Shooting for the moon

In an edited extract from The Launch of Rocket Lab, PETER GRIFFIN outlines the high-risk solution that kept a lunar mission on track.

-  PETER GRIFFIN

In 2017, Nasa formally revealed plans for Artemis, a followup programme to the famed Apollo missions of the 1960s, which aimed to land humans back on the Moon in the 2020s. The centerpiece of the plan was the Gateway space station, that would operate in orbit around the Moon as a place for astronauts to live and work between trips to the lunar surface. Like the International Space Station, Gateway would serve as a habitation module, scientific lab and communications hub. The US was finally going back to the Moon, but extensive preparations for Gateway were needed to identify an appropriate lunar orbit for the first space station that would ever orbit the Moon. The “Capstone” (Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment) mission's primary objective was to test and verify the calculated orbital stability of the Near Rectilinear Halo Orbit (NRHO) around the Moon - the orbit planned for Gateway.

It was calculated to give Gateway and spacecraft docking with it the best combination of fuel efficiency and a pathway to the lunar surface. As Nasa explained: “Hanging almost like a necklace from the Moon, NRHO is a one-week orbit that is balanced between the Earth's and Moon's gravity. This orbit will periodically bring Gateway close enough to the lunar surface to provide simple access to the Moon's South Pole where astronauts will test capabilities for living on other planetary bodies, including Mars.”

The orbit also gives astronauts access to other landing sites around the Moon. A CubeSat [miniature satellite] would need to be launched into lunar orbit to gather data that would help Nasa decide exactly how to position Gateway.