An atmospheric diving suit (ADS) is a small one-person articulated submersible which resembles a suit of armour, with elaborate pressure joints to allow articulation while maintaining an internal pressure of one atmosphere. An ADS can enable diving at depths of up to for many hours by eliminating the majority of significant physiological dangers associated with deep diving. The occupant of an ADS does not need to decompress, and there is no need for special breathing gas mixtures, so there is little danger of decompression sickness or nitrogen narcosis when the ADS is functioning properly. An ADS can permit less skilled swimmers to complete deep dives, albeit at the expense of dexterity.
Atmospheric diving suits in current use include the Newtsuit, Exosuit, Hardsuit and the WASP, all of which are self-contained hard suits that incorporate propulsion units. The Hardsuit is constructed from cast aluminum (forged aluminum in a version constructed for the US Navy for submarine rescue); the upper hull is made from cast aluminum, while the bottom dome is machined aluminum. The WASP is of glass-reinforced plastic (GRP) body tube construction.
Definition and classification
An atmospheric diving suit is a small one-person submersible with articulated limbs encasing the diver. Water- and pressure-tight joints allow articulation while maintaining an internal pressure of approximately one atmosphere. Mobility may be through thrusters for mid-water operation, though this is not a requirement, and articulated legs may be provided for walking on the substrate.
Thornton (2000) distinguishes an ADS from a submersible in that the ADS has human powered articulated limbs, as opposed to remotely operated articulated limbs. It is not clear whether this would exclude servo-assisted limbs encasing those of the operator, as a powered exoskeleton, but it might be reasonable to include them as atmospheric diving suits.
An atmospheric diving suit may be classified as a manned submersible and a self-propelled, manned, one-atmosphere underwater intervention device, but has also been classified as an atmospheric diving system.
Purpose and requirements
The underwater environment exerts major physiological stresses on the diver, which increase with depth, and appear to impose an absolute limit to diving depth at ambient pressure. An atmospheric diving suit is a small submersible with a pressure hull which accommodates a single occupant at an internal pressure of about one atmosphere. The provision of hollow arm spaces with pressure resistant joints to carry manually operated manipulators, and usually separate leg spaces, similarly articulated for locomotion, makes a suit resemble a bulky suit of plate armour, or an exoskeleton , with elaborate joint seals to allow articulation while maintaining internal pressure.
An atmospheric diving suit is equipment intended primarily to isolate the occupant from the ambient pressure of the underwater environment, and provide any necessary life-support while the suit is in use. While using the suit, the diver will expect to perform useful work, and get to and from the place where the work is to be done. These functions require sufficient mobility, dexterity and sensory input to do the job, and this will vary depending on the details of the work. Consequently, the work possible in an atmospheric suit is limited by the suit construction.
Mobility at the surface and on deck can be managed by launch and recovery systems, Mobility underwater generally requires neutral or moderately negative buoyancy, and either the ability to walk or swim, or the use of finely controllable thrusters. Both walking and thruster propulsion have been applied with some success. Swimming has not been effective.
The dexterity to perform useful work is limited by joint mobility and geometry, inertia, and friction, and has been one of the more difficult engineering challenges. Haptic perception through manipulators is a major limitation on finer control, as the friction of the joints and seals greatly reduces the sensitivity available.
Operator visual input is relatively easy to provide directly by using transparent viewports. A wide field of view can be achieved simply and structurally effectively by using a transparent partial dome over the diver's head. Close-up views of the manipulators are limited by joint flexibility and geometry of the suit's arms. External sound and temperature perception are greatly attenuated, and there is no sense of touch through the suit. Communications must be provided by technology, as there is normally no-one else in the immediate vicinity.