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A Systems Engineering Examination of the
Short Range Antitank Weapon (SRAW)
By
John D. Rinko
Project Report submitted to the Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of
Master of Science
in
Systems Engineering
APPROVED:
Benjamin S. Blanchard, Chairman
br. Ue Beaton J. Dennis Hagan 3 “7
April 22, 1996
Blacksburg, Virginia
Key words: Systems Engineering, Anti-tank, Weapon, Human Factors, Optical Sight
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A Systems Engineering Examination of the
Short Range Antitank Weapon (SRAW)
By
John D. Rinko
Committee Chairman: Professor Benjamin S. Blanchard
Systems Engineering
(ABSTRACT)
This paper examines the systems engineering process of the development of a new
lightweight weapon system, a Short Range Anti-tank Weapon (SRAW) for the United
States Marine Corps. The systems engineering approach has been applied to this system.
The need for such an anti-tank system is established from examining currently fielded ant-
tank systems. The maintenance concept, operational requirements, functional analysis,
and requirements allocation are presented with an emphasis on the human interface. The
SRAW optical sight requirements are presented to illustrate the flow-down of the systems
engineering process to the component subassembly level. The results of a field test
verification of the optical sight requirements are presented as one example of the iterative
system development process.
Acknowledgments
The author wishes to thank J. Dennis Hagan, Principal Weapons Systems
Engineer, Naval Surface Warfare Center, Dahlgren, Virginia for serving as local advisor
and for attending the defense of this paper. Appreciation is offered to Professor Benjamin
S. Blanchard, Chairman, Virginia Tech Systems Engineering Program, for serving as
advisory chairman to this project, and to Dr. Robert J. Beaton, CPE, Virginia Tech
Associate Professor and Director of Displays and Controls Lab, for acting as a committee
member.
The author would also like to thank the Naval Surface Warfare Center, Dahlgren,
Virginia for the funding and the opportunity to pursue graduate studies, the Virginia Tech
satellite program for providing a wide selection of available courses, and his wife, Terri
Rinko, for her constant support.
ill
Table of Contents
Page ADStraCt occ ccccccccceeenececeeecesaeeeceeeeseceaeectaeseeeccneeseaeeredeessaseseaeeeseesesdeeetaesenaeed ii Acknowledgment .0...........ccccecssccccscneceesenececeeeaeeeessnaeersesseeeessnaseceesneneeecessneneeseseaaes lil List of Figures .............cccccees ec ccesceecesseeeeeceeeeeeceseeeeeeaeeeceetseeeccsessseeecesessseeteneaeees vi List Of Tables .........cccccccccccsssscessssceeeeeeeeeeeeeseessseneeeceeeeseesesesesnsaeasssaeeeeeeesesesees vi
1L.O INTRODUCTION .........0.ccccccccccccccccesescneeeseeeeeaceeeeesseseaaeeeseesessesssseeeseessensnees 1 2.0 STATEMENT OF NEED 00000... cc. cccccccccccccetnce cee ceneceeeceseeeeteseeeeeesenennaeeesenseenias l
2.1 HISTORICAL BACKGROUND... ccscssessseseeseesessesesseeeeenesesneeneaeeneenes 1 2.2 DEFICIENCIES OF CURRENT SYSTEMS .....cccccceccccceeeenteeeee 3 2.3 CONCLUSION... ccccccccccccesescecceeeensneeeeceseenneeeeeeeseeseesstseseeeteesaaees 3
3.0 OPERATIONAL REQUIREMENTS 0.000... .ccccccccesssstcceeecesceessstteeeeeeseesesaaeesees 4 3.1 MISSION DEFINITION..........0..ceccccccecceceseeceeeeeseneceesassseeeeseeateeessaes 4 3.2 MAINTENANCE CONCEPT ooo... cccccccccnceceeeeeeeesecnteeeeeeseeetneaaeeens 9
3.2.1 Organizational Maintenance ....0... cece cceeeeeeeceeeeeeeteetneeeeees 9 3.2.2 Intermediate Maintenance .............ccccccccccsccccceceeceseesentssssseneees 10
3.2.3 Depot Maintenance... ccccccsssccccesccceeeeesesceseeeestsssssaeees 11
3.3 SYSTEM PERFORMANCE AND PHYSICAL PARAMETERG......... 1] 3.3.1 Weight 0. cccceccccets te ceeeeeecesenssseeeeaeeeeeeeeeeseeeeeesteeaaaas 11
se 0271-4 | | ee 1]
3.3.3 PACKAQING oeceeeseecccccssnsecetssneceessseecesnsneeesesseceesesessaeesseeeaaeesoenee 11 3.3.4 RETIADILIY oc ceeccccccccssscceesssecssseeeceseaeeesessaceeeeeeeaneeesesanaesensaas 11 3.3.5 Service Life...cecccccccccccccccsccsessssscceeccessecseeeessessneaaeaaeeeeeeesseseesnes 12
3.3.6 TOV ZOU. ieeecccccccccccnennesenetseececeeceesoecceecaneusseceesceseeeeanseensseeeereseees 12
3.3.7 Inherent single shot hit probability (Pssu) .........ccccccccceeceseneees 12 3.3.8 Operational RANGC ...ccccccccccccccesscceesesneeeeessacececeeesnseeeseesenecsenaes 13 3.3.9 RESPONSE WINGS ooo... ccc ccccccececee cece eee eetnes tee eeeeseeeeeeeeeeensttensnaanas 13
3.3.9.1 [ritial SHOt INC ooo cece cect ceeceeeteenssteeseesensanes 13
3.3.9.2 EXPOSUTE LINE oo... eeeecceceeseeecceeeeeeeseneeceeeterseaneeaeoesees 13 3.3.9.3 FUriChion UINICS .occccccccccccccceccccceeecesceccececeecenaceeonecaaenes 13
3.3.10 Weapon firing Attitude ....iecccccsscecsssscessseesenscesesseeeseseeeooees 13 3.3.11 Optical Sight.......cciiccccccccccsteceeesesseseeeesssssececseensecessneeassoesenees 13
3.4 ENVIRONMENTS .......0.ccccccccccccccsccecencececsecsncaaeecesesensneaaaeeeseseeeeeaaeeeees 13 BAD Geter ...ceccccccccccccccccceccssesssssceeeeesesseseeseaauaaaaaeaaaaseesseeeeeeeeeees 13
3.4.2 Natural EnvirOnimen ts ...cccccccccccccceceeseeesceeesssssssseessceseesesensesenees 15
3.4.2.1 TeMpPeranure ...ccccccccccsccccsscscessccessssscenseeesssseesssssees 15 3.4.2.2 Low pressure (Altitude) .....cccccccccccssssssensceeesenssnnseeeoes 15
3.4.2.3 HUmidity ...ccccesccccccccescccsssseeeeseeeesnsecenenecesenasesesneesens 15 3.4.2.4 Sand ANA AuUSt...ecccccecccccccccceccseesessssanscaenanseeeeeseeeenenees 15
3.4.2.5 ICing/freCZING FAIR eeccssecsesesesssessssrsvessesctesstsssessseseaes 15 3.4.2.6 SAUt JOS oc ccccccccececssscseceeccssensesetsnnanacceeaneceeseeeseneesenees 15
3.4.2.7 FUNQUS oc ccccesscscseceeessncceeeessssaeeeeesesesssnenaceeesosssesaaeeens 15 3.4.2.8 SOlar PAGIAUION......ccccccccsssnccceeeesssnsncecencesensssonseesoeens 15
iV
3.4.2.9 Water iimer Sion ....ccccccccesesssnccceeeenssscneneeesensenseeeeees 16
3.4.2.10 ROG oe eeccccccccccccessnsneceeceesesnaaeeceessenseaanaecsesteenseesoees 16
3.4.21 Winds oeciccccccccccccscccccceeeesssnscceesessssanacaseccssssanaeessees 16 3.4.3 Induced CrvirOnnens .....cccceccccccccssccnscccccccccccceesseesssnensananaaeeees 16
3.4.3.1 ACCOLErQLIONL...ccccccccccsececeeeesessnnnsnsencceceeesceseeesusneaaaes 16
3.4.3.2 Temperature SNOCK ...csccccccsssccccesssseecevsssceescsssessoesaees 16 3.4.3.3 Basic transportation VibratiOn.......cccccsesssersesscessenes 16
3.4.3.4 Loose CAPO VIDPALION ..cccecccescsseessessesseteeseeseeseseeseens 17 3.4.3.5 Tactical Vibration ....cccccccccesssssscceesesessesaceeeensseneeenens 17
3.4.3.6 Missile-in-flight ViDFration ....ccccccccceessesesscceessnenceeeoes 17
3.4.3.7 THAHSIE AOD cicececccsscccsssecseeeseesessesneneanccenaceeeeeseeesesees 17
3.4.3.8 MU .oocecceccccccccesccssssneceeeeescsneeceeceeeeasaaneeeeseeseaseeesecenns 17 3.4.3.9 Parachute APOD ...cccccccccccccecscssceccceseesssnenaceeseesssneeeoes 17 3.4.3.10 ROG] TIPACH....ceeccececcccecceesseeessensnenaeenseseeseceeseresenees 17
4.0 FUNCTIONAL ANALYSIS... cccccccceectecceeteeneeeeeeeeseseeaaceeeeeeesscsereeeens 17 5.0 REQUIREMENTS ALLOCATION. 000... ccceccccececeseenncceeeeeeesetenseeesessenanees 23 6.0 LIFE CYCLE COST ANALYSIS 00.0... icccccccccccceeeeceeeeeeeeeeettcaeeeeeesenntneeeeeneas 25
6.1 RESEARCH AND DEVELOPMENT COST... eeeeeenteteeees 26 6.2 PRODUCTION COST oo cccccccccccccceccccessneeeeceseeentseaeeeeescssnseeeeentees 26 6.3 OPERATION AND MAINTENANCE COST .........cccccccccsssecceeeeeneees 26 6.4 DEMILITARIZATION AND DISPOSAL COST 0.00... ceeeeeee 27 6.5 LIFE CYCLE COST ESTIMATE AND PROFILE.............00:ccccceeerees 27
7.0 SRAW SYSTEM DESCRIPTION. 0.0.00. cccccccccecceceeceesenseceeeeeeeectenseeeeeneesneees 31 7.1 INTRODUCTION .........ccccccecccccccceeeeeeesceeeeseessssnnneeeeeeescaesnsetesesensaaes 31 7.2 LAUNCHER... cccccccccccceeecencneeececeeseeetaaeeeececsnsneeeceeeeteeseaereeesneaaes 31 7.3 MISSILE ASSEMBLY ..000... cece ccccccccccceesceeeceecesesteeeseeeescusssaeeeeenseeaaas 32
7.3.1 Target Detection Device (TDD) ....cccccccccccctccccetteetttseeeeeentanes 32 7.3.2 Warhead Module ........ccccccccccccceccetee cee sense teeeceesecnensaseeeeensanaess 33
7.3.3 Flight Module 00... ccccccccccccccccceceestecetescsesssceseseeesssessucessessenanes 33
8.0 SRAW LAUNCHER HUMAN FACTORS ISSUES... cccccecceceeseetteees 36 8.1 INTRODUCTION 000. ccececeeeeeetneteeseestenaneees s aeneceeeeeeneeaaes eee 36 8.2 HUMAN VISUAL SYSTEM... eeecccccceteesnnceeeeeeeseeentaaeeeesenneaaeeees 39 8.3 PREVIOUS RESEARCH ON ANTITANK WEAPON SIGHTS ......... 40 8.4 SRAW OPTICAL SIGHT HF REQUIREMENTS VERIFICATION .. 43
8.4.1 Test Procedure ......c.ccccccccccccccccececceeteeessaneeceeeeseceeteseseetsennanaaaes 44
8.4.2 Test Results... ..cccccccccccccscccccsssssscecssneeeesssueeeeeuseaaeeeeesanneeeeas shane 47 8.4.3 Verification Testing Debrief SUMIMNATY .0......ccc cece tet eees 49
8.4.4 Verification Test Conclusions and Recommendations ............ 49
9.0 CONCLUSIONS 20.0... ccc ccccccccssscccnseeesesseeeenssesecseeeeseeescsaeeessaeeessteeeesnaeersas 50 10.0 RECOMMENDATIONS FOR FURTHER STUDY ........0..ecccccccecestceeeeteees 50
REFERENCES .........ccccccccesscccesecscesteeesssseceenseeceseeesetaeceeaeecessaeeeseeeseneeses 52 SELECTED BIBLIOGRAPHY 0000... ccccccccceccceseesnneeeeeeteetensaaeeeeestsnaneeees 53
List of Figures
. Page
Figure 3.1 - SRAW Operational Life Cycle... ccccccceccessceeeesneeeeesteeeeesneeeeseas 7 Figure 3.2 - Second Level Distribution of SRAW During Operational Life Cycle... 8
Figure 3.3 - Mission Profile - Weapon Operational Sequence............eceeeeeeeeteees 10 Figure 4.1 - First Level Functional Analysis Flow Diagram for SRAW ...............6. 19 Figure 4.2 - Second Level Functional Analysis Flow Diagram for SRAW............... 20
Figure 4.3 - Third Level Functional Analysis Flow Diagram for SRAW.................. 21 Figure 4.4 - Maintenance Flow Diagram for SRAW.............cccccccccesssecesesseeeeeseeeees 22 Figure 5.1 - SRAW System Requirements Allocation..............cccccecseecsseeeesseeeeseeees 24 Figure 5.2 - SRAW Launcher Requirements Allocation............ccccceeeseeeeeteeeeeeeens 25 Figure 6.1 - Life Cycle Cost Profile.......0.....ccccccccccccssscesssseeeessscesessseeesesesssseesteeeens 28 Figure 6.2 - Life Cycle Cost Breakdown Structure............cccccccccceseeeeeseeeesteeeenseeees 30 Figure 7.1 - SRAW Missile with Launcher... cccccccccceececeeeessteeecessststeteeesennas 34
Figure 7.2 - SRAW Missile Principle Components ...............ccccccccseccceeeesteeeeetseeeees 35 Figure 8.1 - Prototype Launcher Design ............cccccccecccscccceeesseceeeesteeeeseetseeessteeeess 38 Figure 8.2 - LAW Reticle Pattern..........0...cccccccccccsssccesecseeceesseesesteeeeresesnseessseeens 41 Figure 8.3 - LAV-25 Frontal and Side View ............ccccccccssscceeecesstteeeeeessssteeseeseees 44
Figure 8.4 - Questionnaire .........00cccccccccccecccssseeeeeeeseeeeeecssneeeeeeeseeeeesseesensaeeceeas 46
Figure 8.5 - Number Of Gunners Preferring Each Configuration ..................cc0cc0 49 (Stationary Side View)
List of Tables
Page
Table 1 - Infantry Anti-tank Organization and Requirements .........0...cceeeeeseeees 2 Table 2 - Environmental Requirements .................ccccccceeseeeesseeeees ecteeeeeseteeereeteess 14 Table 3 - Life Cycle Cost Estimate .......0.0.0c.ccccecccccccsesescscesesssessseseeeeecsceeessseaeen wae 29 Table 4 - Optical Sight Test Configurations .....0.0....ccccccccccccessecessssceesseeeenseeeessserens 43 Table 5 - Test Scenarios ..........ccccccceeccceeeeseecestnceecenneesenacececeneeeeseaeeeeseeeseeseeeeesaas 45
Table 6 - Data Summary .....0.....0ccccccccccccesscccessecesesseeeeesseesecesseesensesesaeessesesensseeegss 48
vi
1.0 INTRODUCTION
This paper examines the systems engineering process of the development of a new
lightweight weapon system, a Short Range Anti-tank Weapon (SRAW) for the United
States Marine Corps (USMC). The systems engineering approach has been applied to this
system. The need for such an anti-tank system is established from examining currently
fielded ant-tank systems. The maintenance concept, operational requirements, functional
analysis, and requirements allocation are presented with an emphasis on the human
interface. The SRAW optical sight requirements are presented by the author to illustrate
the flow-down of the systems engineering process to the component subassembly level.
Each section of the report will focus on the SRAW system with the optical sight being
presented in more detail where appropriate to illustrate the transition from the general
(SRAW system) to the specific (SRAW optical sight). The results of a field test
verification of the optical sight requirements are presented as one example of the iterative
system development process.
2.0 STATEMENT OF NEED
2.1 HISTORICAL BACKGROUND
Combined arms warfare stresses the neutralization of enemy armor before contact
with infantry. This is accomplished by airborne platforms and friendly armor. In
situations where friendly airpower and armor is not available, the infantry must stand alone
with their organic weapons. This was dramatically brought home to the USMC on July 5,
1950 during early fighting in the Korean War. Lt. Col. Charles B. Smith with 540 soldiers
from the Ist Battalion, 21st Infantry went into battle against two North Korean regiments
with 33 tanks. Task Force Smith was overwhelmed, suffering heavy casualties. Task
Force Smith was composed of WWII veterans who did not break and run, but spiritedly
engaged the enemy. However, their antitank weapons were ineffective against the
Russian-made T-34s.!
New tactics and the development of modern reactive armor were prompted by the
effectiveness of Antitank Guided Missiles (ATGM) during the 1973 Arab-Israeli War,
when Israeli armor units suffered heavy losses by Egyptian ATGM. The new reactive
armor rendered many existing lightweight antitank systems obsolete.
The strategy and planning organizations within the Defense Department recognize
the threat to infantry posed by enemy armor. The current organization, doctrine, and
weapons mix of anti-tank infantry forces is the result of a 1950’s systems engineering
study. This study resulted in technology-driven categories of weapons: Light Weapons,
Medium Weapons, and Heavy weapons. This study was exclusively focused on the
massive Soviet armor threat in the European theater. Table 1 summarizes the results of
this study. These ranges and weights were then dictated to the weapons development
community. Initial fielding of weapons to meet these requirements (Light Assault
Weapon, Dragon, and the Tube launched Optically Tracked Wire Command weapon)
were completed by 1970.
Table 1 - Infantry Anti-tank Organization and Requirements
Weapon | Organizational Element Range Weight Weapon Ist
Category (meters) (Pounds) Issued
Light Company (200 men) 0-250 10 grew to 20 LAW
Medium | Battalion (600 men) 250-1000 | 30 grew to 50 Dragon
Heavy Division (3000+ men) 1000-3000 | Vehicle Mount TOW US ground forces are not often exposed to enemy armor without considerable
friendly armor and airpower to call upon. Situations arise where rapid reaction forces
such as airborne units, mountain brigades, and the USMC can be called upon to face
heavy armor of considerable quality. The recent Persian Gulf conflict illustrated this
situation. The first units to arrive in Saudi Arabia were elements of the 101st Airborne
and the USMC 7th Marine Expeditionary Brigade.” They referred to themselves as “speed
bumps” because they were deployed without their heavy equipment backup and were
incapable of stopping a heavy armor attack by Iraq. Initial insertions of American troops
can expect to face similar situations in the future, and will continue to need light category
anti-tank weapons.
2.2 DEFICIENCIES OF CURRENT SYSTEMS
Currently fielded man-portable antitank weapons are not capable of defeating
modern enemy tanks from all orientations. All current systems with sufficient lethality
weigh in excess of 50.0 pounds and are high cost systems, not truly man-portable or
disposable. Some systems such as Dragon require the gunner to maintain target tracking
for the duration of flight (multiple seconds), exposing the gunner to return fire. Other
systems are simply ineffectual against the heavy frontal armor of modern tanks
(insufficient warhead penetration). No man-portable weapon system currently in the field
is capable of firing from an enclosure. The noise, backblast, and toxic exhaust from the
rocket motor would kill or injure a gunner firing from an enclosed position. The inability
to fire from protected positions substantially reduces effectiveness in urban terrain and
reduces gunner survivability.
Cost is another deficiency of currently fielded anti-tank systems. The current
systems have very high operational maintenance costs, often driven by the missile
launcher. The launchers not disposable and as such require corrective and preventive
maintenance by highly skilled personnel. A launcher spare parts inventory must be
maintained and transported to the operational location. The missiles are inserted into the
launchers under field conditions, exposing the launcher interior to extreme environments.
The optics in current systems are high cost items, as they are designed for multiple firings.
2.3 CONCLUSION
To meet the emerging world-wide armor threats with low maintenance and low
cost, a Short Range Antitank Weapon (SRAW) must be developed for the USMC. The
system will be deployed worldwide, under all environmental conditions. Major
requirements for the system appear below.
e Cost Requirements
> Employ a disposable launcher concept to:
e reduce operation & maintenance cost;
e allow low-cost single use optics.
> Meet a $10,000/round Design Production Cost goal.
e Human Factors Requirements
> Weigh less than 20.0 pounds.
> Minimize gunner exposure time by employing fire and forget guidance.
> Easy to operate (user-friendly).
e Technical Requirements
> Be capable of firing from an enclosure.
> Require minimal scheduled and unscheduled maintenance.
> Engage targets at operational ranges of 17-600 meters.
> Defeat current and future main battle tanks with a minimum Probability of Single
Shot Hit of 0.5 at 500 meters. |
Note that the range requirement has been increased from 250 meters in the 1950’s study
to 600 m as inexpensive guidance technology developed. SRAW must be ready for initial
delivery by the year 2000 so as to keep pace with the evolving threat. The SRAW has
been identified as a high priority item for the USMC. Funding sufficient for the design,
test, and procurement of 21,000 units has been budgeted.
3.0 OPERATIONAL REQUIREMENTS
3.1 MISSION DEFINITION
The primary mission for the SRAW is to provide rapid-reaction ground forces with
an organic weapon system capable of defeating main battle tanks. This will be
accomplished by a light-weight, fire and forget, shoulder-launched missile package capable
of going with the troops into any environment. Although effective as an individual anti-
armor munition, the SRAW effectiveness will be maximized through a coordinated
employment plan and a well-trained gunner. The SRAW will be integrated into the anti-
armor tactical planning at the USMC Warfighting Center, Quantico, Virginia, and assault
gunners will be trained at Camp LeJeune, North Carolina. The SRAW is being designed
with emphasis on product life cycle. The SRAW completed preliminary design and was
approved for detailed design and development in June 1994. The detail design and
development in the Engineering and Manufacturing Development Process is to be
completed by February 1998, at which time a production decision (Milestone III) will be
made. The SRAW will first be delivered to the USMC in August 1999, delivery to the
first units by January 2000. A total of 21,000 units will be produced at a rate of
5,000/year. The units will have a ten year storage life, after which they will be phased out
and returned to the manufacturer for disposal.
The simplified operational life cycle by which the weapon will be deployed is
depicted in Figure 3.1. The weapon development will proceed from definition of
requirements to preliminary system design and then to detail design and development.
When block number 3.3, System Prototype Test and Evaluation, is completed in a
satisfactory manner, the SRAW weapon will be produced. The weapon will be distributed
to the USMC who will operate the SRAW in the gunner environment or maintain the
SRAW system. At the end ofits ten year service life, each SRAW weapon will be
returned to the manufacturer for disposal.
Figure 3.2 presents the second level distribution of the SRAW to the USMC.
The weapon will be transported from the manufacturer via air, truck, ship or rail to
intermediate maintenance sites in its palletized shipping container. These intermediate
maintenance sites include prepositioning ships, weapons stations, and logistics bases
worldwide. From here, the weapons will be transported to the Fleet Marine Force (FMF).
The FMF constitutes the end user of the weapon (the customer). The FMF customer will
open the shipping container and transport the weapon by infantry vehicle, landing craft, or
helicopter. The FMF gunner in the field will make a decision to fire the weapon. If the
weapon is unfired, the gunner will return it to the FMF inventory. Damaged items will be
returned to the Marine Corps Logistics Bases and from there, returned to the
manufacturer for disposal.
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A FMF gunner making the decision to fire the weapon will employ the operational
sequence illustrated in Figure 3.3. The gunner must detect a target, unsling the weapon
from a carry position, and assume a firing position. The gunner must be trained to clear
the backblast area of friendly troops. The optical sight may then be deployed, and the
target acquired within the reticle pattern. The gunner, using the optical sight, must
identify the target and determine if it is in range. By depressing the arm button, the missile
batteries will power up. The gunner will track the target and depress the trigger, releasing
the missile. The period between target detection and target acquisition is referred to as
the initial shot time and must not exceed 20 seconds. Gunner exposure time, defined as
the time period between target acquisition and missile first motion, must be less than 10
seconds. The missile will then cover the 600 meter range in less than 3 seconds.
3.2 MAINTENANCE CONCEPT
To minimize life cycle deployment costs, scheduled and unscheduled maintenance
will be minimized. Design compromises and weight penalties will be accepted to comply
with the “wooden round” concept. A “wooden round” 1s a stand-alone inventory item,
requiring no spare parts. The item is used once and discarded. Marine units in the field
will treat SRAW as any other round of ammunition. ‘No special facilities will be required.
3.2.1 Organizational Maintenance
The organizational maintenance site for SRAW is the FMF Scheduled -
maintenance will consist of visual inspection for launch tube damage and optical sight
integrity. The FMF will mount the nightsight as required by their missions. Damaged
items will be tagged for return to the manufacturer through the Marine Corps Logistics
Bases. Unscheduled maintenance will consist of removing mud or ice from the launcher.
Emergency situations such as transportation accidents will be handled by Explosive
Ordnance Disposal personnel.
INITIAL SHOT TIME
Target Detection Target Acquisition =
Unsling Weapon Assume Firing Deploy Acquire Position & Clear Sight Target
Backblast Area | |
T-17 sec T-14 T-10 T-7
EXPOSURE TIME
Target Missile Acquisition Determine Depress First
Target In-Range Arm Maintain Depress Motio ID andlayon | & Raise Trigger Button Target Trigger
Target | Guard Track |
T-7 sec T-5 T-2.5 T-0.5 T-0
MISSILE FLIGHT TIME
First Warhead R = 600m
Motion Arm |
T+0 sec T+0.45 — T+2.8
Figure 3.3 Mission Profile - Weapon Operational Sequence
3.2.2 Intermediate Maintenance
The intermediate maintenance sites for the SRAW are Maritime Preposition Ships,
Naval Weapons Stations, Fleet Wholesale/Retail Activities, and the Marine Corps
10
Logistics Bases. Scheduled maintenance consists of visual inspection of the shipping
container for damage and return of damaged units to the manufacturer. When the weapons
approach the end of service life, the intermediate maintenance sites will return them to the
manufacturer for disposal. Emergency situations such as transportation accidents will be
handled by Explosive Ordnance Disposal personnel.
3.2.3 Depot Maintenance
The depot maintenance site for the SRAW is the manufacturing plant. The
manufacturer will be responsible for the SRAW production, initial transportation to the
Marine Corps activity, and eventual safe disposal of damaged/obsolete units.
3.3 SYSTEM PERFORMANCE AND PHYSICAL PARAMETERS
The top level requirements, the mission profile and the maintenance concept drive
the performance and physical parameters. The worldwide deployment of the USMC
drives the required environmental conditions. Note that this is a partial listing of the
SRAW requirements. The SRAW Prime Item Development Specification contains a
complete listing.
3.3.1 Weight. No more than 20.0 Ib.
3.3.2 Length. Not to exceed 40.0 inches.
3.3.3 Packaging. The weapon is a self-contained, man-portable, wooden round. The
launcher serves as the package for the field handling environment.
3.3.4 Reliability. Since this system is an expendable muniton that will fire a single shot
and be discarded, reliability parameters such as mission duration and mean time between
operational failure do not apply. Each firing of a SRAW will be treated as an independent
Bernoulli trial with success being defined as the system functioning properly, i.e., weapon
reliability is the probability that the gunner will be able to sight in on a target, that the
ll
SRAW missile will be propelled from the launcher with the actuation of the propulsion
system, that the missile maintains a stable flight, that the Target Detection Device (TDD)
functions against specified targets, and that the warhead detonates high order. The
probability that the SRAW shall perform in this manner under the specified induced
(storage, transportation, and field handling) and natural environments shall be at least 0.95
at a 90 percent lower confidence level (LCL).
3.3.5 Service life. The weapon shall be designed for a service life of 10 years. Service life
shall consist of a mixture of storage time, normal transportation and handling time, and
field handling which the weapon may experience without degrading performance and
reliability below acceptable limits. This excludes damage by mishandling, contact with
unauthorized materials, or exposure to environments in excess of the required design
environments. Typical time frames associated with each phase of normal service life cycle
are: storage no more than 10 years, transportation no more than 3 months, and field
handling no more than 3 months.
3.3.6 Targets. The weapon shall be capable of accurately engaging and defeating current
and future advanced heavy-armor targets.
3.3.7 Inherent single shot hit probability (Pssu). The weapon Pgsy is defined as the
probability that the missile will fly over the target at a lethal standoff, the Target Detection
Device (TDD) will recognize a valid target and the warhead will detonate with timing and
orientation such that the Explosively Formed Penetrator (EFP) will impact the target. The
lethal standoff is the range of distances between the warhead and the target within which
the warhead will meet its performance requirements. The weapon Pssy against a 2.3m x
2.3.m x 4.6m (h x w x d) stationary target shall be no less than 0.5 (at a 90% Lower
Confidence Level (LCL)) at a range of 600 meters. The Pssy against a 2.3m x 4.6m x
2.3m (h x w x d) target crossing at a minimum of 24 kilometers per hour at 90 degrees to
the weapon-target axis shall be no less than 0.5 (at a 90% LCL) at a range of 200 meters.
12
3.3.8 Operational Range. The operational ranges for the missile shall be from 17 meters
(minimum) to 600 meters (maximum effective range) against stationary targets and from
17 meters to 200 meters against moving targets.
3.3.9 Response times. /
3.3.9.1 Initial shot time. The time from the carry/field handling position to the
ready-to-fire position, with the gunner in the kneeling, sitting, prone or standing position,
shall not exceed 20 seconds. This time does not include the time required to mount a
night vision device/scope.
3.3.9.2 Exposure time. The gunner's exposure time-to-fire the weapon, once in the ready
to fire position, must not exceed ten seconds. The weapon shall be designed to minimize
exposure during operations (including noise and movement requirements) in all firing
positions.
3.3.9.3 Function times. The missile flight time shall be less than 3.0 seconds to a range of
600 meters.
3.3.10 Weapon firing attitude. The weapon shall meet all accuracy requirements through
gunner engagement angles from 30° depression to 30° elevation. The gunner engagement
angle is defined as the angle between the gunner to target line of sight and the horizontal
(gravitational) plane. The weapon shall meet all accuracy requirements when fired with a
initial roll angle of up to 15°.
3.3.11 Optical Sight. The sight shall allow the gunner to effectively engage stationary and
moving 2.3m x 4.6m x 2.3m (h x w x d) targets throughout the operational range.
3.4 ENVIRONMENTS
3.4.1 General. The weapon shall be capable of operating properly in all battlefield
environments. The environmental requirements are summarized in Table 2.
13
TABLE 2. Environmental Requirements.
NATURAL ENVIRONMENTS
Ambient Temperature
-54°C to 68°C i P
-40°C to 63°C . P
-32°C to 63°C P
Altitude
0 to 3,657 m P P
0 to 12,192 m Pp P
Humidity P P P P
Sand and Dust Pp P P P
Icing Pp P P P
Salt Fog P P P P
Fungus P P P
Solar Radiation P P P P
Water Immersion P
Rain P P P P
Winds P P P P
INDUCED ENVIRONMENTS
Acceleration Pp
Temperature Shock P P
Basic Transportation Vibration P P P
Loose Cargo Vibration P P
Tactical Vibration P
Flight Vibration P
Transit Drop P P
Mud P
Parachute Drop Pp P P
Rail Impact P P Requirement: P - Performance
4
The weapon and the shipping container are as described previously in this document. Four configurations of this weapon are defined:
A. Storage: Weapons stored in the shipping container and palletized with TBD shipping containers.
B. Transportation: Weapon in a single shipping container.
C. Field handling: A single weapon out of the shipping container with
the scope not deployed.
14
D. Operational: A single weapon in the ready to fire configuration with the scope deployed.
3.4.2 Natural Environments
3.4.2.1 Temperature. The weapon shall perform as indicated during exposure to the
operational and after exposure to the storage temperature specified in Table 2.
3.4.2.2 Low pressure (Altitude). The weapon shall perform as indicated during exposure
to the operational altitude and after exposure to the storage altitudes specified in Table 2.
3.4.2.3 Humidity. The weapon shall perform as indicated during and after exposure to
humidity and temperature profiles as specified in the "High Relative Humidity with High
Temperature" paragraph of MIL-STD-210, Climatic Information to Determine Design
and Test Requirements for Military Systems and Equipment.
3.4.2.4 Sand and dust. The weapon shall perform as indicated during and after exposure
to the sand and dust environments described in the "Frequency of Occurrence"
subparagraph of the "Sand and Dust" paragraph of the "Worldwide Surface Environment"
section of MIL-STD-210. (The helicopter downwash environment shall not apply to the
Operational configuration.)
3.4.2.5 Icing/freezing rain. The weapon shall meet all performance requirements after a
minimum accumulation of 19 mm of clear glaze ice has been removed, where required, by
the use of antifreeze, salt, alcohol, chipping or warming by any readily available source.
The missile shall be capable of meeting the performance requirements of the system when
fired in an environment of freezing rain.
3.4.2.6 Salt fog. The weapon shall meet all performance requirements after a 48 hour
(minimum) exposure to a 5% salt spray at 35°C.
3.4.2.7 Fungus. The weapon shall not support the growth of fungus under conditions
favorable for the growth of fungus.
3.4.2.8 Solar radiation. The weapon shall meet all performance requirements during and
after exposure to solar radiation as described in the "Daily Cycle of Temperature and
15
Other Elements Associated with the Worldwide Hottest 1-Percent Temperature Value"
table of MIL-STD-210.
3.4.2.9 Water immersion. The weapon shall meet all performance requirements after
immersion both in fresh water and a 5% + 1% concentration of salt water at a minimum 1
meter from the top of the weapon for a minimum of 2 hours each.
3.4.2.10 Rain, The weapon shall meet all performance requirements during and
after exposure to the rain conditions described in the "Rainfall Rate" paragraph of the
"Worldwide Surface Environment" section of MIL-STD-210 for the "10 year period” and
"1 hour duration".
3.4.2.11 Winds. The weapon shall meet all performance requirements during and
after exposure to the "1 percent extreme", "1 minute steady" wind environment described
in the "Frequency of Occurrence" subparagraph of the "Wind Speed" paragraph of the
"Worldwide Surface Environment" section of MIL-STD-210. The weapon shall meet all
performance requirements after exposure to the "1 percent extreme", "associated gusts"
described in this subparagraph.
3.4.3 Induced environments. The SRAW weapon shall meet the indicated induced
environmental requirements shown in Table 2 or as defined below. Unless otherwise
specified, the weapon shall meet all performance requirements after exposure to these
environments.
3.4.3.1 Acceleration. The missile shall meet all performance requirements during and after
exposure to the SRAW launch and flight acceleration environments (with an appropriate
confidence factor added, reference MIL-STD-810 Environmental Test Methods, Table
513.4-I and Table 513.4-I]).
3.4.3.2 Temperature shock. The weapon shall meet all performance requirements after
exposure to temperature shock between -54° C and 68° C.
3.4.3.3 Basic transportation vibration. The weapon shall meet all performance
requirements after encountering vibrations resulting from all modes of transportation:
land, air and sea per MIL-STD-810, Method 514.4, Procedure I, Test Condition I-3.3.1.
16
3.4.3.4 Loose cargo vibration. The weapon shall meet all performance requirements after
exposure to loose cargo vibration per MIL-STD-810, Method 514.4, Category 3 for 1.5
hours.
3.4.3.5 Tactical vibration. The weapon shall meet all performance requirements after
exposure to ground-mobile wheeled vehicle vibration and ground-mobile track vehicle
vibration per MIL-STD-810, Method 514.4, Procedure I, Test Condition I-3.4.7 for three
hours vibration per axis.
3.4.3.6 Missile-in-flight vibration. The missile shall meet all performance requirements
during and after exposure to in-flight vibration levels with a 50% safety factor added as
determined during flight tests in the EMD effort.
3.4.3.7 Transit drop. The weapon shall meet all performance requirements after exposure
to a 1.5m drop in either the Transportation or Field Handling configurations.
3.4.3.8 Mud. The weapon shall meet the performance requirements herein following
immersion in wet and dried mud as specified in Military Testing Definition Test
Operational Procedure 3-2-045 “Automatic Weapons, Machine Guns, Hand and Shoulder
Weapons” under all service conditions.
3.4.3.9 Parachute drop. The weapon, in the field handling and transportation
configuration, shall meet all accuracy requirements after air transport and air drop while
stabilized at ambient temperature and shall be capable of immediate deployment.
Packaging and rigging of material shall be in accordance with MIL-STD-814.
3.4.3.10 Rail impact. The weapon in the shipping container shall meet all performance
requirements after exposure to rail impact per MIL-STD-810, Method 514.4, Category 5.
4.0 FUNCTIONAL ANALYSIS
A partial functional analysis is presented to translate the operational and support
requirements of Section 3.0 into the design requirements of the SRAW. The operational
17
requirements and the maintenance concept were used to create Figures 4.1, 4.2, and 4.3
which show the operational functional flow to three levels. Figure 4.3 addresses the
optical sight operation. Figure 4.4 shows the maintenance flow diagram for SRAW to »
two levels.
18
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All of the SRAW system functions could be detailed to the third level. Only the
optical sight functions are shown to this level. These diagrams show the SRAW system
operation is consistent with the low maintenance requirements and provide insight to the
functional requirements of the optical sight. These diagrams will also form the basis for
later analyses, e.g., Failure Mode, Effects, and Criticality Analysis, Fault Trees, Safety
Analyses, etc. of the SRAW system
5.0 REQUIREMENTS ALLOCATION
Figure 5.1 shows the overall system allocation of requirements. Note that since
this system is an expendable muniton which includes one-shot items (warhead, rocket
motor, batteries, etc.) the reliability allocation is presented in terms of success probability
for all components, even those components for which standard measures would normally
apply. The cost figures for the SRAW weapon refer to unit production cost based on
21,000 units. Life cycle cost details are discussed in Section 6.
The inherent reliability of the SRAW weapon (missile + launcher) must be greater
than 0.95 because when combined with gunner human limitations, the system must have
an inherent single shot hit probability of 0.5. The gunner will be under extreme stress,
performing heavy physical exertion, wearing bulky protective gear, or under hostile
environmental conditions. To account for the human limitations, gunner accuracy under
degraded conditions has been allocated at 0.6 probability of hitting the tank-sized targets
previously defined.
23
SRAW System
Inherent Single Shot Hit Probability: 0.57
Ranges: 600 m Stationary Target
250 m Target Crossing at 24 km/hr
[
I. saad SRAW Weapon USMC Assault Gunner
Reliablity: 0.956 Mean Accuracy at Req'd
Weight: 20 lbs Ranges Under Degraded
Cost: $10,000 Conditions: 0.60
| l. wal
Launcher Missile
Reliablity: 0.984 Reliablity: 0.972 Weight: 5 Ibs Weight: 15 lbs
Cost: $1,000 Cost: $9,000
Veeesssssssscussssetsnny qeesssscnanensvesssetaafesetsnseenenesssetene sl TDD Module Warhead Module Flight Module
Reliability: 0.998 Reliability: 0.989 Reliability: 0.985 Weight: 1.0 Ibs Weight: 6.0 Ibs Weight 8 Ibs
Cost: $3,000 Cost:$2,000 Cost: $4,000
.. | ” . Autopilot Rocket Motor Jet Reaction Control Assy
Reliability: 0.998 Reliability: 0.992 Reliability: 0.995 i Weight: 0.5 Ibs Weight: 6.25 Ibs Weight: 1.25 Ibs
Cost: $2,000 Cost: $1,000 Cost: $1,000
Figure 5.1 - SRAW System Requirements Allocation
The SRAW weapons subsystems result from the functional analysis. The missile
related functions evolve from Figure 4.2, 10.5, Missile Launch, if taken to the third and
fourth levels. A more detailed requirements allocation is presented for the launcher in
Figure 5.2. This allocation will meet the required gunner operational and maintenance
functions in Figures 4.2-4.4 and will help to form the basis for an optical sight design
requirement which takes into account gunner human factors.
24
Launcher
Reliability: 0.984
Weight: 5.0 Ibs
. Cost: $1,000
| J : levee J
Launch Tube Optical Sight Assy. Sling/Handles/Closures Trigger Assy.
Reliability:0.9965 Reliability: 0.9979 Reliability:0.998 Reliability: 0.9915 Weight: 3.0 Ibs Weight 0.5 Weight: 0.75 lbs Weight: 0.75
Cost: $600 Cost: $50 Cost: $250 Cost:$100
Figure 5.2 - SRAW Launcher Requirements Allocation
This allocation shows the cost and weight resource limits for the SRAW system.
System accuracy will be limited by the gunner. A SRAW weapon designed to these
requirements will be able to accomplish the mission profile within the cost budget,
employing the described operational and maintenance functions. A large cost driver in
previous, non-disposable anti-tank systems was the optical sight assembly. The $50
production cost and the 0.5 pound weight budget will limit the quality and size of the
SRAW optical sight. The disposable launcher concept will enable the SRAW optical sight
to meet performance within the total system constraints.
6.0 LIFE CYCLE COST ANALYSIS
A Life-Cycle-Cost (LCC) analysis has been conducted with the objective of
optimizing SRAW system characteristics of minimum LCC, high performance, and high
reliability. The major elements of the LCC are the Research and Development (R&D)
cost, the production cost, the Operating and Support (O&S) cost and the Disposal and
Demilitarization (D&D) cost. Costs are based on production quantity of 21,000 units
over 5 years.
25
6.1 RESEARCH AND DEVELOPMENT COST
This area includes the cost of funding the system management and engineering
design of the SRAW. All aspects of engineering design - conceptual, preliminary and
detail - are included. The cost of developing SRAW-specific technology is included in this
category. Initial feasibility studies, software coding and debugging, and design trade-offs
are accounted for in this category. Engineering efforts to support future product
improvements and all testing through the man-rating process are included in this cost
category. The cost of preparing, printing, publishing, and distributing all reports, plans,
and analyses relating to each design requirement is included. Once the design is finalized,
these costs are non-recurring.
6.2 PRODUCTION COST
Production costs include both recurring and non-recurring costs. Non-recurring
costs include tooling and test equipment costs of $10 million, construction cost of $25
million and First Article Testing costs of $10 million. Over the five year production,
recurring costs include production management, industrial engineering, manufacturing
material costs and labor costs, maintenance of constructed production facilities, quality
control management and inspection costs. Initial logistic support includes all integrated
logistic support planning for the SRAW system. This includes logistic program
management cost, inventory management costs, development of training manuals, aids,
and personnel, and initial transport of the SRAW to the Marine Corps logistics bases.
6.3 OPERATIONAL AND MAINTENANCE COST
Includes all costs associated with operation and maintenance of the SRAW after
delivered to the inventory. Life cycle management and operator training costs are
included. Note that operating personnel cost has not been included in this analysis.
Current Marine assault gunners will substitute the SRAW for their current issued weapon.
26
The gunners will require training on the new system, but their number will remain
unchanged. Maintenance of the system data package and product improvements are
included in this category. Distribution cost of shipment to any Foreign Theater of
Operation is an operational cost. The low maintenance concept reduces maintenance
personnel and support cost, corrective maintenance cost, spare parts cost, test and support
equipment cost, maintenance training cost, and maintenance facilities costs to zero.
6.4 DISPOSAL AND DEMILITARIZATION COST
This cost category includes all costs of SRAW demilitarization when removed
from service. Explosive disposal cost is included. Demilitarization will be conducted by
contractor personnel at the manufacturer plant at the end of the ten year storage life. This
category also includes funding for Explosive Ordnance Personnel to handle emergency
render-safe situations resulting from traffic accidents and the routine demilitarization of
systems that were activated, but not launched.
6.5 LIFE CYCLE COST ESTIMATE AND PROFILE
Table 3 presents the SRAW LCC estimate in constant FY95 dollars, assuming a
three year R&D program, a five year production of 21,000 SRAW units (1,000 units the
first year and 5,000/yr thereafter) and a useful storage life of 10 years. Remaining units
would then be disposed of by the manufacturer. The benefit of the low maintenance
concept is illustrated in Figure 6.1 which presents the LCC profile. The cost “spike” in
FY98 is derived from non-recurring, up-front production costs. After FY98, the funding
profile is much more benign because no spare parts inventory or preventive maintenance is
required. After production is completed in FY03, training costs predominate. The total
acquisition cost in 1995 dollars is $240,760,000. Figure 6.2 shows the LCC break down
structure.
27
COST
($K)
60000
50000
40000
30000
20000
10000
FY95
FY97
FY99
FY01
FY03
FYOS
FYO7
FYO9
FY14
LIFE CYCLE (YR)
Figure 6.1 - Life Cycle Cost Profile
28
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29
|
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System Acquisiton
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Demilitarization
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Design Engineering Distribution
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Test & | | Construction | |_ Product Evaluation Improvements
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Initial Logisitc
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30
7.0 SRAW SYSTEM DESCRIPTION
7.1 INTRODUCTION
The Naval Surface Warfare Center, Dahlgren Division (NSWCDD) is currently
procuring a Short Range Antitank Weapon (SRAW) system to meet these requirements.
NSWCDD is in the eighteenth month of an Engineering & Manufacturing Development
(EMD) program to demonstrate the performance of a production ready system. SRAW
missiles are currently being flown at test facilities in China Lake, California. This section
describes the characteristics of the system under test.
The SRAW consists of a missile in a launcher as shown in Figure 7.1. The SRAW
uses an on-board inertial sensing system to guide it to its target. The SRAW is designed
to fly over targets and uses both a laser for active optical ranging and a magnetometer for
magnetic sensing to detect targets. When the SRAW missile senses the target, it fires a
top attack penetrator warhead. This warhead exploits the more vulnerable turret armor.
After the missile is launched the launcher becomes a disposable item.
7.2 LAUNCHER
The Launcher Assembly consists of a graphite/epoxy filament wound launch tube,
mechanical trigger assembly, optical sight assembly, carry handle and sling, end closures
and shock isolators. The launch tube features an internal, 45 degree conical seat which
provides the interface for the missile. Once installed, the missile is held in tension between
the seat and the launch tube aft end by the Aft Closure Release Mechanism (ACRM). It
holds the missile in the launch tube and the aft closure in place prior to launch. During the
launch sequence, immediately prior to launch, the ACRM is ejected by activation of a
warm gas pressure cartridge. The end closures provide an o-ring seal to protect the
missile from the external environment. In addition, the missile is protected from drop
shocks during field handling and transportation by the foam isolators located at each end
3]
of the launch tube. The length of the Launcher Assembly is approximately 34.5 inches.
The outside diameter of the launch tube is 5.7 inches while the outside diameter of the
shock isolators is 8.2 inches. The total weight of the Launcher Assembly is approximately
5.0 pounds. :
Examining the optical sight assembly in greater detail reveals packaging oriented
constraints. Weight and the required physical envelope require that the objective lens
diameter be no greater than one inch. Conceptual design studies revealed that the optical
sight must periscope away from the launch tube during use to accommodate the gunner’s
helmet. The length of this mirrored periscope assembly must be less than 2.2 inches. To
meet the initial shot time requirements, the sight assembly will be fixed-focus. No
adjustments to the sight assembly will be possible. This will also reduce the possibility of
damage to the sight assembly by eliminating sight deployment during field handling. The
sight must be designed so that under nominal conditions the resolution is limited by the
human eye, minimum resolution of 1 minute of arc (290 prad). The transmission goal at
low light levels is 50% minimum transmission.
7.3 MISSILE ASSEMBLY
The Missile Assembly in Figure 7.2 is made up of three modular sections:
e Target Detection Device (TDD)
e Warhead Module
e Flight Module ,
The missile is 5.5 inches in diameter, 27.5 inches long and has a total fin span of 10.4
inches. It weighs 15 pounds.
7.3.1 Target Detection Device (TDD)
The TDD module is an integrated target sensing system that utilizes a laser ranging
device and a three-axis flux-gate magnetometer to sense tank targets as the missile flies
above them and to calculate the firing point for the warhead based upon target shape and
32
height above the tank. The TDD module interfaces with the remainder of the missile
system electronics through a connector. Based upon the nature of the range and magnetic
signatures, the microprocessor determines if and when to output a firing signal to the a
warhead module.
7.3.2 Warhead Module
The Warhead Module consists of a Explosively Formed Penetrator (EFP)
Warhead, transfer manifold, and a safety and arming assembly all housed in a plastic
structure. The warhead is designed to defeat the roof armor of a tank in a close missile
overflight application.
7.3.3 Flight Module |
The Flight Module consists of the rocket motor, Autopilot Assembly and Jet
Reaction Control Assembly (IRCA). The rocket motor assembly is a two stage
propulsion system consisting of a launch motor and a flight motor. The missile guidance is
controlled by the Autopilot Assembly and the JRCA. Control Algorithms are
implemented by a microprocessor which issues on/off commands to appropriate valves of
the JRCA. Four pop-up fins are attached to the JRCA to provide stable flight
characteristics. Gas generator thrust is vectored by the eight JRC valves which open and
close by command of the autopilot. JRCA thrust controls attitude and flight path of the
missile.
33
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35
8.0 SRAW LAUNCHER HUMAN FACTORS ISSUES
8.1 INTRODUCTION
At this point in the development life cycle, the detail design focus is on the SRAW
missile. Detail design of the launcher has been deferred until the missile is mature. A
prototype launcher has been delivered for a human factors evaluation. This evaluation will
be the last cost-effective opportunity to review the launcher requirements and influence
the design .
Proper design of the SRAW launcher is critical to system success. The launcher
must protect the SRAW missile from environmental stress (hot/cold temperature
extremes, moisture, etc.), transportation vibration, inadvertent drops, and field handling
conditions. The alignment tolerances of the launcher will have direct impact on system
accuracy. Moreover, the launcher is the human-machine interface for the system. The
Marine will never see the SRAW missile until it is launched. His perception and usage of
the system will be dependent on the launcher. A well-designed launcher will allow the
Marine improved mobility, increase his ability to successfully engage targets, and directly
affect his confidence in and willingness to carry the SRAW in combat.
The prototype SRAW launcher is shown in Figure 8.1. Launcher human factors
issues to be resolved include:
e The sling quick release mechanism. Must be comfortable during transport and allow
rapid and unencumbered change from carry position to fire position.
e The shoulder stop. Must fit 5th to 95th percentile Marines using cold weather gear,
flak jacket, etc.
e The front grip. Location and type must be appropriate for transport and firing. It
must not snag on obstacles or equipment.
e Night sight compatibility. The SRAW with rifle-mounted night vision equipment must
be comfortable during use with protective gear under adverse conditions.
36
e Trigger mechanism. Must provide safety and preclude inadvertent operation using
simple tasking to minimize gunner error.
e Controls must be clearly identifiable under adverse conditions (darkness, Arctic
weather gear, Nuclear, Biological, Chemical (NBC) protective gear)
e Optical Sight Design. Must provide the gunner with a visual image magnification
sufficient to identify targets at extreme ranges and a field of view sufficient to track
moving targets at short ranges under all environmental conditions.
The human factors related to the optical sight design will be discussed in greater detail.
A discussion of the human eye which will limit the system resolution, a review of previous
research on anti-tank sights which lead to a baseline requirement, and the results of human
factors verification testing of the baseline requirement will be presented on this one issue.
37
Sling
Trigger Assembly/ Energy Source
Shock Isolator
Sight Assembly (>
Handle Sv 4
Shoulder Stop
Launch Tube
Shock Isolator
Closure
FIGURE 8.1 - PROTOTYPE LAUNCHER DESIGN
38
8.2 HUMAN VISUAL SYSTEM
The SRAW optical sight requirements are dependent on and limited by the human
visual system. The human eye and its photoreceptors transmit visual information to the
brain via the optic nerve. This is accomplished through the absorption of photons in
photopigments (rods and cones) of the retina. Incoming light passes through the cornea
into a clear liquid called the aqueous humor. The adjustable diameter iris acts as a variable
lens stop and allows the eye to regulate the intensity of light entering the lens. The lens
focal length is adjusted by the ciliary muscle to focus an image on the retina. The cavity
behind the lens is filled with a substance called the vitreous humor. The eye thus has four
media of refraction: cornea, aqueous humor, lens, and vitreous humor. Refraction occurs
at four interfaces: air-cornea, cornea-aqueous humor, aqueous humor-lens, and lens-
vitreous humor. The image formed on the retina is upside down and mirror reversed, but
the brain learns to compensate for this early in life.
The light photons falling on the retina excite rods and cones. The cones are
concentrated in the center of the retina in a region called the fovea. The cones are color-
sensitive, but require higher illumination (daylight conditions) than the rods which are used
for nighttime conditions. Vision predominated by the cones is known as photopic vision.
Since the SRAW sight assembly will only be required to function under daylight
conditions, the image formed on the retina should be centered on the fovea for maximum
resolution or acuity.
The eye is sensitive to the visible portion of the electromagnetic spectrum from
about 400-700 nanometers. Visual sensitivity is not constant throughout the visible
spectrum. Sensitivity peaks from about 500-600 nanometers (green-yellow) and is
characterized by the photopic standard observer curves. The human visual system
requires a minimum contrast ratio of 3:1 to distinguish objects. The contrast ratio is the
ratio of maximum luminance (the total perceived energy emitted from a surface) to the
minimum luminance. The contrast ratio becomes important, for example, in trying to
39
distinguish a olive-drab green tank from a forest green background. The human eye is
sensitive to luminance changes over a range of 10’° an is able to detect as few as 10 to 20
photons in the most sensitive wavelengths of the visible spectrum (green-yellow). The
detection threshold intensity for cone vision is 3.2 candela/meter’.
8.3 PREVIOUS HUMAN FACTORS RESEARCH ON LIGHT ANTITANK WEAPONS
OPTICAL SIGHTS
Available data on antitank weapon sights is limited, but sufficient to provide some
direction. Evaluation of the M72 Light Antitank Weapon (LAW) revealed shortcomings
in the reticle design’. The LAW reticle featured stadia lines to assist with range estimation
and velocity. The LAW reticle pattern described is presented in Figure 8.2.4 LAW
gunners were highly tasked, being asked to compensate for target range, orientation, and
velocity, hence the complicated reticle with stadia lines. Less than predicted hit
probabilities documented during infantry training and Vietnam prompted a review of
training methods. This resulted in a new engagement procedure.”
40
Front sight using the stacia lines for range estimation. When the tank is straddled by the stadia lines, the range is marked. Here the tank is at 200 metres
FIGURE 8.2 - LAW RETICLE PATTERN
In a previous study of light antitank weapon sights, ten candidate sights were
evaluated for a prototype LAW replacement. Nine range-finding sights utilizing stadia
lines and one post-and-peep (rifle) sight were evaluated against an M60 tank target. The
results of the experiment showed that none of the sights used provided much improvement
versus iron sights for gunners tasked with range estimation’.
The SRAW allocates the range, gravity, and target velocity compensation to the
missile, simplifying the gunner’s task. The gunner is tasked only to acquire, identify, and
track the target. The gunner only needs to grossly determine if the tank is within the
600m range. Based on previous work, this task is appropriate to iron sights. As a result,
a simple vertical/horizontal crosshair reticle pattern is utilized in the SRAW prototype
system.
41
Regarding magnification and field of view (FOV), a maximum magnification of
4X for rifle scopes is recommended’. Other authors recommend 1-1.5 X for aircraft-sized
targets at less than 1000 meter range®. No quantitative guidance is given regarding field
of view requirements, merely that the field of view be compatible with the intended use.
Magnification and field of view require tradeoffs for a given objective diameter.
Increased magnification results in decreased field of view, unless the size of the optics is
increased as well. Also, the amount of light transmitted decreases with increased
magnification, making a high magnification scope less suited to low ambient light
conditions. Light transmission can be improved by increased optical quality, resulting in
higher cost. The 20.0 pound system weight budget and the $10,000/unit production cost
goal of the SRAW program limits both size (weight) and optical quality. To
accommodate these limits, a one inch objective diameter was selected and a 0.5 pound
sight weight limit was set. For the one inch diameter objective, a diffraction limit can be
calculated as 6Qmin = 1.22 A/lens diameter, where 6Q;in is the minimum angular separation
that can be resolved, 4 is the wavelength of light (using 550 nanometers), and d is the lens
diameter 0.0254 m (1 inch).’ The minimum angular separation is 26.45 j1rad, much less
than the 290 pirad the human eye is capable of resolving. At 600 m, this minimum angular
separation amounts to 1.58 centimeters which is more than sufficient to identify tank sized
targets. Using this as a rough check, the lens diameter allocated should be suitable even
with 50% light transmission.
The disposable launcher concept also limits the optical quality (price) available.
Other disposable light antitank weapons, notably the LAW and the AT4 do not employ a
magnifying scope, i.e., their magnification is unity. A requirement of 3.5X with a 6 degree
FOV was imposed on the Shoulder-launched Multi-Purpose Assault Weapon (SMAW),
but this system utilized a reusable launcher with expensive optics. The SMAW was
designed for use against smaller bunker targets with an operational range of 750 meters.
The SRAW will engage tank-sized targets at 600 meters, but will also be required to
engage moving targets. Three gunner tasks detailed in the SRAW operational flow
42
diagrams are dependent upon the optical sight: acquiring the target within the optical
sight picture; identifying the target; and tracking moving/stationary targets. These gunner
tasks drive the sight requirements. Top level sight design requirements are the sight
magnification, field of view, and reticle pattern. Based on the previous research, a baseline
requirement of 2.5 X minimum magnification, 6 degree FOV, and a simple, cross-hair
reticle was written into the SRAW Prime Item Development Specification.
8.4 SRAW OPTICAL SIGHT HUMAN FACTORS REQUIREMENTS VERIFICATION
The delivery of a prototype launcher provided the SRAW program with a cost-
effective opportunity to verify the top level launcher requirements in the field and if
necessary, influence the design early in the life cycle. Four commercially available,
affordable ($50-100 retail price), 1-inch diameter design configurations were identified.
The test objective was to determine the combination of lens magnification and field of
view which provides the user with maximum ability to acquire, identify, and track moving
and stationary targets throughout the SRAW operational range. Table 4 presents the
optical sight configurations tested.
TABLE 4 - OPTICAL SIGHT TEST CONFIGURATIONS
SIGHT CONFIGURATION MAGNIFICATION | FIELD OF VIEW (FOV)
A 1.75 X 14° FOV
B 2.5 X 4.8° FOV
C 2.5 X 9° FOV
D 4.0 X 7? FOV
43
8.4.1 Test Procedure
Individual evaluation by prospective user (Marine).
Evaluate each scope configuration versus tank-size stationary targets.
Ranges: 17m; 100m; 250m; 600m
Evaluate each scope configuration versus tank-size moving target.
Ranges: 17m; 100m; 250 meters
Survey user response.
Stationary target ranges selected were: 17m (minimum range), 250m (typical
engagement), and 600m (maximum range). Likewise moving target ranges selected were:
17m (minimum range) and 250m (maximum range). Discussions with the SRAW
software/Guidance and Control (G&C) engineers, revealed that targets located at 100m
were most demanding upon the G&C system. As a result, the 100m test range was added
to both moving and stationary targets.
A temporary test range was established at NSWCDD along blacktop roads. A
laser rangefinder was used to mark accurate gunner firing positions. Four SRAW
prototype launchers, each equipped with one (1) of the Table 4 sight configurations were
available. A tank was not available, so a USMC Light Armored Vehicle, LAV-25 (77H x
8°’ W x 22’ L) was used as a representative target with no loss of validity. Figure 8.3
shows the LAV frontal and side aspects.
FIGURE 8.3 LAV-25 FRONTAL AND SIDE VIEW
44
Five US Marines with anti-tank weapon experience participated in this evaluation.
System Experience: LAW (4), AT4 (4), DRAGON (4), and TOW (2). Each participant
was asked to evaluate each optical sight configuration against the moving and stationary
targets at the ranges identified in Table 5. Note that only four gunners participated in the
moving target scenarios to save time.
TABLE 5 - TEST SCENARIOS
RANGE Stationary Side Stationary Frontal Moving, Crossing
(meters) View (SS) View (SF) Target (MC) 25km/hr
17 x xX x
100 xX xX xX 250 x x x 600 x x
The test participants employed the most difficult firing position, free standing,
unsupported. Each participant was given as much time as needed, was allowed to
evaluate the launcher configurations in any order, and was allowed to evaluate any given
configuration as many times as necessary.
The participants were instructed on the test objectives and were instructed to
concentrate upon the optical sight picture only. Variations in scope quality/position was
not to influence their evaluation. Strict instructions not to discuss opinions and
observations amongst themselves were also in force. After each test scenario, each
Marine met individually with a data collector and completed a questionnaire, included as
Figure 8.4. The group of test participants was debriefed at the conclusion of the test.
They were encouraged to speak freely and offer any and all comments they might want to
make.
45
FIGURE 8.4 - QUESTIONNAIRE
Experience with other anti-tank systems. (Check all that apply)
LAW . DRAGON AT4 SMAW
OTHER (Please specify):
CONSIDERING ONLY THE SCOPE MAGNIFICATION AND FIELD OF VIEW (i.e.,
your sight picture), PLEASE ANSWER THE FOLLOWING.
RANGE: Moving/Stationary (Circle One)
I. Ability to acquire and track target.
Preferred Configuration:
Unacceptable Configuration(s):
(Why?)
I. Ability to identify target.
Unacceptable Configuration(s):
(Why?)
POST-TEST SUMMARY
Overall, I felt FIELD OF VIEW/MAGNIFICATION to be more important. (Circle One).
Comments:
46
8.4.2 Test Results
The individual data are summarized in Table 6. A bar graph, Figure 8.5, illustrates
gunner preferences during the stationary side view testing. These preferences are the
gunner’s opinion of which configuration (A-D) presented the best optical sight picture for
a given range and target orientation. Note that some gunners preferred two
configurations during stationary side view testing. Hence the 0.5 split for these
configurations. Configuration C was clearly preferred throughout the testing. The Table
6 data shows the gunners unanimously preferred Configuration C for the stationary frontal
testing and the moving testing. Three of five gunners felt the 1.75 magnification of
configuration A was insufficient to identify (friend or foe) targets at 600 meters. The small
FOV of configuration B and D was unacceptable to these gunners. The high
magnification of configuration D was unacceptable for short range targets.
47
TABLE 6 - DATA SUMMARY
Stationary Target (Side View) Preferred Scope Configuration
Range A B "' C D Unacceptable Configurations: Comments
17m 1 3 2B:b, 3D:a,b
100m 1 3 1B:b, 4D:a
250m 0.5 * 4.5 * 1A:c, 1B:b, 3D:b(2)
600m 1 4 1A:c,d 1B:b
Stationary Target (Front View) Preferred Scope Configuration
Range A B C D Unacceptable
Configurations: Comments
17m 0.5 * 3.5 * 3D:a(2),b
100m 5 ID
250m 5 1B, 1D
600m 4 1 3A:c,d(2), 2B, 1C
Moving Target (Crossing) Preferred Scope Configuration
Range A B C D Unacceptable
Configurations: Comments
17m 4 1A,1B,2D 100m 4 2B:b(2)
250m 4 3B:b(2),1D
Notes: *: at least one participant rated B & C equally, and a value of 0.5 was assigned to each. 2 Reasons for unacceptable ratings:
a: magnification too great b: FOV too narrow
c: identification would be difficult, though not impossible d: magnification too low
Key: Number of Participants/Configuration: Reason for Unsat (# of times cited)
Example 1 2B:b(2) --> 2 Marines regarded Configuration B unacceptable,
both cited narrow FOV as the reason.
Example 2 3D:a,b --> 3 Marines regarded Configuration D unacceptable,
1 Marine cited magnification as too great; 1 Marine cited FOV too
narrow; 1 Marine did not provide a comment.
48
Figure 8.5 - Number Of Gunners Preferring Each Configuration
(Stationary Side View)
8.4.3 Verification Testing Debrief Summary
Participants agreed that a good combination of FOV/magnification was more
important than a single characteristic. The participants liked the wide angle 14° FOV at
short ranges. A 2.5 X scope was felt to be the minimum necessary for positive visual
identification at 600m. Ideally, the Marines would have chosen a 2.5 X scope with a 14°
FOV. While possible, this would likely be a very large and expensive scope unsuitable to
the requirements. The preferred test configuration C, was 2.5 X, 9° FOV. No negative
comments on the reticle pattern were offered by the participants.
8.4.4 Verifications Test Conclusions and Recommendations
The verification testing illustrates one iteration of the system development process.
The current 6° FOV specified in the SRAW Prime Item Development Specifications was
judged inadequate. A 2.5 X scope with a 9° FOV and simple reticle pattern was preferred
49
by the survey participants. The SRAW Prime Item Development Specifications should be
changed to reflect a 9° FOV. The other baseline optical sight characteristics were
acceptable to the participants. This requirement change will improve the effectiveness of
the SRAW gunner, especially at close range.
9.0 CONCLUSIONS
The top-level system requirements for SRAW are based on a 1950’s era systems
engineering study. The mission requirements and deployment doctrine are inadequate.
The systems engineering approach applied to the SRAW system revealed a design capable
of meeting the stated USMC needs. The SRAW requirements have been allocated
appropriately to the system reliability, weight, and fiscal constraints. The Life Cycle Cost
analysis illustrates the benefits of the reduced operating costs associated with maintenance
and spare parts inventory. Application of the systems engineering process to the optical
sight resulted in improved performance within constraints prior to the FY98 production
cost ramp-up. Other SRAW human factors issues need to be examined in the same detail.
10.0 RECOMMENDATIONS FOR FURTHER STUDY
A complete human factors evaluation of the launcher should be completed as soon
as possible studying man-portability and confirming ease of use for the Sth to 95th
percentile gunners in protective clothing. The USMC top level anti-tank organization,
doctrine, and tactics first allocated in the 1950’s should be reviewed with a view toward
the changed threat and technology levels. Significant improvements could result from a
willingness to reexamine the paradigm of organizing infantry anti-tank assets into light,
medium, and heavy systems.
50
Additional human factors testing with one inch diameter, 2.5 X scopes should be
conducted to determine an optimal field of view for this application. Testing 6, 9, 12, 15,
and 18 degree FOVs is recommended as a staring point. Testing should ideally employ
simulators to confirm and quantify the relationship between gunner preference and gunner
accuracy. The low light limits for the optical daysight should be studied further and
incorporated into the gunner training manual as guidance for when to switch to the night
sight. Human factors testing on the SRAW to nightsight interface should be conducted.
The operator and maintenance functions derived from the functional analysis should be
verified and expanded with a detailed operator task analysis. The SRAW System should
be continually reviewed throughout the life cycle for areas where evolving technology,
changing threats, or procurement reform could impact acquisition cost.
51
REFERENCES
' Moskin, J. Robert, The USMC Story, 3rd. ed., (New York, NY: Little, Brown
and Company 1992), p. 445.
? Ibid., p. 773.
* D.J Giodano, Gunner Errors When Using the M72A2 LAW Sight TM-19/75. (Aberdeen, MD: US Army Human Engineering Laboratory [August 1975]), p. 3-5.
* J. Weeks, ed., Jane’s Infantry Weapons, 6th edition, (London, UK: Jane’s
Publishing Co., 1981), p. 546
°D.J Giodano, Simplified Procedures for Engaging Moving Targets with the M72A2 LAW TM-28/76. (Aberdeen, MD: US Army Human Engineering Laboratory
[Nov 1976]), p. 19.
° D.J Giodano_ Sights for Light Antitank Weapons TM-11/76. (Aberdeen, MD: US Army Human Engineering Laboratory [April 1976]), p. 121.
”U.S. Department of Defense, MIL-HDBK-759A - Handbook for Human
Engineering Design Guidelines (Washington, DC: 30 June 1981), p. 7-47.
® W.E. Woodson, Human Factors Design Handbook. (New York, NY: McGraw-
Hill Book Co., 1981), p. 556.
” J. B. Marion and W. F. Hornyak, Physics for Science and Engineering. (New York, NY: Saunders College Publishing (1982), p. 1145.
52
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Blanchard, B. S. and Fabrycky, W. J. Systems Engineering and Analysis, 2nd ed.
New York, NY: Prentice Hall, 1990.
Cartereete, E. and Friedman, M., eds., Handbook of Perception Volume V - Seeing. New York, NY: Academic Press, Inc., 1975.
Giodano, D. J., Gunner Errors When Using the M72A2 LAW Sight TM-19/75.
Aberdeen, MD: US Army Human Engineering Laboratory [August 1975].
Giodano, D. J., Sights for Light Antitank Weapons TM-11/76.
Aberdeen, MD: US Army Human Engineering Laboratory [April 1976].
Giodano, D. J., Simplified Procedures for Engaging Moving Targets with the M72A2
LAW TM-28/76. Aberdeen, MD: US Army Human Engineering Laboratory [April 1976].
Kennedy, D. R., History of the Shaped Charge Effect, the First 100 Years,
Mountain View, CA: D.R. Kennedy & Associates, Inc., 1988.
Korchunoff, K., “Initial Human Engineering Test Report”, prepared under contract
N60921-94-C-A132, Rancho Santa Margarita, CA: Loral Aeronutronic, 6 July
1995.
Marion, J. B. and Hornyak W.F., Physics for Science and Engineering.
New York, NY: Saunders College Publishing , 1982.
Moskin, J. Robert, The USMC Story, 3rd. ed.,
New York, NY: Little, Brown and Company 1992.
Spillman, L. and Werner, J., eds., Visual Perception: The Neurophysiological —
Foundations, New York, NY Academic Press, 1990.
Tortora, G. and Anagnostakos, N., Principles of Anatomy and Physiology, 5th ed.
New York, NY: Harper & Row, 1987.
Walters, W. P. and Zukas, J. A., Fundamentals of Shaped Charges, New York, NY: John Wiley & Sons, Inc., 1989.
Weeks, J., Ed., Jane’s Infantry Weapons, 6th edition, London Jane’s Publishing Co., 1981.
53
Woodson, W.E., Human Factors Design Handbook, New York, NY: McGraw-Hill, 1981.
SRAW Prime Item Development Specification (PIDS), WS-33126, Rev A, 8 Feb 94.
MIL-STD-210C, Climatic Information to Determine Design and Test Requirements for Military Systems and Equipment. |
MIL-STD-810, Environmental Test Methods.
MIL-HDBK-759A - Handbook for Human Engineering Design Guidelines
MTD TOP 3-2-045, US Army Test and Evaluation Command, Test Operations Procedure, “Automatic Weapons, Machine Guns, Hand and Shoulder Weapons”.
54