's two Skybolt pylons, but it would come at the cost of increased drag.

 

[MadRat]

XB-70 never had a weapons bay so NA had a pretty clean slate there.

 

[Scott Kenny]

As I have mentioned earlier, if the Valkyrie had been adopted and used through the 1980s and 1990s, the smaller AGM-131 SRAM II which had a shorter length of 10 feet 5 inches (3.18 meters) could have fit inside the Valkyrie's weapons bays. There is also the possibility of external carriage underneath the Valkyrie's two Skybolt pylons, but it would come at the cost of increased drag.

Right.

But I mean that had the Valkyrie been adopted into service, the original SRAM would have been designed around the Valkyrie bomb bays and not the B-52's long single bay. The Valkyrie-SRAM would probably have a max length of 12', 2 feet shorter than what the Original SRAM ended up being.

After all, launching an SRAM from Mach 3 and 70,000ft gives a very impressive range and lateral reach, so even if the SRAM didn't have 200km range from the B52 and F111 there wouldn't be much trouble.

 

[RanulfC]

That and IIRC the reduced yield also enabled burst height to be chosen such that the fire ball - just - did not touch the ground, while still allowing the drop aircraft to escape unharmed. Given how narrow the margin already was between these two criteria, a 100Mt blast could probably not have been detonated high enough.

During the mid-80s when I was stationed in Europe we had a "weird" little article appear in (and only in) the European "Stars and Strips" newspaper. Said article noted that a Russian nuclear physicist visiting the US for a conference was removed from the stage and escorted to the airport to be put on board a flight home. The white board he was using was also confiscated and removed and the article clearly states that the formula on the board was on the possibility of building a Gigaton class explosion.

As it was well known that the the Soviets had pretty much a standing "subscription" to the Stars and Stripes most of us expected to be a clear "message received"

Randy