15 Questions about the Moon Landings

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.

SOURCES/FURTHER READING

(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)

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