The space launch industry is getting a lot of press in recent years due to rapid advances in rocketry technologies and achievements. Most notably, SpaceX’s propulsive landings of their boosters have been very popular. These events get press not because they’re especially relevant to the daily lives of the everyday citizen, but because they are awe-inspiring. The amount of complexity and ingenuity that is behind these incredible events is beyond the scope of imagination.
However, not all rockets are that complex. There are a wide range of rockets of different sizes and shapes with different applications. Many other launch vehicles (rockets) do not feature propulsive landing or even reusability, vastly reducing the amount of complexity in the system. Going further down the scale, we find rockets that do not fully achieve orbit, but simply carry scientific equipment to the upper atmosphere or space for a short period of time. Once you reach consumer-level hobbyist rockets, certain aspects such as payloads, wireless communications, and navigation are not even necessarily included. In fact, you can buy a hobby rocket kit for as little as twenty dollars* that consists of less than 15 parts!
Fundamentally, all a rocket needs to be called a rocket is a pointy body and a rocket engine/motor that launches it up. At the most basic level, this motor can simply be a homemade concoction of sugar and Potassium Nitrate (bought from a home improvement store or a pharmacy) that is stuffed into a capped PVC pipe. More commercially available rocket motors may consist of gunpowder wrapped in a paper casing, such as this one made by Estes Rockets:
via Apogee Rockets
When these engines burn out, they usually also contain what is called an ejection charge, which creates a small, controlled explosion at the top end of the motor which would eject the nosecone of the rocket and deploy the parachute.
Rocket hobbyists often like to know how fast and high their rocket went, so a more advanced hobby rocket would contain avionics. Avionics simply refers to all electronic components of a rocket. In this case, the avionics would consist of a battery connected to an altimeter which measures the rocket’s altitude over time.
High-powered hobbyist rockets that reach higher altitudes are under stricter regulation by the FAA because they can interfere with aircraft in the sky. These larger, more complex rockets may contain multiple motors arranged in multiple stages. They may also contain more advanced avionics, such as GPS-tracking technology and computer-activated parachute deployment at a specific altitude.
Even higher-flying rockets such as sounding rockets are the aforementioned class of rockets that often carry scientific equipment into space. These rockets now contain a payload (the scientific equipment) that the rocket needs to be designed around. One of these design requirements is likely a target altitude that the equipment must reach to obtain useful scientific data. These powerful rockets often need more advanced rocket motors than the standard solid rocket motors of the hobbyist world. More powerful rocket engines often use liquid fuels such as hydrazine, kerosene, or liquid methane. While using liquid rocket fuels massively increases complexity of the rocket motor, it allows for more precise control of thrust, as well as the ability to completely stop and restart the motor when desired.
sounding rocket via NASA
Last, but not least, we have reached where we began: orbital launch vehicles. These rockets differ from all the aforementioned smaller rockets not only in that their power, but also their precision. Not only does an orbital launch vehicle need to reach the speeds necessary to achieve orbit, it also needs to place the satellite payload in the specific orbit that the client has ordered. All of this needs to be achieved under the intense stresses experienced by accelerating a three million pound rocket to 32 times the speed of sound**.
Depending on how you look at it, rocketry can be dead simple or the most complex thing in the world. However, they all share the same underlying characteristics and structure.
*ten dollar rocket with ten dollar motor
**specifications of the SpaceX Falcon Heavy