Fishermen near Thondi in Tamil Nadu were out at sea on March 12 when they spotted something strange floating about six nautical miles, or 11 kilometres, off the Thiruppalaikudi coast.
It was large, unfamiliar, and clearly not from a fishing boat. They informed the Marine Police, who identified the object and alerted the Indian Space Research Organisation (Isro).
Isro wasted no time. A three-member team from the Vikram Sarabhai Space Centre (VSSC) in Thiruvananthapuram travelled to the site, led by Scientist Saju. The team recovered the object and brought it back to VSSC for closer examination. It turned out to be a piece of one of Isro’s own rockets.
WHAT EXACTLY DID THEY FIND?
The object is called the SITVC system, which stands for Secondary Injection Thrust Vector Control. It comes from the first stage of the PSLV, or Polar Satellite Launch Vehicle, which is Isro’s most frequently used rocket.
More specifically, it is part of the S139 booster, the large solid-fuel motor at the bottom of the rocket that provides the initial thrust at liftoff. Put simply, this component is what helps the rocket steer itself in the right direction during the early part of its flight.
HOW DOES IT ACTUALLY WORK?
Most rockets steer using movable nozzles or fins. The PSLV’s first stage does it differently. The SITVC system has 24 small injection ports placed near the throat of the booster’s nozzle.
During flight, a chemical called Strontium Perchlorate is squirted through these ports into the nozzle.
This disrupts the flow of the exhaust gases in a controlled way, nudging the rocket up, down, left, or right as needed. The technical terms for these movements are pitch and yaw.
It sounds simple once you know how it works, but the precision required to pull this off at full thrust is remarkable.
WHERE DID THIS PIECE COME FROM?
When the S139 booster finishes its job, roughly 110 seconds after liftoff, it separates from the rocket and falls back towards Earth. Most of it burns up on re-entry.
But heavier parts, like the SITVC system, can sometimes survive and land in the ocean. Isro has not yet said which mission this particular piece came from. That investigation is likely ongoing at VSSC.
