Wiktionary
n. Any of several small balloons, inside a dirigible, that can be inflated or deflated to control buoyancy during flight.
Wikipedia
A ballonet is an air bag inside the outer envelope of an airship which, when inflated, reduces the volume available for the lifting gas, making it more dense. Because air is also denser than the lifting gas, inflating the ballonet reduces the overall lift while deflating it increases lift. In this way, the ballonet can be used to adjust the lift as required.
Ballonets may typically be used in non-rigid or semi-rigid airships, commonly with multiple ballonets located both fore and aft to maintain balance and to control the pitch of the airship.
The image illustrates the principle of a balloon within a balloon. 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.
Usage examples of "ballonet".
Anyway, copious quantities of hydrogen gas were pouring from the shaft maw, coming from the rent where the unfortunate brown man had fallen into a ballonet and suffocated.
Vents on the upper surface of the ship were opening, releasing hot air from the ballonets that hung in the center of the hydrogen cells.
Booming and popping sounds came from above, as hot air from the engine exhausts was vented into the ballonets in the gasbags.
Margo trimmed their attitude by adjusting the amount of ordinary air contained in ballonets inside the hydrogen bag.
They opened every release valve on the gas bag and deflated it slowly then trod on the ballonets to help deflate them as well.
She felt light, as if the hydrogen in the ballonets had filled her as well.
Unfortunately, he was holding his knife in one hand and it cut through the netting retaining the bag, as well as through the linen fabric and goldbeater skin of the ballonet.
They seemed to think there was a leak in one of the aft gas ballonets.
A rigging crew had done considerable toward repairing the ripped gas ballonets.
Deseau had guessed right: the dirigible got its lift from hydrogen, the lightest gas and cheap enough to dump and replace after every voyage so that the ballonets didn't fill with condensed water over time.
She felt light, as if the hydrogen in the ballonets had filled her as well.
I’m going to get us down as fast as I can, I’ll have to empty some of the ballonets.
I'm going to get us down as fast as I can, I'll have to empty some of the ballonets.
She felt light, as if the hydrogen in the ballonets had filled her as well.
She would have tossed out pieces of the dirigible frame too, if she could have gotten into the ballonets.