PSLV C35 Countdown Begins: Here’s Why This Launch Is Trickier Than Others

The countdown to the launch of Indian Space Research Organisation’s (ISRO) latest rocket began on Saturday at Sriharikota in Andhra Pradesh.

The Indian space agency said the main cargo of PSLV C35 will be the 371 kg SCATSAT-1, designed for ocean and weather related studies. The rocket will also put into orbit seven other small satellites.

This is the first mission of Polar Satellite Launch Vehicle (PSLV) in which ISRO will be launching its payloads into two different orbits. Here is a quick description of how the space agency plans to achieve this through ‘multiple burns’.

After putting the weather satellite into a 730 km polar sun synchronous orbit, the rocket’s fourth stage will be shut down. It will be turned on after one hour and 22 minutes for a short period (about 20 seconds) before being turned off again. There will be another ‘burn’ (i.e. restarting of the engines) two hours and 11 minutes into the flight. Four minutes later all the seven satellites would be put into their designated orbit.

This switching off and switching on of the rocket’s fourth stage is called multiple burn technology, which was first tested by ISRO while launching its PSLV rocket on 16 December 2015

“Restarting a rocket engine soon after it was shut off is a critical technology that has to be mastered. Once a rocket engine is activated, a great amount of heat is generated. The trick is to cool it down in space and to restart it within a short period of time,” an industry expert said.

“This is entirely different from switching on and switching off the communication satellite’s engines in space. The interval between two restarts of a communication satellite engine will be in days. But in the case of restarting a rocket engine, the time gap will be in hours,” the expert added.

“By that time the rocket’s engine has to be cooled down. This part of the experiment is very critical,” he said.

With inputs from IANS