VibroLink: A Wireless Vibro-Auditory Transmission System to Improve Situational Awareness During EVA

We define tacit knowledge as non-verbalized, intuitive, and unarticulated knowledge. It is non-declarative knowledge of the world, based on embodied experience, as opposed to explicit, declarative knowledge. For example, declarative knowledge might include how to spell the word “swing”; it is the knowledge we can easily convey to others. This is in contrast to the activity of swinging. While most of us know how to swing, articulating what exactly one needs to do to set a swing in motion is challenging.

Polyani [12] introduced the term “Tacit Knowledge” to describe the ability to do something without being able to articulate how to do it: this includes riding a bicycle or playing a musical instrument, without having the ability to fully explain all details of how it is done. Polyani claims that all practical skills rely upon tacit awareness. We extend this to incorporate knowledge about the world, as this is the foundation of any skill. For example, both riding a bicycle and swinging in a swing require a tacit understanding of physics.

Such tacit understanding of the world is also related to domain-specific knowledge, for example, many technicians rely on auditory and visual cues to detect failure on complex machinery [15]. Another documented case is craftsmen from a renowned Japanese denim brand, who claim that they share a unique bond with their machines, relying solely on auditory cues to calibrate them. This tacit understanding of the machinery is built over time and has been handed down through generations [14]. Research is only beginning to explore making such knowledge explicit, for example, by training machine-learning models to identify acoustic cues for fault diagnosis [17].

In this work, we assume that astronauts have a rich body of tacit knowledge of materiality and physics, which includes understanding vibration feedback, be it tactile or audible, and having the ability to infer what caused it. Our work aims to leverage such knowledge to make EVAs safer and more effective.

At the time of this writing, it has been over 60 years since Alexei Leonov floated in free space on March 18, 1965. This event is considered the first human EVA – an activity conducted by an astronaut in outer space outside a spacecraft. EVAs include spacewalks as well as lunar or planetary surface exploration, such as moonwalks. According to a 2004 NASA report [5], in the four decades following Leonov’s EVA, humans spent approximately 900 hours in microgravity and over 160 hours on the lunar surface performing EVAs. The same report highlights the following key areas for improvement in future EVAs: (1) all subsystem designs should prioritize simplicity and reliability based on fundamental principles, favoring these over added functionality in case of trade-offs; and (2) methods are needed to support and maintain high levels of mental performance during EVAs.

Conducting EVAs is extremely mentally challenging. A large part of EVA training focuses on cognitive preparedness, often described as “putting on your EVA brain.” Success relies heavily on planning actions and movements in advance [4]. Several factors contribute to these challenges. For example, vibration and auditory cues are absent in the vacuum environment. Additionally, bulky suits constrain movement and act as sensory insulators. The design of current space suits – ranging from 10 to 30 mm in thickness and composed of up to 16 layers – significantly reduces both audible and tactile feedback [8]. These limitations impair the astronaut’s ability to perceive non-visual cues, grasp objects, and maintain proprioception. As a result, cognitive performance can decline, increasing the risk of accidents [15].

In contrast, access to sensory feedback has been shown to improve task performance and reduce cognitive load in complex environments [16, 9]. Based on this, researchers have explored ways to reintroduce sensory input in space contexts. For example, Berengueres [2] demonstrated that enabling sound transparency during Intravehicular Activities (IVAs) can mitigate sensory deprivation and improve cognitive performance. However, their approach requires complex instrumentation of the astronaut’s environment.

We propose the vibroLink concept as a way to enhance sensory access and improve situational awareness during EVAs. The system provides EVA pilots with a means to leverage their tacit material knowledge and supports sustained high-level mental performance.

The vibroLink units will be designed to operate fully standalone, adhering to the principle that subsystem designs should prioritize simplicity and reliability. Keeping the units independent avoids the complexity of integration with other systems.

Hearing and vision are distal senses – we perceive objects that are located away from the body. According to Katz, touch is different in that it involves both distal and proximal aspects [7]. For example, when we feel the rumbling of a machine, we perceive something that originates at a distance. But unlike hearing and vision, touch also has a proximal aspect: when we touch a material, we perceive the stimulus directly on the skin, at the point of contact.

The extreme conditions of space significantly limit direct physical interaction, restricting astronauts’ ability to perceive their environment, be it distally or proximally. To address this challenge, researchers have been exploring the development of haptic feedback systems. These systems aim to enhance interactions by providing tactile sensations. Their goal is to bridge the sensory gap created by the harsh extraterrestrial environment and the limitations of current spacesuit technology.

There is a large body of research on improving textiles for space exploration (e.g., [3]), which includes space suits with integrated tactile feedback [11]. The suit proposed by Wicaksono uses various sensors, such as piezoelectric and conductive fabrics, to detect external tactile cues. It then relays this information to the astronaut’s skin through vibration motors, creating dynamic tactile experiences that correspond to the materials outside the suit [11]. Similarly, ExoSkin is a proposed haptic layer for the space suits’ gloves. This layer would allow haptic cues from the external environment to be transferred to the astronaut’s skin using small free-moving pins. These pins adapt their shape based on surface contact, providing haptic feedback to the fingertips [13].

Existing systems are aimed at augmenting proximal tactile perception. Our approach aims to enhance sensory access to remote locations. Placing a patch on a solar panel, provides an EVA pilot with a distal experience of the vibration conditions at that panel.

In addition to the system aiming to augment a different type of experience, existing systems also have the drawback of requiring complex integration with future space suits. Our vibroLink concept, however, is designed to seamlessly augment existing EVA equipment, without requiring complex technological integration.

The astronaut leaves the space station through the airlock and carefully maneuvers along the exterior using handrails for locomotion and security. Upon reaching the solar panel area, they attach their tether for safety. The astronaut performs a visual inspection to look for any visible damage. They check the joints and electrical connections, making adjustments or repairs as needed.

Here the astronaut might attach a transmitter unit to the base of the tether, so that they are aware of any mechanical problems with the tether.

Two astronauts exit the spacecraft, carrying satellite components and required tools. They move toward the assembly location – first using tethers and handrails, then with astronaut #1 operating a robotic arm to position astronaut two correctly. Astronaut #2 begins by aligning the satellite’s base with its mounting structure and securing it with bolts or clamps. One by one, they attach additional components such as antennas or sensors, while astronaut #1 adjusts their position relative to the satellite using the robotic arm. After each connection is checked for proper fit and stability, the astronaut powers up or tests parts of the satellite.

Here, astronaut #1 might request astronaut #2 to place a transmitter unit on the satellite itself, allowing astronaut #2 – equipped with a receiver unit – to gain better sensory access to the ongoing assembly process. Additionally, astronaut #2 may place a transmitter unit on the robotic arm’s motors. Since the arm is frequently used to change position, this setup helps them distinguish whether relative motion between themselves and the equipment is caused by drift or by the arm’s movement.

The astronaut exits the planetary lander and steps onto the moon’s surface. Moving slowly and carefully, they walk toward a designated location for sample collection. Upon arrival, they unpack a probe tool from their equipment, insert it into the ground, and collect a soil sample. Once the task is complete, the sample is secured in a storage container.

In this scenario, the astronaut might attach a transmitter unit to a piece of machinery inside the lunar lander. The purpose of vibroLink here is not strictly utilitarian. In the harsh and unfamiliar environment, the familiar vibration pattern from the lander’s machinery provides a sense of comfort and orientation. It offers the astronaut a subtle but reassuring cue that their way back home is secure, even if the lander is temporarily out of sight, and supports their emotional wellbeing.

Participants were tasked with identifying the number of knocks perceived through the vibroactuator’s feedback. Experimenter #2 knocked on the piezo sensor using a rigid plastic piece in a separate room while participants felt the vibratory feedback and identified the number of knocks. Each participant completed one trial, which consisted of four stimuli (1, 2, 3, or 4 knocks) presented in a randomized order.

Participants correctly identified the number of knocks with an overall accuracy of 95.83%. Five out of six participants achieved 100.0% accuracy, while one participant made one error.

Participants were asked to identify both the material and the action conveyed through the tactile feedback. The experiment used two materials (soft and hard) and two actions (scratching or knocking the piezoelectric sensor), resulting in four distinct pairs of stimuli: (soft, knocking), (soft, scratching), (hard, knocking), and (hard, scratching). Experimenter #2 performed the stimuli using a rigid object from Study #1 as the hard material and a piece of sponge as the soft material. Each participant completed one trial in which the four pairs of stimuli were presented in a randomized order. Before the experiment, participants were familiarized with the tactile feedback of all four combinations once.

Results showed an overall accuracy of 87.50% in identifying the stimuli. Four participants achieved 100% accuracy, while P1 misidentified a material, and separately P2 misidentified a material and an action.

Current EVA operations rely heavily on visual information. The bulkiness of EVA suits and the vacuum of space shield astronauts from the vibrations of their surroundings. However, these vibrations are important to our tacit understanding of materiality and actions. vibroLink addresses this problem by offering an implicit, continuous information stream that can operate in parallel with visual tasks. Our preliminary evaluations indicate that such a link can indeed be used to transmit tacit information. Untrained participants were not only able to decode explicit tactile signals such as the number of knocks, but also to differentiate between materials and actions through vibration alone. This suggests that the information provided by vibroLink can effectively support a better understanding of one’s environment during EVA activity.

A system such as vibroLink likely has other benefits related to EVA operations. A central issue during EVA is sensory deprivation due to the isolation provided by the space suit, which can degrade cognitive performance and increase the risk of errors. Our system may mitigate such cognitive effects by increasing sensory access to the astronaut’s environment.

A common concern identified in the literature is the potential complexity of integrating haptic feedback systems into existing suits – generally, added functionality is seen as something that may compromise the safety and reliability of equipment. Many proposed solutions require extensive integration with existing technology stacks. We avoid this issue by proposing that vibroLink operate independently, requiring no integration with existing subsystems. Furthermore, the components are deployable ad hoc and can be integrated into deployment procedures and best practices. This simplicity directly responds to the requirement that EVA tools prioritize reliability and ease of use.

Despite its promise, our prototype still faces technical limitations. The piezo sensor in the transmitter lacks sensitivity to low-frequency vibrations, which we have found important for detecting subtle mechanical anomalies. This limits the system’s applicability for more complex diagnostic tasks. We propose combining the piezo sensor with an accelerometer to expand the frequency range, though this introduces new challenges in signal fusion and actuation algorithms that will need to be addressed.

Additionally, testing with expert users and under more realistic conditions is necessary to validate the system’s relevance in situ. Open questions include whether vibroLink requires any form of longitudinal training for astronauts to fully benefit from it, and whether there are conditions under which the information it provides could be perceived as distracting rather than helpful. Another consideration is whether the current one-to-one transmitter–receiver pairing should be maintained – with all its benefits for creative deployment – or upgraded to a multi-sensor system connected to a single receiver, which may be less flexible but better suited for certain tasks.

In sum, vibroLink offers a lightweight, flexible, and cognitively compatible solution to well-documented EVA limitations. By reintroducing tactile cues through a standalone, easily deployable system, vibroLink addresses both technical and cognitive challenges identified in prior work, and opens a path toward more embodied interaction in extreme environments.