1/The Lava Tubes Hypothesis
There is a growing interest in the scientific community about the many rilles that can be found on the near side of the Moon. These rilles formed as a result of the extrusion of basaltic magma, some of which have evolved into lava tubes when segments of the channel roofed over.
These lava tubes can be so large, thanks to the low gravity that an entire city would fit in!
These natural cavities would be ideal for housing a manned lunar base because they provide natural protection against radiations, meteorites and extreme temperatures variations.
The temperature inside a lava tube is at a constant -20°C. Some cities on Earth are much colder. For example, the habitants of of Oïmiakon, Russia, enjoy an temperature less than -30°C between November and March.
If they can make it on Earth, we can make it on the moon!
The lava tube we choose to built our scientific village is located in the northern region of Oceanus Procellarum. It is a very well known region and easy to land for a spaceship.
Regolith will be used to generate water, that we will store outside (in the from of ice) without any protection, since temperature is constant. The ice will then be transformed into oxygen and hydrogen, and of course water!
One technical difficulty that we will need to address is the 2 weeks nights. During these nights, solar panels will be useless. The hydrogen extracted from the regolith will certainly be the key.
2/ Dry Stone Construction
Lunar mares are made of basalt.
On the moon, a block of basalt of 1x,0,5×0,5 weight only 40kg, gravity being 1/6 of Earth.
On Earth, One the the highest dry stone construction, the Agamemnon tomb in Mycenae, is about 15 meters hight. On the moon with much lower gravity, we can built without difficulty building of 60m or higher, using the same technique our Greek ancestors did.
The advantage of this approach is obvious: no building material needs to be brought from earth. Once you have brought the machinery to extract and freestone, you can built an entire city.
Only aerogel insulation and a kevlar layer to keep air inside is needed. And since the buildings are situated in a cave where temperature is constantly at -20°C, insulation will be very light.
Therefore it becomes possible to built large volumes easy to heat.
Caves are dark. Astronauts are unable to move freely because of the heavy suits they need to wear to live in the difficult environment on the moon. Therefore we want to built large, and luminous volumes to give them all the pleasure of natural space we enjoy on planet Earth, and that they will miss so much.