If you were to launch a rocketship parallel to the earth, on wheels, how big would the ramp have to be to get it into space?

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• makeshiftreaper@lemmy.world ⁨20⁩ ⁨hours⁩ ago

  So for physics reasons it doesn’t really matter what technique you’re using to leave Earth. If you’re going to try to go to space successfully, you’re going to have to go a minimum speed of 25,000 miles per hour. That’s called the escape velocity and it’s a different value for every body of mass in space

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  • glimse@lemmy.world ⁨19⁩ ⁨hours⁩ ago

    Yeah but like what if the ramp went past the exosphere? Drive that rocketship up at 1mph for 100 days and you’ll be in space!

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    • FuglyDuck@lemmy.world ⁨19⁩ ⁨hours⁩ ago

      the longer you spend at sub orbital speeds, the longer you’re spending energy to counter gravity. Building a ramp and lifting it up slowly would only be feasible if you had cheap power to do it. but over all, you’re still using most the same amount of energy to get there anyways.

      also… if you’re going to slow, you’ll just fall back down…

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    • makeshiftreaper@lemmy.world ⁨19⁩ ⁨hours⁩ ago

      Some more physics things, every planet has a limit on how high the tallest possible mountain is based off their surface gravity, the type of rocks present in the crust, and thickness of the crust. On Earth it turns out that limit is pretty close to Mt Everest’s height. Space is still about 50 miles above Everest so I don’t think humans could build this ramp with our current understanding of physics

      If you want to go to space slowly then you can just do what Felix Baumgartner did and take a special type of balloon to get into space. Unfortunately, if you’re not traveling 25,000 mph relative to the surface of the planet, you’re going to fall back to the planet. Just like Felix did

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• FuglyDuck@lemmy.world ⁨19⁩ ⁨hours⁩ ago

  So… define you’re gonna have to define what 'into space" means. 160km is the bare minimum for LEO (its still low enough it’ll degrade, but not so low that you can’t make a full orbit.) the ISS is still in LEO, and still requires some occasional burns to lift it back into orbit at 400km. To get above the atomosphere so you can (mostly) float endlessly inspace, you’d need to go to 1,000km

  Pick one. that’s how high you need to be.

  If you want to just technically reach orbital speeds… you could do that at sea level by going about 7.9 km/s. there’s a small problem of air resistance causing you to burn up and, if you somehow survive that, well, here’s mountains to go splat into.

  If yo wanted to orbit at 160km’s amid musk’s space junk… that’s about 7.8km/s, 400 is about 7.67, and 1000 is about 7.35.

  There are some systems that may or may not be viable in the future that don’t rely on rockets at all, for example, the launch loop which is basically a cable held up by making it rotate really fast. (yeah. talk about whacky.) This thing, as propose, is 60km high and several thousand km long. The idea is that you lift up a mag train and then that mag train accelerates at a comfy 3g. You then use relatively inexpensive kicker motors to circularize your orbit as you reach apoapsis (aka, the point of an orbit that is furthest away from the body you’re orbiting.) This raises (or lowers, depending on which way you’re pointed,) periapsis, which is the closest point.

  The thing about ramps, though, is that if your rocket car is already accelerating at 3 or whatever g (most modern launches push 3-4g, mostly limited by the squishy payload.)… you don’t really need a ramp, and trying to use one anyhow just introduces more inefficiency into the system.

  The point of the launch loop is that it gets us off dumping shit loads of CO2 and other greenhouse gasses- it can be powered by nearly any kind of power (though nuclear is the proposed plant,) and the train is accelerated by riding eddy currents off the loop itself.

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• dwindling7373@feddit.it ⁨20⁩ ⁨hours⁩ ago

  If fast enough you need no ramp. It just takes off thanks to the curvature of the earth.

  It just leaves “sideways”.

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• Thorry84@feddit.nl ⁨19⁩ ⁨hours⁩ ago

  There is a few different concepts here in conflict, which is why the question is hard to answer.

  What do we mean when we say space? Usually we mean above the Kármán line, or above 100km. At that point you are above almost all of the atmosphere, so we consider that space. The atmosphere does actually extend quite a bit above that, but at that point it’s so thin we consider it to be space.

  However as we know, the Earth has a bunch of gravity from its mass. So when you get up to 100km you just fall back down. Space isn’t free of gravity, the gravity of the Earth extends basically for ever. It’s influence does get less (thanks to Newton we know by how much), but considering the Earth is thousands of km wide when we get up to 100km we are basically still on the ground as far as gravity is concerned.

  So why do we see astronauts fly around? They are weightless, so there is no gravity right? This is something popular media gets wrong a whole bunch, it’s not like there is some magically line called space and beyond there you are weightless. Those astronauts are actually in orbit, that’s why they don’t experience gravity from the Earth. To understand orbits, imagine we fire a big ass cannon. The ball flies through the air in an arc and lands on the ground. How far away it lands, depends on how fast we shot the ball. The faster it went out of the cannon, the further it flies. Now imagine we shoot the ball over the horizon, so it lands so far away we can’t even see it anymore. It still lands right? Yes, but only up to a point. It turns out if you shoot the ball fast enough, the arc just continues falling beyond the horizon until it loops around the Earth. As it is falling, it doesn’t experience gravity except for the arc it follows.

  Usually when we put stuff into space, we mean put it in orbit and especially something called Low Earth Orbit . That means it needs to have a speed just like the cannon ball, to keep falling indefinitely. The speed we need is depended on how large the arc we want to have, or in other words how high the orbit is above the Earth. For context, if we want to fly in orbit in space so at an altitude of 100km, we would need to go almost 28254 km/h. Imagine driving that fast on the highway, it’s crazy fast.

  That’s why we use rockets, it’s not as much about going up, it’s more about going really fast. So a rocket takes off and goes vertical for the first bit, this is to get to a thinner part of the atmosphere to reduce drag. Then it does something called the pitch over maneuver, usually in the form of a gravity turn. This is to go mostly horizontal and get that speed up. At the speeds rockets are going, they get to the 100km altitude in no time. So they pitch over as to not overshoot and use all their energy to go as fast as they can horizontally and thus into orbit. Then you get into the realm of orbital mechanics, which popular media also gets wrong a whole bunch. You can’t just point you spacecraft into space, give it a boost and be flying off into the void forever. If you want to learn more I would recommend playing Kerbal Space Program, to get a feel for how orbits work.

  But say we are totally done with Earth and just want to leave it all behind, go into Deep Space. How would we do that? For that we need even more speed, something called escape velocity. If we get to that speed (40270 km/h), we can leave the Earth and go wherever we want, right? No not just yet, we might have left Earth behind, but we are still in orbit around the Sun. So we are still following orbital mechanics, only the Sun is the primary body we have to account for instead of the Earth. So we can use orbital mechanics to fly around the solar system.

  If we want to leave the solar system, we would need to go even faster. But the issue is there is nothing out there. To get anywhere interesting, we would need to travel close to the speed of light for years. Even our fastest spacecraft are standing still compared to the speed of light, so leaving the solar system isn’t very useful right now. But we do have the Voyager space probes which kinda sorta left the solar system and we got some interesting data from them, which is cool!

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  • Consumer2747@lemmy.world ⁨19⁩ ⁨hours⁩ ago

    This seems like a very well-informed post, was definitely full of useful, accessible information, well linked, and well written. I actually learned something (the sideways thing)! Thank you!

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    • Thorry84@feddit.nl ⁨18⁩ ⁨hours⁩ ago

      You are very welcome! <3

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  • litchralee@sh.itjust.works ⁨14⁩ ⁨hours⁩ ago

    You can’t just point your spacecraft into space, give it a boost and be flying off into the void forever.

    To be clear, is the reason this is not sufficient for flying forever is due to orbital mechanics making “point and shoot” not feasible if aiming for the void? Or because the boost isn’t sufficient to escape the planetary system’s influence and thus still predominantly subject to its gravitation pull? Or both?

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    • Thorry84@feddit.nl ⁨14⁩ ⁨hours⁩ ago

      Yes

      As long as the object doesn’t reach escape velocity, it’s in orbit and thus bound by the primary object. Now this orbit can by very weird and huge, but it’s still a loop. Only above escape velocity does the loop “break” and leaving the object without a guaranteed return is possible.

      So in theory if an object is in orbit and the boost is sufficient, it can just leave. However even then it is subject to the gravity fields and will make an arc instead of just a straight line. So “point and shoot” is never really an option. But often in movies a small spacecraft is seen making a small maneuver and somehow being seen as lost to space. That will for certain not be the case, a small boost just gives you a different orbit, but an orbit still.

      For example the movie Life (2017) comes to mind. Spoiler alert. In the end they decide to use an escape pod to launch into “deep space” with the alien. The escape pod just points up and fires the rocket for a short while and now is lost to deep space forever. This is total nonsense. The reason escape pods can work with very little fuel is they often have just enough oompf (or delta-V if you want to be technical) to put the pod into a slightly lower orbit. This lower orbit means more drag from the atmosphere which slows it down further, lowering the orbit again etc. until the thing is slowed enough it can totally re-enter and land. It isn’t like an escape pod pointed down goes to Earth and pointed up goes into outer space. The pod actually fires in the direction of the orbit, so horizontally, in order to slow it down.

      Orbital mechanics get really weird really fast. For example slowing down can cause the orbit to become higher before it goes lower. And putting in energy sideways can alter the angle of the orbit just like those spinning flywheel desk toys. Playing around with orbits in Kerbal Space Program can give a better understanding and can even make the concept of delta-V very easy to understand. KSP players would be unable to watch the movie Gravity (2013) for example without screaming at the screen: “THIS IS NOT HOW ANY OF THIS WORKS”.

      It’s hard to figure out, that’s why we refer to hard things as “rocket science”. It’s not just the complexity of the rocket as a machine and engineering challenge. But also figuring out stuff like orbits, taking into account the different gravity fields of objects that are of note. Doing things like gravity assists or Hohmann transfer orbit, taking into account the influence the extremely thin atmosphere has. And remembering everything moves, so shoot for where the target is going to be, not where it is now.

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• Olgratin_Magmatoe@slrpnk.net ⁨16⁩ ⁨hours⁩ ago

  If you’re going fast enough for a ramp to send you into space, you’re already going sufficiently fast to have a set of wings to carry you the majority of the altitude you need to achieve. And at that point, you’re trying to make a SSTO space plane. But those aren’t currently viable with existing technology due to inefficiencies in current rocket designs.

  Earth is big, with a very deep gravity well. It’s not well suited for fully self powered space planes.

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• Winthrowe@lemmy.ca ⁨21⁩ ⁨hours⁩ ago

  How fast do your wheels go? Being in space is more about going sideways fast than being high up. Orbital mechanics are weird.

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• cosmicrookie@lemmy.world ⁨20⁩ ⁨hours⁩ ago

  When you say parallel, do you mean vertically? Because parallel would require the earth to be flat

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  • TheBat@lemmy.world ⁨20⁩ ⁨hours⁩ ago

    OP means take off, like a plane.

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