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23rd December 2022 (8 Topics)

The uncontrolled re-entries of satellites

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 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 and then perform a deorbit manoeuvre to begin their descent.
  • In both cases, rocket stages come back down — in controlled or uncontrolled ways.

The 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 make minimum 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.
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