A mission to Moon is nothing comparable to travelling to your destination in a train or hopping on flights. It is all about Rocket Science!
If you see a rocket lift off you will realise the dimensions of the space endeavour. The magnificent rocket standing on the space pad, the smoke it ejects on ignition, the trajectory it takes in the sky leaving behind a trail of smoke is a sight to behold. The reason of the magnanimity is the nature of space. The Moon is at a distance of 300000 kms. Mars is at a distance of 75 to 100 million kms depending upon its trajectory at the moment of time it is being cited. The Earth has an atmosphere. The Moon does not have any and Mars has a very week one. The atmosphere of the Earth resists the motion of a rocket when it pierces it. The troposphere lies up to a height of 23 kms in which the planes fly. The stratosphere is upto 50 kms. Beyond the coolest mesosphere of 69 kms lies the Karmen Line beyond which begins again the hot thermosphere and ionosphere upto a distance of 350 kms where-in lies the low earth orbit where gravity seizes to exist. If a rocket has to move beyond the troposphere it requires an amazing amount of thrust and a technology to take you safely beyond these layers and into the inert space where resistance is negligible and hence the rocket science.
A rocket is thus designed to take you to space. First it should be equipped with fuel to take you beyond the resistance of all those atmospheric layers, then it needs command and service modules to travel to the moon or interplanetary space. The intricacy of the command modules is they are fitted with ascent vehicles required to return back and dock with service modules which have the fuel to get you back to Earth.
A mission to moon like the Apollo’s had an assembly of a huge stage1 where it had a big amount of fuel to create a thrust to get beyond the atmosphere and shed off the heat shields and jettison the entire stage into space. Next was jettisoning the Launch Escape Tower which was at the top of the rocket kept as an escape just in case the lift-off misfired. It was just above the command module where the astronauts stood. The second stage carried the mission to a hundred nautical miles and was cut off and separated. Stage 3 orbited around the Earth and took the flight-path in the trans-lunar gulf. The CSM(Command and Service Module) then was maneoured to the Moon and returned back to Earth. The CSM orbited the Moon and ejected the LM (Lunar Module) onto the Moon which had an in built Ascent Vehicle to take off from the Moon and dock with the service module. Finally at the Earth orbit the service module would be jettisoned and only the command module with a powerful heat shield to pierce the Earths atmosphere and parachute down and land in the atlantic ocean to be rescued by marines back to NASA quarantines where they would be rehabilitated and studied for effects of space on humans.
In the intermediate of this space flight and landing on Moon were carried out systematically at various stages system status checkouts, computer updates, trajectory confirmation, deployment of high gain antenna , navigation sightings, mid-course corrections, eat and sleep periods of the astronauts, data transmission and several other activities aiding the smooth completion of the mission.
Rockets of the modern age want to use the rockets multiple times to reduce cost. They have carried out accurate manoeuvres to drive these rockets back to the launch pads once satellites or command modules are released in space. They are also developing pay-load techniques with multiple rocket releases to fuel the space-crafts in space so that take offs and space travel are better facilitated. Scientists are developing better fuels for take offs and for achieving faster speeds so that interplanetary travel is eased.
