I think it is possible to build strong, airtight domes on the moon, with only moon dust and sunlight as the raw materials, fairly cheaply before the next humans arrive. This method turns moon dust into moon rock, in any desired size and shape and requires no water or frame, just some equipment and a lot of sunlight. The only parts not necessarily built with local materials are the airlock and whatever interior furnishings you might want once humans arrive. It's a crude form of selective laser sintering. A robot sweeps a solar-powered laser beam back and forth across a layer of moon dust within the footprint of your future wall, fusing it into a thin layer of moon rock. Then it spreads a thin layer of moon dust over that and fuses it, and so on. It may take a year for a few robots to build a thick-walled, house-sized igloo, but what's the hurry if humans won't be arriving any time soon? Selective laser sintering is used for fast prototyping of metal parts, normally in a small chamber. But on the moon, it can be done outdoors, since wind isn't an issue. The only building material required is moon dust, which is transformed into monolithic rock of any desired shape, in this case a hollow dome wrapped around and dwarfing an imported airlock. And getting the robots, their solar panels, spare parts, and other equipment to the moon requires less fuel than sending humans, because they're in no hurry to get there and require no life support or fuel for a trip home.
You would be better off adding an air tight inner liner. Not sure I would trust the sintering process to making the mooncrete air tight on it's own. hmmm, not sure sintering will work with lunar dust. Edit: after some googling, it seems that microwave based sintering works, so why not laser based? But then again, microwaving works.
Interesting idea, I wonder what it would cost for a lunar sample return mission to get enough material to test this on. The step after that would be a proof of concept facility landed on the Moon. Lunar soil is going to have some meteoroid impactor debris in it, I wonder if that helps the sintering process or not.
Microwaving the lunar regolith with a rover could be a way of doing some crude paving, but it's not much good for building walls. However, experience with selective laser sintering shows it capable of precisely forming desired objects, and it will work with moon dust. What I'm proposing is actually simpler, in some ways, than the usual selective laser sintering, since the object to be built is just a wall, basically, rather then complex machine parts. That eliminates the most difficult of the usual steps. Sure, you could line it with plastic on the inside or paint it. But the domes I'm proposing offer a lot more protection than the inflatable buildings NASA has mentioned and would be in move-in condition before people even arrived. For testing it here, NASA has moon dust and could have a batch of artificial moon dust made if it doesn't already have enough. The equipment and expertise for testing the process and determining details about doing it on the moon (like how quickly to move the laser back and forth) already exist. Many companies have experience with selective laser sintering with various materials. They could also produce estimates of how long it would take to build a given structure working only during lunar daylight and how large the solar panels would have to be.
Current microwave technology relies on heating water molecules in the target material. Dunno if this would would work with any permancy on material on the surface due to solar hearing. I dunno if microwaves would work efficiently on solids in the regolith. Now, if we were talking Hoth...
Pretty sure NASA did some missions about 40 years ago that brought back samples. Not in this case. Your thinking of microwaving food. http://www.space.com/adastra/adastra_moondust_060223.html
Thanks sojourner. That's pretty interesting. The device would have to be pretty hardy though. The high iron content could reflect a fair amount of energy back into the waveguide, and possibly damage the magentron/klystron/whatever else they'd use for a high power microwave emitter. I'm sure they could design around this factor, though. They could also use the lawnmower type device for ration heating in the field. I have fond memories of "broomstick chicken" cooked in front of a troposcatter radio feedhorn.