The Design of a One Atmosphere Submersible/Diving System
Authors: McFarlane James R. , MacDonald Michael D. 
Published: October 2008

There is no universal underwater work system. Therefore, the oil patch is populated by a variety of systems and equipments with unique and/or complementary capabilities. Over the last half decade, a number of so-called one atmosphere systems have evolved to round out the underwater work package. These include JIM, WASP, MANTIS, and more recently, WRANGLER. However, for the most part, these vehicles do not, in the writer's opinion, represent new notions. For example, there was considerable early work done by Kuhnke and Galeazzi. Additionally, NEKTON, which has been around since 1968, is comparable in size to MANTIS and WRANGLER. It is thus suggested that so-called one atmosphere diving systems are not a new concept. They are, in fact, the lower terminus of so called manned submersible designs. The newness is, in reality, vested in the technological refinement of component elements and the finesse in systems integration which comes with experience gained. This is common to all forms of technological evolution. One such vehicle refinement is the WRANGLER.

WRANGLER, which is a manned or remotely controlled vehicle, is thus the offspring of two species. It is, therefore, by definition, an hybrid vehicle which represents yet another element of the underwater work suite. The matrix shown in Table I illustrates where WRANGLER fits into the various vehicle types.

The remainder of this paper will review the rationale for some of the decisions made re the establishment of overall characteristics and definition of various WRANGLER subsystems. The salient premise was that the new vehicle should have characteristics which were substantially different from other one atmosphere systems, so that it would not have to compete with those concepts, but would rather offer another work suite capability. An analysis of the tasks which JIM, MANTIS, and WASP had accomplished effectively indicated a marketable opportunity for a vehicle which had:More pilot spaceGreater mobility, maneuverabilityMore enduranceHybrid control, andMore manipulative capability Each of the aforementioned requirements' impacts on vehicle size and/or cost, as well as the technical expertise required of the users. Clearly, the effects of these requirements are not favorable under all operational scenarios. For example, more pilot space increases the vehicle size and hence handling weight. Having a sophisticated control system is also not without drawbacks. Thus, as is always the case in systems synthesis, there are many tradeoffs made on the way to achieving, what would appear to be in the eyes of the designer, an harmonious union of the parts which will meet the stated capability.

When one commences the system design of anything which cannot be uniquely defined, starting point must be selected and a design iteration will commence from this point. Successive iterations will take place until convergence is reached, which may not, in a multi-variety situation, be path independent. This iterative procedure is the so-called "design spiral" technique, which one finds in many of the papers written by Prof. J. Harvey Evans. To use this technique, the vehicle must be subdivided into functional subsystems and elements.