• milkisklim@lemmy.world
    link
    fedilink
    arrow-up
    29
    ·
    2日前

    In 5e yes. I think the theory is once you hit terminal velocity, you aren’t going to get any more damage from a longer fall.

    Fun fact, I actually did have a villain do exactly that in a campaign once. The party achieved a secondary win condition during combat and so the BBEG jumped off the top of the space elevator to escape.

    • turdas@suppo.fi
      link
      fedilink
      arrow-up
      7
      ·
      edit-2
      24時間前

      Wouldn’t jumping off the top of a space elevator just put you in orbit? Or, if by top you mean the point where the space elevator anchors to its counterweight, in orbit around the sun.

      • Cethin@lemmy.zip
        link
        fedilink
        English
        arrow-up
        3
        arrow-down
        1
        ·
        edit-2
        15時間前

        OK, you’ve got space elevators wrong, and that’s OK.

        The counter-weight doesn’t orbit the sun. It orbits earth. If it orbited the sun it’d rip the thing apart. It sits somewhere above a geostationary orbit, as a geostationary orbit is where the orbit point is always over the same point on the ground, which would be where your elevator is tethered.

        The station part is somewhere below this. The higher it is the heavier or further out your counter-weight needs to be —and since it’s already impossible around earth no matter what, this needs to be as low as possible.

        Because of this setup, your velocity (while below the geostationary line) is always less than the orbital velocity at that altitude. For example, the ISS orbits the earth 15.5 times a day. Our point on the space elevator cable stays at the exact same position over the ground, so it orbits 0 times. At the same altitude as the ISS you need to be moving the same speed as the ISS or you’ll fall down. It only doesn’t while attached to the cable because it’s being pulled by the counter-weight.

        Basically, stuff dropped off a space elevator falls, unless it’s at geostationary altitude. It needs to be given some extra horizontal speed to stay in orbit.

        • turdas@suppo.fi
          link
          fedilink
          arrow-up
          4
          ·
          edit-2
          11時間前

          The counterweight orbits above escape velocity, pulling the space elevator’s cable taut. If the cable were severed the counterweight would drift off into space into a solar orbit. So if you jump off at the counterweight, you’ll enter solar orbit.

          At geostationary orbit (which could be considered the “top” of the space elevator as that’s where you would normally get off, presumably) the space elevator orbits at exactly orbital velocity, so if you jump off there you end up in orbit. Below that your velocity would be below orbital velocity and you’d fall back to Earth.

          • Cethin@lemmy.zip
            link
            fedilink
            English
            arrow-up
            1
            arrow-down
            1
            ·
            8時間前

            Well, the “top” of the elevator could be anywhere. That’s why I said it needs to be as low as possible, because it’s already physically impossible for Earth. The lower and lighter the station is, the less impossible it is, though it’s impossible even with no station and just a cable.

            Above geostationary orbit isn’t suddenly in solar orbit though. It’s still got quite a ways to go. It could be at escape velocity, but that’s not necessary.

            This is all impossible on Earth anyway though, so if you’re making a story where this is taking place it could be any of these outcomes you want. Whatever works best for the story.

            • turdas@suppo.fi
              link
              fedilink
              arrow-up
              2
              ·
              6時間前

              It’s not “physically impossible” on Earth. The forces involved are great, sure, which means you can’t build it out of any present-day material like steel, but they’re not so great that constructing a space elevator would be physically impossible using non-exotic matter like it would be on, say, the Sun, or possibly even just Jupiter. We already know of materials that could be used to make a space elevator cable on Earth if they were available in sufficient quantities – namely carbon nanotubes.

              The “top” can’t be anywhere, because not everywhere along the length of the elevator will put released objects in orbit. Turns out on Earth, an object released off of the elevator would reach a stable (but very eccentric) orbit 2/3rds of the way to geostationary orbit – below that, it would fall back to Earth. Conversely escape velocity would be reached at about 53000 km, which is past geostationary orbit but much closer than where the counterweight would be (in most designs?). Objects above escape velocity will by definition escape Earth’s orbit, which most of the time means ending up in a solar orbit.

              • Cethin@lemmy.zip
                link
                fedilink
                English
                arrow-up
                1
                arrow-down
                1
                ·
                2時間前

                No, it’s physically impossible. Even the most advanced material possible couldn’t hold the strain that would be required for Earth. Technically it’s right on the limit, but that’s ignoring that we have an atmosphere that’s going to exert forces on it too. On Luna it might make sense.

                The top can be anywhere. It would just require adding force to it at/after release. That’s trivial. We already know how to make rockets, or it could be something that pushes or throws it. Compared to building a space elevator, speeding something up is easy.

                • turdas@suppo.fi
                  link
                  fedilink
                  arrow-up
                  1
                  ·
                  2時間前

                  No, it’s not physically impossible. For an explanation see my previous comment.

                  I find it funny that you started this conversation by telling me that I’ve “got space elevators wrong” and then proceeded to spout strange and verifiably false nonsense like this on multiple different points.