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Human spaceflight
Gaganyaan, India's first human spaceflight programme, is in its test flight years: an uncrewed flight carrying the half humanoid Vyommitra is targeted for the last quarter of 2026, and the first crewed flight by 2027. What decides whether a crew comes home is the ablative heat shield under the crew module, and, on longer missions, whether a crew can be shielded from a solar storm.
UPSC has asked
- Prelims 2025: Gaganyaan and micro-gravity research
- Prelims 2022: effects of a major solar storm on the Earth
What a crew module has to survive
7,500 to 8,000 m/sSpeed at which the crew module enters the atmosphere
about 1,800 °CTemperature on the outside of the module
30 to 35 mmThickness of the thermal protection system
below 150 °CWhat the structure underneath must be kept to
- Gaganyaan is the first human spaceflight programme of the Indian Space Research Organisation (ISRO), flying a crew module to low Earth orbit and bringing it back.
How an ablative shield works
- The shield does not resist the heat so much as spend itself on it.
- Its outer layers char, decompose and burn away, carrying the absorbed heat off with them.
- The gases escaping from the surface form a cooler boundary layer that holds the hottest gas away from the wall.
- Because the material is consumed, an ablative shield is used once.
Three ways to survive re-entry
Ablative
- The surface chars and burns away, taking the heat with it
- Single use
- Chosen for the Gaganyaan crew module
Radiative
- A hot outer skin radiates the heat back out
- Can be reused
- Needs materials that stay sound at high temperature
Heat sink
- A thick mass of metal soaks up the heat and holds it
- Heavy, so suited to small capsules
Shielding a crew from radiation
- Weight for weight, hydrogen rich polymers stop protons better than lead, because a hydrogen nucleus is a single proton.
- Such shielding holds off the charged particles of a solar storm but not galactic cosmic rays.
What has happened
1 Sep 2026
AstroRad, a radiation vest, was shown to cut the dose a crew would take in a solar storm.
- It flew uncrewed on Artemis I, a Moon mission of the National Aeronautics and Space Administration (NASA), and is made by Israel's StemRad.
- The modelled dose fell by about 60 per cent for the August 1972 storm and about 40 per cent for October 1989.
21 Aug 2026
ISRO set out where Gaganyaan stands and how the crew module's heat shield will work.
- The first uncrewed flight, carrying the half humanoid Vyommitra, is targeted for the last quarter of 2026, with two more uncrewed flights and the first crewed flight by 2027.
- The crew escape test TV-D1 and two parachute air drop tests are done, and TV-D2 is in progress.
- Every stage of the human-rated LVM3 (Launch Vehicle Mark-3) has been ground tested.
The Hindu, 21 Aug 2026: How Gaganyaan's heat shield will protect the crew (opens in a new tab) · PIB, 5 Aug 2026: Gaganyaan timeline and Bharatiya Antariksh Station (opens in a new tab)