Relevance: GS III (Science & Tech – Space Indigenization) | Source: The Hindu

1. The Human Context: Stop Throwing Away Planes

Imagine if we scrapped a Boeing 747 after every single flight. Air travel would be unaffordable. Yet, for decades, space agencies did exactly that with rockets.

• The Shift: We are moving from Expendable Launch Vehicles (ELVs) (Use & Throw) to Reusable Launch Vehicles (RLVs) (Use & Return).
• The Impact: This shift, led by private players, has slashed launch costs by 5-20 times, making the $1 trillion space economy possible.

2. The Science: Beating the “Tyranny of the Rocket Equation”

• The Problem: The Tsiolkovsky Rocket Equation dictates that ~90% of a rocket’s mass is fuel and tanks. Only ~4% is the actual payload (satellite).
• The Old Way: To save weight during ascent, rockets like India’s PSLV drop their empty fuel stages into the ocean—wasted forever.
• The New Solution: Instead of crashing, the rocket stage keeps some fuel reserve. It uses Retro-Propulsion (firing engines against the motion) to slow down and land vertically back on Earth.

3. India’s Mission (ISRO’s Two Paths)

India is actively developing its own reusability tech to replace the aging PSLV:

• Winged Approach: RLV-TD (Pushpak). It launches vertically like a rocket but glides back to a runway like a plane (similar to the Space Shuttle).
• Vertical Landing: ADMIRE (Test Vehicle). Developing technology to land rocket stages vertically using legs.
• The Future: These technologies will power ISRO’s Next Generation Launch Vehicle (NGLV).

UPSC Value Box

Q. With reference to space technology, the term “Retro-Propulsion” is best described as:

1. A propulsion system that uses nuclear energy for deep space exploration.
2. A technique where rocket engines are fired against the direction of motion to decelerate for a soft landing.
3. The method of using gravitational capability of planets to accelerate spacecraft.
4. A mechanism used in scramjets to compress air at supersonic speeds.

Correct Answer: (2)