Sorry to diverge from the thread topic and follow this zepher but I heard the landing recounted first hand at dinner one night with one of the crew. He said they were steady at 50 feet altitude tracking down range trying to find a suitable landing site , as the original one was strewn with large boulders. I was told there were two seconds of fuel remaining but did not think to qualify if that was absolute or the time ( in fuel cap) before go - no go for landing. I was left with the impression that it was 2 seconds left until abort. However your 17 seconds minus 2 sounds about right. 15 seconds with 50 feet of altitude was probably the cut off point.Chryseplanatia":24ic56fl said:Yeah, "Dead Man" area (a term I am told is not preferred by the "professionals"' so, sorry about that!) was the altitude where it was too late for a stage separation. Idea then would be to loose any forward (or lateral) movement ad drop as quickly as possible for a soft(ish) landing. Then a stage sep could occur safely and they could ascend if necessary.
Now we know why Charlie Duke, Apollo 11 landing CapCom, sounded like his pants were a bit too tight when he said "30 seconds!" into the mike.
As I recall, the popular version was that the descent stage was down to about 17 seconds of hover/landing time, but later the estimate was rounded up to more like 30-40 secs, as the anti-slosh baffles had compromised the low-fuel reading. Heck, my Chevy does the same thing, tho the results of power loss are bit less dramatic.
As dramatic was the ice fuel plug in a descent stage fuel line that started building up pressure in the fuel system after touchdown. I don't think they were clear on whether or not it would result in a burst helium disk or a real explosion, but the latent heat in the descent engine melted it out and all was well. But there were some heart-stopping seconds on a couple of mission control consoles.
Re the original poster, I too welcome newbie questions, but a bit of research beforehand never hurts. I suspect that LM graphic was off of Wikipedia. and much of what is clarified here would be clearly seen there after a careful reading.
Nice add about the iced fuel line!