Editor’s Note: The April 2014 issue of Scientific American presents an agenda for exploring the ocean’s deepest trenches, and reports on manned and unmanned submersibles that will dive there to look for exotic creatures, evidence of how tsunamis get so large, and perhaps the origin of life on earth. Only three humans have made it to the deepest point on the planet, 10,989 meters down. Movie director and explorer James Cameron did it in 2012. Incredibly, the other two men made the trip together in 1960: Don Walsh, a U.S. Navy officer, and Swiss ocean engineer Jacques Piccard. Below, Walsh describes the final adjustments made to their bathyscaphe, Trieste, during the test dives leading up to the big event, and recounts the excitement and tension he experienced during the dive itself.
In the late 1930s a Swiss physicist, Auguste Piccard, began development of an "underwater free balloon" for deep ocean exploration. He called it "bathyscaphe" from the Greek words for deep and ship.
The operating principle was simple. The balloon (called the float) was a thin metal shell filled with lighter-than-water gasoline. Suspended beneath it was the thick-walled cabin for the crew. The float had ballast tanks to provide positive buoyancy while on the surface. When vented, they filled with seawater so that the slightly heavy bathyscaphe would submerge. Once the dive began the descent was slowed or stopped by releasing solid weights from ballast containers (shot tubs) fitted to the float. They contained several tons of very small steel pellets, or "shot."
Piccard's first bathyscaphe, FNRS-2, was tested in 1948. It made a manned dive to 90 feet and a single unmanned dive to 4,600 feet. Both were successful but the submersible was not very seaworthy on the surface. It was taken to the French naval shipyard in Toulon for a complete reconstruction and upgrading. In June 1953 the French Navy launched their first bathyscaphe, the FNRS-3, which used many of the parts of its predecessor.
After working briefly with the French, Piccard and his son Jacques went to Italy and organized a consortium of Swiss and Italian sponsors to build a new bathyscaphe, Trieste. By the end of September 1953 father and son had made a dive to 10,392 feet in the Tyrrhenian Sea, near the Island of Ponza.
The Piccards had soon found that operational costs for the submersible were too much for them to manage. In 1957 the U.S. Navy’s Office of Naval Research (ONR) contracted for a total of 26 dives involving marine scientists from a wide variety of disciplines.
At the end of the program, the Navy purchased Trieste and shipped it to San Diego’s Navy Electronics Laboratory (NEL). The lab hired Jacques Piccard and Giuseppe Buono (his chief mechanic) as consultants to help the Navy learn how to operate and maintain the submersible, under chief scientist Andy Rechnitzer.
In 1958 I was a submarine lieutenant temporarily serving on the staff of Submarine Flotilla One in San Diego. It was a big command, with 24 submarines and four support ships. The flotilla commodore thought that he should have an aide and he recruited me. On a warm summer day Rechnitzer met us to brief the commodore on Trieste. The commodore asked how the Submarine Force could help. Without a moment of delay, he said, "We need two submarine-qualified officers and about five enlisted men to maintain and operate Trieste, and we need them soon." I subsequently received orders to report as one of the two officers.
A Secret Mission
My colleague soon became ill with a condition requiring light duty and a fairly prolonged period of recuperation. Sadly he had to leave the program and I became the officer in charge, with Lieutenant Larry Shumaker as my assistant officer.
The first months of 1959 were very busy at NEL. We did a few dives off San Diego in Trieste's “as delivered” configuration before sending it to the Navy’s Ship Repair Facility for conversion work. In March I did make a dive to more than 4,000 feet in the San Diego Trough. Impressive…this kind of seagoing was going to be pretty exciting!
However, it was not until I joined NEL that I learned what a few insiders had in mind for the bathyscaphe. This was to dive it into the deepest known place in the world! The location was the Challenger Deep in the Mariana Trench some 200 miles from the Naval Station at Apra Harbor, Guam. The depth was about seven miles. When Andy had briefed the commodore he had left this one out!
This was pretty exciting stuff for a couple of submariners who usually hugged the coast. The last sub that I served on had a maximum operating depth of 300 feet.
Trieste would need to be significantly modified. As delivered it could dive to a maximum depth of 20,000 feet. This limit was imposed by the strength of the sphere (cabin) and the amount of gasoline (buoyancy) the float could carry. A new cabin and enlarged float would be needed.
The new sphere was ordered from the Krupp Works in Essen, West Germany. It would be built for 50,000 feet maximum depth, just in case any place in the ocean was found to be that deep. As delivered, the Krupp sphere was a thing of beauty. The walls, five to seven inches thick, were made in three rings and glued together with epoxy at the two joints. The admiral who was head of the Navy’s Bureau of Ships came to see Trieste at NEL. He asked how this very smooth sphere was fastened together. I told him it was glued. He fixed me with an admiral's “evil eye” and said, "Lieutenant Walsh, the Navy does not glue its ships together!" Perhaps, but ours was glued.
The float was lengthened to increase our gasoline capacity from 28,000 to 34,000 gallons. In addition, bigger ballast tubs were built to increase shot capacity from 11 to 16 tons.
While the yard work was going on we were also developing an operational plan for our deep dive program, now named "Project Nekton." While ONR had provided the funds for upgrading Trieste, the policy levels of the Navy had not yet been informed about this deep dive program.
After many meetings I found myself in front of Admiral Arleigh Burke, the chief of Naval Operations. I briefed him and he reluctantly agreed to the project. However he directed that our intentions not be publicized until we were successful. He did not want a high-visibility flop. I called NEL and gave them the good news.
Guam Is Good
The modified Trieste was reassembled and did two test dives off San Diego in mid-September to ensure all the modifications functioned properly. Then we took it apart and loaded it on a commercial cargo ship headed to Apra Harbor at Guam. The ship sailed on 5 October with two of our enlisted men to make sure everything stayed secure.
The rest of the team of three military and seven civilians from NEL flew to Guam to prepare our support base there. Working from dawn to dusk, seven days a week, our little 14-man team began a series of increasingly deep test dives from November to December 1959. All seemed to be working well.
Then on 15 November Andy and Jacques set a new world's depth record with a dive to 18,150 feet.
However, we encountered a significant problem. During the six-hour dive the sphere was soaked in very cold seawater, long enough for the metal to become quite cold. When the bathyscaphe surfaced into the warm tropical waters, the differential expansion across the joints caused the glue joint to fail with a great bang. This was not inherently hazardous, as sea pressure would hold the three pieces in place. But it was clear that we would have to dry-dock Trieste to fix the problem. The big worry was when the sphere was removed from the water, would those pieces slide apart, since there was no sea pressure to hold them?
Very gently the bathyscaphe was set down on its cradle. The three components of the sphere did slip a bit but only few thousandths of an inch. And there was evidence of some saltwater weeping inside the cabin. Our very creative machinist Chief Petty Officer John Michel took charge of the fix. He realigned the three pieces almost perfectly using a forklift truck and a large timber “battering ram” to jolt the pieces into approximate alignment. Then he built a series of bands that went around the outside of the sphere to mechanically hold all the pieces together in alignment. Rubber bands covered the sphere joints and an automotive gasket compound was used to make them watertight. It was a remarkable piece of “shade-tree engineering.” It saved our Project Nekton.
It was difficult to avoid telling our masters in San Diego about this minor operational problem. But we felt that any whiff of this problem would result in an order to cancel the program. We managed to maintain security pretty well even though several of our temporary civilian workers were moving back and forth between Guam and San Diego.
A month later the repaired Trieste was back in the water. On 14 December we made a test dive in Apra Harbor and a few days later Jacques and I dove to 5,450 feet about 50 miles offshore. This completed our operations for 1959, a year in which Trieste had made 13 dives with the U.S. Navy.
Dive to the Ocean’s Deepest Place
On January 15, 1960 Jacques and I dove to 23,000 feet in the Nero Deep. We did not land after sighting the seafloor because we needed to get back to Guam as soon as possible to prepare Trieste for the deepest dive.
On the 19th our little flotilla departed Apra Harbor for the Challenger Deep. The towing vessel was USS Wandank, and USS Lewis was our headquarters ship. It would be a long 200-mile tow, at a stately 5 knots. But even at that slow speed we were very concerned about possible damage while at sea.
Andy and I were on board Lewis, which went ahead to the vicinity of the dive site. Time would be needed for us to make an acoustic survey to locate the Challenger Deep. Lewis’s depth sounder could not see the seafloor at such a great depth so Andy developed a scheme to use small blocks of TNT. We would start a stopwatch when the charge went off and stop it when we heard the return echo on the ship’s fathometer hydrophone. We did not care about exact depth measurement, only that 14 seconds was deeper than 12 seconds, and so on.
When Wandank arrived on site we were pretty sure we had mapped a zone about four miles long and one mile wide. The 20 to 25-foot waves made it difficult getting from the ships to board the bathyscaphe. Fortunately, we found only minor damage from the long tow.
We prepared to start the dive as soon as possible. At about 08:00 all preparations were completed and we bolted the heavy entrance door closed behind us. By 08:30 we were on our way, hopefully to a successful culmination of Project Nekton.
Once below the surface the ride was a lot better and the descent proceeded smoothly. From 300 to 500 feet we ran into some strong thermoclines and our balloon just bounced along on top of them. We valved off gasoline from our maneuvering tank and finally got heavy enough to break through. This had really slowed us down so we increased our rate of descent, because it was important that we be back on the surface with sufficient daylight left to prepare Trieste for tow back to Guam. Those were things we did not want to do in the dark in high seas.
Between 4,000 and 7,000 feet a couple of hull penetrators began to weep some water drops. This had happened before and the remedy was simple. If the number of drops increased with depth, the dive was over and then we would surface. Today the drops decreased and the dive continued.
At 31,000 feet Trieste was jolted by a muted bang. In the past we had some very small external components fail but those events produced sharper sounds of implosions. This noise was much lower in pitch, as if something big had broken.
We checked our instrument readings and all seemed well, and Trieste was descending at the same rate as before, so we decided to proceed. Clearly nothing major had failed.
At about 34,000 feet we turned on our small fathometer. It could give us up to a 600-foot trace of the seafloor beneath us. I was monitoring it closely while Jacques was at the single viewport. Using our outside lights we could also see a glow beneath us when the light reflected off the seafloor.
At 35,000 feet there was still no indication of the seafloor. We knew the fathometer was working since we could see reflections from the iron shot we dropped to slow our descent. By this point we were just barely moving.
Then we passed 36,000 feet. Where was the bottom? We kept moving down as slowly as possible. Finally I began to see a bottom trace on the paper chart. I advised Jacques and called off our height above the bottom as we approached it. As we got closer he could see the loom of our lights and released just enough shot to make an easy landing. Our depth gage read 37,800 feet. We had found a new depth in the Challenger Deep!
Just before we landed Jacques asked me to look out of the viewport. He said, “Do you see that fish on the bottom?” I saw a ”flatfish” like a small sole or halibut. It was whitish in color and about a foot long.
Though very brief, this was an important observation. First, it told us that there was a higher-order marine vertebrate living at this incredible depth. Second, if there was one then there were probably many as this was a bottom-dwelling fish. And third, there were sufficient nutrients and oxygen to support life at the deepest seafloor.
After we landed Jacques and I shook hands and expressed our feelings of relief and joy. Our small Project Nekton team had said we would do it and we did! It was a great day for all of us who had worked so hard for nearly five months at Guam.
While on the seafloor I turned on the aft viewing light and looked out through the port in the entrance hatch. And there was the answer to the big bang at 31,000 feet. The curved acrylic window at the back of the entrance tube had a big crack across it. Thankfully this was not a pressure boundary since the tube was always flooded during the dive. Once back on the surface we would use compressed air to blow out that water and then exit from the sphere. If that window failed while blowing down the tube, we could be trapped inside for several days.
After spending 20 minutes on the bottom we had to leave to get back up in daylight. We did not get any photographs because our landing stirred up so much bottom sediment that there was no visibility. On previous dives the cloud would drift away after a few minutes. It did not happen this time and it was like being in a bowl of milk for our entire time on the bottom.
Leaving the bottom at 13:30 we headed upwards at a good rate of speed. With no worry about groping our way to the seafloor we could just dump ballast and head home. After a three and a half hour ascent we reached the surface with plenty of time left to secure Trieste in daylight.
We gently put the compressed air into the entrance tube to avoid stressing the cracked window. It was slow, taking 15 minutes for an operation that usually took a few minutes. As the water level passed below the viewport in the hatch we could see that the window was holding. When the last of the water had blown clear we quickly let ourselves out of the sphere, shutting the heavy hatch behind us, and we went topside. We saw that the sea conditions were even worse than before.
Once Trieste was secured to the towing line and Wandank had taken the course back to Guam, the Project Nekton principals, Rechnitzer, Piccard, Shumaker and myself left the area on board Lewis. We had been ordered back to Washington, via NEL, to undergo a few days of "celebrity.” The highlight of the trip was a meeting with President in the White House, where he presented us with awards and we gave him one of the American flags and a signed philatelic envelope that we had carried on the dive.
Diving for Science
After rounds of visits with members of Congress and senior officers in the Navy Department we were ready to go back to work. One of the more important visits was with the Chief of Naval Operations. Admiral Arleigh Burke was smiling a lot more than when I had last seen him!
Jacques went home to Switzerland, his consulting work with the project completed. After some time at San Diego, Andy, Larry and I returned to Guam for Project Nekton II. For this project all our dives would be for science. We intended to repeat the Challenger Deep dive, however the Navy reduced Trieste's depth capability to 20,000 feet. Apparently they now had questions about the integrity of the sphere. It was never clear to me how they could remotely make this engineering decision.
By August 1960 our operations at Guam were completed and we shipped the bathyscaphe and all our supporting equipment back to NEL. In addition to repairing wear and tear, Trieste would now undergo some significant modifications based on lessons learned while at Guam. These activities would keep us busy for several months.
Trieste was operational again in late 1961 and we began dives off San Diego in support of NEL research projects. During that year our team began to go on to other assignments. Andy left for an excellent position with North American Rockwell, and later in the year Larry left to return to submarine duty. Finally in July 1962 I was relieved by Lieutenant Commander Donald Keach. It had been an amazing three and a half years for me. My wish had come true. I had gotten away from that desk on board the submarine tender!
Before we left NEL, Andy, Larry and I had developed a conceptual design for a new bathyscaphe. It was clear to us that the nine-year-old Trieste was getting frail and had limited potential for further upgrades. The Navy approved our concept and Trieste II was built at the Mare Island Naval Shipyard in San Francisco Bay. It was put into service in the late spring of 1964 so none of us had the opportunity to dive in it.
However, tragedy created one more mission for the original Trieste before its retirement. In April of 1963 the nuclear submarine Thresher was lost during a test dive off the New England coast. Once the wreckage had been found by surface ships, Trieste was mobilized to make forensic dives at the site. Based out of Boston, the submersible made several dives and some small bits of wreckage were recovered. The bathyscaphe returned to NEL in the fall of 1963 and was taken out of service at the age of 10. Her team now awaited delivery of the new Trieste II.
Later in the 1960s the original Trieste II was replaced with another Trieste II, also built at Mare Island. It had a much greater payload (lift) capabilities and increased endurance for longer missions. These were needed for classified operations that had been delayed by the Thresher tragedy.
However, those operations had to be delayed again when the Scorpion submarine was lost off the Azores in about 9,800 feet of water. The new Trieste II successfully made several dives at this site as part of a program to find out what caused Scorpion to sink.
It was not until the early 1970s that classified work could begin but by this time there were more effective ways to do many of the missions originally planned. Finally in 1984 Trieste II was retired at San Diego. The U.S. Navy had operated bathyscaphes successfully for 26 years. About 250 Navy submariners served in these underwater “spaceships” and are entitled to wear the special deep submergence operator pin.
Today one can see the original Trieste at the Navy Memorial Museum in Washington D.C. and the last Trieste II at the Naval Undersea Museum in Keyport, Washington.
The 50th anniversary of Trieste’s ultimate dive was celebrated at the Navy Memorial Museum in Washington D.C., 15-19 April 2010. The occasion was a reunion of many of those who had worked on and operated the Navy’s three bathyscaphes.
What’s Next?
For more than a third of a century the U.S. and French bathyscaphes were the only means to get man into the deepest parts of the oceans. Since the early 1960s more than 200 manned submersibles were developed worldwide. Although few remain in service today, we can see our technological fingerprints on most of those.
The capability to do deep underwater operations with manned and unmanned vehicles now exists in many places throughout the world. There are seven manned submersibles: four Russian, one French, one Japanese and one Chinese that can dive to 20,000 feet. The deepest is China’s Sea Dragon, which can dive to 23,000 feet. By going to this depth these vehicles can access more than 98 percent of the world’s sea floor.  
The U.S. Navy no longer operates manned deep sea vehicles. The Woods Hole Oceanographic Institution in Massachusetts has a program to upgrade its venerable Alvin to be able to dive to 21,320 feet. Partially funded, that program is moving very slowly.
However, 52 years after Trieste’s deepest dive, the Challenger Deep was again visited by a manned vehicle. On 26 March 2012, James Cameron piloted his Australian-built DEEPSEA CHALLENGER to the seafloor there.
Cameron began planning this project in 1993 but other commitments forced delays. Construction was done in Sydney, Australia, with the submersible being completed in January 2012. I was invited to Sydney that month and was tremendously impressed with the careful thought and engineering excellence that went into the vehicle’s design and construction. Even though it’s a one-person vehicle it was nicely set up to do productive scientific work. And weighing only 12 tons, its diving operations can be supported by a wide variety of ships.
Cameron’s dive duration was nearly eight hours, with three hours spent on the seafloor. By comparison, only 20 minutes of Trieste’s nine-hour dive was at the bottom.
Others have their eyes on the deep, too. In April 2011 Sir Richard Branson and his American partner Chris Welsh announced Virgin Oceanic. The goal is to dive in a one-man submersible into the deepest places in the five oceans. Another relative newcomer, Triton Submarines in Florida, has developed plans for a three-person full depth submersible, Triton 36,000. It will feature a revolutionary all-glass pressure hull. Glass is a very strong material but hard to fabricate and protect from damage during operations. Triton believes they have a construction process that will greatly mitigate the problem.
Two unmanned vehicles have visited the Challenger Deep. In 1995 and 1997 the Japanese Kaiko, a remotely operated vehicle (ROV), dove there. Then in May 2009 the Woods Hole ROV, Nereus, also went there. (A new Nereus mission was scheduled to take place this April.)
In my view, unmanned vehicles will do the majority of the future work at the great ocean depths. They cost less to build and operate and they do not have to support people. However, there always will be the need to send humans to explore. We must continue to go in person to put the trained mind and eye into the uttermost reaches of the oceans’
And as James Cameron said, “What kid wants to grow up to be a robot?” There will always be a place for men and women in deep ocean exploration. I was glad to be there at the beginning a half century ago.