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A number of specialized diving activities are used in the NBRF to achieve test objectives. When unique dive operations are required, it is expected that specific procedures will be created, reviewed, and approved by the NBRF Facility Director prior to initial operations.
There are times when it is useful to have non-dive rated personnel snorkeling in the NBRF to observe test operations. When this is necessary in conjunction with a normal test operation, the deck chief and lead diver must approve and monitor the free-swimming personnel. Specific limitations of NBRF snorkeling include:
The vacuum system at the NBRF is a siphon-based system that provides approximately 8 pounds/square inch pressure differential. Standard pool vacuum hoses with specialized end fittings are used for cleaning interior tank surfaces. Vacuum system users shall be briefed on the proper use of the vacuum system, with specific attention to the danger of minor edema if the vacuum hose is allowed to seal against the skin for a significant period of time. Users will also be briefed on the correct use of the vacuum system valves, which ensure that the tank does not drain following a filtration system failure.
Emplacement of test hardware in the NBRF requires the use of standard lift bags to offset the weight of the units. Prior to the first use of lift bags, an NBRF diver shall receive a predive briefing on the correct use of lift bags, including the use of regulators to fill, nominal configuration of attachment straps, and the operation of spill valves. New users shall use lift bags in non-complex tasks (single bag, simple payload configuration) under close supervision for both descent and lift until they demonstrate basic competency at buoyancy control. Except in unique circumstances with prior approval by the NBRF Facilities Director, non-SSL divers will not be approved for the use of lift bags.
The SSL maintains a number of pneumatically-driven power tools (such as hand drills) for use when hardware modifications must be made underwater. Dive personnel shall be briefed prior to use of the power tools on correct techniques, including safety issues, reaction torque control, dealing with the large volume of bubbles generated by the pneumatic system, and the use of the vacuum system to clear waste particles from the tank. Air-powered tools shall be connected by appropriate hoses to the NBRF shop air system (limited to 80 pounds/square inch), and shall not be connected to any breathing air system. Except in unique circumstances with prior approval by the NBRF Facilities Director, non-SSL divers will not be approved for the use of air-powered tools underwater.
Dive operations requiring large numbers of divers require special attention to safety. Specific attention during the pre-dive briefings will be paid to the mechanics of maintaining order during test operations with large dive teams. One diver will be dedicated to safety monitoring for each four divers involved in test operations. The lead diver is considered to be a safety diver for the purposes of this section. Therefore, if more than five divers are in the water, a second safety diver will be incorporated in the test operation for dive crews of total size between 6 and 10 people. For the purposes of this Section, the safety diver must be an experienced NBRF diver with deck chief certification. If the test has other safety implications beyond the size of the dive team, the Facilities Director may require safety divers to hold lead diver certification. Although it is not anticipated that there will ever be a test requiring more than 10 divers, a third safety diver would be added for total crew sizes between 11 and 15, and so forth.
Due to the presence and involvement of teaching personnel in the training classes, dive operations in support of training are exempt from the formal requirements of this section.
Receive-only DiveComm requires a receiver unit mounted on the air tank and dual bone-conduction speakers mounted on the headband of the face mask. New users of this system will be briefed by experienced personnel prior to the dive, including the importance of ensuring positive restraint of the receiver unit, awareness of the potential for snagging hazards with the receiver hydrophone, proper mounting and use of the bone conduction speakers, and safe breathing practices when listening to a transmission.
The Space Systems Laboratory currently uses a DiveComm communications system in an AGA full face mask for tests requiring two-way communications with one or more divers. The DiveComm itself requires the same briefing as detailed in Section 6.4, with additional briefing on tips of how to speak so as to be understood on the surface:
Divers using the AGA full-face mask must complete a session of in-water training, taught by the NBRF Facility Director or his/her delegated instructor. Pre-dive briefings will focus on the construction and theory of the AGA mask, including positive pressurization for face sealing and the regulator cutout lever for ingress/egress. Trainees will put on and breath from the mask on the surface, and practice handling the cutout lever for controlling free-flow. In-water training will focue on flooding and clearing the mask using the cutout lever. Trainees will donn and doff the mask while sitting on the diver entry platform, flooding the mask, clearing it, and tightening the straps to correctly fix the mask and stop peripheral leakage. When the trainee demonstrates routine competence at shallow depth, the donn/doff demonstration will be repeated at depth in the NBRF. Following successful completion of the mask training, the trainee will swim around the NBRF under the close supervision of the trainer, getting familiar with the effects of the AGA mask such as excess buoyancy and orientation-specific peripheral leakage, and practice two-way communications with the DiveComm system.
Diving operations detailed in subsequent subsections of this Section of the NBRF Diving Safety Manual involve significant restrictions of normal diver capabilities, and as such require a dedicated safety diver. Safety divers shall wear octopus regulators for sharing air supplies in contingency situations, and shall be positioned underwater such that they are within three seconds of full physical access to the test subject. Safety divers shall have no other test responsibilities other than the safety of the test subject. Test operations including subsequent unique dive operations shall have a full formal briefing before each test, with specific instructions to the safety divers, including establishment of hand signals for both normal operations and contingencies. Safety divers shall be selected from the more experienced of NBRF divers, and shall be specifically approved by the NBRF Facility Director as part of the process of approving test plans.
A number of scientific objectives for SSL research operations require replication of human body configurations in microgravity. These tests, such as body dynamics and postural maintenance tests, cannot be performed with a body-mounted air supply. These tests are performed with a "hookah" rig, wherein the second stage of a standard regulator is connected to the first stage through a 20 ft. pressure hose. The regulator hose shall be connected to the user's body to provide both strain relief and positive retention. The user will also wear a body-mounted emergency breathing system, capable of supported normal breathing during egress from the experimental apparatus and nominal ascent to the surface. The test subject shall be briefed on the use of the hookah prior to test operations. Test subjects must either transition to the hookah on the surface, or underwater prior to doffing conventional scuba tank and regulator assembly (i.e., no free dives to/from the hookah regulator.)
Hookah operations require the presence of a dedicated safety diver as per Section 6.9.
A number of objectives for SSL research operations require the use of IVA/EVA foot restraints, or other body restraint systems. These restraint systems shall be designed so as to not entrap divers, and shall be capable of contingency egress within 30 seconds. At least two options shall be provided for test subject egress from a restraint. (For example, egress from EVA foot restraints could be performed either by removing the boots from the restraint, or by the subject removing their feet from the boots.) In cases where the restraints cannot meet both of the prior requirements, a means shall be provided for removing the subject from the tank while wearing the restraints.
Restraint systems require the presence of a dedicated safety diver as per Section 6.9.
SSL research requires the use of space suits and space suit simulators, such as the Maryland Advanced Research/Simulation (MARS) Suit. Suited operations are highly complex and specialized operations, and shall be performed in compliance with specific Space Systems Laboratory Operating Procedures documents for each type of suit.
Space suit operations require the presence of two dedicated safety divers for each suit. Suit safety divers shall initially meet the requirements of Section 6.9, and shall receive specific training on suit systems, suit dive support procedures, and contingency procedures prior to suit test operations.