GS Paper III · Science & Technology · Space
🚀 Satellite Launch Vehicles — ISRO & India
Definition · How Rockets Work · SLV → ASLV → PSLV → GSLV → LVM3 → SSLV · HLVM3 for Gaganyaan · NGLV/Project Soorya · Private Sector · SSLV–HAL Transfer · Updated 2024–26 · PYQs & MCQs
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What is a Launch Vehicle? — Definition & Architecture
Definition First · Newton's 3rd Law · Components
📖 Definition (Exam-Ready)
A Satellite Launch Vehicle (SLV) is a rocket-powered vehicle that transports spacecraft and payloads from Earth's surface beyond the atmosphere — either into orbit around Earth or to another destination in outer space. It provides the thrust needed to overcome Earth's gravitational pull and achieve orbital velocity (~7.9 km/s for LEO).
Satellites cannot travel to space independently — they rely entirely on launch vehicles for their journey into orbit. Once in space, the payload (satellite) separates from the launch vehicle and operates on its own propulsion.
Satellites cannot travel to space independently — they rely entirely on launch vehicles for their journey into orbit. Once in space, the payload (satellite) separates from the launch vehicle and operates on its own propulsion.
🚀 Launch Vehicle Architecture — Fairing · Payload Attach Fitting · Centerbody · Interstage · First Stage · Second Stage · Solid Rocket Motors | Legacy IAS Advanced Launch Vehicle Architecture
🎯 "The Dart Thrown in Stages" Analogy — for Non-Science Students
Imagine trying to throw a dart so hard that it keeps circling the Earth forever. You'd need incredible force. Now imagine instead of one throw, you get multiple throws in sequence — the first propels you up through thick air, the second takes you higher where air is thin, the third gives the final push to reach orbital speed. That's exactly what a multi-stage rocket does — each stage fires, accelerates the vehicle, then drops away (dead weight), making the next stage's job easier. PSLV has 4 stages; GSLV and LVM3 have 3 stages. Each stage = one "throw" upward.
Key Components (from the Infographic)
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Payload Fairing
Protective nose cone that shields the satellite from aerodynamic forces and heat during ascent through the atmosphere. Jettisoned once the rocket reaches space (typically at ~120 km altitude) — exposing the satellite. Fairing drops add to space debris.
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Spacecraft / Payload
The actual satellite or mission payload — communication satellite, Earth observation satellite, scientific probe. Attached to the rocket via the Payload Attach Fitting (PAF). Separates and deploys into the target orbit at mission completion.
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Interstage / Centerbody
Structural connectors between rocket stages. The interstage holds stages together during flight and allows clean separation when a stage burns out. Centerbody = main structural body of the rocket. Explosive bolts or pneumatic mechanisms trigger stage separation.
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First Stage
Most powerful stage — must lift the entire rocket off the ground against Earth's strongest gravity. Usually solid propellant (PSLV: S139 solid motor) or liquid (LVM3: L110 liquid core). Burns out first and is discarded. Largest component by mass.
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Solid Rocket Motors (Strap-ons)
Additional booster rockets attached around the first stage to provide extra thrust at liftoff. PSLV-XL has 6 strap-ons; PSLV-QL has 4; PSLV-DL has 2. LVM3 has 2 large S200 solid strap-ons (each burns for 128 seconds). They fall away when spent.
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Upper Stages (Cryogenic/Liquid)
Final stages operate in the vacuum of space. GSLV and LVM3 use cryogenic engines (liquid hydrogen + liquid oxygen) for maximum efficiency. India's CE-7.5 (GSLV) and CE-20 (LVM3) are indigenous — took 20+ years to develop. Cryogenic engines give 30–40% more thrust per kg of fuel.
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How a Rocket Works — Physics for Non-Science Students
Newton's 3rd Law · Propellants · Staging · Orbital Velocity
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Newton's 3rd Law — Action & Reaction
Every action has an equal and opposite reaction.
Rocket engines burn propellant and expel hot gases backward (action) at tremendous speed. The rocket is pushed forward (reaction). Unlike a car engine that pushes against the road, a rocket pushes against nothing — it works in the vacuum of space because it carries its own oxidiser. Analogy: Blow up a balloon and release it — it flies forward while air jets backward. A rocket is a controlled version of this.
Rocket engines burn propellant and expel hot gases backward (action) at tremendous speed. The rocket is pushed forward (reaction). Unlike a car engine that pushes against the road, a rocket pushes against nothing — it works in the vacuum of space because it carries its own oxidiser. Analogy: Blow up a balloon and release it — it flies forward while air jets backward. A rocket is a controlled version of this.
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Multi-Stage Design — Why Discard Stages?
Dead weight kills efficiency. An empty rocket tank is dead weight that the next engine must carry unnecessarily. By dropping spent stages, the remaining rocket is much lighter — reaching higher speeds with less fuel. Analogy: Hiking a mountain with a backpack — you leave unnecessary items at base camp, camp 1, camp 2. Lighter at each stage = faster ascent.
PSLV has 4 stages. Each drops away in sequence as fuel is exhausted.
PSLV has 4 stages. Each drops away in sequence as fuel is exhausted.
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Solid vs Liquid vs Cryogenic Propellant
Solid: Like a firecracker — simple, reliable, can't throttle. PSLV Stage 1, SSLV.
Liquid: Like a car engine — controllable, can throttle. PSLV Stage 2&4 (Vikas engine).
Cryogenic: LH₂ + LOX at -253°C/-183°C — most efficient. GSLV CE-7.5, LVM3 CE-20. 30-40% more thrust/kg than others.
Liquid: Like a car engine — controllable, can throttle. PSLV Stage 2&4 (Vikas engine).
Cryogenic: LH₂ + LOX at -253°C/-183°C — most efficient. GSLV CE-7.5, LVM3 CE-20. 30-40% more thrust/kg than others.
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Guidance System
Inertial Navigation System (INS) + GPS tracks position and velocity throughout flight. Steerable nozzles (gimbal) adjust rocket direction. Software computes trajectory corrections in real time. Any deviation → automatic correction. PSLV has a near-perfect guidance record.
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Orbital Velocity
To stay in LEO, a satellite needs ~7.9 km/s sideways speed. At this speed, the satellite's "fall" toward Earth curves away as fast as Earth's surface curves — it keeps missing! GEO needs ~3.07 km/s (farther = slower). That's why rockets tilt after liftoff — to gain horizontal speed, not just altitude.
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Evolution of ISRO's Launch Vehicles — SLV to HRLV
1980 → 2026 · Height · Weight · Payload · Propulsion
📈 The Evolution of ISRO's Launch Vehicles — SLV-3 (21.5m, 40kg LEO) → ASLV → SSLV → PSLV → GSLV → LVM3 (45.1m, 1,900kg payload) → HRLV (91m, Human-Rated) | Legacy IAS Presents
💡 Reading the Infographic — The 1,000-fold Journey
ISRO's launch vehicle evolution spans 40+ years and a 1,000-fold increase in payload capacity: SLV-3 (1980) carried just 40 kg to LEO. LVM3 (current) carries 10,000 kg to LEO — 250× more. The upcoming NGLV will carry 30,000 kg — 750× more than SLV-3. Each generation brought new propulsion technologies: All-solid → Solid+Liquid → + Cryogenic → Semi-cryogenic (NGLV). The HRLV at 91m is India's tallest planned rocket, designed to carry humans to the Bharatiya Antariksh Station (BAS) and eventually to the Moon.
ISRO Launch Vehicle Evolution — Payload capacity growth over 50 years | Legacy IAS Original
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Retired Launch Vehicles — SLV-3 & ASLV
India's First Rockets · Dr. APJ Abdul Kalam · Foundation
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SLV-3 — Satellite Launch Vehicle (1980–1983) RETIRED
India's first experimental satellite launch vehicle. Led by Dr. APJ Abdul Kalam (later called "Missile Man of India").
📏 Height: 21.5m | ⚖ Liftoff weight: 17 tonnes | 💨 4-stage all-solid
🎯 Payload: 40 kg to LEO (400 km circular orbit)
First successful launch: July 18, 1980 from SHAR, Sriharikota — placed Rohini RS-1 in orbit, making India the 6th country to launch a satellite with its own rocket.
First flight (1979): Partial failure. Total flights: 4 (1979–1983). Status: Retired 1983.
📏 Height: 21.5m | ⚖ Liftoff weight: 17 tonnes | 💨 4-stage all-solid
🎯 Payload: 40 kg to LEO (400 km circular orbit)
First successful launch: July 18, 1980 from SHAR, Sriharikota — placed Rohini RS-1 in orbit, making India the 6th country to launch a satellite with its own rocket.
First flight (1979): Partial failure. Total flights: 4 (1979–1983). Status: Retired 1983.
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ASLV — Augmented Satellite Launch Vehicle (1987–1994) RETIRED
Bridge between SLV-3 and PSLV — aimed to triple payload capacity. Tested key technologies for PSLV (strap-on boosters, inertial navigation, closed-loop guidance).
📏 Height: 23.6m | ⚖ Liftoff: 40 tonnes | 💨 5-stage all-solid
🎯 Payload: 150 kg to 400 km LEO
Record: 4 development flights (1987–1994). First 2 were failures; last 2 succeeded (SROSS-C and SROSS-C2).
Legacy: Technologies validated for PSLV development. Status: Retired 1994.
📏 Height: 23.6m | ⚖ Liftoff: 40 tonnes | 💨 5-stage all-solid
🎯 Payload: 150 kg to 400 km LEO
Record: 4 development flights (1987–1994). First 2 were failures; last 2 succeeded (SROSS-C and SROSS-C2).
Legacy: Technologies validated for PSLV development. Status: Retired 1994.
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Active Launch Vehicles — India's Current Fleet
PSLV · GSLV Mk II · LVM3 · SSLV · Sounding Rockets
PSLV — Polar Satellite Launch Vehicle · India's Workhorse
📖 PSLV — Definition & Key Facts
PSLV (Polar Satellite Launch Vehicle) = India's 3rd-generation, most reliable launch vehicle. First successfully launched October 1994. India's first launch vehicle with liquid stages. Called "Workhorse of ISRO" for LEO/SSO missions.
📏 Height: ~44m | ⚖ Liftoff mass: 295–320 tonnes (variant-dependent) | 💨 4-stage alternating solid-liquid
🎯 Payload to SSO (600 km): 1,750 kg | To LEO: 3,800 kg | To GTO: 1,425 kg
🏆 World record: 104 satellites in one launch (PSLV-C37, Feb 15, 2017)
📏 Height: ~44m | ⚖ Liftoff mass: 295–320 tonnes (variant-dependent) | 💨 4-stage alternating solid-liquid
🎯 Payload to SSO (600 km): 1,750 kg | To LEO: 3,800 kg | To GTO: 1,425 kg
🏆 World record: 104 satellites in one launch (PSLV-C37, Feb 15, 2017)
Stage 1
SOLID
SOLID
S139 Solid Rocket Motor
Uses 139 tonnes of HTPB (Hydroxyl-terminated polybutadiene) propellant. Provides ~4,800 kN thrust. Burns for ~100 seconds. Augmented by 0, 2, 4, or 6 solid strap-ons (variants: CA, DL, QL, XL). The XL strap-ons each add 719 kN thrust.
Stage 2
LIQUID
LIQUID
Vikas Engine (Earth-storable liquid)
Uses UDMH (fuel) + N₂O₄ (oxidiser) — hypergolic propellants (self-igniting on contact). 799 kN thrust. Burns for ~150 seconds. Vikas engine = India's workhorse liquid engine, also used in GSLV Stage 2 and LVM3 L110 stage.
Stage 3
SOLID
SOLID
S7 Solid Motor (High-altitude)
Smaller solid stage providing high thrust at high altitude where air resistance is minimal. Burns for ~83 seconds. Provides the final solid impulse before the liquid upper stage for orbit insertion.
Stage 4
LIQUID
LIQUID
Two Earth-Storable Liquid Engines (PS4)
Two small liquid engines (7.6 kN each) that can be restarted multiple times in space. Used for precise orbit insertion. PSLV Orbital Experiment Module (POEM) uses this spent stage as an orbital platform for experiments — waste nothing!
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PSLV Variants
PSLV-CA (Core Alone): No strap-ons. Lightest. PSLV-DL: 2 strap-ons. PSLV-QL: 4 strap-ons. PSLV-XL: 6 solid strap-ons — most powerful PSLV variant. Used for Chandrayaan-1, Mangalyaan, Aditya-L1, SpaDeX.
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PSLV Notable Missions
Chandrayaan-1 (2008) · Mangalyaan (MOM, 2013) · 104 satellites in one shot (2017) · Aditya-L1 (2023, PSLV-C57) · SpaDeX (Dec 2024, PSLV-C60) · XPoSat (Jan 2024). 50% of PSLV development now being handed to private sector (2025).
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PSLV Commercialisation
ISRO awarded contract for 5 PSLVs to HAL+L&T consortium. ISRO Chairman V. Narayanan (2025): 50% of PSLV development to be transferred to Indian private companies. Aim: 50 launches per year from current 10–12. 80–85% of PSLV systems already made by Indian industries.
GSLV Mk II — Geosynchronous Satellite Launch Vehicle
📖 GSLV Mk II — Key Facts
GSLV Mk II = India's 4th-generation launch vehicle. Uses indigenous cryogenic upper stage (CE-7.5 engine, developed after Russia denied technology under US/MTCR pressure in 1990s). Primary vehicle for communication satellites to GTO.
📏 Height: ~51.7m | ⚖ Liftoff: ~420 tonnes | 💨 3-stage (solid + liquid + cryogenic)
🎯 Payload to GTO: 2,500 kg | To LEO: 6,000 kg
📏 Height: ~51.7m | ⚖ Liftoff: ~420 tonnes | 💨 3-stage (solid + liquid + cryogenic)
🎯 Payload to GTO: 2,500 kg | To LEO: 6,000 kg
Stage 1
SOLID
SOLID
S139 Solid Motor + 4 Liquid Strap-ons
Same solid core as PSLV Stage 1. Augmented by 4 liquid strap-ons (each with one Vikas engine) — providing additional 660 kN thrust each. The liquid strap-ons give GSLV more control and thrust than PSLV's solid strap-ons.
Stage 2
LIQUID
LIQUID
Vikas Engine (GS2)
Single Vikas engine (800 kN thrust). Earth-storable liquid propellant. Burns for ~150 seconds. Same engine technology as PSLV Stage 2.
Stage 3
CRYO
CRYO
CE-7.5 Indigenous Cryogenic Engine
India's first indigenous cryogenic engine. Liquid Hydrogen (LH₂ at -253°C) + Liquid Oxygen (LOX at -183°C). ~73.5 kN thrust. Burns for ~720 seconds. Took 20+ years to develop after Russia denied technology. GSLV used for Chandrayaan-2, NVS-02 (ISRO 100th mission, Jan 2025).
LVM3 / GSLV Mk III — India's Heaviest Rocket
📖 LVM3 — Key Facts
LVM3 (Launch Vehicle Mark 3) — previously called GSLV Mk III. India's most powerful operational rocket. Used for Chandrayaan-2, Chandrayaan-3, OneWeb constellation launches. HLVM3 variant = human-rated for Gaganyaan.
📏 Height: ~43.5m | ⚖ Liftoff: ~640 tonnes | 💨 3-stage (2 solid strap-ons + liquid core + cryogenic)
🎯 Payload to GTO: 4,000 kg | To LEO: 10,000 kg ("Fat Boy" of ISRO)
📏 Height: ~43.5m | ⚖ Liftoff: ~640 tonnes | 💨 3-stage (2 solid strap-ons + liquid core + cryogenic)
🎯 Payload to GTO: 4,000 kg | To LEO: 10,000 kg ("Fat Boy" of ISRO)
Stage 1
SOLID
SOLID
S200 Solid Rocket Boosters (×2)
Two massive S200 solid rocket motors — each holds 200 tonnes of HTPB propellant. Each generates 5,150 kN thrust. Burns for ~128 seconds. Largest solid boosters developed in India. After burning out, they separate and fall away.
Core
LIQUID
LIQUID
L110 Liquid Core — 2 Vikas Engines
Two Vikas engines in the core liquid stage. 1,598 kN combined thrust. Uses UDMH + N₂O₄. Burns for ~200 seconds. The liquid stage ignites on the ground simultaneously with the solid boosters — this "lit before launch" design improves reliability.
Stage 3
CRYO
CRYO
C32 — CE-20 Indigenous High-Thrust Cryogenic Engine
India's most powerful cryogenic engine. 200 kN thrust — nearly 3× more thrust than CE-7.5 on GSLV. LH₂ + LOX. Burns for ~640 seconds. Throttleable — can adjust thrust in flight. CE-20 was human-rated for Gaganyaan. Enables 10 tonne payloads to LEO.
⭐ LVM3 Notable Missions + Commercial Success
Chandrayaan-2 (2019) · Chandrayaan-3 (July 2023) — India's Moon lander that successfully reached south pole.
OneWeb Commercial: LVM3 launched 36 OneWeb satellites in December 2022 and 36 more in March 2023 — ISRO's entry into mega-constellation launch market.
HLVM3 (Human-Rated variant): LVM3 upgraded with Crew Escape System (CES), additional safety checks for Gaganyaan. CE-20 engine human-rated February 2024. Gaganyaan-G1 uncrewed launch campaign began 2025.
OneWeb Commercial: LVM3 launched 36 OneWeb satellites in December 2022 and 36 more in March 2023 — ISRO's entry into mega-constellation launch market.
HLVM3 (Human-Rated variant): LVM3 upgraded with Crew Escape System (CES), additional safety checks for Gaganyaan. CE-20 engine human-rated February 2024. Gaganyaan-G1 uncrewed launch campaign began 2025.
SSLV — Small Satellite Launch Vehicle · The "Auto-rickshaw" of ISRO
📖 SSLV — Key Facts 2025 Current Affairs
SSLV (Small Satellite Launch Vehicle) = India's newest operational rocket designed for rapid, low-cost, on-demand launches of small satellites. Development complete — technology transferred to HAL.
📏 Height: ~34m | ⚖ Liftoff: ~120 tonnes | 💨 3 solid stages + liquid VTM terminal stage
🎯 Payload to 500 km LEO: 500 kg | To SSO (500 km): 300 kg
⏱ Assembly time: 72 hours (vs weeks for PSLV) | 👥 Crew needed: Minimal
📏 Height: ~34m | ⚖ Liftoff: ~120 tonnes | 💨 3 solid stages + liquid VTM terminal stage
🎯 Payload to 500 km LEO: 500 kg | To SSO (500 km): 300 kg
⏱ Assembly time: 72 hours (vs weeks for PSLV) | 👥 Crew needed: Minimal
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Why SSLV was Needed — The Small Satellite Revolution
Global demand for small satellite launches exploded with commercial constellations (Earth observation, IoT, broadband). These satellites don't want to wait for a PSLV to fill up — they want dedicated launches on demand. SSLV provides: quick turn-around, lower cost, multiple orbit options without co-passengers. Target market: Nano/micro/mini satellites (1 to 500 kg). Analogy: PSLV = city bus (waits for many passengers). SSLV = Ola Auto (instant, individual, smaller).
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SSLV Tech Transfer to HAL — Historic Milestone Sep 2025
September 10, 2025: ISRO, NSIL, and IN-SPACe signed a landmark technology transfer agreement with HAL (Hindustan Aeronautics Limited) for complete SSLV production. HAL bid: ₹511 crore (~$59.7 million). First complete launch vehicle technology ever transferred by ISRO to any company. HAL will independently build, own, and commercialise SSLV launches (6–10 per year). India's 100th Space Technology Transfer agreement. Transfer period: 24 months.
💡 SSLV Launch History
SSLV-D1 (Aug 2022): First flight — partial failure. Satellites injected into wrong orbit (circular vs intended elliptical). 3 satellites lost. Cause: vibration disturbance during 2nd stage separation affected sensor.
SSLV-D2 (Feb 2023): Successful. Launched EOS-07 (ISRO) + Janus-1 (US startup Antaris) + AzaadiSAT-2 (Chennai's Space Kidz India).
SSLV-D3 (Aug 2024): Third and final development flight — successful. ISRO declared SSLV development complete after D3. Technology now transferred to HAL.
SSLV-D2 (Feb 2023): Successful. Launched EOS-07 (ISRO) + Janus-1 (US startup Antaris) + AzaadiSAT-2 (Chennai's Space Kidz India).
SSLV-D3 (Aug 2024): Third and final development flight — successful. ISRO declared SSLV development complete after D3. Technology now transferred to HAL.
Sounding Rockets — India's Space Programme Pioneers
🔭 Sounding Rockets — Where India's Space Journey Began
First sounding rocket: Nike-Apache (American), launched November 21, 1963 from Thumba Equatorial Rocket Launching Station (TERLS), Thiruvananthapuram — marking the official beginning of India's space programme. The location was chosen because it lies near the Earth's magnetic equator — ideal for atmospheric studies.
Rohini Sounding Rocket (RSR) Programme (1975): Consolidated all sounding rocket activities. Currently 3 operational versions with payloads from 8 to 100 kg and altitudes from 80 to 475 km. Unlike orbital rockets, sounding rockets are sub-orbital — they go up and come back down (no orbit). Used for: upper atmosphere research, ionospheric studies, microgravity experiments, student experiments. India now launches indigenously built sounding rockets from 1965 onwards.
Rohini Sounding Rocket (RSR) Programme (1975): Consolidated all sounding rocket activities. Currently 3 operational versions with payloads from 8 to 100 kg and altitudes from 80 to 475 km. Unlike orbital rockets, sounding rockets are sub-orbital — they go up and come back down (no orbit). Used for: upper atmosphere research, ionospheric studies, microgravity experiments, student experiments. India now launches indigenously built sounding rockets from 1965 onwards.
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Launch Vehicles Under Development
HLVM3 · RLV · Scramjet · NGLV/Project Soorya
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HLVM3 — Human-Rated LVM3 (Gaganyaan Vehicle)
LVM3 upgraded for human spaceflight. Every component tested at 1.5× rated load for safety. Additions: Crew Escape System (CES) — high-burn solid motors that pull the crew capsule away from the rocket in emergencies within milliseconds. CE-20 engine human-rated (Feb 2024). Gaganyaan-G1 (uncrewed test) campaign started 2025. Gaganyaan-G4 crewed mission: 2026 — India = 4th country to independently launch humans to space.
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RLV — Reusable Launch Vehicle Technology Demonstrator
Winged, aircraft-like vehicle that can re-enter and land autonomously (like Space Shuttle concept). Programme milestones:
RLV-TD HEX-01 (May 2016): First atmospheric re-entry test (sub-orbital).
RLV-LEX-02 (Mar 2024): Autonomous runway landing from helicopter-drop — successful.
RLV-LEX-03 (Jun 2024): More challenging conditions — successful.
Future: RLV will be scaled up as the reusable first stage of India's two-stage orbital launch vehicle — drastically reducing launch costs.
RLV-TD HEX-01 (May 2016): First atmospheric re-entry test (sub-orbital).
RLV-LEX-02 (Mar 2024): Autonomous runway landing from helicopter-drop — successful.
RLV-LEX-03 (Jun 2024): More challenging conditions — successful.
Future: RLV will be scaled up as the reusable first stage of India's two-stage orbital launch vehicle — drastically reducing launch costs.
⭐ NGLV / Project Soorya — India's Future Super-Rocket Cabinet Approved Sep 2024
Cabinet approval: September 18, 2024. Budget: ₹8,240 crore (~$970 million). Timeline: 96 months (8 years) → target: 2032–2033.
Official name: Next Generation Launch Vehicle (NGLV). Project name: "Soorya" (Sun). Third Launch Pad (TLP) at Sriharikota: Cabinet approved January 16, 2025 — to be built specifically for NGLV.
Specifications:
🎯 Payload to LEO: 30,000 kg (3× more than current LVM3's 10,000 kg)
💰 Cost: Only 1.5× more than LVM3 despite 3× payload capacity
♻ Partially reusable first stage — can be reused 15–20 times
⛽ Semi-cryogenic propulsion — refined kerosene + liquid oxygen (LOX) for booster stages
🏭 Industry-led: Private sector manufactures and launches from day one
🚀 3 developmental flights (D1, D2, D3) planned
Missions it will enable: Bharatiya Antariksh Station (BAS, 2035) assembly · Indian crewed Moon landing (2040) · Heavy commercial GEO satellites · Deep space missions (Mars-2, Venus) · Deployment of mega-constellations
Official name: Next Generation Launch Vehicle (NGLV). Project name: "Soorya" (Sun). Third Launch Pad (TLP) at Sriharikota: Cabinet approved January 16, 2025 — to be built specifically for NGLV.
Specifications:
🎯 Payload to LEO: 30,000 kg (3× more than current LVM3's 10,000 kg)
💰 Cost: Only 1.5× more than LVM3 despite 3× payload capacity
♻ Partially reusable first stage — can be reused 15–20 times
⛽ Semi-cryogenic propulsion — refined kerosene + liquid oxygen (LOX) for booster stages
🏭 Industry-led: Private sector manufactures and launches from day one
🚀 3 developmental flights (D1, D2, D3) planned
Missions it will enable: Bharatiya Antariksh Station (BAS, 2035) assembly · Indian crewed Moon landing (2040) · Heavy commercial GEO satellites · Deep space missions (Mars-2, Venus) · Deployment of mega-constellations
🔥 Scramjet Engine — India Becomes 4th Country (2016)
A scramjet (supersonic combustion ramjet) uses atmospheric oxygen (no onboard oxidiser) + hydrogen fuel for hypersonic speeds (Mach 5+). Unlike rocket engines that carry oxygen, air-breathing engines are much lighter and efficient. First experimental Scramjet flight by ISRO: August 28, 2016 — making India the 4th country (after USA, Russia, China) to demonstrate scramjet flight. Applications: future air-breathing upper stages that reduce payload weight for orbital missions.
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Private Sector Launch Vehicles — India's New Space Era
Skyroot · Agnikul · SSLV-HAL Transfer · IN-SPACe
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Skyroot Aerospace — Vikram-S (Nov 2022)
India's FIRST private rocket launch — Vikram-S sub-orbital test (November 18, 2022). Named after Dr. Vikram Sarabhai. 3D-printed engine components reduce cost. Now developing Vikram-1 (orbital). Backed by private venture capital.
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Agnikul Cosmos — AgniLet (Mar 2024)
World's first flight of a fully 3D-printed rocket engine — SoRTeD-01 launched March 21, 2024 from India's first private launch pad at Sriharikota. AgniLet = world's first single-piece 3D-printed semi-cryogenic engine. Sub-orbital test.
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HAL — SSLV Production (Sep 2025)
HAL won ₹511 crore bid for full SSLV technology from ISRO. First company to receive complete launch vehicle technology from ISRO. Will independently build, own, and commercialise SSLVs. 6–10 rockets/year capacity planned. India's 100th space tech transfer agreement.
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IN-SPACe + Indian Space Policy 2023
IN-SPACe = single-window regulator + promoter for private space. Indian Space Policy 2023 + 100% FDI = opened floodgates. From 3–4 space startups before 2020 → 330+ space startups by 2025. 450+ Indian industries work with ISRO. Target: 50 launches/year.
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PSLV Production — HAL+L&T Consortium
ISRO awarded contract for 5 PSLVs to HAL+L&T consortium. ISRO transferring 50% of PSLV development work to private companies (ISRO Chairman Narayanan, 2025). 80–85% of PSLV components already made by Indian industries (e.g., HCL made 32-bit ISRO computer processor).
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NSIL — NewSpace India Limited
ISRO's commercial arm. Handles: commercial satellite launches for foreign customers, GSAT satellite production, technology transfer agreements (100th ToT = SSLV to HAL, Sep 2025). Launched AST SpaceMobile satellite (US) in 2025. India's route to capturing global commercial launch market.
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Complete Launch Vehicle Comparison Table
All ISRO Vehicles · Specs · Status · Famous Missions
| Vehicle | Status | Height | Liftoff Mass | Stages | Payload (LEO) | Payload (GTO) | Key Missions |
|---|---|---|---|---|---|---|---|
| SLV-3 | 🔴 Retired (1983) | 21.5 m | 17 t | 4 solid | 40 kg | — | Rohini RS-1 (1980) — India's 6th orbital launch nation |
| ASLV | 🔴 Retired (1994) | 23.6 m | 40 t | 5 solid | 150 kg | — | SROSS-C2 (1994). Technology testbed for PSLV. |
| PSLV-CA | 🟢 Active | 44.4 m | 230 t | 4 (S+L+S+L) | 3,200 kg | 1,100 kg | Chandrayaan-1, Mangalyaan, Aditya-L1, SpaDeX |
| PSLV-XL | 🟢 Active | 44.4 m | 320 t | 4 + 6 strap-ons | 3,800 kg | 1,425 kg | 104 satellites (2017 record), IRNSS/NaVIC constellation |
| GSLV Mk II | 🟢 Active | 51.7 m | 420 t | 3 (S+L+Cryo) | 6,000 kg | 2,500 kg | Chandrayaan-2, INSAT-3DS, NVS-02 (ISRO 100th mission) |
| LVM3 | 🟢 Active | 43.5 m | 640 t | 3 (2S+L+Cryo) | 10,000 kg | 4,000 kg | Chandrayaan-3, OneWeb (36+36 sats), Gaganyaan (HLVM3) |
| SSLV | 🟢 Active → ToT to HAL | 34 m | 120 t | 3 solid + VTM | 500 kg (500km) | — | EOS-07, AzaadiSAT-2. HAL ToT signed Sep 2025. |
| HLVM3 | 🔵 Under Dev | 43.5 m | 640 t | Same as LVM3 + CES | 10,000 kg | — | Gaganyaan-G4 (crewed, 2026) — 3 astronauts, 400 km LEO |
| NGLV "Soorya" | 🔵 Approved (Sep 2024) | TBD (~60m+) | ~600 t | 3 semi-cryo + cryo | 30,000 kg | 10,000 kg | BAS (2035), Moon mission (2040). ₹8,240 cr. 2032 target. |
| RLV | 🔵 Under Dev | ~6.5 m (winged) | ~1.75 t | Winged reusable | Future orbital | — | RLV-LEX-02 (Mar 2024), RLV-LEX-03 (Jun 2024) — autonomous landing demonstrated |
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UPSC PYQs — Launch Vehicles
Actual Questions · Verified Answers
⭐ UPSC Prelims — PSLV vs GSLV Core DifferenceRepeated Pattern
With reference to India's satellite launch vehicles, consider the following statements:
1. PSLV uses a cryogenic upper stage to place heavy satellites in geostationary transfer orbit.
2. GSLV uses an indigenous cryogenic upper stage developed by ISRO.
3. LVM3 (formerly GSLV Mk III) is currently India's most powerful operational launch vehicle.
1. PSLV uses a cryogenic upper stage to place heavy satellites in geostationary transfer orbit.
2. GSLV uses an indigenous cryogenic upper stage developed by ISRO.
3. LVM3 (formerly GSLV Mk III) is currently India's most powerful operational launch vehicle.
- (a) 1 and 2 only
- (b) 2 and 3 only ✅
- (c) 1 and 3 only
- (d) 1, 2 and 3
Statement 1 ✗ WRONG: PSLV does NOT use a cryogenic stage. PSLV uses 4 stages: solid → liquid (Vikas) → solid → liquid (earth-storable). No cryogenic stage at all. PSLV's strength is SSO/LEO missions at lower altitudes, not GTO. GTO missions need cryogenic upper stages (GSLV, LVM3).
Statement 2 ✅ Correct: GSLV uses the CE-7.5 Indigenous Cryogenic Engine (upper stage). Russia denied cryogenic technology in 1990s under US pressure (MTCR). ISRO developed CE-7.5 independently over ~20 years. GSLV Mk II uses this indigenous CE-7.5.
Statement 3 ✅ Correct: LVM3 = most powerful operational rocket: 10,000 kg to LEO, 4,000 kg to GTO. Previously called GSLV Mk III. Uses CE-20 cryogenic engine. NGLV (30,000 kg) is under development (approved Sep 2024) but not operational.
Statement 2 ✅ Correct: GSLV uses the CE-7.5 Indigenous Cryogenic Engine (upper stage). Russia denied cryogenic technology in 1990s under US pressure (MTCR). ISRO developed CE-7.5 independently over ~20 years. GSLV Mk II uses this indigenous CE-7.5.
Statement 3 ✅ Correct: LVM3 = most powerful operational rocket: 10,000 kg to LEO, 4,000 kg to GTO. Previously called GSLV Mk III. Uses CE-20 cryogenic engine. NGLV (30,000 kg) is under development (approved Sep 2024) but not operational.
⭐ UPSC Prelims — SSLV & Private SectorCurrent Affairs 2025
Consider the following about India's Small Satellite Launch Vehicle (SSLV):
1. SSLV is a three-stage vehicle with all three stages using solid propulsion.
2. SSLV technology has been transferred to HAL making it the first complete launch vehicle technology transfer by ISRO to a private/public sector company.
3. SSLV can launch payloads of up to 500 kg to Low Earth Orbit.
1. SSLV is a three-stage vehicle with all three stages using solid propulsion.
2. SSLV technology has been transferred to HAL making it the first complete launch vehicle technology transfer by ISRO to a private/public sector company.
3. SSLV can launch payloads of up to 500 kg to Low Earth Orbit.
- (a) 1 and 2 only
- (b) 1 and 3 only
- (c) 2 and 3 only ✅
- (d) 1, 2 and 3
Statement 1 ✗ WRONG: SSLV has THREE solid stages + ONE liquid terminal stage called the Velocity Trimming Module (VTM). The VTM is a liquid propulsion terminal stage that allows precise orbit insertion. So it's 3 solid + 1 liquid = 4 stages total, NOT 3 all-solid.
Statement 2 ✅ Correct: September 10, 2025 — ISRO, NSIL, IN-SPACe signed SSLV technology transfer agreement with HAL. HAL won the competitive bid at ₹511 crore. First-ever complete launch vehicle technology transferred from ISRO to any company. India's 100th space technology transfer agreement under Department of Space.
Statement 3 ✅ Correct: SSLV payload to 500 km LEO = 500 kg. To 500 km SSO = 300 kg. Designed for nano/micro/mini satellite market.
Statement 2 ✅ Correct: September 10, 2025 — ISRO, NSIL, IN-SPACe signed SSLV technology transfer agreement with HAL. HAL won the competitive bid at ₹511 crore. First-ever complete launch vehicle technology transferred from ISRO to any company. India's 100th space technology transfer agreement under Department of Space.
Statement 3 ✅ Correct: SSLV payload to 500 km LEO = 500 kg. To 500 km SSO = 300 kg. Designed for nano/micro/mini satellite market.
⭐ Expected Mains 2026 — India's Launch Vehicle Programme250 Words | 15 Marks
"India's satellite launch vehicle programme reflects both its growing space ambitions and its efforts to commercialise space. Critically analyse the evolution of ISRO's launch vehicles and the significance of recent developments."
Evolution (Brief): SLV-3 (1980, 40kg, 6th country) → ASLV (1987, 150kg) → PSLV (1994, 3800kg, workhorse, 104 satellites 2017) → GSLV Mk II (indigenous cryogenic CE-7.5) → LVM3 (10t LEO, Chandrayaan-3, OneWeb) → SSLV (500kg, rapid deployment, HAL ToT Sep 2025) → NGLV (30t LEO, approved Sep 2024, ₹8240 cr, 2032).
Key Current Milestones: SSLV-D3 completed (Aug 2024) → SSLV development complete → HAL ToT (₹511 cr, Sep 2025, India's 100th space ToT). NGLV/Project Soorya Cabinet approval (Sep 2024) — 30t payload, partially reusable, semi-cryo. Third Launch Pad (Sriharikota) approved Jan 2025. RLV-LEX-02 (Mar 2024) and LEX-03 (Jun 2024) — autonomous landing. HLVM3/Gaganyaan-G4 crewed planned 2026. PSLV 50% development to private sector. 330+ startups. Skyroot Vikram-S (Nov 2022). Agnikul SoRTeD-01 (Mar 2024 — world's first 3D-printed engine flight).
Significance: Commercialisation: ISRO revenue through OneWeb, foreign satellite launches. Private sector: ToT builds indigenous capacity → 50 launches/year target. Strategic: self-reliance, no dependence on foreign rockets. Future missions: BAS (2035), Moon (2040) require NGLV's 30t capacity. Geopolitical: commercial launch = diplomatic leverage. Economy: India aims for $44B space economy by 2033.
Key Current Milestones: SSLV-D3 completed (Aug 2024) → SSLV development complete → HAL ToT (₹511 cr, Sep 2025, India's 100th space ToT). NGLV/Project Soorya Cabinet approval (Sep 2024) — 30t payload, partially reusable, semi-cryo. Third Launch Pad (Sriharikota) approved Jan 2025. RLV-LEX-02 (Mar 2024) and LEX-03 (Jun 2024) — autonomous landing. HLVM3/Gaganyaan-G4 crewed planned 2026. PSLV 50% development to private sector. 330+ startups. Skyroot Vikram-S (Nov 2022). Agnikul SoRTeD-01 (Mar 2024 — world's first 3D-printed engine flight).
Significance: Commercialisation: ISRO revenue through OneWeb, foreign satellite launches. Private sector: ToT builds indigenous capacity → 50 launches/year target. Strategic: self-reliance, no dependence on foreign rockets. Future missions: BAS (2035), Moon (2040) require NGLV's 30t capacity. Geopolitical: commercial launch = diplomatic leverage. Economy: India aims for $44B space economy by 2033.
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Practice MCQs — Launch Vehicles
10 Questions · Click to Attempt
📝 10 MCQs — All Key Concepts + Current Affairs 2024–26
Q1. Why is PSLV called the "Workhorse of ISRO" despite not being the most powerful rocket?
- (a) PSLV is the most powerful rocket and that is why it is called the workhorse
- (b) PSLV has the highest reliability record, most launches, handles the widest variety of missions (SSO, LEO, GTO, multiple orbits), and has enabled India's most iconic missions — making it the go-to vehicle for most ISRO launches ✅
- (c) PSLV is the cheapest rocket to manufacture and therefore used for all routine missions
- (d) PSLV uses cryogenic engines which give it superior performance for all orbit types
✅ (b). PSLV = "Workhorse" because of reliability and versatility, not size. Key points: (1) Over 50 consecutive successful missions — highest reliability record of any Indian rocket. (2) Launched India's most iconic missions: Chandrayaan-1, Mangalyaan, Aditya-L1, SpaDeX. (3) Can reach multiple orbits: SSO (primary), LEO, GTO, sub-GTO, lunar transfer orbit. (4) World record: 104 satellites in one launch (Feb 2017). (5) PSLV-XL is the standard workhouse; CA, DL, QL variants for different payload needs. LVM3 is more powerful (10t vs 3.8t to LEO) but PSLV has far more launches. PSLV does NOT use cryogenic stages (option d is wrong) — 4-stage solid-liquid-solid-liquid.
Q2. What is the significance of the SSLV-HAL technology transfer agreement of September 2025?
- (a) It marks the first time any foreign company has acquired Indian rocket technology
- (b) HAL will manufacture PSLV rockets for commercial satellite launches
- (c) It is the first time ISRO has transferred complete launch vehicle technology to any Indian company — HAL (winning ₹511 crore bid) will independently build, own, and commercialise SSLV launches, with India's 100th space technology transfer ✅
- (d) The agreement transfers LVM3 technology to HAL for manufacturing Gaganyaan rockets
✅ (c). SSLV-HAL Technology Transfer Agreement (September 10, 2025): Signed by ISRO, NSIL, IN-SPACe, and HAL. First-ever COMPLETE launch vehicle technology transfer by ISRO to any company. HAL won through a national competitive bidding process managed by IN-SPACe with a ₹511 crore (~$59.7 million) bid. Significance: (1) HAL independently builds, owns, and commercialises SSLVs — not just manufacturing for ISRO. (2) Target: 6–10 SSLVs per year. (3) India's 100th Space Technology Transfer under Department of Space. (4) 24-month transfer period with ISRO training. (5) Aims to establish India as global hub for small satellite launches in the growing commercial market (projected $44B Indian space economy by 2033). The SSLV development was declared complete after SSLV-D3's successful launch in August 2024.
Q3. The cryogenic engine CE-20 used in LVM3 is superior to the CE-7.5 in GSLV Mk II primarily because:
- (a) CE-20 generates nearly 3× more thrust (~200 kN vs ~73.5 kN), is throttleable for in-flight adjustment, and has been human-rated for the Gaganyaan mission ✅
- (b) CE-20 uses liquid methane instead of liquid hydrogen, making it cheaper and easier to handle
- (c) CE-20 is reusable and can be recovered after each flight, unlike the expendable CE-7.5
- (d) CE-20 is a foreign engine imported from Russia, while CE-7.5 is domestically developed
✅ (a). CE-20 vs CE-7.5 comparison: CE-20 thrust = ~200 kN; CE-7.5 = ~73.5 kN — CE-20 is ~2.7× more powerful. Both use liquid hydrogen (LH₂) + liquid oxygen (LOX) — NOT methane (option b is wrong). CE-20 is throttleable (can adjust thrust from 67% to 104% rated thrust) — valuable for precise orbit insertion and Gaganyaan's human spaceflight needs. CE-20 was human-rated in February 2024 — qualifying it for Gaganyaan. CE-20 enables LVM3 to carry 10,000 kg to LEO and 4,000 kg to GTO. Both CE-7.5 and CE-20 are completely indigenous — India developed both after Russia denied cryogenic technology in the 1990s (option d wrong). Neither is currently reusable (option c wrong), though NGLV's future cryo stage may be reusable.
Q4. What is the NGLV (Next Generation Launch Vehicle), also called "Project Soorya"?
- (a) India's first crewed Moon landing rocket, a single-use super-heavy lift vehicle to be launched by 2030
- (b) A small satellite launch vehicle being developed to compete with Elon Musk's Starship
- (c) A replacement for PSLV that will use cryogenic engines throughout all stages
- (d) A 3-stage, partially reusable heavy-lift rocket approved by Cabinet in September 2024 with ₹8,240 crore budget, capable of carrying 30,000 kg to LEO — 3× more than LVM3 — to enable BAS and Moon missions by 2040 ✅
✅ (d). NGLV (Next Generation Launch Vehicle) / Project Soorya: Cabinet approval September 18, 2024. Budget: ₹8,240 crore (~$970 million). Timeline: 96 months (8 years) → target 2032. 3 developmental flights (D1, D2, D3). Payload: 30,000 kg to LEO (vs LVM3's 10,000 kg — 3× more) and up to 10,000 kg to GTO. Partially reusable: first stage recoverable and reusable 15–20 times (like SpaceX Falcon 9 concept). Propulsion: Semi-cryogenic (refined kerosene + LOX) for lower stages — cheaper than cryogenic. Industry-led from day one. Third Launch Pad at Sriharikota approved separately (January 2025) for NGLV. Will enable: Bharatiya Antariksh Station (2035), Indian crewed Moon landing (2040), heavy commercial satellites. Previously called Unified Launch Vehicle (ULV).
Q5. India became the 4th country to demonstrate Scramjet engine flight in 2016. A scramjet is different from a conventional rocket engine because:
- (a) A scramjet uses nuclear energy for propulsion rather than chemical combustion
- (b) A scramjet uses atmospheric oxygen as oxidiser (no onboard oxygen needed) and achieves supersonic combustion at Mach 5+ speeds — making it lighter and more efficient for hypersonic flight ✅
- (c) A scramjet can be reused indefinitely unlike conventional solid or liquid rocket stages
- (d) A scramjet uses water as fuel and produces zero emissions, making it environmentally friendly
✅ (b). Scramjet (Supersonic Combustion Ramjet): Air-breathing engine — uses atmospheric oxygen, not onboard oxygen. This removes the need to carry heavy liquid oxygen, significantly reducing the vehicle's total mass. Combustion happens at supersonic speeds (Mach 5+) — unlike a ramjet which has subsonic combustion. Fuel: hydrogen. Works only at hypersonic speeds (Mach 5+) — cannot generate static thrust (can't start from standstill). ISRO's first Scramjet flight: August 28, 2016 — making India the 4th country after USA, Russia, China. Applications for future launch vehicles: air-breathing upper stages that save propellant mass, increasing payload capacity. Future "two-stage to orbit" concepts use scramjet as first stage + conventional rocket second stage. Not nuclear (option a). Not infinitely reusable by definition (option c). Not water-fuelled (option d) — hydrogen fuel.
Q6. Why is a multi-stage rocket design more efficient than a single-stage rocket for reaching orbit?
- (a) Multi-stage rockets are heavier, which provides more inertia for breaking through Earth's atmosphere
- (b) Multi-stage rockets can use different fuels in different stages, reducing cost
- (c) Each spent stage (empty tanks and engines) is discarded as dead weight — so subsequent stages only need to accelerate a lighter vehicle, achieving much higher final velocities with the same total propellant ✅
- (d) Multi-stage rockets have better aerodynamic shape, reducing air resistance throughout flight
✅ (c). Multi-stage efficiency is governed by the Tsiolkovsky Rocket Equation: final velocity depends on the mass ratio (starting mass / ending mass). Problem with single-stage: empty tanks and engines are dead weight that must be carried all the way to orbit. Solution: staging — as each stage burns out, its empty structure is jettisoned. Each successive stage starts fresh with only useful remaining mass. Analogy: hiking a mountain and leaving heavy camping gear at each base camp — you're lighter at each level. PSLV has 4 stages — each burns out and drops away. The final payload (satellite) is just a small fraction of liftoff mass. LVM3: liftoff 640 tonnes; satellite payload: 4–10 tonnes. The empty structure and propellant consumed accounts for ~99% of liftoff mass. Option (b): different fuels CAN be used (PSLV does this — solid-liquid-solid-liquid) but the efficiency gain is primarily from mass reduction, not fuel variety.
Q7. India's PSLV launched 104 satellites in a single mission in 2017. Most of these satellites belonged to which country?
- (a) USA — 96 American nanosatellites plus 1 each from Netherlands, Switzerland, Israel, Kazakhstan, UAE = 101 foreign satellites + 3 Indian satellites = 104 total ✅
- (b) Russia — 80 Russian military nanosatellites used the mission to covertly test surveillance technology
- (c) China — commercial imaging constellation deployment on Indian rocket for cost savings
- (d) The 104 satellites were all Indian — demonstrating India's indigenous constellation capability
✅ (a). PSLV-C37 (February 15, 2017): Launched 104 satellites in a single flight — then a world record (breaking Russia's record of 37). Breakdown: 3 Indian satellites (Cartosat-2D + INS-1A + INS-1B) + 101 foreign satellites: 96 from USA + 1 each from Netherlands, Switzerland, Israel, Kazakhstan, UAE. Primary payload: Cartosat-2D (Earth observation, 714 kg). 103 co-passengers: nanosatellites (Dove satellites from Planet Labs, USA — imaging constellation). Total satellite mass: 1,378 kg. Launch: PSLV-C37 from Sriharikota at 9:28 AM IST. All satellites deployed into 505 km SSO within 11 minutes of lift-off. This record was later surpassed by SpaceX (143 satellites on Transporter-1 in 2021), but the PSLV-C37 record for government space agencies still stands.
Q8. What is the Velocity Trimming Module (VTM) in SSLV, and why is it important?
- (a) VTM is the aerodynamic fin system that keeps the rocket stable during atmospheric ascent
- (b) VTM is SSLV's onboard computer system that trims navigation errors in real time
- (c) VTM is an optional fourth solid rocket booster that increases payload by 50% when attached
- (d) VTM is a liquid propulsion terminal stage that precisely adjusts SSLV's velocity for accurate orbit insertion — correcting any inaccuracies from the three solid stages above which cannot be throttled or restarted ✅
✅ (d). Velocity Trimming Module (VTM): SSLV's 4th stage. A liquid propulsion terminal stage using thrusters for precise orbit insertion. Why needed: Solid rocket stages cannot be throttled or shut off mid-burn — they burn completely once ignited. This means the spacecraft arrives at roughly the right orbit but with residual velocity errors. The VTM (liquid, restartable) then makes fine adjustments to achieve the precise target orbit. Critically, the VTM enables SSLV's "multiple orbit" capability — it can insert multiple satellites into different orbital planes in a single mission (a key commercial advantage). Without VTM: SSLV would have insertion accuracy problems. Recall: SSLV-D1 failure was because vibration affected sensors during stage separation, causing the orbit to be circular at wrong altitude. VTM worked correctly in D1 but orbital altitude was wrong due to guidance error. D2 and D3 were successful with VTM functioning as designed.
Q9. The RLV-LEX-02 and RLV-LEX-03 experiments conducted by ISRO in 2024 demonstrated which specific capability?
- (a) India's first successful orbital launch from a sea-based mobile platform
- (b) Autonomous runway landing of a winged reusable launch vehicle after release from a helicopter — demonstrating India's indigenous capability for returning a spacecraft to land like an aircraft ✅
- (c) Supersonic combustion in a scramjet engine at Mach 7 — doubling ISRO's previous record
- (d) Propulsive landing (vertical, tail-first) similar to SpaceX Falcon 9's booster recovery
✅ (b). RLV-LEX (Landing Experiment): ISRO's Reusable Launch Vehicle experiments to demonstrate autonomous runway landing. Method: A winged RLV-TD (shaped like a mini Space Shuttle) is carried to ~4.5 km altitude by a Chinook helicopter, released, and must autonomously navigate, glide, and land precisely on a 1.75 km airstrip. RLV-LEX-02 (March 22, 2024): Conducted from IAF Chitradurga, Karnataka. More challenging conditions than LEX-01 (2023) — higher drop speed and more severe crosswind. Success. RLV-LEX-03 (June 7, 2024): Further challenging release conditions — maximum demonstrated crosswind landing. Success. Significance: Validates the autonomous landing guidance system (ALDN) critical for future two-stage orbital vehicle where the first stage glides back to land. Different from SpaceX Falcon 9 which lands vertically on legs using engine thrust (option d) — ISRO's RLV uses runway landing like a conventional aircraft/Space Shuttle.
Q10. Which of the following correctly matches a launch vehicle with its unique distinguishing feature?
- (a) SSLV → 72-hour assembly time, 3 solid + VTM (liquid), 500 kg to LEO, HAL ToT Sep 2025; GSLV Mk II → Indigenous CE-7.5 cryogenic upper stage; LVM3 → CE-20 cryogenic, 10t to LEO, Chandrayaan-3 ✅
- (b) PSLV → cryogenic upper stage for GTO missions; GSLV → all-solid vehicle with no liquid stages; LVM3 → carries crew for Gaganyaan without any modification
- (c) SLV-3 → India's current workhorse replacing PSLV; ASLV → India's heaviest rocket at 640 tonnes; SSLV → longest standing rocket at 91m height
- (d) NGLV → already operational and conducted its first launch in 2024; SSLV → uses cryogenic propulsion throughout; GSLV → launched India's first satellite Aryabhata
✅ (a). All three matches in option (a) are correct: SSLV: 3 solid stages + VTM liquid terminal stage. Assembly in ~72 hours (rapid deployment). 500 kg to 500 km LEO. HAL Technology Transfer signed September 10, 2025 (₹511 crore). India's 100th space ToT. GSLV Mk II: Defining feature = indigenous CE-7.5 cryogenic upper stage (developed after Russia denied technology). 3 stages: solid S139 + 4 liquid strap-ons / Vikas / CE-7.5 cryogenic. Used for Chandrayaan-2, INSAT/GSAT communication satellites. LVM3: CE-20 cryogenic (200 kN, ~3× CE-7.5). 10,000 kg to LEO. Used for Chandrayaan-3, OneWeb commercial launches. Option (b) wrong: PSLV has NO cryogenic stage; GSLV uses liquid+cryogenic (not all-solid); LVM3 for Gaganyaan requires HLVM3 upgrade with Crew Escape System. Options (c) and (d) contain multiple factual errors.
⚡ Quick Revision — All Launch Vehicles at a Glance
| Vehicle | Status | Stages | Max LEO Payload | Key Distinction |
|---|---|---|---|---|
| SLV-3 | 🔴 Retired 1983 | 4 solid | 40 kg | India's FIRST launch vehicle. Dr. Kalam led. July 1980 = India 6th country. 21.5m height. |
| ASLV | 🔴 Retired 1994 | 5 solid | 150 kg | Bridge to PSLV. Tested strap-on tech. 4 flights, 2 successes. 23.6m. |
| PSLV-XL | 🟢 Active → 50% to private | 4 (S-L-S-L) + 6 strap-ons | 3,800 kg | "Workhorse." 50+ consecutive successes. 104 sats (2017 record). Chandrayaan-1, MOM, Aditya-L1, SpaDeX. |
| GSLV Mk II | 🟢 Active | 3 (S+L+Cryo CE-7.5) | 6,000 kg | India's first indigenous cryogenic engine (CE-7.5). GTO specialist. Chandrayaan-2, NVS-02. |
| LVM3 | 🟢 Active (most powerful) | 3 (2S strap-ons + L + Cryo CE-20) | 10,000 kg | CE-20 (200 kN). Chandrayaan-3, OneWeb. HLVM3 = Gaganyaan vehicle. |
| SSLV | 🟢 Active → ToT to HAL (Sep 2025) | 3 solid + VTM liquid | 500 kg | 72-hr assembly, rapid deploy. First ever launch vehicle ToT by ISRO. ₹511 cr. HAL 6-10/year. |
| HLVM3 | 🔵 Under dev (Gaganyaan) | Same as LVM3 + CES | 10,000 kg | Human-rated LVM3 + Crew Escape System. CE-20 human-rated Feb 2024. Gaganyaan-G4 crewed: 2026. |
| NGLV "Soorya" | 🔵 Cabinet approved Sep 2024 | 3 semi-cryo | 30,000 kg | ₹8,240 cr. 3× LVM3 at 1.5× cost. Partially reusable 1st stage. 2032 target. Enables BAS+Moon 2040. |
🚨 5 UPSC Traps — Launch Vehicles:
Trap 1 — "PSLV uses cryogenic engine" → WRONG! PSLV has NO cryogenic stage. It uses 4 stages: Stage 1 (solid S139) → Stage 2 (Vikas liquid) → Stage 3 (solid S7) → Stage 4 (liquid PS4). Only GSLV Mk II (CE-7.5) and LVM3 (CE-20) use cryogenic stages.
Trap 2 — "SSLV is a 3-stage all-solid vehicle" → WRONG! SSLV has THREE solid stages + ONE liquid terminal stage (VTM = Velocity Trimming Module). The VTM makes precise orbit insertion possible — solid stages alone cannot throttle or restart. So SSLV = 3 solid + 1 liquid = 4 total stages.
Trap 3 — "GSLV Mk III / LVM3 is under development" → WRONG! LVM3 is fully OPERATIONAL. It launched Chandrayaan-3 (Aug 2023), OneWeb satellites (2022-23). NGLV (30t capacity) is what's under development (Cabinet approved Sep 2024, target 2032). Don't confuse LVM3 (operational) with NGLV (under development).
Trap 4 — "SLV-3 made India the 7th country to launch a satellite" → WRONG! SLV-3 made India the 6th member of the exclusive club of space-faring nations (per ISRO's official VSSC page). The July 18, 1980 launch of Rohini RS-1 via SLV-3 from Sriharikota achieved this. (Some sources say 7th — ISRO's own VSSC page says 6th.)
Trap 5 — "The SSLV-HAL deal gives HAL manufacturing rights only" → WRONG! HAL gets COMPLETE ownership: right to build, OWN, modify the design, and COMMERCIALISE SSLV launches independently. This is different from previous HAL work (which manufactured PSLV/GSLV components FOR ISRO). The SSLV ToT transfers full intellectual property and operational rights to HAL.
Trap 1 — "PSLV uses cryogenic engine" → WRONG! PSLV has NO cryogenic stage. It uses 4 stages: Stage 1 (solid S139) → Stage 2 (Vikas liquid) → Stage 3 (solid S7) → Stage 4 (liquid PS4). Only GSLV Mk II (CE-7.5) and LVM3 (CE-20) use cryogenic stages.
Trap 2 — "SSLV is a 3-stage all-solid vehicle" → WRONG! SSLV has THREE solid stages + ONE liquid terminal stage (VTM = Velocity Trimming Module). The VTM makes precise orbit insertion possible — solid stages alone cannot throttle or restart. So SSLV = 3 solid + 1 liquid = 4 total stages.
Trap 3 — "GSLV Mk III / LVM3 is under development" → WRONG! LVM3 is fully OPERATIONAL. It launched Chandrayaan-3 (Aug 2023), OneWeb satellites (2022-23). NGLV (30t capacity) is what's under development (Cabinet approved Sep 2024, target 2032). Don't confuse LVM3 (operational) with NGLV (under development).
Trap 4 — "SLV-3 made India the 7th country to launch a satellite" → WRONG! SLV-3 made India the 6th member of the exclusive club of space-faring nations (per ISRO's official VSSC page). The July 18, 1980 launch of Rohini RS-1 via SLV-3 from Sriharikota achieved this. (Some sources say 7th — ISRO's own VSSC page says 6th.)
Trap 5 — "The SSLV-HAL deal gives HAL manufacturing rights only" → WRONG! HAL gets COMPLETE ownership: right to build, OWN, modify the design, and COMMERCIALISE SSLV launches independently. This is different from previous HAL work (which manufactured PSLV/GSLV components FOR ISRO). The SSLV ToT transfers full intellectual property and operational rights to HAL.
