ballonet

詳細解釋：

bal.lo.net

n.（名詞）
One of several small, auxiliary gasbags placed inside a balloon or a nonrigid airship that can be inflated or deflated during flight to control and maintain shape and buoyancy.
輔助氣囊：置於氣球或軟式飛艇內的一個小的、輔助性的氣囊，可通過在飛行中的充氣和放氣來控制和保持形狀和浮力

來源：
French ballonnet [diminutive of] ballon [balloon] * see balloon
法文 ballonnet [] ballon的小後綴 [氣球] *參見 balloon