active mitigation: rocket initiator thermally activated (rita) … · 2017-05-18 · 2012 ndia fuze...

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


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


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


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)


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


6

EX 22 Mod 5 – Fwd Vent

Front Vented Headcap

Nozzle

Nozzle

Salt Sleeve

NiTiNOL

Hoop

Retainer

Plug

Front Vented Insert


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)


8

Thermally Venting Bulkhead

Motor Tube Bulkhead-Tube Interface (BTI)

Igniter

Bulkhead

NiTiNOL Hoop

Initiator

Bridle Attachment

Retainer

*RITA Not Pictured


9

Early Compact RITA Design

• Revised Low-Profile RITA Design


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


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


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


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


14

2nd Generation RITA Design


15

Components

STRIKER BARS

(SPRING)

FIRING PIN

(TOP)

SLIDER

INITIATOR

BASE

SHEAR PIN

PERCUSSION

PRIMER &

FLYER BALL

NiTiNOL BARS


16

Exploded View

SLIDER

INITIATOR


17

Anti-Blowback Initiator

SEALING DISK INITIATOR BODY BKNO3 FELT PAD BRASS BALL FELT PAD BKNO3 C-CLIP SEALING DISK


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


19

Safe and Fire Cutaways

SAFE POSITION ARM/FIRE POSITION


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


21

Successful Results of RITA Assembly

SCO Tests


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)


23


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


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


26

Contact Information

Mr. John Swain Indian Head Division, NSWC 4081 N. Jackson Road, Suite 2 Indian Head, MD 20640 (301) 744-1162 [email protected]

Mr. Matthew Sanford Indian Head Division, NSWC

4103 Fowler Road, Suite 107


(301) 744-1929

[email protected]

active mitigation: rocket initiator thermally activated (rita) … · 2017-05-18 · 2012 ndia fuze...

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