5 ms·

Even if we built a space elevator, imagine that the payload travels up at 100km/h - really fast, basically a car on a highway. Even in that ludicrous mode, it

• ben_w 7y ago
  100 km/h is not particularly fast, not even for a highway (my German friends recently discussed their preferred Autobahn speeds, and that varied from 110 to 190 km/h). A 747 cruises at 893 km/h. Concorde cruised at 2140 km/h. The ISS orbital speed is 27580 km/h — or 36 megameters in 1 hour 18 minutes.
  • 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.
• aruggirello 7y ago
  You've got it... upside down. The line is dangling from the Moon, down to ~36000Km above us. That car would have to reach geostationary orbit, jump on that tiny cable, then travel... oops, the remaining ~350,000Km to reach the Moon. To do that trip in 15 days, it'd have to run at mach 1.0. Edit: it gets even weirder, if you consider the Moon's distance from Earth goes from 363,300Km at perigee to 405,500Km at apogee... just how long should the line be? If it's 327,300Km, we might only be able to operate it near perigee, sure if it's a bit longer it'd be more usable, but it cannot extend past 363,300Km - or it would touch down here :) - that means there's no way we might use it near apogee, since it would always be too far away.
  • Tepix 7y ago
    > That car would have to reach geostationary orbit No, it would not have to reach orbit, it would have to reach the altitude but not the horizontal speed. Huge difference.
• Pfhreak 7y ago
  People still take ocean liners across the Atlantic. Those trips vary in length, but are at least a week long. If you told me I had to hang out in a cramped hotel for two weeks, but after that I would be on the moon, I'd sign up in a heartbeat.
  • papito 7y ago
    An ocean liner is basically a party on the ocean. This is essentially doing a month-long sentence in a cell at ADX Florence supermax - with no yard time.
    • Pfhreak 7y ago
      Except... I can bring my Nintendo Switch, a pile of podcasts, maybe a book or two, some movies, maybe a laptop? I might not be super comfortable the whole time, but knowing that the moon was only days away would get me through it just fine.
    • Tepix 7y ago
      The view will be unlike any other.