Robots have intrigued humans and captured our imaginations for centuries. As early as the 8th century B.C., Homer, in his epic poem Illiad, described "handmaids of god resembling living young damsels." Science fiction literature and motion pictures also have pictured mobile devices, human-like in form, encased in metal, and able to do those everyday tasks from which many of us would like to be freed.

Despite our long fascination with robots, the first U.S. patent for an industrial robot was issued less than 40 years ago to George C. Devol.. In 1958, Joseph F. Engelberger, a science-fiction enthusiast, developed the first programmable manipulator, or robot. Since then, robots have become indispensable to the industry, to medicine, and to the United States space program. And while today's robots may not look or perform as fantastically as those featured in literature or movies, they are the fulfillment of dozens of science fiction visions.

Robots: What and Why

A robot may be define as a self-controlled device consisting of electronic, electrical, or mechanical units. More generally, it is a machine that functions in place of a living agent. Robots are especially desirable for certain work functions because, unlike humans, they never get tired; they can endure physical conditions that are uncomfortable or even dangerous; they can operate in airless conditions; they do not get bored by repetition; and they cannot be distracted from the task at hand.

Thus, robots are especially valuable to space exploration. Not only can they travel to environments too hostile or too distant for human explorers, but they can also enhance the work schedule of a manned space mission.

Types of Robots in Space

Today, two types of devices exist which can be considered space robots. One is the ROV (Remotely Operated Vehicle) and the other is the RMS (Remote Manipulator System).

Typically, ROVs are used in nuclear facilities for inspection and repair in areas too dangerous for humans, and by police bomb squads for removal of potentially hazardous materials. Space researchers are especially interested in this type of robot for terrain exploration in space.

An ROV can be an unmanned spacecraft that remains in flight, a lander that makes contact with an extraterrestrial body and operates from a stationary position, or a rover that can move over terrain once it has landed. It is difficult to say exactly when early spacecraft evolved from simple automatons to robot explorers or ROVs. Even the earliest and simplest spacecraft operated with some preprogrammed functions monitored closely from Earth.

The most common type of existing robotic device is the crane-like RMS (Remote Manipulator System), or robot arm, most often used in industry and manufacturing. This mechanical arm recreates many of the movements of the human arm, having not only side-to-side and up-and-down motion, but also a full 360-degree circular motion at the wrist, which humans do not have. Robot arms are of two types. One is computer-operated and programmed for a specific function. The other requires a human to actually control the strength and movement of the arm to perform the task. To date, a robot arm has performed a number of tasks on several NASA space missions-serving as a grappler, a remote assembly device, and also as a positioning and anchoring device for astronauts working in space.

Robots and Unmanned Space Exploration

Robotic spacecraft are especially useful in space exploration where distances are too long and environments too hostile and dangerous to send humans. Before astronauts were sent to the Moon, a series of Surveyor spacecraft soft-landed on the lunar surface between 1966 and 1968. Triggered by electronic signals from Earthbound humans, four Surveyors transmitted thousands of images back to Earth and analyzed solid samples gathered with an extendible claw. Based on this information, the United States was able to plan its manned Apollo Moon missions.

The Soviet Lunokhod 1 lunar rover can be called the first mobile robot to explore an extraterrestrial body. In 1970 it rolled out onto the Moon's surface from the Luna 17 spacecraft and was remotely controlled by Soviet scientists through television viewers. One of its autonomous functions was the ability to sense when it was going to tip over and automatically stop and wait for signal from Earth to help it proceed.

Two Viking spacecraft, launched in 1975, parachuted landers to the Martian surface with television cameras, soil scoops and analyzers, and weather stations. Some of these devices transmitted valuable information to Earth until 1982. If humans are ever to explore or even inhabit Mars, additional robotic probes similar to these are essential.

An exciting and practical use for ROVs is as unmanned deep space probes. The Voyager 2 proves are excellent examples of how unmanned space missions can greatly increase our understanding of the universe. They are programmed automatically to make adjustments in operations far from direct human interaction. The Voyager missions, launched in 1977, have provided scientists with opportunities to view Jupiter, Saturn, Uranus, and Neptune, and they continue to provide thought-provoking new data. They have already traveled over 2.8 billion miles, and if they continue to operate, the Voyager proves will hurtle on past the edge of the solar system to interstellar space, sending back signals that are still unfeasible for a manned mission to gather at this point in our space development.

Robots and Manned Space Exploration

To date, the Space Shuttle's Remote Manipulator System (RMS) is the only robotic device which has been used on manned space missions. The robot arm made its test debut in space aboard the Space Shuttle Columbia Mission STS-2 in 1981. Then in 1983, on Space Shuttle Challenger Mission STS-7, when Sally Ride made her historic flight as the first American woman in space, the robot arm was used to release and recover a pallet satellite.

Space Shuttle Mission STS-41C, a 1984 Challenger flight, illustrates some of the advantages of using remote manipulators in space. One of the mission's goals was to capture the malfunctioning Solar Maximum Mission Satellite (Solar Max) for repair and re-orbit. During an extravehicular activity (EVA), astronaut George D. Nelson was unsuccessful in trying to grab the satellite by hand in an untethered space walk, but later, Nelson and astronaut James van Hoften used the Shuttle's giant robot arm to grapple the satellite; then they repaired it in the Shuttle's giant robot arm to grapple the satellite; then they repaired it in the Shuttle's payload bay. Once the repair was successfully completed, the RMS was used to redeploy the satellite.

On the same Challenger mission, human intervention was required to help the robot arm deploy the largest payload yet handled by a Shuttle. The Long Duration Exposure Facility (LDEF) weighing 21,300 pounds (9700 kilograms) was so large it blocked the vision of Astronaut Terry Hart who was manipulating the robot arm. Using a remote TV monitor for visual feedback, Hart first used the RMS to latch onto a grapple fixture on the LDEF to activate its power sources, and then used the RMS to lift, steady, and release the LDEF into orbit. The LDEF contained 57 experiments and was the first satellite specifically designed to be returned to Earth; so, in 1990, the RMS was again used to grapple the satellite and lower it into the Shuttle's payload bay for the return trip to Earth.

A second satellite retrieval mission was accomplished in 1984 during Space Shuttle Discovery Mission STS-51A. This time, a manual retrieval and berthing procedure was accomplished by an astronaut positioned in a restraint system located at the end of the RMS. This foot restraint device, which functions like a "cherry picker," holds and positions the astronaut operated the robot arm from inside the Shuttle's cabin.

On Space Shuttle Atlantis Mission STS-61B, launched in 1985, two important construction experiments were conducted using the RMS. These experiments, referred to as EASE and ACCESS, tested space assembly of two different structures consisting of beams and nodes and evaluated the roles EVA might play in building the planned Space Station.

All these examples of using the RMS during manned space missions rely on teleoperation, continuously controlled remote manipulation by a human. (Teleoperation comes from the Greek, telchir, meaning "distant hands.") Although the RMS has an automated mode, it has never been used in an actual recovery operation. This mode, however, was tested on STS-3 in 1982.

Future Robots in Space

NASA's current plans for development of space robots concentrates on three main uses of remote manipulation in space: servicers, cranes, and rovers. Servicers are humansized, multi-arm, remote manipulators which are used for servicing and assembly. Cranes, like the RMS currently operated on Space Shuttle missions, are long single arms used for repositioning larges masses. Rovers are mobile platforms for transporting payloads on planetary servicers and extraterrestrial surfaces.

In its research, NASA's approach is to focus on remote manipulation systems which demonstrate robustness, or the ability to cope with problems; versatility, or the ability to do a variety of tasks; and simplicity, offering the operator a sophisticated system in a package that reduces complexity - much in the same way a powerful software package allows a nonexpert to manipulate the capabilities of a computer. The strategy is to develop remote manipulation technology where humans and machines have both redundant and complementary roles.

Today's space robots operate either by teleoperation (continuous remote control of a manipulator) or robotics (preprogrammed control of a manipulator). Both areš? ? :ly controlled by humans. The distinction is that the teleoperators are controlled by humans remote in distance, and robots are controlled by humans in time (by way of computer programs). NASA's goal is to develop a system of telerobotics where teleoperation and robots are combined. The future of robots in space is not a question of human versus machine, but rather a combination of the best capabilities of human and machine to achieve something which surpasses the capabilities of either alone. Robots using Artificial Intelligence (AI) along with computers will eventually be capable of "learning" how to perform complex tasks.

A number of telerobotic devices are currently under development. The Goddard Space Flight Center in Maryland is the lead NASA center for developing robots like the Flight Telerobotic Servicer which will assemble and service the Space Station. Similar projects are under way at the Johnson Space Center in Texas and the Kennedy Space Center in Florida in support of crew activities and ground processing of STS. These devices will fetch tools and astronauts, perform hazardous launch duties, and even tend crops in orbiting gardens. Planetary rovers and walkers also are being designed both with wheels and leg-like appendages. They will have the technology to safely and autonomously transverse long distances on unfamiliar terrain.

On May 24, 1989, President George Bush spoke on America's space agenda for the 21st century. "I want to reaffirm my support for the quest to create a spacefaring civilization. That objective is not just our ambition, but our destiny..."NASA's work with robotics is sure to play and important role in that destiny.

For the Classroom

1. Have students research how robot arms and robotic spacecraft have assisted the United States space program through specific missions in space. Then assign one or more of the following activities:

* Create a picture storybook that illustrates the use of robots and robotics in space. Share it with younger students. * Create a data base of each of the space missions, including name, mission number, date, duration, crew members (if applicable), and robotic achievements. * Write a short report on the topic. * Prepare a bulletin board to share the information with others in your school

2. In 1920, Czechoslovakian writer Karel Capek invented the word "robot" in his play R.U.R. (Rossum's Universal Robots). Robota, a Czech word, translates as forced labor, serf, slave, or drudgery. Find a copy of the play, and have students dramatize an excerpt from the script. Capek's robots eventually rebelled against their human masters to take over the world. Have students discuss why this is or is not likely to happen in reality.

3. Have a team of students create a mural that illustrates past and future accomplishment so robots in space.

4. Ask a team of students to create a diorama recreating the activity of the robot arm on on specific Space Shuttle mission.

5. Ask students to imagine that robot arms are readily available to consumers. Have students discuss or write about practical applications, describing specific task that could be accomplished more efficiently.

6. One of the biggest challenges in the field of robotics is reproducing the human senses of sight, sound, and touch in order to give robots practical mobility. William Whittaker, director of the Field Robotics laboratory at Pittsburgh's Carnegie Mellon University, is currently working on one of the most promising mobile robots, the Ambler (short for Autonomous Mobile Robot). Ask students to find out more about this project and then discuss its applications for the future of both space exploration and daily life.

7. Have students investigate all the ways robots and robotics will be essential to the construction, operation, and maintenance of the Space Station. Create a poster that illustrates these findings.

8. Computers are considered the "brains" of robots, and at this point, the exploration of Artificial Intelligence (AI) is the crux of robotics research. Have students find out more about the development of computers and then discuss this statement.

9. Research shows that spending prolonged periods in space places great stress on the human body. Have students research the effects of space on the cardiovascular, circulatory, and skeletal body systems. Then ask them to define Space Adaptation Syndrome (SAS). Lead a discussion on how using robots addresses these issues.

Recommended Reading

Curtis, Anthony R., Space Almanac. Woodsboro, Maryland: Arcsooft Publishers, 1989.

Fiermedal, Grant, "Telepresence," Final Frontier, July-August, 1990, pp. 227-31.

Freiherr, Greg, "Invasion of the Spacebots: NASA is looking for a few good machines." Air & Space, February/March, 1990. pp. 73-81.

Krasnoff, Barbara, Robots: Reel to Real, New York: Arco Publishing. 1982.

Scott, Peter B., The Robotics Revolution: The Complete Guide. New York: Basil Blackwell, 1984.

Storrs, Graham. The Robot Age. New York: The Bookwright Press.. 1985.

Washburn, Mark, "Goodbye, Voyager," Air & Space, December 1989/January 1990, pp. 38-48.


The payload deployment and retrieval system includes the electromechanical arm that maneuvers a payload from the payload bay of the space shuttle orbiter to its deployment position and then releases it. It can also grapple a free-flying payload, maneuver it to the payload bay of the orbiter and berth it in the orbiter. This arm is referred to as the remote manipulator system.

The RMS is installed in the payload bay of the orbiter for those missions requiring it. payloads carried aboard the orbiter for deployment do not require the RMS.

The RMS is capable of deploying or retrieving payloads weighing up to 65,000 pounds. The RMS can also retrieve, repair and deploy satellites; provide a mobile extension ladder for extravehicular activity crew members for work stations or foot restraints; and be used as an inspection aid to allow the flight crew members to view the orbiter's or payload's surfaces through a television camera on the RMS.

The PDRS was built via an international agreement between the National Research Council of Canada and NASA. Spar Aerospace Ltd., a Canadian company, designed, developed, tested and built the RMS. CAE Electronics Ltd. in Montreal provides electronic interfaces, servoamplifiers and power conditioners. Dilworth, Secord, Meagher and Assoc. Ltd. in Toronto is responsible for the RMS end effector. Rockwell International's Space Transportation Systems Division designed, developed, tested and built the systems used to attach the RMS to the payload bay of the orbiter.

The basic RMS configuration consists of a manipulator arm; an RMS display and control panel, including rotational and translational hand controllers at the orbiter aft flight deck flight crew station; and a manipulator controller interface unit that interfaces with the orbiter computer. Normally, only one RMS is installed on the left longeron of the orbiter payload bay. The RMS could be installed on the right side, but the orbiter Ku-band antenna would have to be removed to accommodate the RMS there. Two arms could be installed in the payload bay if the orbiter Ku-band antenna were removed, but only one arm could be operated at a time because only a single software package (computer program) and a single set of display and control panel hardware are provided at the flight deck aft control station. Electrical wiring is in the flight deck aft station for both arms.

One flight crew member operates the RMS from the aft flight deck control station, and a second flight crew member usually assists with television camera operations. This allows the RMS operator to view RMS operations through the aft flight deck payload and overhead windows and through the closed-circuit television monitors at the aft flight deck station.

The RMS arm is 50 feet 3 inches long and 15 inches in diameter and has six degrees of freedom. It weighs 905 pounds, and the total system weighs 994 pounds.

The RMS has six joints that correspond roughly to the joints of the human arm, with shoulder yaw and pitch joints; an elbow pitch joint; and wrist pitch, yaw and roll joints. The end effector is the unit at the end of the wrist that actually grabs, or grapples, the payload. The two lightweight boom segments are called the upper and lower arms. The upper boom connects the shoulder and elbow joints, and the lower boom connects the elbow and wrist joints. The RMS arm attaches to the orbiter payload bay longeron at the shoulder manipulator positioning mechanism. Power and data connections are located at the shoulder MPM.

The RMS can operate with standard or special-purpose end effectors. The standard end effector can grapple a payload, keep it rigidly attached as long as required and then release it. Special-purpose end effectors are designed by payload developers and installed instead of the standard end effector during ground turnaround. An optional payload electrical connector can receive electrical power through a connector located in the standard end effector.

The booms are made of graphite epoxy. They are 13 inches in diameter by 17 feet and 20 feet, respectively, in length and are attached by metallic joints. The composite in one arm weighs 93 pounds. The joint and electronic housings are made of aluminum alloy.

A shoulder brace relieves launch loads on the shoulder pitch gear train of the RMS. On orbit, the brace is released to allow RMS operations. It cannot be relatched on orbit, but it is not required that it be relatched for entry or landing loads.

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Last modified: Wednesday, 25-Mar-11 10:07:00 PM CDT

Creator: Jerry Woodfill / NASA, Mail Code ER7, NASA JSC, Houston, TX 77058

A service of the Software, Robotics and Simulation Division, Rob Ambrose, Chief.