Building america a bubble of steel

This month is the deadline for bids to build what President George W. Bush has called "the most technologically advanced border in American history." The winning plan will encase the nation's 7,000 miles of borders inside a $2-billion virtual "bubble" made of electronic fences, smart sensors, military-grade drones and more all with the aim of keeping out terrorists, illegal immigrants and unlawful commodities.

BLIMPS

Airships hovering above the jetstream serve as telecommunications relays and provide overlapping radar coverage.

DRONES

Unmanned surveillance aircraft flying at 15,000 feet patrol the skies. A Predator B drone has already helped officials nab 1,000 intruders.

WALL OF STEEL

Congress is mulling plans for 700 miles of double-layered steel fencing along the southern U.S. border.

**SURVEILLANCE TOWERv

Cameras and radar give officers real-time views of the environment.

COMMUNICATIONS

Truck-mounted satellite dish

SMART DUST

Wireless sensors no bigger than a speck of dust detect intruders in real time.