CONTROL OF THE WORKING TIME OF A LASER IGNITED DETONATOR. H.Moulard, A.Ritter, J.Mory (ISL) Work done under DGA contract

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1 CONTROL OF THE WORKING TIME OF A LASER IGNITED DETONATOR. H.Moulard, A.Ritter, J.Mory (ISL) Work done under DGA contract Opto-pyrotechnics Workshop IAS - TOULOUSE 17 November

2 Optopyro Initiation at ISL Design and development of opto-pyrotechnic fuzing systems for SPACE (CNES spec) and DEFENSE use. ISL Main Task, Design of Opto-pyro. Igniter and Opto-pyro. Detonator. Current ISL opto-pyro R&D projects: CNES / ESA: replacement of hot wire devices on ARIANE (2011). TDA / THALES: opto-pyro detonator for a laser firing system for Active Defense System of armoured vehicles. 2

3 Active Defense System for Land vehicles SHarK :Ultra-light hard kill protection : short distance interception needs ultra fast arming and firing unit 3

4 LASER DETONATORS: Working Time? Low jitter on Working Time dispersion Fast Laser Detonators: Plasma Shock initiation, but need expansive complex laser sources Laser Ignited Detonator: Thermal laser energy supply Developed for Spacecraft multi-initiation purpose? Use for Defense multi-initiation purpose with limited jitter and cheap laser sources? 4

5 ADS Technical requirements for a low jitter Laser Ignited Detonator All secondary High Explosives. Pass Safety standard Tests (COOK-OFF, ESD). Nd-YAG (free running) laser pulse: < 200 mj and < 150 µs injected in 200 µm Fibre. Detonator Function Time < 150 µs with Jitter ±5 µs. Temperature range: -40 C to +70 C 5

6 ISL Laser detonator for Space use Laser Ignited Detonator : Specially designed for 1 Watt Laser diode (CNES spec). A thermal laser interaction starts a combustion. Advantages: from optical fiber transmission. Insensitivity to ESD, EM and RF disturbances. No primary H.E.: In Line use without mechanical barrier. Easy modular architecture: large distance de-coupling. Cost and weight savings. 6

7 two-stage Opto-pyrotechnic Detonator based on Shock Detonation Transition ISL patent Ignition: ZPP* Strengthened Shock Priming power *For Space Use: ignition reliability needs a pyrotechnics layer 7

8 Strategy to control Laser ignited detonator function time Ignition phase is the slow step, source of time dispersion. Physical parameters to shorten it: Optical power density: the more determining. H.E. formulation optimization: increase thermal laser ignition sensitivity without decreasing material pyrotechnical safety. Choice of H.E, loading density, particle structure. Choice of optical dopant (nature, %) Architecture (confinement) 8

9 Detonator «Jitter» measurement after thermal environment The low jitter laser ignited detonator design is identical to the spatial detonator, except the following differences: Laser source: Nd-YAG solid laser with a 140 mj laser pulse injected in a 200 µ optical fiber. All secondary H.E laser detonator: No pyrotechnics for the first explosive train ISL Thermal Cycling Test Θ Plateau Θ h C Shot detonator Θ d C Room Θ C 5 hours time 9

10 DOP2 Results: Jitter at Room Temperature shot N Thermal conditions Laser pulse total energy (mj) Function time (µs) Ignition phase Power density (MW/cm 2 ) 1 16 C ,6 3, C , C ,6 3, C ,0 3, C ,6 3, C ,4 3, C ,8 3, C ,4 3,9 1st stage loading: HMX/CB DOP2 grade 99/1 10

11 DOP2 Jitter after Cold thermal exposure shot N Thermal conditions 5h at -50 C shot at -44 C 5h at -50 C shot at -44 C 5h at -50 C shot at -40 C 5h at -40 C shot at +20 C 5h at -40 C shot at +20 C Laser pulse total energy (mj) Function time (µs) Ignition phase Power density (MW/cm 2 ) ,

12 Jitter after hot thermal exposure shot N Thermal conditions 5h at +70 C shot at +20 C 5h at +70 C shot at +20 C 5h at +80 C shot at +72 C 5h at +80 C shot at +65 C 5h at +80 C shot at +70 C Laser pulse total energy (mj) Function time (µs) Ignition phase Power density (MW/cm 2 ) ,1 3, ,0 3, ,4 3, ,2 3,2 117,2 42,2 3,3 12

13 Nd-YAG Laser pulse requirement To assure function time reproducibility, key parameter is the laser energy delivered during ignition phase. Reproducibility observed for optical power equal to 1kW (or 3.2 MW/cm 2 ). This high power level during ignition phase is needed to assure reproducibility. 13

14 Effect of H.E. formulation on Laser ignition sensitivity of H.E. Thermal environment makes harder jitter control: Thermal cycling at high temperature is a very severe test for jitter control. To control it, three key parameters: Optical power density of laser source. Optical dopant efficiency. Choice of H.E particle distribution and structure 14

15 Effect of optical dopant (CB) on jitter after thermal cycling HMX/CB DOP2 grade 99/1 shot N Thermal conditions 5h at +70 C shot at +20 C 5h at +70 C shot at +20 C 5h at +120 C shot at +71 C 5h at +100 C shot at +20 C 5h at +100 C shot at +25 C Function time (µs) Ignition phase Power density (MW/cm 2 )

16 Effect of optical dopant (Alex ) on jitter after thermal cycling shot N Thermal conditions Laser pulse total energy (mj) HMX/Alex DOP2 grade 99/1 Function time (µs) Ignition phase Power density (MW/cm 2 ) 1 25 C C C h at +100 C shot at +25 C 5h at +100 C shot at +25 C 5h at +100 C shot at +25 C

17 DoD Homologation: sensitivity of laser ignition explosive STANAG 4170 (AOP7) & MIL-STD 1751 A REFERENCE for Booster Explosive Qualification Explosive formulation RDX type II class 5 HMX/CB (99/1) DOP2 grade HMX/Alex (99/1) DOP2 grade HMX/Alex/Viton DOP2 grade (99/1/1) HMX/CB (99/1) DOP3 grade BAM Impact test No fire Limit BAM friction test No fire Limit 3,5 J 108 N 2,5 J 108 N 2,5 J 96 N 3,5 J 112 N 12,5 J 112 N 17

18 Effect of explosive particles on jitter after thermal environment HMX/CB DOP3 grade 99/1 Nd-YAG source 3,5 MW/cm 2 Thermal conditions 20 C 5h at 70 C shot at 20 C 5h at 100 C shot at 20 C -40 C 5h at -40 C shot at 20 C function time 45 ± 5 µs 45 ± 5 µs 45 ± 5 µs 45 ± 5 µs 45 ± 5 µs 18

19 C.o.t.S. Laser Diode and jitter First results, work in progress. The most challenging: the hot thermal cycling test HMX/CB DOP3 grade 99/1 Laser diode 105 µm 0,16 MW/cm 2 Thermal conditions 20 C 5h at 70 C shot at 20 C 5h at 110 C shot at 20 C Function time 85 ± 5 µs 90 ± 10 µs 250 ± 100 µs A lot of potential for next future (laser technology, explosive formulation ) 19

20 Summary A laser ignited detonator, initiated by a free running Nd-YAG source with an optical power density of 3.5 MW/cm 2 has a working time of 45 µs ± 5 µs, on operational temperature range (-40 C, +100 C) To control the working time dispersion, key parameters : Optical power density HE formulation (explosive particles, optical dopant) Further works are in progress to control function time dispersion with compact laser diodes. 20