Robotics 4 November 2026 5 MIN READ
Shakey, the Robot That Gave Us A*
The wobbly 1960s robot that reasoned about rooms and blocks, and left behind the A* and STRIPS algorithms still used in planning.
THE SHORT ANSWER
Shakey, built at SRI between 1966 and 1972, is described as the first mobile robot that could perceive and reason about its surroundings. It was slow and relied on remote computers, yet it produced the A* path-finding algorithm and the STRIPS planner, both still in use today.
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The first robot that could reason
Between 1966 and 1972, SRI’s Artificial Intelligence Center in California worked on a wobbly wheeled machine that its team named Shakey. SRI describes it as the first mobile robot able to perceive and reason about its surroundings. It could plan a route, find its way between rooms and rearrange simple objects such as blocks. The Computer History Museum says it was not a practical tool, but it led to advances in visual analysis, route finding and object manipulation.
The name came from the way it moved. The project head, Charles Rosen, recalled that the team spent a month looking for a name before settling on Shakey.
The proposal that launched the project went to the funder in January 1965, according to Peter Hart, one of its leaders, and it aimed at an experimental test bed that would join up all the sub-fields of AI. Other accounts date the start differently, so treat the exact start as approximate. Nils Nilsson recalled that the first contract, for about eighteen months, was worth around $300,000. That is a participant’s memory, not a contract document.
A brain in another room
Shakey’s thinking did not happen on board. The museum notes that large remote computers controlled it over a two-way radio link. The robot’s main sensor was a television camera with only 120 lines of resolution, according to the IEEE Milestone dossier.
With senses that weak, the researchers simplified the world instead. Hart recalled that dark baseboards were used to correct the position error that built up as the robot counted the steps of its motors. Shakey lived in a series of rooms with blocks and ramps built to suit it. In 1970 the host computer was upgraded from an SDS 940 to a more powerful DEC PDP-10, while the robot itself got only minor changes.
Two ideas that outlived the robot
STRIPS. To decide what to do, Shakey used a planner called STRIPS, created by Richard Fikes and Nils Nilsson. It combined the means-ends reasoning of Newell and Simon with theorem proving developed by Cordell Green. A STRIPS action is described by its preconditions and by what it deletes and adds to the model of the world. That gave AI a practical answer to what was called the frame problem: how to say what a change leaves unchanged. Hart said in 2017 that STRIPS rules or their derivatives are still used in most modern planners.
A*. To find its way, Shakey needed shortest paths. Hart, Nilsson and Bertram Raphael developed A* as one of several path-finding algorithms for its navigation. Its selling point is a guarantee: it finds the shortest path while examining the smallest number of alternatives necessary. The 1968 paper in IEEE Transactions on Systems Science and Cybernetics proves exactly that. Hart said that the manuscript was rejected by the most prestigious journals of the day before this one accepted it.
The IEEE dossier says Mars rovers use Field D*, a descendant of A*.
A third legacy is architectural. According to Hart, the second version of the software organised control in layers, the first time this design was used to control a robot. The dossier says layered control influenced later machines such as Stanley, which won the 2005 DARPA Grand Challenge.
It was very slow
Shakey’s fame is out of proportion to its speed. SRI’s own report says it moved very slowly, and Richard Waldinger recalled it as slow and unreliable. Edward Feigenbaum said that its total travel over the whole life of the experiment probably never reached a kilometre. We found no primary figure for its speed or planning time, so treat every number you read elsewhere with caution.
Where it is now
The Computer History Museum in Mountain View, California, catalogues a Shakey, made in 1969, which it lists as on display in its AI and robotics gallery. Its catalogue gives the size as 47 by 69 by 47 inches, including protruding wire sensors. In February 2017 the IEEE dedicated a Milestone for Shakey, with plaques at SRI in Menlo Park and at the museum. The numbering of the Milestone differs between the sources, so we do not quote it.
Bill Gates visited the lab as a high-school junior in 1971, Hart recalled, and thought it was pretty cool.
What to watch next
- Planning in modern robots: where classical planning like STRIPS is combined with learned models.
- Onboard versus remote thinking: today’s robots again lean on the cloud, as Shakey leaned on its radio link.
- Path search: how A* and its descendants, such as Field D*, keep being used to move robots around real terrain.
Our take: the body failed, the ideas won. Shakey was clumsy and slow, and it was still the first full system that could perceive, reason and act. Its robot is in a museum, and its algorithms live on in planning and path search.
Do you agree?
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Sources
- Shakey the Robot · SRI International · Accessed
- Shakey - CHM Revolution · Computer History Museum · Accessed
- Shakey: From Conception to History (Kuipers, Feigenbaum, Hart, Nilsson) · AI Magazine 38(1), AAAI · Accessed
- SRI's Pioneering Mobile Robot Shakey Honored as IEEE Milestone · IEEE Spectrum (Tekla Perry) · Accessed
- SHAKEY the Robot - X279.83 · Computer History Museum (collection catalog) · Accessed
- Milestones: SHAKEY: The World's First Mobile Intelligent Robot, 1972 · Engineering and Technology History Wiki (IEEE) · Accessed
- A Formal Basis for the Heuristic Determination of Minimum Cost Paths (Hart, Nilsson, Raphael) · IEEE Transactions on Systems Science and Cybernetics · Accessed
- Shakey the Robot, SRI Technical Note 323 (ed. N. J. Nilsson; DTIC ADA458918) · SRI International / DTIC (via Internet Archive) · Accessed
- Shakey - A 1960's Predecessor to Today's Advanced Robotics · Nuts & Volts · Accessed
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