Ex Luna, Scientia

(it is never clear to me why exactly the third stage of the Saturn V did not share the same 10 meter diameter the lower 2 stages had--if that were done, the stack would be shorter, meaning if the lower stages could pack a bit more punch, a bigger third stage could fit in the same height limit as the old Apollo stack)
The SIVB stage contained about 104 tons of fuel, with hydrogen/oxygen fuels averaging to a density of about 0.358 tons/m^3, giving a volume of about 290 cubic meters. Thus, it's easy to work out that the tanks at 6.6m diameter the tanks would be about 8.5 m long (the other ~10m of the stage length were the thrust structure and engine). Hence why they didn't go to with a 10m stage IOTL--the tanks would have been too short to be structurally efficient, without much change in length of the total stage.
 
(it is never clear to me why exactly the third stage of the Saturn V did not share the same 10 meter diameter the lower 2 stages had--if that were done, the stack would be shorter, meaning if the lower stages could pack a bit more punch, a bigger third stage could fit in the same height limit as the old Apollo stack[/i[) dramatically upgraded missions could still be achieved

The SIVB stage contained about 104 tons of fuel, with hydrogen/oxygen fuels averaging to a density of about 0.358 tons/m^3, giving a volume of about 290 cubic meters. Thus, it's easy to work out that the tanks at 6.6m diameter the tanks would be about 8.5 m long (the other ~10m of the stage length were the thrust structure and engine). Hence why they didn't go to with a 10m stage IOTL--the tanks would have been too short to be structurally efficient, without much change in length of the total stage.

If the third stage were a good deal bigger, which he indicates as a goal, then the structural efficiency problems should have been obviated, and as he says, you could squeeze a good deal more capability into a stack that could stand in the existing VAB. Of course, IOTL they were able to make do with the smaller cheaper, already developed(and therefore, again, cheaper) 260 inch third stage, and they did so.

As an upgrade path, with good funding(always an exciting and tenuous prospect), the 396-in option provides a good upgrade path. A new VAB might be a relatively small expense(comparatively:rolleyes:), but even with fairly loose pursestrings it pays to save what you can.

I was thinking, when you made Carter the champion of the revitalized program in the 1976 campaign, that you might not be on the same "Carter was an incompetent space-hating peanut farmer!" bandwagon that has been so popular since 1980, never mind Reagan's faults and failings. That you recalled that Carter had after all served as an engineering officer aboard USN nuclear-powered submarines and was not the dumb and Luddite hick his political enemies in the day and ever after liked to paint him as being. But then it turns out the Carter Administration is responsible for a slovenly rush job with the Novas...:(:rolleyes:

He answered this pretty well himself, but it may not be fair to call it a, "slovenly rush job," in any case. Sometimes, no matter how much time and effort you put into careful development of a space launch system, some complexity can always pass undetected. On the other hand, I'm sure some political opponents would be quick to place blame, but politics isn't always the art of fairness...
 
Top