Vance, Frank thanx for the replies. I guess I wasn't clear in describing the ascent phase using pos. bouyancy as "negative gravity" so that propulsion would be achieved on both descent and ascent. I think Karl Stanley's sub (from what I could gather from the website) ballasted down to descend and provide propulsion then used air to ascend, which is what I'm trying to avoid. Will check out your leads, Vance.Thanx againPR