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All of 'em defeated with one line (lemmy.dbzer0.com)
submitted 1 year ago by to c/rpgmemes@ttrpg.network
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[–] 6 points 1 year ago* (10 children)

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.

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  • [–] 4 points 1 year ago* (9 children)

    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.

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  • [–] 4 points 1 year ago (8 children)

    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.

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  • [–] 1 point 1 year ago (7 children)

    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.

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  • [–] 2 points 1 year ago (6 children)

    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.

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  • [–] 1 point 1 year ago (5 children)

    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.

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  • [–] 2 points 1 year ago (4 children)

    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.

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  • [–] 1 point 1 year ago* (3 children)

    It's impossible. You didn't "explain" anything. It's on the very edge of being physically possible in a perfect vacuum. That's it. Consider how a hurricane effects a building. The building requires a ton of extra infrastructure/strength to keep it from breaking. Even the most exotic material possible it's still on the very edge of technically possible, that if you add any extra overhead to protect from the environment it isn't possible. Then there's also satellites and space trash which will be hitting the cable. It's not a thing that can work on Earth.

    then proceeded to spout strange and verifiably false nonsense like this on multiple different points.

    Sure... How do you deal with wind on a space elevator? I'm making strange and varifiably false nonsense? You're repeating pop-sci stuff as if it's real, without considering how it'd actually need to be to exist. We can barely build buildings that withstand storms. How is a thin cable going to? Carbon nanotubes are only good for tensile strength (resistance to tension). Shear strength is significantly lower, which is what would be required to withstand forces like weather or impacts. Even assuming it's possible to make the cable, it wouldn't work because of this.

    I don't care how many pop-sci articles or YouTube speculation videos have been made saying it's totally possible and just around the corner. They ignore the reality and only discuss the absolute minimum vacuum requirements. It makes a much more appealing article/video to say it's actually possible than to point out that, in reality, it isn't because there's a lot of additional things that were ignored.

    This video talks about some of the issues realistically, though it's mostly focused on math. It mostly is in the position of "if it were possible, why would we even want it" though, not is it actually possible: https://youtube.com/watch?v=Z5aHMB4Tje4&pp=ygUcYXJlIHNwYWNlIGVsZXZhdG9ycyBwb3NzaWJsZQ%3D%3D

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  • [–] 1 point 1 year ago (2 children)

    Space elevators aren't "pop-sci". There's a plenty of real research that says that one is possible. That is not to say one is going to be built any time soon (though it's not as implausible within a century or two as one might think), but it is to say that one is not physically impossible; physics very clearly says that it's possible. Not "on the very edge of being physically possible". Possible, period. The margins are more than realistic.

    The people who did that research weren't idiots and did in fact account for everything you brought up rather than just assuming a perfect vacuum and spherical cows.

    Sure... How do you deal with wind on a space elevator?

    By maneuvering the base station to avoid high wind weather systems. Though the effect of wind on the cable would not actually be anywhere near as great as you make it out to be.

    We can barely build buildings that withstand storms.

    Oh, really? When's the last time a skyscraper fell due to wind?

    Then there's also satellites and space trash which will be hitting the cable. It's not a thing that can work on Earth.

    The cable can maneuver to avoid trash and satellites, and satellites can maneuver to avoid the cable. Shielding can be applied to protect it from micrometeoroid impacts.

    This video talks about some of the issues realistically, though it's mostly focused on math. It mostly is in the position of "if it were possible, why would we even want it" though, not is it actually possible:

    https://youtube.com/watch?v=Z5aHMB4Tje4&pp=ygUcYXJlIHNwYWNlIGVsZXZhdG9ycyBwb3NzaWJsZQ%3D%3D

    "Why would we even want it" is such a colossally idiotic question that it could only have been uttered by a regressive leftist who's so brain broken by their Elon Musk hateboner that they literally become the guy in the below image, and lo and behold that's exactly what I found by clicking open the video. "Uhhhh we don't need more satellites in space actually because uhhh we have problems down here right now? And uhh billionaire tourism le bad."

    I am so fucking sick of terminally status quo brained people like this who view everything through a lens of present-day American politics and are as a result completely unable to envision a better world.

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  • [–] 1 point 1 year ago (1 child)

    Lol. None of this had to do with Musk. I don't know why you brought him up. If anything, a space elevator is anti-Musk, as he owns a rocket company, but whatever.

    You can't just maneuver a space elevator. The entire way it works is it sits at one point. The amount of forces it'd put on the structure to maneuver it is insane, especially if it has to be in time to avoid a hurricane. It has to stay at the equator, so it can only move along that axis, and the speed would need to be insanely fast. Basically, the structure needs to be built to multiple times the minimum required if you're going to be moving it, without a stable base platform to have oscillation dampeners or whatever on.

    The cable can maneuver to avoid trash and satellites, and satellites can maneuver to avoid the cable. Shielding can be applied to protect it from micrometeoroid impacts.

    Trash can't be maneuvered. We don't even know where 100% of it is. You can't shield the cable. The weight of the cable is the entire issue why we need insane materials to build it. If you add shielding then you're adding to the weight, and therefor multiplying the size the cable needs to be. A cable made of steel literally needs to be larger than the size of the known universe because you need more weight to support more weight. It compounds. If you add shielding with a different material, you run into the same issue. The cable has to be very light so the compounding size doesn't grow to impossible levels.

    Space elevators aren't "pop-sci". There's a plenty of real research that says that one is possible...

    ... The people who did that research weren't idiots and did in fact account for everything you brought up rather than just assuming a perfect vacuum and spherical cows.

    I didn't say they're idiots. They know what they're talking about. Most of them are doing physics papers just showing how the calculations work out, not engineering. It isn't stupid to assume spherical cows if the shape doesn't matter to you. Physics is not engineering, just math.

    The people who opened companies "doing research" into it have all shut down. Either it was a scam or they realized it isn't possible. I'm leaning towards scam, because, like you said, I don't think they're stupid. They know other people are, and will give them money because it sounds cool and they don't know any better.

    The people doing materials science adjacent to this are not doing materials science to build a space elevator. They're just trying to come up with new useful materials. They may write a paper about how it could potentially be used in a space elevator, based purely on the math, because they looking for grant money, recognition, or a media attention for a product for investment purposes or to sell. They aren't stupid. It's just useful.

    Space elevator on the moon? Sure. That is somewhat reasonable, though still far out of our grasp. Space elevator on Earth? Not happening. We'll have fusion reactors and nearly unlimited energy well before we even have the ability to build the mathematically minimum version, without any safety margins or defence for the environment, or systems to deal with vibrations/perturbations.

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  • [–] 3 points 1 year ago*

    Lol. None of this had to do with Musk. I don't know why you brought him up.

    The woman in the video is the one who brought him up.

    You can't just maneuver a space elevator. The entire way it works is it sits at one point. The amount of forces it'd put on the structure to maneuver it is insane, especially if it has to be in time to avoid a hurricane. It has to stay at the equator

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

    In most designs the base station sits on a moving platform in the ocean. That way it can be moved around to avoid things like storms. This doesn't put much extra force at all on the cable, because the cable is very, very long, and as a consequence even a large movement at any given point is only a small change in terms of angles.

    The cable itself is also flexible, which means that even with a stationary base station it could be maneuvered to avoid collisions by pushing on it along its length.

    Trash can't be maneuvered. We don't even know where 100% of it is.

    By the time we'd actually be building a space elevator we would also undoubtedly be a lot more capable and motivated to track orbital debris along its path, and probably also able to clean it up.

    You can't shield the cable. The weight of the cable is the entire issue why we need insane materials to build it. If you add shielding then you're adding to the weight, and therefor multiplying the size the cable needs to be.

    Shielding can be very light and it would be in space, probably only along high-risk segments. In any case, it's mostly an implementation detail that may not actually be necessary anyway.

    The people who opened companies "doing research" into it have all shut down. Either it was a scam or they realized it isn't possible.

    This means absolutely nothing. Quarterly capitalism is incompatible with extremely long-term projects like space elevators, is this news to you? Nobody sane actually expects a space elevator to be built on a timescale that is of use to investors. Even if we had the requisite materials and technologies and the construction started right now, it would likely take decades to complete.

    The people doing materials science adjacent to this are not doing materials science to build a space elevator. They're just trying to come up with new useful materials.

    Exactly. Where did I claim otherwise? My point is that the research has been done to show that it's physically possible and what the approximate material requirements would be. Material science research has shown us that materials that can meet those requirements exist (carbon nanotubes, diamond nanothreads), but currently can't be produced at scale. Thankfully such materials would also be incredibly useful for a great many other purposes, so materials research labs can stay in business investigating how to manufacture them at scale, and at some point in the future once they can be manufactured at scale, they may be used for constructing a space elevator.

    Again, how is this unusual to you? This is how literally all technological development works. Theory will show that some technology is physically possible decades or even centuries before practice catches up and makes it practically possible, and after that manufacturing and economical realities may or may not make it practically feasible.

    One could argue that a space elevator will never be practically feasible because e.g. launching rockets will always be cheaper, or even that it'll never be practically possible because e.g. manufacturing the necessary quantities of advanced nanomaterials will forever be out of reach -- a much more tenuous argument than the first. But no, you've chosen the most tenuous argument of them all, that it is physically impossible -- something theory has already shown to be false.

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