Livermore, California — Recent simulations conducted by scientists at Lawrence Livermore National Laboratory reveal striking insights into the viability of positioning satellites in cislunar space, the area between Earth and the moon. The supercomputer models suggest that if a million satellites were deployed in this region, fewer than 10% would remain stable long enough to justify the effort of launching them.
The burgeoning number of satellites orbiting Earth poses a dilemma as private initiatives, such as SpaceX’s Starlink and China’s Thousand Sails, continue to launch numerous spacecraft. Experts estimate that low Earth orbit (LEO) could support about 100,000 satellites before becoming over-saturated, risking catastrophic collisions known as Kessler syndrome. This scenario could render future space missions impossible.
As LEO grows crowded, researchers are turning their attention to cislunar space. Not only could satellites positioned there enhance global communications, but they could also support human settlements on the moon. However, the complexity of this venture is compounded by challenges in predicting the orbits of spacecraft influenced by the gravitational forces of both Earth and the moon, along with the sun’s more distant pull. The lack of Earth’s magnetic shield also allows hazardous radiation to disrupt potential satellite paths.
To explore these challenges, the LLNL team employed two powerful supercomputers, Quartz and Ruby, to simulate the trajectories of 1 million hypothetical satellites. The immense computational workload involved—approximately 1.6 million CPU hours—would have taken a single computer roughly 182 years to complete, but the task was accomplished in just three days.
The results showed that around 54% of the simulated orbits maintained stability for at least a year, yet only about 9.7% succeeded throughout the entire six-year simulation period. This finding, detailed in the journal Research Notes of the AAS, emphasizes the unpredictability of cislunar orbits compared to LEO, where paths are more stable and consistent.
Research lead Travis Yeager highlighted the uncertainty involved, noting that existing equations cannot precisely predict the position of a cislunar satellite over a week. Instead, calculations must proceed in incremental steps, making the process highly intensive. Yeager emphasized the importance of not making prior assumptions, stating that the simulations were designed to explore a broad range of potential orbits.
One of the unexpected factors influencing these trajectories was Earth’s gravitational variability. Yeager explained that the planet’s shape impacts gravitational forces, creating subtle shifts in gravity depending on location. This complexity makes orbit prediction even more challenging, as regions like Canada experience different gravitational pulls compared to areas over the Atlantic Ocean.
Despite the modest percentage of stable orbits, the research indicates there are approximately 97,000 viable paths for satellites in cislunar space, opening avenues for future exploration. Understanding both successful and unsuccessful trajectories generates valuable data for comprehending how these orbits behave.
The researchers have made their orbital trajectory data available on an open-source platform, providing a resource for future studies and foster collaboration in the burgeoning field of cislunar satellite exploration. The findings signify not only the challenges of deploying satellites in this uncharted arena but also a promising outlook for advancing human presence beyond Earth.