A rocket (from Italian: “rocchetto”) is a missile, spacecraft, aircraft, or other vehicles that obtains thrust from a rocket engine. There are many parts that make up a rocket. For design and analysis, engineers group parts which have the same function into systems. There are four major systems in a full-scale rocket; the structural system, the payload system, the guidance system, and the propulsion system.
The payload system of a rocket depends on the rocket’s mission. The earliest payloads on rockets were fireworks for celebrating holidays. Following World War II, many countries developed guided ballistic missiles armed with nuclear warheads for payloads. The same rockets were modified to launch satellites with a wide range of missions; communications, weather monitoring, spying, planetary exploration, and observatories, like the Hubble Space Telescope. Special rockets were developed to launch people into earth orbit and onto the surface of the Moon.
The guidance system of a rocket may include very sophisticated sensors, on-board computers, radars, and communication equipment to maneuver the rocket in flight. Many different methods have been developed to control rockets in flight. Modern rockets typically rotate the nozzle to maneuver the rocket. The guidance system must also provide some level of stability so that the rocket does not tumble in flight.
As you can see on the figure, most of a full-scale rocket is a propulsion system. There are two main classes of propulsion systems, liquid rocket engines, and solid rocket engines.
The various rocket parts described above have been grouped by function into a structure, payload, guidance, and propulsion systems. There are other possible groupings. For the purpose of weight determination and flight performance, engineers often group the payload, structure, propulsion structure (nozzle, pumps, tanks, etc.), and guidance into a single empty weight parameter. The remaining propellant weight then becomes the only factor that changes with time when determining rocket performance.
Source
Benson, Tom. 2014. Rocket Parts. https://www.grc.nasa.gov/www/k-12/rocket/rockpart.html (accessed on the 18th February, 2021).
