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Space Elevator

neal.fun

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Re: Space Elevator

#31

Post by Sharlin »

philwelch wrote: post #14
davidhyde wrote: post #2

At 74km/h you would reach space (100km karman line) in an hour and a half but you would need to keep going for another 20 days at that speed reach geostationary orbit in order to not fall back to earth when you exit the space elevator.

Yeah, I wish this went on as far as an actual space elevator would, perhaps with extra visualizations of the heights of various orbits. The top would be slightly above geostationary orbit, since you would need the center of mass to be at the geostationary point in order to work.

Or more than slightly if you don't want to haul up a big counterweight but just use the cable itself as a counterweight. The Brad Edwards design proposes a total cable length of around 100,000 km. One very nice side effect of a long cable is that you can slingshot spacecraft from the far end up to ~Jupiter's orbit with zero propellant needed.

Re: Space Elevator

#32

Post by adlpz »

That was absolutely fantastic. I just left a pretty rough meeting and came to HN for some healthy procrastination.

Really made my day.

Re: Space Elevator

#33

Post by Sharlin »

mcv wrote: post #19
philwelch wrote: post #16

Earlier quoted context omitted.

Some of those celestial bodies are even small enough that we could build the elevators with existing materials, too.

A space elevator on Mars is probably totally feasible. But of course the benefits would be much larger on Earth. The problem is: the benefit of a space elevator is bigger the deeper your gravity well is, but it's also much harder to impossible to make one there. But I've also been wondering: wouldn't it be possible to have a tapering space elevator? Reduce the weight by making the parts that have to carry less weight…

Yes, it absolutely has to taper, with an exponential curve, to keep stress constant over the length of the cable. The taper ratio (in terms of cross-sectional area) for the best currently available engineering materials for an Earth space elevator would be in the tens to hundreds of millions, but a carbon nanotube cable might only require a taper ratio of around ten. (A steel cable would need a taper ratio on the order of 10^33.)

Re: Space Elevator

#35

Post by virtualritz »

This is great.

I just wish there was one way to switch all units. The temp. can be switched between F/C by tapping on it.

The height is metric and seems fixed and then stuff in text bubbles is again imperial (e.g. mph instead of kph).

Re: Space Elevator

#36

Post by Sharlin »

mcv wrote: post #20
rasengan wrote: post #3

I love this. Space elevators are going to be here much sooner than it seems with carbon nanotube tech. :)

Would be cool, but as far as I understand, even long, continuous carbon nanotubes wouldn't be strong enough to carry their own weight.

Not if the cable has constant cross-sectional area, but actual designs call for a cable with an exponential taper, and that would make a carbon nanotube cable feasible. With currently available engineering materials the taper ratio would be too large (~10^8 for Kevlar, ~10^33 for steel…)

Re: Space Elevator

#38

Post by Sharlin »

rasengan wrote: post #3

I love this. Space elevators are going to be here much sooner than it seems with carbon nanotube tech. :)

There's not been that much progress in the 20 years since Brad Edwards proposed the first actually feasible space elevator design. It's difficult to say whether ultra-strong CNT cables are something that's perpetually 20 years away, or something that follows the "progress is slow until it suddenly isn't slow" exponential curve.

Re: Space Elevator

#39

Post by aaron695 »

avmich wrote: post #5

I don't understand why so many seemingly educated people keep discussing Earth space elevator. For a long time there is a conclusion that the elevator is incompatible with Earth satellites, which mostly fly below GEO, and elevator will collide with satellites, with all negative consequences. The inherent elevator problem has nothing to do with the material of the cable. Am I missing something?

[dead]

Re: Space Elevator

#40

Post by blkhawk »

As cool as space elevators are - I wish all the other "easier" to build options would be more mainsteam. Say orbital hooks or maybe some of the more sedate active support structures like orbital rings or lauch loop variants.
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