Editing Little Boy (section)

===Conventional weapon equivalent===

After hostilities ended, a survey team from the Manhattan Project that included [[William Penney]], Robert Serber, and [[George T. Reynolds]] was sent to Hiroshima to evaluate the effects of the blast. From evaluating the effects on objects and structures, Penney concluded that the yield was 12 ± 1 kilotons.{{sfn|Malik|1985|pp=18–20}} Later calculations based on charring pointed to a yield of 13 to 14 kilotons.{{sfn|Malik|1985|p=21}} In 1953, [[Frederick Reines]] calculated the yield as {{convert|15|ktonTNT}}.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=393}} Based on the Project Ichiban data, and the pressure-wave data from ''The Great Artiste'', the yield was estimated in the 1960s at 16.6 ± 0.3 kilotons.{{sfn|Malik|1985|p=16}} A review conducted by a scientist at Los Alamos in 1985 concluded, on the basis of existing blast, thermal, and radiological data, and then-current models of weapons effects, that the best estimate of the yield was {{convert|15|ktonTNT}} with an uncertainty of 20% (±3 kt). By comparison, the best value for the Nagasaki bomb was evaluated as {{convert|21|ktonTNT}} with an uncertainty of 10% (±2 kt), the difference in uncertainty owing to having better data on the latter.{{sfn|Malik|1985|p=1}}

To put these numerical differences into context, it is necessary to know that the acute effects of nuclear detonations, especially the blast and thermal effects, do not scale linearly, but generally as a [[cubic root]]. Specifically, the distance of these effects scale as a function of the yield raised to an exponential power of {{frac|1|3}}.{{sfn|Glasstone|Dolan|1977|page=101}} So the range of the {{convert|5|psi}} overpressure damage expected from a detonated 12 kiloton weapon with a height of burst at {{convert|1968|ft}} would be expected to be {{convert|0.98|mi}}, whereas a 20 kiloton weapon would have the same range extend to {{convert|1.12|mi}}, a difference of only {{convert|0.14|mi}}. The areas affected for each would be {{convert|3.02|sqmi}} and {{convert|3.91|sqmi}}, respectively. As such, the practical differences in effects at these yield ranges are smaller than may at first appear, if one assumes that there is a linear relationship between yield and damage.<ref>These calculated numbers come from the [[NUKEMAP]] website, which uses the data and calculations from {{harvnb|Glasstone|Dolan|1977|pages=80-122}}.</ref>

Although Little Boy exploded with the energy equivalent of around 15 kilotons of TNT, in 1946 the [[Strategic Bombing Survey]] estimated that the same blast and fire effect could have been caused by 2.1 kilotons of [[conventional bomb]]s distributed evenly over the same target area: "220 B-29s carrying 1.2 kilotons of [[incendiary bombs]], 400 tons of [[high-explosive]] bombs, and 500 tons of [[anti-personnel weapon|anti-personnel]] [[fragmentation bombs]]."{{sfn|D'Olier|1946|p=24}} Since the target was spread across a two-dimensional plane, the vertical component of a single spherical nuclear explosion was largely wasted. A [[cluster bomb]] pattern of smaller explosions would have been a more energy-efficient match to the target.{{sfn|D'Olier|1946|p=24}}