288 Hours after Lunar Midnight

Roughly 288 hours after Lunar midnight a small gold and silver craft descended from orbit and touched down on the surface of the Moon. The date was July 20, 1969 at 2017Z. Within hours the history books on Earth would change forever.

Here's a little 'factoid' I found interesting. The timing of the Moon landing was very intentional (as one might expect, but maybe not for the reasons you thought). The timing was planned to coincide with Lunar 'morning' on the Moon. Everything had been planned out, but no one had ever actually set foot on the Moon before that day, and no one was 100% certain how all the theories would work. They were pretty confident all the equipment would survive (provided they didn't crash), but the human element still had a degree of uncertainty. How would mankind survive the dramatic temperature swings of the Moon?

Well, for one thing, the astronauts would never experience the full temperature swings on the Moon, they wouldn't be there long enough. A Lunar day is (27) Earth days long. In this time the temperature at the Moon's surface swings from -280F to +260F. Some quick math will tell you this means the temperatures increase from their lowest to their highest at a rate of roughly 40F degrees per Earth day, and that the surface temps would be at about 0F degrees roughly 288 hours after Lunar midnight. This would allow a margin of 3 days (in the event of a problem) before temps reached 120F.

Now, temps don't work the same way on the Moon as they do on Earth because there's no atmosphere to heat up, so the only two ways things get hot is through radiant heat and conductive heat. The space suits were designed to reflect 90% of the radiant heat, and their boots were insulated to isolate conductive heat as much as possible (hence the thick soles on the actual Moon overshoes and the old Moon Boots of the 70's). In any case though, heat was still a concern, especially extreme high temperatures.

Of all the Moon missions, Apollo 17 spent the longest time on the surface of the Moon (3 days). But even Apollo 17 considered heat, so it started earlier (colder) in the Lunar day.

And one other little interesting factoid, Buzz Aldrin reported noticing how his helmet got hotter in the sun than in the shade of the Moon, but noticed no temperature changes in his suit going from sun to shadow. So maybe at the end of the day, the helmet would have been the weak link in Moon EVA's. In any case, the engineers probably planned it just right.

Probably useless trivia, I know, but I thought some might be interested.

Interesting!, there was a lot of planning for the moon landing

a reply to: Flyingclaydisk

I doubt you're one for computer games.
But have you ever looked into the Kerbal Space Program?

Your post is pretty detailed, it makes me think you'd really enjoy KSP.

Thanks for the interesting read, as always.

a reply to: Flyingclaydisk

Thanks for that.

Sometimes we forget the concentrated genius represented by the moon landings.

Cheers!

a reply to: Flyingclaydisk


Thanks for this! Interesting. I had not known that the temperature changes by 40 degrees each day in the series of corresponding lunar-earth "days," so I had no idea they had to plan for a range of temperatures that would change each day (instead of the same range of temps each day). Incredible to think of how many factors they had to think of and plan for, and how many minds must have had to have been weighing in on the project to get all aspects covered.

Yes, I've read that they planned the landing to coincide with the lunar morning in that location.

Apollo 15 astronaut reported his Hasselblad camera getting very hot in the sun. I wish I could find the exact quote.

One of the other main reasons for picking the lunar morning was shadows. Shadows cast by objects and crater rims make it much easier to pick out potential hazards ahead. You only have to look at the difference between the Chinese images from orbit, which were all taken at local noon, and those taken by other probes at different times in the lunar day to see how it affects the details that you can see.

a reply to: Flyingclaydisk


Our little friend graphene (in the form of an aerogel) helped to retain heat within the space suits. They made them like little self-contained space ships with their own heating and cooling systems. They were also custom fit.

One of the modern space suit designers is off selling graphene aerogel ski jackets...

Oros Apparel (homepage)

One of these days I'll pull the trigger. I'll give a full report back here on ATS when I do!

a reply to: TEOTWAWKIAIFF

You'll need to provide a source that I think.

The suits were indeed self contained space ships with built in power and cooling, but I don't believe graphene or aerogels were involved

a reply to: TEOTWAWKIAIFF


There was no graphene or aerogel used in the Apollo space suits.

Here is a link to a technical paper of the suits. The various layers of the space suit are listed on page 2-18 of the document (page 36 of the pdf file). This was worn over the water-cooled undergarment. Graphene and aerogel are not mentioned there or anywhere else in the document.

Apollo Operations Handbook: Extravehicular Mobility Unit
[NOTE: Link opens directly to a 144-page PDF file]

a reply to: Soylent Green Is People

I said “modern” not Apollo. Sorry if it sounded that way. The newer models do and that is where that link takes you.

a reply to: Flyingclaydisk

Excellent post, Flyingclaydisk! I remember discussing the subject years ago (How Hot is it on the Moon?), but did not go into mission specifics the way you did.

Two more anecdotes regarding heat:

The Apollo 15 crew commented on the increase in radiant heat from the surface on the third day of EVA:

166:12:19 Irwin: I think we're just getting to a high Sun angle.

166:12:24 Scott: Yeah. I think so, too.

166:12:25 Irwin: Because I notice I feel a little warmer today than I did yesterday. (Pause)

166:12:36 Scott: Yeah, I do, too, as a matter of fact. You're right.

Also on Apollo 15, the LM got warmer than intended. The Grumman engineers studied the issue and realized that they had calculated the reflected heat from the lunar surface based on the assumption that the lunar horizon was flat. The Hadley-Appenine landing site had tall mountains to the east and south that reflected more heat than planned. I don't know if they made changes to the subsequent LMs (particularly Apollo 17, which landed in a valley surrounded on all sides by mountains) to compensate for this.