What are IN-SPACe re-entry guidelines | Explained

The story so far: On July 30, the Indian National Space Promotion and Authorisation Centre (IN-SPACe) released a set of guidelines called ‘Authorisation for Undertaking Planned Re-entry of Space Objects’. These guidelines provide a new framework for how companies and government agencies must handle the reentry phase of a space mission.What is a planned re-entry?Objects in orbit or the upper atmosphere can fall back to the earth due to gravity. Most often these are spent rocket stages, dead satellites, and orbital debris, and all of them frequently tumble back in an uncontrollable manner. If they are not particularly large, they burn up in the atmosphere — but if they are or are made of heat-resistant materials, they can crash on the surface.The guidelines pertain to planned re-entry, which is a subset of re-entries from space. A planned re-entry is deliberate and where an operator uses particular engines and/or specific manoeuvres to say exactly how, where, and when an object will hit the atmosphere and subsequently descend to the surface.Planned re-entry involves a complex series of processes and demands precise calculations to ensure the object does not skip off the atmosphere like a stone on water, burn up too quickly or descend at the wrong location.What is survivability?While much of the public attention is focused on how rockets go up, how they and the satellites they carry come back down presents a particular scientific and regulatory challenge.To this end, the IN-SPACe guidelines include a survivability analysis. When an object re-enters the atmosphere, it is typically travelling at several kilometres per second. Its outer surface suffers friction with the air, generating an intense amount of heat — thousands of degrees celsius are not unheard of — which could vaporise most materials.However, some components, such as titanium tanks, stainless steel bolts, and heavy engine parts are deemed survivable because they are often tough enough to reach the ground intact. And the IN-SPACe guidelines require operators to submit a fragmentation pattern — essentially a map that shows the changes of how a spacecraft will break apart under the thermal stress of re-entry and where those fragments will fall.If a spacecraft is designed to burn up completely, it may not need a special re-entry permit. But if it is designed to survive — such as a capsule bringing an experiment back from the International Space Station or a reusable rocket stage — the operator must prove they can land it safely.What is the safety threshold?Spaceflight is never zero-risk, so the IN-SPACe guidelines establish a scientific threshold for safety, a kind of maximum allowable risk. Per the guidelines, the risk of a person being hit by a re-entering object must be lower than 1 in 10,000 (or 0.01%).This threshold risk is actually an international standard that India is now formalising. The Inter-Agency Space Debris Coordination Committee (IADC) — the leading international forum for coordinating activities related to human-made and natural debris in space — published its first ‘Space Debris Mitigation Guidelines’ in 2002. The UN Committee on the Peaceful Uses of Outer Space endorsed them three years later. In the 2010s, then, major space agencies including NASA and the European Space Agency began to adopt their rules.NASA in particular was the first to codify the Guidelines’ 1-in-10,000 limit into its NASA-STD 8719.14 safety manual, and which many other nations later adopted as well.What does the maximum risk entail?To keep the risk from crossing this figure, operators will have to use sophisticated software to model the re-entry corridor — the path of the re-entering object — accounting for wind speed and directions, the atmosphere’s density, and the potential debris footprint, i.e. the area on the ground or sea where the fragments might land.For example, an operator may ‘virtually’ crash their satellite thousands of times and based on the flight data estimate which parts will survive the heat of re-entry. Then they overlay the crash zone with global population density maps. If the probability of any of those surviving chunks hitting a person is higher than 0.01%, the mission will be considered unsafe.Also, if a satellite fails this test, the operator will not be allowed to let it fall back naturally but must instead perform a controlled re-entry: using the fuel remaining onboard to steer the object into a remote area — perhaps the ‘Spacecraft Cemetery’ in the South Pacific Ocean where the risk to humans is essentially nil.The guidelines also require operators to coordinate with other forms of travel. So before a planned re-entry, an operator must obtain an advisory note from IN-SPACe, which will be used to issue ‘Notices to Airmen’ (NOTAMs) and Navigation Area warnings for ships (NAVAREAs), basically ‘no-fly’ or ‘no-sail’ zones.By coordinating with aviation and maritime authorities in this way 45 days in advance, the government will be able to ensure the debris footprint steers clear of airplanes and ships, protecting people.How do the guidelines frame liability?Beyond the physics of re-entry, the guidelines address a longstanding legal lacuna: who pays if something goes wrong? Under the international Liability Convention of 1972, a country is responsible for any damage its space objects cause to other countries. The new guidelines protect Indian taxpayers by pinning this responsibility on the private operators themselves.Specifically, any entity that is planning a re-entry must have third-party liability insurance. If a piece of a private satellite hits a building in another country, the company — and its insurers — must also indemnify the Government of India.The resulting policy aim seems to be that while India encourages space innovation, it will also remain a responsible space power on the global stage.The guidelines’ timing is not entirely accidental as India is currently working on its human spaceflight mission, dubbed ‘Gaganyaan’, which involves bringing human astronauts safely back to earth. Several Indian startups are also developing reusable launch vehicles and orbital platforms that will return to earth after completing their missions.Without such guidelines, experts have said the return leg of space travel could be a legal and scientific Wild West.