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Intuitive Machines<\/a>\u2019 first lunar lander officially lost power today<\/span><\/a> after spending seven days on the moon. The lander made history for being the first American hardware to reach the lunar surface since 1972 and the first privately built spacecraft to land on the moon. But the lander, called Odysseus, will be remembered for another reason: its propulsion system.<\/p>\n That propulsion system, which uses a combination of cryogenic liquid oxygen and liquid methane, could unlock new capabilities in space and de-risk future missions by other commercial providers.<\/p>\n Before Intuitive Machines\u2019 IM-1 mission, no lander had ever used this combination of propellants. If they sound familiar, it\u2019s because they\u2019re used in high-performance rocket engines, like SpaceX\u2019s Raptor, Blue Origin\u2019s BE-4 and Relativity Space\u2019s Aeon R.<\/p>\n But landers \u2014 and most spacecraft today \u2014 use \u201cspace storable\u201d or hypergolic propellants, like hydrazine or nitrogen tetroxide, which can be passively stored but are highly toxic. In contrast, \u201ccryogens\u201d are more efficient, higher energy and considerably less dangerous, but they must be actively cooled to very, very low temperatures.<\/p>\n This presents some unique challenges. Because the fuels must be kept so cold, they can only be stored prior to lift-off for a very short amount of time. To get around this issue, Intuitive Machines and SpaceX started fueling the Nova-C class lander\u2019s VR900 engine (which was built by IM) just three hours before lift-off, when the rocket was on the launch pad and the spacecraft was already inside the payload fairing. This is anything but typical.<\/p>\n It\u2019s so out-of-the-ordinary that SpaceX had to develop entirely new capabilities to fuel the lander, Bill Gerstenmaier, SpaceX\u2019s VP of build and flight reliability, said during a press conference on Feb. 13. That included modifying the launch pad, the second stage of the Falcon 9 rocket, and adding an adapter to access the payload fairing when it was already mated to the vehicle.<\/p>\n The two companies performed two wet dress rehearsals prior to launch; issues with propellant loading resulted in the first launch attempt being pushed by a day, to Feb. 15. After the successful launch<\/a>, Intuitive Machines\u2019 also ran into a brief issue chilling the liquid oxygen feed line, which took longer than anticipated. Once the propellant was sufficiently cooled, flight controllers successfully fired the engine in space for the first time the following day.<\/p>\n Because the company was using liquid oxygen and liquid methane, which are highly efficient, they were able to take a more direct trajectory to the moon. The spacecraft only had to transit the Van Allen belt, a high-radiation zone around the Earth, once, which reduced the spacecraft\u2019s exposure to damaging high-energy particles.<\/p>\n Two VR900 engines will also be used on Intuitive Machines\u2019 much larger \u201cNova-D\u201d spacecraft, to deliver 500-750 kilograms of payload to the moon. (The Nova-C lander has a payload capacity of 100 kilograms.)<\/p>\n