Science & Tech

Unrestrained Re-entries of Satellites

Many dignitaries have signed an open letter published by the Outer Space Institute (OSI) urging national and multilateral efforts to limit uncontrolled re-entry of satellites back to Earth.

Open Space Institute (OSI)

  • OSI is a conservation organisation dedicated to preserving scenic, natural, and historic landscapes for public enjoyment, conserving habitats while preserving community character, and assisting in environmental protection.
  • It achieves its objectives through policy initiatives and grassroots activism.

Stages of a rocket launch

  • Rockets have several stages.
  • The rocket sheds a stage after it has increased the rocket’s altitude and velocity by a certain amount.
  • Some rockets burn up all of their larger stages before reaching their final orbit; a smaller engine then propels the payload to its final orbit.
  • Others carry the payload into orbit, then begin their descent with a deorbit manoeuvre.
  • Rocket stages fall back down in both cases, either controlled or uncontrolled.

Uncontrolled re-entry

  • It is the phenomenon of unguided rocket parts falling back to earth after their missions are completed.
  • The rocket stage falls in an uncontrolled re-entry.
  • Its descent path is determined by its shape, angle of descent, air currents, and other factors.
  • As it falls, it will also disintegrate.

Number of satellites in space

  • In 1957, the Soviet Union launched the first artificial satellite.
  • Today, there are over 6,000 satellites in orbit, the majority of which are in low-Earth (100-2,000 km) and geostationary (35,786 km) orbits and were launched in over 5,000 launches.
  • With the introduction of reusable rocket stages, the number of rocket launches has increased dramatically.

Why is this hazardous?

  • The potential radius of impact on the ground increases as the smaller pieces fan out.
  • Some pieces completely burn, while others do not.
  • However, due to the speed at which they travel, debris can be lethal.
  • If re-entering stages still contain fuel, another risk is chemical contamination in the atmosphere and on the ground.

Uncontrolled re-entry damage control mechanism

  • There is no international binding agreement to ensure rocket stages always perform controlled re-entries, nor is there one on the technologies to do so.
  • The 1972 Liability Convention requires countries to pay for damages rather than prevent them.
  • Wing-like attachments, de-orbiting brakes, extra fuel on the re-entering body, and design changes that reduce debris formation are among the technologies used.
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