Disclosed is a lighter than air vehicle comprising a first envelope, a second envelope located inside the first envelope, and a tube connecting the first envelope to the second envelope. The first envelope and the second envelope are spaced apart so as to define a chamber between the first envelope and the second envelope. The chamber is filled with a lighter than air gas. A first opening of the tube is located at an external surface of the first envelope. A second opening of the tube is located at an internal surface of the second envelope, the second opening of the tube being at an opposite end of the tube to the first opening of the tube.