I have not seen a discussion on this Manhattan Project point of divergence, but it is an interesting one. What if Little Boy were to explode during a handling accident or during a failed takeoff or emergency landing of the Enola Gay, destroying half of Tinian Island and the 509th Composite Air Group? Does the invasion of Japan go ahead as planned, and how long does it take for the USAAF to regain the ability to carry out nuclear strikes (seeing as many of the special aircraft and key personnel are vaporized)?