Evolution of PSLV & GSLV – A leap towards strategic space autonomy

What is PSLV (Polar Satellite Launch Vehicle)?

• Designed to launch satellites into Polar and Sun-synchronous orbits
• Can carry light to medium payloads (up to Rs 1.75 tonnes)
• Uses a four-stage propulsion system (alternating solid and liquid stages)
• Highly reliable with over 50 successful missions
• Mostly used for Earth observation and remote sensing satellites
• Lower cost and suitable for multiple small satellite launches
• Developed in early 1990s

What is GSLV (Geosynchronous Satellite Launch Vehicle)?

• Designed to launch satellites into Geosynchronous Transfer Orbit (GTO)
• Can carry heavier payloads (up to Rs 2.5–4 tonnes depending on version)
• Uses a three-stage propulsion system (solid, liquid, and cryogenic stages)
• Includes cryogenic engine for higher efficiency in upper stage
• Used for launching communication satellites and interplanetary missions
• More complex and costlier than PSLV
• Developed later, with first successful launch in 2001

Flowchart of launch vehicle evolution

SLV-3 (1979-80) ──► Experimental

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ASLV (1987-94) ──► Limited success

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PSLV (1993–present) ──► Reliable workhorse

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├─► Used for: Remote sensing, foreign satellites, Chandrayaan-1, MOM

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GSLV Mk I/II (2001–present) ──► GTO launches

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├─► Faced setbacks; mastered cryogenics in 2014

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GSLV Mk III / LVM-3 (2017–present) ──► Heavy-lift, human-rated

├─► Chandrayaan-2, Gaganyaan, OneWeb

UPSC exam questions

✅ Short Answer Questions (3-5 marks)

1. What is the role of cryogenic engines in space launch vehicles?
2. Differentiate between GSLV and PSLV based on payload capacity.
3. Why is PSLV called the ‘Workhorse of ISRO’?

✅ Long Answer Questions (10-15 marks)

1. Discuss the evolution and significance of PSLV in India’s space program.
2. Describe the technological challenges faced by India in developing the GSLV.
3. Explain how PSLV and GSLV have strengthened India’s position in the global satellite launch market.

✅ Analytical / Essay Type Questions (15-20 marks)

1. “India’s self-reliance in space technology reflects its scientific maturity.” Discuss in light of PSLV and GSLV development.
2. Critically examine how ISRO’s launch vehicle development has contributed to India’s strategic and economic capabilities.
3. Analyse the technological and geopolitical implications of India developing indigenous cryogenic technology.