In everyday language, the term rocket refers to a space vehicle propelled by a high-powered jet engine. In reality, it is more accurate tu use the word launcher. The rocket
is intended to launch a load ( satellite
, manned vessel…) beyond the earth’s atmosphere.
Falcon 9, Soyuz, Ariane…all the major space-faring nations have developed their own launchers.
THE DIFFERENT COMPONENTS OF A LAUNCHER
A launcher is composed of several elements :
-> several stages, each with its own fuel and oxidizer tanks, and its rocket engine(s).
-> an equipment bay, where most of the guidance, piloting and localization systems are gathered.
-> the fairing: located at the end of the launcher, it’s purpose is to protect the payload at the beginning of the flight phase.
The payload is most often located at the top ; the cap that covers it , is aerodynamically shaped ( the nose). If it is a manned mission , the launcher also has an ejection system at the top, an escape tower, which makes it possible to evacuate and move the crew away if the first phases of flight do not go as planned.
In order to put a payload into orbit, launchers are always made up of several stages, which are fired successively ; when a stage has exhausted its fuel, it is jettisoned and the next one takes over.
On modern launchers, the first (main) stage is often flanked by boosters, intended to provide additional thrust during the first minutes of flight .
Most of the time, these are solid propellants capable of providing significant thrust at low cost.
Traditionally, launchers have three stages, or two stages with gas pedals attached to the first stage .
The last stage generally provides the most horizontal velocity to the payload. In the most sophisticated launchers, it can be turned off and on several times.
CHEMICAL PROPULSION
A launcher works on the principle of action-reaction : the rocket engine ejected matter ( gas) towards the rear, which transmits by reaction a thrust to vehicle, of equal force and opposite direction, thus towards the front.
As in the case of a gasoline engine of car, the energy comes from the combustion of a fuel with an oxidizer, which we call propellants.
A rocket engine comprises a combustion chamber, where the propellants are burned.
Unlike a conventional engine, the oxidizer is always stored in the rocket and not taken from the atmosphere, which allows the rocket to operate in a vacuum.
We generally distinguish :
-> liquid propulsion:
The oxidizer and fuel are stored in liquid form and injected into the combustion chamber.
-> solid propellant propulsion :
On ignition, the surface of the solid block burns, producing high-pressure combustion gases which are expelled through the nozzle. These solid propellants are often used today as boosters for the first stage, in addition to liquid propellant engines, providing up to 90% of the initial thrust.
The launchers are lost
after being used because their recovery raises many problems. Obviously, this represents a huge financial loss that can be counted in tens of millions.
BUT ONE DAY…….
