The "Helios" UAV of the United States have ____ propellers.
查看答案
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
The thrust of solid rocket engine can be controlled by ____.
A. Control valve
B. Secondary injection technic
C. Different design of grain shape
D. Vectoring nozzle
微信支付 
支付宝支付