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I've always been interested in the other case: What advances in spaceflight would be made by a technologically similar civilization if they had much lower gravi

by scj 8y ago

I've always been interested in the other case: What advances in spaceflight would be made by a technologically similar civilization if they had much lower gravity?

pronoiac 8y ago
I read some musings by Warren Ellis [1] which brushed up against easier space travel, very briefly: "The Olympus Mons mountain on Mars is so tall and yet so gently sloped that, were you suited and supplied correctly, ascending it would allow you to walk most of the way to space. Mars has a big, puffy atmosphere, taller than ours, but there’s barely anything to it at that level. 30 Pascals of pressure, which is what we get in an industrial vacuum furnace here on Earth. You may as well be in space. Imagine that. Imagine a world where you could quite literally walk to space." It's mostly not about your question, but I liked this part. [1] http://www.warrenellis.com/?p=14314 http://www.warrenellis.com/?p=14314
- LeifCarrotson 8y ago
  Walking to the altitude of space and standing on something is very, very different than accelerating to the velocity necessary to stay in space. But that is an interesting point. On a super-Earth, with super-sized mountains or super-thick atmosphere, it might be more useful to start from an extremely high place so that you don't have as much atmosphere to deal with.
  - alonmower 8y ago
    Definitely, though being able to walk to the edge of the atmosphere could let you do things like use rail guns to get payloads up close to orbital speeds
  - kd5bjo 8y ago
    The next logical step after this is a space elevator. Because the structure is mechanically linked to the rotation of the planet below, you can achieve orbital velocity simply by climbing up to geostationary altitude and pushing off. I'm almost certain that there are physical limits that prevent such a thing from forming naturally, but I don't know how close to it something like a mountain can get without collapsing under its own weight.
  - macintux 8y ago
    > On a super-Earth, with super-sized mountains or super-thick atmosphere, it might be more useful to start from an extremely high place so that you don't have as much atmosphere to deal with. The paper tackles this. Mountains should be shorter on a super-Earth.
  - stcredzero 8y ago
    Walking to the altitude of space and standing on something is very, very different than accelerating to the velocity necessary to stay in space. But an Olympus Mons sized mountain with a summit in 30 pascals atmosphere would allow someone to more easily build a very dandy and useful mass driver.
  - ComputerGuru 8y ago
    > On a super-Earth, with super-sized mountains or super-thick atmosphere Not a physicist nor a geologist, but I feel a super earth would have a harder time cresting higher peaks due to gravity’s increased effect. It’s not going to look like “earth, only uniformly bigger.”
  - adrianN 8y ago
    No, when you walk up to space using a sufficiently tall mountain you automatically get the necessary speed. You just need a mountain that takes you up to geosynchronous orbit. That's the whole point of a space elevator. Even if the mountain doesn't take you up to that elevation, you gain speed in the same way as starting from the equator helps.
larkeith 8y ago
I would imagine spaceflight would be much cheaper, more reusable, and widespread in general - space elevators would be much easier to construct, as would fully reusable SSTOs; even if the gravity remains too strong or material sciences too undeveloped for either to be feasible, since the cost of reaching orbit changes exponentially based on surface gravity. Also of note is that interplanetary transfers would be cheaper, thanks to a lower escape velocity. A rather utopian view envisions a society of many space elevators scattered across the world, with orbital stations attached via monorail-esque shuttles. Spaceborne hubs with electromagnetic launchers could provide cheap transit beyond the immediate gravity well, while autonomous solar sail harvesters could collect asteroids for resources. Orbital solar farms might provide power on a massive scale for the surface, and lenses or mirrors could be used to assist in terraforming bodies further from the system's sun (for example, a Europa-equivalent). For planets without a significant atmosphere, you get to do fun stuff like Arthur C Clarke's Lunar mass driver [1]. [1] https://en.wikipedia.org/wiki/Mass_driver https://en.wikipedia.org/wiki/Mass_driver

by scj 8y ago

I've always been interested in the other case: What advances in spaceflight would be made by a technologically similar civilization if they had much lower gravity?

pronoiac 8y ago

I read some musings by Warren Ellis [1] which brushed up against easier space travel, very briefly: "The Olympus Mons mountain on Mars is so tall and yet so gently sloped that, were you suited and supplied correctly, ascending it would allow you to walk most of the way to space. Mars has a big, puffy atmosphere, taller than ours, but there’s barely anything to it at that level. 30 Pascals of pressure, which is what we get in an industrial vacuum furnace here on Earth. You may as well be in space. Imagine that. Imagine a world where you could quite literally walk to space." It's mostly not about your question, but I liked this part. [1] http://www.warrenellis.com/?p=14314 http://www.warrenellis.com/?p=14314

LeifCarrotson 8y ago
Walking to the altitude of space and standing on something is very, very different than accelerating to the velocity necessary to stay in space. But that is an interesting point. On a super-Earth, with super-sized mountains or super-thick atmosphere, it might be more useful to start from an extremely high place so that you don't have as much atmosphere to deal with.
- alonmower 8y ago
  Definitely, though being able to walk to the edge of the atmosphere could let you do things like use rail guns to get payloads up close to orbital speeds
- kd5bjo 8y ago
  The next logical step after this is a space elevator. Because the structure is mechanically linked to the rotation of the planet below, you can achieve orbital velocity simply by climbing up to geostationary altitude and pushing off. I'm almost certain that there are physical limits that prevent such a thing from forming naturally, but I don't know how close to it something like a mountain can get without collapsing under its own weight.
- macintux 8y ago
  > On a super-Earth, with super-sized mountains or super-thick atmosphere, it might be more useful to start from an extremely high place so that you don't have as much atmosphere to deal with. The paper tackles this. Mountains should be shorter on a super-Earth.
- stcredzero 8y ago
  Walking to the altitude of space and standing on something is very, very different than accelerating to the velocity necessary to stay in space. But an Olympus Mons sized mountain with a summit in 30 pascals atmosphere would allow someone to more easily build a very dandy and useful mass driver.
- ComputerGuru 8y ago
  > On a super-Earth, with super-sized mountains or super-thick atmosphere Not a physicist nor a geologist, but I feel a super earth would have a harder time cresting higher peaks due to gravity’s increased effect. It’s not going to look like “earth, only uniformly bigger.”
- adrianN 8y ago
  No, when you walk up to space using a sufficiently tall mountain you automatically get the necessary speed. You just need a mountain that takes you up to geosynchronous orbit. That's the whole point of a space elevator. Even if the mountain doesn't take you up to that elevation, you gain speed in the same way as starting from the equator helps.

larkeith 8y ago

I would imagine spaceflight would be much cheaper, more reusable, and widespread in general - space elevators would be much easier to construct, as would fully reusable SSTOs; even if the gravity remains too strong or material sciences too undeveloped for either to be feasible, since the cost of reaching orbit changes exponentially based on surface gravity. Also of note is that interplanetary transfers would be cheaper, thanks to a lower escape velocity. A rather utopian view envisions a society of many space elevators scattered across the world, with orbital stations attached via monorail-esque shuttles. Spaceborne hubs with electromagnetic launchers could provide cheap transit beyond the immediate gravity well, while autonomous solar sail harvesters could collect asteroids for resources. Orbital solar farms might provide power on a massive scale for the surface, and lenses or mirrors could be used to assist in terraforming bodies further from the system's sun (for example, a Europa-equivalent). For planets without a significant atmosphere, you get to do fun stuff like Arthur C Clarke's Lunar mass driver [1]. [1] https://en.wikipedia.org/wiki/Mass_driver https://en.wikipedia.org/wiki/Mass_driver