ISROs Mission 101 Fizzles: The Third Stage Mystery

On May 18, 2025, the Indian Space Research Organisation (ISRO) introduced its 101st house undertaking—PSLV-C61—from Sriharikota. The purpose was once to position the EOS-09 Earth commentary satellite tv for pc into orbit. While the rocket’s first and 2nd phases carried out neatly, an issue within the 0.33 degree brought about the undertaking to fail. ISRO later showed that the chamber drive dropped within the 0.33 degree, which averted the rocket from handing over the satellite tv for pc to its deliberate orbit.

Let’s perceive what will have came about—in easy, easy-to-follow language.

What Is The PSLV, And What Does The Third Stage Do?

The Polar Satellite Launch Vehicle (PSLV) is considered one of ISRO’s maximum relied on rockets. It has 4 phases that paintings one after some other to hold a satellite tv for pc into house.

The 0.33 degree, referred to as PS3, runs on cast gas—a packed chemical combine that burns to push the rocket additional upward. The chamber drive is the drive throughout the motor when the gas burns. It will have to keep top to generate sufficient thrust (push). If this drive drops, the motor can’t produce the facility had to stay going—and the undertaking fails.

What Went Wrong in PSLV-C61?

ISRO showed that the 0.33 degree failed since the chamber drive dropped swiftly. This way the motor didn’t push onerous sufficient to hold EOS-09 into its right kind orbit. The precise reason continues to be beneath investigation, however listed below are six conceivable causes, defined with easy examples:

Problem With Solid Fuel

If the gas had cracks, air bubbles, or was once packed erratically, it could no longer have burned correctly. Think of a Diwali rocket with dangerous gunpowder—it simply fizzles out as a substitute of flying. Leak within the Motor Case

The motor is sort of a robust container. If there’s a crack or hollow, sizzling gases get away, shedding the drive. It’s like a drive cooker with a small hollow—the steam leaks and the meals gained’t cook dinner neatly. 

Nozzle Malfunction

The nozzle directs the gases out of the motor. If it’s broken or blocked, drive builds up poorly. Imagine a water hose with a foul nozzle—the water doesn’t spray forcefully. 

Ignition or Burning Fault

The gas will have to burn calmly after ignition. If it doesn’t, drive drops. Like seeking to mild rainy firewood—it begins however doesn’t keep lit. 

Vibration Or Structural Stress

Rockets shake so much. Excess vibration will have brought about tiny breaks within the motor or nozzle. Like a automobile tyre bursting after hitting too many potholes.

Missed Defects In Testing

If an issue wasn’t discovered all through pre-launch assessments, it could display up mid-flight. Just like a telephone that appears effective however has a hidden fault no longer stuck on the manufacturing facility. 

Why This Failure Matters

The 0.33 degree is important—it provides the general push to get the satellite tv for pc into orbit. If this degree fails, the rocket doesn’t succeed in the suitable top or velocity. In this situation, EOS-09, supposed for Earth commentary duties like town making plans, agriculture, and nationwide safety, was once misplaced.

How Often Has PSLV Failed?

PSLV may be very dependable, with handiest 3 screw ups in over 60 missions:

1993 – PSLV-D1: Software and degree separation factor.

2017 – PSLV-C39: Heat protect did not open.

2025 – PSLV-C61: Pressure drop in third-stage motor.

Although ISRO’s GSLV-F10 in 2021 additionally failed because of drive loss, that was once in a liquid-fuel degree, no longer a cast degree like PSLV’s.

What Will ISRO Do Next?

ISRO has already shaped a professional overview staff. They will:

Analyse telemetry knowledge (rocket’s in-flight knowledge).

Inspect the design, gas, motor case, and nozzle.

Check all pre-launch check effects.

ISRO has a robust monitor document of convalescing from setbacks—whether or not it was once Chandrayaan or Gaganyaan checking out—and this time shall be no other. They’ll determine the fault, repair it, and go back more potent.

In Short

The PSLV-C61 undertaking failed as a result of a drop in chamber drive within the 0.33 degree, which makes use of cast gas. This may well be because of gas problems, leaks, nozzle faults, or ignored defects. EOS-09 was once misplaced, however ISRO is investigating and can repair the issue for long run missions.

It’s like a automobile breaking down mid-journey—the mechanics (ISRO) are already checking the engine (0.33 degree) so the following shuttle will cross easily.

(Girish Linganna is an award-winning science creator and Defence, Aerospace & Geopolitical Analyst based totally in Bengaluru. He could also be Director of ADD Engineering Components India Pvt. Ltd., a subsidiary of ADD Engineering GmbH, Germany.)