The International Space Station (ISS) is counting down its days, with retirement just a few years away hanging over the orbital lab. For more than 20 years, the space station served as a home for astronauts in low Earth orbit, but it will soon meet its demise as it plummets through the atmosphere, leaving behind small fragments of an iconic legacy.
NASA is working on a plan to deorbit its beloved space station in 2030 and send it through Earth’s atmosphere, where much of it will burn up from the heat of re-entry. The space agency, along with its international partners, has been looking at several options, narrowing them down based on feasibility and cost. After years of effort, NASA decided to enlist the private sector to design a spacecraft that will tow the space station to its fiery death.
The ISS is a big boy, holding the record for the largest man-made structure in space. At 357 feet (109 meters) long, it’s about the size of a football field and will be the largest object ever recovered from space. Bringing down the ISS won’t be easy, and ensuring that the remaining pieces land far from populated areas is the biggest challenge. Here’s a look at how NASA and its partners plan to bring the storied space station to its final resting place.
Why is NASA dropping the ISS?
NASA and its partners began assembling the space station in 1998. The ISS has served as a critical platform for scientific research and new technology demonstrations in microgravity that have often been used on Earth. The space station symbolizes international cooperation and peace, and demonstrates the collaboration between the space agencies of the United States, Russia, Europe, Japan and Canada. It has hosted hundreds of astronauts from 18 different countries, who have completed more than 270 spacewalks.
Alas, all good things must come to an end. The ISS is getting old, and the wear and tear of being in space has taken its toll. Tellingly, its retirement paves the way for commercial use of low Earth orbit, with private companies designing their own space stations to take over once the ISS is gone.
Russia has agreed to continue sending its cosmonauts to the ISS until 2028 while it builds its own space station in orbit. Since its inception, the ISS has continuously hosted at least one NASA astronaut and one Roscosmos cosmonaut. Over the years, Russian Soyuz and Progress vehicles have flown numerous crew and cargo missions to the ISS. The Russian space agency will likely take these toys with it when it departs, meaning NASA will be without its main ISS partner for the decommissioning task.
The space station will have to be destroyed, because taking it apart is simply not practical. “The station was never designed to be taken apart again,” Marco Langbroek, a lecturer in astrodynamics at Delft University of Technology in the Netherlands, told Gizmodo in an email. “I think the current plan is the only option available.”
The initial assembly of the space station took 27 missions using NASA’s now-retired Space Shuttle. Taking the ISS apart piece by piece would require a massive effort by NASA, international space agencies and their astronauts, in addition to having a spacecraft large enough to bring those parts back to Earth.
“Any disassembly attempt to safely disconnect and replace individual components (such as modules) would face significant logistical and financial challenges, requiring at least an equivalent number of [spacewalks] by the space station crew, extensive planning by ground crews, and a spacecraft with a capacity comparable to the large payload bay of the space shuttle, which does not currently exist,” NASA wrote in a recent report.
The space agency added that it is developing a conservation plan for some of the ISS’s smaller items. That makes sense; the station is full of souvenirs and artifacts worth preserving.
The path to destruction
Rather than let the space station return to Earth uncontrolled, NASA and its partners should choose a remote uninhabited area of the ocean as a landing site for the remaining debris. Standard practice for space debris mitigation accepts a risk of human casualties of less than 1 in 10,000.
Before the deorbiting process takes place, the ISS will be emptied of all movable cargo that can be transported back to Earth. ISS astronauts will also have to evacuate the space station before it deorbits, leaving the orbital lab empty for the first time in decades. Someone—we don’t know who, of course—will be the last astronaut floating within its comfortable confines.
A controlled reentry always begins with lowering a spacecraft’s orbit. The first step toward reentry will be to cancel the periodic orbital burns that maintain the lab’s position at about 250 miles (400 kilometers) above sea level. Eventually, the station’s orbit will drop below 150 miles (250 kilometers), Langbroek said. This natural orbital decay, caused by atmospheric drag, will likely take months to gradually bring the ISS down, he explained.
The SpaceX Factor
For the next step, the space agency has tasked SpaceX with designing a new deorbit vehicle. This vehicle will dock with the ISS and perform a series of deorbit burns to further lower the space station’s orbit (NASA had previously proposed using Russia’s Progress cargo spacecraft to deorbit the ISS, but that is now off the table). In March, the space agency released its 2024 budget proposal, which included $180 million to develop a deorbit capability for the ISS by the end of 2030. At the time, NASA had estimated that its ISS tug would cost about $1 billion in total.
The recently awarded SpaceX contract is worth $843 million, which covers development of the vehicle but not launch costs. The company has not shared details about the design of its space tug, and it is not clear whether it could reuse its Dragon spacecraft or build a different one altogether. The exorbitantly priced tug is a single-use spacecraft and will not survive the deorbit mission. While SpaceX “will develop the deorbit spacecraft, NASA will assume ownership of it after development and operate it for the duration of its mission,” NASA wrote. “Along with the space station, it is expected to destructively break up as part of the reentry process.”
Safe and controlled return
Using its brand-new tug, the ISS will need to perform a large reentry burn to precisely determine its reentry location. This will ensure a controlled descent through the atmosphere to manage its debris footprint. The thrust maneuver must be strong enough to put the spacecraft into an elliptical orbit, or an oval-shaped path, so that it is properly captured by the atmosphere, said Tobias Lips, managing director of satellite aerodynamics company Hyperschall Technologie Göttingen in Germany.
“If you have a maneuver strong enough to move your perigee, [minimum altitude] “In principle, down to zero, then the uncertainties of the distribution of your fragments on the ground play a smaller role,” Lips told Gizmodo. “If you accept a higher perigee altitude, then the potential splashdown zone, which encompasses all the uncertainties, becomes larger and larger.”
The reentry expert estimates that about 40% of the ISS will survive the heated journey through the atmosphere, but that NASA will have sufficient control over the splashdown zone. While a significant amount of material may fall from space, it probably won’t land near populated areas.
Destruction of an icon
The ISS will enter the atmosphere at speeds of up to 17,500 miles per hour (28,000 kilometers per hour). Once the space station descends below 60 miles (100 kilometers), it will break apart, Langbroek said. During its fatal dive, the famous structure will deform, its familiar contours falling apart piece by piece, the metal bending under the pressure.
“External elements such as solar panels and antennas will likely break off first, after which the main structure of the station will break into fragments,” Langbroek said. “Most of these will burn up, but some significantly denser and more massive components, such as docking ports and parts of the truss structure, will likely survive.”
The pieces of the ISS that survive re-entry are likely to make up 10% to 20% of its total mass. That’s more than 180,000 pounds (81,646 kilograms) of material, which is why a controlled re-entry is essential. This may seem obvious, but the smaller the spacecraft, the fewer fragments will survive re-entry. As Lips explained, smaller objects are heated more intensely and are more likely to break apart upon re-entry due to their compact size, while larger objects are less likely to completely disintegrate, making it difficult for them to break up completely.
The remaining ISS fragments will crash into an empty area of the southern Pacific Ocean known as the Spaceship Graveyard, whose bottom is home to many dead satellites (including the Russian space station Mir, which crashed to Earth in 2001). The remote area of the Pacific Ocean, called Point Nemo, lies between New Zealand and South America and is the furthest point from the mainland.
Related article: Skylab, the first American space station, changed what we thought was possible in space
In 1979, the first American space station, Skylab, disintegrated in Earth’s atmosphere, scattering debris across the Indian Ocean and Western Australia. NASA calculated that there was a 1 in 152 chance that the remaining fragments would hit people on the ground. Fortunately, no injuries were reported.
It’s hard to imagine the beloved ISS shattered into pieces and crashing into the Pacific Ocean, but its legacy will far outlive the incinerated fragments. The destruction of the space station marks the end of an era and the beginning of a new era that relies more on the commercialization of space. With this new era, the Earth’s orbit will undergo significant changes.
Correction: An earlier version of this article stated the wrong year of Skylab’s return; it was 1979, not 1973.
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