【溫馨提示】 dwg后綴的文件為CAD圖，可編輯，無水印，高清圖，壓縮包內(nèi)文檔可直接點開預(yù)覽，需要原稿請自助充值下載，請見壓縮包內(nèi)的文件及預(yù)覽，所見才能所得，請細(xì)心查看有疑問可以咨詢QQ：414951605或1304139763
searching deeper
After more than four decades investigating the ocean floor, the U.S. Navy's deepest-diving submersible is about to be replaced.
Common wisdom holds that a human body renews itself completely every seven or eight years. That is, all its building blocks—amino acids, cells, DNA strands—have been replaced. But somehow, although we're chemically different, it's still the same old us.
We bring this up because we were thinking about Alvin, the first U.S.-built, manned deep-ocean submersible, and how after 42 years of profound dives, the pressure vessel operated by the Woods Hole Oceanographic Institute is heading toward retirement.
It seems that every three years or so the sub is disassembled to its hull, so every part of it can be checked. Then it is reassembled, often with improvements. That has happened so many times over the past 40 years that every part of the vessel has been replaced. According to Shelley Dawicki, the director for public relations at the institute, "Gradually, after 42 years, no parts are original."
But somehow it's still the same Alvin, which took its first dive in 1964. The craft originally dove to depths of 6,000 feet, or less than 2,000 meters. Now, since its stainless steel crew module was replaced with one of titanium in 1973, it can dive about 4,000 meters, or more than 14,000 feet. That means it reaches about 63 percent of the ocean floor, where it moves cautiously, about a mile or mile and a half an hour, powered by golf cart batteries, through terrain no one from the surface has ever seen before.
Dawicki told us that Alvin had one of its periodic overhauls less than a year ago, but the craft can't be upgraded to do much more than it does now.
The Alvin deep-sea, manned submarine has been continuously retooled during its 42 years, yet still bears a striking resemblance to its original form, seen here in the mid-1960s.
In its lifetime, the little submersible has located a lost hydrogen bomb in the Mediterranean Sea, explored deep-sea hydrothermal vents (where it collected evidence of about 300 previously unknown life forms, including giant tube worms), surveyed and helped photograph the Titanic, and accidentally gave scientists vital feedback about decay in the deep. Researchers who need deep-sea access put their names in and wait a couple of years to see if their project wins a berth for an eight-hour dive.
Alvin, we're told, has made more than 4,000 dives. Woods Hole Oceanographic Institute in Massachusetts operates Alvin for the U.S. Navy, as what it calls a "national oceanographic facility." Now the institute plans to bring aboard a second submersible within the next two years.
The new vessel will be a civilian craft, funded by the National Science Foundation. We couldn't confirm that it will be called the Alvin II. We did learn, though, that it will go far deeper than the Alvin, down to 6,500 meters, or more than 21,000 feet, for access to nearly the entire ocean floor.
Another innovation will be in the area of visibility. Dawicki said that when Alvin was introduced, its three view ports—one for the pilot and one each for two researchers—provided exceptional visibility. It was also unusual in that the vessel required only one pilot, instead of two, so the third seat could go to a researcher. The new submersible will have a total of five view ports, Dawicki said.
Alvin's main engineer, Harold Froehlich, was an aerospace and mechanical engineer for General Mills. He designed the submarine in 1962 from plans for Seapup, a never-built deep-sea submarine he'd designed.
How a cereal company headquartered in landlocked Minnesota came to build the United States' first manned deep submersible is a story unto itself. Froehlich helmed the crew that built the three-person craft for the U.S. Navy.
After World War II, naval officials realized that Japan and Germany knew more about building submarines—and about the largely unstudied underwater world—than the United States did. The Navy needed to catch up.
To that end, in 1953 it purchased the deep-diving
bathyscaphe Trieste, designed by the Swiss explorer Auguste Piccard. The Trieste was quite large and not very maneuverable. It had to be tethered to a service vessel. The Navy sought a deep-sea submarine that wouldn't be so dependent on a ship.
Froehlich, who had spent five years in the Pacific theater during World War II, knew exactly what the United States needed. But was such a thing feasible? In the late 1950s, he sat down to tinker with his Seapup idea to find out.
As it turns out, such a thing could work. And when executives at General Mills learned of Froehlich's Seapup, they decided to bid on the naval contract. Although the company's name is synonymous today with cereal, that certainly hasn't always been the case. In fact, General Mills had been heavily involved in war work and by the late 1950s was looking to retool wartime operations for home front activities. Streamlining to its current focus on food would come later, said Kirstie Foster, a General Mills spokeswoman.
The company earned the bid in 1962 for $472,517. Froehlich and his team delivered the submarine a scant two years later. When Litton Systems took over the building of the Alvin from General Mills, Froehlich moved over, too.
Woods Hole can thank Froehlich for the craft's unique longevity (the submersible has been retooled numerous times, but still retains its original shape). The aeronautical engineer put to good use his knowledge of robotics and hydraulics. General Mills won the contract in part because the craft included portholes designed to withstand the intense undersea pressure and had two hydraulic-arm manipulators.
The craft can withstand 6,500 psi. Although it is headed toward retirement, it remains state-of-the-art, according to Woods Hole. Dawicki said that the only reason it is being retired is that there isn't enough money available to operate two deep-sea submersibles.
But the submarine is best known for its first manned dive, in July 1986, to the hulk of the rusting Titanic that rested 12,460 feet in the sea. Photographs from that dive have been published in National Geographic magazine, because the National Geographic Society funded the dive.
Froehlich received the Elmer A. Sperry Award in 1989 in recognition of advancing the art of transportation. Four engineering institutions, including ASME, sponsored the award, as did the American Institute of Aeronautics and Astronautics.
The man behind a sub with such a rich history remains mild-mannered, being sure to give credit where credit is due. But the Alvin and its exploits surely affected his life.
After all, Froehlich said, in his family's home, Alvin is always acknowledged as his and his wife's third child.
?
? 2006 by The American Society of Mechanical Engineers