EX 437
Multi-Option Fuze
for Navy
Chad Finch
Naval Surface Warfare Center Dahlgren
47th Annual Fuze Conference
“Enhancing Weapon Performance”
April 8-10, 2003
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5” Conventional Ammo
MOFN
MOFN
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M762A1 to MK 432 Conversion
M762A1
MK 432 MOD 0
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M782 Multi-Option Fuze for Artillery
Point Detonating (PD)
Electronic Time (ET)
Surface Proximity (HOB)
Point Detonating Delay
HSMST
Operational Modes
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What is “Navalization”?
A “Navalized” MOFA must be:
• Compatible with Navy guns
– Changes to fuze’s inductive coil / circuit
– Changes to fuze’s inductive interface
(software)
–
Increased precision in electronic time mode
• High Speed Maneuvering Surface Target
(HSMST)
• Safe in Navy guns
– Changes to S&A to increase arming distance
– Changes in software to delay charging of
firing circuit
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Compatible with Navy Guns
• MOFA will not set with MK 34 Fuze Setter
• MOFA inductive coil similar to M762A1
• For M762A1 to MK 432 conversion
– Replaced M762A1 coil w/ MK 419 MFF coil
M762A1 Coil
MK 432 Coil
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Compatible with Navy Guns
• For M782 MOFA to EX 437 conversion
– MK 419 coil will not fit into MOFA
– Proximity sensor limits available space
• Promising results from initial testing
– 575 turns w/ 38 awg wire (fits on MOFA bobbin)
– Small ferrite core (fits under MOFA bobbin)
– Series resonant circuit
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Compatible with Navy Guns
MK 34
Setter
Coil
Fuze
Coil
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• MOFA uses a 23-bit binary message
– ET is settable in 0.1 second increments
• Navy requires a 26-bit binary message
–
“We’re kicking it up a notch!”
to allow setting in 0.01 second increments
– A must have for engaging HSMST
Compatible with Navy Guns
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Safe in Navy Guns
• MOFA uses an M739-type S&A
– Minimum arming distance of 205 ft in the 5” gun
• Conducted a study to assess hazard for
arming distances between 200 and 4800 ft
– Assuming a fuze function at arming
– All distances posed a 1-D risk (MIL-STD-882C)
• Selected 400 feet as the minimum arming
distance
– Gets fuze beyond stern of ship
– Requirement for close in engagement
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Increase
Moment of
Inertia
Change R