A huge inflatable vehicle as long as a 23-floor skyscraper is tall has become the world's largest airship in its bid to serve as a stratospheric satellite, or "stratellite," according to its developers. The 235-foot (72 m) long airship, known as the Bullet 580, has a top speed of 80 mph (129 km/h) and can serve as a high-flying sentinel that stays aloft for long periods of time. Getting the new sky behemoth inflated required six hours inside Garrett Coliseum in Montgomery, Ala. "Our airships are radically different designs that move beyond the performance limitations of traditional blimps or zeppelins...