This sounds very much like what I read about how pilots on the front line rest. They would spend a lot of time in the air, and anytime there was downtime you took it. Some kind of research went into it and they came up with an entire process that would involve relaxing your body from head to toe, and then visualizing yourself somewhere else, like a boat in a lake or relaxing on a hillside. If you fail, you do the whole thing over. With enough training your mind becomes very adaptive and you can fall asleep faster and in highly disruptive environments. I believe it also had roots in meditation, where the more you do it the easier it gets.