"Flashback:" Americas Tsar Bomb

[Christopher Wang]

Today marks the 80th Anniversary of the atomic bombing of Nagasaki on August 9, 1945.

As recounted by Wellerstein (2021), these are the figures that Atomic Energy Commission Chairman Glenn Seaborg presented to the Kennedy Administration on the dimensions for a 50- to 100-Mt American Tsar Bomba:

October 18, 1961
Mass: 30,000 pounds
Length: 12 feet
Diameter: 6 feet

December 13, 1962
Mass: 30,000 pounds
Length: 23 feet
Diameter: 5.5 feet

April 17, 1963
Mass: 35,000 pounds
Length: 305 inches / 25.417 feet
Diameter: 70 inches / 5.84 feet

SOURCE: Wellerstein, A. (2021, October 29). The Untold Story of the World's Biggest Nuclear Bomb. Bulletin of the Atomic Scientists. Retrieved from https://thebulletin.org/2021/11/the-untold-story-of-the-worlds-biggest-nuclear-bomb/

 

[Michel Van]

Mass: 30,000 pounds
Length: 23 feet
Diameter: 5.5 feet

Only a B-52 can carry two Flashback to Designated target.
however in time consider the B-52 as intermediate step replace by Supersonic Bomber like B-58 and XB-70.
and for operational ICBM was warhead too heavy

seems that was reason why McNamara never consider Flashback as option.

 

[jeffb]

Only a B-52 can carry two Flashback to Designated target.
however in time consider the B-52 as intermediate step replace by Supersonic Bomber like B-58 and XB-70.
and for operational ICBM was warhead too heavy

seems that was reason why McNamara never consider Flashback as option.

After reading Alex Wellerstein's fascinating article (thank you Christopher for providing the link which I reproduce here as an encouragement for others) it became obvious after a while that very-high yield weapons were cumbersome and inefficient in all but a few special cases because of scaling effects and that better results could be achieved with multiple, smaller warheads.

The untold story of the world’s biggest nuclear bomb

The secret history of the world’s largest nuclear detonation is coming to light after 60 years. The United States dismissed the gigantic Tsar Bomba as a stunt, but behind the scenes was working to build a “superbomb” of its own.

thebulletin.org

Of interest were the even more insane efforts by Teller in the 50s to design weapons in the 1000Mt-10,000Mt range.

However, a study from 1963 suggested that, if detonated 28 miles (45 kilometers) above the surface of the Earth, a 10,000-megaton weapon could set fires over an area 500 miles (800 kilometers) in diameter. Which is to say, an area about the size of France.[6]

Definitely worth a read.

 

[Justo Miranda]

Only a B-52 can carry two Flashback to Designated target.
however in time consider the B-52 as intermediate step replace by Supersonic Bomber like B-58 and XB-70.
and for operational ICBM was warhead too heavy

seems that was reason why McNamara never consider Flashback as option.

Gigantism proved to be a wrong trend, it is much more effective to use multiple warheads with the ability to accurately target different targets covering much larger areas.

There was no point in sending slow, heavily loaded aircraft against the three defensive rings of the Soviet-developed Sam system.

Even a toxically anti-tech individual, trained at Berkeley, can do something useful from time to time.

 

[Dilandu]

Of interest were the even more insane efforts by Teller in the 50s to design weapons in the 1000Mt-10,000Mt range.

Hardly insane; they were supposed to have a specific effect - continental-scale firestorms, but with no long-term radioactive contamination.

 

[jeffb]

Hardly insane; they were supposed to have a specific effect - continental-scale firestorms, but with no long-term radioactive contamination.

They burn cleaner but it's not a case of no long-term radioactive contamination

Had he not reduced its yield by half, the 100-megaton bomb would have contributed about half as many fission products as were released by all nuclear tests prior to the test moratorium. As it was, even a bomb that was only 3 percent fission wasn’t exactly clean in an objective sense—as it still released almost two megatons of fission products. But in a relative sense (comparing fission yield to total yield), it was one of the cleanest nuclear weapons ever tested.

 

[MihoshiK]

They burn cleaner but it's not a case of no long-term radioactive contamination

I think that in absolute terms Dilandu is referring to fallout caused by soil irradiation. The intended use for these weapons would ensure that there would be no cratering, no soil being pulled into the fireball, and no massive amounts of fallout.
There would still be fission products, but relative to the damage that these things would do they would be quite "clean".

 

[Michel Van]

For me is unclear why the soviets try to build a 100 MT warhead with UR-500 ICBM
wanted Soviet reduce the numbers on ICBM but guarantee maximum destruction as deterrent ?
in early years of ICBM USSR hat only FOUR US targets: New York, Washington D.C. Chicago, Los Angeles
here to use 100 MT warhead make "Sense" as Contervalue strike in case of USA nuclear attack on USSR.
(the US nuclear warplan envision also similar overkill on Moscow)

On Edward Teller after first H-bomb, he went full overdrive proposed several classified projects
Likewise RAND corp. made analysis on "optimal Nuclear warfare"
Like Doomsday weapon, who in case of Nuclear attack destroy the world
This insane concept put the Mutual Assured Destruction to ultima level
here fit Teller proposed 1000Mt-10,000Mt Nuke. (project Sundial ?)

Also proposed Edward Teller clean H-bombs, something the Military wanted for the battlefield.

However McNamara put end to US Doomsday concepts, clean H-bomb and other similar projects.
once a Doomsday weapon operate, you have no control over it and prone to errors or rouge elements.
that reason why Soviets abandoned there Doomsday project
watch movie Dr Strangelove on that topic

Clean H-Bomb so nice it sound, it let temptations for politician to use them too easy.
McNamara stick to dirty H-bomb to guarantee Mutual Assured Destruction or MAD...

 

[Dilandu]

For me is unclear why the soviets try to build a 100 MT warhead with UR-500 ICBM
wanted Soviet reduce the numbers on ICBM but guarantee maximum destruction as deterrent ?

The general idea behind AN602 was to demonstrate, that USSR is leading in nuclear weapon development as well as in missile & space technology. Any kind of weapon development was essentially an afterthought; main goal was to demonstrate to USA, that USSR could also develope and deploy nuclear weapons of any desired power. So basically a demonstration device was first, its weaponization - second.

About tactical role of superheavy 100-megaton warhead - I suppose, it was planned to be used against super-hardened undergound bunkers, like NORAD HQ. Later for that reason some R-36 missiles were equipped with 30-megaton warhead (they have much better accuracy than envisioned in early 1960s, and thus could work with 1/3 warhead power).

 

[Michel Van]

The general idea behind AN602 was to demonstrate, that USSR is leading in nuclear weapon development as well as in missile & space technology.

Put it simple: Khrushchev wanted to show he has bigger one, as Kennedy has...

I suppose, it was planned to be used against super-hardened undergound bunkers, like NORAD HQ.

That would only work on ground impact.
with airburst 100MT could obliterate small country like Belgium or Large city
Also was 1960s soviet target system "inaccurate" therefor a 100MT guarantee assured destruction.

the USA hat far better ICBM target system to reduce the warhead to 4 MT for guarantee assured destruction.
(for Titan II ICBM)

 

[Dilandu]

Put it simple: Khrushchev wanted to show he has bigger one, as Kennedy has...

Partially true. But it needed to be viewed in historical context. 1957-1967 were the period of Soviet Union greatest relative prestige. It was viewed as great technological and industrial power, surpassing even the USA - while the American self-esteem was seriously damaged by Space Race. A demonstration, that USSR lead not only in rocketry, but also in nuclear weapons, was considered a pretty good option to persuade USA to limit further nuclear tests.

That would only work on ground impact.

Basically yes.

 

[Nik]

Brrr...
A mega-nuke in Q-ship's double-bottom was a very nasty 'Keep You Awake Nights' threat.
There'd be no '4-minute' sirens, as we expected any 'secret timer' to be 'instantaneous' to prevent disarming.
My family were situate in the 'Venn' of a triple-target.
The Mersey Docks.
The Wirral refineries. Also, 'hole in map' @ 'Capenhurst' where [REDACTED] nuke-stuff was done.
The Manchester docks.

During the Cuban Crisis, we feared dawn would come early, and from the South...
We cleared out 'under the stairs', un-nailed a few floor-boards to easier access crawl-space. Moved in camping stuff, tools, garden gear etc. Leaned ladders across door-way to mitigate roof collapse. Stashed food, drink, meds etc. Also, most of my school-books, my 'bookshelf' with geology reference, dictionary and prized 'Outline of Science', plus sundry Kiplings for amusement / ethics. Us kids 'nested' there. Given sirens, the 'Grown Ups' would crowd in.
Worst case, literally Flash !!--Boxer's Count--Upper Floor Blown Away, us kids would 'go to ground', dig our way out beneath the porch, survive. We had garden tools, seeds to plant, a 'Licence to Kill'.
Helluva burden to lay on even a bright adolescent...
Fortunately, sanity prevailed, and we learned to sleep easily again...
Although, six decades along, my wits still bear that existential scar...

 

[Yellow Palace]

Only a B-52 can carry two Flashback to Designated target.
however in time consider the B-52 as intermediate step replace by Supersonic Bomber like B-58 and XB-70.
and for operational ICBM was warhead too heavy

The weapons cited are all large enough that a B-52 could only carry one. The limit for tandem carriage seems to be a 13 to 14 foot long weapon, and these things were all in excess of 20 feet as well as requiring the full width of the weapons bay.

Although interestingly the B-70 did have a requirement to carry a 20,000lb Class A weapon, and its weapons bay restricted length to around 13 feet. So clearly someone was considering putting something big on it.

For me is unclear why the soviets try to build a 100 MT warhead with UR-500 ICBM

It's not entirely clear to me that they  did plan a 100 megaton weapon for the UR-500. Big, certainly, but possibly as small as 30-50 megatons. Soviet warhead design practice seems to have been more conservative than the US equivalent, with lower yields in the early weapons - leading to the US overestimating the effectiveness of the Soviet ICBM force in the 1960s.

Basically yes.

Although worth noting that once you get to a yield that large, you can't realistically avoid fallout. So there's no serious disincentive to contact fusing, given how much more effective it is at killing hard targets.

 

[NMaude]

They burn cleaner but it's not a case of no long-term radioactive contamination

Clean H-Bomb so nice it sound, it let temptations for politician to use them too easy.

H-bombs generate radioactive fallout by two mechanisms, one is from fission-products from the warhead's primary and secondary spark plug the other from a process called neutron activation where the neutron is the extremely energetic 14.1MeV fusion neutron generated by DT fusion.

McNamara stick to dirty H-bomb to guarantee Mutual Assured Destruction or MAD...

Dirty warheads are lighter than clean warheads of the same explosion yield.

Put it simple: Khrushchev wanted to show he has bigger one, as Kennedy has...

Khrushev's way saying "I have a very big dick" to Kennedy.

 

[chimeric oncogene]

They burn cleaner but it's not a case of no long-term radioactive contamination

Burst height for the gigaton bombs would have been a hundred km (almost LEO); the fallout would be limited to very small amounts of fission products scattered over very wide areas to the point of insignificance.

Now of course, these weapons were not super useful, because smog, cloud cover, rain etc would have large impacts on their effectiveness. Plus all they did was set stuff on fire. Sure, you might be able to smoke out some SS-20s from the Siberian taiga forests but it's not super reliable.

Rule of thumb as I understand it is that a hundred megatons burns Belgium and a thousand megatons fries France, so these were very indiscriminate, wide area, ecologically disastrous weapons regardless of their lack of fallout.

 

[Dilandu]

Now of course, these weapons were not super useful, because smog, cloud cover, rain etc would have large impacts on their effectiveness. Plus all they did was set stuff on fire. Sure, you might be able to smoke out some SS-20s from the Siberian taiga forests but it's not super reliable.

Well, the general idea was, that due to sheer size of the area covered by "nuclear pancake", it would cause the continental-scale firestorm below. So the small areas covered by thick clouds or rain would be mostly irrelevant; they would still be enfulged with flame, just a bit later.

 

[jeffb]

because smog, cloud cover, rain etc would have large impacts on their effectiveness. Plus all they did was set stuff on fire. Sure, you might be able to smoke out some SS-20s from the Siberian taiga forests but it's not super reliable.

Not exactly testable either. The US push for bigger warheads seemed to be focused more on cracking deeply buried facilities than causing widespread destruction.

Those sort of effects probably more easily (and reliably) achieved with a shower of smaller megaton (or less) class weapons because the fires would join up anyway.

 

[martinbayer]

Let's hope nuclear weapons use in actual conflicts on this planet will forever remain a two off event.

 

[Scott Kenny]

I don't think B83's were going to be pulled off B-52's because of parachute issues if the balloon goes up. I think the mission took priority over egress.

If a plane is carrying multiple weapons, surviving to deliver them all is part of the mission.

And depending on flight paths, dropping a multiple-megaton single bomb may not be the last thing in line.

As an example, a B-52 could carry 4x B28s and 8x SRAMs internally. Or even 1x B41 and 8x SRAMs. If you're getting into any weapon longer than 14ft you're talking only 1 in the bay and probably relying on SRAMs on the wings for defense suppression.

 

[Scott Kenny]

Let's hope nuclear weapons use in actual conflicts on this planet will forever remain a two off event.

Amen.

And yes, I think everyone here knows I'm a missile submarine veteran. Wanting to use those is NOT desired.

 

[martinbayer]

Amen.

And yes, I think everyone here knows I'm a missile submarine veteran. Wanting to use those is NOT desired.

I was actually not aware of that fact (but my wife would probably tell you that that's a chronic condition), but as a German, thank you for your service.

 

[Yellow Palace]

Dirty warheads are lighter than clean warheads of the same explosion yield.

There's very little military reason to minimise fallout, and a dirty Teller-Ulam device typically has two to three times the yield of a clean one.

Notably, though, there's very little military reason to maximise fallout either, and the RIPPLE concept promised very high yield/weight ratios as well as being inherently clean.

The US push for bigger warheads seemed to be focused more on cracking deeply buried facilities than causing widespread destruction.

I'm not so sure: the B41 wasn't suitable for laydown delivery, needed for high accuracy surface bursts to defeat hard targets, and the abortive 60 megaton Class A weapon requirement was explicitly required to crater runways in a counterforce role.

The later B53 and B83, yes, I'd agree that those had a significant hard-target defeat role.

Those sort of effects probably more easily (and reliably) achieved with a shower of smaller megaton (or less) class weapons because the fires would join up anyway.

It's not so much fires you're optimising, as blast effects. And there are some fun interactions between shockwaves there; none of the online circle-drawing weapons effects tools are capable of modelling that.

And that's not restricted to high-yield weapons, or even theoretical - the geography of Nagasaki funneled the blast in ways which resulted in some areas being more heavily damaged than others.

 

[chimeric oncogene]

Those sort of effects probably more easily (and reliably) achieved with a shower of smaller megaton (or less) class weapons because the fires would join up anyway.

It's not so much fires you're optimising, as blast effects.

Given the relatively limited resources actually put towards operationalizing the ripple design in the form of extremely large warheads, I doubt the operational concept for these weapons was thought through in great detail.

Neither the high altitude gigaton bomb or the gigaton laydown weapon (or the 300 megaton laydown bomb, or the 100 megaton earth penetrator described in the DUCC studies) were probably far along enough that the Air Force gave serious quantitative and analytical thought to their application in terms of tactics operations and doctrine.

What little we have is probably napkin sketches and lunch time discussions between weapons physicists and Air Force men and so on.

Attached is an excerpt from Phyllis Schafly's wingnut screed, STRIKE FROM SPACE A MEGADEATH MYSTERY. Given that I suspect there were many wing nuts in the weapons establishment who were also talking to Schafly (the father of the neutron bomb wrote his own wingnut screed at some point), we can probably have some idea of the ideas that must have been bouncing around those napkins.

In any case, once any serious thought was given to this sort of thing, and people started needing to put money behind their ideas, obviously these ideas did not withstand the test of common sense and cost effectiveness. Which is why we do not have gigaton bombs lofted by Doomsday Orions or 100 megaton earth penetrating weapons.

Strike from Space

Excursions into the history of atomic energy.

atomic-skies.blogspot.com

(Note also that the contiguous United States is approximately 7 million square kilometers; each of the gigaton weapons is expected to scorch about 2 million square kilometers or so, with an effect radius of perhaps 800 kilometers, which I would estimate means it's a ten gigaton sundial)

 

[Yellow Palace]

Given the relatively limited resources actually put towards operationalizing the ripple design in the form of extremely large warheads, I doubt the operational concept for these weapons was thought through and great detail.

Yes, I'm talking largely of weapons with maximum yields in the tens of megatons, rather than gigaton-class weapons which probably belong in science fiction. For those, blast is the primary damage mechanism, and thermal flash is at most a useful bonus effect, at least against military and urban-industrial targets. For anti-aircraft and anti-missile use, the results are different.

For what it's worth, even with RIPPLE yield/weight ratios, a gigaton weapon is going to weigh on the order of a hundred tonnes, which isn't deliverable by any sensible weapon system. I'm quite sure, though, that if the USSR had developed the R-56 or UR-700 for its space program, someone in the US intelligence community would have imagined they were planning such a thing.