Wow, lots of activity! Let's see about all this...
Alright then, here's another one! Extrasolar planets!...So what do you have concerning this particular topic, even if the more relevant - read, more Earth-like - extrasolar planets were only really discovered in the latter half of the 2000's.
Unfortunately, there's not a ton to say about extrasolar planets, particularly in the 90s before the instruments get as good as they are today.They will be touched on, but probably in conjunction with other astronomy posts as opposed to something dedicated just to them--we simply lack the information IOTL and they will ITTL through most of part III to say much more specific than, "There are planets around other stars: confirmed."
By the way, the rough dates for Part III are 1989 (Bush's announcement of Constellation) to the first few years of the aughts--there's a couple things that slightly overlap the start of the new millennium.
Hey, I've just noticed a couple things.
1) The Multicore concept uses 60 percent more Ker-Lox per F-1A engine than the Saturn V used per its five F-1 engines. I guess this is per the author's philosophy that for launches from Earth, thrust beats ISP. I estimate a Multicore first stage unit is 30 meters tall whereas the Saturn V's first stage was just under 42, yet 5 Multicore elements hold a lot more kerlox than the whole Saturn V first stage despite the wider diameter.
In part, they use more propellant because they have a lot more thrust--about a 33% improvement. To make up for that, the first stage does have slightly more propellant per F-1A than the Saturn V had per basic F-1. If you normalize by that, the difference isn't as big:
Saturn V, S-IC: 2150 tons prop, 5xF-1, 38 MN vac
Multibody, S-IF/G: 504 tons prop, 1xF-1A, 9.19 MN vac
So the S-IC has about 56.5 kg of prop per Newton of thrust, while the Multibody core has about 54.8. Basically the same. As for heights, the Multibody has a few advantages over Saturn V. First, it's common bulkhead--unlike
Saturn V which has two separate tanks, the
upper bulkhead of the low tank on multibody is also the lower bulkhead of the upper tank. This lets the same tank volume be shorter. Also, as you'll note, the S-IC has a very long thrust structure (the tanks total only about 100 ft of the 135 ft length). Multibody's thrust structure is shorter. Finally, you underestimated the effect of clustering cores. A single core with the same cross-sectional area as Zubrin's 5-core cluster would have to be 14.7m in diameter, while one matching the tricore would have to be 11.4 m. Result? The stages can fit more propellant into dramatically shorter heights.
As for the VAB, the dimensions of the doors are as follows--and have been since the construction of the building. The doors form an inverted T-shape. The lower rectangle is 149 feet wide and 113 feet high (to allow the crawler to pass through, along with pad-level fittings up on top of the MLP), the rest is 76 feet wide and goes up another 352 feet for a total height of 465 feet. The image below shows how these doors fit several major potential "doorbusters," from Saturn V to Shuttle to Ares V and Saturn Multibody. Note that the Shuttle wings squeak through in the lower part of the "T," hence the doors didn't require alteration. What did require alteration were the doors into the VAB's central transfer aisle--those were widened 40 feet to fit the wings, and an additional area cut for the tail, which is what you're reading about in those sources. (
See this image).
2) On the other hand, looking at linear dimensions, grouping 4 Multicores around a fifth in the middle means that the width, getting it out the VAB door, is a bit over 14 meters; even allowing separation of the stages a bit still would have it well under 16, versus the Saturn V's 10 meters maximum diameter.
I think you've done your math wrong. A cluster like that has a maximum dimension the same as 3x the core (6.6m), thus the total Saturn H03 width is more like 20.5 meters (19.8 m of stages, plus a bit for spacing). This does, however, still clear even the 23m "narrow" part of the T.
And so, replicating and even surpassing a Saturn V's capability may indeed make more sense via 5 standard Multibody cores instead of consolidating them all into one 5-engine core. And yet it comes out of the VAB just fine with no door widening!
Basically, if you did want a Saturn V class using Multibody philosophy, it'd be better to go with a 5-core than a new larger core. Zubrin's right there.
