Gaganyaan TV-D1: ISRO Launches First Developmental Test Flight To Demonstrate Performance Of Crew Escape System

Gaganyaan Test Flight: The Indian Space Research Organisation (ISRO) launched the first uncrewed flight mission of the Gaganyaan programme on October 21, 2023, at 10:00 am IST.

Gaganyaan TV-D1 is an important mission because it will demonstrate the performance of the Crew Escape System, and is the first mission of Gaganyaan's uncrewed flight tests.  ( Image Source :X/@ISRO )

Gaganyaan Test Flight: The Indian Space Research Organisation (ISRO) launched the first uncrewed flight mission of the Gaganyaan programme on October 21, 2023, at 10:00 am IST. Known as Test Vehicle Development Flight (TV-D1) or Test Vehicle Abort Flight, the mission, carrying an uncrewed Crew Module and a Crew Escape System, took off from the First Launch Pad at Satish Dhawan Space Centre, Sriharikota, Andhra Pradesh. Gaganyaan TV-D1 is an important mission because it will demonstrate the performance of the Crew Escape System, and is the first mission of Gaganyaan's uncrewed flight tests. 

An in-flight abort of the Crew Escape System will be demonstrated, which means that while the Crew Module is in the air, the Crew Escape System will be jettisoned, so that ISRO will be able to check certain flight parameters, and whether the Crew Escape System can be effectively separated from the Crew Module to save the lives of astronauts in case a mishap occurs. ISRO aims to conduct more test flight missions in the future. 

ISRO will abort the TV-D1 mission at Mach number 1.2, which means that at the time of abort, the speed of the Crew Module will be 1.2 times the speed of the sound in air.

The reason why ISRO will abort the TV-D1 mission at Mach number 1.2 is that it is at this stage that the spacecraft is expected to experience the greatest challenge, in terms of vibration and other parameters. Therefore, if any anomalies are likely to occur, they will probably occur at this stage. Mach number 1.2 is about 360 metres per second. Once the Crew Module achieves this speed, the abort command will be given. The role of the Crew Escape System is to safely pull out the Crew Module from the launch vehicle, so that the Crew Module and the Crew Escape System can go in a direction different from that of the launch vehicle.

As part of the TV-D1 mission, the subsystems of the test vehicle will also be evaluated. The deceleration systems of the Crew Module will also be tested at higher altitudes. 

For this mission, an unpressurised Crew Module is being used, unlike the crewed mission of the Gaganyaan programme, in which a pressurised crew module will be used. Both the pressurised and unpressurised versions have the same mass and size, and are equipped with the same systems for deceleration and recovery, including complete sets of parachutes. 

In the crewed flight test of Gaganyaan, Earth-like atmospheric pressure conditions will be simulated. 

The reason why an unpressurised Crew Module is being used for the first developmental flight test is that the main goal of this mission is to test the Crew Escape System, which does not differentiate between pressurised and unpressurised modules. This mission focuses on the command of abort. There is a possibility of a pressurised Crew Module being used in the next flight.

There are dual redundant avionic systems, which means that there are two sets of systems inside the Crew Module for functions such as navigation, sequencing, telemetry, instrumentation, and power. 

A single-stage liquid propelled test vehicle equipped with a VIKAS engine will carry the Crew Module and the Crew Escape System to an altitude of 11.7 kilometres in about 60 seconds. At that time, an abort command will be given. As a result, the Crew Escape System will pull the Crew Module out of the launch vehicle, and take the Crew Module to an altitude of 16.7 kilometres. The Crew Escape System will be jettisoned, and fall on its own, under the influence of gravity. 

After the apex parachute is removed, drogue parachutes will be deployed from the Crew Module so that its velocity is decreased. The main parachute will be deployed when the Crew Module reaches an altitude of 2.5 kilometres above sea level.

Eventually, the Crew Module will splash down into the Bay of Bengal, and will be recovered by the Indian Navy. The Crew Module will splash down at a distance of about 10 kilometres from the coast of Sriharikota.