Aerophotos writes:

The spare B-29 "Top Secret" was meant to be the replacement for Enola
Gay for the 6th August... if she had broken down in flight.. and RTB...

Does anyone know what happened to Top Secret's bombload? on the Aug 6th
mission???

so that makes 3 atomic weapons on Tinain... so the USAAF could of
effectively bombed another target.. but chose not to..

Well no, as pointed out by other posters. But my question is, was
Kyoto the primary target for the 2nd bombing mission that eventually
devastated Nagasaki, as I have read in one report on the internet. I
always thought Kyoto was not bombed due to the efforts of a certain US
diplomat (?) who IIRC is actually buried in Kyoto.... maybe a myth.

From my reading, I thought that Hiroshima was the primary target due
to the concentration of military installations and command
centers. Nagasaki was chosen because of the naval base
installations. I don't know how true the allegations are that a city
with modern concrete structures (Hiroshima) vs one with mostly
traditional housing (Nagasaki) were chosen. Please correct my mistaken
impressions!

As far as a further mission is concerned, I thought that in the event
of a third mission, not Tokyo but Sapporo was to be targetted. How far
did plans for a third mission go, I did not find out even if there was
enough fissionable material on hand to make another bomb immediately,
or whether that would have taken further weeks or perhaps months.

Any useful references would be appreciated, Google was not exactly
conclusive and this is not my subject, hence I am not able to judge
the quality of the references easily.

Many thanks,
Gernot
--
G Hassenpflug * IJN & JMSDF equipment/history fan