Service Module design

The Apollo SM had to support the weight of the CM and LES at 4Gs. That
meant that it had to have strong walls. I was wondering what if the
S-IVB panels were designed to support the interface of the CM and SM.
That means that the SM walls could be a lot lighter. Which means that
the SM would have had to carry less fuel. Which means the overall
payload would have been lighter. Would that design have been better?
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Jud McCranie wrote in
:

The Apollo SM had to support the weight of the CM and LES at 4Gs. That
meant that it had to have strong walls. I was wondering what if the
S-IVB panels were designed to support the interface of the CM and SM.
That means that the SM walls could be a lot lighter. Which means that
the SM would have had to carry less fuel. Which means the overall
payload would have been lighter. Would that design have been better?

The weight tradeoff would have had to go into other structures to
support different loads; probably would have meant the CM would have
been heavier.

How much lighter is a "lot"? I suspect not much.

--Damon

On Jul 20, 3:44�am, Damon Hill wrote:
Jud McCranie wrote :

The Apollo SM had to support the weight of the CM and LES at 4Gs. That
meant that it had to have strong walls. �I was wondering what if the
S-IVB panels were designed to support the interface of the CM and SM.
That means that the SM walls could be a lot lighter. �Which means that
the SM would have had to carry less fuel. �Which means the overall
payload would have been lighter. �Would that design have been better?

The weight tradeoff would have had to go into other structures to
support different loads; probably would have meant the CM would have
been heavier.

How much lighter is a "lot"? �I suspect not much.

--Damon

actually the SM was designed before a seperate lander was decided on,
it had the thrust to land on moon but no legs

it was seriously overdesigned

On Mon, 20 Jul 2009 02:44:14 -0500, Damon Hill
wrote:

The weight tradeoff would have had to go into other structures to
support different loads; probably would have meant the CM would have
been heavier.

I don't see how the CM would have been heavier - it had to support the
LES anyway. The S-IVB panels would have had to been a little longer,
but you are right - there probably would have needed to be some
support for the SM at the top of the third stage.
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On Sun, 19 Jul 2009 23:46:46 -0400, Jud McCranie
wrote:

The Apollo SM had to support the weight of the CM and LES at 4Gs. That
meant that it had to have strong walls. I was wondering what if the
S-IVB panels were designed to support the interface of the CM and SM.
That means that the SM walls could be a lot lighter. Which means that
the SM would have had to carry less fuel. Which means the overall
payload would have been lighter. Would that design have been better?

I don't know how much lighter they could have made it--it had to be
strong enough to take the thrust of the SPS without collapsing like a
beer can.

take care,
Scott

Jud McCranie wrote:

The Apollo SM had to support the weight of the CM and LES at 4Gs. That
meant that it had to have strong walls.

The walls of the cylinder were actually doors that opened up to allow
access to the components inside...

SM structural strength probably came mostly from the walls between the
bays and the central core structure. (Which makes sense if you
consider that they had to transmit both S-IVB and SPS propulsion
loads.) The diagrams I've seen show the CM support structure attached
to the top of the walls, which lends credence to this thesis.

D.
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Oct 5th, 2004 JDL