Scramjet (supersonic combusting ramjet) Technology

♤ Scramjet is a variant of the ramjet that works at higher speeds. It uses atmospheric oxygen (hypersonic air flow) to burn its fuel. This reduces the amount of fuel that the rocket should carry at lift-off, resulting in considerable cost savings.

♤ How it works: The scramjet is composed of three basic components: a converging inlet, where incoming air is compressed; a combustor, where gaseous fuel is burned with atmospheric oxygen to produce heat; and a diverging nozzle, where the heated air is accelerated to produce thrust. The speed of the aircraft moving through the atmosphere force the air to compress within the inlet.

♤ Theoretical projections place the top speed of a scramjet between Mach 12 (8,400 mph; 14,000 km/h) and Mach 24 (16,000 mph; 25,000 km/h) but practically Mach 9.68 has been achieved by NASA’s X-43a experimental aircraft in 2010

♤ India’s status: The Vikram Sarabhai Space Centre (VSSC) is carrying out the ramjet combustor development programme in collaboration with the National Aerospace Laboratories (NAL), Bangalore.

♤ In 2006, ISRO had successfully tested the use of oxygen moving at a speed of Mach 6 - six times the speed of sound - in laboratory conditions to produce a stable supersonic combustion lasting for a few seconds.

♤ With this, India has joined the elite club comprising a handful of nations that are working on mastering the technology. The U.S., Japan, China, Russia, Australia, and some countries in Europe

♤ Advantages: Using scramjet technology will enhance the payload capability and reduce the cost because It does not have to carry oxygen to burn its fuel and not need rotating parts to compress air (as used in conventional jets, all of which add weight, complexity, and a greater number of failure points to the engine).

♤ Higher speed could mean cheaper access to outer space in the future

♤ Challenges: Hypersonic flight within the atmosphere generates immense drag

♤ Temperature found on the aircraft and within the engine can be much greater than that of the surrounding air so “active cooling” is required in which coolant circulating throughout the vehicle skin prevents it from disintegrating.

♤ Maintaining combustion in the supersonic flow presents additional technical challenges, as the fuel must be injected, mixed, ignited, and burned within milliseconds.

♤ Another limitation is the availability of oxygen. Oxygen is limited to the atmosphere and is dense in the 10-20 km region. So scramjet can be used optimally at this height.