Space Launch Vehicles and Satellite Technology Explained

Posted on Mar 25, 2026 in Geography

Space Launch Vehicles

A space launch vehicle (SLV) is a rocket system used to carry satellites or spacecraft from Earth’s surface into space. It provides the required thrust to overcome Earth’s gravity and place payloads into specific orbits such as low Earth orbit (LEO), geostationary orbit (GEO), or beyond.

1. PSLV (Polar Satellite Launch Vehicle)

  • Developed by the Indian Space Research Organisation (ISRO).
  • Known as the workhorse of ISRO.
  • Used mainly to launch satellites into polar sun-synchronous orbits (SSO).
  • Known for its high reliability and cost-effectiveness.
  • Can carry multiple satellites in a single launch.
  • Famous mission: launching 104 satellites in one go (2017).

Stages

  • 4 stages (Solid + Liquid alternately): 1st & 3rd are solid; 2nd & 4th are liquid.

Payload Capacity

  • ~1,750 kg to Sun-synchronous orbit (SSO).
  • ~1,400 kg to Low Earth Orbit (LEO).

Use: Launching Earth observation and remote sensing satellites.

2. GSLV (Geosynchronous Satellite Launch Vehicle)

  • Used for heavier satellites and higher orbits.
  • Used for geostationary orbit (GEO) missions.
  • Equipped with an indigenous cryogenic upper stage.
  • Can carry communication satellites.
  • More powerful than PSLV.
  • Variant GSLV Mk III (LVM3) is used for missions like Chandrayaan-2 and Chandrayaan-3.

Stages

  • 3 stages: 1st is solid core + liquid strap-ons; 2nd is liquid; 3rd is cryogenic.

Payload Capacity

  • ~2,500 kg to Geostationary Transfer Orbit (GTO).
  • ~5,000 kg to LEO.

Use: Communication satellites and lunar missions.

3. SSLV (Small Satellite Launch Vehicle)

  • Designed for small satellites (up to ~500 kg).
  • Low cost and quick launch capability.
  • Requires minimal launch infrastructure.
  • Ideal for commercial and on-demand launches.
  • Provides flexibility for private players.

Stages

  • 3 solid stages + velocity trimming module.

Payload Capacity

  • ~500 kg to LEO; ~300 kg to SSO.

Use: Commercial and small satellite missions.

4. RLV-TD (Reusable Launch Vehicle)

The RLV-TD is an experimental project by ISRO.

  • Aims to develop a reusable space vehicle.
  • Designed to reduce the cost of space missions.
  • Uses a winged body that can return and land like an aircraft.
  • Currently in the testing and development phase.

Rocket Propulsion

Rocket propulsion is the principle by which a rocket moves forward by expelling gases at high speed in the opposite direction, based on Newton’s Third Law of Motion. It does not require air, so it works in space.

1. Solid Propulsion System

How it works: Fuel and oxidizer are mixed together in solid form (propellant grain). When ignited, it produces hot gases that exit through a nozzle to create thrust.

  • Advantages: Simple, reliable, low cost, high launch thrust.
  • Disadvantages: Cannot be stopped once ignited; lower efficiency.

2. Liquid Propulsion System

Construction: Fuel and oxidizer tanks, turbopumps, combustion chamber, and cooling system.

  • Working Principle: Propellants are pumped into the combustion chamber, mixed, and burned.
  • Types: Cryogenic (liquid hydrogen/oxygen) and Hypergolic (ignite on contact).
  • Advantages: High efficiency, precise thrust control, restartable.

3. Hybrid Propulsion System

Construction: Solid fuel grain with a liquid or gaseous oxidizer.

  • Working Principle: Oxidizer is injected into the combustion chamber to react with the solid fuel surface.
  • Advantages: Safer than liquid systems, throttle control possible.

Satellite Technology

A satellite is an object that orbits a planet or larger body. Artificial satellites are human-made objects launched for communication, weather monitoring, GPS, and research.

Components of a Satellite

  • Power System: Solar panels and batteries.
  • Communication System: Transponders for signal relay.
  • Payload: Cameras, sensors, and scientific instruments.
  • Antenna: Transmitting and receiving signals.
  • Control System: Thrusters and gyroscopes for stability.

Types of Satellites

1. Communication Satellite

Used to transmit signals for TV, telephone, and internet. They act as relay stations in space. GEO satellites cover large areas, while LEO satellites provide high-speed, low-latency coverage.

2. Weather Satellite

Observe Earth’s atmosphere to collect data on clouds, temperature, and storms. Geostationary satellites (e.g., INSAT-3D) provide continuous monitoring, while Polar-orbiting satellites (e.g., NOAA-20) provide global data.

3. Remote Sensing Satellite

Collect information about Earth’s surface without direct contact. They monitor natural resources, environmental changes, and disasters using high-resolution sensors.

4. Navigation Satellite

Provide precise location and timing (e.g., GPS, GLONASS, Galileo). They operate in Medium Earth Orbit (MEO) to provide global coverage via triangulation.

Space Telescopes

Hubble Space Telescope

Launched in 1990, Hubble observes the universe in ultraviolet, visible, and near-infrared light. It has confirmed the existence of supermassive black holes and helped measure the age of the universe.

James Webb Space Telescope (JWST)

Launched in 2021, JWST is the most powerful infrared telescope ever built. Positioned at the L2 Lagrange point, it studies the earliest galaxies, exoplanet atmospheres, and star formation processes.