Hypersonic
travel seems to be impossible now a days, but it be possible after 10-15
years from now on. Scramjet (supersonic combusting ramjet) is similar to Ramjet
except in this combustion takes place in supersonic airflow. Unlike the Ramjet,
in which air was decelerated at subsonic velocity to be combusted; Scramjet
combusts the air in supersonic speed which give Scramjet very high speed, in
the range of MACH 12(14000 km/hr) to MACH 24(25000 km/hr).
Working of a Scramjet engine |
Scramjet like any other jet engine , uses fuel and
oxidiser to protect thrust. The design of Scramjet consists of a converging
inlet, in which incoming air is compressed using high pressure in front of it;
a combustor ; and a diverging nozzle to produce accelerated thrust. Scramjet
like Ramjet does not use any rotating parts, therefore it require high kinetic
energy of hypersonic flow to compress the incoming air ; and must be
accelerated to high velocity, like Mach 4. Due to supersonic flow of air, fuel
must be injected, mixed, ignited and burned within milliseconds in combustion
chamber.
Scramjet has some advantage over Turbojet engine as
it does not need to carry oxygen, and no rotating parts made it easier to
manufacture. Scramjet has a very high specific impulse than Turbojet. Specific
impulse is a chnage in momentum per unit of propellant. Rocket produce only 600
seconds of specific impulse, while Ramjet produce between 1000 and 4000
seconds.
Computational fluid dynamics (CFD) image of the NASA X-43A with scramjet attached to the underside at Mach 7 |
There are lot of Scramjet aircraft prototype being
tested like NASA X-43A, Boeing X-51, North American X-15, and Chinese WU-14.
Fastest scramjet ever tested is NASA
X-43A which achieved the speed of MACH 9.6.
Many countries like India, China, Russia and Brazil
are conducting test and working on the Scramjet engine. Russian “GLL HOLOD” was
the first to flew in 1991 at a speed of MACH 5.8. Brazil 14-X, India Brahmos-2,
HSTDV and AVATAR RLV are in the progress of developing.
NASA X-43A world fastest scramjet aircraft achieving speed upto MACH 9.6. |
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