Oceans apart, India's Chandrayaan-3 rocket 'LVM3 M4' now sleeps in the sea

All expendable spacefaring rockets have the same fate: part by part, they eventually end up in the sea and sleep with the fishes, in different oceans along the rocket's flight path.

Once in the sea, some are washed ashore, some are caught in fishing nets and some remain in the depths forever. Some rocket stages (that complete their task and burn out within the earth's atmosphere) splash down during the progress of the launch mission itself.

But the upper stage of the rocket, which is responsible for injecting the satellite into its precise orbit continuesits stay in spaceas a piece of space debris. Given that these rocket upper stages remain in unstable orbits, they are eventually dragged towards the earth's atmosphere, makingan uncontrolled re-entry, burning up in the earth's atmosphere and touching down in oceans, or in rare cases, on land.

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The latest piece of space debris to undergo this process is the upper stage of India's LVM3-M4 rocket, which carried the Indian moon mission Chandrayaan-3 to its intended initial orbit.

The cryogenic upper stage (the cylindrical portion just below the rocket's nose cone) of the LVM3 M4 launch vehicle made an uncontrolled re-entry into the Earth’s atmosphere, onWednesday (Nov 15) at 14:42 hrs (IST; 9:12 AM GMT, Thursday), said the Indian Space agency ISRO.

The probable impact point was predicted over the North Pacific Ocean, it is said.

Launched on July 142023, the LVM3-M4 rocket completed its launch mission in almost 17 minutes.

The Cryogenic upper stage, which remained suspended in space as a piece of debris,has now taken its place in the ocean, almost three months after the launch.

Also watch |All about Chandrayaan-3 mission

As suggested by the Inter-Agency Space Debris Coordination Committee (IADC), the post-mission orbital lifetime of such objects must be within 25 years.

Therefore, with this upper stage having been removed from orbit in less than just about three months, the process is compliant with the "25-year rule", ISRO said.

Post Chandrayaan-3 injection, the upper stage had also undergone “passivation” to remove all residual propellant and energy sources to minimise the risks of accidental explosions as per the space debris mitigation guidelines prescribed by the United Nations and IADC.

Passivation and Post-mission disposal of this rocket body in adherence to the internationally accepted guidelines once again reaffirms India’s commitment to preserving the long-term sustainability of outer space activities, ISRO added.

A rocketupper stage contains unused fuel in its tanks, there are also batteries, self-destruct systems etc. A malfunction in one of these could lead to an explosion and it would create a lot of small and large pieces of space debris, which are harder to keep track of.

Therefore, space agencies are required to ensure that the rocket upper stage is "passivised". That means, all onboard sources of the stored energy of a spacecraft or orbital stage, such as residual fuels, batteries, high-pressure vessels, self-destructive devices, flywheels and momentum wheels, should be "depleted" or "safed" when they are no longer required for mission operations or post-mission disposal.