1 00:00:05,323 --> 00:00:10,579 >> The tethered aerostats are inflated with two different types of gases. 2 00:00:10,579 --> 00:00:12,961 There's a helium chamber inside the aerostat, 3 00:00:12,961 --> 00:00:17,618 which is the lifting gas that raises the aerostat. 4 00:00:17,618 --> 00:00:21,514 There is also ambient air pumped inside the aerostat 5 00:00:21,514 --> 00:00:25,996 so that we can maintain a constant aerodynamic shape of the aerostat 6 00:00:25,996 --> 00:00:29,951 as it is subjected to different air pressures as it goes up and down. 7 00:00:29,951 --> 00:00:30,292 8 00:00:30,292 --> 00:00:30,633 9 00:00:30,633 --> 00:00:30,806