Hot air balloons are the oldest, successful flight technology, and its flight relies on Archimedes' principle of buoyancy and Ideal Gas Laws. Air inside the balloon is heated, causing gas molecules to disperse and achieve a lower average density. The density gradient of air inside the balloon and air outside allows resultant buoyancy, as long as the density of air trapped in balloon is lower than that of surrounding air , . The heating to achieve lower density in the trapped air of the balloon is done through the use of fuels, with the most common being propane fuels. Propane is preferred over other hydrocarbons because its low boiling point allows a consistently higher vapor pressure for a given temperature, and is therefore a more efficient fuel.
Hot air balloon is still used for recreation and scientific experiments, including Cosmic Microwave Background studies and astronomy. With the high number of uncertainties in steering balloons, it is crucial then to investigate the factors that man can control in order to reduce accidents and assure successful flights. In terms of fuel used, Propane is retrieved from petroleum fractions and is therefore non-renewable. With the peak oil point expected to fall within the century , the question of fuel efficiency is a topic worth investigating in reducing the rate of oil depletion.
Parts of a Hot Air Balloon .
The envelope is the actual part of the 'balloon'. Air is not restricted from the bottom; the hot air would need to rise up to create a temperature gradient. It also allows a passage for oxygen flow for the combustion of fuels. It is made of heat resistant nylon, which prevents scorching, and coated with polyurethane or silicon, which traps heat within the envelope . .
The parachute valve is a retractable opening that is sealed by the pressure equilibrium during flight. It is used during descent to lower the temperature difference. .
