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2012 NDIA Fuze Conference
14 & 16 May 2012
NSWC – Indian Head, MD
Active Mitigation: Rocket Initiator Thermally
Activated (RITA) Insensitive Munitions (IM) Device
for the MK22 Mod 4 Rocket Motor
Distribution Statement A: Unlimited - Approved For Public Release
John Swain Code E15JS, Bldg 841
IHDIV, NSWC
Indian Head, MD 20640
Matthew Sanford Code E34MS, Bldg 302
IHDIV, NSWC
Indian Head, MD 20640
Distribution Statement A: Approved For Public Release
2
Rocket Motor Improvements
• Proposed Solutions:
1. Fully vent both ends using a thermally activated shape memory alloy (NiTiNOL) release mechanism
• Modify headcap
• Modify igniter bulkhead
• New end enclosure
2. Ignite surface of propellant prior to auto-ignition using an Active Mitigation Device (AMD)
• Rocket Initiator Thermally Actuated (RITA)
Modified igniter bulkhead and new
end enclosure
Modified Headcap
RITA
EX 22 Mod 5
Distribution Statement A: Approved For Public Release
3
RM IM Improvement Approach
• Design approach temperature timeline to allow safe, controlled venting (SCO Profile):
*All Proposed IM Mitigation Events Will
Occur Prior To Grain Auto-Ignition
0°F
RITA Functions &
Ignites The Motor
~210°F Vents
Are Released
IM Improved MK22 RM*
Temp.
~255°F Grain Auto-Ignites Current MK22 RM
Temp. 0°F
Distribution Statement A: Approved For Public Release
4
Concept Testing
• Slab Motor Tests
– Determined Propellant Could be
Safely Ignited At Elevated
Temperatures
• High Temperature Vented Test
– Proved Active Mitigation Device
Required
• High Temperature Ignition Test
– High Temperature Ignition Viable
• Limited RITA Functionality Tests
– Showed that the NiTiNOL bar
could meet our requirements and
that the primer would transfer to
the Initiator
High Temperature Ignition Test
(Double Venting)
Distribution Statement A: Approved For Public Release
5
MK22 Mod 4 Rocket Motor Current Production Configuration
Electrical Lead
Towing Bridle
Propellant Grain
Salt Sleeve
Nozzle
Locking Pin
Plug
Nozzle
Baffle
End Closure
Igniter
Spring
N-5 Double Base Propellant Autoignition Temperature ~255°F
Distribution Statement A: Approved For Public Release
6
EX 22 Mod 5 – Fwd Vent
Front Vented Headcap
Nozzle
Nozzle
Salt Sleeve
NiTiNOL
Hoop
Retainer
Plug
Front Vented Insert
Distribution Statement A: Approved For Public Release
7
EX 22 Mod 5 – Aft Vent
Propellant Grain NiTiNOL Hoop
Modified End Closure
Baffle
Spring Igniter
Retainer
SDI Initiator*
Igniter Insert
Bulkhead Tube Interface (BTI)
*Maintaining Current In-Line Initiator (Prior to MIL-STD-1901)
Distribution Statement A: Approved For Public Release
8
Thermally Venting Bulkhead
Motor Tube Bulkhead-Tube Interface (BTI)
Igniter
Bulkhead
NiTiNOL Hoop
Initiator
Bridle Attachment
Retainer
*RITA Not Pictured
Distribution Statement A: Approved For Public Release
9
Early Compact RITA Design
• Revised Low-Profile RITA Design
Distribution Statement A: Approved For Public Release
10
Compact RITA Design
Actuation Process:
1. RITA In Safe Position
• Primer Out of Line With Initiator Charge
• NiTiNOL Bar Is A Structural Member (Device Lock)
• No Stored Energy
RITA Initiator Assembly
Distribution Statement A: Approved For Public Release
11
Early Compact RITA Design
Actuation Process Cont’d:
2. RM & (RITA) Exposed To Cook-off Environment
(SCO or FCO)
• NiTiNOL Bar Begins To Contract
• Slider Begins To Pivot
• Striker Begins Moving Along Slider Ramp
Wedge
Striker
Primer
Wedge
Striker
Primer
Slider
Distribution Statement A: Approved For Public Release
12
Compact RITA Design Actuation Process Cont’d:
3. RITA Fully Actuates (Armed Position)
• NiTiNOL Bar Completes Contraction
• Slider Completes Pivot Motion
• Striker Reaches the Apex of Slider Ramp And Releases
• Firing Pin Impacts Primer
• Begins Ignition of Initiator Charge / Igniter / RM
Distribution Statement A: Approved For Public Release
13
2nd Generation RITA Design Improvements
1. Eliminate pressure loss in BKNO3 to Igniter transfer
2. Increase margins of safety on the striker/ firing pin and
NiTiNOL contraction percentage
3. Incorporate a 2nd Safety Feature into the RITA system (FISTRP
Requirement)
4. Retest BKNO3/Igniter transfer
5. Follow up with DVT and Qualification Testing of the RM
Distribution Statement A: Approved For Public Release
14
2nd Generation RITA Design
Distribution Statement A: Approved For Public Release
15
Components
STRIKER BARS
(SPRING)
FIRING PIN
(TOP)
SLIDER
INITIATOR
BASE
SHEAR PIN
PERCUSSION
PRIMER &
FLYER BALL
NiTiNOL BARS
Distribution Statement A: Approved For Public Release
16
Exploded View
SLIDER
INITIATOR
Distribution Statement A: Approved For Public Release
17
Anti-Blowback Initiator
SEALING DISK INITIATOR BODY BKNO3 FELT PAD BRASS BALL FELT PAD BKNO3 C-CLIP SEALING DISK
Distribution Statement A: Approved For Public Release
18
Safe and Fire (4% NiTiNOL Contraction)
3. SLIDER
ROTATES
2. NiTiNOL
CONTRACTS
4. STRIKER RAISED
AND SNAPS DOWN
1. SHEAR PIN
SOFTENS
SAFE FIRE
Distribution Statement A: Approved For Public Release
19
Safe and Fire Cutaways
SAFE POSITION ARM/FIRE POSITION
Distribution Statement A: Approved For Public Release
20
Retracted Position (Misfire)
UNDERCUT NOTCH
BELOW SLIDER RAMP
FIRING PIN MOVES
OFF OF PRIMER
NiTiNOL BARS RE-EXPAND
AFTER RE-COOLING
Successful Component Level Testing:
• Pull-Testing of Springs to Confirm Proper Firing Energy
• Pull-Testing of Slider Assembly to Confirm Required Pull
Force and Pull Energy Requirements
• Pull Testing of Slider and Shear Pin Resistance
• Striker Bar, Firing Pin, and Primer Initiation Tests
• Various Tensile Tests on NiTiNOL Bars to Confirm Available
Pull Force and Pull Energy
• Transfer Testing Between Primer and Initiator
• Out of Line Safety Tests, Primer to Initiator
• Function Testing of Initiator Check Valve
• Function Testing of Two Slider Materials
– Electroless Nickel Plated Teflon Impregnated SS Slider
– Teflon Impregnated Hard Annodize on Aluminum Slider
Distribution Statement A: Approved For Public Release
21
Successful Results of RITA Assembly
SCO Tests
Distribution Statement A: Approved For Public Release
22
Time of Day
Tem
pera
ture
(d
eg
F)
RITA Functionality TestSlow Cookoff #2
27 Jan 2012
12:00:00 AM 4:00:00 AM 8:00:00 AM 12:00:00 PM 4:00:00 PM50
100
150
200
250
300
350
230 deg F
Cold JunctionOvenIgniter Base
Time (hrs)
Tem
pera
ture
(oF
)
RITA Slow-heat Initiation Test6 Deg F per Hour
15 Dec 2011
0 2 4 6 8 10 1250
100
150
200
250
300
CJC
OvenRita
Initiation at 235 Deg F
Oven Door Opened Momentarily
°Cold JunctionOven °FRITA
A thermocouple “witness” indicator was placed
across the output of the check valve initiator.
High-Speed Video of RITA Functioning
(Manual Pull)
Distribution Statement A: Approved For Public Release
23
Distribution Statement A: Approved For Public Release
24
Conclusions
• The NiTiNOL based initiation device described here
appears to be a viable active mitigation option
• The mechanism described is simple and robust, and
appears to be safe and reliable, despite single
environment (heat only) activation
• A full set of safety testing (drop, vibration, temperature
cycling, etc.) still needs to be done, and likely some
minor design refinements based on the test results
• Evolving active mitigation requirements have driven
design modifications and features throughout the
development of this device
Distribution Statement A: Approved For Public Release
25
Acknowledgements
• Intrinsic Devices Inc. for NiTiNOL Fabrication and Developing Requirements for the material
• ATR for their Support in Configuration Review
• Tidewater Machine for Drawing and Design Review and Hardware Fabrication
• IHDIV, NSWC
– Nancy Johnson – Effort Coordination Support/Project Management
– Frank Valenta & Pete Margiotta – Primer & Design Support
– Murthy Bettadapur – Material Selection & Testing Support
– Ricky Johnson – Hardware Receipt Inspection
– Danny Bouch – RM Assembly
– Bob Johnson – RITA/Initiator Fabrication
– Mike McDonnell & John Lawrence – Inert Component Testing
– Paul Wallman & Mark Principe – Live Energetic Component Testing
Distribution Statement A: Approved For Public Release
26
Contact Information
Mr. John Swain Indian Head Division, NSWC 4081 N. Jackson Road, Suite 2 Indian Head, MD 20640 (301) 744-1162 john.e.swain@navy.mil
Mr. Matthew Sanford Indian Head Division, NSWC
4103 Fowler Road, Suite 107
Indian Head, MD 20640
(301) 744-1929
matthew.j.sanford@navy.mil
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