Armstrong and Aldrin were the first two people on the Moon when Apollo 11 landed there in July 1969. This astonishing achievement (which it should not be forgotten was followed by five more successful landings) continues to fascinate our readers who are still eager to learn more about the details.

Here are a list of questions submitted by an Astronotes reader and my answers, some short, some lengthy. I have quoted the questions exactly as asked apart from slight changes to word spacing and punctuation (quotation marks around some words are as used in the original questions). In the questions LEM stands for Lunar Excursion Module, an name for the Apollo Lunar Module (LM) that was used in the early stages of the craft’s development. Other abbreviations used here are EVA (Extravehicular activity) and CSM (Apollo Command/Service Module).


1. “The average man consumes approx.100 litres of air/hour. How much air did Armstrong and Aldrin carry with them during their moonwalks and how was this achieved?”

Several clarifications must be made before it is possible to answer this. The air we are used to breathing at sea level is mostly nitrogen, only a fifth of it is oxygen. The nitrogen is not used at all in respiration, only the oxygen is. Although the average person might inhale about 100 l of air per hour (so 2400 l per day), only 560 l of oxygen is consumed per day. To save weight in the Apollo spacecraft a pure oxygen atmosphere of only about a third standard atmospheric pressure was used (5psi compared to 14.7psi). Lower pressure allowed a light-weight structure. The Apollo spacesuits were pressurised to 3.5-4.0 psi. The astronauts were not consuming 100 litres of air per hour.

Human lungs take in the oxygen we need to live from the air, but they are not 100% efficient absorbers of oxygen. They are a gaseous exchange mechanism, excreting carbon dioxide as they take in oxygen. Only about 5% by volume of the oxygen in the air inhaled in each breath is used by the body, the rest is exhaled along with carbon dioxide in the breath out. Sealed in a box an astronaut can breathe the air, slowly consuming oxygen, but with each breath out that air is becoming laden with toxic carbon dioxide. In the Apollo spacesuits and spacecraft, the air was “scrubbed” through lithium hydroxide to remove carbon dioxide so it could be rebreathed, so air was not just inhaled once and discarded. This rebreathing system in the Apollo spacesuit is said to have been “20 per cent more efficient than a traditional aqualung.”

Some features of an Apollo Portable Life Support System (PLSS) including the lithium hydroxide canister. (Image credit: NASA)

Some features of an Apollo Portable Life Support System (PLSS) including the lithium hydroxide canister. (Image credit: NASA)


To answer the original question, the spacesuits used on the Moon are described in detail in the document APOLLO OPERATIONS HANDBOOK EXTRAVEHICULAR MOBILITY UNIT which states on page 2-89 that the suit could be charged with “1.340 pounds of usable oxygen for EVA” and goes on to say “This oxygen supply is ample for a 5-hour EVA”.


2. “With this in mind how long did they both stay outside the lander?”

For Apollo 11, the sole EVA lasted 2 hours, 31 minutes 40 seconds. On later missions much longer EVA sessions were made, the longest being Eugene Cernan and Harrison Schmitt’s grueling seven and a half hour  marathon in December 1972. Apollos 15-17 used an up-graded spacesuit, the A7LB,  which carried more oxygen, lithium hydroxide and cooling water to permit longer EVAs.


Astronaut and lunar module pilot Buzz Aldrin moves toward a position to deploy two components of the Early Apollo Scientific Experiments Package (EASEP) on the surface of the moon during the Apollo 11 extravehicular activity. The Passive Seismic Experiments Package (PSEP) is in his left hand; and in his right hand is the Laser Ranging Retro-Reflector (LR3). Mission commander Neil Armstrong took this photograph with a 70mm lunar surface camera. (Image Credit: Neil Armstrong/NASA)

Lunar module pilot Buzz Aldrin moves toward a position to deploy two components of the Early Apollo Scientific Experiments Package on the surface of the moon during the Apollo 11 extravehicular activity. The Passive Seismic Experiments Package is in his left hand; and in his right hand is the Laser Ranging Retro-Reflector. Mission commander Neil Armstrong took this photograph with a 70mm lunar surface camera.
(Image Credit: Neil Armstrong/NASA)

3. “Neil quote “we are kicking up some dust”. No dust on lander feet and not even the slightest evidence of dust having been disturbed under the lander’s engine outlet. Why not?”

A rocket or jet powered vehicle descending in a dusty landscape on Earth will blow up billowing clouds of dust particles which slowly descend, buoyed up by air resistance. This is demonstrated spectacularly by this video of Blue Origin’s New Shepard booster returning to Earth.

However unlike Earth, the Moon has no atmosphere, and that means dust behaves differently. Dust particles are blown up by rocket thrust on the Moon, but fall straight to the ground again. This means that the descending LM was not surrounded by a billowing dust cloud. Also the Descent Engine was throttled back in the final stages of landing and in fact was shut down 5ft above the surface. The chances of dust gathering on the pads was very low as the dust than can be seen being blasted away in films of the landing is blowing underneath, rather than over, the footpads. The claim that the lunar surface under Apollo 11 Descent Engine’s nozzle is undisturbed is not true as can be seen in the image below (similar images were taken on other missions). Rather than being non-existent, the surface disturbance by landing spacecraft has been studied by geologists and engineers trying to see if we can learn anything to help design future missions. An example of this research can be seen in this article’s further reading section.


LM descent engine bell and exhaust rays in lunar soil. (Image credit: Neil Armstrong/NASA)

LM descent engine bell and exhaust rays in lunar soil. (Image credit: Neil Armstrong/NASA)

4. “How much water was required in the space suits to provide cooling and heating and how was this cooling and heating achieved in a split second moving from sunlight to shade?”

More details of the PLSS and its Remote Control Unit. (Image credit: NASA)

More details of the PLSS and its Remote Control Unit. (Image credit: NASA)


For Apollo 11 each A7L spacesuit carried 8.5 lbs (3.9 l) of cooling water according to the document PLSS Technical Information. I am not sure if “split second” temperature adjustment was essential, the wearer could adjust the temperature from a thermostat on the Remote Control Unit on the spacesuit’s chest. Riley and Dolling report that

The water cooling proved very effective on the Moon – with astronauts reporting immediate warming or cooling in response to their controls

5 “The ‘famous’ Armstrong foot print shows a deep tread pattern. His suit which is now undergoing requests for funding to preserve it shows NO tread pattern on the boots. Explain please.”


Aldrin's boot print on the Moon in 1969. It will still be there now. (Image credit: Neil Armstrong/NASA)

Aldrin’s boot print on the Moon in 1969. It will still be there now. (Image credit: Neil Armstrong/NASA)

The spacesuit has relatively thin integral soles but for walking on the Moon, sturdier overshoes were worn over the pressure suit. These had  thick insulating silicon rubber soles.

The Apollo spacesuit overshoes, the original "Moonboots" (Image credit: NASA)

The Apollo spacesuit overshoes, the original “Moonboots” (Image credit: NASA)

6. “These moonwalking suits were supposedly designed to withstand incredibly harsh conditions with rapid heat changes, potential meteorite hits,radiation etc. How can it require restoration and preservation so soon after the event when we can see in museums Henry VIII’s clothes from 500 years ago?”


Neil Armstrong's lunar EVA suit photographed in July 1969 before the flight. Note the overshoes. (Image credit: NASA)

Neil Armstrong’s lunar EVA suit photographed in July 1969 before the flight. Note the overshoes. (Image credit: NASA)

I am not sure that many original clothes of Henry VIII (1491 – 1547) actually do exist to be displayed in museums to this day;  the sole item I know of is the Cap of Maintenance preserved in Waterford . I wonder if the question was inspired by seeing reproductions of Tudor clothing on display.

The Apollo spacesuits were indeed designed to resist the hostile environment of space on a single mission, but unlike the suits used by ISS crews today they were not meant for use over a prolonged time. In fact they were rated for a service life of six months. More than forty years later the Apollo suits are aging badly, the internal layer made from a rubber and neoprene mix is brittle and crumbling despite careful storage in climate-controlled conditions at the Smithsonian Institute. Even twenty years ago the clear PVC tubing in the cooling garments was turning brown. A more subtle issue is that outer fabric of the suits includes Nomex and Teflon, material with less “give” than cotton or wool.  Existing museum manikins for displaying historic garments do not provide enough support to heavy spacesuits, stressing and damaging them as they are displayed. The Smithsonian is currently restoring Armstrong’s suit to appear as it did immediately after the mission ended and developing a custom manikin to allow the suit to be put on display again.

7. “Did the LEM door open inwards or outwards? If it opened inwards how did the two astronauts get out as there was allegedly no room with all their kit on?”


Aldrin backing out throughthe LM's hatch (Image credit: Neil Armstrong/NASA)

Aldrin backing out through the LM’s hatch (Image credit: Neil Armstrong/NASA)

It opened inwards and to the right. The hatch was designed this way so that the internal air pressure would keep it firmly closed (even if the latch failed) by seating it against the edges of the opening. The claim that there was no room for the astronauts to move through the hatch way  is false. It was awkward, leaving the cabin required the commander to crawl out first, then the lunar module pilot closed the hatch, moved across the cabin and reopened the hatch before exiting. Getting back in was just as inelegant a process. Both procedures were rehearsed in mockup LMs on Earth and on a “vomit comet” microgravity simulation aircraft.

8. “Did the LEM have an airlock, if so how was it pressurised and depressurised or did they remain fully suited throughout?”

This interior view of the Apollo 11 Lunar Module shows Astronaut Edwin E. Aldrin, Jr., lunar module pilot, during the lunar landing mission. This picture was taken by Astronaut Neil A. Armstrong, commander, prior to the moon landing.

This interior view of the Apollo 11 Lunar Module shows Aldrin without a spacesuit  during the lunar landing mission. This picture was taken by Neil Armstrong prior to the moon landing. (Image credit: NASA)

No, the Lunar Module did not have an airlock, just like in the Apollo Command/Service Module (CSM) and earlier Gemini spacecraft the cabin was depressurised by venting the air into space to let the crew out and repressurised on their return. Obviously this means everyone must wear a spacesuit while an EVA is underway. The crews were not required to wear spacesuits when the cabin was pressurised.

9 “Did Armstrong and Aldrin wear their suits and helmets when entering the LEM from the command module and when returning to the command module?”

Neil Armstrong operating the onboard television camera while positioned in the CM/LM tunnel. (Image Credit: Michael Collins/NASA)

Neil Armstrong operating the onboard television camera while positioned in the CM/LM tunnel. (Image Credit: Michael Collins/NASA)

No, this was unnecessary as the craft shared a common atmosphere when connected.

10. “How was the LEM reattached to the command module and did this require an airlock?”


The Apollo Docking Mechanism used on the Moon missions and to dock with Skylab and Soyuz 17.

The Apollo Docking Mechanism used on the Moon missions and to dock with Skylab and ASTP docking module.

There was a purpose-designed docking system using a probe on the CM which engaged with a drogue on the LM ensuring that both vehicles were correctly aligned. Once this occurred latches on the CM and LM’s docking rings engaged forming a “tunnel” between the craft. The probe and drogue mechanism was removed and stowed to allow the astronauts to transfer between vehicles. No airlock was required. More detail about this can be found in the chapter Docking and Transfer of the Apollo Operations Handbook.


11. “What were the odds that every Apollo mission except for 13 went without any major incident?”

The Apollo 13 explosion was by far the worst of several near disasters during the lunar missions, but Apollos 8, 10-12 and 14-17 all successfully sent three people to the vicinity of the Moon, carried out a planned mission and returned them. Apollo 13 got the crew to the Moon and back but failed at the mission. These could be interpreted as an 8/9 (88.9%) mission success rate and 100% crew survival rate. In 1965 NASA regarded acceptable success rates to be 90% for mission success and 100% for crew survival so they matched their target pretty well.

12. “Is it true that the LEM motor could only be fired once after which it required a rebuild. Depending on this being true how was it used to land and then be reused to launch away from the lunar surface?”


This diagram shows the layout of the fuel (propellant and oxidiser) takage in both sections of the Lunar Module. (Image credit: NASA)

This diagram shows the layout of the fuel (propellant and oxidiser) tankage in both sections of the Lunar Module. (Image credit: NASA)

This is another question which needs clarification before it can be answered. The Lunar Module had two separate and independent rocket motors. These were the Descent Engine (for descending from lunar orbit to the surface) and the Ascent Engine used to send the Lunar Module’s Ascent Stage back into lunar orbit. You can see the locations of both rocket engines in a cutaway diagram from a 1969 issue of Flight magazine (link). The Descent Engine was left behind when the crew departed the Moon in the LM’s Ascent Stage. Both engines were intended to be used only once each on a mission.

13. “In the film Apollo 13, if it was a true story, why were the astronauts not frying to death rather than freezing to death as shown.”

Most heat generated on board a spacecraft is waste heat from the equipment on board. On the real Apollo 13 mission, after the explosion in the Service Module all power was lost from the fuel cells, so for the four day return journey the crew had to rely on the LM’s batteries (designed for a 2.5 day life). To conserve power all non-essential systems were turned off or powered down to as great an extent as possible. This meant much less heat was being generated so the cabins of both the LM and CM cooled. The astronauts were uncomfortable but not in danger of freezing. Just how cold they got is unclear and the Apollo 13 movie may have exaggerated this to heighten the drama. In an article at Universe Today NASA engineer Jerry Woodfill said

Someone did a later study about how cold Apollo 13 actually was. I know that 38 degrees F was sort of accepted as the temperature during the rescue. (This was the reported temperature in the far reaches of the dead Command Module quarters where Jack Swigert dwelled.) But other analysis found an environment not nearly as cold, especially in the lander. The customary “barbeque-rotational-solar” heating was always present.

14. “Why did the astronauts not take photos of the stars during the dark periods e.g. while orbiting around the so called dark side?”

Photographing the stars was not a goal of Apollo missions, successfully getting to the Moon and back was. Why should it have been? I cannot see what the advantage would have been in photographing stars from spacecraft that were not purpose-built astronomy platforms. There have been numerous dedicated astronomy missions since which have imaged stars and other objects.

15. “The so called ‘earth rise’ photo from NASA shows earth totally out of proportion considering it is much larger than the moon. Why is that?”

I am assuming that the question refers to the famous Apollo 8 “Earthrise” sequence. Although the Earth is a bit less than four times as wide as the Moon, this still means it is very small in the Moon’s sky. Movies and artists’ impressions are out of proportion as they virtually always grossly inflate the size of the Earth from the Moon depicting it as looming large over the surface. This is not correct. Next time you see a full Moon in the sky, try taking a picture of it with the most basic lens possible and see how small it appears in the image. I did this with the image below of Venus and the Moon (though the Moon is not full) taken with the camera on my phone. Imagine the Moon in the image enlarged four times, it’s hardly going to dominate the image. Better still, compare the Moon in my picture to the Earth in the picture taken by Armstrong from the Moon’s surface.


The Moon-Venus conjunction of 8 December 2015. (Image credit: Colin Johnston/Armagh Planetarium)

The Moon-Venus conjunction of 8 December 2015. (Image credit: Colin Johnston/Armagh Planetarium)


The Earth in the Moon's sky (image credit: Neil Armstrong/NASA)

The Earth in the Moon’s sky (image credit: Neil Armstrong/NASA)

The Earth appears just as it should in pictures from the Moon.

I hope that this article has helped answer these intriguing questions and show that there is nothing mysterious or suspicious about the Apollo missions.


(These are not the “be all and end all” of Apollo sources, they are just what I had to hand while writing this.)

Kozloski, Lillian D. U.S. Space Gear: Outfitting the Astronaut, Airlife Publishing, 1994

Riley, Christopher and Dolling, Phil, NASA Mission AS-506 Apollo 11 Owner’s workshop Manual, Haynes Publishing, 2009

Godwin, Robert, Project Apollo: Exploring the Moon, Apogee Books, 2006

Godwin, Robert, Apollo 11: First Men on the Moon, Apogee Books, 2005

Philip T. Metzger, John E. Lane, Christopher D. Immer, and Sandra Clements, “Cratering and Blowing Soil by Rocket Engines During
Lunar Landings” (August 11, 2008). International Conference on Case Histories in Geotechnical Engineering. Paper 1.

(Article by Colin Johnston, Science Education Director)



John · December 10, 2018 at 13:20

It’s all a lie. Chris Duncan was the first in space.
The hoover named Henry was made in 1969, The moon landing was in 1969, coincidence? I think not!
Numatic International, was founded in preparation to send Chris Duncan into space.
That’s why space is a vacuum!?!?!?!?!?!!?
St Pauls Catholic School.

K E Jurgensen · October 9, 2018 at 22:56

Don’t believe much in conspiracy theories, but after watching a NASA movie real today, please answer a question. Dont see this answered anywhere else

The movie real shows Neil dropping a feather and a hammer and they both drop sort of rapid to the ground. OK. Gravity works even on the moon. (1/6 gravity I believe)

If a feather falls to the ground, why doesn’t the flag droop to the ground? Gravity is the same for all mass is it not?

    admin · October 10, 2018 at 14:22

    Hello, thank you for the comment. You have to remember that on the moon the flags were held in place by different rods. The video you see where the flag’s moving is because the astronaut just placed it there, and the inertia from when they let go kept it moving and the astronauts also accidentally bent the horizontal rods holding the flag in place several times, creating the appearance of a rippling flag in photographs.

    If the rods hadn’t been in place then yes the flag would have drooped to the ground 🙂

Telit Likitis · October 8, 2018 at 05:06

Just Embarrassing that human beings believe this Fairytale.
In 1969 NASA did not even have the correct distance to the moon. Their pressurized space suits were “sealed”….. with zippers….That alone is too funny. They supposedly were able to talk (with 1969 technology) and communicate from 200,000 miles away !! That by it self is ABSURD and obviously IMPOSSIBLE as was the staged “phone call” to the Whitehouse.
ALL of the telemetry is GONE ..NASA misplaced it ! Yeah that believable as is 95% of the footage.. Gone…. Riiiiight

    admin · October 8, 2018 at 10:51

    Just in regards to your zipper comment, you have to understand that it wasn’t just any old zipper like you would get on a pair of jeans. The zipper enclosures on Armstrong’s spacesuit actually consisted of three layers. Two brass zippers sandwiched a rubber layer: zipper, rubber, zipper. When pressurised from the inside of the spacesuit, the rubber expanded and created a seal between the two zippers. Hope this helps!

Diga · September 18, 2018 at 23:40

Explain me this.

When Apollo 17 lifted off from the moon, a camera captured the movements of the spacecraft — even though nobody was left behind to, say, establish a lunar base. How was that possible? With a camera on the lunar rover that could be controlled — or even programmed — from Earth.
Pretty impressive technology for the takeoff 42 years ago yesterday (Dec. 14) in 1972, although it took three tries to get the technique right.
As the Smithsonian National Air and Space Museum explains in a 2011 blog post, the camera was available on Apollos 15, 16 and 17. The television camera communicated from Earth using a high-gain antenna on the rover, but there was a slight time delay for the radio waves to travel (a couple of seconds) between the Earth and the Moon.
So the engineers suggested moving the rover a certain distance from the lunar module and setting the camera to automatically tilt to show the lunar liftoff when commanded from Earth.
That was the plan, at least. On Apollo 15, the tilt mechanism malfunctioned and the camera never moved upwards, allowing the lunar module to slip out of sight. And while the attempt on Apollo 16 gave a longer view of the lunar module rising up, the astronauts actually parked the rover too close to it, which threw off the calculations and timing of the tilt upwards so it left view just a few moments into the flight.
Ed Fendall was the person doing the controlling. In an oral history for NASA done in 2000, he recalled how complex the procedure was.
Now, the way that worked was this. Harley Weyer, who worked for me, sat down and figured what the trajectory would be and where the lunar rover would be each second as it moved out, and what your settings would go to. That picture you see was taken without looking at it [the liftoff] at all. There was no watching it and doing anything with that picture. As the crew counted down, that’s a [Apollo] 17 picture you see, as [Eugene] Cernan counted down and he knew he had to park in the right place because I was going to kill him, he didn’t — and Gene and I are good friends, he’ll tell you that — I actually sent the first command at liftoff minus three seconds. And each command was scripted, and all I was doing was looking at a clock, sending commands. I was not looking at the television. I really didn’t see it until it was over with and played back. Those were just pre-set commands that were just punched out via time. That’s the way it was followed.

dw817 · May 10, 2018 at 05:45

Just beautiful. My Dad’s ashes were launched on the Celestis Space Flight as it was his dream to enter space. It was quite an event.

martin avancena · March 30, 2018 at 14:02

I’d like to know why nearly 50 years after the Apollo moon landing, Russia and even China or the Europeans are still trying to solve the technical problems of sending their men on the moon and getting them back to earth safely. The Americans did this routinely several times with primitive technology by today’s standards when my GREAT GREAT Grandfather was still well alive and kicking in his early 70s. Aviation progressed from flimsy rickety biplanes to sophisticated supersonic jets in less than 50 years!

Russia and China would do anything to match American technological achievements. And to think the Russians were initially ahead in the space race. Its just quite incredible that 50 or maybe even more years is not enough time for them to duplicate this ancient American feat.

Ritchie · March 9, 2018 at 20:17

Photos show Buzz at the base of the ladder on the lander. The bottom rung looks to be over waist high. I have not seen any photos of anyone jumping that high on the Moon. How did the Astronauts get up onto the ladder to reenter the module?

semaj · October 9, 2017 at 12:58

My posts deleted again! Does this mean you do not have an opinion or answers?

    admin · October 17, 2017 at 13:52

    Hi, this blog has been changing admins for a little while, so apologies if your comments have been erased. Could you please repeat your question?

    richard Nasa · February 1, 2018 at 03:21

    seeing how big the moon is here on earth, if earth is larger than the moon at a familiar distance, how good this picture of earth with no stars be real?

Ron Nowlan · October 5, 2017 at 15:43

Did the astronauts have their suits OR helmets on when first landing on moon happened? Was it necessary to wear their suits OR helmets in case of a mishap?


    admin · October 17, 2017 at 13:48

    When landing on the moon, to actually physically walk on the moon, the astronauts needed to wear their full suit, helmet included. This is because there is no air on the moon and so it allowed them to breathe. The suit is also able to regulate body temperature and would have devises inside for communication.

    I hope this helps

anthony andrea · September 23, 2017 at 14:59

How did the crew service and replenish their suits between EVA’s on the missions where they went outside more than once? – they needed to recharge the batteries, refill it with ice and oxygen – how was this accomplished? How did they deal with the highly abrasive dust – keep it out of joints and seals etc?

semaj · September 7, 2017 at 20:29

My comments deleted, wonder why that is?
I will try another way by asking the question as follows ref. picture ‘the earth in the moon’s sky’. Does the administrator or anyone that uses this site think that the engineering and finish on the lunar module is unbelievably poor? Please can someone tell me how the return module was disconnected from the LEM base on take off?

    admin · September 8, 2017 at 13:47

    Hi! In regards to your question, the crumpled-looking silver-coloured material on either edge of the LM is, in all probability, thermal insulation
    and, as far as I know, it is supposed to look exactly like that.

    On the subject of how the LM separates from the descent stage upon liftoff from the lunar surface
    I would you to this site:

Bk · April 8, 2017 at 21:41

Why none of the missions carried water? They could have poured the liquid and studied the reactions. If they can play golf, why didn’t they spray water?

There was a video in which one of the astronaut was hitting something with a hammer the loud thud was audible. How is that possible if no sound waves can travel in vaccum?

    George Birch · April 29, 2017 at 01:58

    Where “was” this video? It’s a shame it no longer exists (as you imply,) as this renders it impossible to analyze.

    dw817 · May 10, 2018 at 05:50

    BK, I was wondering about the water situation too. Yet – it’s possible that if water were introduced to the moon’s “atmosphere” that it could cause serious problems. like burn up in a bright and dazzling line of fire or freeze up and become as sharp and solid as a razor blade.

    It is also possible that since there was no water on the moon, it might have disastrous effects to the “ecology” of the moon, little that it is. Likely they took all of this into consideration in their exploration and experiments.

    C J Southern · October 13, 2018 at 09:25

    Re: Hammering sounds heard. Sound waves indeed cannot travel in a vacuum, but the astronaut isn’t in a vacuum; the inside of his suit is filled with oxygen. Vibrations from the hammer strike travel through the suits atmosphere to the microphone.

    AK · October 21, 2018 at 04:53

    The answer to this one is pretty obvious. You are hearing the “sound” of the hammer through the astronaut’s microphone, which is inside his space suit, and his suit does have an atmosphere for sound to travel through. Sound is just vibrations. You can see in the video he is hitting the pole with a hammer and holding the pole with his other hand at the same time. So the vibration of the hammer strike goes through the pole to his gloved/suited hand, the suit vibrates as a result, that vibration travels through his suit and thus into the air/atmosphere inside his suit, and then the air vibrates and the “sound” (air vibration) propagates to his microphone, which you then hear from his broadcast. Pretty basic stuff if you take a moment to think about it.

    Alan · March 20, 2019 at 12:24

    In a vacuum water will instantly boil so any attempt to drop water would have failed it would also have probably been hazardous
    for an Astronaut to try doing this.

Alias · August 10, 2016 at 15:14

I’d just like to have this cleared up, you state that on Apollo 13 the astronauts experienced cold but how is this possible. Let me explain, with a direct path to the sun and how heat travels through radiation, once the Suns Ray’s hit matter wouldn’t they instantly heat what ever matter was in there path? In fact wouldn’t Apollo of needed the same water cooling tech as the suits? Only without the shadow of the moon to “hide” in; would of it needed extreme liquid cooling. More so than was capable to carry? And if you use the spinning argument of the craft (to cool) with no molecules in space or almost none, how would spinning away from the sun help cool something down in a vacuum? Add to that the heat sources of convection and conduction which would apply once radiation hit matter and warmed it, how on earth wasn’t they boiled alive?

    admin · August 11, 2016 at 11:42

    Dear Alias, thank you for your questions.

    with a direct path to the sun and how heat travels through radiation, once the Suns Ray’s hit matter wouldn’t they instantly heat what ever matter was in there path?

    Yes, any object (such as the spacecraft) exposed to sunlight will warm up where the Sun’s rays fall on it. However, not all the energy on sunlight will warm up the spacecraft, a significant portion is reflected off. Then, the spacecraft eventually will reach thermodynamic equilibrium when it is radiating as much energy as it absorbs so it will not keep on getting warmer indefinitely. In the vacuum of space radiation heat is the only way to lose heat but it is effective. The crew are not going to “boil alive” at the distance the Earth and Moon are from the Sun.

    Solar heating is not a big problem in designing a spacecraft to carry people, instead removing waste heat from the spacecraft’s systems is the biggest thermal regulation issue and must be done to protect the crew. You are quite correct in saying that the Apollo spacecraft had liquid cooling systems. The CSM had large radiator panels, these are the white areas on the drum-shaped Service Module while the LM sublimated water carrying waste heat directly into space.

    For your interest here is a link to a technical report on the CSM’s Environment Control System which included the cooling system and here is a link to the equivalent document for the Lunar Module.

    The rotation of the spacecraft was planned to even out the solar heat received. The fear (which may have been groundless) was that the heat shield for re-entry could be adversely effected if one side was continuously cold. By slowly rotating the spacecraft so every side was exposed to the Sun during the flight this was prevented.

    I hope this has helped you.

Duncan · May 19, 2016 at 18:29

Fascinating reading. In regards to the Apollo spacecraft atmosphere, due to the fatal Apollo 1 fire, prior to and during launch a mixture of 60% oxygen and 40% nitrogen was used at 16psi to lessen the risk of fire. It was only when in space that they switched to pure oxygen at a reduced pressure. Great article and great pictures. Thank you.

    admin · May 20, 2016 at 08:37

    Dear Duncan, thank you, I’m planning an article on the Apollo CSM and I will include that.

      Alan · March 20, 2019 at 12:29

      Great article thanks for sharing, a lot of details in there I hadn’t heard before. look forward to more interesting stuff.

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