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> It may even have shattered some of the gravel, meaning that stuff is really more like styrofoam. [...] All those stories of hollowing out an asteroid and turn

> It may even have shattered some of the gravel, meaning that stuff is really more like styrofoam. [...] All those stories of hollowing out an asteroid and turning it into a habitat or generation ship for 50,000 people aren’t looking so prescient. :) Even simpler then, insert giant balloon in the middle, pump it up, cover walls with concerete and you have habitat, no expensive drilling and hollowing out.

db48x 4y ago
What would you gain in that situation? Just some radiation shielding. Most stories about hollowing out asteroids wanted to gain at least some structural rigidity, which in your scenario comes entirely from the concrete you have to ship into space. Ideally you would want to melt the asteroid and blow it up to kilometers across and/or spin it for artificial gravity. Heating and melting foam is harder than solid rock or metal, and spinning it is useless if it has no strength in tension.
- yetihehe 4y ago
  In that case: blow up the balloon, melt rock outside balloon. You could make "cement" from grinding local material plus some binder, that way you bring in less mass. Radiation shielding is also a nice use for asteroid's mass. I'm just saying that blowing up a balloon is easier than extracting several cubic kilometers of rock from inside of asteroid. You can start from that premise and try to find some solutions. > Heating and melting foam is harder than solid rock or metal You can grind it, then blow it with very hot gas onto your baloon, making a nice melted coat of rocks. This technique is already used to repair metal rotor shafts, it deposits machinable metal: https://www.youtube.com/watch?v=NAeBpF84Q9M https://www.youtube.com/watch?v=NAeBpF84Q9M
  - db48x 4y ago
    That would be very fun, but also a lot of gas to ship up from Earth :)
    - yetihehe 4y ago
      You would need oxygen and nitrogen anyway. You could use hot nitrogen (heated resistively or as plasma), you don't need acetylene.
      - db48x 4y ago
        Humans need room–temperature nitrogen, not nitrogen plasma. You would rapidly make the atmosphere inside your bubble unlivable. There are few easy solutions here.
        yetihehe 4y ago
        Then you wait a moment until it cools down. Of course there are few easy solutions, space is very hard environment mercilessly waiting for you to make an error. You can find problems in every step. It doesn't mean you should give up before you start.
- ncmncm 4y ago
  The concrete is just to prevent internal punctures, and provide rigidity in case of punctures. Probably spray foam would serve as well.
- samatman 4y ago
  Structural rigidity in space is 99% tension and 1% compression, due to the lack of gravity, and I'm being generous to compression here. Rock is good at hold itself up against gravity, but is very poor at retaining an atmosphere compared to, say, UHMWP aka Dyneema. Hollowing out an asteroid is more about raw materials and micrometeorite/particle shielding, both of which a slushy will provide in abundance.

db48x 4y ago

What would you gain in that situation? Just some radiation shielding. Most stories about hollowing out asteroids wanted to gain at least some structural rigidity, which in your scenario comes entirely from the concrete you have to ship into space. Ideally you would want to melt the asteroid and blow it up to kilometers across and/or spin it for artificial gravity. Heating and melting foam is harder than solid rock or metal, and spinning it is useless if it has no strength in tension.

yetihehe 4y ago
In that case: blow up the balloon, melt rock outside balloon. You could make "cement" from grinding local material plus some binder, that way you bring in less mass. Radiation shielding is also a nice use for asteroid's mass. I'm just saying that blowing up a balloon is easier than extracting several cubic kilometers of rock from inside of asteroid. You can start from that premise and try to find some solutions. > Heating and melting foam is harder than solid rock or metal You can grind it, then blow it with very hot gas onto your baloon, making a nice melted coat of rocks. This technique is already used to repair metal rotor shafts, it deposits machinable metal: https://www.youtube.com/watch?v=NAeBpF84Q9M https://www.youtube.com/watch?v=NAeBpF84Q9M
- db48x 4y ago
  That would be very fun, but also a lot of gas to ship up from Earth :)
  - yetihehe 4y ago
    You would need oxygen and nitrogen anyway. You could use hot nitrogen (heated resistively or as plasma), you don't need acetylene.
    - db48x 4y ago
      Humans need room–temperature nitrogen, not nitrogen plasma. You would rapidly make the atmosphere inside your bubble unlivable. There are few easy solutions here.
      - yetihehe 4y ago
        Then you wait a moment until it cools down. Of course there are few easy solutions, space is very hard environment mercilessly waiting for you to make an error. You can find problems in every step. It doesn't mean you should give up before you start.
ncmncm 4y ago
The concrete is just to prevent internal punctures, and provide rigidity in case of punctures. Probably spray foam would serve as well.
samatman 4y ago
Structural rigidity in space is 99% tension and 1% compression, due to the lack of gravity, and I'm being generous to compression here. Rock is good at hold itself up against gravity, but is very poor at retaining an atmosphere compared to, say, UHMWP aka Dyneema. Hollowing out an asteroid is more about raw materials and micrometeorite/particle shielding, both of which a slushy will provide in abundance.