What Is a Scramjet Engine

Scramjet engines have been around for decades. These are extremely advanced air-breathing engines that work only above the speeds of Mach 5. Orbital launch vehicles must attain velocities above Mach 25 (8km/s) to leave the atmosphere and enter orbit. Considering the escalating costs of sending rockets to space, saving weight by using air breathing engines that work well at high altitudes, such as Scramjets, is an attractive proposition. To understand what is a Scramjet engine, it is important to understand jet engines and how jet propulsion works. 

Jet propulsion works by the reaction produced by the ejection of matter. Engines that employ jet propulsion often burn fuel to produce high volumes of hot and compressed gas. When the compressed gas is released through a nozzle, it creates a stream of high-velocity gas propelling the engine in the opposite direction based on Newton’s third law. 

The Main Processes in a Jet Engine

Jet engines have a complex array of turbines that compress outside air as a source of oxygen to burn jet fuel. They are made out of a compressor section followed by a combustion chamber and a turbine. The main processes in a Jet Engine are as follows: 

• The rotating compressor in the front of the engine sucks air and funnels it through narrow passages to increase pressure. 
• The highly pressurised air, which is at about 3 to 12 times the outside pressure, is fed into the combustion chamber to burn jet fuel. 
• The energy released from the jet fuel creates many hot expanding gases that run a turbine at the end. 
• The turbine, in turn, runs the compressor to keep the engine working. 
• The hot, high, pressure gases produce exit at the back of the engine and generate thrust.  

Ramjet Engines

Ramjet engines are the simplest form of a jet engine with no moving parts such as compressors and turbines. Instead, these engines use the high forward speed of aircraft to compress air and burn it in the combustion chamber. 

What Is a Scramjet Engine?

A Scramjet (supersonic-combustion ramjet) engine is an improved Ramjet engine, except that it works with air flowing at supersonic speeds. However, it is important to understand that the construction of the two engines is different. Scramjet engines are very difficult to ignite and have lofty challenges. 

Features of a Scramjet Engine 

• Scramjet engines only work at hypersonic speeds (> Mach 1). They require a boost from a rocket or an aircraft flying five times the speed of sound to start the compression process. 
• Scramjets work well at high altitudes where the atmosphere is thin and offers low drag. 
• Scramjets can be used as a booster after the rocket’s first stage is jettisoned and the second stage is ignited. Since the rocket is travelling at sufficient speeds, it is possible to operate a scramjet engine. 
• Scramjets can significantly improve the performance of launch vehicles since an upper stage propelled by a scramjet need not carry extra oxygen in the rocket. 
• Scramjet engines can be used for commercial aircraft to fly supersonically in the future. They are a viable source of propulsion at hypersonic speeds in aircraft that traverse the globe. 

Difference Between a Jet and Rocket Engine

Conclusion 

 Scramjets are advanced jet engine technology that works at high altitudes and speeds above Mach 5. They can be used as a viable upper stage for affordable space launches in launch vehicles. They can also be used in hypersonic aircraft as a propulsion unit in the future. Scramjets work on the same basic principle as a jet engine, except they do not have moving parts such as compressors or turbines. With more development work on these engines, the future of high-speed travel in the upper atmosphere would be dominated by Scramjets.