As NASA prepares for humanity’s first lunar spaceport, engineers are developing a traffic control system to keep spacecraft moving safely and efficiently.
Within the next two decades, NASA’s planned Gateway could become humanity’s first lunar spaceport, serving Orion crew capsules, lunar landers, cargo vehicles, and astronauts traveling between Earth, the moon, and eventually farther into deep space.
Unlike an airport on Earth, Gateway will have no runways, taxiways, or gate announcements. Spacecraft will instead move through an invisible network shaped by the gravity of Earth, the moon, and the surrounding region of space, where trajectories are governed by precise mathematical rules.
Managing that traffic will require its own form of orbital air traffic control.
Engineers from Texas A&M University, NASA’s Johnson Space Center, and Purdue University have developed algorithms and operating strategies for spacecraft waiting near Gateway and for managing multiple vehicles moving through the same orbital environment.
Their work provides mathematical guidelines and orbital “rules of the road” intended to help several spacecraft share this difficult region safely and predictably.
The findings, published in Acta Astronautica, examine how to balance fuel use with operational needs while lowering the risk of spacecraft collisions.
“The future of lunar exploration depends as much on the traffic management as it does on the rocket science,” said Dr. Diane Davis, associate professor of space engineering at the Texas A&M University College of Engineering, and an author of the study.
Gateway’s orbit creates a traffic challenge
Establishing a sustained human presence near the moon will require more than simply reaching it. Spacecraft will also need an infrastructure that allows them to occupy and move through the same gravitational environment without interfering with one another.
For Gateway and the spacecraft visiting it, that environment centers on a Near Rectilinear Halo Orbit, or NRHO.
“The Gateway NRHO is a nearly stable and highly elongated orbit around the moon that provides an uninterrupted line of sight for communications to Earth and requires little propellant to maintain,” Davis said.
Gateway and nearby vehicles will nevertheless experience constantly changing gravitational pulls from both Earth and the moon as they travel along this elongated orbit.
The trajectory is also unlike any orbit previously used for crewed spacecraft. It brings Gateway to within 1,000 miles of the moon’s north pole before carrying it nearly 40,000 miles beyond the south pole.
A single station can remain on course with occasional thruster burns. The situation becomes more complicated when an Orion crew capsule, an uncrewed cargo vehicle, and a large lunar lander may all need to approach, dock, depart, or wait in the same region.
“Collisions and serious damages could happen. To ensure crew safety and mission success, effective traffic management in the NRHO is crucial,” Davis said.
Loitering keeps spacecraft safely separated
One of the central ideas behind that traffic system is loitering, which means carefully maintaining a spacecraft in relation to a particular orbit or trajectory while it waits.
“Loitering in space means maintaining a spacecraft relative to a specific orbit or trajectory without executing an immediate maneuver,” Davis said.
The basic concept resembles airport traffic management. Aircraft may wait at gates, pause on taxiways, or circle before receiving permission to proceed.
Spacecraft approaching Gateway could face similar delays. A vehicle might need to wait for hours, days, or even weeks before a docking port becomes available or another mission finishes.
The major difference is that there is no fixed surface and every vehicle remains in motion.
“Every spacecraft is constantly moving,” Davis said. “It’s a Goldilocks zone of keeping ‘parked’ vehicles far enough from each other to be safe, but close enough to their destination so that resources are used efficiently.”
Determining that balance was a central goal of the research.
Using thousands of computer simulations, the engineers tested ways to keep spacecraft properly separated around Gateway while incorporating realistic navigation errors, imperfect thruster performance, and small disturbances that future Artemis missions could experience.
The simulations showed that modest increases in station-keeping maneuvers could keep spacecraft substantially closer to their planned positions while requiring only small changes in propellant use.
“Greater positional accuracy means mission planners can better predict where every spacecraft will be, preserving valuable fuel,” Davis said.
Knowing where each vehicle should be makes it easier to coordinate docking times, plan rendezvous operations, and reduce risks for both crewed and robotic missions.
“Every maneuver has a cost,” Davis said. “Just like air traffic control on Earth, spacecraft need predictable positions and paths to safely coordinate their movements.”
Greater predictability would also simplify the complicated sequence of spacecraft arriving at and departing from Gateway.
A formation could organize lunar traffic
Instead of allowing visiting vehicles to wait independently, spacecraft could remain at carefully calculated positions ahead of or behind Gateway until they are cleared to dock or depart. The researchers describe this arrangement as a “string of pearls” formation.
“Similar to the arrangement of pearls on a string necklace, spacecraft would arrange themselves naturally along the lunar orbit and relative to Gateway,” Davis said. “Maintaining the loitering vehicle relative to the Gateway enables a closer formation and reduces the risk of vehicles drifting dangerously close together.”
The change may appear small, but it could provide an important framework for managing increasingly complicated operations around the moon.
“It’s the beginning of a new kind of traffic control,” Davis said. “An exciting frontier in planning the infrastructure for an entire transportation system.”
For Davis, orbital traffic planning builds directly on years of mission design and astrodynamics work.
Before joining the Aerospace Department at Texas A&M University in 2026, she spent more than a decade at NASA’s Johnson Space Center, where she served as a principal engineer and mission design lead for Gateway.
As an associate professor, Davis now studies cislunar astrodynamics and space traffic management while also preparing students for the increasingly complex lunar missions that may accompany a permanent human presence around the moon.
“Nothing excites me more than training and developing future engineers and scientists,” Davis said. “It’s an incredible opportunity, because they’ll be the ones planning lunar missions and managing space traffic for humanity beyond Earth.”
If travel to the moon eventually becomes routine, keeping that traffic moving safely will depend on more than rockets and spacecraft. It will also rely on the mathematical rules that determine who waits, who moves, and how vehicles remain safely separated nearly 240,000 miles from Earth.
Reference: “Cislunar traffic management: Orbit maintenance and loitering in the Gateway NRHO” by Diane C. Davis, Brian P. McCarthy, Stephen T. Scheuerle, Emily M. Zimovan-Spreen and Kathleen C. Howell, 3 June 2026, Acta Astronautica.
DOI: 10.1016/j.actaastro.2026.06.006
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