How To Deorbit the International Space Station

At Solar MEMS we are committed to the sustainability of the space environment and the importance of keeping space debris in LEO to a minimum. In this article we want to explain the plans to deorbit the International Space Station, the largest man-made space object ever made, which has been in use for 25 years and is planned to be deorbited in January 2031.

The growing concern among New Space companies and space agencies to keep the debris in LEO to a minimum has highlighted the importance of ensuring that the International Space Station is deorbited in a safe and sustainable way. This is a highly delicate job that NASA and Roscosmos have been working on since 2011 and in its latest report the US agency announced “the last budget estimate for extending the working life of the ISS until 2030 and assumes the deorbiting in January 2031”

The ISS has been orbiting our planet since 1998 and its total mass of over 400 metric tons make it the largest ever man-made space object, and it is due to be decommissioned in the near future. The International Space Stations will need help to achieve this, because its own propulsion capacity is not strong enough, so that it will use that of the visiting vehicles as well.

How the ISS will be deorbited

NASA has made the ‘Transition Report on the International Space Station’ public, in which it explains the details of how it aims to bring the working life of the ISS to an end.

The plan consists of using a controlled re-entry to the Earth over a safe area of the Pacific Ocean called “Point Nemo”, which is the most remote spot in the ocean, around 2688 kilometres from the nearest land. This place is known as “the cemetery of spacecraft” because it has already been used on other occasions to dispose of the remains of US, Russian, Japanese and European spacecraft. The spot lies between New Zealand and the north of Antarctica.

“The chosen approach for decommissioning is a combination of natural orbital decay and the execution of a re-entry maneuver for final targeting and to control the debris footprint”, said NASA. “Once all crew have safely returned to Earth and after performing small maneuvers to line up the final target ground track and debris footprint over the South Pacific Oceanic Uninhabited Area (SPOUA -the area around Point Nemo), space station operators will perform a large re-entry burn, providing the final push to lower station as much as possible and ensure safe atmospheric entry into the target footprint.”

Based on the behaviour of other structures that have returned to Earth, like the Mir, it is expected that most of the ISS hardware will burn up when it enters the atmosphere in the intense heat, while the denser and more hard-wearing, heat-resisting components like the outer shell will survive re-entry and fall into the remote area selected in the South Pacific.

In short, some of the ISS components will burn up or disintegrate in its re-entry into the atmosphere, and whatever is left will fall at “Point Nemo” and sink to the bottom.

Why has NASA decided to deorbit the ISS this way?

The system planned by NASA and Roscosmos is based on research and the experience acquired from other missions that reached the end of their working life. Even so, the size of the International Space Station is a factor that must be considered when preparing this operation. Therefore, the US agency decided to use a modus operandi which is safe for the public and astronauts and which will reduce the creation of space debris to a minimum, a pressing problem for the sector.

One of the options discussed was to dismantle the station and return it to Earth, but the ISS was never intended to be dismantled and has been extended by the addition of new components like the folding solar panels and Russian Nauka and Prichal modules, so the dismantling would require an enormous financial cost and human effort to achieve.

Another option was to push the International Space Station out into a higher orbit beyond the LEO, but this solution, which has been used on other occasions, is feasible for smaller satellites but not for large structures like the ISS, which is the size of a football pitch (it measures around 109 metres by 73 metres).

The option for a Random v Controlled Re-entry, was considered, but this would entail high risks because it could not be guaranteed that the debris that survived re-entry into the atmosphere would fall on an uninhabited area.

This is all we know at present about the plans to deorbit this enormous spacecraft, although there is still a lot of time and industry is advancing rapidly, so we should be on the lookout for news and ideas that can be applied to this ambitious plan that will bring one of the most important international scientific collaborations in history to an end.

(Photo: European Space Agency)