free-fall rocket core sampler

例句：

1. 1. The astronaut was free-falling through space when he received the distress signal.
   宇航员在太空中自由落体时收到了求救信号。
2. 2. The plane was free-falling towards the ground when it suddenly lost altitude.
   飞机在向地面坠落时突然失去了高度。
3. 3. The ball swung free-falling in the air before coming to a stop.
   球在空中自由落下，然后停了下来。