But for all his observations, the design of his birdlike flying machines _ as well as that of his ingenious corkscrew-shaped helicopter _ missed one small but crucial detail : The curved shape of a wing's cross-section, which is what we now know is the source of its lifting power.
42.
:: : : As stated above, helium has about 90 % of the lifting power of hydrogen, so if lift using hydrogen exceeds the weight of the vehicle by more then 10 %, it should work, although your controls might be sluggish . talk ) 13 : 02, 27 May 2009 ( UTC)
43.
It is called a De Rozier, named for an aviation pioneer who built the first such balloon in Paris in 1789 . It uses a combination of helium ( to provide long-duration lifting power ) and hot air ( to compensate for helium's loss of lifting power at night, when cold temperatures would cause the gas to contract ).
44.
It is called a De Rozier, named for an aviation pioneer who built the first such balloon in Paris in 1789 . It uses a combination of helium ( to provide long-duration lifting power ) and hot air ( to compensate for helium's loss of lifting power at night, when cold temperatures would cause the gas to contract ).
