AN UNEARTHLY SPECTACLE
The untold story of the world’s biggest nuclear bomb
By Alex Wellerstein, 10/29/21, Bulletin of Atomic Scientists

In the early hours of Oct 30, 1961, a bomber took off from
an airstrip in northern Russia & began its flight thru cloudy
skies over the frigid Arctic island of Novaya Zemlya. Slung
below the plane’s belly was a nuclear bomb the size of a
small school bus—the largest & most powerful bomb ever created.

At 11:32 a.m., the bombardier released the weapon. As the
bomb fell, an enormous parachute unfurled to slow its descent,
giving the pilot time to retreat to a safe distance. A minute
or so later, the bomb detonated. A cameraman watching from
the island recalled:

"A fire-red ball of enormous size rose & grew. It grew
larger & larger, & when it reached enormous size, it went
up. Behind it, like a funnel, the whole earth seemed to be
drawn in. The sight was fantastic, unreal, & the fireball
looked like some other planet. It was an unearthly spectacle!"

The flash alone lasted over a minute. The fireball expanded
to nearly 6 miles in diameter—large enough to include the
entire urban core of Washington or San Francisco, or all of
midtown & downtown Manhattan. Over several minutes it rose
& mushroomed into a massive cloud. Within ten minutes, it
had reached a height of 42 miles & a diameter of some 60 miles.
One civilian witness remarked that it was “as if the Earth
was killed.” Decades later, the weapon would be given the
name it's most commonly known by today: Tsar Bomba, meaning
“emperor bomb.”

Designed to have a max explosive yield of 100 million tons
(or 100 megatons) of TNT equivalent, the 60,000-lb monster
bomb was detonated at only half its strength. Still, at
50 megatons, it was over 3,300 times as powerful as the
atomic bomb that killed at least 70,000 people in Hiroshima,
& over 40 times as powerful as the largest nuclear bomb in
the US arsenal today. Its single test represents about 1/10
of the total yield of all nuclear weapons ever tested by
all nations.

At the time of its detonation, the Tsar Bomba held the
world’s attention, largely as an object of infamy,
recklessness, & terror. Within two years, though, the
Soviet Union & the US would sign & ratify the Limited
Test Ban Treaty, prohibiting atmospheric nuclear weapons
testing, & the 50-megaton bomb would fall into relative obscurity.

From the very beginning, the US sought to minimize the
importance of the 50-megaton test, & it became fashionable
in both the US & the former Soviet Union to dismiss it as
a political stunt with little technical or strategic
importance. But recently declassified files from the
Kennedy admin now indicate that the Tsar Bomba was taken
far more seriously as a weapon, & possibly as something to
emulate, than ever was indicated publicly. And memoirs from
former Soviet weapons workers, only recently available
outside Russia, make clear that the gigantic bomb’s place
in the history of Soviet thermonuclear weapons may be far
more important than has been appreciated. Sixty years after
the detonation, it’s now finally possible to piece together
a deeper understanding of the creation of the Tsar Bomba &
its broader impacts.

The Tsar Bomba isn't just a subject for history; some of
the same dynamics exist today. It isn't just the story of
a single weapon that was detonated six decades ago, but a
parable about political posturing & technical enablement
that applies just as acutely today. In a new era of nuclear
weapons & delivery competition, the Tsar Bomba is a potent
example of how nationalism, fear, & high-tech can combine
in a fashion that is ultimately dangerous, wasteful, & pointless.

From kilotons to megatons to gigatons
-----------------------------
Even before the first atomic bomb was built, scientists in
the US had conceived of an even larger weapon, the “Super,”
which would use the energy of a fission bomb to power nuclear
fusion reactions in the heavy hydrogen isotopes deuterium & tritium—resulting in a much more powerful weapon than one
fueled by fission alone. Such a weapon, they reasoned, could
be scaled up to the megaton range, a thousand-fold increase
over the kiloton weapons they were contemplating for WWII.
Los Alamos researchers were doing calculations on theoretical
fission-ignited fusion bombs with yields of 100 megatons by
Oct 1944.

But making the first hydrogen bombs took a bit more time
than that. Post-war attempts to rein in the arms race failed,
& the Soviet Union detonated its first atomic bomb in 1949.
By the end of that year, a tense debate over whether a crash
H-bomb program was the proper response to the loss of the
American nuclear monopoly had leaked into the public,
giving rise to speculation about the vast damage that could
be caused by still-hypothetical megaton weapons. It was easy
to apply scaling laws to see what the damage would be from
such weapons. The 20-kiloton “Fat Man” bomb used against
Nagasaki, for example, could devastate the downtown area of
a large American city like San Francisco, Los Angeles, or
New York. A single 10-megaton bomb, though, could destroy
entire metro areas, subjecting over a thousand square miles
to a crushing blast wave & searing heat, easily producing
casualties in the millions. The radioactivity produced
would also be multiplied many hundreds of times, creating
the possibility of vast contamination.

By the spring of 1951, Edward Teller & Stanislaw Ulam at
Los Alamos had developed their design for a workable H-bomb.
The idea was superficially simple: Use the radiation of an
exploding fission bomb (the “primary”) to compress a
special capsule that contained both fusionable & fissionable
materials (the “secondary”). A proof-of-concept device
(“Sausage”) was tested in Nov 1952, achieving an explosive
yield of 10 megatons. A more compact, weaponized version
(“Shrimp”) was detonated in March 1954 in the Castle Bravo
test, achieving a much higher yield than anticipated
(15 megatons, or 1,000 times as powerful as the bomb
dropped on Hiroshima) & surprising the scientists with more
radioactive fallout than expected (which required the
evacuation of occupied atolls downwind from the
Marshall Islands test site).

Only a few months later, in July 1954, Teller made it
clear he thought 15 megatons was child’s play. At a secret
meeting of the General Advisory Committee of the Atomic
Energy Commission, Teller broached, as he put it, “the
possibility of much bigger bangs.” At his Livermore lab,
he reported, they were working on two new weapon designs,
dubbed Gnomon & Sundial. Gnomon would be 1,000 megatons &
would be used like a “primary” to set off Sundial, which
would be 10,000 megatons. Most of Teller’s testimony
remains classified to this day, but other scientists at
the meeting recorded, after Teller had left, that they
were “shocked” by his proposal. “It would contaminate the
Earth,” one suggested. Physicist I. I. Rabi, by then an
experienced Teller skeptic, suggested it was probably
just an “advertising stunt.” But he was wrong; Livermore
would for several years continue working on Gnomon, at
least, & had even planned to test a prototype for the
device in Operation Redwing in 1956 (but the test never
took place).

All of which is to say that the idea of making hydrogen
bombs in the hundreds-of-megatons yield range was hardly
unusual in the late 50s. If anything, it was tame compared
to the gigaton ambitions of one of the H-bomb’s inventors.
It's hard to convey the damage of a gigaton bomb, because
at such yields many traditional scaling laws don't work
(the bomb blows a hole in the atmosphere, essentially).
However, a study from 1963 suggested that, if detonated
28 miles above the surface of the Earth, a 10,000-megaton
weapon could set fires over an area 500 miles in diameter.
Which is to say, an area about the size of France.

The Soviet Union had been interested in the Super for
about as long, having received espionage info about the
early American thermonuclear effort. The Soviets appear to
have made their own path to the hydrogen bomb, though,
first pursuing a single-stage design (“Sloika,” a reference
to a layered pastry), tested in 1953, that could “only” be
detonated at about half a megaton (though sub-megaton,
it'd still be 25 times as explosive as the Nagasaki bomb,
& capable of killing millions if used on a major metropolis).
In the spring of 1954, Andrei Sakharov, Yakov Zeldovich,
& Yuri Trutnev, along with other Soviet physicists,
developed their own version of a staged thermonuclear
weapon, called RDS-37. The details of this are still
somewhat cloudy, but it appears to have been a genuinely
indigenous development, & it resulted in the test of a
megaton-range weapon in 1955.

As in the US, there were those in the Soviet Union who
immediately began thinking of “bigger bangs.” In late
1955, Avraamiy Zavenyagin, a KGB general who was a
minister of the nuclear program, proposed scaling up the
program’s new H-bomb to a massive size. It'd be nothing
fundamentally innovative—the same RDS-37 design but with
a lot more fuel, to produce a yield in the “many tens of
megatons”; one document suggests 20-30 megatons. Work
began on the weapon, dubbed RDS-202, in 1956, with design
calculations made at Chelyabinsk-70 (the Soviet equivalent
of the Livermore weapons lab) & procurement orders issued
for the necessary materials.

The bomb’s physical dimensions would be gigantic: It would
weigh 24–26 tons, with an eventual length of 26 feet & a
diameter of over 6 feet. Making the parts of such an
oversized weapon proved almost beyond the capabilities of
existing machine shops. The largest, front part of the
casing alone required a “parquet” approach in which 1,520
smaller elements were welded together, & the casting of the
internal spherical shapes required new manufacturing techniques.

But acting rapidly, the scientists & technicians had the
bomb ready for testing in the fall of 1956 (Sakharov himself
signed off on its warhead design). However, uncertainties
about the possible effects of such a large weapon—& the
scientists’ inability to reliably predict meteorological
conditions that would affect both the distance of the blast
effect & the fallout—led Soviet officials to postpone the
test until additional studies could be done, which would
end up taking years. Zavenyagin himself died on the last
day of 1956, &, with him, so apparently did RDS-202. In
March 1957, the Soviet govt ordered that the project be put
in long-term storage, & in 1958 decided to dismantle &
recycle all the pieces of it. All that would remain in
storage was the massive casing, which had been painstakingly
engineered for its unusual ballistic properties.

Meanwhile, Soviet thermonuclear weapons design began to
improve dramatically. Two young physicists at Arzamas-16
(the Soviet Los Alamos), Yuri Trutnev & Yuri Babaev,
developed what they called a “new principle” for staged
thermonuclear weapons. Project 49, as it was called, focused
on optimizing the transfer of energy from the bomb’s primary
to its secondary. This, coupled with better primaries &
secondaries, allowed for a much more efficient warhead,
capable of getting much bigger “bangs” out of a given
weight & volume of material. Their new bomb design was
finally tested in Feb 1958, with great success. Igor
Kurchatov, the famed “father of the Soviet atomic bomb,”
reported that year to the Congress of the Communist Party
that now the Soviet Union had “even more powerful, more
advanced, more reliable, more compact & cheaper atomic &
hydrogen weapons.”

By the end of 1958, both the US & the Soviet Union would
agree to a voluntary Test Ban Moratorium. Their stockpiles
would still grow, but innovation in the arms race—at least
when it came to the warheads—was deliberately stifled by
the lack of nuclear testing. This would continue until
1961, when Soviet Premier Khrushchev decided, at last,
that Soviet nuclear testing should resume.

Khrushchev would claim, in his memoirs, that he was
pressured by the scientists & the military to resume
testing. But it's also clear from those around him that
he felt the need to look tough to the world—& to the newly
inaugurated President Kennedy, whom Khrushchev judged weak.
And the real instigator would be the crisis in Berlin,
which was coming to a head in 1961, & would only be
resolved with the construction of the city’s notorious
wall toward the end of the year.

The Soviet Union was also, it should be noted, in a
somewhat precarious strategic position. The Red Army was
huge & vast, & its nuclear arsenal was rapidly growing,
but its delivery vehicles didn't allow it to threaten the
US homeland directly & credibly. The Soviets could threaten
by proxy, to be sure. But the US had a many-fold advantage
in nuclear weapons, many of them ringed around the Soviet
borders. The Soviet Union had tested its first ICBMs, but
there were scarcely any deployed. These same tensions
would, in a few years, lead Khrushchev to base missiles
in Cuba, but prior to that they made Khrushchev desperate
to appear tough.

On July 10, 1961, Khrushchev summoned the nuclear scientists
from Arzamas-16 to the Kremlin, where he told them about his
plan to resume testing that fall. Andrei Sakharov argued
that further testing was unnecessary; Khrushchev was furious
at his impertinence & snapped: “Sakharov, don’t try to tell
us what to do or how to behave. We understand politics.
I’d be a jellyfish & not Chairman of the Council of
Ministers if I listened to people like Sakharov!”

Exactly how the idea of the 100-megaton device came up at
this meeting isn't entirely clear from the accounts, but it
sounds like Khrushchev asked the scientists for proposals
for future tests, & somebody (some authors say it was
Trutnev) proposed that they build & detonate a 100-megaton
bomb. Khrushchev seized upon the idea, reportedly announcing:
“Let the 100-megaton bomb hang over the capitalists like
a sword of Damocles!”

Later Russian accounts by participants claim Arzamas-16
scientists had been inspired, in part, by speculations
about gigantic, gigaton-range bombs in the foreign press
in May 1960. The physicist & designer Victor Adamski said
that Sakharov & others tried to immediately assess the
plausibility of the news reports, & came up with the schema
that was ultimately used for the Tsar Bomba. They'd
initially apparently planned to design a smaller experiment,
but they'd somehow come across the preserved casing from
the aborted RDS-202 bomb from 1956. The vastness of it
apparently inspired them to go for a full-size test. But
unlike the 1956 plan, they'd use the newest Project 49
insights in developing this new bomb, making it far more
sophisticated than a simple scaling-up of an old design;
it'd be over twice as powerful as RDS-202, despite being
the same dimensions & weight. Sakharov, in his memoirs,
said he'd been thinking about “the initiative,” as he
called it, well before any formal request was made.
It wasn't just about the megatonnage for its own sake;
it'd need to be “an absolute record,” so that, perhaps,
it'd be the last series of atmospheric tests ever requested.

The 100-megaton bomb would be known internally as Project
602. The speed of its development is beyond impressive in
retrospect: In a mere 4 months, the team would have to
develop an entirely new weapon design for a totally
untested yield range; build the device & fabricate the
fissionable & fusionable material into the correct shapes;
& devise a plan to safely test it. Sakharov would manage
the whole project, with Trutnev & Babaev doing much of the
design work, along with the young physicists Victor Adamski
& Yuri Smirnov. Little has been released about the details
of the design, but a few years ago two longtime participants
in the Soviet & Russian nuclear programs revealed that it
was what they called a “bifilar” design: There was a
“main” thermonuclear unit in the center, with two
“primaries” imploding it from either side (with a time
difference between the two detonations of no more than
0.1 microseconds). This seems plausible given the documentary
photos of the bomb released by Russia after the Cold War,
which definitely show one very compact “primary” bomb at
the front end of the case, & hint at another at the back
of the case. If this is true, it suggests that the 100-
megaton bomb design was quite different from most thermo-
nuclear weapons; there has never been a report of any
American bombs, for example, that use multiple,
simultaneous primaries.

Another Soviet weapons scientist, Leonid Feoktistov, from
the rival Chelyabinsk-70 lab (which engineered the
ballistics of the bomb), reported disappointment when he
later looked at the warhead design: “It soon became clear
that we're not talking about some kind of super-discovery,
but just about an increase in weight & size.” Adamski,
Smirnov, & Trutnev would disagree with this assessment
entirely: “The bomb’s design was far from simple. Although
it was based on already well-known principles, many things
could've happened, including a failure to achieve the
desired explosive yield. But our specialists made it so
that the bomb went off flawlessly.”

At the last minute, there were uncertainties about the
design. Evsei Rabinowich, a colleague of Sakharov’s, had
decided that the design wouldn't work as planned. Sakharov
disagreed. “Unfortunately,” Sakharov later recalled in his
memoirs, “we lacked the math tools I needed to prove this
(partly because we had departed from precedent in our drive
for a more powerful device).” In the end, Sakharov made
“some changes” in the design, to minimize the margin of
error, which were implemented only days before the test.

Sakharov also made one major change to the test plan.
Even though the test bomb was a 100-megaton design, it
wouldn't be a 100-megaton detonation. In most thermo-
nuclear weapons designs, at least half the yield comes
from a final stage in which non-fissile atoms of uranium
238 are induced to fission by the high-energy neutrons
produced by deuterium-tritium fusion reactions. Replacing
the uranium 238 with an inert substance, in this case
lead, would make the weapon half as powerful (50 megatons),
& it'd release far less fallout in the form of fission products.

Sakharov was already queasy about the long-term deaths
from nuclear fallout, & he wanted to minimize the excess
radioactivity produced by the test. In 1958, he had
calculated that for every megaton of even “clean” nuclear
weapons, there'd be some 6,600 premature deaths over the
next 8,000 years across the globe, owing to carbon atoms
in the atmosphere that would become radioactive under the
bomb’s neutron flux.

A few thousand deaths—even the 660,000 that he thought
would be the result of a 100-megaton test—would be a tiny
amount compared with the billions who'd live & die over
those millennia, but they were still deaths Sakharov
considered himself partially responsible for. Had he not
reduced its yield by half, the 100-megaton bomb would've
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% 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. Again, Sakharov
would later state that he believed that if this worked,
it could essentially end atmospheric nuclear testing: The
Soviets would be able to “squeeze everything out of this
[testing series] so that it would be the last one.”

In Aug 1961, Khrushchev summoned scientists to a secret
meeting at the Kremlin. A colonel stationed at Arzamas-16
was tasked with bringing a wooden dummy of the massive
bomb—considerably scaled down, but still large enough that
it required several officers to bring it into the conference
room. He later reported that, as the scientists briefed
Khrushchev, the Soviet leader “stroked the polished surface
of the model for a long time, & looked at the superbomb
with drunken eyes.” The colonel speculated that perhaps
Khrushchev believed the bomb “gave him unprecedented power
over the world.”

Announcing the test, denouncing the test
---------------------------------
On Aug 30, 1961, the Soviet Union issued a statement that
it was abandoning the test moratorium. It, of course,
blamed the US, claiming the Americans were on the threshold
of starting up nuclear testing underground, & emphasizing
the defensive nature of the Soviet arsenal. The statement
also referred to big bombs: “The Soviet Union has worked
out designs for creating a series of superpowerful nuclear
bombs of 20, 30, 50, & 100 million tons of TNT.” But it
didn't yet directly threaten to test weapons of such high yields.

The response from Kennedy & others was predictably negative
(acc. to one advisor who was there, the president’s first
reaction was “unprintable”). The Kennedy admin then agreed
that the US, too, would resume nuclear testing. The tests
the Atomic Energy Commission (AEC) had ready to go were
low-yield underground tests, which the White House thought
might “invite such adverse comment” when compared to the
larger Soviet tests “as to be unacceptable.” But AEC
Chairman Glenn Seaborg managed to convince Kennedy that it
was a bad idea to try to immediately test larger devices,
& the White House would later use this fallout-free series
of tests as a contrast to the multi-megaton Soviet test series.

The Soviet hints of 100-megaton bombs provoked furious
speculation in American newspapers, which reported
unattributed sources saying that the US could, if it wanted
to, build & test 100-megaton weapons of its own, but that
it chose not to. Some American scientists chimed in that
weapons of such size were “too big” to be practical—that
such a weapon would be strategically pointless. The
argument, which would come up again & again in discussion
of these bombs, was based on the way in which blast damage
scales with yield. A 100-megaton bomb releases 10 times
more energy than a 10-megaton bomb, but it doesn't do
10 times more damage. This is because the blast effects
of explosions scale as a cubic root, not linearly. So a
10-megaton bomb detonated at an optimal altitude might
do medium damage to a distance of 9.4 miles from ground
zero, but a 100-megaton bomb “only” does the same amount
of damage to 20.3 miles. In other words, a 100-megaton
explosion is only a little over twice as damaging as a
10-megaton bomb. The weight of nuclear weapons, though,
does roughly scale with their yield in a more linear fashion
(design sophistication can vary this a bit), so a 100-megaton
bomb weighs roughly 10 times more than a 10-megaton bomb, which
makes it much more difficult to deploy on a bomber or missile.

The details can get much more complicated, depending on
which effects one looks at (thermal radiation scales much
better than blast damage), but the point that would be
repeatedly made is that it's easier to deploy multiple
lower-yield weapons than to deploy more massive weapons
(& it's worth noting the absurdity of considering even
one-megaton weapons, capable of utterly destroying most
cities & many of their suburbs, to be “lower-yield”).

In late Aug 1961, John McCloy, director of the US
Disarmament Commission, reported publicly that, in a
meeting with Khrushchev, the Soviet premier had said that
they'd need to test a 100-megaton weapon to learn whether
their design worked. Soon after, the White House issued a
statement denouncing Soviet testing plans & arguing that
Soviet “threats of massive weapons” wouldn't be able to
“intimidate the world.” The White House recalled its
representative from nuclear-testing negotiations in Geneva,
& further talking points given to newspapers denounced
talk of the giant bomb & its possible testing as “atomic
blackmail” & “terrorism.” As Soviet nuclear testing began
at the start of Sept, the protests continued. The Soviet
test series was vigorous, with multiple tests per week,
& yields ranging from less than a kiloton upward to a
12.5-megaton bomb by mid-Oct.

Finally, in his introductory speech to the Convocation
of the 22nd Congress of the Communist Party of the Soviet
Union on Oct 17, Khrushchev made public his plan for the
Tsar Bomba:

"Since I've digressed from the prepared text, I might as
well say that the testing of our new nuclear weapons is
going on very successfully. We shall complete it very
soon—probably by the end of October. We shall evidently
round out the tests by exploding a hydrogen bomb equivalent
to 50 million tons of TNT. (Applause.) We've said that we
have a bomb as powerful as 100 million tons of TNT. And
we have it, too. But we're not gonna explode it, because,
even if exploded in the remotest of places, we're likely
to break our own windows. (Stormy applause.) We'll therefore
not do it yet. But by exploding the 50-million bomb, we
shall test the triggering device of the 100-million one.
However, God grant, as people said in the old days, that
we never have to explode those bombs over any territory.
That is our fondest dream! (Stormy applause.)"

The world response was immediate. The US, of course,
immediately denounced the plan as unnecessary: Even the
development of 100-megaton bombs didn't require a test of
50 megatons in strength, & the fact that the Soviets were
doing it anyway “could only serve some unconfessed
political purpose.” Newspapers picked up that the bomb
would be tested around Halloween (a holiday not celebrated
in the Soviet Union), & several editorial cartoons depicted
Khrushchev in appropriate garb: on a broomstick, sprinkling
fallout from a giant bomb; or as a trick-or-treater with a
massive bomb in his bag of candy. By Oct. 27, the UN had
passed a resolution that “solemnly appealed” to the Soviet
Union to refrain from testing a 50-megaton bomb.

All of this, of course, fell on deaf ears. The plan had
been to test the “superbomb” since July, & the scientists
at the Soviet weapons labs had finally prepared the warhead
& its ungainly ballistic casing. These were assembled &
shipped via a special railcar to northern Russia, where
they were hung underneath a Tu-95V bomber that had been
painted white to better reflect the thermal radiation of
the blast. All the while, cameramen filmed the work, to
create a documentary for Khrushchev to later show Communist
Party officials & to impress foreign visitors (the 30-min,
top-secret film, “Testing of a clean hydrogen bomb with a
capacity of 50 million tons,” was finally released by
Rosatom a few years back).

Sakharov & most of the weapons designers were not at the
test, but they knew it worked because the detonation
disrupted radio communications with the test site for
40 minutes. Despite being detonated low enough (about
13,000 feet) to be at risk of contacting the ground &
creating significant local fallout, the blast wave “bounced”
the fireball of the bomb upward. As a result, almost all
the fallout shot into the stratosphere, where it'd circle
in the northern latitudes for years before coming down.

The global denunciation was, again, swift. Not yet knowing
that the fission content of the bomb was deliberately
reduced, the US & others criticized the Soviet Union harshly
for its contribution to global fallout. The White House
said this was a political act, rather than a military one,
& emphasized that such weapons didn't change the balance of
power: “There's no mystery about producing a 50-megaton bomb
.... The US Govt considered this matter carefully several
years ago & concluded that such weapons wouldn't provide
an essential military capability.”

The Kennedy admin wasn’t bluffing about its ability to
produce a 50-megaton bomb. As already discussed, the US
had been looking at weapons in the 10- to 100-megaton
yield range for a long time & had even contemplated
weapons in the gigaton range.

The closest the US had previously come to weapons in what
they called the “very high-yield” category came in the
late 50s, when Strategic Air Command (SAC) pushed vigorously
for a 60-megaton bomb. Such a weapon was being eyed not only
for its city-destroying powers (which would be substantive),
but also for use in cracking open deeply-buried facilities—
such as those within mountains, like the bunker the US was
then building at Raven Rock to ensure “continuity of govt”
in the event of nuclear war. Gen. Thomas Power had designated
this weapon as SAC’s top priority in 1957. But its incredible
size increase over other weapons in the US arsenal attracted
internal criticism & scrutiny. In 1957, AEC Commissioner
Thomas Murray appealed to President Eisenhower directly as
to whether such a massively powerful weapon was necessary,
& whether it was consistent with “moral law with regard to
the moderate & discriminate use of force in warfare.” This
prompted Eisenhower to commission a study from the Pentagon
& AEC on the need for such a weapon, & they ultimately
concluded that it was probably “not appropriate” to develop
such a weapon, largely because they expected adverse publicity
both domestically & internationally. They concluded, however,
that the “moral aspects of using large weapons do not differ
from the use of any weapon having mass destruction potential.”

Despite this, SAC continued to push for the weapon, & expected
it to be tested as part of Operation Hardtack in 1958.
Eisenhower had, however, put a cap on total megatonnage for
the test series (15 megatons, or 1,000 times more powerful
than the bomb dropped on Hiroshima), and this scuttled the
test. Scientists at the Livermore weapons laboratory assured
SAC that they could provide them with two versions of such
a weapon without testing, if desired; the first would be a
25,000-lb bomb with a 60-megaton yield, the second a
22,000-lb bomb of 45-megaton yield.

A few months after Sputnik, in 1958, the US Air Force Chief
of Staff asked the AEC for a feasibility study of even
larger weapons—between 100 and 1,000 megatons in yield.
As an internal, once-secret Air Force history from 1967
reported: “The Air Staff concluded that it might be feasible
but not desirable to use a 1,000-megaton weapon. Since
lethal radioactivity might not be contained within the
confines of an enemy state & since it might be impractical
to even test such a weapon, the Air Force Council decided
in April 1959 to postpone establishing a position on the
issue.” Let that sink in: These were weapons too large for
even the Eisenhower-era Air Force.

The largest weapon that the US would ever field was also
developed during this same, heady period: the Mark 41
thermonuclear bomb, with a yield of “approx. 25 megatons.”
The USs has never formally declassified the exact yield of
the Mark 41. A Congressman first divulged the weapon’s high
yield a few days before the Soviet test, to reassure
America’s people & allies that the country had powerful
weapons of its own, & that each B-52 bomber could carry
around 50 megatons of firepower in two such bombs. Unnamed

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