Do rockets on lunar missions, like Chandrayaan, take off at escape velocity?
Answer
Chandrayaan wants to reach the Moon, not simply escape Earth and fly off into deep space. So, the answer is no—not directly.
Reaching Earth's escape velocity means having enough speed and energy to leave Earth on an unbound trajectory. But a lunar spacecraft isn't trying to escape Earth completely. It is trying to leave Earth orbit and enter a trajectory that intersects the Moon's orbit.
The Moon itself orbits Earth, so even when Chandrayaan reaches the Moon, it is still within Earth's gravitational influence. Earth's gravity doesn't suddenly stop at the Moon. The spacecraft is still being pulled by Earth, while the Moon's gravity also acts on it.
That's why a lunar mission is more accurately described as leaving Earth orbit, rather than escaping Earth's gravity altogether.
Chandrayaan is first placed into Earth orbit. It then performs additional engine burns to raise its orbit and eventually receives enough energy in a trans-lunar injection manoeuvre to head toward the Moon.
In brief: Chandrayaan does not take off at Earth's escape velocity. It is launched into Earth orbit and then given additional energy to follow a carefully calculated path to the Moon.