The Goodyear blimp is no small feat. At 50 feet in diameter and 192 feet in length, Goodyear's Spirit of Innovation blimp, tail number N2A, houses some 200,000 cubic feet of helium, making the blimp itself a repository of a small fortune of the natural resource. Although the blimp weighs over 10,000 pounds empty, the addition of the lighter than air helium reduces the blimp to weighing only a few hundred pounds. In order to raise and lower the blimp, large rubber bladders of air are inflated or deflated inside the blimp. This action changes the density of the blimp relative to the surrounding air, making the blimp more or less buoyant.