The U.S. government has decided to retire its most famous research submarine and build a faster, roomier, and deeper diving substitute. On 6 August, the National Science Foundation (NSF) put an end to a decade of debate about the sub's future by announcing that it will shelve the 40-year-old Alvin in late 2007 and replace it with a $21.6 million craft packed with features long coveted by deep-sea scientists.
Alvin entered service in 1967 and is one of five research subs in the world that can dive below 4000 meters (Science, 19 July 2002, p.326). Its storied, nearly 4000-dive career has witnessed many high-profile moments, including the discovery of sulfur-eating sea-floor ecosystems and visits to the Titanic.
Some researchers argued for replacing the aging Alvin with cheaper, increasingly capable robotic vehicles. Others wanted a human-piloted craft able to reach the 11,000-meter bottom of the deepest ocean trench--far deeper than Alvin's 4500-meter rating, which enables it to reach just 63% of the sea floor. Last year, a National Research Council panel endorsed building a next-generation Alvin but put a higher priority on constructing a $5 million robot that could dive to 7000 meters (Science, 14 November 2003, p. 1135).
NSF has followed that advice. A 7000-meter robotic submersible is already under construction, and plans for the piloted craft hew closely to the panel's recommendations. The new sub will be about the same size and shape so that it can operate from the existing mother ship, the Atlantis. But the external similarity, engineers say, disguises a host of major improvements.
A sleeker design means researchers will sink to the bottom faster and be able to stay there longer. Alvin currently lingers about 5 hours at 2500 meters, for instance; the new craft will be able to last up to 7 hours at that depth. Improved electronics will allow colleagues left behind to participate in real time. The new craft will feature more elbowroom inside the titanium sphere that holds the pilot and two passengers. It will also offer five portholes instead of the current three, and the scientists will be able to see just as much as the pilot.
"It's a bittersweet moment. Alvin is a beloved symbol of ocean exploration," says Robert Gagosian, president of the Woods Hole Oceanographic Institution in Massachusetts, which operates Alvin and will run the new craft. "But there's a lot of excitement about the new things we'll be able to do."