Technology Solutions
Hovering over the past A floating drill developed by the U.S. Geological Survey (USGS) may be coming soon to your air space. Sediments are the main material through which scientists can gain insight into changes to the environment over the past few hundred years, and the Hoverprobe 2000 makes collecting undisturbed sediments from otherwise inaccessible spots like mud flats, beaches, and swamps much easier and less environmentally damaging. The Hoverprobe is actually a combination of two technologies: a magic carpet-like boat that floats on a curtain of air 18 in. above both land and shallow water called the Hovercraft and a Meta-Drill that vibrates to gently probe sediments without requiring potentially contaminating fluids. The new tool is capable of obtaining unaltered sediment cores from places scientists could not access any other way, explains Wayne Newell, a geologist with the USGS Eastern Earth Surface Processes team. It is especially valuable for taking samples from intertidal zones that are inaccessible to boats or trucks, Newell says. Although the Meta-Drill, which can use both steel and plastic drill stems, is one of the lightest drill rigs available, the task of locating it in the middle of the Hovercraft was a huge challenge, says Don Queen, drill chief for the USGS Eastern Region. In fact, when Queen first proposed the idea, nobody believed that it was possible, says Jim Quick, chief scientist for the USGS Eastern Earth Surface Processes team. The prevailing wisdom held that everything on the bottom of a Hovercraft needed to be sealed in order to enable it to run. "A Hovercraft lifts up because it has this closed cap that keeps the air underneath it—if you poke a hole in it, it springs a leak and you lose your lift," Quick adds. © 2000 American Chemical Society
Only slightly heavier than air, the Hoverprobe 2000 does not harm environmentally sensitive marshy areas because it applies less than 1 psi of pressure on the area over which it floats.
In conjunction with MPI Drilling and Hovertechnics, Inc., the manufacturers of the Meta-Drill and the Hovercraft, Queen adapted a design used in ice rescue craft to develop a cap to cover the hole through which the Hoverprobe's drill is raised and lowered. The resulting 2000-lb Hoverprobe is the heaviest craft Hovertechnics has built. It uses a 350 Chevy truck engine to drive 40-in. fans, which provide the same kind of thrusting power that lifts airplanes off the ground. One-third of this air power is diverted to tubes distributed around the bottom of the Hoverprobe to provide equal lifting pressure across the surface area. The remaining two-thirds are used to propel the craft. Conventional drills mounted on trucks, ships, and boats just cannot get into really shallow places like you find in estuaries, Quick says. Additionally, "there are a lot of places that won't allow you to bring in a drill rig because it creates too many ruts—it can do permanent damage," Queen notes.
Over the past year, the Hoverprobe has been used to study nutrients and sediment cycling in the Chesapeake Bay and Lake Michigan. "In Chesapeake Bay, we weren't able to get good cores until we used the Hoverprobe," says Charles Holmes, a geologist who specializes in geochemical dating of sediments. "It allows us to collect longer cores than we could previously collect," says Debra Willard, a geologist who is involved in the Chesapeake Bay projects. Depending upon the composition of the sediments it probes, the floating system should be able to capture cores upward of 120 ft, Queen says. Later this year, the USGS scientists plan to take the craft down to southern Florida, where they will use it in the Everglades and the Florida Bay, Queen says. Other uses of the Hoverprobe are for in situ water quality sampling, to evaluate seismic activity, and to investigate what impact dredging might have on a construction site, says Neil Mark of USGS's Technology Enterprise office. —KELLYN BETTS
DECEMBER 1, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 5 0 7 A
