Third Tank
Welding of the new tank took place in October and November of 1967, after which a 40 feet (12 m) deep, 75 feet (23 m) diameter pool was nearly ready. Remaining work, according to Kuers' November 20th report, included installation of a "two-ton hoist, a breathing air system, a scuba cylinder filling system, a new recompression chamber, the installation of the instrumentation in a trailer to be located between Buildings 4706 and 4705, the procurement and the installation of a diving bell and airlock and the design, procurement and installation of an elevator to operate between ground floor and the upper platform and to be used for the movement of both people and equipment."
Final preparations for testing took several more months. Engineers elected to fill the tank slowly to be able to repair any leaks found along the way, and they filled it, finding and fixing a few leaks, between February 29 and March 11, 1968. Thus readied, workers began installing test equipment. Workers had to develop new techniques to assemble parts underwater because of the low clearance between the top of the tank and the enclosing building's roof.
With the prospect of astronauts diving in pressure suits, the Manned Spacecraft Center (now Johnson Space Center), introduced a new level of safety to MSFC in the form of an Operational Readiness Inspection (ORI) committee which evaluated the facility for safety concerns. The committee was formed in December 1967. They carried out inspections and oversaw exercises to demonstrate readiness for a variety of contingencies. After nearly a year of a full tank, the procedures were ready for suited astronauts.
The first suited astronaut dive in the new tank was an exercise to develop Apollo Telescope Mount film retrieval techniques. Paul Weitz and Joseph Kerwin donned Apollo A5L suits (predecessor to the Apollo/Skylab A7L) and practiced film retrieval by both parallel rails and the trolley system while Edward Gibson observed in scuba gear on March 4, 1969. Their experiences led to a tether restraint system, heat exchanger in the space suit air supply, adjusting the umbilical so that it was neutrally buoyant, tweaks to the weighting system for the A5L suit, and a new foot restraint design.
With the addition of trailers for control and dressing rooms between buildings 4705 and 4706, the combination became referred to as building 4705.
Read more about this topic: Neutral Buoyancy Simulator