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【单选题】
The injection point of a spacecraft refers to ____.
A.
The termination point of the thrust of the second-stage rocket engine
B.
The initial position of the spacecraft into orbit
C.
Apogee
D.
Perigee
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参考答案：
参考解析：
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举一反三
【多选题】The launch orbits of spacecraft include: ____.
A.
Direct orbit injection
B.
Ballistic orbit injection
C.
Sliding orbit injection
D.
Transition orbit injection
【单选题】关于应力集中，一下哪个是错误的？
A.
因杆件载荷的改变而引起应力增加的现象称为应力集中
B.
对塑性材料,在应力集中的地方,当某点最大应力达到屈服极限时,将发生塑性变形,应力不再增加
C.
应力集丰对塑性粉料的强度影响很小
D.
脆性材料对应力集中敏感性甚强
【单选题】The black barrier area is located in ____ of the spacecraft’s return orbit.
A.
Deorbit stage
B.
Transition stage
C.
Re-entry stage
D.
Landing stage