4 ms·

We are talking about a thing attached to a cable and going up. How are those other speeds a reference?

by papito 7y ago

heavenlyblue 7y ago
I believe this is way more limited by acceleration.
ben_w 7y ago
I don’t understand why you think that’s a problem. The cars are limited by human reaction time, the aircraft are limited by air resistance, the ISS is a space station and all the constituent parts had to be brought up to that speed in the first place from the ground by rockets. The main advantage of the category that space elevators are a part of is that energy and reaction mass doesn’t need to be carried with you as when you use a rocket, which makes them much easier.
- Retric 7y ago
  Needing to apply force to a tiny strand at high speed is a difficult problem. So far even 40mph has been a major issue. https://en.m.wikipedia.org/wiki/Space_elevator_competitions https://en.m.wikipedia.org/wiki/Space_elevator_competitions Several of these winners achieved less than 5mph and this is near earth so without the issues of supplying power over thousands of miles.
  - ben_w 7y ago
    That is interesting, and also surprising.
nbadg 7y ago
Don't forget that for the vast majority of that trip the atmosphere is essentially negligible. A better comparison would be a vacuum tube train with a(n approximately) constant 1G handicap. From the perspective of the tether, any practical payload mass is negligible in comparison with the tether itself, and -- most likely -- it's under tension anyways, so pulling the payload against gravity would actually be releasing tension below it. Space elevators are particularly strange to think about because they combine the weirdness of orbital mechanics with some, but not all, of the intuitions we have about terrestrial behavior -- and then add in the complications of being a megastructure on top of it, which humans have basically zero experience building. They defy easy reasoning.
- ben_w 7y ago
  It’s even better than that: by 6000 km the inverse-square law will have reduced that to only 0.25 gee gravity drag :)
the8472 7y ago
Attaching to a very thin cable seems problematic, friction would wear on it at high speeds. I wonder whether a linear induction motor (also acting as contactless magnetic bearing) would be possible or fail due to the small surface area.

We are talking about a thing attached to a cable and going up. How are those other speeds a reference?

by papito 7y ago

We are talking about a thing attached to a cable and going up. How are those other speeds a reference?

heavenlyblue 7y ago

I believe this is way more limited by acceleration.

ben_w 7y ago

I don’t understand why you think that’s a problem. The cars are limited by human reaction time, the aircraft are limited by air resistance, the ISS is a space station and all the constituent parts had to be brought up to that speed in the first place from the ground by rockets. The main advantage of the category that space elevators are a part of is that energy and reaction mass doesn’t need to be carried with you as when you use a rocket, which makes them much easier.

Retric 7y ago
Needing to apply force to a tiny strand at high speed is a difficult problem. So far even 40mph has been a major issue. https://en.m.wikipedia.org/wiki/Space_elevator_competitions https://en.m.wikipedia.org/wiki/Space_elevator_competitions Several of these winners achieved less than 5mph and this is near earth so without the issues of supplying power over thousands of miles.
- ben_w 7y ago
  That is interesting, and also surprising.

nbadg 7y ago

Don't forget that for the vast majority of that trip the atmosphere is essentially negligible. A better comparison would be a vacuum tube train with a(n approximately) constant 1G handicap. From the perspective of the tether, any practical payload mass is negligible in comparison with the tether itself, and -- most likely -- it's under tension anyways, so pulling the payload against gravity would actually be releasing tension below it. Space elevators are particularly strange to think about because they combine the weirdness of orbital mechanics with some, but not all, of the intuitions we have about terrestrial behavior -- and then add in the complications of being a megastructure on top of it, which humans have basically zero experience building. They defy easy reasoning.

ben_w 7y ago
It’s even better than that: by 6000 km the inverse-square law will have reduced that to only 0.25 gee gravity drag :)

the8472 7y ago

Attaching to a very thin cable seems problematic, friction would wear on it at high speeds. I wonder whether a linear induction motor (also acting as contactless magnetic bearing) would be possible or fail due to the small surface area.