he MK5 is a fully closed-circuit, computer-controlled, redundant portable life support system (PLSS) designed for extended range underwater work in hazardous environments. It provides a nominal depth-independent range of 10 hours operating time at depths up to 200 meters of seawater with remarkably easy work-of-breathing at all swimming attitudes (a result of computer optimization of the external counterlung).

It contains an extremely sophisticated multi-processor fault-tolerant computer system that not only actively controls breathing gas mixtures, but also computes real-time decompression for any combination of helium, oxygen, and nitrogen whether operated in closed, semi-closed, or open-circuit operation and whether operated in hyperbaric (underwater) or hypobaric (less pressure than sealevel) environments – in short, this same system could be used for an onboard decompression control and planning system for a spacesuit. It is the first and only underwater PLSS to employ a hydrophobic CO2 scrubber – which allows for underwater recovery in the inadvertent occurrence of a flood (through diver error).

It includes a head-up display, primary LCD computer display, “buddy lights” for warning a partner of your gas situation; audible oxygen level warning system; and a completely independent triplex redundant direct digital oxygen level monitoring system along with an elegantly compact manual bypass control system that also permits in-water connection of auxiliary gas supplies to the system (both oxygen and diluent) and user control of all gases from a one-hand operable panel.

The figure at left shows some of the unique features which make the MK5 the world’s most advanced and survivable PLSS, including:

• hydrophobic CO2 removal system allows the use of anhydrous lithium hydroxide (LiOH).
• one-hand operation 90-degree turn switches from closed-circuit to open-circuit abort.
• one-hand operable manual control block allows selection of onboard and offboard gas supplies; offboard supplies can be quick-connected during a mission. All gases can be directed to open-circuit abort breathing.
• three onboard computers - voting logic allows for over-ride of failed sub-systems and continuance of the mission.
• real-time PO2 validation during a mission.
• completely independent digital PO2 display for all three onboard O2 sensors.
• head-up display for hands-off oxygen and decompression management.
• onboard “black box” records all mission data. A sophisticated post-processor permits review and plotting of this data as well as provides input to future mission management (taking into account surface interval time and onboard stored tissue tensions).

The performance of the MK5 is legendary and it has been used on some of the most commiting underwater exploration and science missions ever undertaken. The images on the previous page show some of the extraordinary capabilities of the MK5. Clockwise, beginning at the upper left: real-time download of decompression tissue tensions, allowing for transition from in-water decompression to chamber-based decompression; transferring the crew to a pressurized habitat while decompression information is being downloaded; the crew arrives and changes out to dry clothing; digital data dump of primary oxygen tank pressure (there were two such tanks on each mission); digital data dump of oxygen partial pressure during the mission; digital data dump of depth versus time showing the five (5) hour bottom time at depths ranging from 280 to 300 feet underwater followed by 3-1/2 hours of in-water decompression prior to transfer capsule lock in.

The basic MK5 architecture is modular and lends itself to custom designs, including fully redundant closed-cycle PLSS systems as shown below. This is a 20 hour range, 200 meter operating depth, twin closed cycle MK5 with full consumables cross-routing capability (including both supply gases and CO2 scrubbing cross-over via in-line hose quick connects). The system is shown at lower right being used with two Cis-Lunar Fat Man 20 kilometer range propulsion vehicles.

The MK5 has an optional, and extensive, planning, simulation, data download and plotting package for mission planning and post-mission review. Images on the following page, clockwise from bottom right include post-dive statistics; full mission simulation (including on-the-fly decompression), and mission planner. The MK5 comes with an optional serial data download cable that can be attached in the field to any Windows laptop computer (custom versions will be written on spec for Linux and Mac interfaces).

Acquisition Information: the MK5 can be produced in minimum production lots of 200 following the original design shown here or with upgraded electronics, power, and laptop interface systems. Customer-specified variations are also possible.

Export Information: the present (standard) MK5 design is intended for high-end recreational and scientific diving. It is not a military device. Military versions can be developed on spec but will require ITAR license surcharge and larger production lot minimums.

Spacesuit PLSS: the core components of the MK5 can be readily adapted for use as a COTS industrial spacesuit PLSS, including fully redundant long range versions for sustained, remote, survivable EVA.

Contact us for pricing and lead time.