Author Topic: Artificial Gravity - Why Weight?  (Read 29296 times)

Offline lamontagne

  • Full Member
  • ****
  • Posts: 1025
  • Liked: 1416
  • Likes Given: 229
Re: Artificial Gravity - Why Weight?
« Reply #140 on: 03/05/2017 12:40 AM »


But I think building habitats from asteroid regolith can happen sooner than you're expecting, it's just that you can't do anything clever with it.  I'm thinking something along the lines of a mold that takes loose regolith and stamps/sinters it into segments of a large scale torus.  You use the regolith as your compressive component, and import (steel) cables from Earth as your tensile component when you want to fuse the whole thing together.  Such massive structures will be much easier to work with in microgravity.



How about using basalt fibers to reinforce some form of concrete?
http://novitsky1.narod.ru/babv1.html.htm
Or even basalt fiber to reinforce sintered basalt?  The fiber has higher strength because of the low defects, and the sintered basalt serves as fill.

Offline mikelepage

Re: Artificial Gravity - Why Weight?
« Reply #141 on: 03/13/2017 04:09 AM »
But I think building habitats from asteroid regolith can happen sooner than you're expecting, it's just that you can't do anything clever with it.  I'm thinking something along the lines of a mold that takes loose regolith and stamps/sinters it into segments of a large scale torus.  You use the regolith as your compressive component, and import (steel) cables from Earth as your tensile component when you want to fuse the whole thing together.  Such massive structures will be much easier to work with in microgravity.

How about using basalt fibers to reinforce some form of concrete?
http://novitsky1.narod.ru/babv1.html.htm
Or even basalt fiber to reinforce sintered basalt?  The fiber has higher strength because of the low defects, and the sintered basalt serves as fill.

Interesting, I started responding to this days ago but apparently I never posted it.  I googled this at the time and found that the fibers can only be obtained from particular quarries? I wonder how likely we are to find something like this at asteroids. Or were you thinking to ship it from Earth? Must be pretty massive.

Offline Rei

  • Full Member
  • ****
  • Posts: 471
  • Iceland
  • Liked: 183
  • Likes Given: 58
Re: Artificial Gravity - Why Weight?
« Reply #142 on: 03/13/2017 11:59 AM »
I'm actually building a house out of basalt fibre reinforced concrete

Note that as a general rule, you don't use raw fibres, you use fibres embedded in a plastic binder. I've seen videos from one guy who's building homes just out of raw roving, but from the longevity studies I've seen, I wouldn't trust that. Even if you were only using raw fibre, this would be incompatible with basalt sintering; the fibres lose their strength when you heat them to sintering temperatures. The plastic would be lost first of course. And basalt doesn't sinter well, it likes to fracture. That said, basalt aggregate often makes for a very good concrete. You need a proper binder, though.

I would be hesitant to attempt production of basalt fibre offworld. I've read about the nuances of the production processes and it's not something I'd expect to work well in the "simple / low maintenance / low human involvement" category.  It's tougher than glass fibre production - temperatures are higher, the melt is optically opaque so overhead heating doesn't work well, and various components tend to precipitate out of the mix at different temperatures. Blowing methods would be harder on Mars than on Earth due to the low density (the local environment shouldn't affect the approaches based on drawing from spinnerets)

As for the "particular quarries" thing... that's more a statement of the fact that you can't just use any old basalt and get the same properties.  Each source has to be qualified on its own. Basalt fibre reinforcement is a relatively small (but growing) market these days.  Still, it has a lot of appealing properties. In most regards carbon fibre is significantly superior, but CF is very expensive and requires a lot more energy to produce.  But compared to glass fibre, BFRP is "somewhat better" in almost every measure.
« Last Edit: 03/13/2017 11:59 AM by Rei »

Offline Rei

  • Full Member
  • ****
  • Posts: 471
  • Iceland
  • Liked: 183
  • Likes Given: 58
Re: Artificial Gravity - Why Weight?
« Reply #143 on: 03/13/2017 12:19 PM »
Quote
Not quite sure what you mean by counterweighted rollable trusses (I'm assuming you mean baton-stations/tumbling pigeons?)

Rollable composite trusses:



Based on the same principle that lets tape measures work, but taken to much more extreme ends - each strand rolls out to a nearly circular cross section, with snap locks that join the two sides together.  For trusses, all of the truss elements are rolled up together, so the whole truss snaps out and locks.  It's a really interesting tech; it's been worked on for decades, but it finally seems to be maturing.

Quote
There is a third option I'm calling DEployable Spin Gravity Array (DeSGA - small animation attached), which I would put on space craft intended to support humans working out at asteroids.

Interesting.  Seems more complicated than rollable trusses, and seems to fundamentally require large fairings.. but otherwise I see no reason why that wouldn't work.  How do people move between segments?  Is there an airlock at each end that joins up when the structure folds out to a ring?

But I think building habitats from asteroid regolith can happen sooner than you're expecting, it's just that you can't do anything clever with it.  I'm thinking something along the lines of a mold that takes loose regolith and stamps/sinters it into segments of a large scale torus.


It's the "stamping / sintering" around a mould (aka having to relocate it, having the sinterer not just be some enclosed hollow, etc)  that raises big question marks in my mind.  But, who knows?  :)  Work with sintering asteroid material for return to Earth could certainly advance the TRL enough to make it worth a shot.  The latter has always seemed the most obvious way to make asteroid mining with Earth return economic: sinter to a hollow aeroshell shape (simple enclosed mould) and eject with a quench gun (it's iron-bearing, after all) onto an earth-crossing trajectory, either for aerocapture to orbit, or to impact within a particular target ellipse.  Aka, it's its own ablator and entry body.  But to do that you'd have to be able to justify the easily-multi-billion-dollar-per-component cost of developing A) mining infrastructure, B) sintering infrastructure, C) power infrastructure, and D) a quench gun with the capability to impart several km/s dV.  If you've gotten that far, I guess the next stage of having a mobile sinterer and non-self-contained mould might not be so far fetched  ;)
« Last Edit: 03/13/2017 05:09 PM by Rei »

Tags: