Syllabus: GS3/Science & Technology
Context
- The Gaganyaan mission will require India to demonstrate the safe re-entry of a crew module carrying astronauts, making its Thermal Protection System (TPS) one of the most critical technologies for ensuring crew safety during the return journey to Earth.
Why is Thermal Protection Critical During Re-entry?
- Handles extreme heat: During Gaganyaan’s return from LEO, the capsule enters the atmosphere at hypersonic speed, converting most of its kinetic energy into intense heat. Plasma temperatures can reach 1,800°C, which could damage the spacecraft.
- No room for failure: Once re-entry begins, the mission cannot be aborted, so the TPS must work reliably on its own.
- Protects astronauts: Rapid deceleration makes manual intervention impossible. The TPS acts as a passive and failsafe barrier.
- Maintains habitability: It keeps the cabin and the underlying aluminium-alloy/CFRP structure within safe temperature limits.
What is a Thermal Protection System?
- A TPS is a combination of specialised materials and structures designed to manage the intense heat generated during atmospheric re-entry and prevent it from reaching the spacecraft’s internal structure.
- Types of Thermal Protection Systems:
- Ablative TPS: The heat shield deliberately sacrifices its outer material to protect the spacecraft. Extreme heat causes the material to decompose, erode and form a protective layer.
- The decomposition releases gases that move outward and create a cooler boundary layer, reducing heat transfer to the spacecraft. The Gaganyaan uses an Ablative TPS.
- Examples: Carbon-phenolic, silica-phenolic and PICA (Phenolic Impregnated Carbon Ablator).
- Radiative TPS: The material absorbs incoming heat and radiates it back into the surrounding environment, mainly as infrared radiation.
- It is particularly useful for reusable spacecraft, where the heat shield needs to withstand repeated re-entry.
- Heat-Sink TPS: The material absorbs and stores thermal energy, raising its own temperature without undergoing major melting or decomposition. The material essentially acts as a thermal reservoir.
- Materials such as copper and aluminium can function as heat sinks.
- Ablative TPS: The heat shield deliberately sacrifices its outer material to protect the spacecraft. Extreme heat causes the material to decompose, erode and form a protective layer.
Gaganyaan mission
- Purpose: To demonstrate the capability to launch human beings (three crew members) to low earth orbit and bring them back safely to earth by landing.
- This manned mission will be the first of ISRO’s human spaceflight missions. The US, Russia and China are the only three countries to have conducted human spaceflights yet.
- Launch vehicle: The Launch Vehicle Mark-3 (LVM3) is the launch vehicle for the Gaganyaan mission.
- Crew Escape System (CES): HLVM3 consists of CES powered by a set of quick acting, high burn rate solid motors which ensures that Crew Module along with the crew is taken to a safe distance in case of any emergency either at launch pad or during ascent phase.
- Orbital Module: The Orbiter Module will orbit the Earth, and it consists of Crew Module (CM) and Service Module (SM) connected by a joint. It is designed to keep the crew safe during ascent, orbital phase, and re-entry.
- The Crew Module (CM) is the habitable space with the Earth-like environment in space for the crew.
- Service Module (SM): It will be used to provide the necessary support to CM while in orbit. It is an unpressurized structure containing thermal system, propulsion system, power systems, avionics systems and deployment mechanisms.
Source: TH
Previous article
India and Japan: Deepening Cooperation
