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While space elevators make for a fun toy gedanken for space enthusiasts who don't have an engineering background, they will never happen for one primary reason:

While space elevators make for a fun toy gedanken for space enthusiasts who don't have an engineering background, they will never happen for one primary reason: As soon as you have a material out of which you can build a space elevator, you have a material to make extremely lightweight filament-wound pressure vessels. You essentially get SSTOs with amazing payload fractions and greatly reduced mechanical complexity for free. LH2 gives you tanks that are too heavy for an aluminum craft? No problem. Elevator-grade carbon nanotube composites are 1/1000th the mass. Go nuts. When vehicle mass fractions go from 10% down to .1%, payload mass fractions go from 2% to 12%, minus trace amounts of structure. Was it Asimov who said that space elevators will happen 50 years after people stop laughing? I hope so, because people should never stop laughing at this idea. (Really? We're going to better utilize space--i.e., cramming NEO with nanosats--at the same time we erect a huge hazard in NEO? Come on!)

Florin_Andrei 13y ago
Devil's advocate: Rockets are still less safe. Rockets still produce tremendous accelerations. 12% payload fraction is still much less than 50%, or 90%.
- theothermkn 13y ago
  QED. Your first sentence shows no consideration at all of the effect of material advances on launch vehicle safety. Your use of the phrase "tremendous accelerations" shows no understanding of the accelerations actually produced even by current launch vehicles. Also, you don't mention why this is, or even ever has been, a limiting factor in designing a payload, nor the degree to which it impacts payload design. Noting that 50 or 90 is greater than 12 doesn't change the fact that we're in an entirely different design space from the 2%-mass-fraction vehicle. Like I said, space elevators are a fun little toy gedanken for people who just want to think about The Amazing Future. If this is the best the Devil's Advocate can do, the Saints are going to be just fine.

Florin_Andrei 13y ago

Devil's advocate: Rockets are still less safe. Rockets still produce tremendous accelerations. 12% payload fraction is still much less than 50%, or 90%.

theothermkn 13y ago
QED. Your first sentence shows no consideration at all of the effect of material advances on launch vehicle safety. Your use of the phrase "tremendous accelerations" shows no understanding of the accelerations actually produced even by current launch vehicles. Also, you don't mention why this is, or even ever has been, a limiting factor in designing a payload, nor the degree to which it impacts payload design. Noting that 50 or 90 is greater than 12 doesn't change the fact that we're in an entirely different design space from the 2%-mass-fraction vehicle. Like I said, space elevators are a fun little toy gedanken for people who just want to think about The Amazing Future. If this is the best the Devil's Advocate can do, the Saints are going to be just fine.