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Why intertank instead of common bulkhead in S-IC?



 
 
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  #1  
Old November 21st 12, 06:58 PM posted to sci.space.history
Alejandro Zuzek[_2_]
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Default Why intertank instead of common bulkhead in S-IC?

So why did the S-IC stage have an intertank structure between the fuel and LOX tanks, while the S-II and S-IVB Saturn stages saved weight by having a common bulkhead between their LOX and H2 tanks? I know that the S-II was the last of these three stages to be designed so it had to compensate the weight increase of the CSM+LM stack while the design of the other two stages was pretty much frozen and that was the reason they chose the common bulkhead design over the intertank structure. But on the other hand, S-IVB was designed before S-II, before the weight problems became apparent and it still had a common bulkhead. So why wasn't the same weight saving design used in S-IC?
  #2  
Old November 21st 12, 07:43 PM posted to sci.space.history
Brian Lawrence
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Default Why intertank instead of common bulkhead in S-IC?

On 21/11/2012 17:58, Alejandro Zuzek wrote:
So why did the S-IC stage have an intertank structure between the fuel and LOX tanks, while the S-II and S-IVB Saturn stages saved weight by having a common bulkhead between their LOX and H2 tanks? I know that the S-II was the last of these three stages to be designed so it had to compensate the weight increase of the CSM+LM stack while the design of the other two stages was pretty much frozen and that was the reason they chose the common bulkhead design over the intertank structure. But on the other hand, S-IVB was designed before S-II, before the weight problems became apparent and it still had a common bulkhead. So why wasn't the same weight saving design used in S-IC?


I'm guessing, but probably because the propellant (kerosene) was
at ambient temperature, whereas both LH2 & LOX were very cold
(-423 F for LH2 & -297 for LOX).

--

Brian W Lawrence
Wantage
Oxfordshire
  #3  
Old November 21st 12, 08:55 PM posted to sci.space.history
Alejandro Zuzek[_2_]
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Default Why intertank instead of common bulkhead in S-IC?

On Wednesday, November 21, 2012 3:43:31 PM UTC-3, Brian Lawrence wrote:
I'm guessing, but probably because the propellant (kerosene) was at ambient temperature, whereas both LH2 & LOX were very cold (-423 F for LH2 & -297 for LOX). -- Brian W Lawrence Wantage Oxfordshire

That could be the reason, although the lox lines feeding the F-1 engines ran through the propellant tank, so the insulation problem between kerosene and LOX had been solved, albeit on much smaller surface than a common bulkhead would have.
  #4  
Old November 21st 12, 09:38 PM posted to sci.space.history
Brian Lawrence
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Default Why intertank instead of common bulkhead in S-IC?

On 21/11/2012 19:55, Alejandro Zuzek wrote:
On Wednesday, November 21, 2012 3:43:31 PM UTC-3, Brian Lawrence wrote:
I'm guessing, but probably because the propellant (kerosene) was at ambient temperature, whereas both LH2 & LOX were very cold (-423 F for LH2 & -297 for LOX). -- Brian W Lawrence Wantage Oxfordshire

That could be the reason, although the lox lines feeding the F-1 engines ran through the propellant tank, so the insulation problem between kerosene and LOX had been solved, albeit on much smaller surface than a common bulkhead would have.


The LOX tunnels were 'insulated' by air - there was an air-filled gap
between the LOX-wetted surfaces and the RP1-wetted surfaces.

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Brian W Lawrence
Wantage
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  #6  
Old November 21st 12, 09:53 PM posted to sci.space.history
Jeff Findley[_2_]
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Default Why intertank instead of common bulkhead in S-IC?

In article ,
says...

On Wednesday, November 21, 2012 3:43:31 PM UTC-3, Brian Lawrence wrote:
I'm guessing, but probably because the propellant (kerosene) was at ambient temperature, whereas both LH2 & LOX were very cold (-423 F for LH2 & -297 for LOX). -- Brian W Lawrence Wantage Oxfordshire

That could be the reason, although the lox lines feeding the F-1 engines ran through the propellant tank, so the insulation problem between kerosene and LOX had been solved, albeit on much smaller surface than a common bulkhead would have.


http://www.apolloproject.com/sp-4206/p197.htm

From this diagram, it looks like the "oxidizer suction lines" ran
through "suction line tunnels". Makes you wonder what was between the
tunnels and the lines. At any rate, this design does not look like the
design of the tunnels and lines bear much in the way of similarity,
structurally, to the design of a common bulkhead between a fuel and
oxidizer tank.

Take a look at section [199] below:

http://www.apolloproject.com/sp-4206/xch7.htm

The above hints at the trouble caused by the LOX lines running through
the kerosene tank, which included thermal problems (keeping the LOX
lines cool). A common bulkhead would seem to exacerbate those problems.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer
  #7  
Old November 21st 12, 11:42 PM posted to sci.space.history
Rick Jones
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Default Why intertank instead of common bulkhead in S-IC?

Jeff Findley wrote:

I'd suspect that unless you had really good insulation on the common
bulkhead that the kerosene would gel and maybe even turn solid
(waxy).


How else would one be able to "Light this candle?"
--
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  #8  
Old November 24th 12, 07:13 PM posted to sci.space.history
Me
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Default Why intertank instead of common bulkhead in S-IC?

On Nov 21, 12:58*pm, Alejandro Zuzek wrote:
So why did the S-IC stage have an intertank structure between the fuel and LOX tanks, while the S-II and S-IVB Saturn stages saved weight by having a common bulkhead between their LOX and H2 tanks?So why wasn't the same weight saving design used in S-IC?


Because it was not cost effective. Since it was the first stage, it
took 7 to 11 lb (I don't remember the exact number) of weight savings
to provide one pound of payload mass. It was just easier and cheaper
to have separate tanks

FYI, Atlas has common bulkhead between LOX and RP-1.
 




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