Human Factors

Human factors engineering, a term that is often used synonymously with the word "ergonomics," is the science and design activity that deals with improving how people interact with their environments, tools, and tasks as part of a system; the objective is to make these interactions safe, productive, and comfortable. Or, perhaps better stated from an engineering perspective, human factors engineering is the science and art of designing the environment, tools, and tasks so they interact well with humans as part of a system.

This discipline is difficult to implement in workplaces and homes on Earth. Many problems are technically complicated, as issues of money and scheduling are usually constraints, and the traditionally successful ways of getting things done make the politics of improvement and innovation complex. Allocating tasks along the continuum from manual to machine; taking into account all of the capabilities and the limitations of people (as individuals or teams) and machines; accounting for the dimensions of power, tools, feedback, control, automation, memory, computation, analysis, decision making, and artificial intelligence; and bringing together the sciences and practices of engineering, psychology, biology, communications, and economics are issues that human factors engineers deal with every day.

Stepping off the home planet to the reduced gravity and relative hostility of space adds considerably to the problems addressed by space human factors engineers, but the discipline is the same. The environment in space is different in regard to factors that go beyond the effects of gravity (no ground reactive support; the need to wear protective yet cumbersome suits); the human body adapts to these changes in different ways over time, and the work that must be done is often specific to space in terms of what has to be done or how it can be done.

Meeting the Challenges of the Space Environment

Microgravity has a direct and immediate effect on the human body. Each cell reacts individually to microgravity, and the body as a whole immediately undergoes changes in chemistry and dimensions. Fluids shift to the upper body, and compression no longer acts on the spine and the soles of the feet. Calcium is lost from the bones, and muscles atrophy from lack of use, resulting in diminished strength. A human arm floats up rather than hanging down by the hip. The design of workstations and computers must take into account these differences in stature, posture, biomechanics, and strength. For example, gravity will not keep a computer mouse on the table-top, and so a different tool must be used to move the cursor. A touch screen was studied, but it was very difficult for a person in space to hold the arm out and maintain contact with the screen without pushing oneself away. Voice control of the computer holds promise, but crewmembers want something much more reliable on the machine side and much more forgiving of human error. The current compromise is a trackball-type device or a joystick. But what if the crewmember floats over to the workstation upside down? How should displays and controls be designed so that procedures are not performed backward?

In orbit, feet are nearly useless appendages after an initial kickoff and moving around is controlled mostly by using handrails. Pushing on a toggle switch is more likely to result in rotating the operator's human body than in repositioning the switch unless the operator is restrained. Mobility aids and force restraints are essential in reducing bruises among people moving and stopping in space. In partial gravity environments, such as on Mars or lunar surfaces, moving from one place to another is very different from the same activities on Earth. Video sequences of humans on the Moon show that they sort of bounce around. Studies in simulated Mars gravity conducted in parabolic flights of National Aeronautics and Space Administration (NASA) research airplanes have demonstrated that a different way of moving comes naturally to the human explorer. Space suits and tools will have to be designed to take into account the way human behavior changes in space.

Natural convection currents do not act without a gravity field, and so hot air does not rise. If an astronaut wants to breathe fresh oxygen in every breath, there have to be fans to circulate the air. The heat from an electrical component such as a laptop does not move away with the air, and so energy must be used for active cooling of every item that dissipates heat, including the human.

Working in a pressurized space suit is difficult, especially for the hands. Controlling telerobots or programming automated machines leaves little room for error, takes a lot of time, and requires special skills. The confined cabin of a spacecraft limits the range and exercise of human senses and perceptions. The isolation from colleagues, family, and friends can alter social relationships, expectations, and support structures. The hostility of the external space environment and the inherent risk of spaceflight add stress to everyday tasks. A mistake or inattention can quickly result in death or mission failure and consequently everything becomes much more important.

The nature of space combined with the new human-designed environments and tools for living and working in space impact the ways in which people do things. Solving cognitive problems; meeting unexpected challenges; maintaining safety; staying attentive and motivated on long, boring flights from planet to planet; and maintaining teamwork, family ties, and a healthy personality are all aspects of the interaction between a human and the designed environment.

SEE ALSO COMMUNITIES IN SPACE (VOLUME 4); INTERNATIONAL SPACE STATION (VOLUMES 1 AND 3); LIVING IN SPACE (VOLUME 3); LIVING ON OTHER WORLDS (VOLUME 3).

Theodore T. Foley II and Sudhakar Rajulu

Bibliography

National Aeronautics and Space Administration. Man-Systems Integration Standards, NASA STD-3000, Revision B. Houston: Johnson Space Center, 1995.

Salvendy, Gavriel, ed. Handbook of Human Factors. New York: Wiley, 1987.

——. Handbook of Human Factors and Ergonomics, 2d ed. New York: Wiley, 1997.