Date: 30 Mar 99 01:53:37 From: James Matthew Weber <email@example.com> References: 1
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At 01:25 AM 3/17/99, Balaji.Ramanathan@ual.com wrote: > I found out recently that conventional submarines (as opposed >to nuclear ones) have a double layered hull and the space between >the two layers is used to store fuel. I am wondering if this >approach is viable for airliners. > > Extremely rough back-of-the-envelope calculations seem >to indicate that if a 747 fuselage had a double jacket with a one-inch >gap for fuel, the fuel capacity can be increased by roughly 10000 >gallons (about 70000 lbs). I would guess this is quite a significant >amount of extra fuel and can potentially increase the range without >impacting cargo storage or passenger space. I doubt it is a very practical approach, for several reasons. First of all the amount of metal (weight) you need is optimal for a spherical tank (largest volume to surface ratio), long thin tanks will have a very unfavorable volume to surface ratio, so for a given volume of fuel, you will need a lot more weight. The bad volume to surface ratio causes another problem. The fuel is now all stored in direct contact with the outside surface of the aircraft.There is lots of surface area to conduct the heat away. That surface is typically exposed to very low temperatures at cruise, especially at high latitudes such as over the North Atlantic and North Pacific. I don't have exact figures for JetA, but most mid distallate fuels starts to solidify at about -45F, which is a very realistic temperature outside the aircraft at cruise.