[PSUBS-MAILIST] Propane sub

[CWall@swri.edu]

was just thinking if the ballast tanks are not open to the sae at the bottom
pressurising them with propane should not be a problem. when pressurizing
the tank to blow to the surface pressure the tank and valve off only the
water then you have low pressure gas to run the surface. if pressure gets to
low to run the engine effectivly then inject more gas to the sealed tank.
similar to blowing the sanitary tanks on a nuke. you let the tank run
completely dry and you risk blowing air out into the water making one hell
of a racket.

kinda like the new ideas
Walker

  That is what I had in mind for the trim tanks, which would be made of Freon
or empty propane tanks.  But the free flooding ballast tanks would also be
blown with propane, and they would have enough pressure at their vents to feed
directly into the intake of the engine- it really doesn't take much, especially
 with the engine just ticking over.  Since the trim tank is inside the free
flooding ballast tank, you wouldn't get the noise if you blew it completely
dry,  nor would you lose the propane gas or bouyancy-even if the tank collapsed
 or if a line broke, you still trap all the gas in the free-flooding tank for
bouyancy.

  The nice thing about using propane from the free-flooding ballast tanks for
the engine is that the low pressure is constant- which makes it much easier to
meter to the engine.

In any case, I don't anticipate having to blow the free flooding ballast for
surfacing- you'd just do that if you wanted to increase the freeboard at the
end of the day or when going back to the engine operation,, or for emergency or
 rapid ascent.  It's sort of an inelegant maneuver that I'd normally avoid.

Like I said- the operation of this sub is likely to be a bit different-
everything is going to be much slower, at least if you want to conserve
propane. Others might well find this an objectionable characteristic.

Craig Wall