[BreeveKambmak]

Note that we don't necessarily go to the Astral Plane during dreams -- dreams are usually a physical interpretation of experiences beyond the physical, which explains the symbolism encountered. Hence, a weak subjective realm is created in the Astral Plane, but that is a resulting effect, not a true travel into the Astral Plane per se ; we work on many levels, especially inward, when we dream.

As for chakras, no particular structure seems responsible for a projection besides conscience itself, which permeates the whole energy body. We usually project "through" a chakra, but it is not directly responsible for the behavior.

Note also that the creation of an energy double to explore the real time zone provokes strong energetic sensations, but the act of falling asleep is quite gentle in comparison. We do project when we fall asleep, but it is different from the OBEs we read about in books.