The Gaganyaan mission's Flight Test Vehicle Abort Mission (TV-D1) test flight by ISRO is all set to take place at the Satish Dhawan Space Centre-SHAR, Sriharikota, between 7 am and 9 am on October 21, 2023. The Gaganyaan project’s goal is to showcase human spaceflight capability. It involves sending a three-member crew into a Low-Earth Orbit (LEO) at 400 kilometres for a three-day mission, followed by a safe return to Earth—including a planned splashdown in the waters of the Indian sea. In preparation for the Gaganyaan mission, a hand-picked team of four astronauts is currently undergoing training at the Astronaut Training Facility in Bengaluru, which includes mission-specific training. Why is the mission's first test flight so significant?
“During this flight, an abort scenario will be simulated, replicating the conditions experienced during the ascent phase of the Gaganyaan mission at a Mach number of 1.2. At an altitude of approximately 17 kilometres, the Crew Escape System (CES) will separate from the Test Vehicle. Following this separation, the autonomous abort sequence will be initiated, including the CES separation and the deployment of multiple parachutes, ultimately resulting in the safe landing of the Crew Module (CM) in the sea, approximately 10 kilometres off the Sriharikota coast,” explained space expert Girish Linganna.
The CM is designed to house the astronauts in a pressurized, Earth-like atmospheric environment throughout the mission. ISRO announced that the CM would be retrieved from the Bay of Bengal following its touchdown, with the assistance of a specialized vessel and a diving team from the Indian Navy. Indian Navy personnel are already undertaking mock operations for the module’s recovery.
The CM has completed its integration and undergone various electrical tests at ISRO’s Bengaluru facility, which include an acoustic test. Following this, it was sent to SDSC-SHAR on August 13 for undergoing vibration tests and preliminary integration with the CES before its final integration onto the Test Vehicle at the launch pad.
The Test Vehicle Abort Mission (TV-D1) is tasked with showcasing the functionality of the CES. The TV-D1 rocket is a one-stage liquid-fuelled vehicle designed to carry payloads that include the CM, escape systems equipped with rapid-ignition solid motors, CM fairing and interface adapters, the space agency said.
The development of the CM for the Gaganyaan mission is progressing through various stages. The TV-D1 is an unpressurized variant that has undergone integration and testing and is now prepared for transport to the launch site. This unpressurized CM version has the overall size and mass of the actual Gaganyaan CM.
“Within the CM, all the components necessary for deceleration and recovery are housed. This includes a comprehensive array of parachutes, Recovery Aids Actuation Systems and pyrotechnic devices. Recovery Aids Actuation Systems are mechanisms that control and deploy different kinds of devices, such as parachutes or flotation equipment, during the spacecraft’s descent phase to ensure safe and controlled landing. The CM is also equipped with an extensive array of instruments to record flight data, allowing for assessment of various system performances,” added Linganna.
He further says that pyrotechnic devices are small, explosive devices used to initiate specific actions in aerospace and engineering applications. They generate controlled explosions to initiate specific tasks, such as deploying parachutes, separating spacecraft components, or igniting propulsion systems. These devices, designed to work reliably in extreme conditions of space and re-entry, are crucial for ensuring precise and timely actions in various aerospace systems.
“The avionics systems within the CM are configured with dual redundancy for such functions as navigation, sequencing, telemetry, instrumentation and power management. The phrase, ‘dual redundancy for functions’, means that critical functions or systems have two identical backup systems to ensure reliability and safety. If one system fails, the redundant backup can take over seamlessly ensuring that critical functions—such as navigation, sequencing, telemetry, instrumentation and power remain operational reducing the risk of a failure in essential functions and enhancing safety and reliability,” remarked Linganna.
Experts say that Test Vehicle mission featuring this CM is a significant achievement for the overall Gaganyaan programme, as it represents the integration of an almost complete system for a flight test. With this test flight proving successful, the way will be paved for the rest of the qualification tests and unmanned missions that have been planned, finally leading to the first Gaganyaan mission which will carry Indian astronauts to space.