Soma: You asked a fair question and I will endeavor to answer it as best I can. Liquids and gases are both fluids. When you heat water, it expands. When you heat helium, it too expands. With expansion comes an increase in pressure. You don't want to exceed the airship designed pressure limits.
When a liquid cools, it consdenses somewhat. Water is the exception to the rule. It expands when heated and expands when frozen into ice. The reason ice floats on water is because of that expansion. It still has the same weight, but has increased in size to where its volume is greater than the water it contains and thusly floats. When you cool a gas, it condenses and pressure is lost. When helium condenses, lift is lost.
So, it is important to maintain BOTH temperature and pressure within the gas cells. The objective is to maintain a point of equillibrium at all times. THAT is hard to do.
As I said before in previous posts, Uli is quite aware of the temperatures at high altitude and he intends to used internal heaters with his equipment. Most of it will be packaged in thermal insulation to conserve heat.
The temperature at 65,000 feet is -67F. That is just an average mean temperature. At night it gets much colder. In daylight, somewhat warmer, but -67 is the AVERAGE of the two.
HEAT FLOWS FROM WARM TO COLD. Heat is an energy that is trying to seek out its own equillibrium. Any heat in the gas cells will try to escape in an endeavor to try and warm up the surrounding outside air. Heat flows. Therefore, the big trick is to try and contain it when you want it, and try to rid yourself of it when you don't need it.
Maybe we should consult Chris Angel about this!
No man should be considered totally useless....because he can always serve as a bad example.
