In this orbital configuration, it should take about five days for spacecraft from Earth to reach Gateway. That’s a bit longer than the three-day journeys taken by Apollo astronauts, but a near-rectilinear halo orbit will be a good way to conserve energy. A moderate maneuver will be required to decelerate spacecraft rendezvousing with Gateway, providing a more cost-effective and energy-efficient way of delivering equipment, supplies, parts, and personnel to the outpost.

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“In human spaceflight we don’t fly one single, monolithic spacecraft,” explained Florian Renk, a mission analyst at NASA and ESA’s Operations Centre (ESOC), in a statement. “Instead we fly bits and pieces, putting parts together in space and soon on the surface of the Moon.”

Artist’s depiction of Gateway over the Moon.
Artist’s depiction of Gateway over the Moon.
Image: ESA/NASA/ATG Medialab
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Gateway will slowly come together over the course of several years. NASA will use a combination of private rockets and its own Space Launch System (SLS) rocket to deliver the components required to build the lunar outpost. As we learned yesterday, however, NASA will likely push the inaugural launch of SLS from 2020 to 2021, as Ars Technica reported.

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That’s not great news for a program that’s slated to put people on the Moon a scant three years later, but that’s the timeline NASA has been ordered to deal with. Sadly, politics is becoming a large part of the equation, as NASA struggles to deal with aggressive due dates and budgetary ambiguities. Hopefully sense will prevail such that the 2020s will prove to be as exciting for human space exploration as we’re expecting.

Correction: A previous version of this post incorrectly used the terms perihelion and aphelion, which are specific to objects orbiting around the Sun. The correct terms in this case are perilune and apolune. We regret the error. Thanks to commenter Brianorca for pointing this out.