A lighter-than-air craft. A hot-air balloon is an aerostat.
The science of lighter-than-air flight.
Above ground level
Type of balloon that uses ammonia as its lifting agent instead of helium, hydrogen or coal gas. Becoming very popular in 1990's. Much less costly than flying other gasbags. Has approximately .5 lifting power of helium. Popularized by Tim Cole and Dennis Brown of Colorado. Ammonia gas is readily available in agricultural areas and smells a bit whiffy.
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