'DARPA hard: research agency wants help solving the seemingly impossible.

• Author: Magnuson, Stew
• Position: ANALYSIS - Defense Advanced Research Projects Agency

ANAHEIM, Calif. -- The Defense Advanced Research Projects Agency has a reputation for taking on challenges that sometimes seem to defy the laws of physics--or at least common sense.

The term "DARPA hard" refers to the problems its researchers attempt to solve. Sometimes their projects work and they make a profound impact. The Internet is one example. Sometimes the challenges are too tough. But that's okay. The agency was created to push the research envelope, its staff says.

"Please tell us that it's something that can't be done. It's science fiction." said Brett Giroir, director of the defense sciences office. "That is a challenge we can't resist."

Every 18 months, during the three-day DARPATech conference, the agency trots out is program managers who outline the top items on their wish lists. Scientists, researchers and engineers from throughout the country come to see if they can contribute and maybe snag a contract with the agency.

Missed the conference? No problem. National Defense lists the toughest nuts DARPA needs help cracking. Have a solution to one of these dastardly hard problems? If so, DARPA would like to hear it.

Transparent walls and dirt.

One of the most basic military tactics is to successfully hide from adversaries. Potential U.S. enemies have created thousands of underground structures to hide missiles, weapons of mass destruction, command and control facilities or they may use tunnels to launch attacks. Insurgents may also hide in buildings.

DARPA wants to defeat rock, concrete and plaster walls--not by blowing them up--but rather by making them "transparent," said strategic technology office program manager Joseph Durek.

The agency is creating a suite of sensors to map the inside of buildings, tunnels, caves and underground facilities.

"I want to know how to make these physical shields transparent," he said.

The goal is to make three-dimensional blueprints without being inside the structures. Sensors that measure gravity can be used to find empty spots beneath the earth, Heat signatures can detect cave entrances. In an urban setting, these signals are not easy to detect and the environment is cluttered, he said. And the sensors must be discreet. They can't be easily discovered or destroyed.

The "Visi-Building" project, for example, is looking into radar to probe a building, but it must untangle the complicated scattering of energy inside the building, he said.

Once underground facilities are detected, DARPA wants to penetrate and destroy what's inside without having to resort to nuclear weapons.

If soldiers are...