The atmospheric phase is the most demanding part of any space mission, whether a launch vehicle climbing to orbit or a crew capsule returning to Earth.
Key Developments
- Launch vehicles accelerate slowly through the atmosphere to minimise structural stress.
- During re‑entry, the Gaganyaan crew module will encounter a re‑entry speed of 7,500‑8,000 m/s.
- More than 99% of the vehicle’s kinetic energy is shed as heat in the surrounding air.
- A small fraction of that heat is reflected back toward the spacecraft, enough to melt unprotected structures.
- The solution is a robust Thermal Protection System (TPS) that can absorb and radiate the intense heat.
Important Facts
The physics of re‑entry is governed by the conversion of kinetic energy into thermal energy. At the stated speed, the energy density is extremely high; even a 1% back‑radiation can raise surface temperatures above 1,500 °C. Modern TPS materials, such as ablative composites and ceramic tiles, are designed to either char away (ablative) or withstand the heat without degrading.
Exam Relevance
Understanding the TPS is crucial for GS3 (Science & Technology) questions on India’s space programme, especially the Gaganyaan mission. It also links to topics on technology development, indigenous capability, and the challenges of human spaceflight, which are frequently asked in the essay and optional papers.
Way Forward
To ensure crew safety, ISRO must continue:
- Rigorous testing of TPS materials under simulate