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  Mercury - Gemini - Apollo
  Timing of the Apollo lunar landings

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Author Topic:   Timing of the Apollo lunar landings
Peter downunder
Member

Posts: 37
From: Lancefield, Victoria, Australia
Registered: Apr 2012

posted 07-12-2014 06:29 PM     Click Here to See the Profile for Peter downunder   Click Here to Email Peter downunder     Edit/Delete Message   Reply w/Quote
I find myself involved in a discussion about the timing of the lunar landings.

I have always thought the main issue was lighting conditions for the landing.

The person I'm talking to feels that the major issue was the timing of the EVAs. It would seem the pressure suits were not up to coping with the conditions of the late lunar morning, or worse, the conditions of midday on the lunar surface.

Can anyone point me to a previous discussion on this subject, or perhaps some other documents? Our 'discussion' has now descended into the 'no it isn't!' "yes, it is!!" level. Any help would be appreciated.

Headshot
Member

Posts: 334
From: Streamwood, IL USA
Registered: Feb 2012

posted 07-12-2014 08:24 PM     Click Here to See the Profile for Headshot   Click Here to Email Headshot     Edit/Delete Message   Reply w/Quote
According to a passage in Where No Man Has Gone Before, launch was scheduled so that the sun's altitude during landing would be between 7-1/2 to 15 degrees. I have never heard that the time of the EVAs entered into consideration except for astronaut fatigue.

I am curious as to what others have read or discovered.

Peter downunder
Member

Posts: 37
From: Lancefield, Victoria, Australia
Registered: Apr 2012

posted 07-12-2014 10:17 PM     Click Here to See the Profile for Peter downunder   Click Here to Email Peter downunder     Edit/Delete Message   Reply w/Quote
Thanks for your interest. From my reading, it has always about the pilot having a good view of the surface. Michael Collins' autobiography covered the subject as well.

The other argument is that it was paramount to have the EVA early as the direct sunlight would be too much for the suits. I have seen simplified websites that say (of course) the early morning environment was more benign, but I was skeptical that a midday EVA would be beyond the specs of the suits.

My counter argument was that there was little or no change to the local landing time on the later flights. Challenger was on the surface for 75 hours with an EVA on the last day. It does not fit for me that NASA would have the longer stays if there was any safety issue with the astronauts being out on the surface as the sun moved towards late morning. And besides that, I thought any sunlight hitting the astronauts would be 'direct' no matter how low the sun was in the sky!

Jim Behling
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Posts: 693
From: Cape Canaveral, FL
Registered: Mar 2010

posted 07-12-2014 10:48 PM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Peter downunder:
And besides that, I thought any sunlight hitting the astronauts would be 'direct' no matter how low the sun was in the sky!
You are correct. There is no atmosphere to attenuate the sunlight at low angles.

And actually, the sun at low angles would be hitting the astronauts "broadside," where as sun higher in the sky would have a smaller "target" to shine on.

Also, it is the same sun during the transearth EVAs.

Peter downunder
Member

Posts: 37
From: Lancefield, Victoria, Australia
Registered: Apr 2012

posted 07-13-2014 12:15 AM     Click Here to See the Profile for Peter downunder   Click Here to Email Peter downunder     Edit/Delete Message   Reply w/Quote
You guys are a breath of fresh air. The three points you raised, Jim were in my argument. Especially the low angle causing the astronaut to be if anything, more exposed than when its overhead. We discussed the regolith heating up as the day goes, but I understand its not a good conductor and as it will only conduct through the soles of the feet...

He looked at me like I just stepped out of a... I don't know; a strange thing for a person to step out of.

moorouge
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Posts: 1777
From: U.K.
Registered: Jul 2009

posted 07-13-2014 01:33 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
A full discussion of constraints on Apollo lunar landing times can be found here and here.

Peter downunder
Member

Posts: 37
From: Lancefield, Victoria, Australia
Registered: Apr 2012

posted 07-13-2014 04:05 AM     Click Here to See the Profile for Peter downunder   Click Here to Email Peter downunder     Edit/Delete Message   Reply w/Quote
Thanks for your help. An excellent source from NASA. I would say 'nothing can beat that!' But I have a bad feeling...

All times are CT (US)

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