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EVALUATION AND SELECTION OF TECHNOLOGY CONCEPTS FOR A HYPERSONIC HIGH SPEEDSTANDOFF MISSILE

Dr. Bryce Roth* and Prof. Dimitri Mavris✝

Georgia Institute of TechnologyAtlanta, GA 30332-0150

Abstract*† This paper describes the application of a method for

technology concept selection to the design of ahypersonic high-speed standoff missile capable ofachieving pin-point strike of long-range targets with veryshort dwell times, such as mobile missile launchers. Theprimary strengths of this method are its ability tosystematically enumerate and organize a wide variety ofdesign alternatives in a simple and elegant manner, andits ability to facilitate concept selection for multi-attributeproblems. The high-speed standoff missile is used as amodel for application of this technique due to the multi-attribute nature of the problem and the stringent nature ofthe requirements. These requirements include a 1,500 lblaunch weight, 500 nmi range, less than 10 minute time totarget, and a unit cost of less than $300,000. The firststep in this process was to assemble a set of configurationand technology options for consideration. From these, aset of eight concepts were synthesized, evaluated, anddown-selected to two alternatives: an advanced solidrocket concept, and a ramjet concept. These two designswere evaluated in detail for cost, performance, lethality,and effectiveness. The results were then used inconjunction with the TOPSIS multi-attribute evaluationtechnique to make a final selection.

Introduction One need only review recent and current world

events to realize that today’s political climate is in someways more unstable and uncertain than it has been in thepast, particularly with the end of the cold war and thedisintegration of the Soviet Union. The cold war was astruggle against a monolithic adversary whose boundariesand capabilities were reasonably well defined. No longerdoes the United States face the unified force of the oldSoviet Union and its Eastern Bloc allies. The newadversaries are more numerous and elusive because theylie scattered among several smaller, independent nationsand even factions within nations. In addition, theproliferation of mobile Weapons of Mass Destruction andother offensive weapons amongst numerous smaller * Research Engineer, Aerospace Systems Design Laboratory (ASDL),School of Aerospace, Georgia Tech. Member, AIAA.† Assistant Professor, Department of Aerospace Engineering, andDirector, ASDL. Senior Member, AIAA.Copyright © 2000 by Bryce Roth. Published by the Defense TechnicalInformation Center, with permission. Presented at 2000 MissileSciences Conference, Monterey, CA.DISTRIBUTION STATEMENT: Approved for public release;distribution is unlimited.

countries is making it increasingly difficult to protectfriendly assets against attack from theater-range mobileweapons.

This basic difficulty is further compounded bypresent Western military doctrine, which calls for a long-term aerial campaign in response to these threats, andgenerally downplays the use of ground forces in mostsituations. Since there are no ground forces controllingthe terrain, the adversary is free to hide assets incamouflaged revetments until they are ready to be used.If it is a mobile asset, it is a simple matter to drive theweapon to a suitable launch site, set up, launch, anddepart the area before allied forces have sufficient time torespond. This is especially the case when there is a vastamount of territory that must be patrolled in order to be“in the right place, at the right time.” The recentengagements in Iraq (Operations Desert Storm and DesertFox) and Kosovo (Operation Allied Force) punctuate thispoint.

As a consequence of this doctrine, there is currentlyinsufficient capability to respond to targets that are highlymobile or otherwise difficult to locate. For example,surface-to-air missile (SAM) launchers and mobiletheatre ballistic missiles typically have dwell times ofunder 10 minutes.1 That is, these time-critical targets(TCT) may appear suddenly, or move location rapidly.The subsonic flight speeds of the current arsenal limit thetimeliness of aerial responses to TCTs. As a result,today’s response capability is becoming increasinglyinsufficient to meet the demands of tomorrow’sbattlefield.

This situation is prompting military planners todevelop a credible military capability to respond to thisthreat. One approach to solve this problem is to use aHigh-Speed Standoff Missile (HSSM).1 Such a weapon,capable of hypersonic speeds, would provide a forcestructure with the rapid reaction capability needed toaccurately eliminate the TCT threat. Furthermore, withsufficient range, allied aircraft could launch this missilesafely beyond the threat range of SAMs. In addition, ifsuch a weapon were equipped with a modern multi-purpose warhead, it would greatly increase the utility andflexibility of allied response capability by allowing theweapon to be employed against a variety of targets.

This weapon alone will not meet the needs of therapid response capability, and must instead be designedas part of a larger system architecture. This architecturemust include a synergistic, real-time information andtargeting environment within which the HSSM would

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operate. Thus, the concepts developed and discussed inthis paper are based on a postulated 2010 capability foran advanced command, control, communication,computers, intelligence, surveillance, reconnaissance(C4ISR) network.1 The C4ISR architecture is assumed tocombine ground stations, satellite sensors relays, andunmanned air vehicle sensors to provide the launchaircraft with a sensor-to-shooter connectivity time ofunder 2 minutes. In addition, the C4ISR environment isassumed to offer targeting information accurate to withinthree meters (sufficient for an advanced GPS/INSguidance system aboard the HSSM to achieve high targetaccuracy, on the order of three meters circular errorprobable.)

Finally, a successful HSSM program must performwith minimum possible cost. As a result, the designconcepts described in this paper place a great deal ofemphasis on simplicity of design and avoidance of exoticmaterials and processes. It has been estimated that inorder for an HSSM system to be truly practical, areduction of more than 50% over current missile costs isneeded. A sufficiently low unit cost would allow the useof HSSM in place of much more costly cruise missilessuch as the conventional air-launched cruise missile(CALCM), which has a unit price of approximately $1million.1,2

The design of a missile airframe capable of meetingthese requirements presents several challenges. First, thestringent nature of the HSSM design requirementsimplies that any successful HSSM design must capitalizeon a considerable number of new technologies.Fortunately, there is an abundance of promisingtechnologies that have been proposed for use on a HSSMconcept, particularly with regards to propulsiontechnologies. Consequently, there is an almostbewildering array of potential design solutions, certainlymore than can be evaluated within the resources of anyreasonable research and development effort. Therefore,the design of an HSSM missile presents a challenge withregards to how to best go about systematicallyenumerating and evaluating the multitudinous technologyconcepts such that a handful of the most promisingconcepts are identified for further evaluation.

Second, the HSSM is inherently a multi-objectiveproblem wherein the merit of the design is measured by amultitude of metrics including lethality, performance,system effectiveness, etc. Therefore, any evaluationmethod must be capable of treating multi-criterionproblems in a consistent and comprehensive way. Thishas historically been a stumbling block in conceptevaluation due to the trend towards promulgating moredesign figures of merit (FoMs) with each successivegeneration of missile technology. Fortunately, a greatdeal of work is currently taking place in the field ofmulti-criterion decision-making methods. The missile

concept selection problem stands to benefit from theapplication of these new methods.

The objective of this paper is to describe atechnology concept selection method having uniquefeatures that facilitate systematic selection and evaluationof missile technology concepts subject to multiplecriteria. This method is demonstrated for the design of anHSSM missile from initial conceptual exploration topreliminary design down-select. The designrequirements are discussed in detail, and a matrix ofsuitable HSSM technology concepts is developed. Fromthis initial pool of technologies, a set of eightconfigurations is selected for conceptual-level designdevelopment. These are then down-selected to twodesigns, one solid rocket-powered, and the other poweredby a ramjet. Finally, these two design alternatives areevaluated for performance, cost, and lethality with the aidof multi-attribute decision-making techniques.

Approach - TIES Method One of the major tasks in the conceptual design

process is evaluation of numerous alternative concepts ona qualitative basis, before selecting a subset of baselinedesigns for further development. This process ofalternatives synthesis and evaluation presents aconsiderable challenge because most of the applicableconcepts involve new or untried technology for whichthere is little or no experience base upon which to drawfor guidance in choosing the most promising designmorphology. The number of possibleconfiguration/technology combinations is usuallyastronomical, and as modern systems increase incomplexity, the number of possible design optionsincreases exponentially. Consequently, there is a needfor methods that can assist the designer in organizing andsynthesizing various alternatives to pare down the designpossibilities to a tractable number that can be evaluated ata reasonable depth of analysis.

The approach used to solve this problem was toadapt methods originating in the field of decision theoryfor use in the aerospace systems design process. Thesetechniques have been developed over the course ofseveral years into a comprehensive systems designmethod known as Technology Impact Evaluation andSelection (TIES) Method. TIES is in fact a purpose-builtdesign method developed at the Georgia Tech AerospaceSystems Design Laboratory (ASDL) specifically to aid thedesigner in selection of technology alternatives. Thus, itsapplication herein is a natural extension of its originalpurpose, and it was used to great effect for exploringHSSM technology and configuration options. Inaddition, the systematic approach allows one to focus inon a few promising configurations in very short order.Although TIES is a general method, only a subset ofthose elements germane to the analysis conducted hereinare discussed in detail. A comprehensive description ofthe TIES method is given in references 3 and 4.

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The basic design method used for this study isdepicted in the form of a flowchart shown in Figure 1.The first step is definition of the problem in terms ofspecific objectives and constraints. Based on this, onecan develop a morphological matrix, which is a matrixthat explicitly lists all of the major design andconfiguration alternatives in a simple format. The majordesign attributes are listed in the left column, and thepossibilities for each attribute are enumerated in a row tothe right of the attribute column. Once this matrix iscreated, one can easily generate alternative designconcepts by simply selecting an option from each row,with each complete set of options defining a singleconfiguration. This is best done through a series of free-form brainstorming sessions involving a small team ofexperienced designers.

Once a satisfactory set of design alternatives hasbeen developed, they are next placed in a matrix ofcriteria versus concepts, known as a Pugh matrix. ThePugh matrix is nothing more than a systematic way ofshowing the alternative concepts side-by-side in a simpleformat. Therefore, the Pugh matrix is a tool forsummarizing and comparing the attributes of alternativeconfigurations against each other and against the RFPrequirements. Its primary purpose in this study is toassist in the qualitative down-select from a broad pool ofalternatives to a “short list” of design concepts to bestudied using detailed analytical methods.

Next, the alternatives remaining on the “short list”must be evaluated via modeling and simulation todetermine system attributes and performance. The resultof this process is a set of disparate performance figures ofmerit that must somehow be combined into a singlefigure of merit to arrive at a winning designconfiguration. What is needed is some systematic meansof weighting the importance of the various performanceattributes such that they can be compared on an “apples-to-apples” basis.

The tool used for this task is known as the Techniquefor Order Preference by Similarity to Ideal Solution, orTOPSIS. This decision-making tool works by rankingthe various baseline systems in terms of their fulfillmentof the goals and constraints. Different scenarios areaddressed by subjectively weighting key system

attributes. The results are normalized against a datum (or“perfect design”) and a score can then be calculated foreach baseline system, per scenario.

The approach used in this study was to synthesize aset of eight alternative concepts from the morphologicalmatrix, all of which were placed in a Pugh matrix. Next,these alternatives were evaluated on a qualitative basis,and from there down-selected to a single solid rocket anda single air-breathing design for detailed analysis. Thesetwo designs were then evaluated side-by-side usingmodeling and simulation in conjunction with TOPSIS toarrive at a final design recommendation for which adetailed technology development plan can be formulated.

Step 1: Definition of HSSM Requirements

The assumed HSSM design requirements used in thispaper are based on a set of notional requirementsformulated by the American Institute of Aeronautics andAstronautics Missile Systems Technical Committee(MSTC) calling for a weapon with the ability to respondto time-critical targets. This notional request forproposals (RFP) dated 8/3/98 calls for the design of anHSSM weapon that shall be capable of launch from an F-18C, and travel to its target at hypersonic velocities. It isdesigned to operate in the year 2010, and thus embodytechnologies producible and operable by this time. Theprimary targets of this weapon include, but are notlimited to: 1) mobile ballistic missile launchers (TCT), 2)surface-to-air missile launchers (TCT), 3) command,control, communications sites, 4) storage, supply depotsfor weapons of mass destruction, 5) other targets of

Step 1: Problem Definition•Requirements•Evaluation Criteria

Step 2: Morphological MatrixIdentification and Synthesis ofAlternatives

Step 3: Initial Down-SelectEnumeration of Alternatives inPugh Matrix

Baseline Designs•Air-Breathing•Solid Rocket

Step 4: Modeling & Simulat.•Design Analysis•Performance Estimates

Step 5: TOPSIS EvaluationAnalysis-Based Design Down-Select

Figure 1: HSSM Design Method Overview

Table 1: HSSM Metrics and ConstraintsAttribute Metric RFPPerf. Peak Flight Mach >5

(min. time) Flight Time, sec. <600a

Range, nmi >500b

Lethality Warhead Weight, lbs >150(brd. Tgt.) Impact Velocity, fps >4,000

Penetration Depth, ft. >20c

Off-Boresight, deg. >20Lethality Surface Kill Radius, ft. >150(sfc. Tgt.) Off-Boresight, deg. >20

Cost ACQ Cost, $1000’s <300d

F-18 Launch Weight, lbs <1,500e

Integration Length, in <168Span, in <24

Other No Ejectables

Wooden Roundf

a: Against Time-Critical Target Onlyb: Against Non-Time-Critical Targetc: Reinforced Concrete Targetd: Production Qty 4,000 Units Over 10 yrs; 2010 Entry into Servicee: F-18C Deployable; Must Carry at Least 2 Missiles and Bring Back Aboard Carrierf: Ready for Loading & Firing Directly from Shipping Container

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strategic value.

Table 1 summarizes the key HSSM metrics andconstraints, based on the RFP. Note that the combinationof flight speed, range, maximum allowable launchweight, and design cost required in the HSSM RFPtogether represent a considerable advance over today’sstate-of-the-art capabilities. It is evident thatconsiderable design innovation and technology infusionwill be required to achieve these goals in a single design.

Step 2: Morphological Matrix

The morphological matrix is simply a table used tofunctionally decompose a system. For the HSSM, thismeans describing the missile system in terms of keysubsystems. Therefore, the morphological matrix is used

as a brainstorming tool to list all possible ways in whicheach missile subsystem can be configured. The key tocreating this matrix is to select a set of attributes that isbroad enough not to exclude significant configurationalpossibilities, yet specific enough to focus design effortalong a few well-defined directions. The morphologicalmatrix for the HSSM design is provided in Table 2.

The next step was to develop a set of eightalternative configurations based on the possibilitiesenumerated in the morphological matrix. Thesealternatives were generated by selecting a single vector ofdesign attributes from the matrix, one selection per row.For example, Table 2 has a set of options (vector ofattributes) circled, one selection per row. This vector ofoptions constitutes one of the eight alternative concepts

Table 2: HSSM Morphological Matrix with Two Design Alternatives Shown: Solid Rocket Concept (Circled),and Ramjet Concept (Shaded)

1 2 3 4 5 6

System Cross-Section cylindrical oval diamond shape ALCM-like "flattened

triangle"waverider

Trajectory pure ballistic pure lifting pulsed propulsioncombination

ballistic/lifting

Maximum Mach 5.0 5.5 6.0 ballistic maximum

Cruise Mach 4.0 4.5 5.0 5.5 6.0 none

Aero Lifting Surface no wing fixed wingvariable geometry

wing

Nose shape sharp point blunt, round blunt, sharp inlet at nosenose extension (off-

nose shock)

Control Effectornone (spin-stabilized)

fins (tail) fins (canard) thrust vector control

Propulsion Type solid rocket ram rocket ATR ramjet scramjet turbojet

Inlet Type none scoop axisymmetric

Fuel Type pure solid hybrid solid gel fuels standard hydrocarbonsendothermic hydrocarbons

External Boost yes no

Structures &Thermal

Structural Concept

monocoquerings, frames,

stringersmolded

Thermal Concept hot structureTPS on internal (cold structure)

combination hot/cold

Nose Material Carbon/CarbonCeramic Matrix

CompositeTitanium Inconel

Titanium-Aluminide

hybrid

Body Material Carbon/CarbonCeramic Matrix

CompositeTitanium Inconel

Titanium-Aluminide

hybrid

Structural Cooling ablativethermal barrier

coatingactive cooling (fuel)

active cooling (inert chemical)

passive

Wing Support none fixed folding

Electronics/Avionics Guidance GPS INS

combination GPS/INS

astral INSradar reference

navigation

Primary Target Acquisition

GPS radar optical imaging lidar

Backup Target Acquisition

none GPS radar optical imaging ladar home-on laser

Communications continuous updateupdate from F-18

before launchupdate on ground

before loadingsingle midcourse

update

Electronics Cooling

none (therm. Robust systems)

prestored coolant fuel cooling heavy insulation

Characteristics

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initially investigated for the HSSM design. Themorphological matrix also has a set of options that areshaded. This set also forms one of the alternativeconfigurations studied for the HSSM design proposal.These eight alternatives were then compared side-by-sidein a Pugh matrix (not shown in the interest of brevity).

Steps 3&4: Initial Down-Select/Modeling & Simulation

Once a population of alternatives is synthesized, thenext step is to select a recommended designconfiguration. Ideally, this is done through rigorousmodeling and simulation of each design concept.However, the time and effort required to do a detailedevaluation of the previously defined eight alternativeconcepts is far greater than the resources available for thetask. Therefore, the approach used for the initial down-select is to do a low-level “back of the envelope” analysisfor each of the eight alternatives in the Pugh matrix andselect two designs for further development.

As there is insufficient space to discuss all eightalternatives, it must suffice to say that the twoconfigurations were selected based on their apparentability to meet RFP requirements. Subsequently, the bestelements of the losing configurations were incorporatedinto the winning baselines wherever possible. The twodesigns ultimately selected are the concepts circled andshaded in the morphological matrix. These conceptsconsist of a solid-rocket powered ballistic missile and aramjet-powered air-breathing missile, both of which arediscussed in detail in reference 5. The next two sectionswill describe the baseline configurations in detail as wellas the performance results estimated via the modeling andsimulation tools previously described.

Solid Rocket Baseline The solid rocket-powered baseline design concept

proposed to meet the design requirements previouslydiscussed is a conventional axisymmetric design with avery high propellant mass fraction, and was assigned thedesignation DKM119-7R. The missile is designed to flyin a ballistic trajectory at very high speed, and features asemi-staged design to enable achievement of high impactvelocities necessary to achieve adequate penetrationcapability against hardened targets. It is designed to besimple and cheap to manufacture, and employs a simple2-channel control system with a GPS-based guidancesystem using commercial off-the-shelf (COTS) systems.

Design drawings for the DKM119-7R are shown inFigure 2. The middle drawing shows a planform view ofthe design, and a notable feature is the large motor sizerelative to the warhead and guidance package. The 500nmi range requirement demands an extremely highpropellant mass fraction, and this is reflected in thedesign. Also notable is the large bulge roughly a third ofthe length of the missile. This bulge separates the motor

from the terminal flight package (warhead and guidancemodules).

The drawing on the bottom shows an inboard profilefor the DKM119-7R. The total missile length is 166inches, and weighs 1,500 lb. Maximum span is 20.5inches, with a terminal flight package maximum diameterof 10 inches. Notable features include the integral gasbottles (2), staging mechanism, control surfacearrangement, internal configuration, and nozzle/casedesign. The integral gas bottles store high pressurenitrogen used to power the control surfaces in flight, andare located in the guidance section as well as the nozzlethroat region. Integral gas bottles allow reducedstructural mass because the pressure bulkheads areredundant with the existing structural shell of the missile.In addition, the storage volume can easily be tailored tocapitalize on existing space, and bottle manufacture issimple, consisting of a single-pass weld. Bottlepositioning around the nozzle throat area has addedbenefits of 1) pre-stressing the nozzle to help ensurethroat area design intent using less structural material, 2)cooling of nozzle structural shell via heat transfer intobottle gas, 3) energization of bottle gas via heat transfer,allowing use of a smaller bottle for same control energy.

Design details of the staging mechanism are ofinterest because this is a key to the viability of theDKM119-7R design concept. The staging mechanismincorporates the unique feature of allowing the terminalflight package to be a flight-line changeable item, whichfacilitates quick turn-around times, simplifies flight linelogistics, and enables the concept of a derivative productfamily to be realized. The central idea is that if a series ofterminal flight packages can be built on a single motordesign, then the same motor can be used for a variety ofpurposes. One need only change the terminal flightpackage to adapt the weapon for a particular purpose.This allows quick adaptation of the basic design tocurrent needs, both at the flight line level and at theproduct design level, as described in detail later on. It isassumed that the launch lugs are attached to the motorcase via a strong back that allows the launch lug positionto be moved to match the missile CG position as theweight of the terminal flight package varies.

The control surface arrangement consists of a set offour jet vanes located in the nozzle diverging section anda set of four slab-surface movable control fins in the nosesection. The jet vanes are used for control during theinitial phases of flight when the motor is in operation, andare manufactured of carbon-carbon composite material.The four tail fins are fixed and are used to augmentstability. The four front fins are not in operation duringthe initial flight, but are put into operation at the start ofreentry, and operate for the remainder of the flight. Allcontrols are powered by compressed nitrogen.

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The internal arrangement is designed for maximumvolumetric efficiency within the envelope restrictionsallowable for aircraft compatibility. The warhead wasintentionally placed in front of the guidance package tohelp shield the guidance computers from the extremethermal loads imposed by the high flight Mach numbers.In addition, location of the warhead in the nose increasespackaging efficiency. In order to have adequate volumefor motor propellant, the outer case mold line diameter is16.5 inches. However, the high impact velocity demandsa terminal flight package with a high ballistic coefficient,and thus, the terminal package diameter is much smallerthan the motor, giving the missile the distinctive shape ofa high power rifle cartridge.

Finally, the nozzle design is a high performance,high area ratio configuration of single piece, rolled shellmanufacture. The nozzle bolts onto the rear of the motorcase shell for simplicity of manufacture and assembly.The case has a constant outer-diameter, with a mild hip atthe front. The terminal flight package is connected to thecase via a single bolt at the nose of the case, and a matingcollar that transfers flight loads from the eight-inchdiameter load platform on the case shell to the six-inchdiameter terminal flight package. It was elected to use aneight-inch diameter load-bearing platform because itallows heavier nose packages to be attached in the future,whereas, if a six-inch platform were used, there would bea severe limitation of growth potential. Thus, a heavierconfiguration with a mating collar was selected in spite ofthe weight, complexity, and cost penalties in the interestof product growth capability.

The top two drawings of Figure 2 show the terminalflight package detail and an isometric view of the missile.Note that the terminal flight package is very smallrelative to the motor, and is very simple in design. Theguidance system is COTS using GPS navigation with anINS backup. The major assemblies consist of a warheadmodule, a guidance module, a motor case module, and anozzle module. The simple design and modular nature ofthese assemblies greatly facilitates their separatemanufacture at remote sites and later assembly in a singlearea. In fact, the terminal flight package and the motormodule need not (and in fact should not) be assembleduntil it is placed on the aircraft wing. The bulk of theelectronics are located in the guidance section with onlyminimal electronics content in the nozzle section andwarhead fusing. The warhead itself is a multi-modedevice capable of being used in either ablast/fragmentation or herd-target penetration mode. Allstructural pieces requiring highly specialized manufactureare located in the nozzle and case, with the guidancesection structure consisting of a simple tube with end capand an internally-welded bulkhead, and the warhead caseconsisting of a precision casting.

Use of a conventional axisymmetric design allows agreatly reduced production cost, facilitates missilemodularity, and simplifies design and manufacture.However, the most important feature of the modularaxisymmetric design is that it facilitates the developmentof a “derivative family” concept of manufacture. Thisconcept has the potential to drastically reduce unit costby amortizing development, tooling, and production costsover much larger production runs than is possible using

Inboard profile

Planform View

Terminal Flight PackageIso from George

Figure 2: DKM119-7R Configuration, Inboard Profile, and Major Design Details.

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a conventional product development approach. Thisderivative family concept is key to achievement of theaggressive cost goals set forth in the RFP.

Derivative Missile Family Concept

The fundamental basis of the cost-control strategyemployed in this design is the realization that the bestway to drastically reduce unit cost to the levels targetedin this proposal is to lengthen production runs and fit theproduction rate to match the capacity of the availablemanufacturing capability. The key to making thishappen is product standardization and development of afamily of derivative products based on a common design.This concept, above all others, will enable achievementof unit cost targets proposed here.

The concept proposed here is to use the basic rocketmotor module as a building block for a family ofproducts. This idea is illustrated in Figure 3, whichshows a hypothetical family of missiles all based on thesame motor. For instance, it is possible to mount a 350 lbwarhead package on the 8 inch load pad of the rocketmotor to create a medium-range standoff missile.Attachment of an air-to-air package would create a long-range air-to-air missile in the AIM-120 Phoenix rangeclass. It may even be possible to develop more exoticweapons, such as a two-stage anti satellite weapon thatuses the high-performance solid rocket motor of theDKM119-7R as the first stage.

Such an arrangement has the ability to drasticallyreduce the unit cost of the motor because the productionrun would be much larger than that of the DKM119-7Ralone. Using such a concept, it would be possible toprocure a lot of motors as a separate buy from thepayload package, which increases procurementflexibility. It would be possible to ship bare rocket motormodules to the site of a regional conflict, and then usethese modules with whatever warhead need be used at thetime, thus increasing logistical flexibility. It would bepossible to easily upgrade existing hardware in the field,increasing technology transition flexibility. It wouldeven be possible to park aircraft on the ramp with barerocket motor modules on the pylons, attaching thepayload modules according to the instantaneous missionneeds, be it medium range standoff attack, anti-ballisticmissile combat air patrol, or long-range attack of pointtargets, thus increasing operational flexibility. Finally,such a concept would enable companies to rapidlyrespond to defense requirements by leveraging existinghardware designs towards new payload modules based onthe same motor module, thus increasing product lineflexibility.

An obvious extension of this concept would bedevelopment of motor modules, each of a specific totalimpulse class. The DKM119-7R motor module wouldserve as the foundation for the large-impulse class ofmissile motor, with other motor designs focused on the

medium and low impulse classes, rounding out thepropulsion spectrum. Moreover, if the staging/payloadattach mechanism were standardized across all missiles,various sized motors could be used for the same payloadpackage. For instance, a single air-to-air package wouldbe used with large impulse motors to make a long-rangemissile, and short-range motors to make a short-rangeAAM. Finally, it would be possible in this environmentto separately bid motor and payload. As a result, motorswould become a commodity, with differentmanufacturers competing for various motor contracts.

It is believed that this concept, more than any other,has the potential to make the cost goals defined for thismissile obtainable. If such a concept can be implementedon a wide scale, the economies of scale achieved throughstandardized production of missiles as a commodityshould be nothing less than revolutionary.

Design Drivers and Trade Philosophy

As mentioned previously, the principal driver for thisdesign is low unit cost. When making design decisionsinvolving trades on cost, all requirements wereconsidered to be negotiable in the interest of reduced unitcost. Since weight is closely related to cost, the designweight constraint of 1,500 lb was considered to be firm,and some compromises in design performance wereaccepted in the interest of reduced weight (and cost).This is the basic philosophy guiding the design decisionsfor the DKM119-7R concept.

The main system-level design drivers for thisconcept are given in Table 3. The $300K unit cost is the

Anti-Satellite

Long-Range Air-to-Air Missile

Medium-RangeGround Attack

Figure 3: Derivative Missile Concepts Based onDKM119-7R Rocket Motor Module

Table 3: Design Drivers on DKM119-7RConfiguration

Design Drivers Consequence500 Nmi Range • High Propellant Weight Fraction

• High Specific Impulse Motor• Complex Case And Nozzle Structure• Extremely High Energy Propellant

$300k Unit Cost • Modular, Product-Family Design• COTS Guidance System• Simple Axisymmetric Construction

4000 Ft/STerminalVelocity

• Extremely High Ballistic Coefficient• High Fineness Ratio• Ejectable Motor Case

TCT ReactionTime <10 Min

• High Flight Speeds Å BallisticFlight

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primary motivation for the introduction of a productfamily-oriented configuration. It also drives the use ofcommercially available guidance hardware, as well as theselection of a simple axisymmetric configuration. Therange requirement demands an extremely high propellantweight fraction as well as a high specific impulse for bestperformance. This in turn drives the rocket motor designto use a complex case and nozzle structure to achievelight weight with high performance. Finally, the rangerequirement implies that the propellant must have anextremely high energy density in order to maximizemotor impulse.

Another strong driver on the missile configuration isthe 4,000 ft/s terminal velocity requirement needed toachieve adequate penetration against hardened targets.This implies that the terminal flight package must go intoa powered dive and/or have an extremely high ballisticcoefficient. It was elected to design a terminal flightpackage with an extremely high ballistic coefficientrather than have a two-stage, powered-dive configurationbecause the added cost, weight, and complexity of havingan extra motor, nozzle, igniter, etc. was deemed to beinsufficient relative to the performance benefit.However, one must still have a staging mechanism so thatthe empty motor case can be discarded after use. Theterminal velocity requirement also drove the small (sixinch) radius and high fineness ratio of the terminal flightpackage.

Finally, the reaction time of 10 minutes against timecritical targets implies very high flight speeds. The dragassociated with flight at this speed in the sensibleatmosphere (below 120,000 ft) is high enough that onemust use sustained propulsion throughout the flight. Inorder to get sustained propulsion from a solid rocketmotor for 10 minutes, the thrust would be too low tomaintain powered flight. Therefore, the only option is touse a ballistic flight path in which takes the missile out ofthe sensible atmosphere for part of its flight. Thus, thetime requirement in conjunction with the rangerequirement drove the selection of a ballistic flightprofile. In addition, the long length of the terminal flightpackage, in conjunction with the large propellant massand 168 inch length requirement, drove the motor casediameter to 16.5 inches.

Requirements Compliance Matrix

The requirements compliance matrix for the solidrocket design is shown in Table 4. The order ofprecedence for design trades is generally taken to be: 1)cost, 2) weight, 3) TCT response time, 4) range, 5)terminal velocity. This general philosophy is reflected inthe compliance matrix, as a great deal of focus is given tomeeting cost and weight constraints within the enveloperestrictions of current launch platforms (F-18C). Assuch, all basic dimensional envelope requirements aremet, as are launch weight limits. As is discussed later,most of the performance objectives were met, but trades

on performance in the interest of weight and cost werenecessary. The ejectables requirement is violated for thisdesign in the interest of reduced cost (derivative familyconcept) and terminal flight velocity (high terminalpackage ballistic coefficient).

Air-Breathing Baseline The DKM119-4A high speed standoff missile is a

hypersonic ramjet-powered, long-range, precision-guidedweapon developed to meet the design requirements fornext-generation quick response to time critical targets atminimal per-shot cost. The missile is designed to usehigh-precision target coordinates supplied by off-boardassets as its principal means of targeting and is guided inflight by a GPS/INS equipped package to fly to anddestroy time-critical targets of opportunity. Once GPStarget coordinates are available, the weapon is launchedfrom an aircraft at patrol altitude, is boosted to ramjettakeover speed using a solid rocket motor, and thencruises to the target area at Mach 5. Once in the vicinity,the missile is designed to perform a terminal dive ontothe target where the multi-mode warhead is detonated ineither a blast/fragmentation mode for destruction ofsurface targets, or in a penetration mode for destructionof hardened targets.

The DKM119-4A is designed to perform at minimalcost and with maximum flexibility. The design featuressimple and modular construction that simplifiesmanufacturing, maintenance, and upgrades. Thepropulsion system contains no moving parts and isdesigned for high reliability/low cost. It uses an annularfuel tank with a high heat-capacity endothermic fuel toprotect the warhead, guidance computers, control system,and fuel control system from the harsh, high-temperatureflight environment, all without the need for extensive useof exotic materials technologies.

This avoidance of exotic high-risk technologies iskey to delivering a low-cost solution to the requirementswithin the desired development timeframe. Moreover,COTS components are used wherever possible in theinterest of reducing unit cost. For example, the guidance

Table 4: DKM119-7R Requirements ComplianceRequirement Go/No-Go500 Nmi Range ✔Air Launched, F-18C Compatible ✔Max. Mach Number > 5 ✔Time to Target for TCTs < 10 Min. ✔Off Boresight Launch > 20 Deg. ✔Length < 168 Inches ✔150 lb Warhead w/ 150 Foot Blast Radius ✔Concrete Penetration Depth of 20 Feet ✘ (18 ft)4000 ft/s Impact Velocity ✔Average Unit Production Cost of $300K ✔Wooden Round ✔No Ejectables ✘1,500 Lb Launch Weight ✔

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system is built entirely from off-the-shelf components,and the use of GPS/INS terminal guidance precludes theneed to put expensive seeker equipment on-board, furtherreducing unit costs.

An inboard profile of the basic design is given inFigure 4. Overall length is 168 inches, maximum span is24 inches, and launch weight is 1,480 lb. Note that thedesign is axisymmetric with a simple cylindrical bodyrather than a flattened lifting-body. There are severalreasons for this, the most important of which is that itreduces manufacturing costs considerably over custom-molded bodies by simplifying part geometry, fabrication,and assembly. Moreover, the axisymmetric configurationfacilitates design flexibility by allowing a simple modulardesign in which modules can easily be upgradedindependent of the surrounding vehicle. Additionally, theaxisymmetric configuration is desirable from a surfaceheating point of view, as it has less wetted area than otherconfigurations, and is structurally efficient becausepressure loads are carried in pure hoop stress.

The design features an axisymmetric, fixed-geometryconical inlet mounted on the nose of the vehicle. Theaxisymmetric inlet is used because it is relatively simpleand cheap to manufacture, while delivering acceptableinlet pressure recovery and off-design dragcharacteristics. The inlet employs no bleed or bypass inthe interest of simplicity and cost, and is sized to matchramjet engine flow demand at the design-point cruise

fight condition of 89,000 ft and Mach 5.

The DKM119-4A is controlled using movablecanard surfaces located just aft of the inlet and mountedon the forward fuselage frame that separates the inlet andmain body modules. The main body module consists ofan annular fuel tank wrapped around the warhead,guidance module, high pressure gas bottle, and fuelcontrol module. The fuel tank geometry is designed togive maximum thermal protection to sensitivecomponents while being structurally efficient. This fueltank is the primary load-bearing member connecting theforward section to the ramjet module, and is pressurizedduring ramjet operation, both for added bending stiffnessand to provide high-pressure fuel to the fuel controlsystem.

As mentioned previously, the warhead is a multi-mode design identical to that used in the DKM119-7R, asis the guidance computer hardware used in the guidancemodule. A high-pressure nitrogen gas bottle is mountedimmediately aft of the guidance module and is used forfuel tank pressurization, control system actuation, andinternal cavity purge (to ensure hot gasses are not able toenter the core bay area and overheat sensitivecomponents). The fuel control module uses a simplepressure-fed fuel system to feed fuel to four injectors inthe ramjet combustor. The use of four injection points inthe combustor facilitates efficient combustion andenables reasonably high turn-down ratios by staging the

Inboard profile

Planform View

Isometric View

Terminal Guidance Package

Figure 4:DKM119-4A Configuration, Inboard Profile, and Major Design Details.

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burners appropriately.

The ramjet combustor and nozzle are built as a singlemodule that bolts on to the mid-frame separating theramjet module from the main body package. The ramjetmodule features a four-cup vortex swirler combustor lineridentical to those used in aircraft gas turbine enginestoday. Although the swirler design is more complicatedand expensive than the spray-bar arrangements typicallyused in ramjet combustors, is allows much highercombustion efficiencies than are possible using spray-bars, and also facilitates swirler staging for part throttleoperation.

The ramjet is fed by an axisymmetric transfer ductthat moves the inlet air around the main body packageand back to the ramjet combustor. Note that the transferduct discharge features a turning vane and a lobed turningtab to promote the smooth flow of air into the collectionreservoir immediately forward of the swirlers. Thecombustor liner and nozzle are all air-cooled and areconstructed of conventional high-temperature alloys. Theramjet module also has a set of fixed fins attached to theexterior which are used for aerodynamic stability as wellas stiffening of the load-bearing ramjet module case. Theramjet nozzle exit plane incorporates a structural ring thatgirths the nozzle and acts as the thrust frame to transferloads from the booster into the ramjet case.

Finally, the aft 40% of the missile length consists ofa solid rocket booster used to propel the missile fromlaunch speed to ramjet takeover speed. This boostercontains 500 lb of high-energy propellant and produces7,000 lb of thrust during the eighteen-second boost phase,burning out at Mach 3.3. After burnout, the booster isdesigned to fall away and the ramjet takes over.Although it is possible to use a smaller booster and haveramjet takeover at an earlier time, the disadvantage of thisis that ramjet specific thrust is very low at these Machnumbers, and results in poor acceleration relative to thesolid rocket booster. As this is in direct conflict with thetime-to-target requirement, it was opted to use a largerbooster since the range requirement could be met withreasonable confidence. A conventional booster wasselected due to its low risk/cost, although this design doesnot comply with the “no ejectables” requirement. Onepossible solution is to use an integral ramjet/booster andthis is a technology worthy of further investigation. Notealso that the booster module incorporates a set ofaerodynamic fins to ensure static stability during theboost phase when the weight of the booster draws themissile center of gravity aft.

The figure above the inboard profile shows a fullaxisymmetric view of the DKM119-4A design. Note thehigh volumetric efficiency of the overall design due tothe annular fuel tank arrangement. The CG travel inflight is minimal because the fuel tank CG is nearlycoincidental with the vehicle CG, simplifying the controlsystem complexity and reducing development cost. Note

the relatively short inlet length and correspondingly lownose fineness ratio. Since the inlet design has noboundary layer bleed on the intake ramp, it is necessaryto keep the inlet ramps short to minimize the impact ofboundary layer separation on inlet operation.

The manufacturing breakpoints for the DKM119-4Adesign consist of an inlet, main body module, ramjetcombustor with nozzle, and booster module. The mainbody module is in turn broken into two sub-modules andthree assemblies: the warhead and guidance modules, andgas bottle, fuel system, and main fuel tank assemblies.This arrangement allows any major module to bereplaced independent of its surrounding modules, thusincreasing upgrade flexibility and maintainability.Second, it facilitates ease of manufacture. Finally, andmost importantly, it facilitates subcontracting of thebooster and ramjet module design and manufacturing tothose companies whose core competency is in theseareas. This “core competency” production concept isbased upon the idea that the best way to reduce productcosts is not to produce the entire missile “in house,” butrather to subcontract key components to those companieswhose core competency is in those fields. This concept iskey to reducing DKM119-4A unit cost and overall designrisk.

Design Drivers & Trade Philosophy

The highest-priority design driver on theconfiguration of the DKM119-4A missile is unitproduction cost. This requirement has received thepreponderance of attention because it will be difficult tomeet using air-breathing missile designs due to theirinherent complexity. Thus, considerable effort will bedevoted towards strategies to reduce cost, and this sectionwill show that the cost goals have a pervasive impact onthe overall design. In addition, this section will explainwhat are the other important design drivers and how theyimpact the design of the missile.

Other important design drivers on the DKM119-4Abesides cost are weight (which is usually closelyassociated with cost), and performance. When designtrades are necessary, the order of priorities used for theDKM119-4A is: cost, weight, time to target, range/payload, all others. This priority ranking can beexplained as follows: cost must be first because it is ahigh customer priority and failure to meet this target willgreatly increase the program’s vulnerability tocancellation. Weight is important because it is closelyrelated to cost and because the launch weight (andgeometric dimensions) must stay within the standardmissile envelope common to most aircraft in order for themissile to be widely compatible with existing equipment(thus increasing sales potential). The fundamentalpurpose of the DKM119-4A is to fill a void in operationalcapability, namely quick response to time-critical targets.Thus, the time to target requirement must be met,otherwise there is little justification for building the

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missile in the first place. Range and payload are alwaysimportant to any missile system, and it is seldom possibleto get more than enough of either. Finally, meeting allother requirements is important also, and every effort hasbeen made to ensure that the DKM119-4A satisfies all ofthese. However, satisfaction of these requirements willnot come at the expense of the previous four.

The primary design drivers on the configuration ofthe DKM119-4A are summarized in Table 6. Note thatthe cost requirement drives many aspects of missiledesign, as previously mentioned. In addition to theweight, time, and range loads, the fact that the missilemust fly at Mach 5+ in the atmosphere implies that thethermal loads on the airframe will be severe. This has astrong impact on the internal configuration of the missile,as well as on the material selection for airframestructures.

Requirements Compliance Matrix

Design compliance of the DKM119, model 4A withRFP requirements for high-speed standoff missiles issummarized in Table 5. The requirements emphasis is onmeeting range and time-to-target goals while drivingdown the unit-cost as much as possible. Note that thedesign meets all requirements except three, those beingunit cost, no-ejectables, and penetration depthrequirements. The first is due to the inherent complexityof an air-breathing design, while the second is due to theboost requirements to reach ramjet takeover speed.

The DKM119-4A meets the 500 nmi rangerequirement, and could be optimized to go considerablyfarther. The design is compatible with the F-18C interms of hardware, dimensional envelope, and launchenvelope. The maximum Mach number is greater than 5and the missile has 180o off-boresight launch capability.The design cost is $495K, 66% above target and impactspeed, penetration depth, and ejectable requirements arenot met, though it is likely the last three could be metwith the addition of an integral booster ramjet design.Finally, the design meets the launch weight limit with a20 lb weight margin.

Concept Evaluation and Selection Up to this point, the performance of the two

candidate designs has been presented in great detail, andeach was revealed to have some inherent strengths andweaknesses. However, the process of down-selecting to asingle design requires consideration of a variety ofattributes and performance parameters, most of whichcannot be compared on an “apples-to-apples” basis.Therefore, it is simply not possible to make this decisionbased on classical optimization techniques. Instead, thefinal decision rests largely upon intuitive judgement onthe part of the evaluator.

This intuitive approach to systems design has yieldedhighly successful systems in the past, and may yet

continue to do so in the future. However, there areseveral factors that are making it increasingly difficult torely solely on an individual’s intuitive judgement. First,acumen in judgement comes from experience in makingmany similar judgements. However, there are fewersystems in development today, and consequently, thereare also fewer opportunities for decision-makers to honetheir skill. Second, the cost of modern aerospace systemsis continuing to spiral ever upward. Consequently, thefinancial stakes of design decisions are increasingly gravewith each successive generation, and shareholders arenaturally reluctant to rely solely upon the judgement of asingle individual when the decisions could “make orbreak” the company. Finally, the complexity of modernaerospace systems is growing considerably over theprevious systems. Therefore, it is increasingly difficultfor any single person to become a true “expert” in everydiscipline necessary to evaluate a design.

The upshot of this situation is that there is a strong

Table 5: DKM119-4A Requirements ComplianceRequirement Go/No-Go500 Nmi Range ✔Air Launched F-18C Compatible ✔Max. Mach Number > 5 ✔Time to Target for TCTs < 10 Min. ✔Off Boresight Launch > 20 Deg. ✔Length < 168 Inches ✔150 lb Warhead with 150 Foot Blast Radius ✔Concrete Penetration Depth of 20 Feet ✘4000 ft/s Impact Velocity ✘Average Unit Production Cost of $300K ✘Wooden Round ✔No Ejectables ✘1,500 lb Launch Weight ✔

Table 6: Primary Design Drivers on DKM119-4AConfiguration

DesignDrivers

Consequence

$300KUnitCost

• Modular Design• COTS Components• Simple Geometry (Axisymmetric)• Strap-on Booster• “Core Competence” Business Strategy

Weight <1,500 lb

• Axisymmetric Cross-section• Simple and Efficient Load-Bearing Structure• 3 Simple Fuselage Frames• Simple Pressure Shells

Time toTarget <10 min

• Large Booster for Quick Acceleration• M5+ Cruise Speed Å Large Aero-Heating Loads• Canard-Mounted Controls (Due to Large Booster)

Range >500 nmi

• Low Ramjet SFC Å Conical Inlet+Vortex Swirlers• Low Empty Weight, Small Warhead Size

Aero-HeatingLoads

• Temperature-Tolerant “Superalloy” Case Materials• Annular Fuel Tank w/ Endothermic Fuel• Low Wetted Area Å Axisymmetric Cross-section• Gas-Operated Controls

ImpactVelocity

• Dynamic Pressure-Tolerant Airframe to 200 psia• Powered Flight into Target Å Reduced Range

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impetus to develop formalized methods and tools to assistthe designer in the multi-attribute decision-makingprocess. This section will describe a formalized selectionmethodology that can be used to down-select to a singledesign. This method will then be applied to assist in thedesign down-select for the HSSM design concept ofchoice for this paper.

Baseline Performance Results

The performance results for the solid rocket and air-breathing baseline HSSM designs are summarized andcompared against the RFP requirements in Table 7. Notethat the HSSM design requirements are grouped into 4broad categories: performance, lethality against a buriedtarget, lethality against a surface target, and cost. The F-18 compatibility constraints and 1,500 lb weight limit arenot included in this matrix because they were taken as“design to” constraints for both concepts. Consequently,it is assumed that both concepts are completely equal interms of compatibility and launch weight, which meansthat neither of these requirements impact the selectionprocess. Also, the no-ejectables requirement wasviolated for both concepts, so it also has no significantimpact on the selection process and is therefore notincluded in the evaluation matrix. It is clear from Table 7that the DKM119-7R has significant performance andcost advantages over the “-4A” configuration.

Step 5: Design Down-Select via TOPSIS

The next step is to evaluate these two designs anddown-select to a single design recommendation. The toolused to assist in this decision is TOPSIS,6 or Techniquefor Order Preference by Similarity to Ideal Solution.TOPSIS is a systematic means for ordering the variousalternative systems studied in terms of their fulfillment ofthe metrics and constraints. It works by estimating a totalproduct score based on the various performance metrics,where the influence of each requirement is normalizedbased on a weight assigned to each performance attributeto reflect the importance of that requirement. Differentscenarios (such as hard target or soft target scenarios) areaddressed by subjectively weighting key system attributesaccording to the needs of each scenario.

The first step is to normalize the results of Table 8against a datum and score results for each alternativesystem, per scenario. For the HSSM, the datum wastaken as a fictitious missile whose metrics lie directly onthe specified constraints (system requirements). Forexample, the datum missile has a maximum Machnumber of 5, a range of 500 nmi, and an impact velocityof 4000 ft/s. Thus, a design that exceeds the requirementin a particular category will have a score higher than100%, while a design that falls short will score less than100.

The next step is to select weighting factors for eachattribute of significance. The weighting factors selected

for this study are shown in Table 8. Since differentevaluators generally have unique estimates of how theimportance weighting should be distributed amongst thefour merit categories considered, several likely weightingscenarios are given. Two broad categories of scenario areconsidered, these being wartime use and “police action”use, the primary difference being that the latter class ofapplication is assumed to be more cost-sensitive than all-out wartime application. These two classes of conflictare further subdivided into two target types, these beingnon-time-critical and time-critical targets (the latter isassumed to be more sensitive to performance than is theformer). Finally, these four classes are further dividedinto surface (soft) targets and buried (hardened) targets.Thus, a total of eight weighting scenarios are considered.

The equation used to generate the system scores, perscenario, is given by

∑

∏×=

= =

4

1 1Score

i

in

jdatumj

ji

M

MWF (1)

The i values in Equation 1 correspond to the four

Table 7: HSSM Performance vis Å vis Requirements

Attribute MetricSolid

Rocket RFPAir-

BreatherPerf. Peak Flight Mach 8.7 5.0 5.0(min. time) Flight Time, sec. 456.0 600 768.0

Range, nmi 497.6 500 500.0Lethality Impact Velocity, fps 4,385.0 4000 <2,500(brd. Tgt.) Penetration Depth, ft. 17.8 20.0 ~10.0

Off-Boresight, deg. 180 180 180Lethality Surface Kill Radius, ft. 150 150 150(sfc. Tgt.) Off-Boresight, deg. 180 180 180Cost ACQ Cost, $1000’s 285.9 300 495.4

Table 8: HSSM Effectiveness Results for VariousWeighting Scenarios

Attribute Surface Buried Surface BuriedPerformance 60% 60% 50% 50%

Lethality: Surface 25% 0% 35% 0%

Lethality: Buried 0% 25% 0% 35%

Cost 15% 15% 15% 15%DKM-119-7R 140.0% 152.8% 126.2% 144.1%DKM-119-4A 55.96% 80.96% 48.15% 83.15%

Attribute Surface Buried Surface BuriedPerformance 30% 30% 20% 20%

Lethality: Surface 30% 0% 40% 0%

Lethality: Buried 0% 30% 0% 40%

Cost 40% 40% 40% 40%DKM-119-7R 112.6% 128.0% 98.8% 119.3%DKM-119-4A 47.66% 77.66% 39.85% 79.85%

Police Action UseTCT non-TCT

TCT non-TCTWartime Use

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attributes (performance, lethalities, cost). WF denotes theweighting factor for the ith attribute. j is the number ofmetrics comprising the ith attribute. The M values are thevalues of each of the j metrics, and “datum” refers to thevalue of Mj for the datum missile. The fraction term inthe above equation indicates a “higher-the-better” metric,i.e., a metric for which the highest value is desirable. For“lower-the-better” metrics (time of flight and cost), thereciprocal of the indicated fraction is used.

The results from TOPSIS analysis of the eightweighting scenarios are shown at the bottom of Table 8.It is evident from the scores that the DKM-7R emerges asthe clear victor for all eight scenarios due to its superiortime-to-target, penetration, and cost performance. Infact, with the exception of the ejectables requirement, itmet or surpassed all RFP requirements except penetrationdepth. It should be noted here, however, that theDKM119-4A concept could be considerably refined toimprove its performance, particularly with respect to itsrange performance. Therefore, if range performancewere a stronger driver in the HSSM design, the air-breathing design would be the weapon of choice over thesolid rocket, particularly because it has greater potentialfor range and payload growth than the solid rocket.

Conclusions The primary objective of this paper was to

demonstrate how several methods from decision theorycan be applied to the missile design process.Specifically, it was shown that the morphological andPugh matrices are useful tools for assisting the designerin organizing and synthesizing design alternatives in theface of almost limitless options. It was also shown thatTOPSIS can be used to assist in the multi-attributedecision-making process apropos a design down-select.

In addition to demonstrating new methods, theresults of this study suggest that it is possible to constructa relatively low-risk solid rocket-powered missile capableof simultaneously achieving the range, speed, weight, andcost targets defined in the 1998 MSTC RFP. In fact, itappears that solid rocket-powered configurations are inmany ways superior to the air-breathing designs andwarrant further investigation and development as viabledesign concepts for meeting the HSSM requirements.This is not to say that air-breathing concepts can berejected out-of-hand based on the results presented here.The scope and depth of the air-breathing concept analysisis simply too limited to permit a sweeping conclusion.Nevertheless, the solid rocket-powered concept appearsto be a strong contender worth more consideration than ithas heretofore received for the HSSM application.

It is further suggested that a key strategy towardsdriving cost down is to adopt a product family approachsimilar to the “core engine” philosophy used in theaircraft engine business wherein a single (expensive-to-develop) engine core us leveraged for a variety of

applications. A similar strategy could be used for aHSSM missile wherein a common propulsion unit couldserve as a platform for a variety of products, therebyincreasing commonality, reducing development costs forderivative systems, and amortizing tooling andproduction costs over much larger production runs.

Finally, several innovative design features weresuggested for incorporation into HSSM designs. Theseinclude the use of an integral gas bottle in the solid rocketconfiguration to save weight and cost, the use of a flight-line changeable terminal flight package, and the use of anoversized staging collar for future payload growth. Inaddition, both designs feature a highly modulararrangement (contrary to fashionable lifting-bodydesigns) that facilitates easy assembly, work-share splits,and product derivatives/upgrades.

Acknowledgements The authors would like to acknowledge the

contributions made to this paper by the 1999 HSSMdesign team: Mr. Andrew Frits, Mr. Brian German, Mr.Peter Hollingsworth, Mr. Steve Lebron, Mr. GeorgeMantis, Mr. Javier Rosario, and Mr. Jon Wallace. Theircontributions have been essential in making this workpossible. In addition, we would like to thank Mr. GeneFleeman for his patient guidance during the course of thisproject.

References

1 Missile Systems Technical Committee of the American Institute ofAeronautics and Astronautics. “Design Objectives and Requirements– Request for Proposal: High Speed Standoff Missile.” Aug. 3, 1998.

2 United States Air Force. “AGM-86B/C Missiles,” July 27, 1998.http://www.af.mil/news/factsheets/AGM_86B_C_Missiles.html.

3 Mavris, D.N., DeLaurentis, D.A., Soban, D.S., “ProbabilisticAssessment of Handling Qualities Constraints in AircraftPreliminary Design.” 36th Aerospace Sciences Meeting & Exhibit,Reno, NV, January 12-15, 1998. (AIAA-98-0492)

4 Mavris, D.N., Kirby, M.R., Qiu, S., “Technology Impact Forecastingfor a High Speed Civil Transport.” World Aviation Congress andExposition, Anaheim, CA, September 28-30, 1998. (SAE-985547)

5 Frits, German, Hollingsworth, Lebron, Mantis, Rosario, Roth, &Wallace, DKM119 Fast Attack, Air Launched Air to Ground Missile,Design Report Submitted to the AIAA Missile Systems TechnicalCommittee, available at: http://www.asdl.gatech.edu, June, 1999.

6 Hwang, Multiple Attribute Decision Making, Springer-Verlag, Berlin,1981.