/sci/ - Science & Math

>>8070143
made a mistake here, cable should be around 100,000 km long

>>8070183
>>Lifting stuff up on a space elevator would cost more energy than sending stuff up on a reusable rocket.
however, electrical energy tends to be cheaper than fuel

>>So space elevator plans these days tend to talk about things like microwave power transmission, which is very lossy.
That is correct. Although one would more likely use a laser as the spot size will be smaller.

Now let's talk about where the 'for free' part comes in, above geostationary orbit the apparent gravitational force on a space elevator goes up. As long as you can overcome friction on the cable altitude keeps increasing and once you reach ~53,000 km, you are at escape velocity. Simply letting go of the cable at this point results in an escape trajectory.

It isn't actually 'free', but it does demonstrate an entertaining point about how space elevators steal angular momentum from Earth's rotation.

Yes, space elevators take a long time to get stuff into orbit(months), but then again so do other forms of transportation such as container ships.

>>Show me the bridge with the 35,790 km long span.
the amount of mass we would need to make a space elevator is less than the mass of the golden gate bridge. The Golden Gate Bridge masses 3.808 *10^8 kg. A 100,000 km space elevator was predicted from the study below to use 97.7*10^3 kg of cable and 52.7*10^3 kg of counterweight.

http://pichak-asanbar.ir/wp-content/uploads/2013/10/PKASpace-Elevators.pdf

>>8070311
>>8070236
Making a cable that can support the required tension force will certainly be a challenge

However, all of this is beside the point: space elevators are less of a fantasy than the singularity. For a space, we have a pretty good idea of what the technical challenges are. For artificial general intelligence, we have no clue what the challenges are.

>>6056619
>>hold it's own weight
the problem with space elevators isn't building a cable that can hold it's own weight, it's building a cable strong enough to hold onto a counterweight above geostationary orbit. A space elevator is in tension, not compression.

>>6057369
>>6057436

Because in order for the counterweight to support any weight, it must be above geostationary orbit, so it is spinning faster than the earth and centrifugal force will attempt to pull it away from earth.

>>6056623
The problem with lofstrom loops is one needs gigawatts of power to keep the thing from falling down, all the time.

>>6056201
Surprisingly yes, material requirements are actually more for a 370 km space tower than a space elevator. 35800 km is about as long as all the cables in the golden gate bridge