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Author Topic: Did Apollo controllers compensate for time delay?  (Read 2207 times)

Offline Eric A. Taylor

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As the Eagle descended to the moon Neil Armstrong was forced to take over control when he realized they were going to land in a bolder field. As he is looking for a new landing spot you can hear controllers calling out his fuel state. First rather calmly "60 seconds" then with a little more stress "30 seconds" then just before touchdown a very stressed "15 seconds". Armstrong has stated he knew he had "plenty" of fuel to make a safe landing as soon as he picked his new landing site, long before he heard "60 seconds". The moon is 1.5 light seconds from the earth so when Neil heard "30 seconds" in his head set did he in fact have just 27 seconds of fuel left, or did the controller call out "30 seconds" when he READ 33 seconds fuel remaining? Being somewhat smart the controller would know that his data was already 1.5 seconds old and it would take another 1.5 seconds for his words to reach Eagle so by the time Neil heard the controller's words the data would be 3 seconds old.


 

Offline LeeE

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Did Apollo controllers compensate for time delay?
« Reply #1 on: 07/12/2009 17:31:19 »
Hmm...  I don't know the answer to this question but I strongly suspect that the controller on Earth would just read out the data as he saw it, for guidance only, and that any correction/allowance for time delay would be made by Armstrong up on the Moon.  I'm not even sure if the fuel usage figures that the Earth-side controller was giving were based upon actual fuel readings sent from the LEM or whether they were just projections based upon the duration of the burn.

In the end, it would all come down to Armstrong as he was actually there and knew how much fuel he had burnt.  Don't forget too, that 'Buzz' Aldrin, who had an engineering background, was also on board the LEM and would have been monitoring fuel levels alongside Armstrong.
 

Offline Geezer

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Did Apollo controllers compensate for time delay?
« Reply #2 on: 07/12/2009 23:55:37 »
I suppose, if it was based on telemetry from the LEM, it would be a three second delay.
 

Offline Eric A. Taylor

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Did Apollo controllers compensate for time delay?
« Reply #3 on: 08/12/2009 06:28:08 »
Aldrin's "background" in engineering happened to be a PhD! Aldrin might have been an asshole, I don't know for sure, having only talked to him once, but he was not stupid. None of them were. NASA engineers were having a hell of a time figuring out how to work in space. Ed White's space walk was a huge success but he didn't DO anything. Several Gemini flights wore astronauts out trying to do useful work during a space walk. It was absolutely critical that they find a solution to this problem. Without a solution there would be no Apollo flight. It was Aldrin who figured it out.

The job of the LMP was to read information to his commander, as the commander was far to busy flying the ship. He was "pilot" in name only, simply because these guys were mostly fighter pilots and test pilots and would not stand being called "co-pilot". Though all LMPs were trained to fly the lunar lander none officially did it. Most did fly it on the back side of the moon though.
 

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Did Apollo controllers compensate for time delay?
« Reply #3 on: 08/12/2009 06:28:08 »

 

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