發送短信 : Swept-back grid fins for transonic drag reduction

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|  __ \\    / _ \\   / ____||   / _ \\   / ____|| 
| |  \ ||  / //\ \\ / //---`'  / //\ \\ / //---`' 
| |__/ || |  ___  ||\ \\___   |  ___  ||\ \\___   
|_____//  |_||  |_|| \_____|| |_||  |_|| \_____|| 
 -----`   `-`   `-`   `----`  `-`   `-`   `----`