Stanford Cart

How a Moon Rover Project was Blocked by a Politician but got Kicked by Football into a Self-Driving Vehicle

By Lester Earnest (les at


View in Portuguese courtesy of Artur Weber & Adelina Domingos


The Stanford Cart has had a career of ups and downs since 1960. It was born as a research platform for studying the problem of controlling a Moon Rover from Earth. It then was reconfigured as an autonomous road vehicle for research in visual navigation, then went into show business for a few years. It now is on display in a home for retired robots at the Computer History Museum .


Moon Rover Test Vehicle

 Stanford Cart with cable, 1961. The Stanford Cart was originally constructed by Mechanical Engineering (ME) graduate student James L. Adams to support his research on the problem of controlling a remote vehicle using video information. He had been working at Caltech’s Jet Propulsion Laboratory on a NASA program called Project Prospector, which was proceeding with the assumption that someone on earth could drive around the Moon using a television camera on a vehicle and radio links in both directions. However, Adams showed that assumption to be false.

     The Cart had four small bicycle wheels with electric motors powered by a car battery and carried a television camera with a fixed view in the forward direction. Tests were conducted using both 2-wheel steering, like a car, and 4-wheel steering, in which the wheels and the television camera swiveled together. The cart was connected by a very long cable to a control console with a television display and controls for steering and speed. A magnetic tape loop made it possible to vary the time delay of steering commands, to simulate communication delays.

     Adams explored the controllability of the vehicle while avoiding obstacles with various combinations of communication delay and speed. When steering commands are delayed by communications there is a tendency for the operator to over-steer and lose control. Adams showed in his dissertation that with a communication delay corresponding to the round trip to the Moon (about 2.5 seconds) the vehicle could not be reliably controlled if traveling faster than about 0.2 mph (0.3 kph) [1].


Stanford Cart with radio links, 1963. Mechanical Engineering graduate student Paul W. Braisted devised a scheme to improve the controllability of the vehicle by adding an analog computer that took into account preceding steering commands and put a bright dot on the television screen at the predicted location of the cart when a current steering command would begin to take effect. With this addition the vehicle could be controlled at 5 mph (8 kph). Still there was a fundamental limitation on teleoperation in that if the travel during the time delay is greater than the distance from the vehicle to an unseen obstacle there is no way to avoid hitting it. Braisted completed his dissertation in 1963 [2].


Political Theater Takes Precedence. The prospect of using this technology was put off by President John F. Kennedy's announcement on September 12, 1962, of the U.S. manned mission to the Moon. Under hindsight, based on scientific objectives, that plan made sense only as political theater but it turned into a television extravaganza. We could have gathered a lot more information about the moon by sending robot vehicles for a tiny fraction of what it cost to send people there and get them back, but politics generally takes precedence over science.  Had we stuck with the original plan of sending robotic vehicles instead of people, we would now know a lot more about the Moon and would have spent only a tiny fraction of what it cost to put on that television show. Incidentally, I evidently played a small part in providing good television quality for that show but that is another story.

     People tend to think of astronauts and cosmonauts as explorers but, since none of their missions made sense from a scientific exploration viewpoint, they were actually actors in political theater. Robots are much better at space travel and planetary exploration than humans and likely always will be. After the Moon landings our politicians put together the Internationals Space Station and Space Shuttle costing hundreds of billion dollars more for no significant purpose other than political show business.


How football kicked off the first attempt at an autonomous road vehicle. I came to Stanford in late 1965 as Executive Officer of the new Stanford Artificial Intelligence Laboratory (SAIL), which I designed, named, and managed in the foothills above the Stanford campus

     Jim Adams, who had originally created the Cart for his PhD dissertation, had returned to Stanford as a Professor of Mechanical Engineering and, given that he and I had been football teammates as Caltech undergraduates in the early 1950s, I looked him up, visited his lab and noticed the Cart sitting in the corner of the room, then asked about it. It occurred to me that this vehicle could be used to build an experimental self-driving road vehicle based on computer interpretation of the visual input, so I asked if I could borrow it and was granted that privilege.


../Documents/My%20Pictures/SAIL/sail.79.jpgSAIL research facility, 1966-1979. I had in mind trying to drive on the circular road surrounding the SAIL facility using the road center line and other visual references. However I knew that the Cart would be unable to carry a big enough computer to do that, so I planned to use a television transmitter on the cart to send images to the SAIL computer (which by that time was a DEC KA10 system occupying an area about the size of a basketball half-court), with another radio link used to send guidance commands from the computer to the Cart. The KA10 ran at a speed of about 0.65 MIPS, quite slow by modern standards.

     However, the radio links that had been used in the earlier experiments with the Cart had disappeared, so I recruited an Electrical Engineering PhD student named Rodney Schmidt, to build a low power TV transmitter and radio control link, allowing human operators to control the cart via the computer while sitting at a desk viewing the television image.


Stanford Cart configured as an autonomous road vehicle. We were granted an experimental TV license by the Federal Communications Commission for Channels 22 and 23, so that we could be sloppy. I had a long ramp built down the front steps that allowed the Cart to travel from the lab to the road, making it possible to drive it around the neighborhood, which became a popular pastime.

     I also had a metal “CAUTION ROBOT VEHICLE” sign posted on the entrance road to the lab, which turned out to be a problem because it was repeatedly stolen and was expensive to replicate. I figured out too late that it should have been printed on cardboard and offered for sale at the Stanford Book Store, which could have made some money.

     To facilitate letting the cart travel from the lab to the street and back, I got a series of ramps built on the front steps, which turned out to be useful for other purposes, such as enabling cyclists such as me to ride to our offices and it also enabled people in wheelchairs to get in for tours.

../Documents/My%20Pictures/SAIL/caution.jpg     Once the system was working, John McCarthy became interested and took control of the project so that he could play with it, to my extreme annoyance. Worse still, he then backed away from the self-driving vehicle goal and settled for looking at a high contrast line on paper. Rodney Schmidt wrote a thesis saying that under controlled lighting conditions such a line could be followed at a speed of about 0.8 mph (1.3 kph), an experiment that didn't even require a vehicle [3].


Stanford Cart with slider, 1972-79. The cart was next changed from 4-wheel to 2-wheel steering and a number of people played with it. Graduate student Bruce Baumgart started driving the Cart around and was thinking of turning it into a dissertation but eventually did one on Geomed, a 3D geometric editor for representing polyhedra.

     Hans Moravec, who had come to Stanford specifically to work on visual navigation, stayed with it but suffered a setback in October 1973 when the cart toppled off the exit ramp while under manual control and ended up with battery acid throughout its electronics. Moravec was able to enlist the aid of roboticist Victor Scheinman in 1977 to build a “slider,” a mechanical swivel that moved the television camera from side to side allowing multiple views to be obtained without moving the cart. Using the KL10 processor then available, which ran at about 2.5 MIPS, Moravec was eventually able to use multi-ocular vision to navigate slowly around obstacles in an indoor environment. He used it to do navigation problems that were similar to what was being done in the artificial intelligence group at the nearby SRI (Stanford Research Institute) and programmed it to move in one meter spurts punctuated by ten to fifteen minute pauses for image processing and route planning. In 1979, the cart successfully crossed a chair-filled room without human intervention in about five hours.  Moravec completed his dissertation in 1980 and there is a short video of the cart in action. Upon completion of his PhD, Moravec moved to Carnegie Mellon University’s Robotics Institute which had been founded earlier by Prof. Raj Reddy, another SAIL graduate.


More Show Business. After SAIL shut down in 1980 the cart again went into storage until 1987 when, at the request of the Digital Computer Museum in Boston, I sent a number of retired robotic devices to a new exhibit there. The Smart Machines Theater, later renamed Robot Theater, was a collection of artifacts on stage, lit up in sequence with some moving in their moments of glory, synched to a video, proving that even old robots can have a second career in show business.

The Smart Machines Theater in Boston with the Cart in the center

After the Boston museum shut down, the robots and other artifacts were sent to its successor, the Computer History Museum in Mountain View, California. Beginning in 2011 it was put on static display at the Museum, where it can be seen today. However, the captions shown there tell almost nothing about its history. Perhaps someday it will again be allowed to roam the world.


CMU Research. The Robotics Lab at Carnegie-Mellon University, managed by former SAILors Raj Reddy and Hans Moravec undertook many research projects, including additional attempts at building self-driving vehicles, training many PhDs in the process.


Back to Stanford. In 2003 Sebastian Thrun, who had earned a PhD in the CMU Robotics Lab, joined the Stanford faculty and revived SAIL, then initiated a new autonomous road vehicle project. He initially developed a robot car called Stanley that eventually won the 2005 DARPA Grand Challenge, a race across the California desert. In 2007 the SAIL team took second in the DARPA Urban Challenge, which simulated an urban driving environment.




On to Google. Sebastian Thrun and some of his colleagues then moved to nearby Google and created the Google driverless car which was then spun off into a new company called Waymo, which is still part of the Googleplex, now called Alphabet, and is still under development there. Uber allegedly tried to swipe some of their technology, so Waymo sued them and got an out of court settlement.

     Meanwhile, Sebasian Thrun started a new company called Udacity, which offers online education in a number of areas.





Waymo Self-Driving Car


More Space Theater. Another person who has entered space showbiz is Elon Musk, who earlier made a bundle as a cofounder of Paypal, then founded SpaceX in 2002. Musk and others are now planning to send people back to the moon and on to Mars, which will be equally pointless. Getting to Mars requires a trip of around nine months, subject to both cosmic and solar radiation, so there is a good chance they will get sick or die on the way. Thus a digging robot should be sent along to bury them. If they do get there alive then radiation will kill them shortly.

     Another group subsequently founded Tesla and developed an electric car but ran out of money. Musk then bailed them out and pretended that he had invented that car, further boosting his show business. He recently used SpaceX rockets to put a Tesla into space, orbiting around the Sun, which made more headlines but not a lot of sense.


Heritage. Looking back, The first version of the Stanford Cart, built to assess the feasability of remotely driving a vehicle on the Moon, was succeeded by a modified version of the Cart that worked, then was transformed into an experimental self-driving vehicle on Earth, then was modified to run around indoors. Moravec then went on to CMU and, with Raj Reddy, helped initiate more self-driving vehicle research there, at least a couple of generations.

     Then Thrun came from CMU to Stanford and reinitiated a successful self-driving vehicle development there, then went on to Google and did a couple more generations there. That technology then moved into Waymo for another generation. In summary, the Waymo vehicle can be thought of as something like a tenth to twelfth generation descendant of the original Stanford Cart and things are clearly going to keep moving ahead. My hope is that robot taxi services will become widespread before I lose my drivers license.


Acknowledgment. Thanks to James Adams, Bruce Baumgart, Hans Moravec, Oliver Strimpel, Sebastian Thrun and Dave Grossman for providing information for this account.


References. The following Ph.D. dissertations at Stanford University came out of research with the Stanford Cart.

[1] James Adams, Remote control with long transmission delays, PhD in Mechanical Engineering, 1961.

[2] Paul Braisted, Study of a predictor for remote control systems operating with signal transmission delays, PhD in Mechanical Engineering, 1963.

[3] Rodney Schmidt, A study of the real-time control of a computer-driven vehicle, PhD in Electrical Engineering, 1971.

[4] Hans Moravec, Obstacle avoidance and navigation in the real world by a seeing robot rover, PhD in Computer Science, 1980.