We've had plenty of threads and TLs about super-fast fighters and bombers. I'm working on something that involves a different aspect of airplanes: their size. My question for you is, given economic incentives to make bigger airplanes, just how big can they plausibly get?
Here's what I have in mind. The TL includes a successful Aircraft Nuclear Propulsion program, with the first military combat aircraft (a bomber) flying in the early 60s, and the first non-combat aircraft flying in the 70s. For reasons not worth getting into right now, the public is okay with this, and oil price spikes and mass produced reactors mean that atomic propulsion is economically competitive with conventional propulsion by the mid to late 70s for large aircraft over long-haul routes. (I'm still not 100% sure that I can make the economics work out, but I think I can, and let's just assume it does for the moment.)
Now, one of the interesting properties of atomic propulsion is that efficiency increases markedly as aircraft size increases. The T/W of an atomic engine is dominated by the shield, which is very roughly proportional to the surface area of the reactor, so a bigger plane means less of the plane is engine. In fact, there's a breakeven point somewhere between one and four million pounds gross weight, depending on assumptions, where the T/W of an atomic engine for a large airplane on a long-range mission is better than that of a conventional engine, if you count the fuel as part of the engine.
So this creates a strong incentive for airplanes to get BIG. NASA did a few paper studies that went up to 20,000,000 lbs. gross weight, and which had enough cargo capacity to airdrop a Saturn-V. Also, I should mention that this TL features a technocratic political movement who just LOVE enormous public works programs, like super-sizing airports to Meet the Challenge of Tomorrow (TM). In many cases local concerns may prevent them from expanding as much as they want, but quite a bit of funding would be available for states or municipalities to build longer and wider airstrips.
So, how big can planes get? Can they actually reach 20,000,000 lbs.? Even bigger?
Here's what I have in mind. The TL includes a successful Aircraft Nuclear Propulsion program, with the first military combat aircraft (a bomber) flying in the early 60s, and the first non-combat aircraft flying in the 70s. For reasons not worth getting into right now, the public is okay with this, and oil price spikes and mass produced reactors mean that atomic propulsion is economically competitive with conventional propulsion by the mid to late 70s for large aircraft over long-haul routes. (I'm still not 100% sure that I can make the economics work out, but I think I can, and let's just assume it does for the moment.)
Now, one of the interesting properties of atomic propulsion is that efficiency increases markedly as aircraft size increases. The T/W of an atomic engine is dominated by the shield, which is very roughly proportional to the surface area of the reactor, so a bigger plane means less of the plane is engine. In fact, there's a breakeven point somewhere between one and four million pounds gross weight, depending on assumptions, where the T/W of an atomic engine for a large airplane on a long-range mission is better than that of a conventional engine, if you count the fuel as part of the engine.
So this creates a strong incentive for airplanes to get BIG. NASA did a few paper studies that went up to 20,000,000 lbs. gross weight, and which had enough cargo capacity to airdrop a Saturn-V. Also, I should mention that this TL features a technocratic political movement who just LOVE enormous public works programs, like super-sizing airports to Meet the Challenge of Tomorrow (TM). In many cases local concerns may prevent them from expanding as much as they want, but quite a bit of funding would be available for states or municipalities to build longer and wider airstrips.
So, how big can planes get? Can they actually reach 20,000,000 lbs.? Even bigger?
