A lot is riding on the Plexiglas models floating in the ship-testing tank at the Navy's David Taylor Research Center.
Since December, engineers at the research center in Carderock, just outside Washington, have been filling the models with red lubricating oil and then ripping holes in the hull bottoms to see how much flows out.
These simulations of oil tanker accidents, completed last month, are designed to help answer this question: What kind of ship would best protect the environment against oil spills, one with a double hull or one with something called a mid-deck dividing the cargo holds?
The question may sound arcane, but the implications of the answer are potentially enormous, in environmental and economic terms.
The U.S. shipbuilding industry says its ability to tap the $4 billion-a-year international market for new ships is at stake. Some members of Congress have entered the fray, saying the mid-deck design is another Japanese attempt to take away American jobs.
And, in an unlikely alliance, environmentalists have sided with the U.S. shipbuilding industry in opposing the mid-deck design. They favor double-hull vessels, which they say are much more effective than mid-deck ships in preventing oil spills.
Double-hull ships have outer hulls enclosing inner ones, which prevents even a single drop of oil from being spilled in the great majority of tanker accidents.
The mid-deck design -- in which the holds containing the oil are divided into upper and lower tanks -- would leak oil in any accident severe enough to puncture its single bottom. The advantage claimed by advocates of the mid-deck design is that in severe accidents, such a ship would spill much less than a double-hull ship would.
The question is how much less.
The issue of whether mid-deck vessels are accepted as an environmentally acceptable alternative to dual hulls will be decided in early March in London by the International Maritime Organization, the marine safety arm of the United Nations.
The early indications are that the IMO will accept the mid-deck design. An IMO steering committee on tanker design has already drafted a report endorsing the mid-deck based on tests conducted last year at the Tsukuba Institute in Japan. But the steering committee is due to meet again Feb. 28 to consider the results of the Carderock tests before making its final recommendations to the IMO.
IMO approval would amount to an endorsement of mid-deck vessel operations outside the United States and increase pressure to permit their use in this country as well.
However, unless Congress changes the Oil Pollution Act of 1990, enacted after the huge Exxon Valdez oil spill in Alaska in 1989, U.S. waters will be restricted to tankers with double hulls.
Environmentalists, who struggled for years to get Congress to ,, require double hulls, are fiercely opposed to changing the rules.
"From all the information I've seen, it's clear to me the double hull is preferable to a mid-deck vessel," said Sally Ann Lentz, a staff attorney for the Friends of the Earth in Washington.
Most tanker accidents are of the "low-energy" variety, she said. In a low-energy accident involving a double-hull tanker, only the outer hull would be damaged and no oil would escape. In an accident involving a mid-deck vessel, any perforation of the ship's bottom would result in an oil spill.
"The mid-deck guarantees pollution in those low-energy situations," Ms. Lentz said. "I'd much rather have nothing spilled than something."
The results of the Navy lab tests have not been made public, but Ms. Lentz said she has been told they found mid-decks would spill considerably more than advocates of the design have claimed, perhaps three to four times as much.
The environmentalists are joined by the U.S. shipbuilding industry, which sees the mid-deck design as a threat to its existence.
The mid-deck design, in the industry's view, is a ploy by the Japanese to keep Americans from gaining a toehold in the booming international market for new tankers , a market Americans say they need to penetrate in the face of a declining market at home.
Hogwash, say the defenders of the mid-deck.
Both the oil companies and the independent owners and operators of tankers want the mid-deck design to get equal consideration with the double hull. No one, they argue, will have a monopoly on the construction
of mid-deck tankers. And they think it is wrong to refuse to consider anything but double-hull ships, since such inflexibility amounts to slamming the door on development of designs that might prove more effective than the double-hull in limiting oil spills.
In 80 percent of accidents in which the outer hull of a double-hull ship is breached, the inner hull remains intact, according to industry estimates. That means that in four out of five serious accidents involving a double-hull tanker, no oil would escape.
Supporters of the mid-deck design concede that mid-deck ships will spill oil more frequently than double-hulls will. But they maintain that in very serious accidents -- those violent enough to penetrate both skins of a double-hull -- the mid-deck ship would spill much less oil.
For example, if the Exxon Valdez had been a double-hull vessel, both skins would have been pierced when it ran aground in Alaska. The double hull might not have prevented a major spill. Had the Exxon Valdez been of a mid-deck design, a much smaller amount of oil would have been spilled, if the theory is correct.
"That's the principle," said Seth Hawkins, director of program development at David Taylor. "The point of the tests is to find out if in reality this is what happens."
William O. Gray, president of Skaarup Oil Corp., based in Greenwich, Conn., represents independent tanker owners. A longtime advocate of the mid-deck design, he argues that both designs have their drawbacks but that on balance mid-decks are preferable.
"Neither one does everything that everyone would want," Mr. Gray said, but a world fleet of mid-deck tankers, because of their better performance in serious accidents, would mean "less total oil in the marine environment, even though there would be more spills."
In addition, dual hulls might be more susceptible to explosions, because dangerous fumes can accumulate in the spaces between the hulls, Mr. Gray said, noting that fires and explosions account for about 25 percent of marine oil spills.
Some doubts have been raised about whether the mid-deck would really perform as predicted. The mid-deck principle works only if the upper cargo hold is completely sealed off from the lower one. A long crack up the side of the ship, for example, would destroy the pressure differentials that prevent the oil from leaking out of the ship.
Joseph D. Poricelli, a naval architect who is a partner in an Annapolis consulting firm, ECO Engineering Inc., said that when his company examined the histories of six severe tanker accidents, it found that in each case cracks had formed that would have rendered the mid-deck design ineffective.
Many of those who favor mid-deck ships see themselves as advocates of rational choice rather than of one design over another.
Frank Nicastro, coordinator of industrial affairs for Exxon Co. International, a division of Exxon Corp., said the key point is to keep an open mind and to consider dispassionately the results of research such as the tests conducted at the David Taylor Research Center.
"It seems to me we should take this information and try to use it," he said. "We're all environmentalists. We all have a common interest. No one is trying to promote a design that would spill more oil."
Mr. Gray said his goal is not to win approval for one design over the other, but rather to "keep the door open for improved technology."
Ms. Lentz of the Friends of the Earth responded, "If somebody came up with a better idea I'd be behind it 100 percent. The mid-deck isn't it."
John J. Stocker, president of the Shipbuilders Council of America, says acceptance of the mid-deck design is being promoted vigorously by the Japanese because key rights to the mid-deck design belong to Mitsubishi. U.S. shipyards that want to build mid-deck vessels could do so only under license from the Japanese, he said.
Americans think they could compete internationally on double-hull vessels but not on mid-decks.
The market is potentially huge. As foreign tanker owners replace their aging fleets in the next two decades with vessels meeting stricter environmental standards, they will order about 40 tankers a year, each worth more than $100 million, according to Mr. Stocker. That's a market of more than $4 billion a year.
"We want access to that part of the market," Mr. Stocker said.
If those ships are double-hulls, he said, the American industry could win a significant number of orders between now and the end of the century. "Something between five and 10 would be great," he said.
"If we've going to have an industry around in the year 2000, we've got to get our share of the international market," Mr. Stocker said.
Mr. Gray, the representative of the tanker owners, dismisses the suggestion that the mid-deck design is some kind of Japanese plot to control the market.
The mid-deck concept has been around for a long time, and the Japanese don't have a monopoly on the design, he said. In addition, the Japanese could just as easily move to build double-hull ships, which he said don't cost any more than mid-decks.
"To suggest the Japanese are doing this to steal business from someone is patently absurd," he said.
U.S. law requires operators in U.S. waters to convert their fleets to double-hulls over the next two decades. There seems to be little support in Congress for altering the law to permit mid-deck ships.
Rep. Dean A. Gallo, the Republican congressman from New Jersey who sponsored the U.S. double-hull legislation, said that in 1990 the House of Representative endorsed dual-hulls by a vote of 367-to-7. "The feelings haven't changed," he said.