What happens if you cast Astral Projection while physically on the Astral plane?

[Frost]

Oh? Have they given any thought to what the various beasties on the Astral will do to their uninhabited forms? It'd be a race against time to get back to the Astral Plane before their physical bodies are destroyed.

Have you never made or found an Astral Fortress? We totally build our own Super Astral Fortresses.