The compression of air is finished in the ____ of ramjet.
A. Intake ducts
B. Compressor
C. Turbines
D. Nozzle
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The "Helios" UAV of the United States have ____ propellers.
A. 10
B. 12
C. 14
D. 16
The thrust-to-weight ratio of rocket engines could reaches ____.
A. 30-40
B. 50-70
C. 80-120
D. 100-150
____ is a kind of the chemical energy rocket engines.
A. Solar energy rocket engine
B. Electric energy rocket engine
C. Solid-liquid hybrid rocket engine
D. Nuclear energy rocket engine
The most important part to control the thrust of the liquid rocket engine is the ____.
A. Jet nozzle
B. Propellant feeding system
C. Propellant pump
D. Flow control valve
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