Man, Mongoose, and Machine

Standing outside a Sri Lankan army base in the spring of 2007, Thrishantha Nanayakkara mapped an entire minefield without once setting foot in it.

This unorthodox de-mining team avoids most of the traditional pitfalls. Metal detectors give too many false alarms, fooled by bullets or other debris. Hand-held ground-penetrating radar machines are too expensive. Dogs weigh enough to trigger mines, injuring or killing themselves and their handlers.

Standing outside a Sri Lankan army base in the spring of 2007, Thrishantha Nanayakkara mapped an entire minefield without once setting foot in it. Nanayakkara held a remote control and periodically made a note on his computer. A mongoose hitched to a robot did most of the work.

Courtesy of Thrishantha Nanayakkara

Two linked robots directly behind the sensor allow a human operator to direct the mongoose over the minefield without risk of personal injury. The robots move by flexing their jointed bodies back and forth.

Nanayakkara, a visiting scholar at the School of Engineering and Applied Sciences and a 2008-09 Radcliffe Institute fellow, picked an indigenous mongoose for its temperament, size (roughly 2.5 kilograms, light enough to step on a mine without detonating it), and sense of smell (able to detect explosives three meters away). He equipped his robot (roughly a meter long and half a meter wide) with a harness to keep the mongoose under control and a video camera to record its findings. Although the mongoose walks a few feet ahead, the robot with its eight metal legs sets the pace. During the test run, the pair went back and forth across a 10-by-10-meter plot, stopping whenever the mongoose detected a mine, which it indicated by sitting up (as it was trained to do). In a morning’s work, the mongoose found every mine.

The land mines in Sri Lanka—and other war-torn nations—are both physical obstacles and obstacles to economic growth. “To understand how de-mining expands economic activity, it is good to imagine the reverse,” Nanayakkara says. “Let’s say there are five land mines in Boston, and we don’t know where they are. Immediately people restrict their movements to the most essential errands. This worsens if we get the news that somebody has been caught in a mine blast. The remaining four land mines can freeze the economic activity of Boston.” In Sri Lanka, the land mines laid by both the government and Tamil Tiger rebels number between 1.5 million and 3 million.

Although Nanayakkara no longer works directly with Sri Lankan military engineers, he is perfecting at Harvard what he once demonstrated in practice. Developed with a team of students at the University of Moratuwa, the robot’s characteristics (such as size, speed, and sensing ability) have now been programmed into a minefield simulation that includes obstacles like trees or rough terrain. By digitally tweaking the robot’s design, Nanayakkara can determine how various mechanical changes improve its efficiency.

Perfecting the machine’s locomotion, he believes, is the first step. He is working with students and professors at Harvard and MIT to develop a spring-loaded leg to help the robot move more easily over the soft dirt of the jungle floor.

He trained his three mongooses mostly through trial and error: rewarding them for reacting to explosives held on a stick, then covering the cage so that they would learn to identify their target by scent, rather than sight. At Harvard, he is taking a more systematic approach by collaborating with assistant professor of molecular and cellular biology Naoshige Uchida, who is studying how rats learn to pick out a single smell in a pungent environment. Nanayakkara hopes that determining how another rodent’s brain sorts smells will lead to improved training techniques that in turn will make his country a safer place to live.

“Land mines write off fertile farmlands and destroy social structures,” he says. “Efficient removal of mines helps the affected communities to return to a normal, productive life.” 

Read more articles by Paul Gleason

You might also like

The Risks of Low-Dose Radiation Exposure

Continuing fallout from the Manhattan Project

Five Questions with Brian D. Farrell

A professor and curator of entomology on beetles, biodiversity, and evolutionary change

This Astronomer is Sounding a Warning on 'Space Junk'

As debris accumulates in low Earth orbit, the danger of destructive collisions continues to rise.

Most popular

“Do You Find That Reasonable?” Harvard Undergraduates Discuss a Changing University

A student panel grapples—civilly—with shifting policies and differing opinions.

The Professor Who Quantified Democracy

Erica Chenoweth’s data shows how—and when—authoritarians fall.

Harvard Adopts Reforms as Higher Ed Turmoil Continues

University creates new “interfaith engagement” role; Columbia, Brown settle with the government.

Explore More From Current Issue

Four 2025 Centennial Medal recipients standing outdoors in a row, smiling, with greenery and a brick building behind them.

Four alumni of the Graduate School of Arts and Sciences are honored.

Colorful glass bottles and nautical trinkets line a window shelf, with a ship in a bottle as the centerpiece.

I Spy Creator Walter Wick at the Norman Rockwell Museum 

Black-and-white photo of a person wearing a “STRIKE” shirt facing a large crowd in a stadium during a protest.

A retrospective on resistance