September 1, 2005 On a shoestring, and with off-the-shelf components, students are designing prototypes of robotic blimp that could one day be used by the Pentagon. Cheaper than spy satellites, blimps can hover in place for months, powered by solar panels.
BALTIMORE--You see them floating above football stadiums, but blimps are now being used for more than games: They're a cheap and safe way to get a bird's-eye view of the ground below. Recently, some students have decided to take their science class outdoors, putting a class assignment to the test and helping to send blimps into near space.
Making the grade isn't the only reason mechanical engineering student Nick Keim helped build the blimp. His student airship is now part of a project to send a bigger, un-manned blimp high in the sky.
Keim, a student at Johns Hopkins University in Baltimore, says, "We designed a smaller-scale airship that could prove that you can control an airship to fly itself." The amateur blimp is helping professional engineers design a high altitude reconnaissance vehicle, HARVe, a first-of-its-kind blimp to hover in near space.
"The military has a need for this kind of observation capability," says Vince Neradka, an aerospace engineer at Johns Hopkins' Applied Physics Laboratory in Laurel, Md.
Satellites are costly and constantly on the move. The space blimp is cheaper, disposable, and can float in one place for weeks. Neradka says, "This HARVe is going to stay and watch around the clock and provide information that the battlefield commanders today just don't have."
The blimp is packed inside a rocket and launched from ship, plane or submarine. Once in space, it self-inflates. Solar panels provide power to steer propellers and a camera and communications device send satellite-quality pictures back down to earth.
The students had to keep costs down and work within a limited budget. They purchased many of the blimp's working parts from remote-control hobby stores. The total cost was $12,000. Researchers say the real blimp is designed for near space, which is higher than commercial airplanes fly, but not as high as satellites orbit. The blimp should be ready within five years.
BACKGROUND: Three undergraduate students at Johns Hopkins University have built a model airship that will aid professional engineers who are designing a military craft to conduct surveillance at the outer edge of the Earth's atmosphere.
HOW IT WORKS: The 17-foot-long helium-filled blimp has four propellers and is outfitted with sophisticated electronics that enable it to fly by itself. It follows computer commands to move itself to a predetermined location, but the craft can also be steered manually using a wireless remote controller. An on-board video camera transmits real-time images from about 50 feet above the ground.
WHY IT'S USEFUL: The student model was designed to test and refine the guidance, navigation and control of such a craft for a larger version being developed by the university's Applied Physics Laboratory. Dubbed the High Altitude Reconnaissance Vehicle (HARVe), the airship would be stuffed inside a missile, which would carry it to near-space altitude. Once released from its carrier, a mammoth balloon would self-inflate and carry a gondola equipped with sensors and propellers. The full-sized system would be an inexpensive disposable airship that would hover high over a military location for several weeks, sending images of ground activity and relaying communications. Then the airship would either disintegrate or be destroyed.
LIGHTER THAN AIR: Blimps, or airships, operate on similar principles to hot-air balloons. In 1780, two French paper makers, the Mongolfier brothers, noticed that smoke from a fire built under a paper bag would cause it to rise into the air. The hot air inside expanded, and thus weighed less, in terms of volume, than the surrounding air. This creates "lift," enabling an object to float. The Mongolfiers put the concept to practical use in 1782 when they built the first hot-air balloons. In 1852, another Frenchman, Henri Giffard, built the very first airship, or dirigible. Its enormous envelope was shaped like a cigar and filled with hydrogen, a gas that is lighter than air at normal temperatures -- such as is helium. Giffard's machine was also outfitted with a steam engine, which turned a propeller to create thrust, and rudders to help with steering.