Apollo Mission: Why 3 Astronauts? Why not two?

[Xavven]

While I was designing a new Moho land and return mission, I started thinking I could really shave some weight if I brought only 1 Kerbal to the surface instead of 2. Then I wondered, why did NASA decide to bring 3 astronauts on the Apollo missions instead of 2? I get why you'd want at least 1 person in the CSM, but couldn't they have saved a lot of mass by making the LEM a 1-man lander? Plus, the CSM wouldn't need as much life support with one less body taking up living space, oxygen, water, and other supplies.

Or were they trying to reduce risk on the surface exploration by having a buddy system?

[shynung]

Or were they trying to reduce risk on the surface exploration by having a buddy system?

Most likely, yes.

I also have to mention that the Soviets' plan for a moon landing (N1-L3) call for 2 cosmonauts; one in the LOK (command capsule), the other in the LK (lander).

I think the idea is that, should the lander somehow failed to return and rendezvous with the capsule, the capsule would return alone to Earth.

Edited April 28, 2014 by shynung

[Mitchz95]

Or were they trying to reduce risk on the surface exploration by having a buddy system?

That's my guess as well. Also, two people can do more science than one.

[shynung]

I thought the Apollo missions were manned by test pilots, not scientists.

[Stargate525]

I thought the Apollo missions were manned by test pilots, not scientists.

They were. There was exactly one geologist on the moon. That's it.

The 2-man reason was indeed for safety. Initially, they weren't 100% certain that an astronaut could GET BACK UP if they fell on the moon. If that had been the case, tripping and dying of suffocation would be the worst death ever.

[DaveofDefeat]

The 2-man reason was indeed for safety. Initially, they weren't 100% certain that an astronaut could GET BACK UP if they fell on the moon. If that had been the case, tripping and dying of suffocation would be the worst death ever.

You mean there's no life alert on the moon?

[luizopiloto]

why three... 2 pilots, witch one is the captain, one for the orbital module, one for the lander... and the engineer...

- - - Updated - - -

depending of the mission, one pilot, one engineer and one medic...

[Dunbaratu]

Simple geometry might have something to do with it. As the radius of a cylinder increases, the volume increase per inch of radius increase goes up exponentially by the square of the radius.

So the amount of additional radius needed to support 3 instead of 2 passengers is less than the amount of additional radius needed to support 2 instead of 1.

And the radius increase drives air resistance, craft instability, and so on.

It may be the case that once you get past the big leap from 1 person to 2, that it's less of a big deal to go a bit further to 3.

[Nibb31]

why three... 2 pilots, witch one is the captain, one for the orbital module, one for the lander... and the engineer...

depending of the mission, one pilot, one engineer and one medic...

There were no "engineers" or "medics".

Except for Jack Schmitt who was the only civilian and a geologist, all NASA astronauts were test pilots with a military background.

These guys considered themselves the best of the best, senior test pilots, and had a huge ego. During Gemini, when the program required mission titles for the crew, the first proposal was to have "Pilot" and a "Co-pilot". This caused a huge protest, because they were senior test pilots and none of them wanted to have the title of co-pilot during a mission. So they came up with the roles of "Commander" and "Pilot" (CDR and PLT in the mission transcripts).

This was carried over for Apollo where the roles were defined as "Commander", "Command Module Pilot" and "Lunar Module Pilot" (CDR, CMP and LMP in the mission transcripts).

After Apollo, for Skylab, the mission roles were CDR, CMP and Science Pilot (for Skylab) or Docking Module Pilot (for ASTP)

[bsalis]

Yeah - I just assumed a "buddy system" as well.

It is pretty common for dangerous tasks to be done by two people, even if only one person is needed. Just so easy to make a mistake while concentrating on whatever you are working on.

[Red Iron Crown]

Simple geometry might have something to do with it. As the radius of a cylinder increases, the volume increase per inch of radius increase goes up exponentially by the square of the radius.

So the amount of additional radius needed to support 3 instead of 2 passengers is less than the amount of additional radius needed to support 2 instead of 1.

And the radius increase drives air resistance, craft instability, and so on.

It may be the case that once you get past the big leap from 1 person to 2, that it's less of a big deal to go a bit further to 3.

[nitpick]Volume goes up geometrically with radius, not exponentially.[/nitpick]

I really don't think radius was the driving factor here, anyway. The upper stage of the Saturn V was significantly wider than the Apollo CSM, so a wider or narrower CSM wouldn't have had much effect on the air resistance effects.

I think the buddy system is the real reason. Far more ways to get into trouble during a surface EVA.

[lajoswinkler]

It's just like diving. You always go with a buddy.

[shynung]

I think the buddy system is the real reason. Far more ways to get into trouble during a surface EVA.

I wonder why the Soviets think one cosmonaut is enough to man the lander? They are known for reliability (their LK lander has redundant engines), so why would they not use a buddy system similar to Apollo?

Or is it a technical limitation of their spacecraft (modified Soyuz)?

EDIT: I read from Wikipedia that later versions of the LK was to carry 2 cosmonauts, so apparently they also plan to land at least 2 men on the moon.

Also, the N1 has only 70% of the Saturn V's translunar capacity, so it's understandable if they tried to shave off mass from the LK/LOK spacecraft by carrying one less cosmonaut.

Edited April 28, 2014 by shynung

[Red Iron Crown]

I wonder why the Soviets think one cosmonaut is enough to man the lander? They are known for reliability (their LK lander has redundant engines), so why would they not use a buddy system similar to Apollo?

Or is it a technical limitation of their spacecraft (modified Soyuz)?

I think your signature just about sums it up. The Soviets' tolerance for risk seemed much greater during the space race.

[shynung]

I think your signature just about sums it up. The Soviets' tolerance for risk seemed much greater during the space race.

I tend to disagree with that view when it concerns manned flights. Soviets are quite cheap on spaceflight at first, because nobody knew how to fly rockets back then, other than a few German scientists. When Vostok 1 flew, the spacecraft's retrorockets could fire automatically even if Gagarin forgot to light them up.

[Nibb31]

I wonder why the Soviets think one cosmonaut is enough to man the lander? They are known for reliability (their LK lander has redundant engines), so why would they not use a buddy system similar to Apollo?

...

Also, the N1 has only 70% of the Saturn V's translunar capacity, so it's understandable if they tried to shave off mass from the LK/LOK spacecraft by carrying one less cosmonaut.

That's exactly the reason. The Soviet lunar stack was much less capable and much more dangerous. The LK could only stay a few hours on the Moon surface, and the crew would have had to stay strapped in their seats for the entire mission. Even if the N1 had reached orbit, the rest of the mission was so risky that they would have been very lucky if the cosmonauts had returned alive.

[shynung]

That's exactly the reason. The Soviet lunar stack was much less capable and much more dangerous.

Signified by said lunar stack demolishing its own launch pad at the second test launch.

[Nikolai]

In addition to the strengths already mentioned here, a three-person crew ensures that the smallest possible clique is also a majority.

[lajoswinkler]

COntrary to the popular opinion, Soviets were very careful about manned flights. It was their lack of other qualities that created the public notion that they carelessly launch cosmonauts into orbit.

[rdfox]

NASA investigated a one-man lunar lander in connection with a "quick and dirty" landing program that would have used a Gemini spacecraft in the "CSM" role, and a one-man *open-cockpit*(!) lander in the LM role. The only real advantage of this was that it would have been able to use a much smaller booster (probably a Saturn IB with Centaur or Transtage upper stage for the trans-lunar and trans-earth transfer burns), since it would have required an EVA to board the lander, an EVA to reboard the command module, and had very limited sample-return capability, plus it would have required re-engineering the long-duration Gemini spacecraft to allow for EVAs and docking to carry the lander to the Moon. Given that Apollo and Saturn V were both well-advanced in design at the time this was proposed, it never really had much of a chance except as a possible backup option in case it became clear that Apollo wouldn't be ready in time.

As for why a two-man lander, it was partly to maximize the amount of science that could be done on the surface, but there was a much bigger reason for it. Simply put, the LMP *was* basically a flight engineer on the lunar missions. Yes, he could take control of the vehicle if necessary, and, in fact, Pete Conrad let Al Bean have control over Apollo 12's LM for a few minutes while on the far side of the Moon, but the LMP's primary role during the landing was to monitor the computer and annunciator panel to keep track of, diagnose, and fix any problems (with the help of mission control) while the CDR handled the actual flying of the landing. Remember, test pilots *are* engineers; they usually have engineering degrees, and are expected to do a lot of engineering analysis of anomalies during flight to be able to work around them and bring the aircraft back in one piece. The whole thing about the "pilot" designation was that the majority of them came from single-pilot flight test environments (fighters, trainers, pure experimental aircraft, etc., where you don't work as part of a crew) and their egos didn't want to admit to being the "lesser" light in the spacecraft on a mission; the "commander" and "pilot" designation got around this by having the implication that both were equal in flying ability, but the commander was the senior officer and thus the one in charge should there be a disagreement. (Yes, this was influenced by their military backgrounds--there's always a commander, a senior officer present at whose feet the buck stops.) Indeed, on the Skylab missions, the Pilot was usually a scientist, too, with the Commander being the only "stick and rudder man" who primarily was a pilot/engineer amongst the three, but the designations were retained because NASA did require even their scientist-astronauts to become pilots who were rated in high-performance jet aircraft (in the form of the T-38). It wasn't until the Shuttle program opened the door to non-pilot astronauts that the more accurate "Mission Specialist" and "Payload Specialist" designations came into being.

As a side note, the single most ridiculous position designation that NASA ever had was on the Apollo-Soyuz mission. For that, the three Apollo crew positions were designated as Commander, Command Module Pilot, and Docking Module Pilot. The Docking Module was not at all a spacecraft requiring a pilot; it was essentially just a docking adapter to mount the androgynous docking system that NASA and the Soviets had developed on an Apollo with minimal work, plus act as an airlock between the Soyuz's 14.7 psi natural air on-orbit atmosphere and the Apollo's 5 psi pure oxygen atmosphere. Really, the designation as DMP was probably a sop to keep "Original Seven" alumnus Deke Slayton (finally making his first spaceflight after it was proven that his atrial fibrillation wasn't a flight-disqualifying issue) happy as to his official role in the mission, as opposed to being designated "third pilot" or "additional crewmember" or something like that...

[deadshot462]

Nice post Rdfox, very informative.

There's a good level of redundancy with 2 LM pilots.

Also, they could have had 2-man crew that abandoned the CSM in orbit, leaving it automated, but I don't think the technology at the time allowed this yet.

Going back to KSP, I still bring 3 kerbals even if only 1 lands because there's quite a bit of science in the orbits between launch and landing.

[Albert VDS]

Also, they could have had 2-man crew that abandoned the CSM in orbit, leaving it automated, but I don't think the technology at the time allowed this yet.

Yeah, the technology just wasn't there to reliably keep the CSM safely unmanned in orbit and dock with it.

[shynung]

Also, they could have had 2-man crew that abandoned the CSM in orbit, leaving it automated, but I don't think the technology at the time allowed this yet.

There's an inherent problem with that approach. Should the lander fail to dock with the automated CSM, all astronauts would either be killed or stranded on the moon, and likely to exhaust their life support system while waiting for a rescue mission. If one stayed in the CSM, he would be able to return to Earth, albeit alone.

And to think that there's a speech prepared for the US president to speak should this ever occured...

Edited April 28, 2014 by shynung

[Camacha]

I think the answer is simple - the redunancy is increased, while risks and the chance or error are reduced. In most dangerous situations it is typical to check each other's work for safety; in climbing, diving, with pilots and so forth. Two people see more than one and you can help each other out when things go awry.

I tend to disagree with that view when it concerns manned flights. Soviets are quite cheap on spaceflight at first, because nobody knew how to fly rockets back then, other than a few German scientists. When Vostok 1 flew, the spacecraft's retrorockets could fire automatically even if Gagarin forgot to light them up.

I agree. People tend to project cold war fears and their (often sparse) knowledge of other Soviet engineering (tanks and tractors) onto the space program. While there are different design strategies in east and west, the Soviets did amazingly sophisicated things back then. People just see what they expect or want to see, unfortunately.

Edited April 28, 2014 by Camacha

[Shuttle]

Very interesting thread, thank you! I googled a little and here is what wiki says about soviet lunar space suit Krechet-94:

http://en.wikipedia.org/wiki/Krechet-94

The suit also featured a metal "hula hoop" ring on the back, which would allow a solo cosmonaut who fell on his back to roll onto his side and use his arms and legs to stand.