The World’s Largest Vacuum Chamber

 The 6,400-acre Plum Brook Field Station complex near Sandusky, Ohio, houses five large test facilities operated by NASA to test various aspects of space flight. Most of these were built decades ago when the country's space program was of national importance. But now, these million-dollar facilities have fallen into disuse and some have fallen into such disrepair that they will require millions of dollars to repair. Of the five facilities still in place, four have not been used in recent times. Two are to be demolished, one is not fully functional and one has never been used. Only one large vacuum chamber, called the Space Power Facility, is in use with a long line of customers booked until at least 2021. One of its most recent customers was SpaceX.

The Space Power Facility (SPF) is the world's largest vacuum chamber measuring 30 meters in height and 37 meters in width. It is used to simulate the conditions that exist in outer space so that rocket hardware can be tested before it is actually sent into space. It pumps out about 30 tons of air present in the chamber until only 20 milligrams remains. It takes about eight hours to reach this level. Inside, a series of quartz heat lamps simulate solar radiation and a 400-kilowatt arc lamp simulates the solar spectrum. The cryogenic cooling shroud brings the temperature down to minus one hundred and sixty degrees centigrade.

The facility was built in 1969, originally for nuclear-electric power studies under vacuum conditions, but was later adopted for testing spacecraft propulsion systems. The entire chamber is made of aluminium, which is not the toughest metal to withstand the enormous pressure generated when pumping air. The strange choice of metal is due to the fact that the chamber was originally designed for testing nuclear devices and aluminum has radiation shielding properties. To strengthen the structure, the entire aluminum chamber is covered with concrete which provides additional radiation shielding.

The SPF is not the most extreme vacuum chamber but it is certainly the largest. Some vacuum chambers can achieve ultra vacuum conditions where air pressure is reduced to 100 nanopascals, or about 2,500 times less than the strongest vacuum achieved by SPF, but those vacuum chambers are generally small, and Used for things like X-rays. Spectroscopy and gravitational wave detectors. The SPF, on the other hand, is big enough to swallow a spacecraft. The airbag landing system for Mars Pathfinder was tested inside this vacuum chamber, and the Mars Exploration Rovers, Spirit and Opportunity, were stress-tested here under simulated Mars atmospheric conditions. In 2013, SpaceX, the most exciting private space venture, used SPF's services to test its payload fairing – the nose cone that protects the spacecraft from pressure and heat during launch through the atmosphere.

In 2013, the BBC conducted a physical demonstration of one of the most famous thought experiments inside SPF. He took a bowling ball and a bunch of feathers, lifted it to the roof of the chamber through a crane and dropped it down at the same time. Without air resistance to slow the wings, both objects fell at the same rate and touched the chamber floor at exactly the same moment. Here is the video of the experiment.