The propellant to be burned is contained within the combustion chamber or case. The solid propellant is sometimes called grain and it contains all the chemical components needed for burning (oxidizer and fuel).
Once the propellant is ignited, it burns smoothly at a determined rate on all the internal surfaces. Initial burning take place on the internal surfaces of the hole(s) there is in the grain. As the propellant is burned, the cavity keeps growing.
The resulting hot gases flows through the nozzle to impart thrust. Once the motor is ignited, the propellant will burn till it has been consumed.
These type of engines are considered to be the most simple due to the fact there aren’t feed systems like in hybrid or liquid engines.
An example of this type of rocket engines are the ones that were used on the Space Shuttle boosters or the ones used on the Ariane 5 boosters.
Liquid propellant rocket engines use liquid propellants that are fed at high pressures from tanks into a thrust chamber. Depending on the number of liquids that are used we can distinguish between:
In the thrust chamber the propellants react to form hot gases, which are accelerated and ejected at high velocities through the nozzle, imparting momentum to the vehicle.
Some of the liquid rocket engines permit repetitive operation and can be started and shut off various times (eg. Merlin (SpaceX)). If the thrust chamber is provided with adequate cooling, it is possible to run liquid rocket engines for long periods.
The liquid propellant engines are considered to be the most complex due to the fact they require precision valves and a complex feed mechanism which includes propellant pumps, turbines, propellant pressurizing device and a complex thrust chamber.
An example of these type of rockets can be found in many of the active rockets. For example the Merlin engines used on the Falcon 9 or the Rutherford used on the Electron rocket.
This type of engines uses a stored high-pressure gas such as air, nitrogen or helium as their propellant. Due to the high pressures, this type of engines require heavy tanks. This type of engines have been used and are still used today as altitude control systems (ACS).
On this type of rocket engines we can heat the gas to improve the performance. This type of engines are the so called warm gas propellant rocket propulsion.
This type of rocket engines use a liquid and a solid propellant. For example, it can be injected a liquid oxidizing agent into a combustion chamber filled with a solid grain. Then the chemical reaction takes place and produce hot gases. This can also be done injecting liquid propellant agent into a combustion chamber filled with a solid oxidizer.
There are also combination systems that both has solid and liquid propellants. One example is a pressurized liquid propellant engine that uses a solid propellant to generate hot gases for tank pressurization.
Most of the times the gaseous and monopropellant rocket engines are used on the ACS because they can be started and shut off many times with an excellent precision.
Not agree? Send us a request!
Liquid propellant rocket engines are considered to be the most complex due to the fact they require precision valves and a complex feed mechanism which includes propellant pumps, turbines, propellant pressurizing device and a complex thrust chamber.
Not agree? Send us a request!