ISRO's crew escape system vehicle, and CGI of a submerged crew module at the bottom of the sea

The Indian Space Research Organisation (ISRO) is preparing for multiple flights of the specially designed test vehicle that will be used to test the Crew Escape System (CES), which will be a crucial element of India’s first human space flight mission (Gaganyaan).

ISRO in August 2022 had successfully tested the Low Altitude Escape Motor that will power the Crew Escape System, a system to eject the Gaganyaan crew module with astronauts in case of an eventuality. The emergency system will jettison the crew module from the launch vehicle if an emergency occurs during the initial phase of the flight.

The Indian space agency test-fired the Low Altitude Escape Motor at Sriharikota on Wednesday and said that the Crew Escape System (CES) takes away the Crew module of the Gaganyaan mission in case of any eventuality and rescues the astronauts.

"In case of mission-abort during the initial phase of flight, LEM provides the required thrust to CES, to take away the Crew Module from the launch vehicle," ISRO said in a statement.

A special purpose solid rocket motor, the LEM is equipped with four reverse flow nozzles and generates a maximum sea level thrust of 842 kN (nominal) with a burn time of 5.98 seconds (nominal). The nozzle end of the motor is mounted at the fore end of the launch vehicle unlike at the aft end in conventional rocket motors to prevent exhaust plumes from filling the crew module and suffocating the astronauts.

The main objective of the test conducted was to evaluate motor ballistic parameters, validate motor subsystem performance, confirm the design margins, evaluate the thermal performance of nozzle liners, validate the integrity of all interfaces, evaluate the head-end mounted safe arm (HMSA) based ignition system performance, and to evaluate side thrust due to misalignment and variation in flow and other functional parameters including flow reversal.

The Gaganyaan mission, which was set to conduct the maiden uncrewed mission this year, has been pushed to 2023 as ISRO continues to perfect the systems and has said that it will not take any chances, since this is the first time it is attempting to send humans into space from India.

The Indian space agency has, however, maintained that it will conduct two unmanned abort missions during which the spacecraft will be launched to an altitude of 15 kilometers and ISRO will simulate an abort scenario after which the crew capsule will return to Earth under parachutes.

ISRO chief S Somnath has said that their first priority is human safety and they will be simulating failures and bringing the crew back safely under those circumstances.