A series of unmanned trial emplacements and recoveries were made at Lameshur 

 Bay to determine the correct amount and placement of ballast and the proper 

 procedure for flooding and dewatering the pontoons of the catamaran during 

 emplacement and recovery. 



The system proved to be unstable because of a shift between the center of 

 gravity and the center of buoyancy when passing through the air/water interface. 

 The instability resulted in an uncontrolled heeling over of the pressure vessel 

 until its buoyancy took effect. This generally resulted in the pressure vessel 

 assuming a 45 degree angle at either one of four quarters . The heeling motion 

 did not constitute a severe problem because a correct attitude could be estab- 

 lished soon after it occurred by additional flooding of the pontoons. It did 

 appear ungainly, however. 



To remedy the situation, the emplacement procedures were changed. The new pro- 

 cedure involved flooding of the forward end compartments to establish a positive 

 down angle, followed by a sequential partial flooding of the center and after 

 end compartments . This procedure worked well and allowed the minitat to level 

 out with only the top of the pressure vessel above water prior to winching down 

 operations. Figures 12 and 13 show the minitat descending through the inter- 

 face and in a stable altitude after leveling out. 



When the minitat is in a level attitude, with only about two feet of the pres- 

 sure vessel above water the haul down procedure is started. Two hand winches 

 having a 3,300 pound capacity are attached between bridles from the two forward 

 comers and the two after corners of the habitat and hauldown cables connected 

 to two 4,000 pound clumps on the bottom. When the structure is a few feet off 

 the bottom, final flooding of the pontoons allows it to settle to the bottom. 



During the shallow water trials it became apparent that the flooding and vent- 

 ing sequence during emplacement and recovery was not in conformity with previous 

 calculations. Each pontoon had been divided into three separate compartments 

 in order to eliminate much of the free-surface effect of sea water in the 

 35-foot long cylinders. Upon cutting into the pontoons it was discovered that 

 the transverse bulkheads were improperly welded, permitting free exchange of 

 sea water ballast and internal pressures between compartments. The steel bulk- 

 heads were repaired and emplacement procedures modified to prevent excessive 

 pressure differentials which might rupture the bulkheads again. Following these 

 repairs the minitat was emplaced in shallow water for further trials in a manned 

 mode. The trials were carried out at a depth of 20 feet so that diver decom- 

 pression would not be required. 



After all systems were functional the minitat was occupied by two man teams 

 rotated in eight hour shifts. This procedure accelerated the usage of the sys- 

 tems compared to occupancy by a single team of men who would have to sleep and 

 rest about half the time. All systems were tested including the emergency 

 systems. Meals were cooked, pliombing and life support equipment operated, 

 scrubber canisters changed, and sleeping facilities tried out. Several minor 

 modifications were made in the course of this manned all systems checkout. 



The PTC and DDC were also exercised at this time to reveal any hardware or 

 procedural difficulty. A team of two divers entered the PTC which was about 

 10 feet below the surface. The PTC was lifted aboard using the ships boom and 

 mated to the DDC. A 5 hour simulated emergency decompression was carried out 



III-13 



