UNCLASSIFLED

1970 ;1AD ,

Ref

ARMED SERVICES TECHNICAL INFORMATION AGENCYARLINGTON HALL STATIONARLINGTON 12, VIRGINIA

UNCLASSIFIED

NOTICE: When government or other drawings, speci-fications or other data are used for any purposeother than in connection with a definitely relatedgovernment procurement operation, the U. S.Government thereby incurs no responsibility, nor anyobligation whatsoever; and the fact that the Govern-ment may have formulated, furnished, or in any waysupplied the said drawings, specifications, or otherdata is not to be regarded by implication or other-wise as in any manner licensing the holder or anyother person or corporation, or conveying any rightsor permission to manufacture, use or sell anypatented invention that may in any way be relatedthereto.

s 1998f0 NOLTR 61-171o 279 523

I ENERGY REQUIREMENTS FOR THEINITIATION OF WIRE AND CARBON BRIDGEPRIMERS CONNECTED ELECTRICALLY INPARALLEL OR SERIES

22 NOVEMBER 1961

UNITED STATES NAVAL ORDNANCE LABORATORY, WHITE OAK, MARYLAND

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j ] k~pprovei by o.u..eopz required for releea"

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i!QkTI

NOLTR 61-171

ENERGY REQUIREMENTS FOR THE INITIATION OF WIRE ANDCARBON BRIDGE PRIMERS CONNECTED ELECTRICALLY IN PARALLEL OR SERIES

Prepared by:

E. Eugene Kiimer

Approved by:Chief7l'xplosidn Dynam s Division

ABSTRACT: In order to gain information about explosive trainreliability, carbon bridge and wire bridge primer ignitionassemblies were tested in parallel and in series by capacitordischarge. In addition, wire bridge assemblies were tested inparallel and in series by constant current. About twice as muchenergy was required to fire two carbon bridge assemblies as tofire a single one. It required 2.6 times as much energy bycapacitor discharge to fire two wire bridge assemblies as tofire one. Under constant current conditions, two wire bridgeignition assemblies in series required the same current as asingle unit but for two in parallel more than twice thecurrent was needed than for a single unit,

PUBLISHED FEBRUARY 1962

Explosions Research DepartmentU. S. NAVAL ORDNANCE LABORATORY

WHITE OAK, MARYLAND

4i

NOLTR 61-171 22 November 1961

This report discloses information concerning the firing require-ments of two ignition assemblies from production lots of PrimersMk 114 and Mk 121 when connected in parallel and in series.This work was carried out in the Explosion Dynamics Division ofthe Explosions Research Department, Naval Ordnance Laboratory,White Oak Maryland, in connection with Wep Task RUME-3-E-O16/212 I/FO08-10-004, Underwater Initiating Units.

The results of this investigation are intended for the informa-tion and use of the Naval Ordnance Laboratory and should be ofinterest to others working with electro-explosive devices.

W. D. COLEMANCaptain, USNCommander

C. ARONSONBy direction

,ii

NOLTR 61-171

CONTENTSPage

Introduction .............. 1The Primer Mk l14 Mod 0 Ignition Assembly Tests ..... 2

Capacitor Discharge Firing . . . . . . . ................ 2Single Item Firing... . .... ....... . 2Firing of Two Items in Series. . . . . . . . . . . . . 3Firing of Two Items in Parallel. . . . . . . . . . . . 3

Constant Current Firing ......... . . . . . . .- 3The Primer Mk 114 Mod 0 Ignition Assembly Tests. . .. . . 4Discussion . . . . . . . . . . . . . . . . . . . . . . . 5Conclusions. . . . . . .. . ... . . 6

ILLUSTRATIONS

Figure Title Page

1 The Mk 114 Mod 0 Primer Ignition Assembly . . . . 10

2 The Mk 121 Mod 0 Primer Ignition Assembly . . . . 11

3 The Multiple Firing Circuit Arrangement . . . . . 12

4 The Energies at Which 50% of the Primer Mk 114Mod 0 Ignition Assemblies Fire From CapacitorDischarge Initiation. . . . . . . . . . . . .13

5 A Typical Capacitor Discharge Curve for theMk 114 Mod 0 Primer (Primer Fire). . . . . . . . 14

6 Firing of the Primer Mk 114 Mod 0 Ignition

Assembly as a Function of the Current . . . . . . 15

7 The Crystal Pick Up Assembly. . . . . . . . . . . 16

8 The Ignition Lag Time of the Mk 114 Mod 0 PrimerIgnition Assembly as a Function of the Current . 17

9 The Mean Energy Requirement as a Function of thePotential (Mk 121 Mod 0 Primer Ignition Assembly)18

10 The Mean Energy Requirement as a Function of thePotential (Mk 121 Mod 0 Primer Ignition Assembly)Parallel Firing . . . . . . . . . . . . . . . . 19

11 The Mean Energy Requirement as a Function of thePotential (Mk 121 Mod 0 Primer Ignition Assembly)Series Firing . . . . . . . ......... . 20

A iii

NOLTR 61-171

ILLUSTRATIONS(con't)

Table Title Page

1 The Energy Requirements for Firing thePrimer Mk 114 Mod 0 Ignition Assembly. . . . . 7

2 Constant Current Firing of Primer Mk 114Ignition Assembly. . . . . . . . . . . . . . . 8

3 The Energy Requirements for Firing thePrimer Mk 121 Mod 0 Ignition Assembly ..... 9

REFERENCES

(1) Electric Initiator Handbook, 3rd Edition, 29 April 1960prepared by the Franklin Institute for Picatinny Arsenal,Confidential

(2) "Statistical Analysis for a New Procedure in SensitivityExperiments", AMP Report 101.1R SRG-P No 40, July 1944,Unclassified

(3) NavWeps Report 7347, "Characterization of Squib, Mk 1Mod 0, Determination of the Statistical Model", L. D.Hampton, and J. N. Ayres, 30 Jan 1961, Unclassified

(4) NOLR 1111, Ordnance Explosive Train Designers' Handbook,April 1952, Confidential

iv

NOLTR 61-171

ENERGY REQUIREMENTS FOR THE INITIATION OF WIRE ANDCARBON BRIDGE PRIMERS CONNECTED ELECTRICALLY IN PARALLEL OR SERIES

IN TRODUCTI 0-N

1. Most modern weapons contain electro-explosive devices whosefunctioning reliabilities affect the overall weapon reliability.Most production lot primers have about 99.8 percent functioningreliability at a 95-percent confidence level. The 0.2 percentof unreliability is considered to be too great for many of ournew weapon systems. To increase the reliability of a weapon anexplosive train containing two primers (or detonators) is usuallyincorporated into the design with planned redundancy.

2. Considerable data are available on the energy required toinitiate a single given electric initiator (1). When designinga dual initiator train, the assumption usually has been made thatthe energy requirement will be twice that which is necessary fora single unit. This assumption has been made with considerablereservation because of a lack of substantiating data. However,it appeared to be not too unreasonable a first approximation.

3. The purpose of this project was to study several typicalprimers to determine the energy required to initiate them whenconnected electrically singly, and as two identical units inparallel or in series. The methods of delivering the energywere by capacitor discharge and by constant current applied fora fixed time. Two electric primers were chosen for study; thePrimer Mk 114 Mod 0, a wire bridge item; and the Primer Mk 121Mod 0, a carbon bridge item. Since only the firing character-istic was of interest, only the response of the ignition assem-blies (Figures 1 and 2) of each primer/was considered in thetests.

4. The Primer Mk 114 Mod 0 Ignition Assembly consists of twoinsulated copper wires twisted together in a molded plastic plug.The wires extended up out of the plug approximately 0.07 inch.These leads are bridged with an 0.005-inch diameter nichrome wirewith an effective length of about 0.025 inch. The bridge has aresistance range of 3 to 7 ohms. This bridge is loaded with amixture of (75/25) DDNP/potassium chlorate as a buttered charge.

1

NOLTR 61-171

THE PRIMER MK 114 MOD 0 IGNITION ASSEMBLY TESTS

Capacitor Discharge Firing

5. The capacitor discharge tests on the ignition assemblies weremade using the equipment arrangement shown in Figure 3. Thestatistical response of the ignition assembly to the energystored in the capacitor was determined by the Bruceton Sensi-tivity Test (2) assuming a log normal distribution for theresponse of the ignition element to the initiating energy. Thecapacitance was varied and the potential held constant for eachtest.

6. Each Bruceton test was run using a sample size of 50 whichgives a reasonably good estimate of the mean firing energy.Values of the standard deviation were also obtained from theBruceton test runs and used to calculate the energy associatedwith 0.001 and 0.999 probability of functioning. While the meanfiring energy is established with good precision the estimate ofthe standard deviation with a sample size of 50 is probably nottoo accurate. Consequently, the mean firing energy and not theextreme points of the distribution is best for making comparisonsin analyzing the test results. (In addition, it has been shownfor at least one conventional wire bridge electro-explosive devicethat the log normal distribution does not accurately predict thetails of the distribution(3) although the mean of the distributionis precisely known.)

7. In the dual initiator arrangement two firing criteria wereused:

Both ignition assemblies had to function to be considereda fire.

Only one ignition assembly had to function to be considereda fire.

The input current to and the voltage across each assembly duringfiring were monitored by a dual beam oscilloscope. The test pro-gram was arranged to consider each criterion in separate tests.

8. Single Item Firing. A random sample of ignition assemblieswas selected from the production lot for the testing. The resultsof tests to determine the response of a single item to differentinitiati