Science and Technology- Developments and their Applications and Effects in Everyday Life
News: ISRO launches SSLV: What is the aim behind developing Small Satellite Launch Vehicles?
Discuss the evolution of different types of ISRO’s launch vehicles and the significance of SSLV and future launch vehicles.
Recently, the Indian Space Research Organisation (ISRO) successfully launched the third developmental flight of the Small Satellite Launch Vehicle (SSLV). The SSLV-D3 placed the Earth observation satellite EOS-08 precisely into orbit.
What are Launch Vehicles?
- Launch Vehicle or Rockets act as a bus and satellites are passengers; hence the rockets place the satellites on their destination.
- Rockets have several detachable energy-providing parts. They burn different kinds of fuels to power the rocket. Once their fuel is exhausted, they detach from the rocket and fall off, often burning off in the atmosphere due to air-friction, and getting destroyed. Only a small part of the original rocket goes till the intended destination of the satellite.
- Once the satellite is finally ejected, this last part of the rocket either becomes part of space debris, or once again burns off after falling into the atmosphere.
Evolution of Launch Vehicles:
- According to the payload or weight of the satellites could bring, the launch vehicle could evolve and it is mainly categorized as Polar Satellite Launch Vehicle (PSLV), Geosynchronous Satellite Launch Vehicles (GSLVs) and Small Satellite Launch Vehicle (SSLV).
- The first rocket developed by ISRO was simply called SLV, or satellite launch vehicle. It was followed by the Augmented Satellite Launch Vehicle or ASLV.
- These two could carry small satellites, weighing up to 150 kg, to lower earth orbits. ASLV operated till the early 1990s before PSLV came on the scene.
- PSLV’s first launch was in 1994, and it has been ISRO’s main rocket ever since. Today’s PSLV, however, is vastly improved and several times more powerful than the ones used in the 1990s.
The Polar Satellite Launch Vehicle (PSLV)
- It is the third generation of Indian satellite launch vehicles first used in 1994. More than 50 successful PSLV launches have taken place to date.
- It has also been called “the workhorse of ISRO” for consistently delivering various satellites into low earth orbits (less than 2,000 km in altitude) with a high success rate.
- The PSLV-XL can carry around 1,860 kg of payload.
Geosynchronous Satellite Launch Vehicles (GSLV)
- Geosynchronous Satellite Launch Vehicles (GSLVs) have been instrumental in launching communication satellites in the geosynchronous transfer orbit.
- According to the European Space Agency (ESA), telecommunications satellites are usually placed in geostationary Earth orbit (GEO). It is a circular orbit 35,786 kilometres above Earth’s equator.
- A satellite in the GTO keeps its orbit around the same location over the planet once a day while orbiting it at a height of about 37,000 km.
GSLV vs. PSLV
- The Polar Satellite Launch Vehicle (PSLV) can take up to 2000 kg into space for up to 600–900 km, but the GSLV can carry a bigger payload of up to 5,000 kg for up to 37,000 km in orbit.
- The primary purpose of PSLV is to launch earth observation or remote sensing satellites, while GSLV is intended to launch communication satellites.
- Satellites are launched by GSLV into GTOs, or higher elliptical orbits.
Small Satellite Launch Vehicle (SSLV)
- ISRO’s Small Satellite Launch Vehicle (SSLV) is a three-stage Launch Vehicle configured with three Solid Propulsion Stages.
- It also has a liquid propulsion-based Velocity Trimming Module (VTM) as a terminal stage, which can help adjust the velocity as it prepares to place the satellite.
- Essentially, the aim behind SSLVs is to produce low-cost launch vehicles with short turnaround times and minimal infrastructural requirements. The SSLV can launch satellites weighing up to 500kg and accommodate multiple satellites.
- Before SSLVs, smaller payloads had to be sent into Space using other launch vehicles carrying multiple, bigger satellites. They depended upon the launch schedules of those satellites.
About Reusable rockets:
- The future rockets are meant to be reusable. Only a small part of the rocket would be destroyed during the mission.
- The bulk of it would re-enter the earth’s atmosphere and land very much like an airplane, and can be used in future missions.
- Reusable rockets would cut down on costs and energy, and also reduce space debris, which is becoming a serious problem because of the large number of launches.
- Fully-reusable rockets are still to be developed, but partially-reusable launch vehicles are already in use.
- ISRO has also developed a reusable rocket, called RLV-TD (Reusable Launch Vehicle Technology Demonstrator) which has had a successful test flight in 2016.