Obviously, many designers have done the hard work that concludes tall and narrow is more cost effective.
America has the best transportation system in the world. Roads, interstate highway system, railroads, more inland waterways than anyone else, airports, etc. However, for the widest loads, the inter-coastal waterways and larger river systems can only handle 10-12m in width.
Quote from: KelvinZero on 05/26/2017 03:31 amObviously, many designers have done the hard work that concludes tall and narrow is more cost effective.Not really. Narrow has lower drag, but higher bending loads and also not optimal for weight. The most optimal shape is a sphere, the most optimal cylinder is one with h = 2r - neither of those are good aerodynamically.I have vague memory that for rocketry, length of 7 diameters is close to optimal, but don't quote me on this.Rockets often becoming longer than optimal because of transportation limitations and because change in factory tooling (and doors, roof height etc) is very expensive.
Fineness ratio, the ratio of the length of a body to its maximum width. There's a quote from Von Braun somewhere that the fineness ratio for orbital rockets shouldn't exceed 10-1, but that was in an era where materials science and engineering were much more limited than they are today. Many rockets today exceed 14-1. The Falcon 9 is in excess of 19-1. There's no real "optimum" that I can find a solid source on, it really depends on the design requirements.
Quote from: whitelancer64 on 05/26/2017 03:50 pmFineness ratio, the ratio of the length of a body to its maximum width. There's a quote from Von Braun somewhere that the fineness ratio for orbital rockets shouldn't exceed 10-1, but that was in an era where materials science and engineering were much more limited than they are today. Many rockets today exceed 14-1. The Falcon 9 is in excess of 19-1. There's no real "optimum" that I can find a solid source on, it really depends on the design requirements.Yeah, the F9FT is skinny as hell.
.... Railroads only about 3.7m but length due to turns can be a problem, but did carry the shuttle solid boosters but separated into segments for turns.
Aerodynamic losses are greater if you're wider. So you want to go taller if you can, but for a large rocket you'll be limited by the amount of thrust that can be produced in a given diameter with sea level expansion. So for a certain average vehicle density, there's a limit to how tall a cylindrical rocket can be (at least the propellant filled portion).
Quote from: Robotbeat on 05/26/2017 11:03 pmAerodynamic losses are greater if you're wider. So you want to go taller if you can, but for a large rocket you'll be limited by the amount of thrust that can be produced in a given diameter with sea level expansion. So for a certain average vehicle density, there's a limit to how tall a cylindrical rocket can be (at least the propellant filled portion).That was my initial guess, but everyone else here has been saying it has more to do with the size of roman horse's rear ends :-)Can you guess any ballpark of what the loss is? Just roughly. (The shuttle shape IMO proves you can still get something to orbit.. but presumably you pay something for it)Even if someone could estimate the difference between a rocket with atmosphere and a rocket with no drag, I think that would give a fair indication. Doubling the width would probably be something like doubling that loss, whatever it is?
Here's a whole essay on drag loss, and how it varies with proportions (height and frontal area). Overall drag losses are small compared to gravity losses (typically 100 m/s as compared to 1500 m/s or so), so even doubling them will not be prohibitive.
Please no more intermediate ITS speculation until there's some actual evidence to support its existence. People are using each others speculation to bolster their own speculation, and it's turning into a big morass of alternative-fact for a lot of frequent posters around here. No. We're better than this.As for width, the shape of the nose and where the taper begins and ends is just as portentous as the width of the nose.