Scramjet

Aerospace Feb 20, 2022

by Aarushi Roy

“Time is the most valuable thing a man can spend.”

~ Theophrastus.

In today's competitive world, all of us are trying to save time and make the most out of the limited resources available to us, aren't we? Over time, humans have come up with several inventions that have substantially reduced our traveling time. From foot to airplane, we have reduced human efforts and traveling time by a significant amount and are still working towards increasing our convenience even more.

Scramjet is one such invention that powers vehicles to operate at high speeds. A scramjet (supersonic-combustion ramjet) is a ramjet engine in which the airflow through the engine remains supersonic or greater than the speed of sound. In a scramjet, high-speed forward motion is utilized to compress the air without any compressor. However, it is an improvement over the ramjet engine as it efficiently operates at hypersonic speeds and allows supersonic combustion.

Image Courtesy: clearias.com

Scramjet-powered vehicles are envisioned to operate at speeds up to at least Mach 15. Scramjet engines are designed to achieve speeds beyond Mach 6, which mixes fuel into the air flowing through it at supersonic speeds, intended for hypersonic aircraft. The fuels utilized in a scramjet are cryogenically liquefied gas such as hydrogen and methane instead of liquid hydrocarbon. The most significant reason for adopting these fuels is to exploit the more excellent heat release per unit weight of fuels that have a higher ratio of hydrogen to carbon atoms than ordinary fractions of petroleum, even though this gain is partly negated by the higher volume per unit of heat release of those same fuels.

Image Courtesy: Wikipedia.com

Another primary reason for utilizing a very cold fuel is that it may be used as a heat sink for cooling a very high-speed (and hence scorching) engine and aircraft structure. The scramjet has an unusual feature: the inlet deceleration and exhaust acceleration occur primarily outside the enclosed engine inlet and exhaust ducts against external aircraft surfaces in front of and to the rear of the engine. In effect, the machine itself is little more than a sophisticated supersonic combustion chamber.

The supersonic speed makes it suitable for flying at lower altitudes than even a boost-glide hypersonic vehicle.

ISRO has successfully tested two 'air breathing' scramjet engines as the first step to perfect a futuristic technology to launch missiles, inject heavier satellites in orbit, and fly astronauts at hypersonic speed.
The Defense Advanced Research Projects Agency (DARPA) and the US Air Force completed the first free flight test of new scramjet-powered hypersonic weapon technology last week — the Hypersonic Air-breathing Weapon Concept (HAWC). - By Ryan Pickrell Published September 28, 2021

Image courtesy: www.darpa.mil

These are specific applications of scramjet engines that show their demand in the aerospace industry and the military sector. If proven to be successful, we may also hear about scramjet engines being utilized in ordinary vehicles in the future. The scramjet engine has a broad scope of applications in the medicinal industry. Every second is precious and can be used for transplantations to save several lives.

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