Q:

Lunar launch pad cooling

I read recently about the huge volumes of water that is sprayed on a launch pad during lift off. I remember it to be about four times as much water as fuel burned. This is done to reduce noise (energy that would have become acoustic, instead taken up in change-of-state i.e. water to steam) and to help the launch pad survive the heat, so it can be used again.
I occurred to me that in a vacuum, like on the moon, a landing and launch facility cannot spray water on the launch pad to protect it. 
Is anyone aware of studies of what a lunar launch pad would look like and how it would survive the heat of launch?

A:

I haven't seen studies, but there are ways to build a launch pad without water cooling. The Soyuz launch pads for instance are built over the edge of a large hole in the ground:

This would work on the Moon as well. The main issue would be loose rubble at the bottom of the pit being launched across the Moon or even into orbit. 

