Sunday, 20 February 2011

Hazards of Electromagnetic Radiation to Ordnance (HERO)

The  high  intensity  radio  frequency  (RFR)  fieldsproduced   by   modern   radio   and   radar   transmittingequipment   can   cause   sensitive   electroexplosivedevices   (EEDs)   contained   in   ordnance   systems   toactuate prematurely. The Hazards of ElectromagneticRadiation   to   Ordnance   (HERO)   problem   was   firstrecognized  in  1958.  The  prime  factors  causing  theproblem have been increasing ever since. The use ofEEDs  in  ordnance  systems  has  become  essential.  Atthe same time, the power output and frequency rangesof  radio  and  radar  transmitting  equipment  have  alsoincreased.RFR energy may enter an ordnance item through ahole or crack in its skin or through firing leads, wires,and   so   on.   In   general,   ordnance   systems   that   aresusceptible to RFR energy are most susceptible duringassembly,   disassembly,   loading,   unloading,   andhandling in RFR electromagnetic fields.The most likely results of premature actuation arepropellant   ignition   or   reduction   of   reliability   bydudding. Where out-of-line Safety and Arming (S + A)devices   are   used;   the   actuation   of   EEDs   may   beundetectable  unless  the  item  is  disassembled.  If  theitem does not contain an S + A device, or if RFR energybypasses the S + A device, the warhead may detonate.Ordnance   items   susceptible   to   RFR   can   beassigned   one   of   three   HERO   classifications,   basedupon   the   probability   that   they   will   be   adversely a f f e c t e d     b y     t h e     R F R     e n v i r o n m e n t .     T h o s eclassifications are:1.   HERO   Safe.   An   ordnance   item   sufficientlyshielded   or   protected   to   make   it   immune   toadverse   effects   from   RFR   when   used   in   itsexpected shipboard RFR environments.2.   HERO susceptible. Ordnance containing EEDsproven by tests to be adversely affected by RFRenergy to the point that safety or reliability maybe in jeopardy when the ordnance is used in RFRenvironments.3.   HERO   unsafe.   Any   electrically   initiatedordnance item that becomes unsafe when:a.   Its internal wiring is physically exposed.b.   Tests  being  conducted  on  the  item  requireadditional electrical connections to be made.c.   Electroexplosive   devices   (EEDs)   havingexposed wire leads are present, handled, orloaded.d.   T h e i t e m i s b e i n g a s s e m b l e d o rdisassembled.e.   The item is in a disassembled condition.f.   The item contains one or more EEDs and hasnot   been   classified   as   HERO   safe   orsusceptible   by   either   a   test   or   designanalysis.To ensure the HERO safety and HERO reliabilityof   ordnance   systems,   the   Naval   Sea   SystemsCommand  sponsors  an  extensive  testing  program  todetermine  their  susceptibility  to  RFR  energy.  HEROrequirements   and   precautions   are   provided   inNAVSEA   OP   3565/NAVAIR   16-1-529/NAVELEX0967-LP-624-6010/Volume   II,    ElectromagneticRadiation  Hazards  (U)  (Hazards  to  Ordnance)  (U).You will find your ship’s specific requirements in itsHERO Emission Control (EMCON) bill.The  commanding  officer  of  each  ship  or  shorestation   is   responsible   for   implementing   HEROrequirements.   He   or   she   must   also   establish   aprocedure  to  control  radiation  from  radio  and  radarantennas   among   personnel   handling   ordnance   andpersonnel controlling radio and radar transmitters. Thecommanding   officer   does   this   through   a   commandinstruction  based  on  the  ship’s  mission  and  specialfeatures. This instruction is usually part of the Ship’sOrganization Manual and is the basis for departmentand division instructions

No comments:

Post a Comment