Space has a moment. China launched the first Tianhe module for its Tiangong space station this spring, and SpaceX followed shortly thereafter with the first crewed mission from US soil since 2011. In July, Virgin Galactic and Blue Origin launched sightseeing flights. suborbital with their business leaders on board. Almost every week, it seems, more and more private companies and governments are announcing new concepts, flights and projects.
Recent activity, while exciting, is causing some concern. The amount of space debris is increasing, despite the demands of deorbiting and disposing of satellites, and the problem will soon worsen. About 11,000 satellites have been launched in the 64 years since Sputnik 1 in 1957 (Exhibit 1).
We are now at the point where approximately 70,000 satellites could enter orbit if the proposed plans materialize – an explosion of interest based on potential new markets, innovative architectures and more sophisticated technologies (Exhibit 2). Even if not all of the proposed constellations deploy, many more satellites will be in space. Unless they are actively desorbed, they will stay there for months or even hundreds of years, depending on the altitude.
We looked at the space debris — what has been done so far, the growing risk, and the government’s response — to find solutions.
Beware of giant satellites and floating paint chips
What exactly is space debris? Many people think this phrase refers to a gigantic piece of metal about to crash into a big city, but only a few of the millions of objects in orbit are as big as the ancient rockets and space stations of the upper floor. Much of the rest is tiny particles, such as paint stains. The US space surveillance network was tracking around 20,000 debris in orbit in 2019 (Exhibit 3).
Today there are around 27,000 pieces of debris,
most of which are over ten centimeters in diameter. The trajectories of others – and what they might touch and when – are uncertain.
The US space surveillance network was tracking around 20,000 debris in orbit in 2019; today there are around 27,000 pieces. The trajectories of others – and what they might touch and when – are uncertain.
Considering the speed at which orbital objects move, even a collision between small debris and another object on a crossing path can be catastrophic. The International Space Station (ISS), designed to survive impacts from debris up to one centimeter in diameter, was damaged in May 2021 when an object of about five millimeters pierced a hole in the thermal coating of its robotic arm . The ISS, which had to maneuver repeatedly to avoid larger debris, suffered no functional damage, but the incident reminded us that even major space systems are vulnerable to impacts from tiny objects.
Don’t be surprised if crash reports increase over the next few years. There is only one object tracked for every 18 million cubic kilometers in low Earth orbit, but that number does not include small, potentially fatal debris, nor does it take into account the relatively higher density of objects in certain orbits. and the distance to each object. moves over a given time. These two factors increase the risk of a collision, even in a largely empty environment. Space debris cannot be controlled and can stay in the sky for centuries, depending on orbits and collision dynamics, so the problem will persist.
What goes up doesn’t necessarily go down
Experts have been discussing the problem of space waste since the 1960s, which led NASA’s Donald Kessler to write a groundbreaking 1978 report on the chain of reactions that could occur once debris has reached a certain level, a effect now called Kessler syndrome. A few high-profile crashes have also drawn attention to the issue. In 2007, China tested an anti-satellite weapon (ASAT) by intercepting a non-operational weather satellite (an FY-1C polar-orbiting satellite from the Fengyun series). The resulting explosion created a cloud of space debris with more than 3,000 objects, the largest ever.
Likewise, a collision in 2009 between the defunct Russian satellite Kosmos 2251 and a commercial communications satellite Iridium produced more than 2,000 pieces of debris.
Exhibit 4 shows the amount of debris created after some of the bigger collisions.
Governments and other agencies have come up with solutions to reduce space debris. The United States, for example, released a report in 2011 on debris reduction, and the United Nations recently created guidelines on the long-term sustainability of outer space activities.
Even more unusual, the G-7 Forum of Developed Economies issued a statement in June 2021 that underscored the growing danger of space debris and encouraged international cooperation to resolve the issue.
Overall, however, not much has changed over the past decade when it comes to taking concrete action.
Alien collisions can have serious economic consequences, and the increased use of space will further increase these costs. Many new satellites are housed in huge “mega-stellations” that eclipse previous systems, and their number could increase tenfold over the next five to ten years.
Time to take out the alien trash
So what can be done to mitigate the risk of collisions as the amount of debris increases? Our analysis suggests that we need solutions that take into account four main categories of objects:
- Active satellites. They are not debris, but their increasing number, and their potential increase by an order of magnitude, is of real concern. Operators can reduce the risk of collisions with satellites by improving situational awareness, coordinating with other operators to perform evasive maneuvers and creating “end of life” disposal requirements.
- Uncontrollable dead satellites and other large objects (like upper stages and rocket bodies). These items cause the greatest damage and potential chain effects, but they also offer the greatest potential for feedback on debris removal measures.
- Minor debris that cannot be tracked. A mitigation measure could involve the creation of satellites that are more likely to survive certain impacts.
- Small debris that is being tracked (or will be when the sensors improve). Operators are now maneuvering active satellites around this debris, but disposal technologies may be worth exploring, as discussed below.
Addressing the problem of space debris requires a multitrack approach. National and international government agencies now require satellite operators to have a phase-out plan before issuing a constellation license, but other measures could go very far. NASA has already set up a task force to examine new roles the agency can take on to mitigate the growth of orbital debris and promote the sustainability of space.
Regulatory and licensing bodies could also encourage greater collaboration between operators to reduce collisions.
With regard to situational awareness (tracking satellites and reporting their movements), government agencies and private companies could drive progress through various measures, such as adding sensors (on the ground and in the air). space) with higher resolution.
Finally, active clearance of space debris may be possible in some cases. A startup recently started a test mission to prove it had the capabilities required for docking and clearing space debris.
Other debris mitigation efforts will likely focus on removing inactive satellites and larger intact objects, at least initially. OneWeb, for example, has announced plans to collaborate with Astroscale on debris removal, and SpaceX has also discussed the possibility of using its Starship to clean up space debris.