Flush with the success of the technology demonstration flight of its Reusable Launch Vehicle (RLV- TD) last month, ISRO is gearing up to test a scramjet engine based on air-breathing propulsion.

The test flight of the indigenously-developed scramjet engine is scheduled to take place from the Satish Dhawan Space Centre at Sriharikota sometime in July.

Named Advanced Technology Vehicle (ATV), the test platform will comprise a scramjet engine hitched to a two-stage sounding rocket (RH- 560).

“The vehicle has been characterised and is being fabricated at the VSSC and the ISRO Propulsion Complex, Mahendragiri,” VSSC Director K.Sivan told The Hindu over phone from Sriharikota, amid preparations for the launch of the PSLV-C34 carrying 20 satellites.

Coasting phase

The air-breathing engine will be released at a height of 70 km and ignited during the coasting phase. Apart from the hypersonic ignition at Mach 6, ISRO hopes to sustain the combustion for 5 seconds.

“The test is also expected to help us achieve good thrust value with the scramjet engine,” Dr. Sivan said.

Maintaining combustion in hypersonic conditions poses technical challenges because the fuel has to be ignited within milliseconds.

Space agencies across the world are focussing on the development of scramjet technology because it contributes to smaller launch vehicles with more payload capacity and promises cheaper access to outer space.

Atmospheric oxygen

While conventional rocket engines need to carry both fuel and oxidiser on board for combustion to produce thrust, scramjets obtain oxygen from the atmosphere by compressing the incoming air before combustion at hypersonic speed. The scramjet engine can also liquefy the oxygen and store it on board.

Dr. Sivan said the post-flight analysis of the RLV-TD test flight had shown encouraging results.

Critical technology

“We could understand the hypersonic aerothermodynamics of the delta winged body, the Thermal Protection System worked well and the hypersonic re-entry and autonomous navigation and landing could be validated. Another critical technology that was successfully tested was the Flush Air Data System to measure the surface pressure on the aircraft.”

He said it would take more analysis and detailed discussions and planning to move on to the development of the full-scale version of the RLV.