Malfunction in ISRO's Mission 101: Puzzle Surrounding Third Stage Remains Unsolved
Rewritten Article
In the case of the May 18, 2025, Indian Space Research Organisation (ISRO) mission, PSLV-C61, things didn't go as planned. The goal was to launch EOS-09, an Earth observation satellite, into orbit. Although the first and second stages performed flawlessly, the third stage, nicknamed PS3, failed due to a drop in chamber pressure. Let's break down what this means and what could've gone wrong.
What's the Deal with PSLV and the Third Stage?
PSLV, one of ISRO's trusted rockets, consists of four stages. The third stage is called the PS3 and runs on solid fuel. The chamber pressure is the pressure inside the motor when the fuel burns. This pressure must stay high to generate enough thrust for the rocket to move forward. If the pressure drops, it could lead to mission failure.
So, What Happened with PSLV-C61?
When the chamber pressure dropped without warning, it prevented the third stage from pushing hard enough to get EOS-09 to its intended orbit. ISRO is still investigating the exact cause, but here are six possible suspects:
- Fuel Issues: If the fuel contained cracks, air bubbles, or was packed unevenly, it might not have burned properly.
- Leak in the Motor Case: If there's a crack or hole in the motor, hot gases escape, dropping the pressure.
- Nozzle Malfunction: Damage or blockage in the nozzle can lead to pressure buildup problems.
- Ignition or Burning Fault: The fuel must burn evenly after ignition. If it doesn't, pressure might drop.
- Vibration or Structural Stress: Excess vibration could cause tiny breaks in the motor or nozzle.
- Missed Defects in Testing: If a problem wasn't discovered during pre-launch tests, it might've shown up mid-flight.
Why Does This Matter?
The third stage provides the final push to get the satellite into orbit. If it fails, the rocket doesn't reach the right height or speed. For EOS-09, this meant losing a satellite meant for Earth observation tasks like city planning, agriculture, and national security.
How Often Does PSLV Flub Up?
While PSLV is very reliable, with only three failures in over 60 missions:
- 1993 – PSLV-D1: Software and stage separation issue.
- 2017 – PSLV-C39: Heat shield failed to open.
- 2025 – PSLV-C61: Pressure drop in third-stage motor.
Although ISRO's GSLV-F10 in 2021 also failed due to pressure loss, that was in a liquid-fuel stage, not a solid stage like PSLV's.
What's Next for ISRO?
ISRO has created a team of experts to investigate. They'll look at:
- Telemetry data (rocket's in-flight information).
- The design, fuel, motor case, and nozzle.
- Pre-launch test results.
Although setbacks have happened with missions like Chandrayaan and Gaganyaan testing, ISRO has always recovered and come back even stronger. They'll find the fault, fix it, and get ready for the next mission.
The Bottom Line
The PSLV-C61 mission flopped due to a pressure drop in the third stage. The investigation is ongoing but could be due to fuel issues, leaks, nozzle malfunctions, or missed defects during testing. EOS-09 was lost, but ISRO is working hard to figure out what went wrong and prevent it in future missions. It's like a car breaking down on a journey – the mechanics (ISRO) are already checking the engine (third stage) so the next trip will go smoothly.
(Girish Linganna is an award-winning science writer and Defense, Aerospace, and Geopolitical Analyst based in Bengaluru. He is also Director of ADD Engineering Components India Pvt. Ltd., a subsidiary of ADD Engineering GmbH, Germany.)
Source: ISRO's Website and Encyclopedia Britannica
Note: The given data provides insights into the role of the third stage in PSLV and common reasons for third-stage failure. However, it has been kept minimal in the rewritten article to maintain a natural flow and avoid overloading the content with excessive details.
- The third stage of PSLV, responsible for delivering satellites into their intended orbits, is powered by solid fuel and must maintain a high chamber pressure to generate enough thrust.
- The failure of the third stage on the PSLV-C61 mission could be linked to various suspects, such as fuel issues, leaks in the motor case, nozzle malfunctions, ignition or burning faults, vibration or structural stress, or missed defects in testing.
