Humans versus Robots

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Humans versus Robots

As humans step off their home planet into the surrounding solar system and beyond, they do not go alone. Machines have preceded them. And as people go into space, machines will go along. Of all the machines we have used and imagined, none have captured our interest and feelings so strongly as the class of machines called robots.

But what exactly is meant by the term "robot"? Moreover, how is it decided that it is better to use a robot for a job rather than a human? What are robots like in the early twenty-first century and what they will be like in the future? Will humans ever become more robot-like?

What are Robots?

Let's begin with a bit of speculation on why robots are so interesting to us. Humans have always tried to create "life" from inanimate objects. From literary history, there have been robot-like figures such as Pinocchio and Frankenstein, and from more recent popular culture we have Star Trek 's Data and the Terminator. These entities could be good or evil, and were deliberately created in our image.

Fictional robots are often capable of moving around the world and having other characteristics of humans. In their depiction, there is frequently some essence that transcends their physical trapping and they may be capable of thinking, feeling, judging, and exploring. It is easy to imagine R2D2 and C3PO, robots from George Lucas's popular movie Star Wars (1977), as companionseven friends. These machines of fiction give robotic researchers goals to build toward. Unfortunately, humans in 2002 do not yet have the capability of creating any of these imagined robots.

Nevertheless, we have created machines for space exploration that we do call robots. Examples include the Sojourner robot from the 1997 Mars Pathfinder mission and the robotic arms from the space shuttle and the International Space Station. It is possible to coax these machines to do marvelous tasks in space and on planetary surfaces, although in most ways these devices are much closer to a car than they are to the robots of science fiction.

Space missions are expensive and require a great deal of planning and long, careful preparation. Hence, the technologies flown on missions are often several years behind the state of the art for terrestrial applications. One of the consequences of this is that we can simply look at the technology that is available for use in Earth applications (e.g., autonomy used in vehicles in agriculture) and realize that the technologies behind these applications will be available in a decade or so in space missions.

What is a Space Robot?

Given that modern space robots have a closer relationship to appliances than they do to the robotics stars of Hollywood, it is not easy to clearly define what is a robot and what is not. Generally for space applications, robots are machines that have some level of autonomy, can follow instructions, and are capable of interacting with their environment. Robots will usually have either arms or some means of mobility, like wheels. We would think of a robot as having more autonomy if by using that robot, humans can do more of what they want to do, and less of what they do not want to do.

To do a task in space we have both humans and robots as possible agents for that action. But when should we use robots and when should we use humans? There are three criteria that are considered in deciding on humans versus robotic tools:

  1. What activities are humans best at? What activities are robots best at?
  2. What are the costs of using humans versus using robots?
  3. What activities do we want humans to be a part of in space?

The Utility of Humans and Robots

Obviously, humans and robots should be used where and when each are most useful. As technologies for robots improve the number of those tasks that robots are better at will increase.

Currently robots are better than humans at a number of things. Machines can perceive beyond the human visual spectrum, they need a smaller mass of consumables (e.g., food), they are more expendable, and they can be built to better tolerate environmental extremes (e.g., cold and radiation).

On the other hand, humans also have a great many advantages for tasks in space. Humans are the most adaptive, creative, and smartest tool for doing science and exploration that we have available. Humans would be the core of every scientific and exploration task we attempt except for the costs and the dangers. In spite of quickly advancing robotics technology, the overwhelming value of humans as tools for space exploration is not likely to change drastically in the foreseeable future. However, costs and dangers are real considerations, and are often sufficient to preclude humans from being the tool of choice unless there are other overriding reasons for the use of humans.

Humans have major advantages over machines in many areas, including mobility, manipulation skills, pattern recognition (e.g., geological evaluation of a site), robustness with respect to plan failures and system failures, self repair under broad parameters, capability to repair a multitude of other tools, and robustness in communication, to name a few. Tests indicate that a human scientist in the field is at least a couple of orders of magnitude more efficient than a rover in space supported by a remote human team.

It is important to note that when humans are used in the exploration of space, machines tools are sent as well. So for a realistic understanding of the advantages of humans in exploration and in science in space it is useful to compare humans with robots as tools.

Relative Costs of Robotic versus Human Missions

Humans are wonderful tools, but they are also expensive tools. Generally, the more mass we launch into space the more costly a mission. Human missions require more mass than robotic missions because we must carry our food, water, and environmental support systems. Unlike machines, humans cannot be put into sleep states for weeks or months to decrease consumable use. For most operations humans want to remain in an environment warm enough for only needing shirtsleeves. Also it is usually necessary to have airlocks and space suits for astronaut egresses. Egress is the word we use for astronauts leaving a spacecraft and going outside. All of these elements add mass, and consequently, cost. Costs are also added because the safety standards for human crews are higher than for robotic devices.

In summary, for most tasks humans are preferable to robots, but they are much more expensive than robots. Another factor that affects the decision to use humans in space exploration is the societal importance of human exploration. We do not only explore space because of the scientific value of that exploration; we also explore space because human beings are curious and like to explore. We have the same motivation to explore Mars and the Moon as we have to climb Mount Everest or reach the bottom of the sea.

Human Exploration

The exploration of space is not the activity of an individual but a cooperative effort by many elements of society. It gives back to that society a sense of accomplishment, international prestige, a sharing of the excitement of exploration and new frontiers, a set of goals for future generations, advances in technologies, and the economic benefits of commercial uses of new technologies. To a lesser degree this is true of all space exploration, but it is most prominent when humans are involved. Space exploration in the early twenty-first century requires the commitment and resources of a government and the political considerations and agreements that this entails. Thus the decision to use humans is often dominated by societal issues. One motivation for society deciding to explore space with humans is simply the excitement we all share for that exploration.

Synergistic Robotic-Human Exploration

Once it is decided to use humans in a particular exploration task, the next question is how machines, including robots, are used to make tasks easier, safer, more effective, and cheaper. Each specific exploration goal leads to different answers to this question. For example, if we are robotically setting up a Mars or lunar base prior to human arrival, then the specifics of what robots and how they are used depends crucially on the details of those habitats.

The robotic augmentation of humans is a recurring theme in science fiction. For example, astronauts donning an exoskeleton suit to augment their strength, as the character Ellen Ripley did in the movie Aliens, is a non-invasive human augmentation that will probably be available in space missions in the not too distant future.

As we explore our solar system we will first send our robotic machines and then explore ourselves. And as we go about exploring space ourselves it will always be in a partnership with robots. The goal is to use robots to make space exploration easier, safer, more effective, and cheaper. The answer to the question of whether to send robots or humans is "both" and each at their proper time.

see also History of Humans in Space (volume 3); Living in Space (volume 3); Robotic Exploration of Space (volume 2); Robotics Technology (volume 2).

Michael A. Sims


Asimov, Isaac, and Karen A. Frenkel. Robots: Machines in Man's Image. New York: Harmony Books, 1985.

Moravec, Hans. Robot: Mere Machine to Transcendent Mind. New York: Oxford University Press, 1999.

Internet Resources

Aerobot. National Aeronautics and Space Administration. <>.

Robonaut. National Aeronautics and Space Administration. <>.

2003 Mars Mission. National Aeronautics and Space Administration. <>.

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Humans versus Robots

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