About GSLV-F15

Why in News? 

ISRO achieved another historic milestone with the successful launch of the GSLV-F15 rocket carrying the NVS-02 satellite. The mission marked the 100th rocket launch from the Sriharikota spaceport in Andhra Pradesh.

Key Highlights of GSLV-F15 Rocket 

• The rocket was launched from the Second Launch Pad (SLP) at the Satish Dhawan Space Centre, SHAR, located in Sriharikota, India.
• GSLV-F15 was the 17th flight of India’s Geosynchronous Satellite Launch Vehicle (GSLV).
• It was the 11th successful launch utilizing India’s indigenous cryogenic stage.
• This mission marked ISRO’s technological advancements in cryogenic propulsion systems.
• The rocket’s payload fairing was a metallic version with a diameter of 3.4 meters, designed to safeguard the satellite during ascent.
• The GSLV-F15 successfully placed the NVS-02 satellite into a Geosynchronous Transfer Orbit (GTO).
• The mission also became the 8th operational flight of GSLV with the indigenous cryogenic stage.

Introduction & History of GSLV (Geosynchronous Satellite Launch Vehicle)

• • Introduction:
    • The Geosynchronous Satellite Launch Vehicle (GSLV) is an expendable launch system developed by ISRO.
    • It has been used in 15 launches since its first flight in 2001.
    • The GSLV is known for its cryogenic third stage, which uses liquid hydrogen and liquid oxygen to generate higher thrust, enabling the vehicle to carry heavier payloads.
    • GSLV is a three-stage rocket, which includes solid rocket boosters, a liquid core stage, and a cryogenic upper stage.
    • One of the notable missions launched by GSLV was Chandrayaan-2, India’s mission to the moon.
    • GSLV is designed to place communication and meteorological satellites into high orbits. It represents India’s self-reliance in satellite launching capabilities.
    • GSLV is classified as a medium-lift launch vehicle, making it capable of placing satellites into a variety of orbits, including GTO, SSO, and LEO.
    • GSLV rockets are commonly used to launch satellites such as INSAT, GSAT (including the South Asia Satellite), GISAT, NVS, and NISAR.
• History:
• • Prior to the GSLV, the PSLV was in operation since 1993 but lacked the capacity to launch heavier payloads into geosynchronous transfer orbit (GTO).
  • Recognizing the strategic necessity of launching INSAT satellites for national communication, meteorology, and other services, ISRO initiated the GSLV development in the early 1990s.
  • The first experimental GSLV flight in 2000, which carried the GSAT-1 satellite, failed due to issues with the cryogenic stage performance.
  • After overcoming technological challenges, the first successful flight with an indigenous cryogenic stage occurred in January 2014, when GSLV-D5 launched the GSAT-14 satellite.
  • Since 2017, GSLV has successfully completed 6 consecutive missions, proving its reliability and maturity in launching heavy payloads.

Key Features of GSLV Rockets

• Size: 
  • Height: The GSLV stands at a height of 49.13 meters (161.2 feet) and reaches 51.73 meters with the Ogive Payload Fairing.
  • Diameter: The rocket has a diameter of 2.8 meters (9 feet 2 inches).
  • Lift-off Mass: The total mass of the rocket at lift-off is approximately 420 tonnes.
• Payload Capacity: 
  • Geosynchronous Transfer Orbit (GTO): The GSLV is capable of carrying a payload of 2,250 kg into GTO.
  • Sun-Synchronous Orbit (SSO): It can deliver a payload weighing 3,000 kg into SSO.
  • Low Earth Orbit (LEO): The rocket can place 6,000 kg payloads into LEO.
• Booster:
  • The rocket uses 4 L40 H boosters.
  • The propellant mass of each booster is 42,700 kg (94,100 lb).

Variants of GSLV Rockets

• GSLV Mark I
  • The GSLV Mark I used a Russian Cryogenic Stage (CS) and was the initial version of the GSLV.
  • GSLV Mk.I had its first flight on April 18, 2001.
  • The first developmental flight had a 129-tonne first stage (S125) and could carry around 1,500 kg into geostationary transfer orbit (GTO).
  • All GSLV Mark I launches were conducted from the Satish Dhawan Space Centre in Sriharikota.
  • It conducted a total of 5 flights as of now from 2001-2010. In 2010 a suborbital test was conducted, which was the last rocket of this series.
• GSLV Mark II
  • The GSLV Mark II is equipped with the indigenous CE-7.5 cryogenic engine.
  • GSLV Mark II previously used Russian cryogenic engines, but now incorporates Indian technology.
  • In 2018, ISRO introduced a 6% increased thrust version of the Vikas engine for the first stage boosters, which was first demonstrated in the GSAT-6A launch.
  • GSLV Mk.II began its operation on April 15, 2010, and has been the active version.
  • The last flight of GSLV Mk.II was conducted on January 29, 2025.
• GSLV Mk III (LVM-3)
  • The GSLV Mk III, also known as LVM-3, is the most powerful, advanced and latest variant in the GSLV series.
  • With a payload capacity of up to 4 tons to GTO, it is designed for heavy payloads and is used for critical missions like the Chandrayaan-2 and Gaganyaan.
• RLV-OREX (Reusable Launch Vehicle Technology Demonstration)
  • The Reusable Launch Vehicle Technology Demonstration program (RLV-OREX) is an experimental initiative by ISRO to develop a space plane concept.
  • A modified version of the GSLV Mk II rocket, with its cryogenic stage replaced by the PS-4 stage from the PSLV.

Cryogenic Technology in GSLV

• How Cryogenic Technology Works in GSLV:
  • Cryogenic upper stage (CUS) of the GSLV uses liquid hydrogen (LH₂) and liquid oxygen (LOX) as propellants to power the rocket’s upper stage.
  • The main engine and two steering engines feed these propellants into the combustion chamber where they are ignited.
  • A gas generator cycle is employed to operate the engines, where the thrust and mixture ratio are carefully regulated.
  • Steering engines control the rocket’s trajectory during the thrust phase.
• What is Cryogenics?
  • Cryogenics is the science of extremely low temperatures, typically below -153°C, at which gases such as hydrogen, nitrogen, and oxygen turn into liquids.
  • In rocket propulsion, cryogenic fluids like liquid hydrogen and liquid oxygen provide the necessary thrust for high-performance engines, which is vital for placing payloads in higher orbits.
• Why Cryogenic Technology:
  • Cryogenic engines provide much higher efficiency and thrust compared to older liquid propulsion technologies.
  • This makes GSLV capable of carrying heavier payloads to Geosynchronous Transfer Orbits (GTO).
  • The Indigenous Cryogenic Engine (CE-7.5) is part of ISRO’s effort to develop self-reliant cryogenic technology for space exploration.
• Applications: GSLV’s cryogenic stage has been used in several important missions such as the Chandrayaan-2 mission and GSAT-19 satellite launch.

The Strategic Role of GSLV in India’s Space Program

• Strategic Autonomy: The GSLV program gives India a self-reliant launch capability, reducing dependency on foreign commercial launchers. This strategic autonomy strengthens India’s position in global space affairs and ensures security.
• Economic Impact: By offering launch self-reliance, GSLV reduces reliance on international space agencies, ultimately saving on costs. The program also boosts economic growth by providing space-based services that benefit key sectors like communication, weather forecasting, and navigation.
• Technological Advancements: The GSLV program serves as a testament to India’s technological mastery, especially in cryogenic rocket technology. It highlights India’s scientific and technical prowess. GSLV enables rapid and customized launches, making it easier for India to meet its space exploration goals.
• National Security: GSLV plays a crucial role in national security by enabling India to launch military and intelligence satellites independently. These satellites improve surveillance, communications, and early warning systems, significantly boosting India’s defense capabilities and deterrence posture.

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