A gas balloon is a balloon that flies in the air because it is filled with a gas less dense than air or lighter than air (such as helium or hydrogen).
Unlike the hot air balloons, which go up and come down in a couple of hours, the gas balloons participate in a cross-country distance race. The race lasts a couple of days, and the balloon that travels the longest distance wins.
The balloons here are filled with hydrogen. To begin, the gas delivery tube is attached from the tanks to the balloon. Crew members sit on the opening until enough gas is in the balloon to make it stand upright,
then they jump off to let the balloon rise and continue the filling.
When the balloon is filled the tube is disconnected and the balloon is launched.
The balloon operates by the light gas raising the balloon. As the balloon rises the gas cools. To obtain more height the balloon carries “ballast”, which are bags filled with sand. Less ballast = less weight and the balloon rises. As this process repeats itself, the ballast is used up, and the balloon must land.