In News
- An open letter published by the Outer Space Institute (OSI) calls for both national and multilateral efforts to restrict uncontrolled re-entries of rockets and satellites.
- The Outer Space Institute (OSI) is a network of world-leading space experts that aims to address challenges arising from the use and exploration of space. It is based in Canada.
Uncontrolled re-entry
- Uncontrolled re-entries 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 downward path 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.
Concerns about the re-entries
- Speed: More than size, it is the speed at which space debris is travelling, which makes them deadly.
- Rise in launches: The number of rocket launches has been surging with the advent of reusable rocket stages. Today, there are more than 6,000 satellites in orbit, most of them in low-earth (100-2,000 km) and geostationary (35,786 km) orbits, placed there in more than 5,000 launches.
- Impact on Land: Most rocket parts have landed in oceans principally because the earth’s surface has more water than land. But many have dropped on land as well.
- Population: The risks from uncontrolled re-entries are growing as the global population grows. Many places have become more densely populated. Conservative estimates place the casualty risk from uncontrolled rocket body re-entries as being on the order of 10% in the next decade.
- North vs South: Countries in the ‘Global South face a “disproportionately higher” risk of casualties than the ‘Global North’.
- Impact on Airlines: An impact anywhere on an airliner with the debris of mass above 300 grams would produce a catastrophic failure, meaning all people on board would be killed.
- Chemical Contamination: If re-entering stages still hold fuel, atmospheric and terrestrial chemical contamination is another risk.
Examples
- Parts of a SpaceX Falcon 9 that fell down in Indonesia in 2016 included two “refrigerator-sized fuel tanks”.
- Parts of a Russian rocket in 2018 and China’s Long March 5B rockets in 2020 and 2022 hit parts of Indonesia, Peru, India and the Ivory Coast, among others.
Is there any international agreement to tackle it?
- There is no international binding agreement to ensure rocket stages always perform controlled re-entries nor on the technologies with which to do so.
- The Liability Convention 1972 requires countries to pay for damages, not prevent them.
1-in-10,000 threshold
- Some states has adopted a safety threshold of one predicted casualty per 10,000 launches (0.01%), above which controlled re-entries are supposed to be required.
- This means launches should keep the chance of a casualty from a re-entering body to be below 0.01%.
Criticism of 1-in-10,000 threshold
- But this threshold is arbitrary and not widely accepted internationally.
- Even those states that use it have often waived the requirement on multiple occasions when compliance is deemed to be unreasonably expensive.
- Most importantly, the 1-in-10,000 threshold does not account for cumulative risks from all launches over a period of time.
- This threshold makes little sense in an era when new technologies and mission profiles enable controlled re-entries.
Recommendations by OSI to minimize damage
- While the OSI letter admits that any kind of re-entry will inevitably damage some ecosystems, it recommends that bodies aim for an ocean in order to avoid human casualties.
- Future solutions should be extended to re-entering satellites as well.
- The focus should be on developing and using smaller satellites as they are likelier to burn up during re-entry.
Source: TH
