In Search of a Bigger Boom

by Alex Wellerstein, published September 12th, 2012

The scientist Edward Teller, according to one account, kept a blackboard in his office at Los Alamos during World War II with a list of hypothetical nuclear weapons on it. The last item on his list was the largest one he could imagine. The method of "delivery" — weapon-designer jargon for how you get your bomb from here to there, the target — was listed as "Backyard." As the scientist who related this anecdote explained, "since that particular design would probably kill everyone on Earth, there was no use carting it anywhere."1

Edward Teller looking particularly Strangelovian. Via the Emilio Segrè Visual Archives, John Wheeler collection.

Teller was an inventive, creative person when it came to imagining new and previously unheard-of weapons. Not all of his ideas panned out, of course, but he rarely let that stop his enthusiasms for them. He was seemingly always in search of a bigger boom. During the Manhattan Project, he quickly tired of working on the "regular" atomic bomb — it just seemed too easy, a problem of engineering, not physics. From as early as 1942 he became obsessed with the idea of a Super bomb — the hydrogen bomb — a weapon of theoretically endless power.

(One side-effect of this at Los Alamos is that Teller passed much of his assigned work on the atomic bomb off to a subordinate: Klaus Fuchs.)

It took over a decade for the hydrogen bomb to come into existence. The reasons for the delay were technical as well as interpersonal. In short, though, Teller's initial plan — a bomb where you could just ignite an arbitrarily long candle of fusion fuel — wouldn't work, but it was hard to show that it wouldn't work. Shortly after abandoning that idea more or less completely, Teller, with the spur from Stan Ulam, came up with a new design.

The Teller-Ulam design allows you to link bombs to bombs to bomb. John Wheeler apparently dubbed this a "sausage" model, because of all of the links. Ted Taylor recounted that from very early on, it was clear you could have theoretically "an infinite number" of sub-bombs connected to make one giant bomb.

A few selected frames from Chuck Hansen's diagram about multi-stage hydrogen bombs, from his U.S. Nuclear Weapons: A Secret History. Drawing by Mike Wagnon.

The largest nuclear bomb ever detonated as the so-called "Tsar Bomba" of the Soviet Union. On 1961, it was exploded off the island of Novaya Zemlya, well within the Arctic Circle. It had an explosive equivalent to 50 million tons of TNT (megatons). It was only detonated at half-power -- the full-sized version would have been 100 megatons. It is thought to have been a three-stage bomb. By contrast, the the largest US bomb ever detonated was at the Castle BRAVO test in 1954, with 15 megatons yield. It was apparently "only" a two-stage bomb.

The dropping of the Tsar Bomba, 1961: an H-bomb the size of a school bus.

We usually talk about the Tsar Bomba as if it represented the absolute biggest boom ever contemplated, and a product of unique Soviet circumstances. We also talk about as if its giant size was completely impractical. Both of these notions are somewhat misleading:

1. The initial estimate for the explosive force of the Super bomb being contemplated during World War II was one equivalent to 100 million tons of TNT. As James Conant wrote to Vannevar Bush in 1944:

It seems that the possibility of inciting a thermonuclear reaction involving heavy hydrogen is somewhat less now than appeared at first sight two years ago. I had an hour's talk on this subject by the leading theoretical man at [Los Alamos]. The most hopeful procedure is to use tritium (the radioactive isotope of hydrogen made in a pile) as a sort of booster in the reaction, the fission bomb being used as the detonator and the reaction involving the atoms of liquid deuterium being the prime explosive. Such a gadget should produce an explosion equivalent to 100,000,000 tons of TNT.2

Teller was aiming for a Tsar Bomba from the very beginning. Whether they would have supported dropping such a weapon on Hiroshima, were it available, is something worth contemplating.

2. Both the US and the USSR looked into designing 100 megaton warheads that would fit onto ICBMs. The fact that the Tsar Bomba was so large doesn't mean that such a design had to be so large. (Or that being large necessarily would keep it from being put on the tip of a giant missile.) Neither went forward with these.

A US MK 41 hydrogen bomb.

But remember that the original Tsar Bomba was actually tested at 50 megatons, which was bad enough, right? Both the US and the Soviet Union fielded warheads with maximum yields of 25 megatons. The US Mk-41, of which some 500 were produced, and the Soviet  SS-18 Mod 2 missiles were pretty big booms for everyday use. (The qualitative differences between a 50 megaton weapon and a 25 megaton weapon aren't that large, because the effects are volumetric.)

3. Far larger weapons were contemplated. By who else? Our friend Edward Teller.

In the summer of 1954, representatives from Los Alamos and the new Livermore lab met with the General Advisory Committee to the U.S. Atomic Energy Commission. Operation Castle had just been conducted and had proven two things: 1. very large (10-15 megaton or so), deliverable hydrogen bombs could be produced with dry fusion fuel; 2. Livermore still couldn't design successful nuclear weapons.

Norris Bradbury, director of Los Alamos, gave the GAC a little rant on the US's current "philosophy of weapon design." The problem, Bradbury argued, was that the US had an attitude of "we don't know what we want to do but want to be able to do anything." This was, he felt, "no longer relevant or appropriate." The answer would be to get very definite specifications as to exactly what kinds of weapons would be most useful for military purposes and to just mass produce a lot of them. He figured that the strategic end of the nuclear scale had been pretty much fleshed out — if you can routinely make easily deliverable warheads with a 3 megaton yield, what else do you need? All diversification, he argued, should be on the lower end of the spectrum: tactical nuclear weapons.

Edward Teller and Enrico Fermi, 1951. Courtesy of the Emilio Segrè Visual Archives.

When Teller met with the GAC, he also pushed for smaller bombs, but he thought there was still plenty of room on the high end of the scale. To be fair, Teller was probably feeling somewhat wounded: Livermore's one H-bomb design at Castle had been a dud, and the AEC had cancelled another one of his designs that was based on the same principle. So he did what only Edward Teller could do: he tried to raise the ante, to be the bold idea man. Cancel my H-bomb? How about this: he proposed a 10,000 megaton design.

Which is to say, a 10 gigaton design. Which is to say, a bomb that would detonate with an explosive power some 670,000 times the bomb that was dropped on Hiroshima.3

If he was trying to shock the GAC, it worked. From the minutes of the meeting:

Dr. Fisk said he felt the Committee could endorse [Livermore's] small weapon program. He was concerned, however, about Dr. Teller's 10,000 MT gadget and wondered what fraction of the Laboratory's effort was being expended on the [deleted]. Mr. Whitman had been shocked by the thought of a 10,000 MT; it would contaminate the earth.4

The "deleted" portion above is probably the names of two of the devices proposed — according to Chuck Hansen, these were GNOMON and SUNDIAL. Things that cast shadows.

The Chairman of the GAC at this time, I.I. Rabi, was no Teller fan (he is reported to have said that "it would have been a better world without Teller"), and no fan of big bombs just for the sake of them. His reaction to Teller's 10 gigaton proposal?

Dr. Rabi's reaction was that the talk about this device was an advertising stunt, and not to be taken too seriously.

Don't listen to Teller, he's just trying to rile you. Edward Teller: trolling the GAC. A 10,000 megaton weapon, by my estimation, would be powerful enough to set all of New England on fire. Or most of California. Or all of the UK and Ireland. Or all of France. Or all of Germany. Or both North and South Korea. And so on.

"Don't Fence My Baby In." Cartoon by Bill Mauldin, Chicago Sun-Times, 1963.

In 1949, Rabi had, along with Enrico Fermi, written up a Minority Annex to the GAC's report recommending against the creation of the hydrogen bomb. The crux of their argument was thus:

Let it be clearly realized that this is a super weapon; it is in a totally different category from an atomic bomb. The reason for developing such super bombs would be to have the capacity to devastate a vast area with a single bomb. Its use would involve a decision to slaughter a vast number of civilians. We are alarmed as to the possible global effects of the radioactivity generated by the explosion of a few super bombs of conceivable magnitude. If super bombs will work at all, there is no inherent limit in the destructive power that may be attained with them. Therefore, a super bomb might become a weapon of genocide.

If that doesn't apply to a 10,000 megaton bomb, what does it apply to?

Was Teller serious about the 10 gigaton design? I asked a scientist who worked with Teller back in the day and knew him well. His take: "I don't doubt that Teller was serious about the 10,000 MT bomb. Until the next enthusiasm took over." In this sense, perhaps Rabi was right: if we don't encourage him, he'll move on to something else. Like hydrogen bombs small enough to fit onto submarine-launched missiles, for example.

It's hard not to wonder what motivates a man to make bigger and bigger and bigger bombs. Was it a genuine feeling that it would increase American or world security? Or was it just ambition? I'm inclined to see it as the latter, personally: a desire to push the envelope, to push for the bigger impact, the biggest boom — even into the territory of the dangerously absurd, the realm of self-parody.

  1. Robert Serber, The Los Alamos primer: The first lectures on how to build an atomic bomb (Berkeley: University of California Press, 1992), page 4, fn. 2. []
  2. Letter dated October 20, 1944 from James B. Conant to Vannevar Bush, Subject: Possibilities of a Super Bomb. Vannevar Bush-James B. Conant Files, Records of the Office of Scientific Research & Development, S-1, NARA, Record Group 227, folder 3. Quoted from Chuck Hansen, The swords of Armageddon: U.S. nuclear weapons development since 1945 (Sunnyvale, Calif.: Chukelea Publications, 1995), III-17. []
  3. Actually, if you take the Hiroshima yield to be 15 kilotons, it comes out to a nice round 666,666 times the strength of the Hiroshima bomb. But the precision there seemed arbitrary and the symbolism seemed distracting, so I'm relegating this to just a footnote. []
  4. Minutes of the Forty-First Meeting of the General Advisory Committee to the U.S. Atomic Energy Commission, July 12-15, 1954, on p. 55. []

24 Responses to “In Search of a Bigger Boom”

  1. Charles Day says:

    A 10-GT bomb could prove useful if humanity, faced with a zombie pandemic, had to abandon Earth for its space colonies and wipe out the zombies that remain. On second thought, that tactic might not work. A new breed of super mutant zombies could be the result.

  2. Nuclear Tan says:

    Teller was the nutty professor 10 gig bombs, space based X-ray lasers and brilliant pebbles is the kind of stuff you’d expect to find in the diary of a madman. I never understood how such a brilliant man couldn’t realize that his SDI ideas could have shifted the preferred delivery system from missiles to cargo ships. I wonder if Teller’s dream of an extinction level gadget helped fuel Oppenheimer’s reluctance to work on the “Super”?

  3. lord of light says:

    SUNDIAL was meant to have a 10gt yield,Gnomon only 1Gt. Things not fully such as you are described :

    1.Sundial was meant to be a “2-stage” 1000mt Alarm Clock,so its also dirtiest bomb.
    2.Livermore in reality worked on these designs -Gnomon group existed at UCRL up to August 1955( York letter to Starbird ,Sep.2,1955 in the AEC nuclear power for rockets – report to the general manager by the director of military application).At this time UCRL probably not worked at any other tn device.Report of DMA- Technical estimates relating to future weapons,8 June,1955 , described ultra-high yield things -Gnomon ,TAV ,Sundial.All data is removed.For Gnomon and Tav tests were contemplated (but not planned at this time,in Oct.1954 LLNL thought that it may be possible to test Gnomon in 1956) ,but not for Sundial.Actually Hansen description of Alarm Clock is wrong,because calculation have been run on it in 1947 (La-5647-MS) ,in 1953-1954 calculation was done on Maniac on Super, NOT Alarm Clock.

    Results on Alarm Clock reported in La-645,Remarks on Alarm Clock and La-648,Alarm Clock integrations.Ordinary Alarm Clock was 40-100 tons,which meant that Sundial’s mass was ~7000 tons-so airburst impossible.In the second version of the 41st Minutes Teller’s remark declassified that gadget would not present any problem aside from the Gnomon and if the latter begins to look good Livermore may want to test it.
    There list of reports stated that these were declassified,there many La -and UCRL- reports ,for example UCRL-4374 ,Weapon development during August 1955.No.1 (in which undoubtedly Gnomon and Sundial described). Where to your knowledge these documents ?
    TAV it seems to have 2000 mt yield ,since as Mk21 was 19 megatons ( Mk21 yield declassified in history of 15th Air Force ,Jan-June 1956,Chap.3. development of atomic capability),I’m believe that TAV was Mk21 or 36 with 2 further fusion stages.

    • The only things I include are things I have sources for; if you have more sources or citations on this, send them my way, I’d be interested in seeing them!

    • Wotan says:

      I red in Rhode’s Dark Sun that the Alarm Clock configuration has an upper yield limit (in the order of megatons?) and only with the Teller-Ulam staging is possibile to scale the yield to very high levels, but i’m not sure what “two-stage alarm-clock” means: Instead of a conventional boosted primary there’s an Alarm-clock like primary followed by one (or more) fusion secondary?.

      Alex, i hope you’ll do another post on Sundial/Gnomon and similar very high yield projects, there’s very little info online about them, but they make Project Pluto looks reasonable 😉

      • My understanding is that any “Alarm Clock” design would have an upper-yield. I seem to recall reading somewhere that the Soviets developed 1 Mt version of essentially the same idea, though I can’t recall exactly where I saw that. Still a pretty big boom.

        As for a two-stage “Alarm Clock” — no clue. You could imagine an “Alarm Clock” as a very big primary, or even as a secondary in and of itself (not too far from Ulam’s original staging idea). But I don’t really know.

        I’ve recently sent out for some new documents on the US high-yield designs, though I don’t know if anything on GNOMON or SUNDIAL will be in there. I’m very curious about such things, though.

  4. The 10GT weapon really would have been BACKYARD. At 6MT/tonne (the upper bound for thermonuclear weapons) it would have weighed 1667 tonnes. Even the smaller 1GT would be 167 tonnes which might have been ship or sub transportable.

    For the curious at least NUKEMAP can do the effects scaling for a 10,000,000kT bomb in Washington, DC. The fireball would yield up 75% of it’s energy in about 280 seconds or so. That’s 5 minutes of 12 mile diameter fireball glow.

    I wonder what the optimum detonation height is? Only joking. Clearly it’s zero feet as you can’t fly with a 1667 tonne weapon. You can’t really put it on a ship unless you build something like an aircraft carrier for it. It wouldn’t really matter since it would punch through the atmosphere on detonation.

    LANL’s 1GT TAV I’ve seen mentioned on here in comments and in a couple of places the net. Who was working on that one? Not Teller as he was at Livermore (I presume, wasn’t he?). It seems someone in the hierarchy was at least a little serious about gigaton weapons. Or did TAV move labs and turn into GNOMON and SUNDIAL?

  5. lord of light says:

    TAV appeared later,around Nov.1954., there was Carson Mark who proposed this -“Although LASL not now engaged in any inquires into this ,Mark said he saw not reason why the 2-stage approach could not extrapolated to a point where weapons might give yields in the begaton (i.e.gigaton) range….In principle ,at least ,however it appears perfectly feasible to design a 2-stage which might be the size of submarine and then exploded with resultant tidal waves. …Sensitive information removed”

    Memo for file from J.K.Mansfield ,subjet trip to LASL and Livermore,October,26,1954.In this source also noted that Livermore worked on Sundial and possible Gnomon test in 1956.This is footnote from 2st Hansen’s Swords.

    Whether or not he described Tav as size of submarine unclear ,but numerical value of letter TAV-400.

    There also sources of possible interest on Opennet:



    There was a typo- UCRL-4374.Weapon development during July,1954.No.1.

  6. Mike Lehman says:

    Strangelovian indeed.

    From our view, it’s difficult to think about this sort of thing as anything other than insanity. Keep in mind that that these discussions are taking place right after the CASTLE series, while the AEC was still stonewalling on BRAVO’s fallout after the Lucky Dragon incident occurred. That report wasn’t released until 1955 and settled nothing as far as anyone but the AEC was concerned, in fact threw gasoline on the fire after the map of BRAVO’s fallout was superimposed on the US East Coast. Things changed.

    There may be some nomenclature confusion going on here. When we’re talking the highest yield deployed US weapon at 19 Mt, I think it was the Mk17/Mk24, not the Mk 21/Mk26 at ~4 Mt? In any case, 19 Mt was the high water mark of the Air Force’s drive for high yield weapons, which cost Oppenheimer his career and prodded the Soviets to also set such weapons as among their goals. That’s a complex situation I won’t try to unravel here. My point is that, while the Mk17/24 was fielded, it also quickly became obsolete as only the B-36 could carry it. The weapon and plane were retired together by ~1960 IIRC. Why?

    Fallout took the wind out of the sails of high yield weaponry after 1955, despite some deadenders (never did that word fit so well) who insisted the US needed such a weapon. Eisenhower put his foot down on further development of such high-yield weapons. After the Mk17/24 was retired, the highest yield weapon in the inventory then was Mk53/W-53 family at 9 Mt

    Was this simply a politically astute decision based on public reaction to such weapons? Well, credit is definitely due there, of course, as incomplete a project as nuclear disarmament remains today. On the other hand, there were a strong set of empirical reasons that fallout brought to the table to cause Teller’s troubling fantasies to wither within the US national security bureaucracy. The first effects were seen in Ike’s decision to place limits on high-yield weapons.

    But more importantly, one has to consider the almost total lack of utility of weapons the size of submarines that could destroy Europe or the East Coast. Sure, some fool wrote some sort of military requirement somewhere that probably further encouraged Teller to follow his star, but wiser heads began to prevail within the government, both civilian and military. Fallout changed everything, once you start considering the consequences of such enormous yields. Instant nuclear winter/fall/or whatever you think would occur after, plus there goes the human gene pool.

    So what is the military utility of a weapon you just might regret setting off, even if it was in another hemisphere? Deterrence, pure and simple. There is no other use for such a thing other than as part of a mutual suicide pact once you push that button. Not very effective in actually fighting a war, don’t you know?

    Instead of following the path the Air Force fought so hard for — and at such cost to Oppenheimer, shortly after CASTLE US weapons development turned firmly back toward finishing the stockpile development program of a diverse set of devices, many tactical, set in motion in 1950 when the not-yet-disgraced Oppie was the GAC chair. Meanwhile, Teller ended up continuing to be rewarded with his boondoggle at LL, a costly duplication of effort that had its roots in the Air Force’s desire to isolate Oppie and shower their golden ‘super’ one, Teller, with lots of money that was wasted before Teller’s rump group ever got a successful shot off.

    Thank goodness all we ended up with out of that mess was a really great movie…Dr. Strangelove, in which the wisdom of suicide pacts via gigaton yield weapons was thoroughly skewered.

  7. […] This fundamental ambivalence of concept shoots through all of our cultural depictions of deterrence, as well. It’s not a surprise that most of the defense intellectuals depicted in books and films are simultaneously both of these things. Dr. Strangelove is of course the canonical, genre-defining case: coldly rational, but also completely psychotic. Not too far off… […]

  8. lord of light says:

    Not, Mk21 was a 19-megaton weapon and Mk36Y1 have a higher yield than Mk17:

    “Mk21 was designed to achieve maximum reliability with minimum surveillance in storage .It is 148 inches in length ,has diameter of 58.47 inches ,weighs approximately 17,600 pounds and yields an explosive force of 19 megatons.The insertion of the thermonuclear capsule into the pit of “Cobra”…”

    History of 15th Air Force.January-June 1956.Chapter III.The development of atomic capability .p.29.(282).

    “The Mk21 ,a thermonuclear device with an explosive force of 19 megatons fell in the latter category.”

    Navajo was a test of Mk-21C -4.5-4.7mt, but predicted yield was 6mt (~1/3 of full yield) –


    In Report of NSC Ad Hoc Working Group on the Technical Feasibility of a Cessation of Nuclear Testing,” 27 March 1958
    stated in section Clean weapons -“The US have in its stockpile a clean weapon yielding 6 megatons (compared to 19 megatons in the standard version of this warhead ..).

    But US not have any clean weapon at this time – SC-M-67-662-3434-11.Mks 21-22-26-36 at

    So,they probably described 21 not 36.
    And Mk17 have a smaller yield than Mk36Y1 -“Mk17 mod 1 weapons were retired between November 1956 and August 1957.The Mk 17 mod2′ s were retired between August and October 1957 ,since Mk 36 weapons were then entering the stockpile in large enough quantities to fully support military plans for weapons of this yield range.The Mk36 provided a HIGHER yield than Mk17 and at much smaller weight.”

    History of early TN weapons .Mks 14,15,16,17.Sc-M-67-661.

    Mk36 described as enriched Mk21 in Bowen &Little study.Sybil Francis stated 25mt for Mk17/24.

    Mk36 only originated in 1955 ,so this why I’m believe that TAV was Mk21 with 2 further fusion stages and ~2Gt.

    4-5 mt for Mk21 and 9-10mt for Mk36,and 940 produced for MK36 were ,probably a public numbers from 80-s.US have 20,900 megatons at June 30,1960-so 940 impossible.,as well 500 mk-41s also impossible. DOE stated that only basic information about the stockpile have been declassified.

  9. Doc Strangelove says:

    Regarding gigaton mines I found this piece on FAS Blog:

    You may pay particular attention to the second commentary by a user nicknamed “stanley tweedle”. As far as I understand is there no limit of the yield of a multi stage device. Even a teraton mine is possible. This must be the backyard device Teller was contemplating. A thing like this would easily damage the earth’s crust, a global killer.

  10. […] without me sounding like a madman, because the “such things” in this case are monstrous nuclear weapons or other disturbing legacies of the nuclear age. Some of my early NUKEMAP interviews came off […]

  11. Chris Barrett says:

    I think there could be an authenticity problem with the Los Alamos classified document header image shown in the article on this site about weapon-induced weather -such as rainstorms – increasing the lethality of the weapon. I believe that the lab was called one of “LASL”, “Los Alamos Laboratory”, or “Project-Y” in 1945, but certainly *not* LANL. In the image it shows “LANL”, which was what LASL was renamed some 30 odd years later and remains so named today. “LANL” would never have been used on a document in 1945. It at least requires an explanation in the image’s description-related text to be credible.

    • Hi Chris: The “LANL” at the top of the document linked-to here, along with the “RG 326 ATOMIC ENERGY COMMISSION,” are stamps that were added later. (RG 326 is an explicit reference to the NARA reference group.) They are indicators of where the physical records are stored (or were stored at one point in their existence), and were not applied contemporaneously with its creation. They are just indicators of where that particular paper copy was located, prior to it being photocopied or microfilmed or whatever, long before it was ever scanned as a grainy PDF. (It comes from a government document repository, where many such documents are hoarded, often with nothing more than such stamps to indicate where they at one point originally lived.) Incidentally, the same archive has another copy of the same document (identical except for redactions) as well. The exact path of this document, from its creation to its being in my hands, is not entirely clear to me, but I have no doubts as to its authenticity. Hope that clears it up a bit!

  12. Chris Barrett says:

    Alex, Thanks.

  13. […] the odds of them being built, much less used, are pretty much nil. Hooray for us! (Nobody tell Edward.) But as you slide down the scale of cheapness, you slide into the area of likelihood — if not […]

  14. Jim-Bob says:

    The more I read about Edward Teller, the more convinced I become that he either had Asperger’s Syndrome or high functioning autism. You will never fully understand his motivations outside of this because nuclear weapons were his obsessive “special interest”. For him, the human element did not really come in to play when he was working on these things because it was an intellectual challenge. Being on the borders of the autistic spectrum myself (likely Asperger’s), I understand his motivations and the apparent naivete that his actions represent. When you get caught up in a subject you lose all perspective and figuring out or learning new things become a sort of high. He may have understood the human cost in terms of a set of data points but wanted to see his new “toy” work so badly that he failed to understand the basic humanity of those it would impact. Later in life, when he was no longer in the moment, he was able to reflect and logically arrive at a more normal human reaction to what he had done. I don’t really see him as evil though, just naive. However, that doesn’t make the results of his actions any less horrific.

  15. […] Teller is a particularly important, and reviled, figure in this discussion. I.I. Rabi, one of Teller’s colleagues on the Manhattan Project, is said to have reflected, “it would have been a better world without Teller.” In the 1950s, Teller was talking about a 10,000-megaton bomb — that’s 670,000 Hiroshimas, in case you are counting at home. On his blackboard at Los Alamos, Teller reportedly had a device so large that it would kill everyone on earth. He named it “Backyard,” since there would be no need to move it anywhere. (Alex Wellerstein has a wonderful blog post on Teller, from which much of this is drawn, entitled “In Search of a Bigger Boom.”) […]