Physics of Gas Ballooning Lift at Sea Level Equipment Theory of Gas Ballooning Lift at Altitude Complete books have been written on the theory of gas  ballooning and a full discussion of the topic is not possible  here. At the very least, three topics must be understood by  the competent gas pilot: physics, weather aspects, and the  significance of different lifting gases.  As a balloon ascends, it is generally true that temperature,  atmospheric pressure, and gross lift all decrease. Gross lift  decreases as pressure decreases, but increases as temperature  decreases. Thus, as a gas balloon rises in the atmosphere, the  decreasing pressure and temperature oppose each other. The  decreasing temperature increases lift while the decreasing  pressure decreases lift. Atmospheric pressure changes are  more significant than temperature changes. Thus, net lift  decreases as altitude increases in a standard atmosphere. cabling should have a breaking strength of at least five times  the maximum gross load that is suspended on the cables.  This must include sand ballast, as well as the weight of the  gondola, the occupants, and all supplies and equipment. For hydrogen systems, the cabling must be electrically  conductive. For ammonia systems, the cables should be long  enough to separate the occupants of the gondola from gas  fumes coming out of the appendix.  The bottom end of the cabling is gathered at a load ring which  acts as the interface between the envelope and the gondola  cables. The load ring also serves as the system’s strong point  for attachment of inflation harnesses or trail ropes.  Equipment carried varies with the purpose of the flight. A minimum equipment list should include an altimeter/ variometer, compass, global positioning system (GPS),  aircraft position lights, several flashlights (for night flights),  oxygen (for high altitude flights), aircraft radio, and  aircraft sectional maps for navigation and communication.  [Figure 11-6]  Other items which may be included for safety  and occupant comfort may include: a first aid kit, adequate  food, water, warm clothing, and toilet facilities for both  the planned flight and for the postflight period before the  recovery crew arrives.  The generation of buoyancy (commonly referred to as “lift”)  in a gas balloon is somewhat different from that of a hot air  balloon. The basic principle is the same, but for different  reasons. One cubic meter of air weighs 2.702 pounds at sea level  under International Standard Atmosphere (ISA) conditions  (29.92 inches of mercury ("Hg) and 59 degrees Fahrenheit  (°F) at sea level). At the same time, and also under ISA  conditions, a cubic meter of helium weighs 0.3729 pounds.  The difference between these two numbers, 2.329 pounds,  is the gross lift of a gas balloon with a volume of one cubic  meter. To determine the gross lift under ISA conditions, it then  becomes a simple multiplication of 2.329 pounds times the  volume of the envelope. For the standard 1,000 cubic meter  gas balloon, the gross lift is 2,329 pounds.  The above calculation is valid for helium. If, however,  hydrogen is used as the lifting gas, the factor is 0.189 pounds  per cubic meter; anhydrous ammonia’s weight is 1.583  pounds per cubic meter. As compared to helium, hydrogen  has 8 percent more gross lift per cubic meter, while ammonia  has approximately 50 percent less lift than helium under ISA  conditions. Four main factors are instrumental in determining lift: 11-5 4.  Ambient barometric pressure (which is directly related  to altitude and local weather conditions). 3.  Outside air temperature 2.  Amount of lifting gas in the envelope (usually equal  to the envelope’s total capacity) 1.  Type of lifting gas used (e.g., helium, hydrogen, or  anhydrous ammonia) $_{Figure 11-6.}$  Instruments and radios are sometimes carried in a  pod such as this.