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Nuclear weapon yield
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<h2 id="examples-of-nuclear-weapon-yields">Examples of nuclear weapon yields</h2> <p>In order of increasing yield (most yield figures are approximate): </p> <table><tbody><tr><th rowspan="2">Bomb</th><th colspan="2">Yield</th><th rowspan="2">Notes</th><th rowspan="2">Weight of nuclear material</th></tr><tr><th>kt TNT</th><th>TJ</th></tr><tr><td><a href="/facts/Davy_Crockett_(nuclear_device)/kDyeU6Hg">Davy Crockett</a></td><td>0.02</td><td>0.084</td><td><a href="/facts/Variable_yield/kRGpQ7Js">Variable yield</a> tactical nuclear weapon—mass only 23 kg (51 lb), lightest ever deployed by the United States (same warhead as <a href="/facts/Special_Atomic_Demolition_Munition/rtfS3edR">Special Atomic Demolition Munition</a> and <a href="/facts/AIM-26_Falcon/1rCsVJ9E">GAR-11 Nuclear Falcon missile</a>).</td><td></td></tr><tr><td><a href="/facts/AIR-2_Genie/gIhUzWUm">AIR-2 Genie</a></td><td>1.5</td><td>6.3</td><td>An unguided <a href="/facts/Air-to-air_rocket/9IaP5n01">air-to-air rocket</a> armed with a <a href="/facts/W25_(nuclear_warhead)/s95LBoWX">W25</a> <a href="/facts/Nuclear_warhead/QVdBcMdm">nuclear warhead</a> developed to intercept bomber squadrons.</td><td>Total weight of nuclear material and bomb was 98.8 - 100.2 kg</td></tr><tr><td>Hiroshima's "<a href="/facts/Little_Boy/4XAsA7xT">Little Boy</a>" <a href="/facts/Gravity_bomb/Pxd1KvCE">gravity bomb</a></td><td>13–18</td><td>54–75</td><td>Gun type <a href="/facts/Uranium-235/pe0RznDM">uranium-235</a> fission bomb (the first of the two nuclear weapons that have been used in warfare).</td><td>64 kg of Uranium-235, about 1.38% of the uranium fissioned</td></tr><tr><td>Nagasaki's "<a href="/facts/Fat_Man/2vlxvS9a">Fat Man</a>" gravity bomb</td><td>19–23</td><td>79–96</td><td>Implosion type <a href="/facts/Plutonium-239/eRobTXos">plutonium-239</a> fission bomb (the second of the two nuclear weapons used in warfare).</td><td>6.2 kg of Plutonium-239, about 1 kg fissioned</td></tr><tr><td><a href="/facts/W76/TAkfe2Yj">W76</a> warhead</td><td>100</td><td>420</td><td>Twelve of these may be in a <a href="/facts/MIRV/cmzWwXxy">MIRVed</a> <a href="/facts/Trident_missile/5CL2CCGA">Trident II missile</a>; treaty limited to eight.</td><td></td></tr><tr><td><a href="/facts/W87/DnadI0mu">W87</a> warhead</td><td>300</td><td>1,300</td><td>Ten of these were in a <a href="/facts/MIRV/cmzWwXxy">MIRVed</a> <a href="/facts/LGM-118A_Peacekeeper/HpETRcB9">LGM-118A Peacekeeper</a>.</td><td></td></tr><tr><td><a href="/facts/W88/XnwYMSXq">W88</a> warhead</td><td>475</td><td>1,990</td><td>Eight of these may be in a Trident II missile.</td><td></td></tr><tr><td><a href="/facts/Ivy_King/ljgMS1vL">Ivy King</a> device</td><td>500</td><td>2,100</td><td>Most powerful US pure fission bomb,<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> 60 kg uranium, implosion type. Never deployed.</td><td>60 kg of Highly enriched uranium (HEU)</td></tr><tr><td><a href="/facts/Orange_Herald/rzYHlzsQ">Orange Herald Small</a></td><td>800</td><td>3,300</td><td>Most powerful tested UK <a href="/facts/Boosted_fission_weapon/U11GQ2mf">boosted fission missile warhead</a>.</td><td>117 kg of Uranium-235</td></tr><tr><td><a href="/facts/B83_nuclear_bomb/jvcLw3X4">B83 nuclear bomb</a></td><td>1,200</td><td>5,000</td><td>Variable yield weapon, most powerful US weapon in active service.</td><td></td></tr><tr><td><a href="/facts/B53_nuclear_bomb/r0n4zhHN">B53 nuclear bomb</a></td><td>9,000</td><td>38,000</td><td>Was the most powerful US bomb in active service until 1997. 50 were retained as part of the "Hedge" portion of the <a href="/facts/Enduring_Stockpile/YflCk4wK">Enduring Stockpile</a> until completely dismantled in 2011.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> The Mod 11 variant of the <a href="/facts/B61_nuclear_bomb/C2YTuKyy">B61</a> replaced the B53 in the bunker busting role. The W53 warhead from the weapon was used on the <a href="/facts/LGM-25C_Titan_II/xrfcxWFj">Titan II Missile</a> until the system was decommissioned in 1987.</td><td></td></tr><tr><td><a href="/facts/Castle_Bravo/R2F4BRFf">Castle Bravo</a> device</td><td>15,000</td><td>63,000</td><td>Most powerful US test.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> Never deployed.</td><td>400 kg of Lithium-6 deuteride</td></tr><tr><td>EC17/Mk-17, the EC24/Mk-24, and the <a href="/facts/B41_nuclear_bomb/bNSostjy">B41</a> (Mk-41)</td><td>25,000</td><td>100,000</td><td>Most powerful US weapons ever: 25 megatonnes of TNT (100 PJ); the Mk-17 was also the largest by area square footage and mass cubic footage: about 20 short tons (18,000 kg). The Mk-41 or <a href="/facts/B41_nuclear_bomb/bNSostjy">B41</a> had a mass of 4800 kg and yield of 25 Mt; this equates to being the highest yield-to-weight weapon ever mass produced. All were gravity bombs carried by the <a href="/facts/B-36/GUwVqxkc">B-36</a> bomber (retired by 1957).</td><td></td></tr><tr><td>The entire <a href="/facts/Operation_Castle/95dt0XsF">Operation Castle</a> nuclear test series</td><td>48,200</td><td>202,000</td><td>The highest-yielding test series conducted by the US.</td><td></td></tr><tr><td><a href="/facts/Tsar_Bomba/qbjpPwN2">Tsar Bomba</a> device</td><td>50,000</td><td>210,000</td><td>USSR, most powerful nuclear weapon ever detonated, yield of 50 megatonnes, (50 million tonnes of TNT). In its "final" form (i.e. with a <a href="/facts/Depleted_uranium/oKGvpUlW">depleted uranium</a> <a href="/facts/Tamper_(nuclear_weapon)/yDkgmcrE">tamper</a> instead of one made of <a href="/facts/Lead/EYljasJN">lead</a>) it would have been 100 megatonnes.</td><td></td></tr><tr><td>All <a href="/facts/Nuclear_testing/s2srGDFP">nuclear testing</a> as of 1996</td><td>510,300</td><td>2,135,000</td><td>Total energy expended during all nuclear testing.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a></td></tr></tbody></table> <p>In comparison, the blast yield of the <a href="/facts/GBU-43_Massive_Ordnance_Air_Blast_bomb/HIsckd5Q">GBU-43 Massive Ordnance Air Blast bomb</a> is 0.011 kt, and that of the <a href="/facts/Oklahoma_City_bombing/BwmNQQ5u">Oklahoma City bombing</a>, using a truck-based fertilizer bomb, was 0.002 kt. The estimated strength of the <a href="/facts/2020_Beirut_explosions/T6Sd0Thd">explosion at the Port of Beirut</a> is 0.3-0.5 kt.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> Most <a href="/facts/List_of_the_largest_artificial_non-nuclear_explosions/DXj8nBto">artificial non-nuclear explosions</a> are considerably smaller than even what are considered to be very small nuclear weapons. </p> <h3>Yield limits</h3> <p>The yield-to-mass ratio is the amount of weapon yield compared to the mass of the weapon. The highest achieved values are somewhat lower, and the value tends to be lower for smaller, lighter weapons, of the sort that are emphasized in today's arsenals, designed for efficient MIRV use or delivery by cruise missile systems. </p> <ul><li>The 25 Mt yield option reported for the <a href="/facts/B41_nuclear_bomb/bNSostjy">B41</a> would give it a yield-to-mass ratio of 5.1 megatonnes of TNT per tonne. While this would require a far greater efficiency than any other current U.S. weapon (at least 40% efficiency in a fusion fuel of lithium deuteride), this was apparently attainable, probably by the use of higher than normal <a href="/facts/Isotopes_of_lithium/XC311sQu">lithium-6</a> enrichment in the <a href="/facts/Lithium_deuteride/uWCl2pST">lithium deuteride</a> fusion fuel. This results in the <a href="/facts/B41_nuclear_bomb/bNSostjy">B41</a> still retaining the record for the highest <a href="/facts/Power_density/aSQJNy5p">yield-to-mass</a> weapon ever designed.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a></li> <li>The <a href="/facts/W56/6c7ykP3e">W56</a> demonstrated a yield-to-mass ratio of 4.96 kt per kilogram of device mass, and very close to the predicted 5.1 kt/kg achievable in the highest yield-to-mass weapon ever built, the 25-megatonne B41. Unlike the B41, which was never proof-tested at full yield, the W56 demonstrated its efficiency in the XW-56X2 Bluestone shot of <a href="/facts/Operation_Dominic/RlBM2UIp">Operation Dominic</a> in 1962,<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> thus, from information available in the public domain, the W56 may hold the distinction of demonstrating the highest efficiency in a nuclear weapon to date.</li> <li>In 1963 DOE declassified statements that the U.S. had the technological capability of deploying a 35 Mt warhead on the Titan II, or a 50–60 Mt gravity bomb on B-52s. Neither weapon was pursued, but either would require yield-to-mass ratios superior to a 25 Mt Mk-41.</li> <li>For current smaller US weapons, yield is 600 to 2200 kilotonnes of TNT per tonne. By comparison, for the very small tactical devices such as the <a href="/facts/Davy_Crockett_(nuclear_device)/kDyeU6Hg">Davy Crockett</a> it was 0.4 to 40 kilotonnes of TNT per tonne. For historical comparison, for <a href="/facts/Little_Boy/4XAsA7xT">Little Boy</a> the yield was only 4 kilotonnes of TNT per tonne, and for the largest <a href="/facts/Tsar_Bomba/qbjpPwN2">Tsar Bomba</a>, the yield was 2 megatonnes of TNT per tonne (deliberately reduced from about twice as much yield for the same weapon, so there is little doubt that this bomb as designed was capable of 4 megatonnes per tonne yield).</li> <li>The largest <i>pure-fission</i> bomb ever constructed, <a href="/facts/Ivy_King/ljgMS1vL">Ivy King</a>, had a 500 kilotonne yield,<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> which is probably in the range of the upper limit on such designs. Fusion boosting could likely raise the efficiency of such a weapon significantly, but eventually all fission-based weapons have an upper yield limit due to the difficulties of dealing with large critical masses. (The UK's <a href="/facts/Orange_Herald/rzYHlzsQ">Orange Herald</a> was a very large boosted fission bomb, with a yield of 800 kilotonnes.) However, there is no known upper yield limit for a fusion bomb.</li></ul> <p>Large single warheads are seldom a part of today's arsenals, since smaller <a href="/facts/MIRV/cmzWwXxy">MIRV</a> warheads, spread out over a pancake-shaped destructive area, are far more destructive for a given total yield, or unit of payload mass. This effect results from the fact that destructive power of a single warhead on land scales approximately only as the cube root of its yield, due to blast "wasted" over a roughly hemispherical blast volume, while the strategic target is distributed over a circular land area with limited height and depth. This effect more than makes up for the lessened yield/mass efficiency encountered if ballistic missile warheads are individually scaled down from the maximal size that could be carried by a single-warhead missile. </p> <h3>Yield efficiency</h3> <p>The efficiency of an atomic bomb is the ratio of the actual yield to the theoretical maximum yield of the atomic bomb. Not all atomic bombs possess the same yield efficiency as each individual bombs design plays a large role in how efficient it can be. In order to maximize yield efficiency one must make sure to assemble the critical mass correctly, as well as implementing instruments such as tampers or initiators in the design. A tamper is typically made of uranium and it holds the core together using its inertia. It is used to prevent the core from separating too soon to generate maximum fission, so as not to cause a "fizzle". The initiator is a source of neutrons either inside of the core, or on the outside of the bomb, and in this case it shoots neutrons at the core at the moment of detonation. It is essentially kick starting the reaction so the maximum fission reactions can occur to maximize yield. <a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> <h2 id="milestone-nuclear-explosions">Milestone nuclear explosions</h2> <p>The following list is of milestone nuclear explosions. In addition to the <a href="/facts/Atomic_bombings_of_Hiroshima_and_Nagasaki/fRpj8aJA">atomic bombings of Hiroshima and Nagasaki</a>, the first nuclear test of a given weapon type for a country is included, as well as tests that were otherwise notable (such as the largest test ever). All yields (explosive power) are given in their estimated energy equivalents in kilotons of <a href="/facts/Trinitrotoluene/sADUt6nC">TNT</a> (see <a href="/facts/TNT_equivalent/nEQ5z8mp">TNT equivalent</a>). <a href="/facts/List_of_nuclear_tests/4jclhjH5">Putative tests</a> (like <a href="/facts/Vela_incident/4BL5WEHB">Vela incident</a>) have not been included. </p> <table><tbody><tr><th>Date</th><th>Name</th><th>Yield (kt)</th><th>Country</th><th>Significance</th></tr><tr><td>(1945-07-16)July 16, 1945</td><td><i><a href="/facts/Trinity_test/0aHtpyUN">Trinity</a></i></td><td>18–20</td><td><a href="/facts/Nuclear_weapons_and_the_United_States/sBxLkstG">United States</a></td><td>First fission-device test, first plutonium implosion detonation.</td></tr><tr><td>(1945-08-06)August 6, 1945</td><td><i><a href="/facts/Little_Boy/4XAsA7xT">Little Boy</a></i></td><td>12–18</td><td><a href="/facts/Nuclear_weapons_and_the_United_States/sBxLkstG">United States</a></td><td><a href="/facts/Atomic_bombings_of_Hiroshima_and_Nagasaki/fRpj8aJA">Bombing</a> of <a href="/facts/Hiroshima/WuFDhz14">Hiroshima</a>, <a href="/facts/Japan/U5mz0SRT">Japan</a>, first detonation of a uranium gun-type device, first use of a nuclear device in combat.</td></tr><tr><td>(1945-08-09)August 9, 1945</td><td><i><a href="/facts/Fat_Man/2vlxvS9a">Fat Man</a></i></td><td>18–23</td><td><a href="/facts/Nuclear_weapons_and_the_United_States/sBxLkstG">United States</a></td><td><a href="/facts/Atomic_bombings_of_Hiroshima_and_Nagasaki/fRpj8aJA">Bombing</a> of <a href="/facts/Nagasaki%2c_Nagasaki/5HMR4mnp">Nagasaki</a>, <a href="/facts/Japan/U5mz0SRT">Japan</a>, second detonation of a plutonium implosion device (the first being the Trinity Test), second and last use of a nuclear device in combat.</td></tr><tr><td>(1949-08-29)August 29, 1949</td><td><i><a href="/facts/RDS-1/mgXDp8fa">RDS-1</a></i></td><td>22</td><td><a href="/facts/Soviet_atomic_bomb_project/b5kFJIPY">Soviet Union</a></td><td>First fission-weapon test by the Soviet Union.</td></tr><tr><td>(1951-05-08)May 8, 1951</td><td><i><a href="/facts/Operation_Greenhouse/0hCFWth1">George</a></i></td><td>225</td><td><a href="/facts/Nuclear_weapons_and_the_United_States/sBxLkstG">United States</a></td><td>First boosted nuclear weapon test, first weapon test to employ fusion in any measure.</td></tr><tr><td>(1952-10-03)October 3, 1952</td><td><i><a href="/facts/Operation_Hurricane/HsNtjcmK">Hurricane</a></i></td><td>25</td><td><a href="/facts/Nuclear_weapons_and_the_United_Kingdom/lK8jPFP1">United Kingdom</a></td><td>First fission weapon test by the United Kingdom.</td></tr><tr><td>(1952-11-01)November 1, 1952</td><td><i><a href="/facts/Ivy_Mike/yFqF9H72">Ivy Mike</a></i></td><td>10,400</td><td><a href="/facts/Nuclear_weapons_and_the_United_States/sBxLkstG">United States</a></td><td>First "<a href="/facts/Nuclear_weapon_design/gw0LEc74">staged</a>" thermonuclear weapon, with cryogenic fusion fuel, primarily a test device and not weaponized.</td></tr><tr><td>(1952-11-16)November 16, 1952</td><td><i><a href="/facts/Ivy_King/ljgMS1vL">Ivy King</a></i></td><td>500</td><td><a href="/facts/Nuclear_weapons_and_the_United_States/sBxLkstG">United States</a></td><td>Largest pure-fission weapon ever tested.</td></tr><tr><td>(1953-08-12)August 12, 1953</td><td><i><a href="/facts/RDS-6s/HjACuGdr">RDS-6s</a></i></td><td>400</td><td><a href="/facts/Soviet_atomic_bomb_project/b5kFJIPY">Soviet Union</a></td><td>First fusion-weapon test by the Soviet Union (not "staged").</td></tr><tr><td>(1954-03-01)March 1, 1954</td><td><i><a href="/facts/Castle_Bravo/R2F4BRFf">Castle Bravo</a></i></td><td>15,000</td><td><a href="/facts/Nuclear_weapons_and_the_United_States/sBxLkstG">United States</a></td><td>First "staged" thermonuclear weapon using dry fusion fuel. A serious <a href="/facts/Nuclear_fallout/I1kJkLKt">nuclear fallout</a> accident occurred. Largest nuclear detonation conducted by United States.</td></tr><tr><td>(1955-11-22)November 22, 1955</td><td><i><a href="/facts/RDS-37/GFGsMb2W">RDS-37</a></i></td><td>1,600</td><td><a href="/facts/Soviet_atomic_bomb_project/b5kFJIPY">Soviet Union</a></td><td>First "staged" thermonuclear weapon test by the Soviet Union (deployable).</td></tr><tr><td>(1957-05-31)May 31, 1957</td><td><i><a href="/facts/Orange_Herald/rzYHlzsQ">Orange Herald</a></i></td><td>720</td><td><a href="/facts/Nuclear_weapons_and_the_United_Kingdom/lK8jPFP1">United Kingdom</a></td><td>Largest boosted fission weapon ever tested. Intended as a fallback "in megaton range" in case British thermonuclear development failed.</td></tr><tr><td>(1957-11-08)November 8, 1957</td><td><i><a href="/facts/Operation_Grapple/LoDVTsXp">Grapple X</a></i></td><td>1,800</td><td><a href="/facts/Nuclear_weapons_and_the_United_Kingdom/lK8jPFP1">United Kingdom</a></td><td>First (successful) "staged" thermonuclear weapon test by the United Kingdom</td></tr><tr><td>(1960-02-13)February 13, 1960</td><td><i><a href="/facts/Gerboise_Bleue/Y6SY7fNN">Gerboise Bleue</a></i></td><td>70</td><td><a href="/facts/France_and_weapons_of_mass_destruction/RGpsjtUa">France</a></td><td>First fission weapon test by France.</td></tr><tr><td>(1961-10-31)October 31, 1961</td><td><i><a href="/facts/Tsar_Bomba/qbjpPwN2">Tsar Bomba</a></i></td><td>50,000</td><td><a href="/facts/Soviet_atomic_bomb_project/b5kFJIPY">Soviet Union</a></td><td>Largest thermonuclear weapon ever tested—scaled down from its initial 100 Mt design by 50%.</td></tr><tr><td>(1964-10-16)October 16, 1964</td><td><i><a href="/facts/596_(nuclear_test)/QPUvKCmr">596</a></i></td><td>22</td><td><a href="/facts/People%2527s_Republic_of_China_and_weapons_of_mass_destruction/SeQ2B1CW">China</a></td><td>First fission-weapon test by the People's Republic of China.</td></tr><tr><td>(1967-06-17)June 17, 1967</td><td><i><a href="/facts/Chinese_nuclear_test_No._6/QXd6CGTL">Test No. 6</a></i></td><td>3,300</td><td><a href="/facts/People%2527s_Republic_of_China_and_weapons_of_mass_destruction/SeQ2B1CW">China</a></td><td>First "staged" thermonuclear weapon test by the People's Republic of China.</td></tr><tr><td>(1968-08-24)August 24, 1968</td><td><i><a href="/facts/Canopus_(nuclear_test)/CXMu79xC">Canopus</a></i></td><td>2,600</td><td><a href="/facts/France_and_weapons_of_mass_destruction/RGpsjtUa">France</a></td><td>First "staged" thermonuclear weapon test by France</td></tr><tr><td>(1974-05-18)May 18, 1974</td><td><i><a href="/facts/Smiling_Buddha/vhxqMQR1">Smiling Buddha</a></i></td><td>12</td><td><a href="/facts/India_and_weapons_of_mass_destruction/IcG8vgjd">India</a></td><td>First fission nuclear explosive test by India.</td></tr><tr><td>(1998-05-11)May 11, 1998</td><td><i><a href="/facts/Pokhran-II/xRhJSWkk">Pokhran-II</a></i></td><td>45–50</td><td><a href="/facts/India_and_weapons_of_mass_destruction/IcG8vgjd">India</a></td><td>First potential fusion-boosted weapon test by India; first deployable fission weapon test by India.</td></tr><tr><td>(1998-05-28)May 28, 1998</td><td><i><a href="/facts/Chagai-I/8LaQAvda">Chagai-I</a></i></td><td>40</td><td><a href="/facts/Pakistan_and_weapons_of_mass_destruction/sfNPnK3S">Pakistan</a></td><td>First fission weapon (boosted) test by Pakistan<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a></td></tr><tr><td>(2006-10-09)October 9, 2006</td><td><i><a href="/facts/2006_North_Korean_nuclear_test/eartLjgg">2006 nuclear test</a></i></td><td>under 1</td><td><a href="/facts/North_Korea_and_weapons_of_mass_destruction/1yT71YSy">North Korea</a></td><td>First fission-weapon test by North Korea (plutonium-based).</td></tr><tr><td>(2017-09-03)September 3, 2017</td><td><i><a href="/facts/2017_North_Korean_nuclear_test/QW2cun9Y">2017 nuclear test</a></i></td><td>200–300</td><td><a href="/facts/North_Korea_and_weapons_of_mass_destruction/1yT71YSy">North Korea</a></td><td>First "staged" thermonuclear weapon test claimed by North Korea.</td></tr></tbody></table> Note <ul><li>"Staged" refers to whether it was a "true" <a href="/facts/Thermonuclear_weapon/T9zFe3H0">thermonuclear weapon</a> of the so-called <a href="/facts/Teller%25E2%2580%2593Ulam/T9zFe3H0">Teller–Ulam</a> configuration or simply a form of a <a href="/facts/Boosted_fission_weapon/U11GQ2mf">boosted fission weapon</a>. For a more complete list of nuclear test series, see <a href="/facts/List_of_nuclear_tests/4jclhjH5">List of nuclear tests</a>. Some exact yield estimates, such as that of the <a href="/facts/Tsar_Bomba/qbjpPwN2">Tsar Bomba</a> and the tests by India and Pakistan in 1998, are somewhat contested among specialists.</li></ul> <h2 id="calculating-yields-and-controversy">Calculating yields and controversy</h2> <p class="note">See also: <a href="/facts/Fermi_problem/LueugRQk">Fermi problem</a></p> <p>Yields of <a href="/facts/Nuclear_explosion/BtpfgcUg">nuclear explosions</a> can be very hard to calculate, even using numbers as rough as in the kilotonne or megatonne range (much less down to the resolution of individual <a href="/facts/Terajoule/9ndq9jD2">terajoules</a>). Even under very controlled conditions, precise yields can be very hard to determine, and for less controlled conditions the margins of error can be quite large. For fission devices, the most precise yield value is found from "<a href="/facts/Radiochemistry/vdL6AaCH">radiochemical</a>/Fallout analysis"; that is, measuring the quantity of <a href="/facts/Fission_product/xJd9MXXH">fission products</a> generated, in much the same way as the <a href="/facts/Chemical_yield/fkBhd9dH">chemical yield</a> in chemical reaction products can be measured after a <a href="/facts/Chemical_reaction/GpqWlKrz">chemical reaction</a>. The radiochemical analysis method was pioneered by <a href="/facts/Herbert_L._Anderson/49KskgsX">Herbert L. Anderson</a>. </p><p>For nuclear explosive devices where the fallout is not attainable or would be <a href="/facts/Neutron_bomb/CDQspbMM">misleading</a>, <a href="/facts/Neutron_activation/FXwq3HUs">neutron activation</a> analysis is often employed as the second most accurate method, with it having been used to determine the yield of both <a href="/facts/Little_Boy/4XAsA7xT">Little Boy</a><a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> and <a href="/facts/Thermonuclear/fzQUW49h">thermonuclear</a> <a href="/facts/Ivy_Mike/yFqF9H72">Ivy Mike</a>'s<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> respective yields. </p><p>Yields can also be inferred in a number of other <a href="/facts/Remote_sensing/pj2crmGs">remote sensing</a> ways, including scaling law calculations based on blast size, <a href="/facts/Infrasound/yCUJSSe3">infrasound</a>, fireball brightness (<a href="/facts/Bhangmeter/FcnRouRT">Bhangmeter</a>), <a href="/facts/Seismograph/CCc9vwqf">seismographic</a> data (<a href="/facts/CTBTO/sFAGq1pT">CTBTO</a>),<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> and the strength of the shock wave. </p> Alongside contemporary fundamental physics, data from nuclear testing resulted in the following total blast and thermal energy fractionation being observed for fission detonations near <a href="/facts/Sea_level/mDhuI7Xe">sea level</a><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a><a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a><a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a><table><tbody><tr><td>Blast</td><td>50%</td></tr><tr><td>Thermal energy</td><td>35%</td></tr><tr><td>Initial <a href="/facts/Ionizing_radiation/vw0d9GaT">ionizing radiation</a></td><td>5%</td></tr><tr><td>Residual <a href="/facts/Fallout_radiation/I1kJkLKt">fallout radiation</a></td><td>10%</td></tr></tbody></table> <p><a href="/facts/Enrico_Fermi/cmYcY15H">Enrico Fermi</a> famously made a (very) rough calculation of the yield of the <a href="/facts/Trinity_test/0aHtpyUN">Trinity test</a> by dropping small pieces of paper in the air and measuring how far they were moved by the <a href="/facts/Blast_wave/aDgFJWLm">blast wave</a> of the explosion; that is, he found the <a href="/facts/Overpressure/aepmRBw0">blast pressure</a> at his distance from the detonation in <a href="/facts/Pounds_per_square_inch/RMdeTlB0">pounds per square inch</a>, using the deviation of the papers' fall away from the vertical as a crude <a href="/facts/Barograph/n7rkJsBq">blast gauge/barograph</a>, and then with pressure <i>X</i> in psi, at distance <i>Y</i>, in miles figures, he extrapolated backwards to estimate the yield of the Trinity device, which he found was about 10 <a href="/facts/Kilotonne/gMymLmWv">kilotonnes</a> of blast energy.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a><a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> </p><p>Fermi later recalled: </p> <blockquote><p> I was stationed at the Base Camp at Trinity in a position about ten miles [16 km] from the site of the explosion... About 40 seconds after the explosion the air blast reached me. I tried to estimate its strength by dropping from about six feet small pieces of paper before, during, and after the passage of the blast wave. Since, at the time, there was no wind[,] I could observe very distinctly and actually measure the displacement of the pieces of paper that were in the process of falling while the blast was passing. The shift was about 2 1/2 meters, which, at the time, I estimated to correspond to the blast that would be produced by ten thousand tonnes of TNT.<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a><a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a><a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a></p></blockquote> <p>The <a href="/facts/Surface_area/WNowzFCw">surface area</a> (A) and volume (V) of a sphere are A = 4 π r 2 {\displaystyle A=4\pi r^{2}} and V = 4 3 π r 3 {\displaystyle V={\frac {4}{3}}\pi r^{3}} respectively. </p><p>The blast wave, however, was likely assumed to grow out as the surface area of the approximately hemispheric near <a href="/facts/Surface_burst/RI4T0jIp">surface burst</a> blast wave of the Trinity gadget. The paper is moved 2.5 meters by the wave, so the effect of the Trinity device is to displace a hemispherical shell of air of volume 2.5 m × 2π(16 km)2. Multiply by 1 atm to get an energy of 4.1×1014 J ~ 100 kT TNT.[<i>quantify</i>] </p> <p>A good approximation of the yield of the Trinity test device was obtained in 1950 by the British physicist <a href="/facts/Geoffrey_Ingram_Taylor/akUuexNt">G. I. Taylor</a> from simple <a href="/facts/Dimensional_analysis/t6UskoCD">dimensional analysis</a> and an estimation of the heat capacity for very hot air. Taylor had initially done this highly classified work in mid-1941 and published an article with an analysis of the Trinity data fireball when the Trinity photograph data was declassified in 1950 (after the USSR had exploded its own version of this bomb). </p><p>Taylor noted that the <a href="/facts/Radius/9Gr9deYD">radius</a> <i>R</i> of the blast should initially depend only on the energy <i>E</i> of the explosion, the time <i>t</i> after the detonation, and the density ρ of the air. <a href="/facts/Buckingham_%25CF%2580_theorem/R3j8Dl2w">The only equation</a> having compatible dimensions that can be constructed from these quantities is </p> R = S ( E t 2 ρ ) 1 5 . {\displaystyle R=S\left({\frac {Et^{2}}{\rho }}\right)^{\frac {1}{5}}.} <p>Here <i>S</i> is a dimensionless constant having a value approximately equal to 1, since it is low-order function of the <a href="/facts/Heat_capacity_ratio/jFcMaukb">heat capacity ratio</a> or adiabatic index </p> γ = C P C V , {\displaystyle \gamma ={\frac {C_{P}}{C_{V}}},} <p>which is approximately 1 for all conditions. </p><p>Using the picture of the Trinity test shown here (which had been publicly released by the U.S. government and published in <i><a href="/facts/Life_(magazine)/t3r71BEK">Life</a></i> magazine), using successive frames of the explosion, Taylor found that <i>R</i>5/<i>t</i>2 is a constant in a given nuclear blast (especially between 0.38 ms, after the shock wave has formed, and 1.93 ms, before significant energy is lost by thermal radiation). Furthermore, he estimated a value for <i>S</i> numerically at 1. </p><p>Thus, with <i>t</i> = 0.025 s and the blast radius being 140 metres, and taking <i>ρ</i> to be 1 kg/m3 (the measured value at Trinity on the day of the test, as opposed to sea-level values of approximately 1.3 kg/m3) and solving for <i>E</i>, Taylor obtained that the yield was about 22 kilotonnes of TNT (90 TJ). This does not take into account the fact that the energy should only be about half this value for a hemispherical blast, but this very simple argument did agree to within 10% with the official value of the bomb's yield in 1950, which was 20 kilotons of TNT (84 TJ) (see G. I. Taylor, <i>Proc. Roy. Soc. London A</i> 200, pp. 235–247 (1950)). </p><p>A good approximation to Taylor's constant <i>S</i> for γ {\displaystyle \gamma } below about 2 is<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a> </p> S = ( 75 ( γ − 1 ) 8 π ) 1 5 . {\displaystyle S=\left({\frac {75(\gamma -1)}{8\pi }}\right)^{\frac {1}{5}}.} <p>The value of the <a href="/facts/Heat_capacity_ratio/jFcMaukb">heat capacity ratio</a> here is between the 1.67 of fully dissociated air molecules and the lower value for very hot diatomic air (1.2), and under conditions of an atomic fireball is (coincidentally) close to the <a href="/facts/Standard_temperature_and_pressure/JhJv9KFJ">STP</a> (standard) gamma for room-temperature air, which is 1.4. This gives the value of Taylor's S constant to be 1.036 for the adiabatic hypershock region where the constant <i>R</i>5/<i>t</i>2 condition holds. </p><p>As it relates to fundamental dimensional analysis, if one expresses all the variables in terms of mass <i>M</i>, length <i>L</i>, and time <i>T</i>:<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a> </p> E = [ M ⋅ L 2 ⋅ T − 2 ] {\displaystyle E=[M\cdot L^{2}\cdot T^{-2}]} <p>(think of the expression for kinetic energy, E = m v 2 / 2 {\displaystyle E=mv^{2}/2} ), </p> ρ = [ M ⋅ L − 3 ] , {\displaystyle \rho =[M\cdot L^{-3}],} t = [ T ] , {\displaystyle t=[T],} r = [ L ] , {\displaystyle r=[L],} <p>and then derive an expression for, say, <i>E</i>, in terms of the other variables, by finding values of α {\displaystyle \alpha } , β {\displaystyle \beta } , and γ {\displaystyle \gamma } in the general relation </p> E = ρ α ⋅ t β ⋅ r γ {\displaystyle E=\rho ^{\alpha }\cdot t^{\beta }\cdot r^{\gamma }} <p>such that the left and right sides are dimensionally balanced in terms of <i>M</i>, <i>L</i>, and <i>T</i> (i.e., each dimension has the same exponent on both sides). </p> <h3>Other methods and controversy</h3> <p>Where these data are not available, as in a number of cases, precise yields have been in dispute, especially when they are tied to questions of politics. The weapons used in the <a href="/facts/Atomic_bombings_of_Hiroshima_and_Nagasaki/fRpj8aJA">atomic bombings of Hiroshima and Nagasaki</a>, for example, were highly individual and very idiosyncratic designs, and gauging their yield retrospectively has been quite difficult. The Hiroshima bomb, "<a href="/facts/Little_Boy/4XAsA7xT">Little Boy</a>", is estimated to have been between 12 and 18 kilotonnes of TNT (50 and 75 TJ) (a 20% margin of error), while the Nagasaki bomb, "<a href="/facts/Fat_Man/2vlxvS9a">Fat Man</a>", is estimated to be between 18 and 23 kilotonnes of TNT (75 and 96 TJ) (a 10% margin of error). </p><p>Such apparently small changes in values can be important when trying to use the data from these bombings as reflective of how other bombs would behave in combat, and also result in differing assessments of how many "Hiroshima bombs" other weapons are equivalent to (for example, the <a href="/facts/Ivy_Mike/yFqF9H72">Ivy Mike</a> hydrogen bomb was equivalent to either 867 or 578 Hiroshima weapons — a rhetorically quite substantial difference — depending on whether one uses the high or low figure for the calculation). </p><p>Other disputed yields have included the massive <a href="/facts/Tsar_Bomba/qbjpPwN2">Tsar Bomba</a>, whose yield was claimed between being "only" 50 megatonnes of TNT (210 PJ) or at a maximum of 57 megatonnes of TNT (240 PJ) by differing political figures, either as a way for hyping the power of the bomb or as an attempt to undercut it. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Effects_of_nuclear_explosions/cReYEzPg">Effects of nuclear explosions</a> — goes into detail about different effects at different yields</li> <li><a href="/facts/List_of_nuclear_weapons/MwGSWHLV">List of nuclear weapons</a></li></ul> <h2 id="external-links">External links</h2> Wikimedia Commons has media related to Nuclear weapon yield. <ul><li><a href="http://www.warbirdforum.com/hiroshim.htm">"What was the yield of the Hiroshima bomb?"</a> <a href="https://web.archive.org/web/20170913004426/https://www.warbirdforum.com/hiroshim.htm">Archived</a> 2017-09-13 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a> (excerpt from official report)</li> <li><a href="https://web.archive.org/web/20051201184506/http://www.cddc.vt.edu/host/atomic/nukeffct/enw77a.html">"General Principles of Nuclear Explosions"</a>, Chapter 1 in Samuel Glasstone and Phillip Dolan, eds., <i>The Effects of Nuclear Weapons</i>, 3rd edn. (Washington D.C.: U.S. Department of Defense/U.S. Energy Research and Development Administration, 1977); provides information about the relationship of nuclear yields to other effects (radiation, damage, etc.).</li> <li><a href="https://web.archive.org/web/20060405211214/http://www.saag.org/papers5/paper451.html">"THE MAY 1998 POKHRAN TESTS: Scientific Aspects"</a>, discusses different methods used to determine the yields of the Indian 1998 tests.</li> <li><a href="https://fas.org/nuke/guide/india/nuke/">Discusses some of the controversy over the Indian test yields</a></li> <li><a href="http://nuclearweaponarchive.org/India/IndiaRealYields.html">"What are the real yields of India's nuclear tests?"</a> from Carey Sublette's NuclearWeaponArchive.org</li> <li><a href="http://meyerweb.com/eric/tools/gmap/hydesim.html">High-Yield Nuclear Detonation Effects Simulator</a> <a href="https://web.archive.org/web/20090216184207/http://meyerweb.com/eric/tools/gmap/hydesim.html">Archived</a> 2009-02-16 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>The B-41 Bomb <a href="http://nuclearweaponarchive.org/Usa/Weapons/B41.html" target="_blank">http://nuclearweaponarchive.org/Usa/Weapons/B41.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"Complete List of All U.S. Nuclear Weapons". The Nuclear Weapon Archive. October 14, 2006. Retrieved August 29, 2014. <a href="http://nuclearweaponarchive.org/Usa/Weapons/Allbombs.html#MK-18" target="_blank">http://nuclearweaponarchive.org/Usa/Weapons/Allbombs.html#MK-18</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Ackerman, Spencer (October 23, 2011). "Last Nuclear 'Monster Weapon' Gets Dismantled". Wired. Retrieved 23 October 2011. <a href="https://www.wired.com/dangerroom/2011/10/b53-dismantled/" target="_blank">https://www.wired.com/dangerroom/2011/10/b53-dismantled/</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Rowberry, Ariana. "Castle Bravo: The Largest U.S. Nuclear Explosion". Brookings Institution. Retrieved 23 September 2017. <a href="https://www.brookings.edu/blog/up-front/2014/02/27/castle-bravo-the-largest-u-s-nuclear-explosion/" target="_blank">https://www.brookings.edu/blog/up-front/2014/02/27/castle-bravo-the-largest-u-s-nuclear-explosion/</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Norris, Robert S.; Arkin, William M. (May 1996). "Known Nuclear Tests Worldwide, 1945-1995". Bulletin of the Atomic Scientists. 52 (3): 63. Bibcode:1996BuAtS..52c..61.. doi:10.1080/00963402.1996.11456628. <a href="https://books.google.com/books?id=xAwAAAAAMBAJ&pg=PA63" target="_blank">https://books.google.com/books?id=xAwAAAAAMBAJ&pg=PA63</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Pickrell, Ryan (6 August 2020). "Beirut's Devastating Explosion Equivalent to Several Hundred Tons of TNT, Experts Say". ScienceAlert. Retrieved 2020-08-06. <a href="https://www.sciencealert.com/beirut-s-devastating-port-explosion-100-times-bigger-than-the-mother-of-all-bombs" target="_blank">https://www.sciencealert.com/beirut-s-devastating-port-explosion-100-times-bigger-than-the-mother-of-all-bombs</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Cozzani, Franco (July 26, 2011). Fission, Fusion and Staging: A bird's view at the core concepts of nuclear weapon design and the curious ideas about it. IERI. Retrieved February 3, 2017.. <a href="http://www.ieri.be/fr/publications/ierinews/2011/juillet/fission-fusion-and-staging" target="_blank">http://www.ieri.be/fr/publications/ierinews/2011/juillet/fission-fusion-and-staging</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>"Operation Dominic". The Nuclear Weapon Archive. <a href="http://nuclearweaponarchive.org/Usa/Tests/Dominic.html" target="_blank">http://nuclearweaponarchive.org/Usa/Tests/Dominic.html</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>"Complete List of All U.S. Nuclear Weapons". The Nuclear Weapon Archive. October 14, 2006. Retrieved August 29, 2014. <a href="http://nuclearweaponarchive.org/Usa/Weapons/Allbombs.html#MK-18" target="_blank">http://nuclearweaponarchive.org/Usa/Weapons/Allbombs.html#MK-18</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>"Nuclear Weapons Primer". Wisconsin Project on Nuclear Arms Control. Retrieved 2023-04-28. <a href="https://www.wisconsinproject.org/nuclear-weapons/" target="_blank">https://www.wisconsinproject.org/nuclear-weapons/</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>"Pakistan Nuclear Weapons: A Brief History of Pakistan's Nuclear Program". Federation of American Scientists. 11 December 2002. Retrieved 30 October 2019. <a href="http://www.fas.org/nuke/guide/pakistan/nuke/" target="_blank">http://www.fas.org/nuke/guide/pakistan/nuke/</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Kerr, George D.; Young, Robert W.; Cullings, Harry M.; Christy, Robert F. (2005). "Bomb Parameters" (PDF). In Young, Robert W.; Kerr, George D. (eds.). Reassessment of the Atomic Bomb Radiation Dosimetry for Hiroshima and Nagasaki – Dosimetry System 2002. The Radiation Effects Research Foundation. pp. 42–43. Archived from the original (PDF) on 2015-08-10. Retrieved 2014-11-08. <a href="https://web.archive.org/web/20150810210007/http://www.rerf.or.jp/shared/ds02/pdf/chapter01/cha01-p42-61.pdf" target="_blank">https://web.archive.org/web/20150810210007/http://www.rerf.or.jp/shared/ds02/pdf/chapter01/cha01-p42-61.pdf</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Malik, John (September 1985). "The Yields of the Hiroshima and Nagasaki Explosions" (PDF). Los Alamos National Laboratory. Retrieved March 9, 2014. <a href="https://www.osti.gov/manhattan-project-history/publications/LANLHiroshimaNagasakiYields.pdf" target="_blank">https://www.osti.gov/manhattan-project-history/publications/LANLHiroshimaNagasakiYields.pdf</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>US Army (1952). Operation Ivy Final Report Joint Task Force 132 (PDF). Archived (PDF) from the original on March 11, 2014. <a href="http://apps.dtic.mil/dtic/tr/fulltext/u2/a995443.pdf" target="_blank">http://apps.dtic.mil/dtic/tr/fulltext/u2/a995443.pdf</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Estimating the yields of nuclear explosions. chapter 7. Seismic verification of nuclear testing treaties. <a href="https://www.princeton.edu/~ota/disk2/1988/8838/883809.PDF" target="_blank">https://www.princeton.edu/~ota/disk2/1988/8838/883809.PDF</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>"Chapter 3 Effects of Nuclear Explosions, Section I – General". <a href="https://fas.org/nuke/guide/usa/doctrine/dod/fm8-9/1ch3.htm" target="_blank">https://fas.org/nuke/guide/usa/doctrine/dod/fm8-9/1ch3.htm</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>"Nuclear Events and their Consequences" (PDF). The Borden Institute. Archived from the original (PDF) on 2017-01-25. approximately 82% of the fission energy is released as kinetic energy of the two large fission fragments. These fragments, being massive and highly charged particles, interact readily with matter. They transfer their energy quickly to the surrounding weapon materials, which rapidly become heated. <a href="https://web.archive.org/web/20170125171152/https://ke.army.mil/bordeninstitute/published_volumes/nuclearwarfare/chapter1/chapter1.pdf" target="_blank">https://web.archive.org/web/20170125171152/https://ke.army.mil/bordeninstitute/published_volumes/nuclearwarfare/chapter1/chapter1.pdf</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>"Nuclear Engineering Overview" (PDF). Technical University Vienna. Archived from the original (PDF) on May 15, 2018.. The various energies emitted per fission event are listed on p. 4: "167 MeV" is emitted by means of the repulsive electrostatic energy between the 2 daughter nuclei, which takes the form of the "kinetic energy" of the fission fragments, this kinetic energy results in both later blast and thermal effects. "5 MeV" is released in prompt or initial gamma radiation, "5 MeV" in prompt neutron radiation (99.36% of total), "7 MeV" in delayed neutron energy (0.64%), and "13 MeV" in beta decay and gamma decay(residual radiation). <a href="https://web.archive.org/web/20180515201022/http://www.oektg.at/wp-content/uploads/02-Nuclear-Engineering-Overview1.pdf" target="_blank">https://web.archive.org/web/20180515201022/http://www.oektg.at/wp-content/uploads/02-Nuclear-Engineering-Overview1.pdf</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Article featuring Jack Aeby talking about his photograph. <a href="http://www.abqjournal.com/trinity/trinity1.htm" target="_blank">http://www.abqjournal.com/trinity/trinity1.htm</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Rhodes, Richard (1986). The Making of the Atomic Bomb. New York: Simon & Schuster. pp. 674–677. ISBN 0-671-44133-7. OCLC 13793436. <a href="0-671-44133-7" target="_blank">0-671-44133-7</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>E. Fermi. My Observations During the Explosion at Trinity on July 16, 1945. <a href="https://web.archive.org/web/20130302233056/http://www2.vo.lu/homepages/geko/atom/report.htm" target="_blank">https://web.archive.org/web/20130302233056/http://www2.vo.lu/homepages/geko/atom/report.htm</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>"Trinity Test, July 16, 1945, Eyewitness Accounts – Enrico Fermi". Retrieved November 4, 2014. <a href="http://www.dannen.com/decision/fermi.html" target="_blank">http://www.dannen.com/decision/fermi.html</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>"Eyewitnesses to Trinity" (PDF). Nuclear Weapons Journal, Issue 2, 2005. Los Alamos National Laboratory. 2005. p. 45. Archived from the original (PDF) on 29 December 2018. Retrieved 18 February 2014. <a href="https://web.archive.org/web/20181229223636/https://www.lanl.gov/science/weapons_journal/wj_pubs/11nwj2-05.pdf" target="_blank">https://web.archive.org/web/20181229223636/https://www.lanl.gov/science/weapons_journal/wj_pubs/11nwj2-05.pdf</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>"Analytical mathematics for physical understanding, versus abstract numerical computation". The effects of nuclear weapons. Credible nuclear deterrence, debunking "disarm or be annihilated". Realistic effects and credible nuclear weapon capabilities for deterring or stopping aggressive invasions and attacks which could escalate into major conventional or nuclear wars. 2006-03-29. <a href="http://glasstone.blogspot.com/2006/03/analytical-mathematics-for-physical.html" target="_blank">http://glasstone.blogspot.com/2006/03/analytical-mathematics-for-physical.html</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>Thayer Watkins. The Expansion of the Fireball of an Explosion. San José State University. <a href="https://web.archive.org/web/20140701221514/http://applet-magic.com/fireball.htm" target="_blank">https://web.archive.org/web/20140701221514/http://applet-magic.com/fireball.htm</a> <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> </ol>