Cryogenic Upper Stage of LVM3 Makes a Re-entry

Relevance: GS3, Space Technology, Indian Space Research Organization, ISRO, Chandrayaan-3, LMV3, Indigenization of Technology & Developing New Technology, Space Debris, 25-year Rule

Why in the news?

• Recently, the cryogenic upper stage of the LVM3 M4 launch vehicle, used in India's Chandrayaan-3 moon mission, made an uncontrolled re-entry into the Earth's atmosphere.
• The probable impact point predicted is over the North Pacific Ocean.

Chandrayaan-3 Mission – An Overview

• Chandrayaan-3 was launched on July 14, 2023, using the LVM3 M4 launch vehicle.
• The spacecraft was successfully injected into an orbit of 133 km x 35823 km with a 21.3° inclination.
• The key objectives of Chandrayaan-3 are:
  • Technological Demonstration: To demonstrate the capability to perform a soft landing on the lunar surface and operate a robotic rover.
  • Scientific Exploration: To conduct scientific experiments using instruments onboard the lander and rover, focusing on lunar surface studies.
• Chandrayaan-3 aims to contribute significantly to our understanding of the moon's topography, mineralogy, and lunar regolith (moon soil).
• It also showcases India's growing capabilities in space technology and exploration.
• The mission serves as an inspiration for future deep space missions and stimulates advancements in space technologies.
• On August 23, India achieved a milestone by becoming the fourth country to successfully land on the moon and the first to land in the moon's polar region.

Cryogenic Upper Stage Re-entry

• Cryogenic upper stage re-entry refers to the process where the cryogenic upper stage of a rocket re-enters the Earth's atmosphere after completing its mission in space.
• The cryogenic upper stage re-entered Earth's atmosphere in an uncontrolled manner.
• The re-entry happened 124 days after the launch.
• The stage's post-mission orbital lifetime was in line with the "25-year rule" for Low Earth Orbit (LEO) objects, as recommended by the Inter-Agency Space Debris Coordination Committee (IADC).

Significance of Cryogenic Upper Stage Re-entry Process

• End of Mission: Typically, a cryogenic upper stage re-entry occurs at the end of a space mission, after the stage has successfully delivered its payload (like a satellite or spacecraft) into orbit.
• Orbital Decay: Re-entry can happen due to orbital decay. After fulfilling its role, the upper stage remains in orbit for a period, gradually losing altitude due to the faint atmospheric drag in low Earth orbit (LEO) or due to gravitational perturbations and other forces acting upon it.
• Controlled vs. Uncontrolled Re-entry:
  • Controlled Re-entry: Ideally, the re-entry of a rocket stage is controlled, where the stage is deliberately guided back to Earth to land in a predetermined area. This minimizes the risk of debris causing damage or harm.
  • Uncontrolled Re-entry: In some cases, the re-entry is uncontrolled, meaning the stage returns to Earth's atmosphere without guidance. This can happen if the stage lacks the capability to perform a controlled descent or if there's a malfunction.

• Atmospheric Disintegration: During re-entry, the cryogenic upper stage typically disintegrates due to the intense heat and friction generated as it moves through the atmosphere at high speeds.
• Space Debris Concern: The re-entry of such stages is a concern in the context of space debris management. Controlled re-entries are preferred to minimize the risk of debris falling in populated areas.
• Compliance with Space Debris Mitigation Guidelines: Many space agencies adhere to international guidelines (like the 25-year rule for de-orbiting inactive satellites and rocket stages in LEO) to minimize space debris. Part of this involves ensuring that end-of-life stages re-enter the atmosphere and pose minimal risk.
• Safety Measures: Measures like passivation (removing or neutralizing leftover fuel and disabling batteries to prevent explosions) are often taken to minimize risks associated with re-entry.

What is Space Debris?

• Space debris, also known as space junk, refers to defunct human-made objects in space that no longer serve any useful purpose.
• This includes non-functional spacecraft, abandoned launch vehicle stages, mission-related debris, and fragments from the disintegration, erosion, and collision of space objects.
• These objects typically orbit the Earth, just like operational satellites. Their orbits can vary from Low Earth Orbit (LEO), where most of the debris is concentrated, to Geostationary Earth Orbit (GEO) and even beyond.
• Space debris poses a significant risk to space operations, as collisions with even small debris at high velocities can cause considerable damage to satellites, spacecraft, and the ISS.

Measures Taken by ISRO for Space Debris Mitigation

• Compliance with the "25-year rule": The cryogenic upper stage of the LVM3 M4 launch vehicle re-entered the Earth's atmosphere within 124 days of its launch.
  • This is in full compliance with the "25-year rule" for Low Earth Orbit (LEO) objects recommended by the Inter-Agency Space Debris Coordination Committee (IADC).
  • This rule is a guideline suggesting that space objects in LEO should deorbit within 25 years of the end of their mission to reduce long-term space debris.
• Passivation of the Upper Stage: After the successful injection of Chandrayaan-3 into its intended orbit, ISRO undertook the passivation of the upper stage of the launch vehicle.
  • Passivation involves the removal of all residual propellants and energy sources from the spent stage of the rocket.
  • This process is crucial to minimize the risks of accidental explosions, which can create additional space debris.
• Adherence to International Guidelines: ISRO's actions in the disposal of the rocket body and passivation process were in adherence to the space debris mitigation guidelines prescribed by the United Nations and the IADC.
  • These guidelines are designed to preserve the long-term sustainability of outer space activities by minimizing the creation of space debris.
• Controlled Re-entry and Impact Prediction: Although the re-entry of the rocket body was uncontrolled, ISRO predicted the probable impact point over the North Pacific Ocean.
  • The agency also ensured that the final ground track of the re-entry did not pass over India, indicating measures taken to predict and track the re-entry path for safety and debris impact assessment.

Conclusion

The safe and compliant conclusion of the Chandrayaan-3 mission's launch phase marks a significant achievement for ISRO and India's space program. It underscores India's ongoing commitment to responsible space exploration and adherence to global standards in space missions.