Why is Scramjet Engine in News Headlines Now

In a scramjet engine, combustion occurs at hypersonic speeds. Proper fuel-air mixing, flame propagation, and cooling of engine components are affected by a shorter air residence time. India’s DRDO (Defense Research and Development Organization) made headlines a few months ago when it completed the maiden flight test of its uncrewed scramjet demonstration aircraft for hypersonic flight. Yes, that’s a mouthful. The ‘Hypersonic Technology Demonstrator Vehicle (HSTDV)’ was the official name of the demonstration plane. The plane was designed to reach speed of more than Mach 6. To put that in perspective, a passenger plane travels at a much slower speed than Mach 1. First, let’s look into Ramjets and Scramjets before we proceed further.

What Exactly is RAMJET?

• It’s a type of engine used in missiles, planes, and rockets to propel them forward
• It is most effective when the body moves at a speed of 3-6 Mach
• It’s a brand-new innovation in the field. While current engines can only travel at 1-2 Mach, future engines will be able to travel at much higher speeds. The Ramjet engine contributes to an increase in the speed to 3-6 Mach
• Because Ramjet cannot produce forward motion at low speeds, it is initially assisted by a conventional jet before Ramjet takes over

An Overview of SCRAMJET

• Supersonic Combustion Ramjet is the abbreviation for the Supersonic Combustion Ramjet
• It achieves higher speeds than Ramjet
• It’s used to travel at supersonic speeds
• For all mission stages, conventional, Ramjet, and Scramjet engines will be required
• It does not have movable parts (unlike a turbine in a conventional engine). Such high speeds are impossible for moving parts to withstand.
• It’s a Ramjet, which means combustion takes place in a supersonic gas stream

Why is SCRAMJET in Headlines?

• In July 2016, ISRO tested a miniature model of the ‘SCRAMJET’ engine, developed in-house
• The test platform, dubbed Advanced Technology Vehicle (ATV), will feature a scramjet engine coupled to a two-stage sounding rocket
• The new engine is expected to aid in launching satellites and other space systems in the future
• Scramjet Propulsion Experiment (SPEX) is the name of the experiment

Advantages of Scramjets

• Scramjet does not need to carry its oxygen; it collects oxygen from the surrounding environment
• It is much easier to manufacture compared to a jet engine or turbine because there are no rotating parts
• It has a higher count of specific impulse (change in momentum per unit of fuel expelled) compared to a  conventional engine
• Because scramjets don’t have oxidiser tanks, they’re much lighter, faster, and ultimately less expensive than traditional rocket technology
• It’s only exhaust is water, released from combining hydrogen, the fuel, oxygen, and oxidiser, and it needn’t discard massive empty tanks as conventional rockets do

Design of Scramjet 

The schematics of a using Scramjet (or Supersonic Combustion Ramjet) appear to be pretty straightforward – air is drawn in through the front, with the fuel burning in the middle, and exhaust gas ejected from the back, to generate thrust. The design’s simplicity, however, comes to a halt here. The design of a suitable scramjet powerplant is complicated due to air compressibility, complex flows, fuel injection, air inlet design, high temperatures, and so on. The use of Scramjet is inefficient at low speeds, but as they reach supersonic speeds, they become more efficient.

Why Switch to Scramjet?

The decision to switch from ramjets to scramjets was motivated by the need to reduce the temperature at higher speeds. This technology will also reduce the weight of the launch vehicle. GSLV rockets are around 400 tonnes in weight, with 200 tonnes of oxygen. Scramjet technology eliminates the need for a rocket to transport oxygen, resulting in reduced weight of the launch vehicle. The rocket’s payload capacity can be increased.

Due to its use in military missiles, low-cost access to space, and other applications, the scramjet engine is the most suitable air-breathing propulsion system and suitable option for high-speed flight (Ma4). 

Conclusion

When it comes to future space transportation, ISRO’s development of the use of Scramjet engines represents a significant step. Reusable launch vehicles need a powered long return cruise flight, and an air-breathing propulsion system provides the answer. A second cruise missile, Brahmos II, is being developed by DRDO using the same scramjet technology. As a result, the development of ramjet and scramjet technologies should be accelerated for India to conduct future sophisticated space missions. In addition, it will give life to our much-touted “Make In India” policy.