India tests scramjet demonstrator over Bay of Bengal

The Advanced Technology Vehicle, a two-stage sounding rocket, blasted off Sunday with India's scramjet engine demonstrator. Credit: ISRO
The Advanced Technology Vehicle, a two-stage sounding rocket, blasted off Sunday with India’s scramjet engine demonstrator. Credit: ISRO

India’s space agency launched a modified suborbital sounding rocket Sunday and ignited two air-breathing scramjet engines at Mach 6 for a brief five-second experiment that could pave the way for a future reusable space transport system.

The Indian Space Research Organization said the flight occurred “exactly as planned” after blastoff from the Satish Dhawan Space Center on India’s east coast Sunday.

“The successful technology demonstration of air-breathing scramjet engines in flight by ISRO today is a modest yet important milestone in its endeavor to design and develop advanced air-breathing engines including engines for ISRO’s future space transportation system,” the Indian space agency said in a statement.

The scramjet engine package launched from the space center on Sriharikota Island aboard a 3.6-ton (3,277-kilogram) two-stage solid-fueled sounding rocket called the Advanced Technology Vehicle, or ATV, at 0030 GMT Sunday (6 a.m. Indian time; 8:30 p.m. EDT Saturday).

The twin scramjet engines, mounted to the back end of the rocket’s second stage, ignited once the booster reached the desired altitude and speed. The flight followed a pre-programmed sequence, and the scramjet engines burned their hydrogen fuel for about five seconds, according to ISRO.

Scramjets work by ingesting air from the atmosphere and injecting fuel for combustion. Unlike conventional air-breathing jet engines, scramjets do not use rotating fans to compress incoming air.

Liquid-fueled rockets must carry oxidizer along with fuel to place satellites in orbit. Up to three-quarters of the propellant aboard existing launchers consists of oxidizer, and scramjets could allow engineers to design new vehicles to collect oxygen from the rarefied upper atmosphere. That would reduce the weight of propellant a rocket has to carry.

“Also, if those vehicles are made reusable, the cost of launching satellites will further come down significantly,” ISRO said in a statement. “Thus, the future reusable launch vehicle concept along with air-breathing propulsion is an exciting candidate offering routine access to space at far lower cost.”

Scramjets are especially useful at supersonic and hypersonic speeds, and tests of scramjet technology to date have relied on a rocket assist before engine start-up.

Diagram of a scramjet engine. Credit: ISRO
Diagram of a scramjet engine. Credit: ISRO

Sunday’s flight lasted about five minutes, and the scramjet test vehicle touched down in the Bay of Bengal about 200 miles (320 kilometers) from the Sriharikota launch base. Ground stations at the launch site tracked the vehicle during the flight, according to ISRO.

The successful demo flight Sunday made India the fourth country in the world to test scramjet technology in flight. Russia, the United States and China previously flew similar engines on hypersonic test flights.

ISRO called Sunday’s flight a “maiden short-duration experimental test” for India’s scramjet program.

“With this flight, critical technologies such as ignition of air breathing engines at supersonic speed, holding the flame at supersonic speed, air intake mechanism and fuel injection systems have been successfully demonstrated,” ISRO said.

The scramjet test flight came three months after ISRO flew a reduced-scale space plane on a hypersonic demonstration launch to test new heat shield, guidance, navigation and control systems.

Indian officials said after the May 23 space plane flight that the testbed could be a pathfinder for a future unmanned reusable launch vehicle that could take off like a rocket, deploy a satellite in orbit, and return to Earth and land on a runway.

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