A rocket may appear like a single large structure on a launchpad, but it actually consists of millions of unique smaller parts. These parts can be grouped into one of the four major systems that make up a rocket.

A Rocket Consists Of Four Primary Parts:

  1. The Structural System
  2. The Propulsion System
  3. The Guidance System
  4. The Payload System

All four systems perform an equally important role in the functioning of an orbital launch vehicle. By taking a closer look at each component, the specific makeup and purpose each one serves will quickly become evident:

The Structural System Of A Rocket

A rocket’s structural system is essentially the frame and shell of a rocket, like the fuselage of an aircraft or the hull of a ship. Unlike an airplane, though. a rocket’s structure contains all other systems, including the guidance, payload, and propulsion systems.

The materials used in the construction of a rocket need to be both strong enough to hold the vehicle together and withstand all the dynamic forces put on it during launch and ascent but also be light enough to assist it in escaping Earth’s gravity and achieving orbit.

The 4 Main Parts Of A Rocket
Illustration of the four systems under which all parts of a rocket are categorized.

As a result, strong, lightweight materials like titanium, aluminum, and carbon composites are typically used to build the most critical parts of a rocket’s structure.

During construction, support structures called stringers are used, which run the entire length of the rocket (or rocket section). At certain intersections, the stringers are connected to circular frames (or hoops) that cover the circumference of the vehicle.

Next, the rocket’s shell (or skin) is attached to the frame and coated with different materials, including a thermal coating to protect the vehicle from the extreme heat generated by air resistance while also protecting the cold cryogenic fuels and oxidizers inside the vehicle.

Together, the stringers, hoops, as well as the rocket’s shell make up the basic structure of a launch vehicle, which is the shape you see on a launchpad.

Spacecraft used to return to Earth need even more protection since the heat generated during re-entry through the atmosphere is high enough to melt metal. Tiles made from silica (ceramic) fibers are used as heat shields to protect the vehicle during this critical process.

(Although a modern orbital rocket is typically built and integrated at an assembly facility close to its launch complex, its various parts are usually manufactured elsewhere and in multiple locations. Learn more about a rocket’s manufacturing process in this article.)

It has to be noted that sometimes there is an overlap between the different systems of an orbital launch vehicle, and the structural system is no exception. Payload fairings are one such example.

The payload fairing of a rocket is considered part of the structural system as it forms part of the nose section of the vehicle’s outer shell. But its primary role is to protect the payload & it is integrated with the payload during assembly, also making it part of the payload system.

(Learn more about rocket payload fairings, what they are, and the role they play in an orbital launch vehicle in this article.)

The Propulsion System Of A Rocket

A rocket’s propulsion system provides the thrust that moves the launch vehicle through the atmosphere into orbit during launch and allows it to maneuver in the vacuum of space. The vast majority of a rocket’s mass and internal space comprise of the propulsion system.

Rocket Propulsion System
The propulsion system of a typical liquid-propellent launch vehicle.

It primarily consists of the rocket engine (either a liquid-propellant engine or solid rocket booster, or a combination of both), fuel and oxidizer tanks, pumps, and the rocket nozzle.

A modern rocket uses a process called rocket staging to discard sections of the propulsion system that used up its fuel and is no longer needed to reduce the weight of the vehicle and improve aerodynamics during a launch.

There are primarily two types of rocket engines that are used by modern launch vehicles: Liquid-propellant rocket engines and solid-propellant propellant engines (or SRBs). Either one or a combination of these engines can be used, depending on mission requirements.

(Learn more about what precisely a liquid-propellant and solid-propellant rocket engine are and how each one functions in this article.)

The Guidance System Of A Rocket

A rocket’s guidance system fulfills the crucial role of guiding its movement and determining the direction it travels in. It is responsible for keeping a rocket upright during launch, controlling its trajectory through the atmosphere, and determining its movement in space.

Saturn 5 Guidance System
The giant guidance system of the Saturn V rocket that was used during the Apollo Missions.

Primary movements like pitch, yaw, and roll are all controlled by the guidance system. It also controls a rocket’s thrust, including throttling down before the vehicle experiences maximum dynamic pressure (max q), shutting it down, and restarting it at the appropriate time.

It consists of a series of sensors, onboard computers, radars, and other navigational equipment that allows it to detect the rocket’s orientation and direction and make the necessary adjustments to keep the vehicle on its predetermined heading.

Although it doesn’t always receive the same amount of attention or emphasis as the propulsion or structural system, the guidance system is just as critical for a rocket’s operation, without which it will be unable to function properly.

The Payload System Of A Rocket

A rocket’s payload refers to any form of cargo/object/individual(s) a launch vehicle needs to deliver or transport into space. Although not crucial for a rocket’s operation, it is the primary reason any rocket is sent into orbit and beyond.

The type of payload any rocket carries depends entirely on the mission of any space launch. If the purpose is to put a satellite into orbit, the satellite (enclosed in a purposely-built fairing) will serve as the payload.

Crew Dragon Spacecraft
The Crew Dragon Spacecraft, which formed part of the payload of a Falcon 9 rocket, docks with the International Space Station.

Crewed missions will require a spacecraft for carrying humans (like the command module used during the Apollo missions and the Crew Dragon used by SpaceX to send astronauts to the International Space Station). The spacecraft and crew are the payloads in this case.

Rockets are also used to send probes into space to explore the solar system, like the Voyager spacecraft and, more recently, the Cassini probe that studied Saturn in great detail. Scientific equipment like the Hubble Space Telescope can also serve as payloads for rockets.

While discussing a rocket’s propulsion system, it was mentioned that a combination of liquid-propellent engines and solid rocket boosters are sometimes used on a single launch vehicle during a launch. This configuration is often a result of payload specifications.

When a certain payload is too heavy for a specific launch vehicle or it needs to be placed into a higher orbit, it often requires additional thrust to enable a rocket to lift the extra weight into space and place the payload into the required orbit.

A relatively simple and cost-effective way of accomplishing this is to add multiple solid rocket boosters (SRBs) to a liquid-propellent rocket. In recent years rockets like the United Launch Alliance’s Delta IV and Atlas V rockets frequently used SRBs to provide added thrust.

During the Space Shuttle Program in the late 20th and early 21st Century, two solid rocket boosters formed a crucial part of every launch. The weight of the orbiter and its payload were simply too much to reach orbit without the added thrust of the two largest SRBs ever used.

(All the parts or systems of an orbital rocket help to put a launch vehicle in a type of orbit around the Earth, where it stays or travels further into the Solar System. Learn more about the different types of orbits spacecraft/satellites follow around the Earth in this article.)

Conclusion

Rockets contain literally millions of parts, with the Space Shuttle having approximately 2½ million moving parts, while the Saturn V rocket used during the Apollo missions had more than 3 million moving parts.

As this article illustrated, a launch vehicle’s parts or components can be categorized into four primary systems:

  1. The Structural System
  2. The Propulsion System
  3. The Guidance System
  4. The Payload System

All four systems play an equally important role in the functioning of a launch vehicle, and this article highlighted the makeup and function of each system on an orbital launch vehicle.

This article was originally published on headedforspace.com. If it is now published on any other site, it was done without permission from the copyright owner.

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