More than 140 experts and dignitaries have signed an open letter published by the Outer Space Institute (OSI) calling for both national and multilateral efforts to restrict uncontrolled re-entries. The Outer Space Institute is a trans-disciplinary international institute dedicated to space studies. 

 

Details

  • The Outer Space Institute (OSI) has published the International Open Letter on Reducing Risks from Uncontrolled Re-entries of Rocket Bodies.
  • The Open Letter calls on governments to negotiate a multilateral agreement requiring controlled re-entries.
  • It also wants Nations to demonstrate leadership by immediately and unilaterally committing to national controlled re-entry regimes.
  • The letter states that the conservative estimates place the casualty risk from uncontrolled rocket body re-entries as being on the order of 10% in the next decade.
    • The U.S. Orbital Debris Mitigation Standard Practices (ODMSP) require all launches to keep the chance of a casualty from a re-entering body to be below 0.01%.
  • It also emphasises that countries in the Global South’ face a “disproportionately higher” risk of casualties.

 

Background

  • 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 (throw away) 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.

 

Uncontrolled re-entry

  • In an uncontrolled re-entry, the rocket stage simply falls. Ground stations usually lose control on such rockets.
  • 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.
  • Some pieces burn up entirely while others don’t. But because of the speed at which they’re travelling, debris can be deadly.
  • Most rocket parts have landed in oceans principally because earth’s surface has more water than land. But many have dropped on land as well.

 

Recent examples of uncontrolled re-entry

  • Parts of a Russian rocket in 2018 and China’s Long March 5B rockets in 2020 and 2022 striking parts of Indonesia, Peru, India and Ivory Coast, among others.
  • In October 2022, ISRO’s RISAT-2 satellite made an uncontrolled re-entry in the Indian Ocean near Jakarta.
  • Parts of a SpaceX Falcon 9 that fell down in Indonesia in 2016 included two refrigerator-sized fuel tanks.

 

Associated dangers

  • Any kind of re-entry will inevitably damage some ecosystem and there is also an associated risk of human causalities on the ground as well.
    • A 2021 report of the International Space Safety Foundation said, an impact anywhere on an airliner with debris of mass above 300 grams would produce a catastrophic failure, meaning all people on board would be killed.
  • If re-entering stages still hold fuel, atmospheric and terrestrial chemical contamination is another risk.

 

International Regulations

  • There is no international binding agreement to ensure rocket stages always perform controlled re-entries nor on the technologies with which to do so.
    • These technologies include wing-like attachments, de-orbiting brakes, extra fuel on the re-entering body, and design changes that minimise debris formation.
  • The Liability Convention 1972 requires countries to pay for damages, not prevent them.