Rocket engines! How do they work?
Hi there! I´m back for another post. Today we are talking about rocket engines. If you think they are boring, you should be sorry because the only reason you can play that stupid game called Pokémon Go is because of rockets!
Rocket engines are a type of jet engine that expel very hot gases out of an exhaust. These hot gases are created in the combustion chamber. In order for a rocket motor to achieve thrust (if done properly a lot) there is a very important law that you must keep in mind; Newtons third law of motion. It states that "for every action(force) in nature, ther is an equal and opposite reaction. What does this mean for current rocket scientists or soon to be rocket scientists like yourself (I hope)? That if you want more power(or power at all) you can do two things with your rocket. you either increase the mass of the stuff you throw out the back of the engine, or you increase its velocity.
These motors are the most powerful type of jet engine, as well as the least efficient. The reason is that they don´t use the oxygen provided by the atmosphere, so they must carry their own oxidizer(all reactions like these need oxygen in some form). The chemicals they use are very cold, very hard to work with and are difficult to properly control and mix in a combustion chamber in order to obtain the best fuel/oxidizer ratio, thus less power and efficiency. This is made even worse when you make a bigger engine, but since these engines are obsolete in most parts of the atmosphere and are only useful at getting stuff to space and through it, they are usually pretty big on the first couple of stages of a rocket. Space probes use rockets too, but they are a pain in the arse for missions: not much power, heavy, complicated(more stuff to go wrong), not usable for long(propellants run out, so you can´t do much) and the fuel can evaporate out of the fuel tanks! Space probes try to use alternatives to rockets, like ion thrusters (I will talk about them in the future). So these engines have a limited range of practical usability.
VARIANTS
There are three main variants of rocket motors(there are others though), and the only difference are the chemicals they use:
1. Solid fueled rockets: their propellants are in a solid form, usually in a powder mixture. These engines are cheaper and much simpler than their counterparts, but have a few down sides:
-They can´t be throttled in real time, although you can predict how much power you need and alter the area of the propellant that is burning and can be designed into the propellant grain.
-Once turned on, they cannot be turned off, hence a big safety hazzard.
-It isn´t economically viable to reuse them, even though it can be done.
-They are only useful for lifting rockets off the launch pad, but in higher altitudes, your better off with other types of rockets.
2.Liquid fueled rockets: their propellants are in liquid form, stored in pressurized tanks. These engines are more expensive than solid fueled rockets, but have a few benefits over them:
-They can be throttled in real time, so if you want to land and reuse the first stage, these are the engines to use.
-They have better specific impulse(they are more efficient) than solid fueled rockets.
-Their performance is more consistent in varrying altitudes and environments.
-Some can be turned on and off various times.
3.Hybrid rockets: also known as hypergolic fueled rockets, usually use hypergolic propellants.
-These propellants explode on contact, so they recquire fewer moving parts.
-They are easily throttleable and easy to turn off.
-They are relatively simple, since the fuel is usually solid, and the oxidizer is liquid and stored in tanks.
There are more types of rocket motors, but these three are the most important. This is currently the best that we have to go to space, and there is still lots of work to be done if we want to have colonies on other planets.
That´s it! I hope you now understand how rockets work...uhm...hopefully. If you have any questions leave them in the comments and I will try to answer them.
-DISCLAIMER: I am only a pretend engineer, so if you find a mistake, please tell me in the comments.
Bye!
Rocket engines are a type of jet engine that expel very hot gases out of an exhaust. These hot gases are created in the combustion chamber. In order for a rocket motor to achieve thrust (if done properly a lot) there is a very important law that you must keep in mind; Newtons third law of motion. It states that "for every action(force) in nature, ther is an equal and opposite reaction. What does this mean for current rocket scientists or soon to be rocket scientists like yourself (I hope)? That if you want more power(or power at all) you can do two things with your rocket. you either increase the mass of the stuff you throw out the back of the engine, or you increase its velocity.
VARIANTS
There are three main variants of rocket motors(there are others though), and the only difference are the chemicals they use:
1. Solid fueled rockets: their propellants are in a solid form, usually in a powder mixture. These engines are cheaper and much simpler than their counterparts, but have a few down sides:
-They can´t be throttled in real time, although you can predict how much power you need and alter the area of the propellant that is burning and can be designed into the propellant grain.
-Once turned on, they cannot be turned off, hence a big safety hazzard.
-It isn´t economically viable to reuse them, even though it can be done.
-They are only useful for lifting rockets off the launch pad, but in higher altitudes, your better off with other types of rockets.
Schematic of a solid fueled rocket motor
2.Liquid fueled rockets: their propellants are in liquid form, stored in pressurized tanks. These engines are more expensive than solid fueled rockets, but have a few benefits over them:
-They can be throttled in real time, so if you want to land and reuse the first stage, these are the engines to use.
-They have better specific impulse(they are more efficient) than solid fueled rockets.
-Their performance is more consistent in varrying altitudes and environments.
-Some can be turned on and off various times.
Picture of the infamous f1 liquid fueled rocket motor being test-fired
3.Hybrid rockets: also known as hypergolic fueled rockets, usually use hypergolic propellants.
-These propellants explode on contact, so they recquire fewer moving parts.
-They are easily throttleable and easy to turn off.
-They are relatively simple, since the fuel is usually solid, and the oxidizer is liquid and stored in tanks.
Schematic of a hybrid rocket motor
That´s it! I hope you now understand how rockets work...uhm...hopefully. If you have any questions leave them in the comments and I will try to answer them.
-DISCLAIMER: I am only a pretend engineer, so if you find a mistake, please tell me in the comments.
Bye!
Comments
Post a Comment