Which of the following vehicles is used where the flight time is long?

A)
Solid propulsion system
B)
Liquid propulsion system
C)
Hybrid propulsion system
D)
Electrical propulsion unit

Correct Answer :   Electrical propulsion unit


Explanation : Electrical propulsion units have low thrust values. This means that it is a less viable option during take-offs and landing. Because of its very low acceleration potential, it takes a long period of time to accelerate and hence is suited for missions that are time intensive.