Supercomputer Study Finds 97,000 Stable Orbits Between Earth and Moon

Lawrence Livermore National Laboratory (LLNL) conducted a study which utilized supercomputers to create a simulation that tested one million theoretical satellite orbits between Earth and the Moon. Fewer than 10% of these cislunar orbits maintained stability throughout six years of observation. The process of satellite placement beyond low Earth orbit presents difficulties which require a solution. The study identified 97000 orbits as operational, from which future missions could select multiple workable routes.

High-performance simulations

According to the study, LLNL scientists employed two of their most powerful supercomputers, Quartz and Ruby, to simulate one million cislunar orbits. The simulation took approximately 1.6 million CPU hours (or about 182 years of computing time) but was completed in only three days because of parallel processing. The researchers chose not to assume any particular orbit in their simulation but instead considered a broad range of initial conditions to characterize the cislunar space. According to lead author Travis Yeager, the researchers chose to ‘pretend we knew nothing' about this area to make sure that no orbits were assumed in advance.

Results and implications

For comparison, the low Earth orbit is already saturated with satellites, and the estimated number of 100,000 is likely the maximum before the risk of collision sets off a chain reaction. The overwhelming number of orbits was unstable, with only about 9.7% of the orbits remaining stable for the entire six years. Still, this represents about 97,000 stable orbits in the earth-moon system, which is a significant number of options for satellite placement. The authors point out that even the unstable orbits are useful data.