All expendable spacefaring rockets have the same fate: part-by-part, they eventually end up in the sea and sleep with the fishes, at 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 burnout 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 would continue its stay in space, as a piece of space debris. Given that these rocket upper stages remain in unstable orbits, they are eventually dragged towards the earth’s atmosphere, make an uncontrolled re-entry, burn up in the earth’s atmosphere and impact in the oceans, or in rare cases, on land.
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, on Wednesday (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 14th 2023, the LVM3-M4 rocket completed its launch mission in almost 17 minutes.
The Cryogenic upper stage which remained as a piece of debris from this mission has now taken place, 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 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 preserve the long-term sustainability of outer space activities, ISRO added.
A rocket upper 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 on-board sources of 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.
