(The 2.2 Second Drop Tower). Much of the operating cost of a drop tower is due to the need for evacuation of the drop tube, to eliminate the effect of aerodynamic drag. Alternatively the experiment is placed inside an outer box (the drag shield) for which, due to its weight, during its fall the reduction of acceleration due to air drag is less. Historical uses Though the story may be apocryphal, Galileo is popularly thought to have used the Leaning Tower of Pisa as a drop tower to demonstrate that falling bodies accelerate at the same constant rate regardless of their mass. Drop towers called shot towers were once useful for making lead shot. A short period of weightlessness allows molten lead to solidify into a quasi-perfect sphere by the time it reaches the floor of the tower. List of drop towers The vacuum-dynamic stand in Academician V.P.Makeyev State Rocket Centre NASA Glenn Research Center 2.2 Second Drop Tower NASA Glenn Research Center Zero-G Research Facility Micro-Gravity Laboratory of Japan (MGLAB) (Closed June 2010) HASTIC 50m Drop Tower, Sapporo Fallturm Bremen Applied Dynamics Laboratories drop tower for spinning spacecraft Experimental drop tube of the metallurgy department of Grenoble NASA Marshall Space Flight Center Drop Tube Facility is currently mothballed Dryden Drop Tower, Portland State University, Maseeh College of Engineering and Computer Science National Microgravity Laboratory (China) The pagoda at the Royal Botanic Gardens, Kew was used during the Second World War as a drop tower for testing bomb designs. Queensland University of Technology drop tower, Brisbane (Closed 2014) See also Glenn Research Center Marshall Space Flight Center Magnetic levitation Microgravity Environment Shot tower Weightlessness References Laboratory equipment Towers Weightlessness