terminated. Water from fuel combustion The most promising procedure for ballast extraction during the journey is condensation of the engines' exhaust gasses, which consist mainly of water vapour and carbon dioxide. The main factors affecting gainable water are the hydrogen content of the fuel and humidity. The necessary exhaust gas coolers for this method had repeated problems with corrosion in the early years. The first trials on the DELAG-Zeppelin LZ 13 Hansa (1912–1916) were conducted by Wilhelm Maybach. The trials were not satisfactory, resulting in the project's termination. The USS Shenandoah (ZR-1) (1923–25) was the first airship with ballast water recovered from the condensation of exhaust gas. Prominent vertical slots in the airship's hull acted as exhaust condensers. A similar system was used on her sister ship, USS Akron (ZRS-4). The German-made USS Los Angeles (ZR-3) was also fitted with exhaust gas coolers to prevent jettisoning of the costly helium. Lifting gas temperature Changes in the lifting gas temperature in relation to the surrounding air have an effect on the buoyancy balance: higher temperatures increase buoyancy; lower temperatures decrease buoyancy. Artificially changing the lifting gas temperature requires constant work as the gas is barely thermally isolated from the surrounding air. However, it was common to make use of natural differences in temperature such as thermal updrafts and clouds. Preheated lifting gas Preheated lifting gas was tested to offset the higher weight of the Zeppelin. One variation tested on the LZ 127 Graf Zeppelin was to blow heated air on the lifting gas storage cells with the aim to gain buoyancy for launch. Lifting gas density It is possible to change the density of a volume of lifting gas by compressing it with a Ballonet. Basically a balloon inside a balloon that can be pumped full of outside air from the surrounding atmosphere. See also Aerostat Blimp Loon (company) References External links Patentschrift zum Auftreibsausgleich durch Kondensation und Verdampfung von Wasserdampf (German) Airship technology Buoyancy devices