It’s not the same, but it’s similar to physical sex, depending on what astral senses you’re using during an astral project session.
You don’t need Clairvoyance (seeing), unless you want to watch a stripshow and masturbate to it.
You don’t need Clairaudience (hearing)…unless you want to talk dirty, like a phonesex call.
…but you do need Clairsentience (feeling) and an open Head Chakra for the physical experience. Of course you can combine the ability to feel with seeing and hearing to enhance the experience, but it’s not as essential, because the physical act of sex speaks in volumes solely on the behalf of the ability to feel.
Astral sex, and sex with spirits are much more powerful, because the sexual act stimulates the entire nervous system and the physical stimulation goes beneath the first layer of our skin. Why? Because the electrical conduits is our nerves and our bloodstream is more sensitive to spirit energies. A spirits touch is often much weaker on the top of our skin, in contrast to the resistance behind the layers.