Numerical simulation of human orientation perception during lunar landing

Abstract

In lunar landing it is necessary to select a suitable landing point and then control a stable descent to the surface. In manned landings, astronauts will play a critical role in monitoring systems and adjusting the descent trajectory through either supervisory control and landing point designations, or by direct manual control. For the astronauts to ensure vehicle performance and safety, they will have to accurately perceive vehicle orientation. A numerical model for human spatial orientation perception was simulated using input motions from lunar landing trajectories to predict the potential for misperceptions. Three representative trajectories were studied: an automated trajectory, a landing point designation trajectory, and a challenging manual control trajectory. These trajectories were studied under three cases with different cues activated in the model to study the importance of vestibular cues, visual cues, and the effect of the descent engine thruster creating dust blowback. The model predicts that spatial misperceptions are likely to occur as a result of the lunar landing motions, particularly with limited or incomplete visual cues. The powered descent acceleration profile creates a somatogravic illusion causing the astronauts to falsely perceive themselves and the vehicle as upright, even when the vehicle has a large pitch or roll angle. When visual pathways were activated within the model these illusions were mostly suppressed. Dust blowback, obscuring the visual scene out the window, was also found to create disorientation. These orientation illusions are likely to interfere with the astronauts' ability to effectively control the vehicle, potentially degrading performance and safety. Therefore suitable countermeasures, including disorientation training and advanced displays, are recommended.