sentences:  The outer balloon represents the airship's outer envelope or gasbag, while the red inner balloon represents the ballonet.In an airship the ballonet would be much smaller relative to the size of the gasbag; for example, in the French airship Lebaudy Patrie the volume of the ballonet was approximately one-fifth that of the envelope.The ballonet was first described in 1783 by Jean Baptiste Meusnier, then a lieutenant in the French Army.