DNA Explainer: ISRO GSLV failure - What does the anomaly in cryogenic engine mean?

After five promising minutes of its GISAT-1 satellite launch, the country’s space agency, the Indian Space Research Organisation (ISRO), was left disappointed when it became clear that the rocket had malfunctioned at the final stage.

The GSLV rocket lifted off from the Satish Dhawan Space Center in Sriharikota, Andhra Pradesh at 5:43 am on Thursday, August 12. The rocket reached the lower end of space to an altitude of 139 kms. The first two stages, that give initial thrust for lift-off and later carry the 52-meter-tall vehicle to space, performed to a tee.

Watch Live: Launch of EOS-03 onboard GSLV-F10 https://t.co/NE3rVjNtHb

— ISRO (@isro) August 11, 2021

But at the final stage i.e., the Cryogenic stage of the rocket launch, was when bad luck struck. On Twitter, ISRO announced that the mission had not been accomplished due to the technical issue on this final stage of the rocket.  

Here’s an explanation of what stages of a rocket mean, what’s the cryogenic stage and what went wrong during ISRO’s mission.

What are stages of a rocket?

Typically, a rocket going to space has two or more stages. In each stage, the rocket is propelled out into the space against Earth’s gravitational force with the help of different sets of engines (one or a cluster of engines fire each stage).

In simple words, a rocket combines multiple engines that are stacked vertically on top of each other. After each stage, the rocket separates from the used-up engines as the next stage takes over propulsion.

What is the cryogenic stage?

Cryogenic stage consists of engines that burn liquid Hydrogen and liquid Oxygen to generate thrust for the rocket. Not only is it more efficient in comparison to earth-storable liquid propellant rocket stages, the cryogenic stage also offers more thrust to the rocket for every kilogram of the propellant fuel.

Nevertheless, the cryogenic stage is technically quite complex as the propellants in this stage have to be at extremely low temperatures. Hydrogen liquifies at -253 degrees Celsius whereas Oxygen at -183 degrees Celsius. This can give rise to thermal and structural problems in the rocket.

What went wrong in ISRO’s launch?

At an altitude of around 139 kms and flight time of 5 minutes and 40 seconds, ISRO observed a marked deviation from the GSLV's planned flight path after it switched over to its final, cryogenic stage.

As per ISRO’s plan, the cryogenic engine, the stage that faced an anomaly, was supposed to perform from 4 minutes and 56 seconds until 18 minutes and 29 seconds. This would have been the rocket’s entire duration in space. Had this sequence of engine performance been successful, the EOS-3 satellite would have been ejected into space at 18 minutes and 39 seconds after its launch from earth.

But the mission was hit by a glitch sometime around 5 minutes and 40 seconds.

Nearly an hour after the failed launch at around 7 am, ISRO’s official Twitter handle said “Performance of first and second stages was normal. However, Cryogenic Upper Stage Ignition did not happen due to technical anomaly. The mission could not be accomplished as intended.”

GSLV-F10 launch took place today at 0543 Hrs IST as scheduled. Performance of first and second stages was normal. However, Cryogenic Upper Stage ignition did not happen due to technical anomaly. The mission couldn't be accomplished as intended.

— ISRO (@isro) August 12, 2021

What’s next for ISRO?

This failure is a setback for ISRO, which faced serious disruption in activity owing to the COVID-19 pandemic and a subsequent delay of prestigious missions.

ISRO is also working on Gaganyaan, an ambitious human spaceflight mission involving Indian astronauts.

It is important to note that cryogenic engines are a crucial part of advanced spaceflight missions that require heavy loads to be carried to space. The failure of EOS-3 mission would imply that ISRO has to further study and analyse its cryogenic engines for reliable performance.

Amid the uncertainty looming over the third wave of the pandemic, ISRO would also have to allocate time, manpower and financial resources to build another GSLV Mk2 rocket and a replacement for the lost EOS-3 satellite.