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Need opinions and guidance building a space elevator.

#642
Okay. Maybe my understanding of a space elevator is incorrect. I assumed they would be made of something like cement and steel or carbon fiber or titanium.

A cylinder that was 3 meters in radius and 20,000 km long would have a volume of 565,000,000 m^3. The density of cement is 3,150,000 g/m^3 and carbon fiber is around 2,000,000 g/m^3. That means the simple cylinder I am designing has a mass of 1,130,000,000,000 kg (1,200,000,000 tons) if it was made entirely out of carbon fiber.

A cylinder with that volume weighing 20 tons would have a density of 0.0000000354 g/m^3. Hydrogen at standard pressure has a density of 90 g/m^3. So what are these elevators made of? Pure energy?

Note, I use a simple cylinder to make the math easiest, but you could make this a tube with a 9 meter radius pipe with a thickness of the wall of 0.5 meters and it works about the same.

Regarding the velocity, I just used the terminal velocity of a sky diver to come up with 250 miles per hour (plus it works out close enough to 100 m/s). The energy lost to friction in the atmosphere surely retards the velocity (reducing the energy that would hit earth), but it will just stop the velocity from accelerating past the terminal velocity. The structure wouldn't really be going fast enough ever to vaporize like a meteor entering the atmosphere.

Also, regarding the distribution of energy, it would be like 53,000,000 kg falling every km 21000 times. That is around half the circumference of Earth. Going back to the terminal velocity of around 100 m/s, that is 265,000,000,000 J or 63 tons of TNT every km. Or 2.5 megatons of TNT across the world. And that is just for a big piece of pencil graphite.

I do admit I think I forgot to convert the g to kg in my prior post, but that was back of napkin math with little real thought or checking.
 
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#643
James Collins said:
Okay. Maybe my understanding of a space elevator is incorrect. I assumed they would be made of something like cement and steel or carbon fiber or titanium.

A cylinder that was 3 meters in radius and 20,000 km long would have a volume of 565,000,000 m^3. The density of cement is 3,150,000 g/m^3 and carbon fiber is around 2,000,000 g/m^3. That means the simple cylinder I am designing has a mass of 1,130,000,000,000 kg (1,200,000,000 tons) if it was made entirely out of carbon fiber.

A cylinder with that volume weighing 20 tons would have a density of 0.0000000354 g/m^3. Hydrogen at standard pressure has a density of 90 g/m^3. So what are these elevators made of? Pure energy?

Note, I use a simple cylinder to make the math easiest, but you could make this a tube with a 9 meter radius pipe with a thickness of the wall of 0.5 meters and it works about the same.

Regarding the velocity, I just used the terminal velocity of a sky diver to come up with 250 miles per hour (plus it works out close enough to 100 m/s). The energy lost to friction in the atmosphere surely retards the velocity (reducing the energy that would hit earth), but it will just stop the velocity from accelerating past the terminal velocity. The structure wouldn't really be going fast enough ever to vaporize like a meteor entering the atmosphere.

Also, regarding the distribution of energy, it would be like 53,000,000 kg falling every km 21000 times. That is around half the circumference of Earth. Going back to the terminal velocity of around 100 m/s, that is 265,000,000,000 J or 63 tons of TNT every km. Or 2.5 megatons of TNT across the world. And that is just for a big piece of pencil graphite.

I do admit I think I forgot to convert the g to kg in my prior post, but that was back of napkin math with little real thought or checking.
Click to expand...
I think that it would be triangular...:whistle:
 
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#644
James Collins said:
Okay. Maybe my understanding of a space elevator is incorrect. I assumed they would be made of something like cement and steel or carbon fiber or titanium.

A cylinder that was 3 meters in radius and 20,000 km long would have a volume of 565,000,000 m^3. The density of cement is 3,150,000 g/m^3 and carbon fiber is around 2,000,000 g/m^3. That means the simple cylinder I am designing has a mass of 1,130,000,000,000 kg (1,200,000,000 tons) if it was made entirely out of carbon fiber.

A cylinder with that volume weighing 20 tons would have a density of 0.0000000354 g/m^3. Hydrogen at standard pressure has a density of 90 g/m^3. So what are these elevators made of? Pure energy?

Note, I use a simple cylinder to make the math easiest, but you could make this a tube with a 9 meter radius pipe with a thickness of the wall of 0.5 meters and it works about the same.

Regarding the velocity, I just used the terminal velocity of a sky diver to come up with 250 miles per hour (plus it works out close enough to 100 m/s). The energy lost to friction in the atmosphere surely retards the velocity (reducing the energy that would hit earth), but it will just stop the velocity from accelerating past the terminal velocity. The structure wouldn't really be going fast enough ever to vaporize like a meteor entering the atmosphere.

Also, regarding the distribution of energy, it would be like 53,000,000 kg falling every km 21000 times. That is around half the circumference of Earth. Going back to the terminal velocity of around 100 m/s, that is 265,000,000,000 J or 63 tons of TNT every km. Or 2.5 megatons of TNT across the world. And that is just for a big piece of pencil graphite.

I do admit I think I forgot to convert the g to kg in my prior post, but that was back of napkin math with little real thought or checking.
Click to expand...
You got the first bit right.
 
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#653
It's a neat idea. We'll do it eventually, but not here until we develop very strong materials that currently exist only in theory. But you could do it now, in lower gravity situations such as our moon. Kevlar would do, there. But in a 'high' gravity environment such as Earth's the stress is too great for today's known substances.
 
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#654
and we need a space elevator .....because ? I thought Elon Musk was working out this whole re useable rocket stuff. You could get a lot of re useable rocket for the price of one space elevator. Besides rockets can dodge space junk more easily too........ya know, so theres that
 
#656
bluesblaster said:
and we need a space elevator .....because ? I thought Elon Musk was working out this whole re useable rocket stuff. You could get a lot of re useable rocket for the price of one space elevator. Besides rockets can dodge space junk more easily too........ya know, so theres that
Click to expand...
Elon is brilliant. The elevator is in the future, when space junk and rockets are things we read about in history books. Maybe another thousand years? But it'll happen.
 
#657
I think there will just be more space junk personally. The land and the sea will be full of all our disposable non bio degradable crap, the only place left to go is up. Space, the final frontier in waste management.
 

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