That's an excellent question. Strictly
speaking, there is no reason why a spacecraft must
orbit the earth before going to the moon. But in
practice, this was often done for the Apollo
missions. Apollo 11 circled the earth one and a
half times. The Apollo rockets were built in
stages, with one stage getting the rocket into
orbit, and the next stage getting it from earth
orbit to the moon. (A third stage was used to come
Technically no, it does not. But practically,
that is the best way to get the job done. In order
to leave the earth’s gravitational tug, an object
needs to attain escape velocity which from earth
is 11.2 km/s. The usual pattern is to launch into
low earth orbit at speed of 8 km/s, check all the
systems and do a burn and change the trajectory.
But this is not required per se.
A rocket ship does not have to orbit the Earth
in order to get to moon. In fact, a ship whose
destination in the Moon should not waste any time
or fuel orbiting the earth. To get to the moon, a
rocket ship must travel fast enough break free of
the Earth's orbit, or gravitational pull. This
velocity is almost 7 miles per second (over 25,000
miles per hour!) at the surface of the Earth and a
little under 4.5 miles per second (over 15,800
miles per hour!). Remember that the closer you are
to something with mass, the stronger the
gravitational pull. Thus, the farther you are from
the Earth, the smaller the escape velocity is.
While a rocket ship can try straight-shooting
to where the Moon will be, another approach has
been used called a trans-lunar injection (see a
picture here: trans-lunar
injection). This approach involves burning
some fuel to maneuver the rocket ship into an
orbit around the Earth and then burning the rest
of the fuel and escaping the Earth once the rocket
ship has positioned itself to reach the moon.
In short, a rocket ship doesn't have to orbit
the Earth to get to the Moon, but it can be more
practical to make a pit-stop above the Earth
before committing to the whole she-bang!
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