ISRO Gaganyaan Mission: Thermal Protection System Explained

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Key takeaways

ISRO is using a specialized Thermal Protection System (TPS) for its Gaganyaan human spaceflight mission to shield the crew capsule during atmospheric re-entry.
During re-entry from Low Earth Orbit (LEO), over 99% of the capsule's kinetic energy converts into plasma heating with temperatures reaching up to 1,800°C.
The heat shield is only 30-35 mm thick, but it successfully keeps internal structural temperatures below 150°C.
High-density carbon phenolic tiles protect the forward nose heat shield, while medium-density silica phenolic tiles cover the side panels and afterbody.
The indigenous ablative technology builds upon flight-proven lineage from the Space Capsule Recovery Experiment and the 2014 LVM3 / CARE mission.

ISRO is preparing for uncrewed flight tests under the Gaganyaan mission, prompting experts to explain how the crew module's Thermal Protection System (TPS) protects astronauts.

A Thermal Protection System (TPS) acts as an advanced outer shield that protects spacecraft from extreme heat while moving through the atmosphere at hypersonic speeds.

When returning from Low Earth Orbit (LEO), over 99% of the capsule's kinetic energy converts into friction heat, reaching plasma temperatures up to 1,800°C that can melt metals.
Atmospheric re-entry is an irreversible process, meaning astronauts cannot abort the mission once the spacecraft begins its descent toward Earth.
Deceleration forces change too quickly for manual pilot controls, making an automatic, passive thermal barrier essential for safety.
The system keeps temperatures inside the capsule low enough to protect human crew members and preserve the composite structural frame.

Extreme friction during re-entry causes resin materials inside the heat shield to absorb heat and undergo chemical breakdown.
As outer layers burn away, a carbon-rich char layer forms to block heat, while shedding outer material carries thermal energy away from the capsule.
Chemical reactions release hot gases through surface pores, creating a gas cushion that pushes intense plasma away from the outer skin of the spacecraft.

The protective shield measures just 30-35 mm in thickness, yet it keeps internal structural temperatures below 150°C despite 1,800°C external heat.
Engineers built the forward nose heat shield using high-density carbon phenolic tiles to withstand peak heat and pressure at the impact point.
The side panels and rear sections use medium-density silica phenolic tiles to manage secondary turbulent air heating.
The design skips fragile ceramic tiles to use durable single-use composites that handle impacts better and need less maintenance.
This indigenous shield builds on flight-tested technology from the Space Capsule Recovery Experiment and the 2014 LVM3 / CARE mission.