Military

by Dr. Jeffrey R. Wyatt

From the moment submarines became serious weapons of war, naval officers have worked to turn them from submersible torpedo boats into true underwater warships - vessels that could operate and fight without having to come up for air. The diesel-electric boat that fought both world wars was like a marine mammal - albeit a very useful one - but submariners wanted their craft to evolve into something more like a fish.

A Naval Research Laboratory technician adjusting the CAMS-I prototype before its first deployment in 1972.

The big challenge was developing air-independent propulsion, and as everyone knows, the U.S. Navy achieved this in 1955 with the nuclear-powered USS Nautilus (SSN-571) and her successors. But little public attention has been drawn to the more basic problem of keeping the air in these latter-day submarines breathable. And even less is known about the way we answered a more fundamental question - how do we know when the air's any good?

That second aspect exposes a difficult problem. Bad air is often odorless and colorless, as we're reminded every winter when people die of carbon monoxide poisoning from defective heaters. Years ago, miners took canaries into the pits with them to detect lethal concentrations of carbon monoxide. The small birds were more sensitive to dangerous concentrations of gas than the men themselves, and when the birds took sick, the miners knew it was time to get out. A variety of chemical sensors later found their way into mine safety equipment and industrial monitoring devices - and into the breathalyzers used by traffic cops and solicitous bartenders. But they were narrowly specialized, detecting only the presence of a small, specific range of compounds.

None of these devices were a good fit with the submarine. Not only is space onboard at a premium, but the sheer variety of toxic, or at least unbreathable, substances that find their way into a submarine's enclosed spaces poses a problem of daunting complexity for atmosphere monitoring. My first experience with the subject came when I arrived at the Naval Research Laboratory (NRL) in 1972 as a postdoctoral fellow to do basic research in a group headed by Dr. Fred Saalfeld, now the top civilian at the Office of Naval Research. At that time Saalfeld was involved in developing the Central Atmosphere Monitoring System, CAMS-I, for submarine air analysis.

From time to time, Saalfeld's group would analyze air samples taken onboard submarines. I still remember coming in over a weekend to analyze a set flown down from New London after one boat had had a fire in port. As it happened, this was the research submarine NR-1, and fortunately, there were no casualties. It was our responsibility to determine if it was safe to go back onboard without wearing protective breathing equipment. In those days, we used "old-fashioned" laboratory techniques to analyze and interpret data, and on my first actual submarine embark in 1975, riding USS Snook (SSN-592) from San Diego to Bremerton, I performed a specialized series of air measurements using wet chemistry. And I experienced firsthand the odor you inevitably pick up riding one of our boats.

Submariners have always needed atmosphere monitoring instruments, and it's important that the equipment be reliable - a monitor that breaks frequently or cries "wolf" with false positives is worse than useless. The crew will only mistrust and ignore it. On the old diesel-electric submarines, there was little you could do to refurbish the atmosphere except for short term, emergency fixes using chemical scrubbing, oxygen candles, or reserve air carried in tanks. The principal method of atmosphere control was surface ventilation, which you had to do anyway to recharge the batteries, so the requirement for atmosphere monitoring was minimal. An old diesel submariner told me once that you could always tell when the oxygen level was getting low when it became difficult to light your cigarettes. That may say as much about how the world has changed since those days as needs to be said.

It really changed when USS Nautilus put to sea in 1955, and it became clear that nuclear submarines would never realize their full potential without finding a way to keep the crew breathing while submerged. Suddenly a submarine could remain submerged for extended periods of time - as the Nautilus did when she transited the polar ice cap in 1958. But although nuclear-powered attack boats could in principle stay submerged indefinitely, their operational routines in the 1950s seldom required them to remain underwater for long intervals. They could and often did surface or snorkel to purify their air. Thus, in preparation for Nautilus' polar voyage, little more was installed than an emergency air breathing system that is still used today on all of our submarines - basically a network of compressed air lines with quick-connect points for emergency breathing masks. All this changed when ballistic missile submarines joined the fleet. From the deployment of USS George Washington (SSBN-598) in the early 1960s, long-term submerged operation was the rule, and atmosphere control became correspondingly more important.

The CAMS-II atmosphere analyzer allows software reprogramming to accomidate new compounds or to modify alarm thresholds.

Not only did oxygen need to be supplied and carbon dioxide removed, but trace contaminants that previously could be ignored became a concern when submarines stayed submerged for long periods. Nautilus at first put to sea without effective means to remove carbon monoxide, hydrogen, and various organic chemicals - and the crew even painted while underway. But early air analyses showed the need for more comprehensive measures, and a catalytic burner was installed. This works by heating the submarine air and passing it over a catalyst that converts the contaminants to carbon dioxide and water. As valuable as these burners proved to be, there were still lessons to be learned, including the importance of keeping them properly adjusted. Fortunately, we no longer have incidents like the one depicted in a cartoon drawn by a Nautilus crewmember, in which formaldehyde in the air threatened to subject the crew to a slow embalming. Actually, the formaldehyde came from partial oxidation of methanol in a badly-adjusted burner, and the methanol was there because of its use as a solvent in shellac.

Catalytic burners remove many undesirable compounds from the air, but they're only one of the systems that maintain the quality of a submarine's atmosphere. Submarines produce oxygen by electrolyzing water - splitting the oxygen from the water it's bonded to. The boats also carry charcoal filters - good for absorbing large spills. And they remove carbon dioxide with a scrubber using the compound monoethanolamine (MEA), which absorbs the CO2 from the air. The MEA is then heated to drive out the gas, and the latter is compressed and ejected overboard.

When nuclear propulsion brought essentially unlimited electrical power onboard, air conditioning came with it. But air conditioning requires refrigerants, and the early systems occasionally leaked refrigerating gases into the submarine's living spaces. These would build up over time, and, while they were in themselves non-toxic, they would decompose in the burner to produce acidic gases that were both toxic and corrosive. The refrigerants would also decompose in the heat of lighted cigarettes, giving the smoke a characteristically unpleasant taste, probably from the phosgene gas that was a product of the decomposition. Tobacco smoke is bad enough in itself, but to combine it with phosgene - a poisonous gas used militarily in World War I - goes beyond adding insult to injury. During the 1960s, one of the most troublesome areas of atmosphere control was the atmosphere monitor itself. These instruments had no special name, but they went through six generations: from Mark I to Mark VI. To have this many versions of a nameless piece of military equipment in so short a time shows there were, in fact, serious problems, and the atmosphere monitor was always on the Submarine Force's top ten list of systems needing critical attention. Sometimes it topped the list.

The Mark I through Mark IV, and the later Mark VI, all used an oxygen meter based on oxygen's distinctive magnetic susceptibility, a hydrogen meter that exploited hydrogen's high thermal conductivity, and infrared adsorption for everything else. In contrast, the Mark V used gas chromatography. The CAMS now uses infrared for carbon monoxide and mass spectrometry for everything else. The Mark I through Mark IV hosted relatively unreliable and insensitive infrared analyzers that had trouble detecting small refrigerant leaks, which then went unnoticed and built up larger concentrations. Then, in a typical vicious cycle, they further degraded the analyzer's reliability. Since the analyzer provided poor readings, crews mistrusted it - and not without justification: A submarine atmosphere analyzer is supposed to operate within the environment it is analyzing. To get around these problems, we then developed the Mark V - which attempted to analyze all the gases with an automated gas chromatograph. With today's microprocessors, we might have made that work, but not in the 1960s, and the Mark V turned out to be a real dog.

At this point, Dr. Saalfeld convinced the Navy to consider an analyzer based on what was then perceived as an exotic laboratory technique: mass spectrometry. The Perkin Elmer Corporation had built a small analyzer as a prototype for NASA's Skylab. It was mounted in USS Hammerhead's (SSN-663) torpedo room, and the crew was instructed to record and compare its readings with those from the Mark IV analyzer. After two days at sea, the
Mark IV failed, but the Perkin Elmer instrument worked fine for the entire trip. Encouraged, we had two more prototypes built and installed on USS Hawkbill (SSN-666) and USS Pintado (SSN-672) in 1972. They performed so well that the crews asked to keep them after the trial period - always a good sign.

Next, a production version of this Central Atmosphere Monitoring System (CAMS) was built and tested to all the rigorous acoustic, EMI, shock and vibration requirements for submarine equipment. Finally, in 1975, twenty years after the Nautilus reported she was "underway on nuclear power," the Navy had a reliable submarine atmosphere analyzer.

Conceptual Diagram of the CAMS-I mass spectrometer, which analyzes gases according to molecular weight. Lighter ions follow a more sharply curved trajectory through a magnetic field, heavier ones travel a less sharply curved path, and they are sorted by multiple detectors.

The good performance of the CAMS-I soon kept refrigerant leaks to a minimum. When a submarine crew saw CAMS indicate increasing refrigerant levels, they were confident that there really was a leak, and would find and fix it. A retired skipper told me once that early in his career he was aboard a pre-CAMS ship with a broken Mark IV analyzer and, coincidentally, a large refrigerant leak. As the refrigerant decomposed, it produced hydrochloric acid. This not only produced significant corrosion throughout the boat, but at the end of the patrol many of the crew (including himself) needed all the fillings in their teeth replaced.

One lesson we learned with the CAMS-I was to make the system drip proof. On the 637-class submarines, the CAMS was installed near the main hatch used to load stores. Often water would come down the hatch and splash onto the top of the CAMS, which could cause electrical problems if the system weren't properly protected. This area also saw a lot of foot traffic in port. I recall visiting USS Sunfish (SSN-649) when a ten-pound bag of premixed cake icing with the consistency of confectioner's sugar was dropped next to the CAMS. At least it was lemon scented.

CAMS-I and its successor CAMS-II remain in use today. CAMS-II's big advantage over CAMS-I is ease of reprogramming. The newest version of CAMS-II allows the system software to be changed in the field using a laptop computer. This enables us, for example, to analyze for new compounds like ozone-safe refrigerants, or to change alarm levels based on new limits in the submarine atmosphere control handbook.

MM1(SS) Ron Brown makes a routine check of the oxygen generator on USS Rhode Island (SSBN-740).

The success of the CAMS program is due to the skill and dedication of many people in the Navy and in industry. Some of them stayed with the program for many years, lending continuity and the positive effects of pride in ownership. Many scientists and engineers rode submarines and obtained a better appreciation for what the fleet needed and did not need. It's important to know your customer. It was great that submariners were willing to accept what then amounted to experimental scientific apparatus aboard their ships and use it. The Submarine Force was far ahead of the rest of the Navy in that regard.

Will a new analyzer soon be designed as a successor to the CAMS-II? I tend to doubt it - the existing system is a good one, and there are few military or commercial pressures driving us to replace it. There is one area, however, in which atmosphere analysis will become increasingly important. As the International Space Station comes on-line, the astronauts and cosmonauts who live and work there will be using atmosphere analyzers based on CAMS technology. With new communities and converging lines of expertise, you often see surprisingly fruitful advances. If space is indeed the deepest ocean, submarine Sailors may find they have more in common with astronauts than they do with their brothers and sisters in the surface fleet.

Dr. Jeffrey Wyatt is senior member of the Corporate Staff at the Office of Naval Research (ONR). He came to ONR in 1999 after 17 years as a scientist at the Naval Research Laboratory (NRL), working in mass spectrometry and the related problem of submarine atmosphere monitoring.