The heavy part of the dome will be the glass panels. The structure won't be too bad, though sealing the triangles may be annoying. But anchors just need to be deep enough that their friction cones have enough surface area on the non-overlapping side. It's fine that they overlap, it's just that the overlapping area doesn't count so much. As long as the total weight of the volume of the soil in all the cones is equal to the pressure times bottom area of the dome, you're fine.To ensure this, you just need long enough cables. Cables made out of the right material can have an extremely good strength to density ratio, like 4GPa/(g/cc). Much stronger than the Windows or the quasi-isotropic Carbon fiber composite of the frame, which would be around 0.4GPa/(g/cc) (much worse for the glass due to knock-downs for stress concentrations). Then the anchors themselves, but if the cables are long, the anchors will be a minority of the mass.So the anchors and cables would be much less mass than a whole sphere. Also, realize that you still have to solve the problem of how to properly rest on the soil and walk around on the sphere.And there's another thing: you could have a vertical cable in the center of the dome anchored deep underground. This could carry some of the load as well. The dome wouldn't have to be so high for a given area.
To ensure this, you just need long enough cables. Cables made out of the right material can have an extremely good strength to density ratio, like 4GPa/(g/cc). Much stronger than the Windows or the quasi-isotropic Carbon fiber composite of the frame, which would be around 0.4GPa/(g/cc)
Anchors AwayIf you pick a commercial ground engineering system and run the numbers, you can really advance the NSF dome anchoring designs. Just sayin'.
Would the use of structural panes lend themselves to single replacement after the dome is built?Couldn't the overlap issue of friction cones be alleviated by staggering the depth of them? I would be more concerned with how the failure of one effects the other, otherwise.
Does the dome have to be sealed, as in 100% air tight pressure vessel or is it enough to have it at positive pressure(PP)? I mean, considering that ISRU fuel production is a hard requirement to land people (iirc), industrial scale O2 and N2 production and CO2 processing would already be there when they start to dome up. Wouldn't a PP, open system, dome relax the structural requirements, particularly the anchoring PITA at hand?Yes, you can't have short sleeve / breathable environment from that way, but you can have a much more benign one under the dome: Less dust, thermal balance, attenuated radiation and pressure environment... Could probably grow stuff at low (1/2atm?) pressure and reduce the personal protection to rebreather and MCP suits....Yes, it's wasteful, but I suggest to allow an abundance in some resource, else this whole enterprise is, probably, doomed if it has to squeeze every margin. Energy abundance would seem the most beneficial (I.e nuclear vs PV), allowing ISRU overproduction, which can't be bad, fuel and ECLSS wise.
Quote from: mfck on 11/14/2016 09:58 amDoes the dome have to be sealed, as in 100% air tight pressure vessel or is it enough to have it at positive pressure(PP)? I mean, considering that ISRU fuel production is a hard requirement to land people (iirc), industrial scale O2 and N2 production and CO2 processing would already be there when they start to dome up. Wouldn't a PP, open system, dome relax the structural requirements, particularly the anchoring PITA at hand?Yes, you can't have short sleeve / breathable environment from that way, but you can have a much more benign one under the dome: Less dust, thermal balance, attenuated radiation and pressure environment... Could probably grow stuff at low (1/2atm?) pressure and reduce the personal protection to rebreather and MCP suits....Yes, it's wasteful, but I suggest to allow an abundance in some resource, else this whole enterprise is, probably, doomed if it has to squeeze every margin. Energy abundance would seem the most beneficial (I.e nuclear vs PV), allowing ISRU overproduction, which can't be bad, fuel and ECLSS wise.what's the point in building a gigantic glass dome ifyou cannot really going around it without a mask?
Quote from: Robotbeat on 11/14/2016 12:31 amTo ensure this, you just need long enough cables. Cables made out of the right material can have an extremely good strength to density ratio, like 4GPa/(g/cc). Much stronger than the Windows or the quasi-isotropic Carbon fiber composite of the frame, which would be around 0.4GPa/(g/cc) The anchors, by definition, have to hold the same load as the frame. If the anchor-cables are so mass-efficient, why wouldn't you just use them as the tensile frame as well?
But I do think that the habitats have to be pressure vessels, and doors from the habitats to the dome should be airtight and normally closed.
Quote from: meekGee on 11/14/2016 02:36 pmBut I do think that the habitats have to be pressure vessels, and doors from the habitats to the dome should be airtight and normally closed.I think, emergency shelters would be good enough. No need to build the whole habitats pressure resistant.
.........After the dome is up, maybe the atmosphere in the dome is high in CO2 (how much is still ok for people) and maybe you have the ability to pump in CO2 to keep pressure if there a small leak. (Though that's a large pump)....