Mk 118 Mod 0 Rockeye Anti-Armor Bomblet
1. Overview
The Mk 118 Mod 0 is an air-delivered anti-armor submunition designed to penetrate armored vehicles and hardened targets through a shaped charge warhead. As the payload of the CBU-100 Rockeye II cluster bomb system, the Mk 118 represents one of the earliest purpose-built anti-armor cluster munitions widely deployed by US and allied forces. The Rockeye system was specifically designed to engage armored formations from the air, filling a critical tactical gap in the air-to-ground anti-armor mission.
2. Country/Bloc of Origin
- Country: United States of America
- Developer: US Naval Weapons Center, China Lake
- Development Period: 1960s
- Service Entry: 1968
- International Users: United States, numerous NATO allies, and other nations
The Mk 118/Rockeye system was developed during the Vietnam War era as the US military sought effective air-delivered weapons against armored targets and fortifications.
3. Ordnance Class
| Attribute | Classification |
|---|---|
| Type | Submunition / Bomblet |
| Role | Anti-Armor / Anti-Materiel |
| Delivery Method | Air-delivered via dispenser (CBU-100) |
| Category | Cluster Munition Submunition |
| Target Types | Tanks, armored vehicles, fortifications, equipment |
The Mk 118 is classified primarily as an anti-armor submunition, though its fragmentation effects also provide anti-personnel and anti-materiel capability.
4. Ordnance Family / Nomenclature
Primary Designation:
- Mk 118 Mod 0 (Bomblet)
- Mk 118 Mod 1 (Minor improvements)
Parent Systems:
- CBU-100 Rockeye II – Standard dispenser containing 247 Mk 118 bomblets
- CBU-99 – Earlier Rockeye variant
- CBU-59 APAM – Anti-Personnel/Anti-Materiel variant (different submunition)
Related Munitions:
- BLU-97/B – Later combined effects submunition (replaced Rockeye for some missions)
- BLU-108/B – Smart anti-armor submunition (CBU-97 SFW)
- Mk 20 Mod 0-6 – Dispenser designations for various Rockeye variants
NATO Stock Number (NSN): 1325-00-147-4399 (Mk 118 Mod 0)
Common Names:
- Rockeye Bomblet
- Rockeye Anti-Armor Bomblet
- “Rock” (shortened nickname)
5. Hazards
Primary Hazards
| Hazard Type | Description |
|---|---|
| Shaped Charge | High-velocity copper jet for armor penetration |
| Fragmentation | Steel body fragments upon detonation |
| Spall | Secondary fragments from penetrated armor |
Shaped Charge Lethality
The Mk 118’s primary kill mechanism:
- Impact initiates shaped charge
- Copper liner collapses into high-velocity jet (~8 km/s)
- Jet penetrates armor through hydrodynamic forces
- Behind-armor effects include spall, fire, and crew casualties
Sensitivity Factors
- Impact Fuze: All-ways acting piezoelectric fuze
- Dud Rate: Significant dud rates documented (varies with conditions)
- Fuze Sensitivity: Armed duds may function on disturbance
- Standoff Requirement: Shaped charge requires proper standoff for penetration
Safety Considerations
- High Explosive Content: Significant blast and fragmentation hazard
- Shaped Charge Jet: Can penetrate walls, vehicles, and other barriers
- UXO Persistence: Duds may remain hazardous for decades
- Small Size: Can be picked up, especially by children
- Partial Burial: May be concealed in soft ground or debris
Kill/Danger Radius
| Zone | Distance | Effect |
|---|---|---|
| Lethal Radius | ~8-10 meters | Fatal injuries from fragmentation |
| Casualty Radius | ~15-20 meters | Significant injury risk |
| Shaped Charge Effect | Direct hit required | Armor penetration |
| Pattern Coverage | ~40,000 sq meters | Full CBU-100 dispersion |
| Safety Distance | Minimum 50 meters | From individual dud |
⚠️ WARNING: Mk 118 submunitions contain a shaped charge warhead capable of penetrating armor and structural materials. Unexploded bomblets are extremely dangerous and may detonate if touched, moved, or disturbed. The all-ways acting fuze functions at any impact angle.
6. Key Identification Features
Physical Characteristics
| Dimension | Measurement |
|---|---|
| Length | Approximately 11.4 cm (4.5 inches) |
| Diameter | Approximately 6.4 cm (2.5 inches) |
| Weight | Approximately 600 grams (1.32 lbs) |
Visual Identification
- Shape: Cylindrical body with distinctive conical nose and tail fins
- Color: Olive drab (OD) green body, often with yellow markings
- Markings: Yellow band indicating HE content; nomenclature stenciled
- Material: Steel body with copper shaped charge liner
- Distinctive Features:
- Pronounced conical nose (shaped charge)
- Rigid tail fin assembly (four fins)
- Larger than many other submunitions
- Visible copper liner if nose damaged
Tail Fin Assembly
The Mk 118 uses fixed, rigid tail fins for stabilization:
- Four stabilization fins arranged in cruciform pattern
- Fins are fixed (not pop-out/deployable)
- Orient bomblet for nose-down impact
- Provide spin stabilization during descent
- Fins may be bent or damaged on impact
Construction Details
| Component | Material | Function |
|---|---|---|
| Body | Steel | Fragmentation case |
| Nose | Steel with copper liner | Shaped charge assembly |
| Fins | Aluminum or steel | Aerodynamic stabilization |
| Explosive | Composition B or similar | Main charge |
Condition Indicators
| State | Visual Indicators |
|---|---|
| Intact Dud | Complete body, fins intact, nose undamaged |
| Partial Function | Damaged body, incomplete fragmentation |
| Post-Detonation | Fragmented remains, crater, scoring |
| Buried | Fins or partial body protruding from ground |
Comparison with Similar Submunitions
| Characteristic | Mk 118 | BLU-97/B |
|---|---|---|
| Length | 11.4 cm | 20 cm |
| Diameter | 6.4 cm | 6.1 cm |
| Weight | 600g | 1.5 kg |
| Color | OD Green | Yellow |
| Tail | Fixed fins | Scissor pop-out fins |
| Primary Role | Anti-armor | Combined effects |
7. Fuzing Mechanisms
Primary Fuze System
The Mk 118 employs an all-ways acting piezoelectric impact fuze:
| Component | Function |
|---|---|
| Piezoelectric Element | Generates firing current on impact |
| All-Ways Acting Assembly | Enables function at various impact angles |
| Firing Circuit | Initiates detonator |
| Detonator | Primary explosive to booster |
| Booster | Amplifies initiation to main charge |
Arming Sequence
- Release: Dispenser opens, ejecting submunitions
- Fin Stabilization: Tail fins orient bomblet nose-down
- Descent: Bomblet descends through target area
- Arming: Setback/spin during descent arms fuze
- Impact: Piezoelectric element generates current
- Detonation: Firing train initiates shaped charge
Safety Mechanisms
- Setback Safety: Requires ejection acceleration
- Arming Wire: May be used in some variants
- Spin Arming: Rotation contributes to arming sequence
- Environmental Sealing: Protects fuze components
All-Ways Acting Fuze Design
The AWA fuze ensures reliable function:
- Functions regardless of impact angle
- Shaped charge effectiveness varies with angle, but fuze will fire
- Critical for area weapons with varied impact geometries
- Multiple paths to firing pin strike
Piezoelectric Operation
Self-generating electrical fuze:
- No battery required
- Impact compresses piezoelectric crystal
- Crystal generates electrical current
- Current fires electrical detonator
- Extremely reliable when functional
Dud Causes
| Cause | Description |
|---|---|
| Soft Ground | Impact cushioned; fuze fails to function |
| Vegetation | Foliage absorbs impact |
| Water | Landing in water bodies |
| Fuze Defect | Manufacturing or degradation |
| Orientation | Extreme angles beyond AWA capability |
| Low Release | Insufficient arming time |
8. History of Development and Use
Development Background
The Rockeye system was developed during the 1960s in response to the need for effective air-delivered anti-armor weapons. Conventional bombs were inefficient against dispersed armored targets, and the emerging threat of massed Soviet armor in Europe required a solution that could engage multiple vehicles per sortie.
Development Timeline
| Year | Event |
|---|---|
| 1960s | Development at Naval Weapons Center, China Lake |
| 1968 | CBU-99/Mk 118 enters service |
| 1970s | Improved CBU-100 Rockeye II fielded |
| 1980s | Widespread use in training and stockpiling |
| 1991 | Extensive combat use in Gulf War |
| 1999 | Used in Kosovo operations |
| 2003 | Employed in Iraq War |
| 2008 | Convention on Cluster Munitions (US did not sign) |
Design Philosophy
The Rockeye concept emphasized:
- Anti-armor focus: Shaped charge optimized for vehicle defeat
- Area coverage: Multiple bomblets vs. single bomb
- Aircraft survivability: One pass engagement
- Target flexibility: Effective against varied hard targets
Combat Employment
Vietnam War (limited use): Early Rockeye variants used against vehicles and fortifications.
Operation Desert Storm (1991): Extensive Rockeye employment against Iraqi armor:
- Armored formations engaged during air campaign
- Iraqi defensive positions attacked
- Significant effectiveness against parked/dug-in vehicles
- Notable dud problems in soft desert sand
Kosovo (1999): NATO forces employed Rockeye against Serbian military targets:
- Armored vehicles and artillery positions
- Post-conflict UXO clearance challenges
Operation Iraqi Freedom (2003): Continued use against military targets:
- Employed from US Navy and Marine Corps aircraft
- Urban proximity created controversy
- UXO concerns in populated areas
Effectiveness Assessment
| Target Type | Effectiveness |
|---|---|
| Tanks (top attack) | Moderate to High |
| APCs/IFVs | High |
| Artillery/SP guns | High |
| Trucks/soft vehicles | Effective |
| Fortifications | Moderate |
| Personnel | Secondary effect |
International Restrictions
The Mk 118/Rockeye system faces international scrutiny:
- 2008 Convention on Cluster Munitions: Bans cluster munitions for signatories
- US Position: Did not sign CCM; retains Rockeye capability
- Allied Nations: Many NATO allies have ratified CCM, cannot use Rockeye
Current Status
- Mk 118/CBU-100 remains in US inventory
- Subject to policy restrictions on use
- Largely superseded by precision-guided munitions
- Retained for specific anti-armor scenarios
- Extensive UXO remains in previous conflict areas
9. Technical Specifications
Explosive Content
| Specification | Detail |
|---|---|
| Main Charge | Composition B |
| Charge Weight | Approximately 185 grams (6.5 oz) |
| Shaped Charge Liner | Copper |
| Total Weight | 600 grams |
Warhead Effects
| Effect Type | Capability |
|---|---|
| Shaped Charge Penetration | ~190mm (7.5 inches) RHA at optimal angle |
| Fragmentation | Steel body produces high-velocity fragments |
| Behind-Armor Effects | Spall, fire, crew casualties |
Performance Characteristics
| Specification | Detail |
|---|---|
| Armor Penetration | 190mm Rolled Homogeneous Armor (optimal) |
| Effective Against | MBT top armor, APCs, IFVs, fortifications |
| Function Mode | Impact (piezoelectric AWA) |
| Stabilization | Fixed tail fins |
| Optimal Impact Angle | Near-perpendicular for maximum penetration |
CBU-100 Dispenser Configuration
| Specification | Value |
|---|---|
| Submunitions | 247 Mk 118 bomblets |
| Dispenser Weight | ~222 kg (489 lbs) |
| Dispenser Length | 2.34 meters (92 inches) |
| Coverage Area | ~40,000 sq meters |
| Release Altitude | Varies (affects pattern) |
Delivery Parameters
| Parameter | Typical Value |
|---|---|
| Release Altitude | 500-3,000 feet |
| Aircraft Speed | 350-550 knots |
| Dispenser Opening | Timer or altitude triggered |
| Pattern Shape | Elliptical (varies with parameters) |
10. Frequently Asked Questions
Q: How does the Mk 118 achieve its 190mm armor penetration? A: The Mk 118 uses a shaped charge (also called Monroe effect or HEAT) warhead. Upon detonation, the copper liner collapses inward, forming a superplastic jet traveling at approximately 8 km/s. This jet penetrates armor through hydrodynamic forces—at these velocities, both the jet and armor behave like fluids. The 190mm penetration figure represents optimal conditions (perpendicular impact, proper standoff distance). Real-world penetration varies with impact angle; angled impacts significantly reduce effectiveness as the jet must travel through more armor material.
Q: Why was Rockeye designed specifically as an anti-armor weapon rather than a combined-effects weapon like the BLU-97? A: Rockeye was developed in the 1960s when the primary concern was defeating massed Soviet armor—the anti-armor mission drove the design. The larger shaped charge and heavier construction optimized armor penetration at the expense of submunition count per dispenser. Later combined-effects munitions like the BLU-97 reflected evolved doctrine emphasizing multi-role capability against diverse target sets (personnel, light armor, materiel, POL sites). The Rockeye’s anti-armor specialization made it highly effective against its intended targets but less versatile than successor systems.
Q: What factors affect Mk 118 dud rates in combat conditions? A: Multiple factors influence dud rates: ground conditions are paramount—soft sand, mud, deep snow, and water can cushion impact and prevent fuze function; vegetation can similarly absorb impact energy; release altitude affects arming time and impact velocity; aircraft speed and dive angle influence impact dynamics; environmental conditions (temperature, humidity) affect fuze components; manufacturing lot variations create quality differences; and age-related degradation of stockpiled munitions reduces reliability. Gulf War experience showed higher dud rates in soft desert sand than expected from testing on hard-packed ranges.
Q: How effective is the Mk 118 against modern main battle tanks with reactive armor? A: Modern tank protection significantly complicates Mk 118 effectiveness. Explosive reactive armor (ERA) can disrupt the shaped charge jet, substantially reducing penetration. Composite armor arrays provide enhanced protection compared to equivalent RHA thickness. However, the Mk 118’s top-attack delivery mode targets the relatively thin roof armor, which often lacks ERA coverage. Against tank turret tops (typically 40-80mm), the 190mm penetration remains effective unless active protection systems intercept the bomblet. The Mk 118 remains highly effective against older tanks and lighter armored vehicles.
Q: Why doesn’t the Mk 118 use pop-out fins like some other submunitions? A: The Mk 118 uses fixed tail fins because it was designed in the 1960s when simpler, more robust mechanisms were preferred. Fixed fins provide reliable stabilization without deployment mechanisms that can fail. The trade-off is increased dispenser volume—fixed fins require more space than folded fins. Later submunitions like the BLU-97 use pop-out scissor fins to achieve denser packing. The fixed fin design is mechanically simpler and was proven effective, so it was retained through Rockeye’s production life.
Q: How does the CBU-100 dispenser distribute the Mk 118 bomblets? A: The CBU-100 is a clamshell-type dispenser that opens at a preset time or altitude after release, separating into halves and ejecting all 247 bomblets. The bomblets spread in an expanding pattern as they descend, creating an elliptical “footprint” on the ground. Pattern size and density depend on release altitude (higher releases create larger, less dense patterns), aircraft speed (faster speeds elongate the pattern), dispenser opening height, and wind conditions. Pilots select delivery parameters based on target characteristics and desired effects.
Q: What was the typical tactical employment of Rockeye in the Gulf War? A: During Desert Storm, Rockeye was employed primarily against Iraqi armored and mechanized units: static defensive positions where tanks and APCs were dug in; moving armored columns during the ground campaign; artillery and air defense positions; and logistical/support areas with vehicle concentrations. Attack profiles typically involved diving or shallow-angle deliveries to optimize bomblet pattern over the target. Multiple aircraft often attacked the same target area to ensure coverage. The weapon was particularly effective against vehicles that couldn’t maneuver to escape the bomblet pattern.
Q: How do EOD teams approach areas contaminated with Mk 118 duds? A: Clearance of Mk 118-contaminated areas follows systematic procedures: establish area boundaries based on delivery information and visual reconnaissance; conduct careful visual search for surface bomblets and impact indicators (craters, fragments); use metal detection to locate buried bomblets; document and mark each item’s location; destroy bomblets in place using explosive charges or render-safe procedures—never attempt to move armed duds; conduct thorough resurvey after initial clearance; and may require multiple passes over extended periods. The shaped charge warhead’s armor-penetration capability means standard cover provides less protection than with fragment-only munitions.
This document is for educational and training purposes only. All ordnance should be treated as dangerous until rendered safe by qualified EOD personnel. Never attempt to handle, move, or disturb any suspected explosive ordnance.