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Hydrogen and helium are the most commonly used lift gases. Although helium is twice as heavy as (diatomic) hydrogen, they are both significantly lighter than air. The lifting power in air of hydrogen and helium can be calculated using the theory of buoyancy as follows: Thus helium is almost twice as dense as hydrogen.
The hull is internally divided by diaphragms into a total of six main compartments with additional sub-divisions; these divisions can be sealed in the event of emergencies, such as battle damage being sustained, allowing for the majority of the airship's helium, and thereby lift capacity, to be retained. [20]
The hybrid airship combines the airship's aerostatic lift, from a lighter-than-air gas such as helium, with the heavier-than-air craft's dynamic lift from movement through the air. Such a hybrid craft is still heavier than air, which makes it similar in some ways to a conventional aircraft.
The Germans had extensive experience with hydrogen as a lifting gas. Accidental hydrogen fires had never occurred on civilian Zeppelins, so the switch from helium to hydrogen did not cause much concern. Hydrogen also increased lift by about 8%. After the Hindenburg disaster Eckener vowed to never use hydrogen again in a passenger airship.
Using the molar volume, the mass of 1 liter of helium (at 1 atmospheres of pressure) is found to be 0.178 g. If helium is used instead of vacuum, the lifting power of every litre is reduced by 0.178 g, so the effective lift is reduced by 13.90625%. A 1-litre volume of hydrogen has a mass of 0.090 g, reducing the effective lift by 7.03125%.
Based on specific lift (lifting force per unit volume of gas), the greatest static lift is provided by hydrogen (11.15 N/m 3 or 71 lb f /1000 cu ft) with helium (10.37 N/m 3 or 66 lb f /1000 cu ft) a close second. [174] In addition to static lift, an airship can obtain a certain amount of dynamic lift from its engines.
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Molar heat capacity: 20.78 J/(mol·K) [3] ... During World War II, the demand increased for helium for lifting gas and for shielded arc welding.