BLU-24/B Fragmentation Submunition Family
1. Overview
The BLU-24/B series represents the United States’ primary fragmentation submunition design deployed during the Vietnam War and beyond. Commonly referred to as the “Orange” bomblet due to its distinctive orange-painted steel body and streamlined profile, the BLU-24 family served as an area denial and anti-personnel weapon dispersed via cluster bomb dispensers. The submunitions employ impact-detonated fuzing and generate lethal fragmentation through embedded steel ball bearings distributed throughout the casing. The design prioritizes reliability and manufacturing simplicity while maintaining consistent fragmentation patterns across dispersed area targets.
2. Country/Bloc of Origin
| Attribute | Details |
|---|---|
| Country | United States of America |
| Developer | Ordnance/Munitions Development Command, US Navy |
| Development Period | 1960–1962 |
| Production Period | 1962–1990s (continuous with variants) |
| International Users | Australia, South Korea, South Vietnam (during war), Thailand, Turkey, Israel, several Gulf Cooperation Council states |
| Status | Largely phased out of US inventory; remaining stocks managed under demilitarization protocols |
3. Ordnance Class
| Attribute | Classification |
|---|---|
| Type | Submunition (bomblet) |
| Role | Anti-Personnel, Area Denial |
| Delivery Method | Cluster Bomb Unit (CBU) dispenser, rocket-assisted or gravity |
| Category | Unguided, scatter weapon system |
| Target Types | Personnel in the open, soft-skinned vehicles, light structures, materiel in open storage |
4. Ordnance Family / Nomenclature
Primary Variants:
- BLU-24/B (early model): Initial production configuration, 1960s introduction. Smooth cylindrical body with four drag fins welded to rear section.
- BLU-24/B (late model): Refined version with improved consistency in fragmentation and fuzing reliability. Distinguishable by subtle differences in fin attachment and body finish.
- BLU-24B/B: Mid-generation variant with modest improvements to fuzing mechanism and internal fill consistency.
- BLU-24C/B: Later variant representing final refinements in the design lineage before transition to newer submunition types.
Parent Systems:
- SUU-30 Dispenser (primary carrier): Used in CBU-29, CBU-41 cluster bomb units
- CBU-1 through CBU-27: Various cluster configurations
- CBU-29 Cluster Bomb Unit: Vietnam-era standard
- CBU-41 Cluster Bomb Unit: Extended deployment variant
Related Munitions:
- BLU-18/B (alternative fragmentation design, smaller scale)
- BLU-4A/B (compact fragmentation, “Pineapple” bomblet)
- Mark 118 Rockeye (Navy variant, shaped-charge anti-armor)
Common Names:
- “Orange Bomblet” (color designation)
- “Orange Cluster Bombs” (container reference)
- “CBU-29 submunition” (system reference)
- “Rockeye-type” (generic reference to family lineage)
5. Hazards
Primary Hazards
Impact Detonation Sensitivity:
- Submunitions are armed upon separation from dispenser (typically 1,000–2,000 feet AGL minimum safe altitude requirement).
- Impact detonation remains extremely sensitive. Minimal force required for initiation—estimated 2–5 G impact forces sufficient for reliable detonation.
- Submunitions scattered over terrain with variable ground hardness will produce unpredictable fuzing behavior; some may arm and detonate on minimal contact (rocks, hard earth), while others may fail to detonate on soft ground (sand, mud, vegetation).
- Failed detonations result in armed submunitions remaining hazardous indefinitely.
Fragmentation and Blast Effects:
- Steel ball bearings (typically 200–350 per unit, 3–4 mm diameter) embedded throughout casing generate lethal fragmentation cone.
- Primary fragmentation hazard extends 15–25 meters from detonation point with high lethality out to 10 meters.
- Explosive charge (typically 0.3–0.5 lbs TNT equivalent) generates blast overpressure capable of injuring personnel at extended range.
- Secondary fragmentation (casing rupture) creates unpredictable secondary missiles.
Sympathetic Detonation:
- Clustered failed submunitions pose risk of sympathetic detonation if any initiating event disturbs the ground area (secondary explosions).
- Movement or disturbance of scattered submunitions can trigger adjacent armed munitions.
Corrosion and Deterioration:
- Steel bodies subject to corrosion in tropical or maritime environments (Vietnam deployment experience showed accelerated deterioration).
- Corrosion can compromise structural integrity and alter fuzing behavior.
- Long-term environmental exposure (20–30+ years) creates unpredictable detonation sensitivity.
Hazard Classification Table
| Hazard Type | Severity | Range | Notes |
|---|---|---|---|
| Impact detonation | Extreme | Contact–5m | Highly sensitive; minimal triggering force |
| Fragmentation | Extreme | 0–25m | Steel balls + casing fragments; lethal to 15m |
| Blast overpressure | High | 0–20m | Injury and structural damage |
| Sympathetic detonation | High | Area dependent | Risk when clustered UXO disturbed |
| Chemical (aged fill) | Moderate | Unit area | Residual explosive degradation |
| Environmental hazard | Moderate | Local | Corrosion, contamination, unstable detonation |
6. Key Identification Features
Physical Characteristics Table
| Feature | Specification |
|---|---|
| Overall Length | 10.2–10.8 inches (260–275 mm) |
| Maximum Diameter | 2.5–2.75 inches (64–70 mm) |
| Weight | 1.3–1.6 lbs (590–725 grams) |
| Body Material | SAE 1020–1030 steel, typically painted |
| Color | Orange or orange-yellow (standard livery) |
| Tail Assembly | Four stamped steel drag fins, aft-welded |
| Nose Section | Slightly domed, no nose fuze cavity (impact fuze internal) |
| Marking | Stenciled nomenclature on body; lot number and date coding |
| Explosive Fill | ~0.3–0.5 lbs TNT or RDX/TNT mixture |
| Fragmentation | ~200–350 steel ball bearings, 3–4 mm diameter, embedded throughout |
Visual Identification
Distinctive Features:
- Orange body color: The orange paint (standard US ordnance color for fragmentation submunitions) is the defining visual characteristic. Early models may show fading or discoloration in field conditions.
- Cylindrical profile: Smooth, slightly tapered body with continuous lateral surface. No prominent ridges or segmentation (unlike some armored fragmentation designs).
- Four drag fins: Positioned at 90-degree intervals around the rear third of the body. Fins are small (1–1.5 inches tall), streamlined, and welded flush to the casing.
- Nose dome: Slightly rounded nose without visible fuze well or detonator cavity. Fuzing mechanism is entirely internal.
- Marking conventions: Manufacturer codes, nomenclature (BLU-24/B or variants), date code, lot number typically stenciled in black or white paint on body surface.
Comparison Features
| Feature | BLU-24/B Early | BLU-24/B Late | BLU-24C/B |
|---|---|---|---|
| Body finish | Rougher, more porous | Smoother, more uniform | Polished, consistent |
| Fin attachment | Welded, visible bead | Welded, refined | Integral/welded, seamless |
| Fuze mounting | Internal, early design | Internal, refined | Internal, latest design |
| Fragmentation pattern | Variable | Consistent | Optimized distribution |
| Nose profile | Slightly pointed | Rounded dome | Rounded dome (refined) |
Hazard Recognition
Armed Status Indicators:
- Separated from dispenser and exposed to air: likely armed.
- Presence of arming wire or fuze shear pin removed: armed.
- Undisturbed position in open field or terrain: assume armed.
Unarmed Conditions (rare):
- Still attached to or partially engaged with dispenser: may be inert during manufacturing or transport.
- Associated with clearly marked inert range or training operation: treat with skepticism unless documented.
7. Fuzing Mechanisms
Fuze Type and Design
Impact Fuze (Internal):
- Fuzing is entirely internal; no external fuze well or obvious detonator cavity exists.
- Fuze design consists of inertial-type detonation train: impact initiator → booster → main charge relay.
- Specific fuzing mechanism likely employs a spring-loaded firing pin or inertial switch that strikes a percussion-sensitive element upon sudden deceleration from impact.
- Fuze is direct-action with no delay or air-burst capability.
Arming Sequence
- Pre-Release (In Dispenser): Submunitions in dispenser are in safe condition, fuzes secured against inadvertent initiation.
- Separation from Dispenser: Submunitions tumble and separate from parent container at altitude (typically 500–2,000 feet AGL). Arming mechanism is either:
- Barometric arming: Fuze arm as internal pressure or aneroid mechanism resets after separation.
- Setback arming: Fuze deactivate-lock released by reduced G-forces upon dispenser deployment.
- Free Fall: Armed submunitions descend with tumbling motion, drag fins providing stability.
- Ground Impact: Contact with terrain at impact sensitivity threshold (~2–5 G) triggers detonation train.
Safety Mechanisms
Limited Internal Safeguards:
- Early BLU-24/B models have minimal redundancy in arming logic.
- Fuze design assumes proper dispenser separation and altitude control.
- No redundant fuze or backup safety mechanism in standard configuration.
- Self-destruct or self-neutralization capability: limited or absent in early variants.
Operational Safety Dependency:
- Safe employment relies entirely on correct dispenser operation and deployment parameters (altitude, aircraft speed, release sequencing).
- If dispenser malfunctions or release occurs at lower altitude, submunitions may not properly arm or may impact while partially armed.
Known Fuzing Issues
- Cluster failures: Documented instances of submunitions failing to detonate on impact, resulting in armed unexploded ordnance.
- Sympathetic detonation: Multiple submunitions in close proximity can trigger cascade detonations if one is disturbed.
- Environmental sensitivity: Age and environmental degradation can alter fuzing sensitivity over decades; field-aged munitions show inconsistent detonation behavior.
8. History of Development and Use
Development Timeline
| Period | Event |
|---|---|
| 1960–1962 | Development and initial testing of BLU-24/B design by Naval Ordnance Station (Indianhead, MD) and supporting contractors. Design prioritizes ease of manufacturing and reliability in cluster dispenser. |
| 1963–1965 | Production ramping and integration into CBU-29 and early cluster bomb variants. First deployments with US Navy and Air Force. |
| 1965–1973 | Extensive combat deployment in Southeast Asia (Vietnam, Laos, Cambodia). Hundreds of millions of submunitions dispersed. Becomes standard anti-personnel weapon for area denial missions. |
| 1973–1980s | Continued production and inventory expansion. Deployment in Middle East and other contingency areas. Variants (BLU-24B/B, BLU-24C/B) introduced with incremental improvements. |
| 1980s–1990s | Production phased out as newer submunition designs (CBU-87 with BLU-97, sensor-equipped variants) enter service. Remaining stocks managed under protocols. |
| 1990s–Present | Demilitarization and stockpile reduction programs. International proliferation controlled under Cluster Munitions Convention discussions. |
Combat Employment History
Vietnam War (1965–1973):
- Deployed extensively by US Navy carrier aircraft and Air Force fighter-bombers.
- Used in rolling thunder campaign and tactical air support missions.
- Effective against dispersed personnel and light materiel targets.
- High usage in Laos and Cambodia resulted in massive unexploded ordnance contamination.
- Documented civilian casualties and long-term ordnance hazard legacy.
Middle East Operations (1970s–1980s):
- Limited deployment in support of allied operations.
- Israel employed variants in Yom Kippur War and subsequent operations.
- Turkey and other regional allies maintained inventories.
Modern Conflicts (1990s–2000s):
- Phased out of primary US inventory; replaced by advanced submunition designs.
- Some stocks remained in reserve status through 1990s.
- International treaty restrictions (Cluster Munitions Convention, 2008) restricted further production and use by signatory nations.
Current Status
- US Military: Phased out of active inventory; remaining stocks subject to demilitarization.
- Allied Nations: Selective retention for training or reserve purposes; most NATO allies transitioned to alternative designs.
- International: Proliferation concerns remain in regions with historical US/allied operations; unexploded ordnance presents ongoing humanitarian challenge in Southeast Asia (millions of submunitions remain in Laotian and Cambodian soils).
- Treaty Status: US is not signatory to Cluster Munitions Convention but has voluntarily phased out BLU-24 and similar cluster munitions from active inventory.
9. Technical Specifications
Dimensional and Weight Data
| Parameter | Value |
|---|---|
| Overall Length | 10.2–10.8 inches (260–275 mm) |
| Maximum Body Diameter | 2.5–2.75 inches (64–70 mm) |
| Fin Height (extended) | 1.0–1.5 inches (25–40 mm) |
| Total Weight | 1.3–1.6 lbs (590–725 grams) |
| Weight (warhead only) | 0.8–1.1 lbs (360–500 grams) |
| Tail Assembly Weight | 0.2–0.3 lbs (90–140 grams) |
Explosive Fill Specifications
| Component | Specification |
|---|---|
| Primary Charge | TNT or RDX/TNT mixture |
| Charge Weight | 0.3–0.5 lbs (135–225 grams) TNT equivalent |
| Booster Configuration | Integral or separate booster pellet |
| Detonation Velocity | ~6,500–7,200 m/s (estimated for TNT fill) |
Fragmentation Payload
| Parameter | Value |
|---|---|
| Fragmentation Type | Steel ball bearings |
| Ball Diameter | 3–4 mm (0.12–0.16 inches) |
| Approximate Quantity | 200–350 balls per submunition |
| Total Fragmentation Mass | 0.3–0.5 lbs per unit |
| Velocity (at detonation) | ~1,200–1,500 m/s (estimated) |
Performance Characteristics
Dispersion Pattern:
- Dispersed submunitions scatter over elliptical or irregular area dependent on altitude, aircraft speed, and wind conditions.
- Standard dispenser (SUU-30) releases submunitions at approximately 50–100 feet per second relative velocity.
- Tumbling descent with drag fin stabilization provides moderate cross-sectional area for wind effects.
- Typical ground spread: 300–1,000 meters long by 100–300 meters wide, depending on deployment parameters.
Detonation Characteristics:
- Direct impact (contact) detonation with no discernible delay.
- Detonation occurs on impact with terrain hardness threshold of approximately 2–5 G.
- Soft ground (mud, sand, tall grass) may result in partial detonation or failure to detonate (UXO).
- Hard surfaces (rock, concrete, hardpan) reliably detonate.
Blast and Fragmentation Effects:
- Blast radius (primary injury potential): 0–20 meters.
- Fragmentation lethality (steel balls): 0–15 meters (high probability of injury).
- Fragmentation significant injury: 15–25 meters.
- Blast overpressure capable of collapse of light structures (mud, straw construction) to 10–15 meters.
Environmental Tolerance
- Temperature Range: -40°F to +160°F (-40°C to +71°C) for safe storage and operation.
- Humidity: No specific vulnerability; steel casing resists moisture initially but subject to corrosion over extended field exposure.
- Vibration Tolerance: Limited; transport handling may inadvertently initiate poorly-armed submunitions.
- Storage Stability: TNT-based fill stable for 20+ years under proper storage conditions; field-exposed munitions show degradation after 5–10 years.
10. Frequently Asked Questions
Q: How can I distinguish a BLU-24/B from other fragmentation submunitions in the field?
A: The BLU-24/B is most easily identified by its distinctive orange body color and small four-fin tail assembly. The smooth cylindrical body with no segmentation, combined with the domed nose and lack of visible fuze cavity, distinguishes it from other designs. Early variants may show varying paint finish, while later production runs show more uniform, smoother surface finish. Compare against reference materials (photographs, museum displays) to confirm. Size (roughly 10.5 inches long, 2.5 inches diameter) and weight (~1.5 lbs) further narrow identification.
Q: Are BLU-24/B submunitions found in specific regions, or are they everywhere?
A: BLU-24/B submunitions are concentrated heavily in Southeast Asia (Vietnam, Laos, Cambodia), where hundreds of millions were dispersed between 1965 and 1973. Significant quantities were also deployed to South Vietnam allies and used in Middle East operations. Outside these regions, BLU-24 contamination is minimal. If you encounter Orange cluster submunitions in unexpected locations (Europe, Sub-Saharan Africa), verify nomenclature carefully—color alone is insufficient for positive identification.
Q: If I find an unarmed BLU-24/B (failed to detonate) in the field, how dangerous is it?
A: An unexploded BLU-24/B is considered armed and extremely hazardous. The submunition remains in armed condition indefinitely unless deliberately rendered safe. Impact sensitivity of 2–5 G means that vibration from vehicle movement, excavation, or handling could detonate it. Do not touch, move, or disturb the munition. Cordon off a safety perimeter (minimum 25 meters), mark location, and contact qualified EOD personnel. Age of the munition (Vietnam-era submunitions are now 50+ years old) increases unpredictability.
Q: What is the blast radius I should brief my personnel to expect?
A: Primary blast injury potential extends to approximately 20 meters. Lethal fragmentation effects extend 15–25 meters, with steel ball bearings capable of penetrating light body armor or causing severe trauma at any distance within that radius. Safe distance for unprotected personnel: minimum 30 meters. For planning purposes, assume 50-meter stand-off distance provides reasonable margin for blast and secondary fragmentation effects. In clusters where multiple submunitions are present, account for sympathetic detonation doubling the effective hazard radius.
Q: Can a BLU-24/B be safely detonated in place as part of remediation efforts?
A: Controlled in-place detonation is a legitimate remediation technique when environmental and safety conditions permit. Detonation must be executed by qualified EOD personnel with proper explosive ordnance disposal training and authority. Site must be secured, personnel evacuated beyond safe stand-off distance (minimum 100–150 meters depending on number of munitions), and blast debris containment considered. Detonation is preferred over attempted removal in areas with high contamination density. Consult with national or international ordnance disposal authorities for regional guidance.
Q: How does aging affect BLU-24/B reliability and hazard?
A: Aging degrades both reliability and predictability. TNT-based explosives remain chemically stable for decades but become increasingly brittle. Fuzing mechanisms corrode and may lose sensitivity calibration. Field-aged submunitions (Vietnam era, now 50+ years old) show highly inconsistent detonation behavior—some detonate on minimal impact, others fail to detonate at all. Corrosion of steel casing can rupture unexpectedly under stress, exposing degraded explosive fill. Age increases unpredictability rather than reducing hazard. Treat aged munitions as marginally hazardous rather than “safe” through decay.
Q: What is the difference between BLU-24/B early and late models in terms of hazard assessment?
A: Early BLU-24/B submunitions (1960s–early 1970s) have less refined fuzing and more variable fragmentation distribution. Late models (1970s–1980s) have improved fuzing consistency and optimized fragmentation density, making them more reliably effective. From a hazard perspective, both pose equivalent threat—direct impact detonation at 2–5 G sensitivity with lethal fragmentation extending 15+ meters. The main difference is reliability of fuzing, which paradoxically makes later models somewhat more predictable as UXO (less likely to fail to detonate). No meaningful difference in stand-off distance or protection requirements.
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.