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.