Why did NASA send two astronauts to the moon instead of one?

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I can think of a lot of good reasons for both arguments, and the Soviets made the opposite call for their lander, but what I'm interested in here is this:

Given the mass penalty of another man (body weight, supplies, oxygen, propellant) and given the LM's extreme optimization for mass, why did NASA decide that two astronauts needed to land on the moon instead of one?

Obviously this decision was made very early on in the LM's development. NASA must have known what a weight penalty this would impose, and what a crunch this would put on the rest of the vehicle. Was there just not enough confidence with the guidance systems at that time? Was there a strong sense of "you're going to need a buddy system for this to be safe"? Of course, it ended up being the right decision, as Buzz Aldrin came through during the LM's descent for Apollo 11.

Dave Markle

Posted 2015-09-24T13:06:25.480

Reputation: 356

8Several reasons, some of which you already mentioned. Annother one: redundancy. They carried spares of several mission critical components, the astronauts are no exception.Rikki-Tikki-Tavi 2015-09-24T14:07:07.663

4The Soviets worried about their lone astronaut on the Moon. They devised a hoop that fit around the spacesuit; if the astronaut were to fall, the hoop would make sure he ended up face-down and able to get up.Hobbes 2015-09-24T14:35:42.767

1@Hobbes That sounds like the most embarassing thing that could happen to a human: Sent to the moon only to fall down in front of a worldwide TV audience and be saved by a metal hoop.Todd Wilcox 2015-09-24T17:10:53.840

20The most embarrassing thing that could happen would be if the lone astronaut fell on his back and were unable to get up again because his spacesuit was too damn heavy and unwieldy.Hobbes 2015-09-24T17:28:30.227

1@Hobbes That would not have become a popular movie. A bit boring to read about after the first 100 pages. But with sword or axe in hand I think that the fallen knight still could've fought off the moongoblins pretty well for a while.LocalFluff 2015-09-24T19:53:30.803

Why do planes have two pilots?BlueRaja - Danny Pflughoeft 2015-09-24T20:01:59.753

1@BlueRaja: test pilots flew solo in record-breaking runs.Hugh 2015-09-25T00:43:43.927

1@BlueRaja-DannyPflughoeft: so that the other one can bring the passengers down safely. How many passengers did NASA report to the FAA for the moon lander? ;-) And what are the lander's characteristics compared with private and military flights that don't need a copilot? Beyond, "one isn't enough" in both cases, I don't think the reasons translate directly. The two situations are too different.Steve Jessop 2015-09-25T08:49:46.883

I think it's a great question. Note that when we first tried to put a person in orbit, we generally went for "1". I'd never noticed before how bold it was, weight-penalty wise, to go for 2 on the moon. (And I admit I wasn't clearly aware the USSR went with 1.) Great question thanks!Fattie 2015-09-25T12:24:58.510

1They actually wanted to send all three astronauts down to the moon but realized it wouldn't really work out that way. Then one of the engineers uttered "Well, two outta three ain't bad" - it happened to get overheard by a strapping young fellow by the name of Marvin Aday who was touring a the space center on a high school field trip. Marvin would later take the stage name Meat Loaf and bring the line to international fame. Or so I've been told. By no one. Because it didn't happen...corsiKa 2015-09-25T15:37:19.820

Answers

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Even before Kennedy's "we choose to go to the Moon" speech, NASA was working on concepts for Moon missions.

Dr. Robert Gilruth, Director of the Manned Spacecraft Center: "Even before the President's decision to land on the moon, we had been working on designs and guidelines for a manned circumlunar mission. This was done in a series of bull sessions on how we would design the spaceship for this purpose if the opportunity occurred. Our key people would get together evenings, weekends, or whenever we could to discuss such questions as crew size and other fundamental design factors. We believed that we would need three men on the trip to do all the work required, even before the complexity of the landing was added.

One of the reasons a crew of 3 was chosen: with 3 men, you can have a duty roster of 4 hours on, 8 hours off and have one person on duty at all times. This was seen as a requirement for longer missions. In practice, the crew preferred to synchronize their schedules, leaving the spacecraft to be monitored by ground control at times when the crew was asleep.

With 3 crew members available, it made sense to get as many of them on the surface of the Moon as possible. More boots on the ground meant more science could be done.

This book also confirms the safety aspect of having two crewmembers on the Moon.

NASA had a culture of relying heavily on crewmembers. In contrast, the Soviets tried to automate their spaceships to a greater extent (and were able to design for a smaller crew as a result).
This culture came about when the earliest group of astronauts was chosen from the test pilot community; their preference for a hands-on approach influenced the entire space program.

Hobbes

Posted 2015-09-24T13:06:25.480

Reputation: 63 604

42

EVA suits are very difficult for a single person to put on by themselves, so another person was required to help the other astronaut put on their EVA suit. At the very least, it is much easier to do it with help. A single person would have a very difficult time doing this. On the ground a team of people is usually employed to have this happen. Note there are things on the back of the suit that require connections, zippers, etc. Some of these are in very difficult locations to reach.

Incidentally, this is one of the major assumptions that Andy Weir made in The Martian, that a method of putting on an EVA suit by one's self has been found by the time we try to go to Mars.

Some references to the difficulty in putting on an EVA suit:

One might ask, why not wear the suit the entire time? Well, imagine being trapped inside a suit for over 24 hours (28 for Apollo 11, no doubt longer for others), and not being able to take it off at all, except for the helmet. It would get uncomfortable, influence bodily functions, etc. All in all, that is just too long to remain in a space suit if at all possible.

In addition, there are other advantages to having two people on the surface, for redundancy and to allow more to be done. The systems were only semi-automatic, which means another person was another set of eyes to make things easier. Overall, it just made sense to have two people.

PearsonArtPhoto

Posted 2015-09-24T13:06:25.480

Reputation: 67 296

7He also assumed that there was a way to burn Hydrazine so cleanly that you can breath the exhaust without being, dead, dead and dead. So I don't think this is a good reference.Rikki-Tikki-Tavi 2015-09-24T14:09:51.153

1That sequence, by the way, is the one thing he most admits to getting wrong. In any case, I've posted the best sources I can find to getting as to how difficult it is.PearsonArtPhoto 2015-09-24T14:33:08.217

2Interestingly the Soviets designed a suit that would be easier to get into unassisted: the Krechet-94.Hobbes 2015-09-24T14:36:37.150

3Plus "what if something goes wrong?" Specifically, what if something bad "happens" to your astronaut? SciFi and movies aside, in reality there's only one practical help for that situation: another astronaut.RBarryYoung 2015-09-24T23:43:03.680

1This answer begs the immediate question: Why not just wear the space suit during the whole mission? Except maybe for the helmet and backpack, which I'm guessing are a lot easier to strap on. BTW your answer would benefit from a good description of a space suit. Most people seem to assume it's just a big suit, maybe kinda bulky, but in reality there are many layers to it.DrZ214 2015-09-25T03:36:29.333

Regarding spacesuits: Do the spacesuits on the ISS also require two people to put them on?DP_ 2015-09-25T09:33:24.333

@DrZ214: There are a lot of uncomfortable aspects to wearing a space suit, not just the helmet/ backpack. Actually, I suspect the backpack is one of the harder pieces to get on by yourself. Still, I can answer a bit more into it.PearsonArtPhoto 2015-09-25T11:34:50.033

I think NASA can made suit wear from the front and with ease. To help another astronauts to wear a suit send another one is not meaningful here. Because where man can go to Moon, can he/she not able to made a space suit that astronauts can wear without help of another? I don't think so...KTPATEL 2015-09-25T12:45:35.237

5

I cannot comment, but I just wanted to share some information (as I just wrote a paper on Project Apollo). First, there is an excellent resource available from NASA called Chariots for Apollo. The chapter relevant to the question is Chapter 1- Concept to Challenge.

Hobbes' quote is correct, historically, that studies had been undertaken by NACA since the mid 1950s. Pearson is also partially correct that NASA wanted the workload split (for redundancy and other reasons). Project Mercury and Gemini were both adapted to the needs of Apollo. However, another great resource, though not official as per the page, is Guidelines for Advanced Manned Space Vehicle Program. You will want to pay special attention paper written by Stanley C. White Human-Factors Considerations.

NASA decided on two astronauts for many reasons, with only some given by Hobbes and Pearson. Hopefully, the provided resources will help explain some other reasons aside from the work and abilities of the astronauts.

Personally, and without justification, I feel NASA chose multiple astronauts because they did not understand how extended and stressful missions in space might affect a human. I believe this is somewhat shown by the following example. NASA quarantined all Apollo astronauts for 21 days, up until they realized there was no chance for them to bring back anything dangerous.

I also feel their answers ignore the political ramifications behind Apollo (NASA was pressured to meet the decade goal), but that is a topic for another day.

In response to the mass penalty, from the provided resources you can see that NACA and subsequently NASA originally prepared for a mission with far more available resources. Mass in the preparatory stages was not considered to be an issue. The Goett Committee fully expected a two week long mission (against the 8 day Apollo 11 mission).

spacer

Posted 2015-09-24T13:06:25.480

Reputation: 169