The critical mass of any given nuclear system is not simply a matter of mass — it is a more complex function of the mass, its geometry, and properties like neutron reflection, among other things. As an illustrative example, the "bare sphere" critical mass of 70%-enriched uranium is 87.2 kilograms (192 lb), but with a 5 centimetres (2.0 in) beryllium neutron reflector, it drops to 36.5 kilograms (80 lb), and with a 10 centimetres (3.9 in) beryllium reflector, it drops to 23.7 kilograms (52 lb). Glaser, Alexander (2006). "On the Proliferation Potential of Uranium Fuel for Research Reactors at Various Enrichment Levels". Science and Global Security. 14: 1–24. doi:10.1080/08929880600620542. So while the 38.53 kilograms (84.9 lb), 80%-enriched, cylindrical "projectile" was an insufficient amount of enriched uranium to be a "bare sphere" critical mass, inside of a neutron-reflecting system it could potentially be dangerously close to criticality even prior to weapon assembly, or just prior to full assembly. After weapon assembly, the 64.2 kilograms (142 lb) 80%-enriched material, in a solid cylinder and encased in a neutron-reflecting tungsten tamper, would have composed more than one critical mass.
Glasstone & Dolan 1977, p. 409 "An air burst, by definition, is one taking place at such a height above the earth that no appreciable quantities of surface material are taken up into the fireball. ... the deposition of early fallout from an air burst will generally not be significant. An air burst, however, may produce some induced radioactive contamination in the general vicinity of ground zero as a result of neutron capture by elements in the soil." p. 36, "at Hiroshima ... injuries due to fallout were completely absent.". Glasstone, Samuel; Dolan, Philip J. (1977). The Effects of Nuclear Weapons, Third Edition. United States: United States Department of Defense and United States Department of Energy. ISBN978-1603220163.
Ramsey, N. F. (2012). "History of Project A". In Coster-Mullen, John (ed.). Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. United States: J. Coster-Mullen. OCLC298514167.
Coster-Mullen 2012, p. 30. Coster-Mullen, John (2012). Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. Waukesha, Wisconsin: J. Coster-Mullen. OCLC298514167.
Hansen 1995, pp. 111–112. Hansen, Chuck (1995). Volume V: US Nuclear Weapons Histories. Swords of Armageddon: US Nuclear Weapons Development since 1945. Sunnyvale, California: Chuckelea Publications. ISBN978-0-9791915-0-3. OCLC231585284.
Hansen 1995, p. 113. Hansen, Chuck (1995). Volume V: US Nuclear Weapons Histories. Swords of Armageddon: US Nuclear Weapons Development since 1945. Sunnyvale, California: Chuckelea Publications. ISBN978-0-9791915-0-3. OCLC231585284.
Coster-Mullen 2012, p. 18. Coster-Mullen, John (2012). Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. Waukesha, Wisconsin: J. Coster-Mullen. OCLC298514167.
Coster-Mullen 2012, p. 27. Coster-Mullen, John (2012). Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. Waukesha, Wisconsin: J. Coster-Mullen. OCLC298514167.
Coster-Mullen 2012, pp. 18–19, 27. Coster-Mullen, John (2012). Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. Waukesha, Wisconsin: J. Coster-Mullen. OCLC298514167.
Coster-Mullen 2012, p. 28. Coster-Mullen, John (2012). Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. Waukesha, Wisconsin: J. Coster-Mullen. OCLC298514167.
Coster-Mullen 2012, pp. 23–24. Coster-Mullen, John (2012). Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. Waukesha, Wisconsin: J. Coster-Mullen. OCLC298514167.
Hansen 1995a, pp. 2–5. Hansen, Chuck (1995a). Volume VII: The Development of US Nuclear Weapons. Swords of Armageddon: US Nuclear Weapons Development since 1945. Sunnyvale, California: Chuckelea Publications. ISBN978-0-9791915-7-2. OCLC231585284.
Campbell 2005, pp. 46, 80. Campbell, Richard H. (2005). The Silverplate Bombers: A History and Registry of the Enola Gay and Other B-29s Configured to Carry Atomic Bombs. Jefferson, North Carolina: McFarland & Company. ISBN0-7864-2139-8. OCLC58554961.
Coster-Mullen 2012, pp. 100–101. Coster-Mullen, John (2012). Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. Waukesha, Wisconsin: J. Coster-Mullen. OCLC298514167.
Coster-Mullen 2012, pp. 34–35. Coster-Mullen, John (2012). Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. Waukesha, Wisconsin: J. Coster-Mullen. OCLC298514167.
Coster-Mullen 2012, pp. 86–87. Coster-Mullen, John (2012). Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. Waukesha, Wisconsin: J. Coster-Mullen. OCLC298514167.
Coster-Mullen 2012, p. 85. Coster-Mullen, John (2012). Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. Waukesha, Wisconsin: J. Coster-Mullen. OCLC298514167.
Hansen 1995, pp. 116–118. Hansen, Chuck (1995). Volume V: US Nuclear Weapons Histories. Swords of Armageddon: US Nuclear Weapons Development since 1945. Sunnyvale, California: Chuckelea Publications. ISBN978-0-9791915-0-3. OCLC231585284.
Hansen 1995, p. 115. Hansen, Chuck (1995). Volume V: US Nuclear Weapons Histories. Swords of Armageddon: US Nuclear Weapons Development since 1945. Sunnyvale, California: Chuckelea Publications. ISBN978-0-9791915-0-3. OCLC231585284.