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From: (Henry Spencer)
Subject: Re: Apollo Crew Size
Date: Sat, 16 Jan 1999 19:20:10 GMT

In article <77n1nn$661a$>,
Daniel D Waltimire <> wrote:
>I've often wondered if Apollo really needed a three member crew.  As I
>understand it the original ideal was to "man" the vehicle in watches...

Correct.  Remember that the basic design of Apollo was sketched out well
before it became specifically a lunar-landing program; it was meant as a
general-purpose near-Earth spacecraft.  A three-man crew was chosen simply
because that was deemed the minimum which would permit one man on watch at
all times on a long flight.

>but following the flight of Apollo 7, (during which, according to Walter
>Cunningham, the crewman left on "watch" while his crewmates slept,
>inevitably seemed to fall asleep himself), this was not done.

There were a variety of problems, some of which had started to show up
during Gemini, with rotating watches.  It was hard for the guy on the
graveyard shift to stay awake if he did nothing; it was hard for the rest
of the crew to sleep if he talked to the ground and was otherwise active;
it was especially hard for *him* to sleep when the rest of the crew was

However, in fact Apollo 8 ran the same way.  The change came on Apollo 9,
at least partly because the more active schedule, with two separate
spacecraft involved, wanted everyone awake simultaneously for as much of
the day as possible.  So everyone slept at the same time, with the ground
keeping an eye on things via telemetry -- a possibility which had not
been taken seriously at the beginning of Apollo.

>I've often wondered if a two man crew would have been adequate for the lunar

Perhaps.  It would have required some changes, though.  Having three men
aboard did turn out to be very convenient.

>After all, the command module was designed to be flown back solo, so its
>operation should not have been too demanding for a reduced crew.  I don't
>know about the LM's requirements, though I would assume that in the event of
>a serious accident one person would have been able to pilot it back into
>lunar orbit...

Correct.  But docking with the CSM was nearly impossible without the CSM's
active cooperation... which is why the early crews had a rule that the CMP,
who was the key man in that situation, had to have space experience.  (And
docking, as opposed to rendezvous, is not simple to do by remote control.)

Not that something couldn't have been arranged, but it would have changed
the spacecraft and its procedures substantially.

>...some significant increases in endurance and/or payload should have been
>possible even if the switch to a two person crew had been made after the
>design was frozen.

Not really.  The actual consumables for the extra man did not weigh a lot,
especially since they were on the CSM, which had performance margins, and
not on the LM, where every gram was precious.  To see any substantial
advantage, a wholesale redesign would have been needed.  And it wouldn't
have helped the LM, where the weight problems were really acute.

>Though I suppose that much of the "payload surplus" may
>have been spent giving the LM a larger safety margin fuel wise.

No, the LM's fuel margin was substantially reduced as experience built up,
and none of the landings was really short on fuel.  (The low-fuel alarm on
Apollo 11 was a false alarm, caused by sloshing as Armstrong maneuvered.)
The good old days                   |  Henry Spencer
weren't.                            |      (aka

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