Imagine launching a million satellites into the vast expanse between Earth and the Moon, only to discover that most of them wouldn't even last long enough to be worth the effort! That's the startling revelation from cutting-edge supercomputer simulations that have mapped the complex dance of celestial bodies. While this might sound like a cosmic catastrophe, it actually sheds crucial light on the intricate challenges of expanding humanity's presence beyond our home planet.
In recent years, our skies have become incredibly crowded with an unprecedented surge in active spacecraft. This boom is largely driven by private companies launching massive satellite "megaconstellations," like the well-known Starlink network from SpaceX and China's rapidly expanding Thousand Sails project. And this is just the beginning of the trend.
Once Earth's low-Earth orbit (LEO) is fully utilized, the next frontier for satellite deployment is the fascinating region known as cislunar space – the area stretching between our planet and the Moon. This expansion holds immense promise, not only for enhancing our planet's infrastructure but also for providing essential services like internet access to future lunar colonies.
However, navigating cislunar space presents a significantly greater challenge than LEO. The orbits of spacecraft here are far more unpredictable because they are caught in a constant gravitational tug-of-war. This celestial battle involves the combined pull of Earth, the Moon, and the Sun. And here's where it gets particularly tricky: the Sun's influence becomes more dominant the farther an object is from Earth. Furthermore, without Earth's protective magnetic shield, the intense radiation from our Sun can easily disrupt and destabilize orbital paths in this region.
To tackle this complex problem, researchers at the renowned Lawrence Livermore National Laboratory (LLNL) in California harnessed the power of two of their formidable supercomputers, Quartz and Ruby. They ran simulations tracking the trajectories of approximately 1 million objects in cislunar space. This monumental task required an astonishing 1.6 million CPU hours – a feat that would have taken a single computer an estimated 182 years to complete! Astonishingly, the supercomputers crunched through this data in a mere three days.
Out of all the simulated orbits, a respectable 54% managed to remain stable for at least a year. But here's the part most people miss: only a mere 9.7% of these satellites maintained stable orbits throughout the entire six-year simulation period. The detailed findings of this orbital analysis were published in August 2025 in the journal Research Notes of the AAS, with a preliminary version of the team's analysis also available on the preprint server arXiv since December. (It's worth noting that the preprint paper has not yet undergone peer review.)
The researchers deliberately designed the simulated trajectories to be as expansive and varied as possible. Their goal was to encompass a wide spectrum of potential scenarios, including those they couldn't even anticipate. As study lead author Travis Yeager, a research scientist at LLNL, explained, "The point of it was to not assume anything about what types of orbits we want. We tried to go into it pretending we knew nothing about this space."
Uncertain Orbits: A Cosmic Riddle
Unlike the relatively stable and predictable orbits in LEO, cislunar orbits are characterized by a high degree of uncertainty. This complexity meant the research team had to employ a more computationally intensive method, advancing their calculations in small, discrete time steps. "If you want to know where a [cislunar] satellite is in a week, there's no equation that can actually tell you where it's going to be," Yeager elaborated. "You have to step forward a little bit at a time."
One of the most unexpected factors influencing these orbits, the researchers discovered, is the subtle but significant impact of Earth's gravitational pull. This pull isn't uniform; it shifts as our planet rotates. "The Earth is not a point source," Yeager emphasized. "It is actually blobby." He provided a fascinating example: gravity is weaker over Canada than it is over the Atlantic Ocean due to these variations.
While the percentage of surviving satellites in the simulation might seem low, the results still translate to an impressive 97,000 stable orbits within cislunar space. This opens up a vast array of possibilities for future exploration and utilization of this region. The team highlighted that understanding which orbits don't work is just as invaluable as knowing which ones do. "From a data-science point of view, this is an interesting data set," Yeager remarked. "When you have a million orbits, you can get a really rich analysis."
To foster further research and innovation, the scientists have made their orbital trajectory data publicly available on an open-source platform, allowing anyone to access and utilize it for future studies on cislunar satellites.
This research raises a compelling question: Given the inherent instability of cislunar orbits, are we truly prepared for the ambitious expansion of our orbital infrastructure, or are we venturing into a realm where the celestial mechanics present a more formidable challenge than we initially anticipated? What are your thoughts on the future of space exploration in cislunar space? Do you agree with the researchers' approach to understanding these complex orbits, or do you believe there are other factors that should have been considered?
