Simone D’Amico, science fellow at the Hoover Institution, is associate professor of aeronautics and astronautics, the W. M. Keck Faculty Scholar in the School of Engineering, and professor of geophysics (by courtesy) at Stanford University. He is the founding director of the Stanford Space Rendezvous Laboratory, founding codirector of the Center for Aerospace Autonomy Research (CAESAR), and director of the undergraduate program in aerospace engineering at Stanford.
Simone, you’ve often referred to a challenge called the “space sustainability paradox.” What exactly is this paradox?
The space sustainability paradox highlights the tension between two different dimensions: the sustainability enabled by space and the sustainability of humankind’s use of space. On one hand, we’re relying ever more heavily on satellites for critical applications like the Global Positioning System, or GPS, for navigation, space-based internet such as Starlink for communication, and the creation of a virtual “digital twin” of Earth. The digital twin is constructed from remote sensing data that can be used for things such as monitoring humans’ impact on the environment, forecasting the weather, and managing responses to natural disasters. These technologies contribute to safety and sustainability on Earth, and they’re important for national security and defense purposes too. All this activity can be described as sustainability enabled by space.
On the other hand, we can only get these and other benefits because we’re launching ever more assets into space, which raises the question of how we can ensure the sustainable use of near-Earth space itself, which is a finite resource. Currently, more than 34,000 objects larger than 10 centimeters are actively tracked in Earth’s orbit, and they include about 10,000 working satellites, spent rocket bodies, and other debris. Many thousands more satellites could be added over the next few years. Additionally, statistical models estimate there are a million objects between 1 centimeter and 10 centimeters in size in orbit that we are not able to track with current technology from the ground. Even small objects like these can cause considerable damage given the immense speed at which they are moving. Space has become increasingly congested, and the proliferation of satellites is making the problem of debris worse.
The paradox lies in the fact that the very growth of space activities that support Earth’s sustainability may simultaneously threaten sustainable access to space. In the current absence of globally agreed-upon rules for space traffic management, the risks of collisions in Earth’s orbit rises, which threatens the long-term usability of space for future generations.
2. What are some of the potential consequences for humankind if we can’t find ways to resolve the space sustainability paradox? How soon are we likely to encounter these?
If we don’t resolve this paradox, there are several significant consequences that could impact humankind within the next few years to several decades.
Collisions and other issues that increase space debris and degrade space assets would make it harder for us to observe and study Earth from space. For instance, without reliable satellite infrastructure, our ability to predict and manage natural disasters such as hurricanes, wildfires, and floods would be diminished, and the human and economic costs caused by these events would increase.
Many of our defense systems also rely on space-based assets for surveillance, communication, and precision navigation. Unchecked space debris and a lack of agreed-upon traffic management guidelines could disrupt military satellites and lead to increased geopolitical tensions as countries vie for control of safe orbital regions that have relatively little or no debris.
There’s also a worst-case scenario called the Kessler syndrome. This refers to a situation in which an event triggers a cascade of collisions in Low Earth Orbit, or LEO, which is a region less than 1,000 kilometers in altitude, where most satellites are to be found. The chain reaction could create a cloud of debris in space that makes entire orbits unsafe for use for decades or centuries, severely limiting access to space for all kinds of missions.
3. Are there technological solutions that could help us address this critical challenge?
Yes, there are. Let me give you a couple of examples that my colleagues and I are working on at Stanford’s new Center for Aerospace Autonomy Research, which is known by its acronym, CAESAR.
First, technologies that enable spacecraft to operate autonomously can be combined with artificial intelligence (AI) to better manage space activities. Autonomous operation can help satellites and other space assets avoid collisions, service and repair other vehicles in orbit, and remove space debris, all without human intervention. At the same time, AI-driven algorithms can optimize the trajectories of spacecraft so they can better anticipate and respond to evolving conditions in space, such as threats posed by orbiting debris. AI’s ability to process vast amounts of data incredibly fast means it can help spacecraft respond to threats in real time and reduce risks caused by human error.
Then there are space domain awareness, or SDA, technologies that can be deployed both on the ground and in space. When deployed in space, SDA refers to multiple interconnected satellites that detect, track, and predict the movement of resident space objects. Such distributed systems in orbit can complement ground tracking technologies that are used today. These are certainly useful but have major limitations, such as the lack of full-sky coverage and limited resolution. By using AI and advanced sensors, SDA systems can help us better manage traffic in space by, for instance, anticipating satellites’ trajectories and giving early warnings of potential collisions.
4. Commercial companies have become very active players in the space domain over the past couple of decades. What are the implications of this for the space sustainability paradox?
The growing involvement of commercial companies is a double-edged sword. On the positive side, they’ve driven rapid innovation in space technologies, creating more efficient and affordable solutions. They’ve deployed vast satellite constellations that enhance our ability to monitor the Earth, improving weather forecasting, disaster response, and environmental monitoring. They’ve also helped create a more resilient space-based infrastructure for communication, navigation, and surveillance systems that benefit various sectors, from agriculture to defense. Finally, private-sector investment has accelerated the development of autonomous spacecraft technology and techniques for debris removal and in-space servicing of assets—all of which can help address some of the sustainability challenges we’ve been talking about.
However, the negative implications are equally significant. The surge in commercial satellite launches, particularly for megaconstellations with thousands of small satellites, is contributing to the crowding in LEO and making debris and collisions more likely. The proliferation of commercial actors also makes coordinating activities more difficult, especially without a unified and globally coordinated traffic-management system for space today. We really are operating in a celestial Wild West!
5. What are examples of steps you think decision makers in government should be taking to tackle the space sustainability paradox?
I think governments should prioritize establishing a comprehensive traffic-management framework that enforces global standards for satellite operations and mitigating space debris. This would require strict enforcement measures such as financial penalties and launch restrictions for noncompliant operators to ensure that all commercial and government entities adhere to protocols for collision avoidance and responsible orbital use. Recent policy initiatives by the United Nations, such as the Space Agenda 2030, and by the European Union, such as the Zero-Debris Charter, are timid steps in the right direction, but they are certainly not enough without actions taken by state actors to enforce them.
Governments should also foster private-public partnerships to accelerate the development of debris-removal technologies and autonomous systems, offering incentives such as tax-exempt financing to encourage companies to invest in these solutions. And they can promote sustainable satellite design, including mandatory requirements to incorporate responsible deorbiting plans at the end of satellites’ useful lives to ensure they don’t contribute to the space debris problem.
We also need governments to work through international bodies such as the United Nations Office for Outer Space Affairs to create binding agreements on securing the sustainability of space. To foster a circular space economy—by which I mean one where satellites and spacecraft are specifically designed for reuse, repurposing, repair, and efficient end-of-life deorbiting—policymakers and regulators could offer incentives to companies that design recyclable satellites (or modular ones, with some parts that can be reused) as well as impose penalties on designs likely to contribute to more space debris. This system of incentives and penalties could be realized through a “space tax”—similar to a “carbon tax”—that is based on the estimated orbital-environmental impact of a space mission. If we combine regulation, innovation, and international collaboration, we can secure the future benefits of continued scientific, commercial, and defense activities.
6. Those steps all sound sensible, but might there be some practical hurdles? For instance, space has become an important domain for the military. How do we deal with issues such as antisatellite missile tests that can create space debris?
Practical hurdles, such as the militarization of space, do pose significant challenges to implementing effective space sustainability measures. Antisatellite, or ASAT, missile tests that intentionally destroy satellites, creating lots of debris, are a major concern, and they highlight the tension between national security interests and the need to better manage the overall environment in space. Addressing this requires international agreements that not only regulate commercial activities but also set strict limits on military actions in space, including bans or moratoriums on ASAT tests. Diplomatic efforts, such as arms control treaties for space, will be critical to reducing debris generated by these activities while balancing this effort with national security concerns.
However, even if we can get such agreements—and I believe we must try to do so—enforcing them will be difficult because of the strategic importance of space assets for defense and intelligence operations. So, we’re going to need multilateral trust-building and transparency measures, including satellite tracking data–sharing agreements and third-party verification mechanisms. We’re also going to need to encourage greater collaboration between military and civil space agencies that can help reduce risks associated with military operations in space.
7. What additional research areas are there that you think could help us resolve the space sustainability paradox?
We’re going to need to prioritize several key research areas. Advanced propulsion and deorbiting technologies are key for developing systems that enable satellites to maneuver effectively and to reliably and safely take themselves out of orbit at the end of their operational lives. Also, research into in-orbit manufacturing and recycling could help advance a circular space economy by enabling the repair, repurposing, and construction of spacecraft in orbit using materials sourced from defunct satellites. This would reduce debris and the need for frequent launches.
We also need to develop AI-enhanced space traffic–management algorithms that will be crucial for predicting and preventing collisions in crowded orbits, and we need to do more research into the design of satellite constellations to make these more sustainable using modular and scalable networks that can operate with fewer satellites. All this work needs to be complemented by research into international space governance that’s focused on legal frameworks for enforcing the responsible use of space and addressing liability for debris generation. There’s certainly a great deal to be done, but I’m optimistic that by focusing on these issues we can ultimately resolve the space sustainability paradox.
