Characterization of the Apollo Astronaut Lunar Extravehicular Activity Falls and Near-Falls

Abstract

The Apollo astronauts that set foot on the moon performed extravehicular activities (EVAs) that included traverses, collecting samples, and running experiments that provided knowledge about our planet, the moon, and our universe. During these EVAs, the astronauts were observed to fall, which could lead to risk of injury to the astronaut or damage to the space suit. The Apollo-era spacesuits had mobility limitations that affected task performance, including decreased range of motion, restorative forces of the suit based on soft-goods deformations, and an altered center of mass primarily due to the portable life support system (PLSS). It is possible that these mobility limitations coupled with the reduced gravity environment of the moon led to falls, although it is not documented what aspects of their tasks may have triggered falls. We analyzed the video and audio transcripts from all the Apollo lunar EVAs to characterize when in the timeline a fall or near fall occurred, as well as what task was being performed at the time of the event. Here a fall was defined as impact with the ground (other than the boot) and a near-fall was when the astronaut required corrective actions but was able to recover without impacting the ground. A total of 48 events (27 falls and 21 near-falls) were catalogued. Of these events, 32 occurred during sample collection or equipment interaction (inclusive of local reorientation steps), 5 occurred while mounting or dismounting the lunar rover, 5 occurred during a general traversal, and 6 had other causes (e.g., playing, throwing a non-tool object, transitioning between tasks, unknown off-video). The events that occurred during general traversals were initiated by stepping on rocks, craters, or surface inclines. The events were distributed across the timeline of the EVA, with a greater number of events during the 25-75% of the EVA duration (32 total events) than for the beginning and end periods (16 total events). While events did occur during traversals, task activities generated events, including retrieving tools, connecting and avoiding cables, setting up experiments, picking up items off the ground, and reorienting in the local environment to continue the task. These data highlight the importance of interactions with equipment and task goals on fall risk. Improved suit designs that increase mobility will address some of these events; however, future missions should consider how tools, equipment, and local reorientation are used within tasks to mitigate future risks.