ISRO Clears Three Key Gaganyaan Crew Module Safety Tests

Syllabus: GS3/ Science and Technology

Context

• The Indian Space Research Organisation (ISRO) has successfully completed three major qualification tests for the Gaganyaan mission’s Crew Module systems.

About the Tests

• The tests covered the Crew Module Up-righting System (CMUS), the Crew Module Service Module Connect Disconnect System (CSCDS), and the Crew Module structure’s ability to withstand Apex Cover separation loads.
• The first test ensures that the crew module returns to an upright position after splashdown in the sea.
  • The system, based on stored cold-gas technology, is a critical safety feature for astronauts.
• The second test involved the separation of the umbilical mechanism that connects the crew module, where the astronauts are housed, with the service module, which provides power and propulsion.
  • The mechanism consists of two units—CSU-1 on the crew module side and CSU-2 on the service module side. 
  • During the crew module’s re-entry into the Earth’s atmosphere, the service module separates from the crew module after CSU-1 disconnects. Subsequently, just before re-entry, CSU-2 also separates.
• The third test validated the structural integrity of the crew module during the separation of the apex cover.
  • The apex cover protects the parachutes and associated systems during the mission and is jettisoned before parachute deployment to enable the safe descent of the crew module.

Crew Module Re-entry and Recovery Process

• After the orbital phase, the propulsion system in the service module will fire its thrusters to de-orbit the Orbital Module (OM), then the service module will separate from the crew module by severing the joint with a redundant mechanism.
• While both modules descend to the earth, the crew module, which is designed to survive the intense thermo-structural loads of re-entry, will decelerate by aero-braking and safely splash down in sea. Meanwhile, the service module will burn up.

Which Configuration is Best for Re-entry?

• The crew module design must balance several critical objectives, including maximise the internal volume, manage the aerodynamic lift and drag generated during atmospheric flight, maintain aerodynamic and hydrodynamic stability, and stabilise the module dynamically at low speeds.
• A spherical configuration offers the highest possible internal volume with the lowest structural mass.
  • However, because a perfect sphere creates no aerodynamic lift, it falls straight down through the atmosphere, like a dropped stone. This subjects the crew to painfully high g-forces.
• A sphere-cone combination is the preferred configuration for a re-entering body.
  • Its blunt base generates a detached shockwave that pushes intense frictional heat away from the spacecraft, while its conical body provides the aerodynamic stability and lift necessary for a controlled, survivable descent.
  • The Gaganyaan crew module has a sphere-cone configuration.

What is Dynamic Instability During Re-entry?

• Dynamic instability refers to a critical condition in which the Crew Module develops rapidly increasing and uncontrolled oscillations while slowing down through Earth’s atmosphere.
• The problem becomes acute as the spacecraft approaches the speed of sound, where shifting shock waves and turbulent airflow generate highly fluctuating aerodynamic forces.
• To prevent these oscillations from growing beyond safe limits, the spacecraft continuously uses small control thrusters to maintain the correct attitude.

Way Ahead

• The Gaganyaan Crew Module represents a major technological achievement in India’s human spaceflight programme. 
• By successfully overcoming the challenges of atmospheric re-entry, the Crew Module forms the foundation of India’s ambition to undertake sustained human space exploration in the future.

Source: AIR, TH