# Designing a Space Elevator

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1. Mar 31, 2015

### Mk

Hi PF,
I've been tasked with joining a team in Budapest to design an endogenously powered space elevator.
I was wondering if I could talk about some concepts with you while I prepare for the 1 month camp.
http://copernicus.exosphe.re/

Right now I'm wondering if there is a way I can generate a strength curve for materials created over time. For example, is there any chance that the time that kevlar was invented, and the time that nanotubes were invented fall around an exponential curve? The maximum speed of manmade vehicles did, and allowed scientists to predict when they would be able to leave the Earth. If that strength/time curve is not already available, what materials do you think are significant milestones in strength?

Second, I'm also trying to wrap my head around the physics of space elevators. So far it seems like if the tether is less than 25,000 km tall, it will want to fall to the Earth. But if it's longer than that and has a counterweight, if the tether was cut from its base on earth, it would tend to rise up off the ground and float away into space.

Third, the task is to design an endogenously powered space elevator that coordinates with asteroid mining companies. If a payload is lowered down an elevator, how would we extract energy from that process?
1. The first thought I had was eddy currents. I remember seeing some neodymium magnets fall down a copper tube cooled by liquid nitrogen. That would be a way to slow its fall, but does it produce energy we can tap? Or just heat energy?
2. Induction: perhaps this is a more ordered form of the same eddy currents. Right? I remember passing a neodymium magnet through the inside of a loop of wire and detecting a current.
3. A friend of mine who works on radio towers says that when air blows against the radio tower, it generates a static electricity potential high enough that it can destroy the equipment on the radio tower and protective measures have to be put in place. Is there a way to capitalize off of this "problem?"
4. There are intriguing magnetic and electric phenomena in the region between the lower atmosphere and outer space.
I'll post back with more thoughts later.

Last edited: Mar 31, 2015
2. Mar 31, 2015

### Zuri Rohm

Is this elevator going to be used in a space station or space shuttle?

3. Mar 31, 2015

### Mk

The elevator is a tether, likely of unspooled carbon nanoribbons connecting sea level Earth with a satellite or counterweight floating in geosynchronous orbit. Flying vehicles or space stations could dock to its port in space. Check the first link in my first post for more information.

4. Mar 31, 2015

### Mk

5. How would you store the energy gained from the fall of a payload? On what order would that energy be? Would graphene supercapacitors be appropriate? If it is large enough, could we just push the electricity directly into the grid, or use the activation energy as a catalyst for extremely high energy chemical reactions, or nuclear fusion reactors? What type of structure would be necessary in order to pull something up a second space elevator (or the same one even), simultaneously?

Some people I talked to suggested beaming power to a solar panel would be easiest. That has a 0.5% efficiency with today's technology, according to Wikipedia.

Perhaps boats could dock near the base of the elevator in order to charge their supercapacitors.

5. Mar 31, 2015

### Mk

I went and checked since you said that. Turns out I think I read it on a different site!

But this Wikipedia article on space-based solar power made me realize its more complex than that. The density of the atmosphere is always changing with altitude and weather.
https://en.wikipedia.org/wiki/Space-based_solar_power

This source also says (with a citation):
"Between 1969 and 1975, Bill Brown was technical director of a JPL Raytheon program that beamed 30 kW of power over a distance of 1-mile (1.6 km) at 84% efficiency."

6. Apr 1, 2015

### Bandersnatch

Here's a feasibility study of one particular design of the space elevator that you might find useful:
http://www.mill-creek-systems.com/HighLift/contents.html
http://www.mill-creek-systems.com/HighLift/

It goes over material requirements and proposes some climber designs and power transfer.
There isn't all that much about the physics there, but even what is there should help, as you appear to have some misconceptions. E.g. you need a much longer cable than 25Mm (maybe you meant miles?) - basically you need to have its neutral point at the radius of the geostationary orbit. Any length of the cable further out will pull the cable outwards, anything closer will pull it inwards.

7. Apr 2, 2015

8. Apr 2, 2015