Sriharikota - The Indian Space Research Organisation (ISRO) marked a significant milestone with the launch of the inaugural uncrewed mission of the Gaganyaan program on October 21, 2023, at 10:00 am IST.

This mission, referred to as Test Vehicle Development Flight (TV-D1) or Test Vehicle Abort Flight, carried an uncrewed Crew Module and a Crew Escape System. The liftoff occurred from the First Launch Pad at the Satish Dhawan Space Centre in Sriharikota, Andhra Pradesh.

Gaganyaan TV-D1 holds great importance as it serves as a crucial demonstration of the Crew Escape System's performance, representing the maiden uncrewed flight test for the Gaganyaan program. The mission entails an in-flight abort of the Crew Escape System, where the system is jettisoned while the Crew Module is airborne. This allows ISRO to assess specific flight parameters and the system's capability to separate effectively from the Crew Module, ensuring astronaut safety in the event of an emergency. ISRO has plans for further test flight missions in the program.

The TV-D1 mission will be aborted at Mach number 1.2, indicating that the Crew Module's speed will be 1.2 times the speed of sound in the air at the time of the abort command. This stage is chosen as it represents the most challenging phase for the spacecraft, with significant vibration and other parameters. Mach number 1.2 is approximately 360 meters per second. Once the Crew Module reaches this speed, the abort command will be issued. The role of the Crew Escape System is to safely separate the Crew Module from the launch vehicle, diverting their paths.

During the TV-D1 mission, subsystems of the test vehicle will also undergo evaluation, including testing the Crew Module's deceleration systems at higher altitudes.

It's worth noting that this mission uses an unpressurized Crew Module, in contrast to the crewed mission of the Gaganyaan program, which will employ a pressurized crew module. Both versions share the same mass and size and are equipped with identical deceleration and recovery systems, including complete sets of parachutes. The crewed Gaganyaan flight tests will simulate Earth-like atmospheric pressure conditions.

The choice of an unpressurized Crew Module for the first developmental flight test stems from the primary focus of testing the Crew Escape System, which functions equally well with pressurized and unpressurized modules. This mission emphasizes the abort command. Future missions may involve a pressurized Crew Module.

Dual redundant avionic systems are incorporated within the Crew Module, providing redundancy for functions like navigation, sequencing, telemetry, instrumentation, and power.

The test vehicle, equipped with a VIKAS engine, is a single-stage liquid-propelled system that propels the Crew Module and the Crew Escape System to an altitude of 11.7 kilometers in about 60 seconds. At this point, the abort command is issued, and the Crew Escape System removes the Crew Module from the launch vehicle, taking it to an altitude of 16.7 kilometers. The Crew Escape System is then jettisoned, allowing it to descend under the influence of gravity.

Following the removal of the apex parachute, drogue parachutes are deployed from the Crew Module to reduce its velocity. The main parachute is deployed when the Crew Module reaches an altitude of 2.5 kilometers above sea level.

Ultimately, the Crew Module splashes down into the Bay of Bengal and is recovered by the Indian Navy, approximately 10 kilometers from the coast of Sriharikota.