Explained: Why ISRO's GISAT-1 satellite launch failed today

The launch failed when the cryogenic upper stage engine failed to ignite. The cryogenic upper stage is the last stage of a rocket intending to reach the upper stages of the atmosphere, at the edge of space.

The cryogenic upper stage uses liquid oxygen and liquid hydrogen as fuel sources instead of solid rocket fuel or other Earth-storable liquid propellants. The cryo engine is a highly sophisticated technology that keeps hydrogen and oxygen at temperatures below -150 degrees Celsius in pressurised tanks before being combined together to provide propulsion. The cryogenic stage provides more thrust per unit of fuel when compared to other fuels and is necessary to reach farther into the atmosphere, and breaching the barrier of space.

In GSLV’s case, the cryogenic stage was supposed to function from 4 minutes and 56 seconds of the flight until 18 minutes and 29 seconds, whereupon GISAT-1’s self-propulsion systems would have carried it into the final position, some 36,000 km away from the surface of Earth.

The payload satellite, GISAT-1 or EOS-3, had been described as a “game-changer” for India. The satellite will be placed far out of reach of any anti-satellite missiles and its high-resolution cameras will allow India to have real-time, constant monitoring of large areas of Earth.

This will be used for monitoring of natural disasters, episodic weather events like cyclones, cloud bursts and thunderstorms. The satellite will also capture and obtain spectral signatures for agriculture, forestry, and water bodies. The GISAT-1 satellite had been marred by delays due to the COVID-19 pandemic, having initially been slated for a March, 2020 launch.

ISRO will need to go back to the drawing board and ensure that its cryogenic upper stage engines work without fail. The development of a cryo engine is absolutely essential for other advanced space missions, like the upcoming manned spaceflight mission, Gaganyaan.

This was the eighth launch and third failure of the GSLV rocket. Meanwhile, ISRO had launched Brazil's earth observation satellite Amazonia-1 and 18 smaller co-passenger satellites in February this year.