In 1892 he published his designs as "Aerostat Metallitscheski" (the all-metal dirgible aerostat). A powered, steerable aerostat is called a "dirigible". A blimp is a non-rigid aerostat. ILC is the world's largest producer of modern aerostat and airship envelopes. Nowadays a "balloon" is an unpowered aerostat and an "airship" is a powered one. An airship is a powered, free-flying aerostat that can be steered. Another system of this kind is the Tethered Aerostat Radar System. In the early morning, lightning struck an aerostat that was tethered to the vessel. The aerostat radar data is available to NORAD and U.S. Customs and Border Protection. The first modern man-lifting aerostat, made by the Montgolfier brothers, was a hot air balloon. Beginning in the late 1990s, the aerostat sites were equipped with Lockheed Martin 420K aerostats. Galatea docks the aerostat at the tower housing Central's core. The aerostat could be positioned above the vessel for surveillance. It was Lowe's intent to make a transatlantic crossing by utilizing an enormous gas-inflated aerostat. Neither the aerostat nor its pilot or companion were ever found.