Context

More than 140 experts have signed an open letter published by the Outer Space Institute (OSI) calling for both national and multilateral efforts to restrict uncontrolled re-entries.

About

About Outer Space Institute (OSI):

• It is a network of world-leading space experts united by their commitment to highly innovative, transdisciplinary research.
• Comprised of physical scientists, social scientists, lawyers, engineers, industry leaders, and policymakers.
• It breaks down barriers that prevent people in different fields from working together.

What are the stages of a rocket launch?

• Rockets have multiple stages.
• Once a stage has increased the rocket’s altitude and velocity by a certain amount, the rocket sheds it.
• Some rockets jettison all their larger stages before reaching the destination orbit.
  • a smaller engine then moves the payload to its final orbit
  • Others carry the payload to the orbit, then perform a deorbit manoeuvre to begin their descent.
• In both cases, rocket stages come back down — in controlled or uncontrolled ways.

What is an uncontrolled re-entry?

• It is the phenomenon of rocket parts falling back to earth in an unguided fashion once their missions are complete.
• In an uncontrolled re-entry, the rocket stage simply falls.
• Its path down is determined by its shape, angle of descent, air currents, and other characteristics.
• It will also disintegrate as it falls.
• As the smaller pieces fan out, the potential radius of impact will increase on the ground.

Why are scientists worried about the re-entries?

• Striking Land instead of Oceans: Parts of a Russian rocket in 2018 and China’s Long March 5B rockets in 2020 and 2022 had fallen into Indonesia, Peru, India, and the Ivory Coast.
• If re-entering stages still hold fuel, atmospheric and terrestrial chemical contamination is another risk.
• Increasing Risk: The casualty risk from uncontrolled rocket body re-entries as being on the order of 10% in the next decade.
• Disproportionate Risk: Countries in the ‘Global South’ face a “disproportionately higher” risk of casualties.

Is there any international agreement for safer re-entries?

• There is no international binding agreement to ensure rocket stages always perform controlled re-entries.
• The Liability Convention 1972 requires countries to pay for damages, not prevent them.

What can minimize the damage?

• Bodies aim for an ocean to avoid human casualties.
• A re-entry notification plan and a retrieval plan.
• Using the techniques like:
  • wing-like attachments
  • de-orbiting brakes, and extra fuel on the re-entering body
  • design changes that minimize debris formation
• Design-for-demise solutions to modify the characteristics of spacecraft components:
  • Changing the material of a tank to make it demisable.
• Using smaller satellites: They experience more atmospheric drag than if they had been bigger, and are likelier to burn up during re-entry.