'Now boarding' … 240,000 miles from Earth, at the moon's first airport

A new chapter is about to unfold in lunar exploration as the moon prepares to welcome its first airport. This orbital hub, known as the Gateway, will serve as a crucial launching pad for future missions to the moon and beyond. However, unlike traditional airports with concrete runways and aircraft, the Gateway will operate along a unique and invisible highway—known as a near-rectilinear halo orbit (NRHO).

Engineers from Texas A&M University, NASA's Johnson Space Center, and Purdue University have developed sophisticated algorithms and operational strategies to manage the complex traffic flow around the Gateway. Their work, published in Acta Astronautica, lays the foundation for a safe and efficient traffic management system for spacecraft navigating the challenging lunar environment.

The NRHO offers several advantages for lunar exploration. It provides an uninterrupted line of sight for communication with Earth, requires minimal propellant to maintain, and remains stable for extended periods. However, navigating this orbit is unlike anything humans have experienced before. The orbit is egg-shaped, swooping within 1,000 miles of the moon's north pole before extending nearly 40,000 miles beyond its south pole.

Spacecraft traveling along the NRHO must carefully manage their positions, as collisions and serious damage could occur in this dynamic environment. The researchers' algorithms consider factors such as navigation errors, thruster imperfections, and small disturbances that could arise during future Artemis missions. Their findings reveal that modest increases in station-keeping maneuvers allow spacecraft to stay closer to their intended positions while requiring minimal propellant use.

By maintaining carefully calculated intervals between spacecraft, the researchers propose a "string of pearls" formation around the Gateway. Similar to pearls on a necklace, spacecraft would line up naturally along the lunar orbit and relative to the Gateway. This arrangement minimizes the risk of vehicles drifting dangerously close together and enables efficient coordination of docking schedules and rendezvous operations.

The successful implementation of this traffic management system is crucial for creating a lasting human presence around the moon. It not only ensures the safety of crewed and robotic missions but also optimizes resources by reducing the need for excessive propellant consumption. As the moon's first airport takes shape, the intricate dance of spacecraft loitering in the NRHO will pave the way for future lunar exploration endeavors.