Page 10 - Curriculum Visions Dynamic Book

Nose cone
Capsule (payload)
Launcher
Going into space
 The payload is a tiny front-end compartment of the space vehicle (Apollo 11).
Launcher design
Launchers are always built in detachable stages because it is important to lose as much unnecessary weight as quickly as possible during the journey. If a single stage was used, the tanks would be partly empty for much of the journey, adding the weight of the casing for no gain.
The launcher and its payload weigh most when they have a full fuel tank, and most fuel is used up simply getting the assembly off the ground and through the lower atmosphere. That is why the tanks are the biggest part of any spacecraft, and why some of them quickly become empty and are dropped off within a couple of minutes of takeoff.
Propulsion systems
A propulsion system can be considered the power unit or engine of the rocket. It burns the propellant or fuel. But launcher propulsion systems are not like the engines we use in cars.
Rocket propulsion systems are special forms of the jet engine. The main difference between spacecraft and aircraft jet engines is that normal jet engines use the air of the atmosphere to burn their fuel, so they do not have to carry around a supply of oxygen in a large tank. However, using air does have a big disadvantage: Burning needs oxygen, and the amount of oxygen that can be used in burning fuel depends on how much oxygen is in the air. That limits the thrust the engine can provide. More thrust can be achieved by using
a more concentrated supply of energy, even on the ground. However, launchers have to operate in space, where there is no oxygen at all, and so they have to carry their oxygen supply with them in the form of huge tanks of liquefied oxygen gas.
Propulsion systems can look crude, but they are not. They do have to be as simple as possible, so that they are reliable. They also have to be able to withstand enormous forces and the flow of searingly hot, corrosive substances.
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