a system engineering state—of—the—art equal to modern warship design

CAPT. M. ECKHART, JR., USN (RET.)

A SYSTEM ENGINEERING S TA TE-OF- THE-A R T E Q U A L

TO MODERN WARSHIP DESIGN THE AUTHOR

is currently Chief Scientist in the Autonetics Marine Systems Division, Rockwell International, concentrating in Digital Simulation Applications in System Engineering. A graduate of the U.S. NavalAcademy in 1945, he served in various surface assignments until 1950. Subsequent thereto, afrer being designated an Engineering Duty Officer (ED), he had Type Commander Stafl Laboratory, ESO, and Naval Shipyard assignments until 1962 when he became the Miltary Chairman, Electrical Science at the U.S. Naval Academy. In I965 he became the Head, Electrieal/Electronics Design Branch, Bureau of Ships, remaining in this assignment until 1967 when he assumed -the responsibilities of Director, Ship Concept Design Division, Naval Ship Engineering Center. Upon retiring from the U.S. Naval Service in 1970, he joined Rockewell International, and the following year became the Manager of the Integration Programs Group involved in Model-Based Systems Analysis. EM Effectiveness. Submarine Control. and Ship Data Miltiplexing. His education includes a BS degree fTom the U.S. Naval Academy; a BS degree in Electrical Engineering received from Massachusetts Institute of Technology in 1949; and a MS degree in Electrical Engineering received f iom The George Washington University in 1967. A former ASNE Council Member, he has been active in ASNE at both the National and Local Section levels since I96 7.

ABSTRACT

The general systems engineering state-of-the-art has not been equal to the functional diversity of modern mdti- mission warships, nor to the more complex system relationships that are characteristically involved in their design. Resultant dependence upon qualltative assessments of higher level relationships in warship definition and design has been and Is a critical impediment to the Navy’s corporate purposes, both in prosecutiog its vital rebuildlag campdgn and in dealing with the technological pace of naval warfare. A design methodology development, first reported on ASNE Day 74, has provided the bash for removing this impediment. The threshold criterion of system engineering, qaanti5cation, and correlation of total system design objectives, can be satislied for warship definition and design. Further, the basic elements of an exploitive system engineering practice have been developed sufRciently to c o n k their validity. This work is interpreted in terms of the system engineering structure that can be expected to emerge; first, because it can be done, and second, because its payoffi are so urgently needed by the Navy.

INTRODUCTION

A FUNDAMENTAL TURNING POINT I N WARSHIP DESIGN and the associated practice of naval engineering is at

hand. It is being enabled by a new system engineering state-of-the-art, one being developed explicitly for the warship application. System design issues that are imperatives of modern warship design both motivate and characterize this new state-of-the-art, and will cause its relatively rapid incorporation into general design practice.

Naval engineering practices are heavily conditioned by the idea that the complexity of multimission warships transcends the general systems engineering state- of-the-art. That is, it has been infeasible, if even possible, to quantify the top level sets of relationships that a) represent total warship design objectives; b) govern total system performance characteristics in the tactical environment; c) express relative worth of inter- dependent system characteristics and qualities; and d) involve the “trade-offs” between system performance and sue and cost.

Journal readers will readily identify the foregoing limitations with the critical ship definition and design problems of the 1%Os and 1970s. On the other hand, probably none can fully identify the degree to which these limitations have shaped naval engineering thinking and practices. Consider, for example, that while warships are our reason for being as a professional community, “warship design” is not common in our professional vernacular. Design objectives are identified with “ships”, “ship” systems, and Combat Systems. The reason, of course, is that each of these warship design subsets can operate below the foregoing limitations.

Systems engineering is typically described in terms of procedures, but its contribution to system design is governed by the extent of system relationships that can be quantified. A new system engineering state-of-the-art can now be said to be in sight because it has been established that quantzjkation of system relationships can be extended upward to total warship design objectives. Further, the analysis means have been sufficiently developed to confirm that interior relationships can be quantified so as to move, if not remove, the other limitations itemized above. Expanding upon these considerations, so as to identify the enlarged design framework that is being enabled, is the purpose of this paper.

The body of the work which provides the basis for this paper was initially described in three companion papers presented at ASNE Day 1974 [1][2][3]. The work, then in its formative stage, was reported in the context and scope of the conventional ship design process. Subsequent developments have served to

130 Naval Engineers Journal, April 1978

ECKHART NEW SYSTEM ENGINEERING STATE-OF-THE-ART

confirm the outline of the larger perspective of a new system engineering state-of-the-art, one that is equal to literal warship design realization.

PREMISE

SYSTEM RELATIONSHIPS CAN BE TREATED WITH AS- SURED VALIDITY BY SYSTEMS ANALYSTS AND SYSTEMS ENGINEERS ONLY IF THEY CAN BE QUANTIFIED TO ENGINEERING STANDARDS.

While the general systems engineering state-of-the-art has infused the spectrum of design activities involved in ship acquisition, it has not produced a coalescing to a total system discipline of the kind characteristic of the aerospace sources of the state-of-the-art. Trauma, caused by past efforts at instant remedy of ship acquisition management problems by transfer of aerospace form and method, without its substance, still invests our community. More importantly, fixation on form and method has deterred recognition of the technical keys to real substance.

Three absolute prerequisites can be identified from aerospace experience for evolution to a total system discipline:

Integral association of systems engineering with

Ability to quantify total system performance, char- system design.

acteristics, and cost “trade-offs.”

Identification of systems engineering with a “top- down” system specification discipline.

The same three prerequisites must be satisfied within the construct of ship acquisition if an equivalent total system discipline of warship design is to be attained. Figure 1 graphically associates the essential considerations.

Figure 1 reverses the classical sequence of analysis to synthesis, with the latter being the real design processes. System engineering, in the context of this paper, is the activity of closing the loops as diagramed.

The twojoops of Figure 1 must be integrally coupled and sustained concurrently. Detailed top-level “requirements”, as typically developed for ship acquisition, extend considerably into the scope of true “top-down’’ system specifications. Also, that which can logically be “required” is bounded by that which can be designed and specified.

As with all things connected with engineering, the key to Figure 1 is the ability to quantify all the design relationships involved in warship mission performance, i.e., the “analysis” bubble. This capability must invest the method of systems analysis with the rigor and depth of engineering. It is now established that the analysis methodology known as Model-Based System Analysis [2][3] can satisfy these criteria in the context of Figure 1.

Figure 1. Coupling Analysis to Design to close System Engineering Loops of Warship Definition, Design, and Specification.


NEW SYSTEM ENGINEERING STATE-OF-THE-ART ECKHART

TECHNICAL BASIS

ABILITY TO QUANTIFY SYSTEM RELATIONSHIPS THAT GOVERN WARSHIP DESIGN OBJECTIVES IS A DIRECT MEASURE OF NAVAL ENGINEERING EFFECTIVENESS.

Expressing net design objectives of a warship must start from direct measures of performance for all warfare missions. These measures will express dynamic properties, parameterized for tactical environment conditions, i.e., threat, force level interactions, and natural phenomena.

Design objectives must be directly relatable to design variables and system relationships that designers operate on. That is, sensitivities to those variables and relationships must be traceable to and quantifiable within mission performance measures.

The two foregoing criteria bracket the new system engineering state-of-the-art being enabled by Model- Based System Analysis (MBSA). The overall logic of MBSA is diagramed in Figure 2. An “image” of the design subject is simulated in tactical encounters designed to stress the ship image through its mission performance ranges, for its various operating modes. Being an image of the design is a literal requisite in two regards:

To be consistent with the organization of the design process and with the typical physical composition of warships so as to enable real time correlation with the design process. To be expandable with the design process as it de- velops greater depth and detail through the several

THREAT AND TACT1 C A L ENVIRONMENT PARAMETERS

NATURAL ENVIRONMENT PARAMETERS

TACTICAL ENCOUNTER

+

I SELF- STlMU LATE ENVIRONMENT (STRESS) OPERATING CONDITIONS

WARSHIP MODEL (IMAGE OF DESIGN)

PARAMETE RlZE D PARAMETRIC OPERABILITY SENSlTlVlTlES MEASURES *

OPERATIONAL RELIABILITY - SATURATION CONDITIONS - BREAKDOWN MECHANISMS

Figure 2. Logic of Model-B.eed System Analysis.

REACTION TIME MISS DISTANCE/ ACCURACY SATURATION

Figure 3. Mission Performance Memmres Matrix.

design stages. That is, traceability to mission performance measures can be established in concept and feasibility studies and be maintained through Preliminary, Contract, and Detail Design.

This image is realized through a family of models which are intended to have the potential for handling all ship types. This is proving valid in all applications to date. For further details in these respects readers are referred to References [2] and [3] which are still valid in their particulars.

A basic issue in MBSA development is what “measures” express warship performance for the various warfare missions, while being meaningful as quantitative design objectives. Most Journal readers are aware that “Measures of Effectiveness”, as developed through application of classical Systems Analysis to ship requirements problems, have not proved to be convertible into discrete and quantifiable design objectives. MBSA development has followed the opposite tack of devising the highest level performance measures that can be quantified, be parameterized VERSUS the condition variables of Figure 2, and be traceably factored to the designer framework. The generalized result is illustrated in Figure 3.

While -it is not immediately obvious, the several pri- mary warfare missions, e.g., AAW, can be expressed quite comprehensively by the three objective measures given in the left title column. The top title row is typical of the functional breakout commonly employed to define mission capabilities. Quantifying the inter- sections of this matrix provides the required con- vertibility between mission measures and design traceability. To distinguish warfare missions from other mission requirements and characteristics, the quantified relationships of this matrix have been termed “Combatant Capabilities” in MBSA development.

The objective measures must be interpreted in the broadest context. “Reaction Time” becomes a variety of functions of time, which has become the most critical parameter of modem warfare. “Miss Distance/ Accuracy’’ is related to the many engineering areas of error analysis and budgeting, not just weapon targeting. Saturation has to do with total system capacities, and it

132 Naval Englneers Journal, April 1978

ECKHART

REFERENCE MEASUREMENT TARGET

ATTITUDE REF

SYNCHRO IN INERTIAL TARGET TRANSMBSSON COORDINATES RANDOM

+ POSITION * b COMPUTATION b

NEW SYSTEM ENGINEERING STATE-OF-THE-ART

TARGET PREDICTION TARGET FILTER A N 0 PREDICTOR WIND +

AIR TEMPERATURE

includes such things as interior communication chan- nels, not just total measures such as simultaneous threat engagement capacities.

How individual mission matrices combine to form the net design objectives of a given multimission warship cannot yet be generalized satisfactorily, This depends upon the mix of missions, degree of use of common subsystems, level of automation, et cetera. Also. inter- mission dependencies due to mutual competition for limited design resources afforded by a given ship archi- tecture will typically become very influential.

One exceptionally critical competition for available design resources, for example, occurs topside in all modem surface warships: the resource being unenclosed volume. Over the last few years “topside design” has been added as a fundamental extension of ship design, and development of a comprehensive topside design logic is approaching a first generation operating form.

An example of how the quantification thresholds resulting from the above matrix drives MBSA development is illustrated in Figure 4. Ship motion in response to sea and wind forces induces error effects into all control operations, automatic or manual. In displace- ment ships it will usually cause operational ineffective- ness long before stability limits are reached. Ship motion effects on Combat Systems performance has been in the “too hard” category of naval engineering [41.

t A A MOTION * VIBRATION PRESSURE + SHIP VELOCITY IN IT IAL VELOCITY BIAS +

A N 0 RANDOM ERRORS LEVER A R M EFFECTS FLEXURE A N 0 VELOCITY

Figure 4 diagrams the first complete error propagation model for naval gun fire that treats total ship motion effects, with traceability to their effects components and their points of entry. Two broad findings immediately emerged:

BALLISTIC CALCULATION

Present surface ship motion theory and modeling is not sufficiently predictive of motion characteristics to satisfy the input requirements directly and rigor- ously. Thus explicit justification for needed ship motion research can now be developed. Intuition and empirical observation have not been reliable guides as to relative consequences of the various components of ship motion, e.g., pitch and heave may be much more degrading than roll.

Rigorous dynamic error analysis is prerequisite to assuring realization of dynamic performance measures at the higher levels of Figure 3. Ship motion produces the most complex array of errors in warships. Thus, Figure 4 provides a valid basis for generalizing to a generic error propagation model, the first generation of which has been developed.

Inability to trace vehicle (mobility) design parameters to worth margins in mission performance measures has been a significant impedance to conventional ship pro- graming, and has become the key to advanced ship programs. Reference [S] describes the situation colorfully.


CONTROL LOGIC CRITERIA BALANCE

-WEIGHT - - VOLUME OPERATING - 0 ENCLOSED POSITIONS

0 UNENCLOSED OEFlNlTlONS - ENERGY

r 1

A hydrofoil analysis has been conducted to test ability of MBSA methods to evaluate critical design parameters for the next generation hydrofoil, with results as follows:

BASE LINE SU BSY STE Ms - DEVELOPMENT SPEC1 F I CAT1 ONS

L d

An ASW mission potential that is uniquely related to hydrofoil characteristics can be demonstrated. Critical vehicle design parameters can be evaluated over potential design ranges VERSUS ASW mission measures. Key sensor design parameters can be correlated with mission and vehicle design parameters.

Not all missions are as strongly sensitive to vehicle characteristics as in this test case. Nevertheless, it is now confirmed that the simulation/modeling logic of Figure 2 is capable of removing the “too hard” label from this set of system relationships.

These sparse examples don’t tell much about MBSA, but they reveal something much more important, namely, that the problem solving bam’ers to rigorous warship design are coming down. Now we need to think in terms of how to overcome the divisions that have characterized the design approach to warships because of these barriers.

WARSHIP PRELIMINARY DESIGN

THE SYSTEM ENGINEERING LEVEL OF ANY SYSTEM IS ESSENTIALLY FIXED BY TEE END OF PRELIMINARY DESIGN.

Preliminary Design is the key to introduction of a new system engineering state-of-the-art for warship design. Overall allocations of available design resources are determined and mission performance potentials are bounded therein. Accordingly, realizing the major ad- vancement of warship design now being enabled can be related directly to design goals and thresholds established for Preliminary Design. Figure 5 illustrates the Author’s estimate of the minimum goals for the near future.

Performance definition is the common denominator of Figure 5. That is, the design context of Preliminary Design would be elevated from mechanical system relationships to performance characteristics that en- compass mechanical system aspects as well as mission payload aspects. “Metric” implies that mission performance measures will mature to design standards through the interaction of programmatic decision making and design confirmation. (All mechanical

I MISSION I

ARRANGEMENT

PROCESSING PERFORMANCE SPECIFICATIONS

OPE RATING

~

Figure 5. Warehip Preliminary Design Objectives.


ECKHART NEW SYSTEM ENGINEERING STATE-OF-THE-ART

system requirements, including those of the payload, are implied in the Zefi side of Figure 5.)

Warship design imperatives that dictate the minimum content of Figure 5 are at hand or in sight: Multiple platform tactical modes and inter-platform control: Exploitation of dramatic steps in warfare technology, such as laser devices and guided projectiles; Marriage of advanced ship with conventional ship concepts in future force compositions. All these and other advances imply alteration of performance and resource allocation relationships among the components of Figure 5 , and will depend upon investing preliminary designs with so- phisticated system engineering solutions.

In parallel with the above, design optimization within arbitrary limits will become even more imperative. To the well appreciated size/cost constraint will be added the much more complex one of manning. Future manning constraints will force a revolutionary change in warship design to make manning an independent design variable instead of the dependent variability that has been allowed heretofore. This will require an extremely demanding inversion of the design priorities within Figure 5 to make “Operating Positions Definitions” and “Operating Logic Definitions” the forcing functions throughout.

Two actions will transform Figure 5 from an array of design components (that exist implicitly) into a rigorous warship preliminary design construct:

Mutually relating all components in mission performance terms. Casually coupling “mechanical system characteristics” and “payload performance characteristics” through mutual constraint relationships, as indi- cated by heavy dashed arrows.

A third change of substantial impact will be involved in establishing concurrency among all the design components of Figure 5 during Preliminary Design.

ASSOCIATED SPECIFICATION REQUIREMENTS

WARSHIPS BECOME WHAT PASSES THROUGH THE HEADS OF DESIGNERS, INTO DEFINITIVE SPECIFICATION TERMS, AND THUSLY INTO THE HANDS OF PRODUCERS.

All of the foregoing arguments literally collapse into the issue of specifications. There is a very straight- forward yardstick of system engineering effectiveness. It is the rigor of the “top-down” specification discipline within which the system engineering activity operates.

Conversely, the most direct way to characterize con- temporary circumstances in point is to say that the major warship design issues fall outside the conventional specification envelope of ship acquisition. In this context, Figure 5 becomes the outline of a “top-down,’ warship specification to be established through Pre- liminary Design.

Quantification of system relationships, as discussed under “Technical Basis”, is given forceful point and purpose only by definitive specification goals. Returning

to Figure 4, and relating it to a recent Journal paper involving roll stabilization by DR. REWEN LEOPOLD [6] affords a good example. A central omission runs through DR. LEOPOLD’S account. The Technical Com- munity has never quantified the influence of roll motion on weapons control and other control processes so as to establish system specification thresholds that could not be satisfied without stabilization.

In fact, however, roll cannot be isolated in terms of ship motion effects on control processes. These processes are affected by the total of “6-degree-of- freedom” motion (as a rigid body) plus angular hull deflections (flexure), both directly and indirectly through corruption of sensor and reference inputs. However, we no longer need to partition the problem arbitrarily to have a tractable solution. Modern motion sensing and data processing technologies offer the al- ternative of incorporating compensation for all significant motion effects into the mechanizations of the affected control processes. It all depends upon rigor in quantifying performance requirements and thresholds, as in Figure 3. An essential condition that obtains is to rationalize specifications across all mechanization blocks and error components of Figure 4, with enough lead time to enable design responsiveness.

The lesson in point goes much deeper than failure of roll stabilization application, or ship design. In this case, lack of specification rigor can be traced to failure of research sponsorship for acquisition of basic knowledge on predicting ship motions.

Designers can design to “top-down’’ specifications, but producers can build only to “bottom-up” specifications. Aerospace can focus, apparently, on “top-down’* specifications because the decisive com- mitment is to full-scale Engineering Development, giving full scale verification of the production specification basis. That verification is not available in ship acquisition, of course. Thus the essential corrollary to “top-down” specification in Preliminary Design is the preservation of design traceability through the specification expansion stages of Contract and Detail Design, and not just for the ‘‘ship’’ specification, but for the total specification hierarchy evolving from Figure 5.

As modern warship complexity has begotten more complex analyses and design processes, a questipn commonly arising is: “How much is enough?” One definite part of the answer is what it takes to quantify warship performance metrics in a “top-down” specification and to provide traceability to all lower tier specifications.

TECHNICAL VISION AND REACH

The last 10 to 12 years have been difficult years for our profession because they have been difficult years for the ship side of the NAVY. Urgency in rebuilding the NAVY can be directly related to urgency in rebuilding naval engineering, from our perspective. From external perspectives, conversely, our only urgency is in being responsive to design imperatives associated with warships of the future. However, the most urgent of these

Naval Engineers Journal, April 1978 135


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ARLINGTON, VA. 22201 MARLTON PK. GREENLAND, N.H.03840 NORFOLK, VA. 23513 CHULA VISTA, CA. 920 (703) 527-7866 CHERRY HILL, N.J. 08034 (603) 436 -2068 ( 8 0 4 ) 853-7431 (714) 426-9538

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(609) 429-7050

imperatives involves system relationships that have been accepted as “too hard.” Thus thinking only in terms of doing the familiar [better, faster, and more often is a form of self-negation.

Much about the conventional approach to and ob- jectivizing of the total design spectrum of warship acquisition is a direct reflection of our past technical limitations in two respects: 1) quantifying the higher level system relationships of warships, and 2) translating them into quantitative “top-down” specification hier- archies. These limitations are no longer inescapable. Much hard and basic work must be done to remove them, but the technology for doing so is in sight, and the basic techniques are confirmed. The implications of overcoming these limitations go far beyond naval engineering per se.

While research is ideally directed towards basic knowledge, for too many years Department of Defense research has been limited to provable uses and available applications. Thus the above design limitations have been reflected broadly in corresponding limitations on research, as in the ship motion example. Since modem warfare is highly technology dependent, the arguments of this paper have a direct bearing on revitalizing ship- related R&D.

Engineering also serves a basic dependency in systems acquisition that goes beyond producing drawings and specifications. It provides acquisition process objectivity in the form of quantitative system relationships and process discipline in the form of quantitative specifications. These are the “authority” levers of engineering, and restoring naval engineering “authority” is a constant undercurrent in the professional dis-

courses of our Society. Given the high stresses of the budgetary crunch on the NAVY’S rebuilding purposes at the national political interface, and the business crunch at the shipbuilding industry interface, qualitative engineering arguments will have little leverage. On the other hand, these same stresses amplify the dependence on engineering for the elements of objectivity and discipline.

Finally, technical vision and reach need an objective forum in which ideas can meet and be tested. Thus ASNE has a vital service to naval engineering as our profession thinks and works its way through this turning point that is upon us.

REFERENCES King, Randolph W., RADM, USN, “Combatant Capabil- ity - A New Dimension in Ship Design,” Naval Engineers Journal, Vol. 86, No. 3 (June 1974) p. 33. Eckhart, Myron, Jr., CAFT, USN (Ret.), “The Rationale of Model-Based System Analysis for Combatant Capabil- ity Assessment,” Naval Engineers Journal, Vol. 86. No. 3 (June 1974) p. 40. Prout, Mrs. Frances M., CDR Robert C. Baker, USN, and Henry J. DeMattia, Jr., “Combatant Capability Assessment: Status in the Ship Design Process,” Naval Engineers Journal, Vol. 86. No. 3 (June 1974) p. 56. NAVSEA Seakeeping Workshop Report, “Seakeeping in the Ship Design Process,” July 1975. O’Neil, William D., “Advanced Naval Vehicles: Who Needs Them?”, SNAME Marine Technology (October 1977). Leopold. Dr. Reuven. “Innovation Adoption in Naval Ship Design,” Naval Engineers Journal, Vol. 89, No. 6 (December 1977) p. 35.

SPECIAL COMBAT SYSTEMS MEETING

NAVAL SURFACE WEAPONS CENTER, WHITE OAK LABORATORY SILVER SPRING, MARYLAND

a 9 NOVEMBER im

. * . . . . * * . + . * THE ASNE FLAGSHIP SECTION, with the Naval Surface Weapons Center as co-sponsor, currently has in the planning stages a 2-DAY SPECIAL MEETING devoted to technical presentations on “Combat System Design.”

A Security Classification of SECRET, with clearance requests to be handled via the Naval Surface Weapons Center, and a buffet/ social hour on Wednesday evening, 8 November, are contemplated.

MARK YOUR CALENDAR NOW!!! Keep these dates open and plan to be present for two days of sociability and informative technical sessions on combat systems.

MORE WILL FOLLOW LATER, with future announcements providing specific information regarding the program and the exact time and location of the meeting place.

1- SYSTEMS ENGINEERING ASSOCIATES


a system engineering state—of—the—art equal to modern warship design

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