60 Seconds, the last few moments before Apollo 11 touched down

[wiggy]

No it wouldn’t have been an automated abort.

As for the fuel calls… they weren’t a direct count of seconds to tanks dry.

The rationale behind the timing calls was that NASA and the astronauts wanted to avoid if at all possible going through a process known as “abort stage” at low altitude.

That was a series of steps involving the descent stage being jettisoned from the ascent stage, various systems in the ascent stage being quickly powered up and pressurized and then the ascent engine firing to return the vehicle to orbit.. That sequence could take anything up to four seconds and if the LM was near the surface the crew might run out of altitude before the the ascent engine generated a rate of climb.

The other big danger issue with a low level abort stage was that it risked “frag” damage to the ascent stage if the descent stage hit the surface and components within it exploded..

So….the fuel timing was run such that when the timing got to zero on the stopwatch (managed by a gentleman called Bob Carlton) there were still approximately 20 seconds of fuel left in the descent stage. At zero on the watch the capcom in Houston (Charlie Duke on 11) would call “ fuel depletion”, which was a signal to the crew that they had to either:

1. Commit to continue to land in the next 20 seconds…

or

2. Abort by applying full power on the descent engine to immediately start climbing away, gaining altitude and building up a rate of climb. Once the descent engine ran out of fuel after a few seconds the abort staging could be done with the vehicle well clear of the surface and with a positive rate of climb.

HTH