Sub Marine Explorer - Construction

Construction

Sub Marine Explorer had an external large volume (560 sq. ft.) high air pressure chamber which was filled with compressed air at a pressure of up to 200 pounds per square inch (1,400 kPa) by a steam pump mounted on an external support vessel. Water ballast tanks were flooded to make the Sub Marine Explorer submerge. Pressurized air was then released into the vessel to build up enough pressure so it would be possible to open two hatches on the underside, while keeping water out. This meant that air pressure inside the submarine had to equal water pressure at diving depth, exposing the crew to high pressure, making them susceptible to decompression sickness, which was unknown at the time. To surface, more of the pressurized air was used to empty the ballast tanks of water. A contemporary (August 1869) newspaper account of dives in Sub Marine Explorer off Panama documents 11 days of diving to 103 feet (31 m), spending four hours per dive, and ascending with a quick release of the pressure to ambient (sea level) pressure. Modern reconstruction of Explorer's systems suggests an ascension rate of 1 foot per second (0.30 m/s); or a rise to the surface in just under two minutes. Even if it took longer to rise, decompression sickness would have been a factor. Using now-standard U.S. Navy diving tables, the men inside Explorer would have exceeded their no-decompression limit in 25 minutes at 103 feet (31 m). After a two hour dive (half of the documented time spent) a decompression schedule of one hour, 32 minutes and 40 seconds was required with staged stops at 30, 20, and 10 feet (9.1, 6.1, and 3.0 m). The problems of decompression do not appear to have been clearly understood; the contemporary reference notes that at the conclusion of the dives, "all the men were again down with fever; and, it being impossible to continue working with the same men for some time, it was decided, the experiment having proved a complete success, to lay the machine up in an adjacent cove....(The New York Times, August 29, 1869).

The basic premise of Sub Marine Explorer was based on an earlier 1858 patent by Van Buren Ryerson of New York for a diving bell also named "Sub Marine Explorer." Ryerson and Kroehl had worked together, Kroehl using Ryerson's bell to blast and partially clear Diamond Reef in New York harbor. Kroehl, working with Brooklyn shipbuilder Ariel Patterson, extensively modified Ryerson's design, extending the hull form to a 12 m-long (39 ft), 3.3 m-diameter (11 ft) craft of intricate design. While some have termed Kroehl's Sub Marine Explorer a "glorified diving bell," its sophisticated systems of ballast, pressurization and propulsion make it a nineteenth century antecedent to more modern "lock out" dive systems and subs.