You might assume that a robot with a heroic name like Explorer would be designed to orbit a distant planet, probe the interior of a volcano or roll over the rock-strewn surface of Mars.

	Martha Rial, Post-Gazette Scientist Hagen Schempf with Explorer, a robot he created at the National Robotics Engineering Consortium in Lawrenceville. Click photo for larger image.

But the Explorer robot developed by Hagen Schempf probes a less exotic, but similarly difficult-to-access world -- the natural gas pipelines buried beneath us.

Shaped something like a worm, or a string of link sausages, the 5-foot-long Explorer can crawl through miles of live natural gas lines, using fish-eye cameras at either of its ends to search for leaks or for pools of water that have seeped into the system.

Once inside a 6- or 8-inch gas main, Explorer can prowl around for hours, making 45- or 90-degree turns at pipe joints when necessary. And it operates without a tether, so human controllers at the surface direct it by a wireless remote control.

"You can inspect a whole neighborhood in a matter of hours," said Schempf, a principal systems scientist at the Carnegie Mellon University Robotics Institute. That means workmen have to dig only one hole down to the gas main to insert the robot and, in urban environments such as Pittsburgh or Yonkers, N.Y., digging the hole can be the most expensive part of the inspection process.

It was in Yonkers that the Carnegie Mellon team and their colleagues at the Northeast Gas Association tested Explorer last month. Explorer was placed in an 8-inch-diameter, cast-iron gas main in the Consolidated Edison of New York system. It inspected hundreds of feet of the line, which originally was installed in 1890.

"We were delighted with its performance," said Rodney Anderson, technology manager for natural gas delivery at the National Energy Technology Laboratory in Morgantown, W.Va., one of Explorer's sponsors. "We're really excited about this new type of technology."

Anderson, in fact, envisions later generations of robots that not only operate remotely, but also actually "live" in the gas mains, constantly prowling on the lookout for leaks. The robots eventually might even be equipped to make some repairs on their own, he added.

The demand for such technology is increasing, Anderson said, in part because much of the existing natural gas infrastructure is more than 50 years old. U.S. gas companies are spending an increasing amount of money on detecting and repairing gas leaks, now more than $300 million annually in urban and surburban areas.

Gas companies also are facing new federal mandates to perform regular inspections. After pipeline ruptures in Carlsbad, N.M., and Bellingham, Wash., Congress passed the Pipeline Safety Improvement Act in 2002. The law requires problem pipelines to be inspected within five years and all pipelines to be inspected within 10 years. All would be reinspected at seven-year intervals.

The state of the art for pipeline inspection today is a 1- or 2-ton device that is inserted into a pipe. Propelled by gas pressure, it travels tens of miles, recording magnetic flux data that can later help workmen pinpoint areas of weakness or leakage.

The devices are called smart pigs because they make a noise not unlike that of a squealing pig as they are blown down the pipe. Yet large segments of pipeline, at least 30 percent of major gas lines, are "unpiggable" because of bends and turns, or because the line simply can't support such a massive device.

Special cameras and other instruments on tethers can be inserted for inspections over short spans, Anderson said. But the only way to inspect many unpiggable pipelines, he said, is to dig down and inspect them from the outside, a huge expense in urban areas.

Over the past 20 years, Schempf has been involved or led the development of dozens of robots, including Jason, the underwater exploration robot developed at Woods Hole Oceanographic Institute, and Neptune, a robot for inspecting above-ground fuel storage tanks. Most recently, he was the principal investigator for Dragon Runner, a robot developed for the Marines for urban warfare that is being deployed in Iraq.

The challenge in designing Explorer, Schempf said, was similar "to packing 12 pounds into a 6-pound bag." The robot had to be as small and lightweight as possible so it could fit inside 6- and 8-inch mains and successfully negotiate joints. Because it is untethered, it also must carry its own power supply.

The 4-inch-diameter robot is divided into seven segments, or modules, connected to each other by articulated joints. Propelled by small wheels that press against the interior of the pipes and joints, Explorer has special software that allows it to make 90 degree turns without human intervention.

With a camera on each end, Explorer can readily find pools of seepage water, one of the major problems found in cast-iron mains. Additional magnetic flux or other sensors may be needed for inspecting steel pipelines.

Though Explorer is an electrical device operating in mains filled with flammable gas, explosions are not a major concern because the robot is purged of oxygen. Without oxygen in the pipeline, sparks from the robot can't ignite the natural gas. Consequently, the riskiest parts of the inspection process is the insertion of the robot into the pipe and its subsequent retrieval.

Schempf said he conceived the robot several years ago and obtained support from both NASA and the Northeast Gas Association for its initial development. Later, the Department of Energy also became a sponsor.

Anderson, of DOE's National Energy Technology Lab, said Explorer was one of two alternatives to smart pigs that the DOE is sponsoring. The other, Roboscan, is being developed by Foster-Miller Inc. of surburban Boston, and is designed to operate in 20-inch gas pipelines. Unlike Explorer, Roboscan is tethered.

Schempf estimated robots such as Explorer could be built for $50,000 to $100,000 "in onesies and twosies," and perhaps $25,000 to $60,000 if produced in large quantities. But ultimately, the inspection robot business will not be about selling robots, but about selling the service to gas distributors. "You charge by the foot" of pipeline inspected, he said.

After last month's successful test in a low-pressure pipeline, a second test in a high-pressure steel pipe is now being planned either for next month or early September, probably in New England, he said.