Solid and liquid rocket engines

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Missiles as a type of weaponry have existed for a very long time. The pioneers in this matter were the Chinese, as mentioned in the hymn of the Celestial Empire at the beginning of the 19th century. "Red glare of rockets" - that's how it is sung in it. They were charged with gunpowder, invented, as you know, in the same China. But in order for the “red highlights” to shine, and fiery arrows to fall on the heads of the enemies, rocket engines were needed, albeit the simplest ones. Everyone knows that gunpowder explodes, and flight requires intense combustion with directed gas release. So the composition of the fuel had to be changed. While conventional explosives are 75% nitrate, 15% carbon, and 10% sulfur, rocket engines are 72% nitrate, 24% carbon, and 4% sulfur.

Modern solid-propellant rockets and boosters use more complex mixtures as fuel, but the principle remains the same, ancient Chinese. His merits are undeniable. These are simplicity, reliability, high speed of initiation, relative cheapness and ease of use. In order for the projectile to start, it is enough to ignite the solid combustible mixture, provide air flow - and that's it, it flew.

However, there issuch a proven and reliable technology has its drawbacks. Firstly, having initiated the combustion of fuel, it is no longer possible to stop it, as well as to change the combustion mode. Secondly, oxygen is needed, and in conditions of rarefied or airless space it is not. Thirdly, burning still proceeds too quickly.

The solution that scientists in many countries have been looking for for many years has finally been found. Dr. Robert Goddard tested the first liquid propellant rocket engine in 1926. As a fuel, he used gasoline mixed with liquid oxygen. In order for the system to operate reliably for at least two and a half seconds, Goddard had to solve a number of technical problems related to the pumping of the reagents, the cooling system and the steering mechanisms.

The principle on which all liquid rocket engines are built is extremely simple. There are two tanks inside the case. From one of them, through the mixing head, the oxidizer is fed into the decomposition chamber, where, in the presence of a catalyst, the fuel coming from the second tank passes into a gaseous state. A combustion reaction occurs, the hot gas first passes through the narrowing subsonic zone of the nozzle, and then the expanding supersonic zone, where fuel is also supplied. In reality, everything is much more complicated, the nozzle requires cooling, and the feed modes require a high degree of stability. Modern rocket engines can be powered by hydrogen, the oxidizer is oxygen. This mixture is extremely explosive, and the slightest violation of the operation of any systemleads to an accident or disaster. Fuel components can also be other substances that are no less dangerous:

- kerosene and liquid oxygen - these were used in the first phase of the Saturn V launch vehicle program in the Apollo program;

- alcohol and liquid oxygen - were used in German V2 rockets and Soviet carriers "Vostok";

- nitrogen tetroxide - monomethyl - hydrazine - used in Cassini engines.

Despite the complexity of the design, liquid rocket engines are the main means of delivering space cargo. They are also used in intercontinental ballistic missiles. Their modes of operation are amenable to precise regulation, modern technologies make it possible to automate the processes occurring in their units and assemblies.

However, solid-propellant rocket engines have not lost their importance either. They are used in space technology as auxiliary. Their importance is great in braking and rescue modules.