As early as next week, the Pentagon plans to lob a missile at a satellite falling toward Earth, in an unprecedented effort to keep the satellite's toxic fuel from inflicting public injury or death, federal officials said Thursday. The United States has never shot down a spacecraft with a missile, said Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff. The military is not destroying the satellite to keep classified information from falling into the wrong hands, Cartwright and other officials said. Downing the spacecraft is also not a way to test an anti-satellite missile, they said. "This is all about trying to reduce danger to human beings," said James Jeffrey, deputy national security adviser. However, satellites carrying the same type of toxic fuel fall to Earth all the time, said Jim Lewis of the Center for Strategic and International Studies, a Washington think tank. Also, he added, no one has ever been hurt by falling satellite parts, mostly because so much of the Earth's surface is water or thinly populated. "The risk of this is very low, and that leads to the question, why bother?" Lewis said. "This isn't going to popular" with other nations. When China shot down a satellite in a 2007 test, it was widely condemned by other nations and left a wide swath of space debris that will endanger satellites and human spacecraft for years. The U.S. National Reconnaissance Office launched the targeted satellite in December 2006, Cartwright said. It reached the proper orbit, but ground controllers lost contact with it. It is now slowly falling out of orbit. The satellite's cost and exact purpose are classified. Eventually, pieces of it will strike the Earth, though where they'd hit and how big they'd be are impossible to predict, said Graham Candler, an aerospace engineering professor at the University of Minnesota. Among the pieces that could survive the trip through the Earth's atmosphere is a 3-foot-wide spherical tank containing 1,000 pounds of hydrazine, a toxic fuel used to maneuver spacecraft, including the space shuttle. Hydrazine, Cartwright said, could spread over an area the size of two football fields and anyone caught in it could suffer lung damage and possibly die. Three Navy ships will be stationed in the northern Pacific Ocean to shoot down the satellite sometime during a seven-to-eight-day window that will open early next week. A missile equipped with target-seeking sensors and explosives will aim for the tank, in the hopes of venting it before the satellite's pieces reach Earth. The Standard Missile-3 the Pentagon will use is reliable and successfully hit an incoming ballistic missile during a 2007 test, said Steven Schneider of Purdue University. "It's almost certainly possible to do," said Ivan Oelrich of the Federation of American Scientists. "Whether it is a good idea or not is another thing entirely." Enlarge By Heesoon Yim, AP Joint Chiefs Vice Chairman Gen. James Cartwright, center, is flanked by deputy national security adviser James Jeffrey, left, and NASA Administrator Michael Griffin during a news conference at the Pentagon on Thursday. Conversation guidelines: USA TODAY welcomes your thoughts, stories and information related to this article. Please stay on topic and be respectful of others. Keep the conversation appropriate for interested readers across the map.