4 ms·

Let me know when we build suspended structures the size of stadiums that are air tight. Spinning orbital structures have to basically hang from themselves and

by shkkmo 4y ago

Let me know when we build suspended structures the size of stadiums that are air tight. Spinning orbital structures have to basically hang from themselves and deal with primarily tension forces rather than compression forces.

ben_w 4y ago
The scale in tensile form was achieved at least 23 years ago. Now, I know you're going to say "not airtight", and that's correct, I'll get to that: https://en.wikipedia.org/wiki/London_Eye https://en.wikipedia.org/wiki/London_Eye Also very nearly that scale 130 years ago: https://en.wikipedia.org/wiki/Ferris_Wheel_(1893) https://en.wikipedia.org/wiki/Ferris_Wheel_(1893) Making ferris wheels airtight is somewhat pointless, but would be in certain regards easier in freefall than on the ground as (a) it doesn't need to start off spinning and therefore doesn't need to be stable until it's finished, and (b) there's not going to be the same concerns about metal fatigue because the force isn't going to constantly change direction from the reference frame of any given element. If that can be balanced against (c) we've barely scratched the surface of space manufacturing and don't know what to expect, remains to be seen.
- shkkmo 4y ago
  The London Eye is about 2/3rds of the size of a stadium. In addition, a ferris wheel has nothing like the mass you need to support for a space station. There is no question that building a rotating structure with that kind of mass at that kind of scale rotating at those kinds of speeds is going to create significant novel engineering problems. Those problems become even bigger when you consider that this structure has to be built in space (we've never built anything of this size in space, let alone tried to spin it up) and you have to solve problems like thermal expansion/contraction that will only get harder with scale.
  - ben_w 4y ago
    > The London Eye is about 2/3rds of the size of a stadium. In addition, a ferris wheel has nothing like the mass you need to support for a space station. You're being too literal, "stadium" isn't an SI unit and 120 metres is bigger than the 112 meters suggested in the article up-thread, so the technicality is not an important point. Also, the core point is that the tensile strength required is nothing special. Indeed this is why the O'Neill designs are the size they are (8x32 km) and you only need to jump to mass-produced carbon nanotubes for the much larger and more ridiculous McKendree cylinder (size: Russia). > kinds of speeds is going to create significant novel engineering problems No doubt, novel things usually do even on the ground, that's why civil engineering is the discipline that it is — but can you name any not already faced by, say, suspension bridges? In particular: what is speed supposed to do in this case, given its in space, and chosen specifically for 1g acceleration like everything on Earth is anyway?

by shkkmo 4y ago

ben_w 4y ago

The scale in tensile form was achieved at least 23 years ago. Now, I know you're going to say "not airtight", and that's correct, I'll get to that: https://en.wikipedia.org/wiki/London_Eye https://en.wikipedia.org/wiki/London_Eye Also very nearly that scale 130 years ago: https://en.wikipedia.org/wiki/Ferris_Wheel_(1893) https://en.wikipedia.org/wiki/Ferris_Wheel_(1893) Making ferris wheels airtight is somewhat pointless, but would be in certain regards easier in freefall than on the ground as (a) it doesn't need to start off spinning and therefore doesn't need to be stable until it's finished, and (b) there's not going to be the same concerns about metal fatigue because the force isn't going to constantly change direction from the reference frame of any given element. If that can be balanced against (c) we've barely scratched the surface of space manufacturing and don't know what to expect, remains to be seen.

shkkmo 4y ago
The London Eye is about 2/3rds of the size of a stadium. In addition, a ferris wheel has nothing like the mass you need to support for a space station. There is no question that building a rotating structure with that kind of mass at that kind of scale rotating at those kinds of speeds is going to create significant novel engineering problems. Those problems become even bigger when you consider that this structure has to be built in space (we've never built anything of this size in space, let alone tried to spin it up) and you have to solve problems like thermal expansion/contraction that will only get harder with scale.
- ben_w 4y ago
  > The London Eye is about 2/3rds of the size of a stadium. In addition, a ferris wheel has nothing like the mass you need to support for a space station. You're being too literal, "stadium" isn't an SI unit and 120 metres is bigger than the 112 meters suggested in the article up-thread, so the technicality is not an important point. Also, the core point is that the tensile strength required is nothing special. Indeed this is why the O'Neill designs are the size they are (8x32 km) and you only need to jump to mass-produced carbon nanotubes for the much larger and more ridiculous McKendree cylinder (size: Russia). > kinds of speeds is going to create significant novel engineering problems No doubt, novel things usually do even on the ground, that's why civil engineering is the discipline that it is — but can you name any not already faced by, say, suspension bridges? In particular: what is speed supposed to do in this case, given its in space, and chosen specifically for 1g acceleration like everything on Earth is anyway?