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In July, few Washingtonians noticed when the military base-closing commission slated the Naval Medical Research Institute (NMRI) in Bethesda for shutdown. Even Bethesdans hardly paid attention: Most probably didn’t realize that the Navy has been performing spooky, underwater experiments just up the street from their $250,000 homes and swank hotels for years. While the suburbanites were donning suits, hopping in their Lexuses, and cruising to downtown offices, NMRI’s divers were living in isolation chambers and pedaling on stationary bikes submerged in dank, 15-foot-deep tanks of water.

But now, after half a century, NMRI (pronounced “Namri”) is closing its Bethesda facility. By 1999 at the latest, the largest of the Navy’s half-dozen biomedical labs will have shuttered its Wisconsin Avenue campus. Most of its 400 employees, principally scientists who conduct basic research on bone-marrow transplants, casualty-wound treatment, and infectious-disease pathology, will move out to Forest Glen, Md. (There they will occupy an enormous new lab at the Walter Reed Army Institute of Research annex. Continuing a robust American tradition, the annex will be named for its benefactor, Hawaii Sen. Dan Inouye.)

NMRI’s daredevil employees, however, are leaving town. The divers are relocating to a similar facility in the sunnier clime of Panama City, Fla., saving the $1.5 million a year it costs to operate NMRI’s diving research center.

Folks at NMRI aren’t too sad about the migration. “The current building has problems with air-conditioning and heating and plumbing,” says Capt. Robert W. Gaugler, NMRI’s scientific administrator. “We are going into a nice new place and I think a lot of people are looking forward to that.” But before the wrecking crews demolish the NMRI complex, Washingtonians should shed a tear for the loss of one of the area’s oddest institutions. As commanding officer Capt. Tom Contreras says, NMRI’s diving research is “pretty cool stuff.”

The diving area at NMRI looks like something out of Logan’s Run. It’s a high-ceilinged room the size of a basketball court. A pair of open-ended metal sewer pipes shaped into mini-submarines dominate the space. Each is as long as a school bus but considerably less roomy. The air smells faintly of stagnant eau de chlorine, and a half-dozen muscled Navy jocks—straight from central casting—stride purposefully around the room, wearing short shorts and tight blue Navy T-shirts. They periodically examine the complicated control panels facing the mini-submarines.

This lab is one of the backbones of the Navy’s diving operation. The entire Navy only employs a few hundred divers, but they perform essential and dangerous duties. Some check for cracks in hulls; others handle underwater explosives; the best belong to the Navy’s elite force, the SEALs. The mini-subs are pressurized chambers where Navy divers—rotated on short stints from their regular assignments—volunteer their health and sanity to improve mankind’s knowledge of underwater endurance. The divers are guinea pigs to the cause of military science, aquatic counterparts to the hotshot pilots of The Right Stuff.

Even after several decades of testing, there’s a lot that the Navy doesn’t know about safe deep-water diving. The only way to fill the holes in its diving manual is to have the volunteer divers sign informed-consent statements, climb into insulated and pressurized chambers, and spend some of the most uncomfortable hours, days, and—in years past—weeks of their lives. After div ers enter a chamber through the airlock, their buddies outside slowly raise the air pressure inside, cranking it as high as 10 atmospheres.

It is this high pressure that allows NMRI to explore the critical dilemmas of diving. As anyone who’s ever taken a scuba lesson knows, going deeper into the water increases pressure on the body—and, more to the point, increases pressure on the air molecules heading to the body’s tissues. The higher pressure packs more gas into the same volume, so each breath sucks in more molecules than the body would normally ingest on dry land.

The NMRI trials attempt to answer two questions. First, what is the best mix of gases for a diver’s air tank? Too much oxygen is toxic; so is too much nitrogen. And second, how can divers avoid the bends? If a submerged diver heads to the surface too quickly, the nitrogen accumulated in his tissues can’t escape and collects in bubbles. If these bubbles form in the spine or the brain, they cause paralysis or death. A mild case—the only kind NMRI divers tend to suffer, and then only rarely—can bring on numbness or pain in an elbow or a knee.

Once inside the chambers, the divers actually spend most of their time out of the water. The high air pressure mimics the conditions they would experience underwater. They sleep on narrow bunks in cramped quarters. Food, reading material, and medicine can be passed through a small, air-locked porthole. Virtually everything, from the enormous circular doors to the sinks, is metal, since high pressure tends to make most materials extremely flammable. The collection of metallica also includes a head. “You haven’t experienced anything in life if you haven’t sat on a stainless steel toilet in the morning,” says Jim Cowden, an experienced diver who’s currently detailed to NMRI.

During tests, divers also test their stamina and gas consumption in the pool, spending an hour and more on the submerged stationary bikes. This imitates the exertion of a real underwater mission. “After you’ve been in the water for 80 or 90 minutes,” Cowden says, “you shiver pretty good. It’s not a Maui vacation.”

Aside from the general discomfort, life inside the chamber follows peculiar rules. Ordinary plastics are banned because they may leak toxic gases under pressure. Glassketchup bottles are wrapped tightly in duct tape before being brought inside because, according to Cowden, “glass shatters twice as bad in here.” And a shattered bottle is a severe danger. Nobody can risk an infected cut inside the chamber because a sick diver can’t be brought out. The chamber must be decompressed very, very slowly before divers can return to the regular world. A rapid re-entry would induce a massive case of the bends.

Divers used to spend as long as six weeks in the pressure chambers, testing the pressure of a 1,000-foot dive. (Most of that time was needed to decompress the chamber safely.) A few years ago, the Navy stopped these marathon sessions. Most of NMRI’s current dives last only a day.

The diving area is not NMRI’s only curiosity. Another group of researchers is studying oxygen-rich environments in an ultraclean building. The air is so oxygenated that even a minute quantity of dust could trigger an explosion. There’s also a bathtub-like apparatus that had its 15 minutes of fame earlier this year, after several Marines died during training in a Florida swamp. To illustrate the effects of cold water on the human body, NMRI allowed a scantily-clad CBS Evening News national security correspondent, David Martin, to sit in the tub and shiver his buns off before a national television audience. “We were getting a bit worried about whether he would make it through OK,” admits one NMRI official who witnessed the event. NMRI was also the site of one of the government’s infamous human radiation experiments.

Because most of NMRI’s work will continue in Forest Glen or Panama City, employees are not exactly frantic over the closing. But there is plenty of nostalgia. Commanding officer Contreras, who expects to serve through most of the transitional period, says he wants to record as much of NMRI’s history before it closes.

So far, however, the Navy’s higher-ups don’t have plans to save the diving chambers from the bulldozers. That’s a pity. After all, a chamber could be the perfect prison for corrupt politicians: a pressurized, isolated, escape-proof room where no one has to listen to them talk.