How NASA is prepping for lunar traffic jams
Popular Science...
Managing air traffic on a global scale requires juggling a dizzying combination of logistics, international regulations, and environmental variables. But in the not-too-distant future, commercial plane travel could feel quaint when compared to the organizational efforts needed to run humanity’s first lunar spaceport.
If all goes as planned, NASA hopes to have the Gateway installation up and running on the moon within the next 20 years. Once operational, the revolutionary orbital transportation nexus will ferry astronauts, cargo, and scientific equipment all headed to the moon’s first permanent lunar base. Setting aside everything involved in building such a vast structure, Gateway will only function safely so long as it runs on precise mathematical and gravitational calculations that simply isn’t necessary for air travel on Earth.
As researchers explain in a study recently published in the journal Acta Astronautica, these systems will all relate back to a route called the Near Rectilinear Halo Orbit (NRHO). The largely stable orbital path offers the most fuel efficient cosmic highway and an interrupted line of sight between spacecraft and mission specialists back home.
That won’t make harnessing the NRHO simple by any stretch, however. The NRHO will need to follow a highly elongated, egg-shaped loop that passes within 1,000 miles of the moon’s north pole. It will then round its turn about 40,000 miles past the lunar south pole. Thanks to physics, Gateway as well as any crew or cargo will also constantly contend with the gravitational struggle between Earth and the moon.
Then there is lunar “rush hour” to consider. Planning a single spacecraft’s trip to the moon is (relatively) straightforward, but what about when multiple crews are simultaneously en route to the moon? Just like commuting to work or taxiing on an airport runway, planning the solution comes down to loitering.
“Loitering in space means maintaining a spacecraft relative to a specific orbit or trajectory without executing an immediate maneuver,” Diane Davis, a study co-author and Texas A&M University space engineer, said in a statement.
On Earth, vehicles at rest remain at rest—at least relatively speaking. Loitering in space will involve combating orbital physics for days or even weeks at a time.
“Every spacecraft is constantly moving,” Davis explained. “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.”
Davis and her colleagues from NASA and Purdue University ran thousands of computer simulations to identify the best ways to keep multiple spacecraft loitering safely near Gateway, while also including inevitable variables like thruster issues and navigational errors. They concluded that a handful of new maneuvers are necessary to ensure vehicles remain as close to their intended spots as possible. These can then be stacked as the spacecraft queue lengthens around Gateway. Davis likens the calculations to arranging a string of pearls on a necklace.
“Spacecraft would arrange themselves naturally along the lunar orbit and relative to Gateway,” she said.
Although it sounds straightforward on paper, the concepts remain incredibly complex to translate into multibillion dollar missions with dozens of lives on the line. It might not sound as dramatic as actually launching from Gateway for a lunar rendezvous, but it’s just as vital to the future of human space travel.
“The future of lunar exploration depends as much on the traffic management as it does on the rocket science,” said Davis.
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