India's Launch Vehicle Technology

India's space program has seen significant evolution in its launch vehicle technology, enabling the country to achieve self-reliance in space access.

What is a Launch Vehicle?

A launch vehicle, also known as a rocket, is a transportation system designed to carry a payload (satellites, spacecraft, or humans) from Earth’s surface into space. It provides the necessary velocity and altitude to overcome Earth's gravity. Once near the intended orbit, satellites are ejected.

Evolution of ISRO's Launch Vehicles

India's launch vehicle development began in 1969 under Dr. Vikram Sarabhai, with the vision of achieving self-reliance in space technology.

• Early Beginnings (1960s): Started with sounding rockets. The first sounding rocket, Nike-Apache, was launched from Thumba, Kerala, in 1963, marking the program's start.
• 1970s: Developed SLV and ASLV launch vehicles.
• 1980s: SLV-3 made India the 6th or 7th nation to independently reach Earth orbit.
• 1990s: PSLV development began, and GSLV was conceived for geostationary orbit.
• 2000s: LVM3 (GSLV Mk III) development started for heavier satellites.
• 2010s: ISRO launched the Reusable Launch Vehicle Technology Demonstrator (RLV-TD) in 2016.
• 2020s: SSLV (Small Satellite Launch Vehicle) was developed for small satellites, and the Next-Gen Launch Vehicle (NGLV) is planned to replace existing rockets.

Types of Indian Launch Vehicles

Satellite Launch Vehicle (SLV)

• First-generation launch vehicle.
• Developed under the leadership of Dr. A.P.J. Abdul Kalam.
• First experimental flight: August 1979 (partially successful).
• First successful launch: SLV-3 on July 18, 1980, which placed the Rohini (RS-1) satellite into orbit. This achievement made India the sixth country to launch its own satellites.
• Structure: Four-stage, solid-propellant rocket.
• Capacity: Capable of placing a 40 kg class payload into Low Earth Orbit (LEO) up to 400 km.
• Significance: Made India self-reliant in indigenous launch technology.

Augmented Satellite Launch Vehicle (ASLV)

• Second-generation launch vehicle.
• Developed to augment the payload capacity of SLV.
• Operating period: Used between 1987 and 1994.
• Structure: Five-stage, all-solid propellant vehicle, utilizing strap-on boosters for added thrust.
• Capacity: Could place approximately 150 kg of satellites into Low Earth Orbit (LEO) at 400-600 km.
• Developmental Flights:
  • ASLV-D1 (1987) and ASLV-D2 (1988) were unsuccessful.
  • ASLV-D3 (1992) achieved the first success, launching SROSS-C.
  • ASLV-D4 (1994) was also successful.
• Significance: Laid the foundation for the development of more capable launch vehicles like PSLV and GSLV.

Polar Satellite Launch Vehicle (PSLV)

• Third-generation launch vehicle and ISRO's most reliable and versatile rocket.
• First successful launch: October 1994 (PSLV-D2).
• Structure: Four-stage hybrid rocket with alternating solid and liquid propulsion systems.
• Propellants:
  • First and Third stages: Solid propellant (HTPB).
  • Second and Fourth stages: Liquid propellant (UDMH + N2O4 for 2nd stage, MMH + MON for 4th stage). The Vikas engine is used in the second stage.
• Strap-on Boosters: PSLV can use six solid rocket strap-on boosters for additional thrust.
• Payload Capacity:
  • Sun-Synchronous Polar Orbit (SSPO) (600 km altitude): Up to 1,750 kg.
  • Geosynchronous Transfer Orbit (GTO): Up to 1,400 kg.
• Variants:
  • PSLV-G (Standard Version): Original version with six strap-on boosters.
  • PSLV-CA (Core Alone): Without strap-on boosters, for lighter payloads.
  • PSLV-XL (Extended Version): Most powerful, with larger strap-on boosters. Used for major missions like Chandrayaan-1 and Mangalyaan.
• Key Missions:
  • Chandrayaan-1 (2008): India's first lunar mission.
  • Mars Orbiter Mission (Mangalyaan, 2013): India's first mission to Mars, successful on its maiden attempt.
  • World Record (2017): Launched 104 satellites in a single mission (PSLV-C37).
  • Aditya-L1 (2023): India’s first solar observatory mission.

Geosynchronous Satellite Launch Vehicle (GSLV)

• Fourth-generation launch vehicle and ISRO's most powerful.
• Designed for launching medium and heavy satellites into Geosynchronous Transfer Orbits (GTO) and Geostationary Earth Orbits (GEO).
• First successful launch: 2003 (GSLV-D2). GSLV-D1 launched in 2001 was an experimental satellite and failed to achieve target orbit.
• Structure: Three-stage rocket.
• Propellants:
  • First stage: Solid fuel (S139 motor, S-200 boosters in Mk III).
  • Second stage: Liquid fuel (Vikas engine, L110).
  • Third stage (Cryogenic Upper Stage - CUS): Uses liquid hydrogen (LH2) as fuel and liquid oxygen (LOX) as oxidizer, stored at extremely low temperatures.
• Cryogenic Technology: India developed its indigenous cryogenic engine (CE-7.5, CE-20, CE-25) after initial reliance on Russia and facing restrictions. Mastery of this technology allows for launching heavier payloads and reduces foreign dependence.
• Payload Capacity:
  • GSLV Mk II: Up to 2,250 kg to GTO and 6,000 kg to LEO.
  • GSLV Mk III (LVM3): ISRO's most powerful launch vehicle, capable of placing 4-tonne class satellites to GTO and 8-10 tonne payloads to LEO. Used for Chandrayaan-2, Chandrayaan-3, and Gaganyaan.
• Key Missions:
  • GSAT-1 (2001): First experimental GSLV flight, failed to achieve target orbit.
  • GSLV-D5 (2014): First successful flight with indigenous cryogenic stage.
  • GSAT-9 (2017): Launched South Asia Satellite.
  • Chandrayaan-2 (2019): Orbiter successful, lander failed soft landing.
  • Chandrayaan-3 (2023): Successful soft landing on Moon's south pole.
  • Gaganyaan (upcoming): India's first human spaceflight mission will use human-rated LVM-3.

Small Satellite Launch Vehicle (SSLV)

• Purpose: Designed for launching mini, micro, or nano-satellites (10 to 500 kg mass) up to 500 km in LEO.
• Cost-effectiveness: SSLVs will cost 1/10th of a PSLV and need only 72 hours for launch compared to 45 days for PSLV.
• Structure: 3-stage solid propellant vehicle.
• Flexibility: Can be assembled both vertically and horizontally.
• New Spaceport: Foundation stone laid for India’s new spaceport for SSLV at Kulasekarapattinam, Tamil Nadu.

Reusable Launch Vehicle (RLV)

• Concept: Designed to re-enter Earth's atmosphere after launching the payload and land at a target location, allowing multiple launchings.
• Objective: To reduce launch costs significantly (up to 10 times).
• RLV-TD (Technology Demonstrator): Successfully tested in 2016. Renamed Pushpak (RLV LEX-02 MISSION).
• Propulsion: May use Scramjet engine technology for supersonic speed and to utilize atmospheric oxygen.

Next Generation Launch Vehicle (NGLV)

• Future plan to replace existing rockets.
• Will have 3 times the present payload capability of LVM3 at 1.5 times the cost.
• Features reusability and modular green propulsion systems.
• Maximum payload capability of 30 tonnes to Low Earth Orbit.
• Will use semi-cryogenic propulsion (refined kerosene as fuel with liquid oxygen as oxidizer) for booster stages.
• Aims to enable human spaceflight missions to the Bharatiya Antariksh Station and lunar/inter-planetary exploration missions.

Private Sector Rockets

• Agnibaan: Developed by Agnikul Cosmos, uses 3D-printed engine technology for small and medium satellite launches. World's first rocket powered by a fully 3D-printed engine.
• Vikram-S: Developed by Skyroot Aerospace, launched in 2022 as India's first privately built rocket.

Propellant Technology

Rocket propulsion relies on Newton's Third Law of Motion, where the expulsion of hot gases downward generates an upward thrust. Propellants are a combination of fuel and oxidizer.

Solid Propellants

• Fuel: Hydroxyl-terminated polybutadiene (HTPB).
• Oxidizer: Ammonium Perchlorate.
• Advantages: Compact, energy-dense, high thrust, minimal maintenance. Used for quick-response missiles due to simplicity and reliability.
• Disadvantages: Thrust cannot be controlled or stopped once ignited.
• Applications: Short-to-medium range ballistic missiles (e.g., Prithvi, BrahMos), and first/third stages of PSLV.

Liquid Propellants

• Fuel: Unsymmetrical Dimethylhydrazine (UDMH), Mono Methyl Hydrazine (MMH), Liquid Hydrogen (LH2).
• Oxidizer: Nitrogen Tetroxide (N2O4), Mixed Oxides of Nitrogen (MON), Liquid Oxygen (LOX).
• Advantages: Thrust can be controlled (started, stopped, throttled), high energy efficiency.
• Disadvantages: Complex design, requires more preparation time and handling safety.
• Applications: Long-range missiles, space launch vehicles (e.g., Agni series, Akash), and stages of PSLV and GSLV.

Cryogenic Propellants

• Description: Uses fuels (Liquid Hydrogen, -253°C) and oxidizers (Liquid Oxygen, -183°C) stored at extremely low temperatures.
• Advantages:
  • High energy density per unit mass, allowing for longer ranges and heavier payloads.
  • Clean fuel, producing only water upon combustion.
  • Economical, as fuel is cheap and readily available.
  • Essential for heavy satellites (2500-3000 kg) in Geo-stationary orbit and manned space flights.
• Disadvantages:
  • Complex handling and storage due to extremely low temperatures and high volatility.
  • Challenges include complex stage combustion cycles, high temperature variation (over 3000°C in thrust chamber), and material/alloy requirements for the engine.
• Global Status: Only a few countries (USA, Russia, China, Japan, France) possess this technology. India became the sixth.
• Applications: Employed in heavy-lift space missions (e.g., GSLV Mk III) and long-range ballistic missiles (e.g., Agni-V).

Hybrid Propellants

• Combines solid fuel and liquid oxidizer.
• Advantages: Offers better control over thrust compared to solid propulsion.
• Applications: Used for experimental systems and advanced prototypes (e.g., BrahMos Hypersonic Cruise Missile prototype).

Air-Breathing Engines (Ramjet, Scramjet)

• Utilizes atmospheric oxygen as the oxidizer, making the missile lighter as it doesn't need to carry onboard oxidizers.
• Ramjet: Works at supersonic speeds by compressing incoming air before combustion.
• Scramjet: Operates at hypersonic speeds, where air is compressed and combusted without slowing it to subsonic speeds.
• Advantages: Extremely fuel-efficient, enables hypersonic flight and extended ranges.
• Disadvantages: Limited to regions with sufficient atmospheric oxygen, unsuitable for space.
• Applications: Hypersonic missiles and advanced cruise missiles (e.g., BrahMos-II, HGV).

Institutional Setup for Launch Vehicle Development

Several ISRO centers are crucial for the design, development, and launch of these vehicles:

• Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram: Leading center for design and development of launch vehicle technology, including PSLV, GSLV, RLV, and human spaceflight technologies.
• Liquid Propulsion Systems Centre (LPSC), Thiruvananthapuram/Bengaluru: Responsible for design, development, and realization of liquid propulsion stages and cryogenic engines.
• ISRO Propulsion Complex (IPRC), Mahendragiri, TN: Engaged in cryogenic engine production and propulsion technology products.
• Satish Dhawan Space Centre (SDSC) SHAR, Sriharikota, Andhra Pradesh: India's primary spaceport, responsible for providing launch base infrastructure and integration of launches.
• Human Space Flight Centre (HSFC), Bengaluru: Focuses on Gaganyaan mission, including astronaut modules and life support systems.