| Dennisbab 留言内容：SpaceX Polaris Dawn crew returns home after history-making mission
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SpaceX’s Polaris Dawn crew is home, capping off a five-day mission to orbit — which included the world’s first commercial spacewalk — by splashing down in the Gulf of Mexico.
The Crew Dragon capsule carrying four astronauts landed off the coast of Dry Tortugas, Florida, at 3:37 a.m. ET Sunday.
The Polaris Dawn mission made history as it reached a higher altitude than any human has traveled in five decades. A spacewalk conducted early Thursday morning also marked the first time such an endeavor has been completed by a privately funded and operated mission.
But returning to Earth is among the most dangerous stretches of any space mission.
To safely reach home, the Crew Dragon capsule carried out what’s called a “de-orbit burn,” orienting itself as it prepared to slice through the thickest part of Earth’s atmosphere.
The spacecraft then reached extremely hot temperatures — up to 3,500 degrees Fahrenheit (1,900 degrees Celsius) — because of the pressure and friction caused by hitting the air while still traveling around 17,000 miles per hour (27,000 kilometers per hour). The crew, however, should have remained at comfortable temperatures, protected by the Crew Dragon’s heat shield, which is located on the bottom of the 13-foot-wide (4-meter-wide) capsule.
Dragging against the air began to slow the vehicle down before the Crew Dragon deployed parachutes that further decelerated its descent. |
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