Flight data analysis, simulation tests to reveal cause of GSLV rocket's failure

Analysis of flight data of the recently failed Indian rocket GSLV-F10 and simulation tests are to be done to arrive at the cause of failure. The failure analysis report detailing the cause of rocket's failure is expected to be completed by the end of this month, it is learnt.

Experts in -- rockets/propulsion -- from Indian Space Research Organisation (ISRO) and also from outside are studying the data sent by the failed GSLV-F10 rocket to arrive at the failure cause, said an official of ISRO.

On August 12, India's Geosynchronous Satellite Launch Vehicle-F10 (GSLV-F10) carrying the country's first Geo-Imaging Satellite (GISAT-1) failed to complete its mission as its cryogenic engine did not ignite.

The failure resulted in the loss of rocket and satellite both valued over several hundred crores of rupees and also the revenue opportunity for 10 years.

"GSLV-F10 launch took place on August 12, 2021 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 said in a statement.

The GSLV-F10 is a three stage/engine rocket. The core of the first stage is fired with solid fuel and the four strap-on motors by liquid fuel. The second is the liquid fuel and the third is the cryogenic engine.

"A whole lot of data has to be studied and simulation tests have to be done to arrive at the actual cause of failure. After the simulation tests are done, the reports will be reviewed by an expert panel," the official told IANS preferring anonymity.

The final report on the failure is expected by the end of this month.

"Based on that, whatever corrective actions need to be taken will be taken as other satellites are planned to be sent up by a similar rocket," the official added.

Refuting reports that the cryogenic engine was a reengineered Russian cryogenic engine, the official said: "India's cryogenic engine started well ahead of the receipt of such engines from Russia. Even the GSLV rockets that flew with Russian engines have failed. There may be some similarities between Indian and Russian engines. But India designed its own cryogenic engine for the GSLV MkII rocket."

According to the official, the cryogenic engine for India's bigger rocket GSLV MkIII was also designed by the ISRO engineers which is a slightly simpler technology.

"But designing and building a lower powered engine for GSLV-MkII with a similar technology will take another 12 years. Moreover there is nothing majorly wrong with the cryogenic engine for GSLV-MkII. Several GSLV-MkII rockets have flown successfully," the official said.

Meanwhile, rocket experts had told IANS that failure of the ignitor or failure of the cryogenic engine to get ignited or even the failure of the avionics in sending the ignite signal could be the reasons for the Indian rocket going down.

"The cryogenic engine is a complex system and the failure is not due to design flaw," former Chairman of ISRO G. Madhavan Nair had told IANS.

According to him, the ignitor/pyro systems could have ignited but the fuel might not have due to various reasons.

Nair also agreed the rocket being kept idle for more than a year after it was readied for flight could have also affected the functionality of the components.

"It could be a failure in avionics in sending the ignite signal. Or the failure of igniter which is a pyro element where testing is done for few in a batch rather than every component. Moreover, there is long storage of components due to pandemic delay causing some unnoticed component failure in the ignition system," another space sector official on the condition of anonymity told IANS.

"Cryo stage did not ignite is the cause -- this is officially announced and can be seen in the curve," the official added.

Another space sector expert preferring anonymity told IANS: "On seeing the videos captured by the cameras fixed at the rocket, one can conclude as to the cause of loss."

"During launch ISRO did announce separation of the heat shield, shutting off of the second stage and firing of the cryogenic stage. Success of cryo ignition and normal thrust was announced," the expert said.

"I would not be surprised that the heat shield did not get separated, though telemetry may be correct and the vehicle veers out of trajectory due to excess load of heat shield, apart from the satellite load," he added.

"Non separation of heat shield even with four way redundancy and yet sending right telemetry, has been seen earlier. This phenomenon was seen in PSLV 39 launch with IRNSS-1H, on 31st August 2017. But due to the presence of an on-board camera, the non-separation of the heat shield was detected. Otherwise, it could have been passed off as malfunctioning of the last stage of the rocket," the expert remarked.

However, Nair does not agree with this possibility.

"After the separation of the heat shield the rocket had travelled for several seconds on the plotted path. Had the heat shield not separated then the rocket would have veered away much earlier," Nair said.