Spreading out the load seems a good idea in general. How about a robotic sealer that tracks along a group of six panes and sits down slowly as it has a large valve to allow a softer action.Edit/ This same bot could be used on the outside to clean off dust, otherwise it might end up being the little bot that never gets used.
@Ionmars Yah it doesn't show perspective very well, but the view shown is actually on the inside. Sorry about the confusion.
This post is a follow-up to my previous Reply #313 in this thread. Here I present a better sketch of the modified dome structure and a further modification. The idea is to employ a series of “super-hoops” that are over-designed to resist tension forces.
That design will be vulnerable to torsion and lateral stress. A geodesic by design resists torsion and stress equally from all directions.That doesn't make them perfect. From a mass perspective, the optimal shape involves trusses. Geodesics are simpler to build than truss structures, but the bending moment of inertia is proportional to the thickness of a beam to its, what, third power? Haven't done a FEA run in half a year so I'm a bit rusty But basically if you want to maximize stress and minimize mass, you have a heirarchy of structural members, with small numbers of those of the greater thickness, leading to greater numbers of less thickness, and so forth, all the way to the glazing.Of course, your lowest mass structures are pressure-supported.
Just thinking about the environment... I'm betting that corrosion between dissimilar metals is going to be huge. Normally your panels basically act like charge collectors even on Earth, accelerating corrosion between, for example, an aluminum frame and stainless bolts, or whatnot. But on Mars they'll be far more effective at it. Every last element that contacts every last other element better be very resistant to galvanic corrosion, w/proper isolation.
On the upside: unlike on Earth, most of your stress on Mars is self-loading. Your wind / snow and even dust loads will be very small. And of course gravity is lower. Only in cases where you want to pile regolith on top do you have to deal with heavy loadings per square meter.Anchoring will be a pain, however. Maybe earth screws? Better pick an area that's not shallowly underlain by bedrock...Just thinking about the environment... I'm betting that corrosion between dissimilar metals is going to be huge. Normally your panels basically act like charge collectors even on Earth, accelerating corrosion between, for example, an aluminum frame and stainless bolts, or whatnot. But on Mars they'll be far more effective at it. Every last element that contacts every last other element better be very resistant to galvanic corrosion, w/proper isolation.(I know some people have talked about CF-framing.... I've never heard of anyone making a CF-framed greenhouse, so I have no clue how well that'd actually work. They make fiberglass greenhouses (I never have), which are good in some regards, but vulnerable to UV and are flammable. But CF with an advanced binder might be able to work around that (at significantly greater material cost - but that's typical for space applications)
Domes sound fancy, but what about good old fashioned pyramids? To me it seems much easier to work with (and produce) flat surfaces.
......The last time I designed a greenhouse, it was an isogrid, about twice as long as it was wide, so I tried using the asymmetry to allow me to focus reinforcements predominantly on the narrow axis. It didn't work, even in that "easier" case. The shape tries to twist or lean and overload the weaker elements on the long axis.The same will happen to you here, but even moreso. If you try to put all of your strength on one axis, it'll transfer to the weak elements and overstress them. Also: it's nice and easy to draw a bunch of random elements. It's a whole different ballgame when you have to actually join them together in a buildable fashion. And account for the strength of the joints in your FEA run.
Quote from: Rei on 11/23/2016 10:59 am......The last time I designed a greenhouse, it was an isogrid, about twice as long as it was wide, so I tried using the asymmetry to allow me to focus reinforcements predominantly on the narrow axis. It didn't work, even in that "easier" case. The shape tries to twist or lean and overload the weaker elements on the long axis.The same will happen to you here, but even moreso. If you try to put all of your strength on one axis, it'll transfer to the weak elements and overstress them. Also: it's nice and easy to draw a bunch of random elements. It's a whole different ballgame when you have to actually join them together in a buildable fashion. And account for the strength of the joints in your FEA run.Thanks for sharing your experience. My intuition and some of the earlier posts were wrong. So as the size of dome increases you should only increase the thickness and strength of all members equally. Eventually the members are so thick as to crowd out any usable glass panes. Se la vie, Elon.
There has been a lot of discussion about anchoring these domes but as they will be pressurized, how would they be sealed where the dome meets the regolith?
Quote from: oiorionsbelt on 11/25/2016 11:34 pmThere has been a lot of discussion about anchoring these domes but as they will be pressurized, how would they be sealed where the dome meets the regolith?Either the wall is buried a few feet down,or there is an airtight membrane brought in towards the center of the floor.