- The Tamil Nadu government has started acquiring 2,300 acres of land at Kulasekarapattinam in Thoothukudi district for ISRO’s second launch port, smaller than the first port in Sriharikota, Andhra Pradesh.
- Currently satellites are launched from the Sriharikota launch centre in Andhra Pradesh.
- The second spaceport after Sriharikota was announced considering the increase in the number of launches that the space agency is planning in the coming years.
- Thoothukudi offers a locational advantage to launch towards India’s South.
- When ready, the new port will handle mainly the small satellite launch vehicle (SSLV) that is under development. SSLVs are meant to put a payload of up to 500 kg in space.
- Another lunar mission is being discussed with Japanese space agency JAXA (Japan Aeronautics Exploration Agency) but its elements have not been finalized.
- Although scores of landers sent by Russia, the U.S. and the Chinese have explored moon’s surface, so far, no other agency has landed in the southern hemisphere of moon. ISRO hopes to be still the first to do so through its Chandrayaan-3 Mission.
But why did the space agency choose Thoothukudi for its second launching port?
Proximity to seashore
- Thoothukudi’s proximity to the seashore makes it ideal for “straight southward” launches.
- From Sriharikota, such southward bound launches are not possible as the rockets have to fly around Sri Lanka.
- The fact that rockets will be able to have a straight trajectory from Thoothukudi will also allow them to carry heavier payloads.
- Incidentally, the Sriharikota spaceport was also chosen for its proximity to the sea. Safety reasons, too, were factored in while choosing the location.
- A spaceport in Thoothukudi district would be ideal for putting satellites in the polar orbit — normally undertaken through a Polar Satelite Launch Vehicle or PSLV rocket — but not for satellites with geostationary orbits launched by GSLV rockets.
- Note that not all satellites are launched from equatorial regions; satellites that need to achieve a polar orbit around Earth won’t have any use for the natural boost from earth’s rotation, as they are headed either in a northern or southern direction.
Proximity to Equator
- Like the Sriharikota spaceport in the Satish Dhawan Space Centre, Thoothukudi was selected as a spaceport due to its nearness to the equator.
- A rocket launch site should be on the east coast and near the equator.
- The proximity to the Equator saves substantial fuel. The Earth’s rotation provides a speed boost to rockets launched in the eastward direction and headed for an equatorial orbit around the planet.
- ISRO has its Liquid Propulsion Systems Centre (LPSC) at Mahendragiri in Tirunelveli district, where it assembles the second and fourth stage engines for the PSLV.
- Instead of transporting the second and fourth stages to Sriharikota from Mahendragiri, it would be easier to shift them to the launch pad if it is built in Kulasekarapattinam, which is around 100 km away.
Why is it better to launch a spaceship from near the equator?
- The surface velocity of rotation varies from point to point on the Earth. It is about 1600 km per hour or about 460 meters in a second near the equator. The velocity gradually reduces as we move to the poles and it is practically zero there.
- A satellite launched from the sites near the equator towards the east direction will get an initial boost equal to the velocity of Earth surface or the rotational speed of Earth (This is because of inertia and Earth rotates from west to east). This is similar to an athlete circling round and round before throwing a discus or a shot put. This speed will help the spacecraft keep up a good enough speed to stay in orbit.
- The initial boost helps in cutting down the cost of rockets used to launch the satellites.
- This is the major reason for launching satellites in the east ward direction. But this benefit can be taken only for such satellites which are placed in geo-stationary orbit or which circle the Earth parallel to the equator. Such satellites are usually communication satellites or satellites used for scientific research such as ISS.
- There are other satellites which are placed in polar orbits moving across the equator in north south direction and used mainly for mapping or sometimes for spying. Such satellites are generally launched in south ward or north ward direction and therefore cannot take advantage of the Earth’s rotation.
- Also, these rockets travel eastward, so if anything goes wrong during their ascent, the debris would essentially fall into an ocean’s waters, far away from densely populated areas.
- Another reason they launch rockets from places near the Equator is that the satellites intended to attain a geostationary orbit (e.g., communication satellites) must have zero inclination with respect to the equatorial plane.
- If not, then they have to make complex course corrections and burn a lot of fuel to attain the proper orbit.