A LEARJET 45 CAPT'S WINDOW FAILED AT FL430. THE CREW DSNDED AND DIVERTED TO AN UNPLANNED DEST.

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DURING CRUISE FLT AT FL430; IN SMOOTH AIR; WE EXPERIENCED A FAILURE OF THE PLT SIDE WINDSHIELD. THERE WAS A SUDDEN AND VERY LOUD BANG AND THE ENTIRE WINDSHIELD SHATTERED. I; THE CAPT; WAS THE PNF AND OCCUPIED THE R SEAT. THE FO; PF AND OCCUPYING THE L SEAT; AND I IMMEDIATELY DONNED OUR MASK. WE BEGAN AN EMER DSCNT. THERE WAS A VERY SLIGHT DELAY IN COMMUNICATING WITH ATC DUE TO NOT SELECTING THE CORRECT SWITCH FOR THE MASK MIKE. I NOTIFIED ATC IMMEDIATELY AND DECLARED THE EMER. I INFORMED THEM THAT WE MAY BE LOOKING PRESSURIZATION AND NEEDED LOWER IMMEDIATELY. BY THIS TIME WE HAD ALREADY STARTED A DSCNT AND COMPLETED MEMORY CHKLIST ITEMS. ATC THEN CLRED US TO FL240 AND ASKED WHAT ALT WERE WE REQUESTING DSCNT TO. I INFORMED ATC THAT A MINIMUM 10000 FT WOULD BE REQUIRED. I INFORMED ATC THAT ZZZ1 WOULD NOT BE SUITABLE. ATC ADVISED THAT ZZZ WAS 50 NM. ONCE BELOW 10000 FT WE HAD COMPLETED ALL CHKLIST ITEMS AND I BRIEFED THE PAX AS TO SIT AND ASCERTAINED THAT THEY WERE ALRIGHT. ATC CLRED US TO 6000 FT AND DIRECT TO ZZZ VECTORS FOR THE ILS RWY 22. THE FO AND I DISCUSSED THAT SINCE THE PF DID NOT HAVE ADEQUATE VISIBILITY AND DUE TO THE POSSIBILITY OF TOTAL WINDSHIELD FAILURE RESULTING IN IMPLOSION IT WAS DECIDED THAT I WOULD MAKE THE LNDG FROM THE R SEAT. LNDG WAS UNEVENTFUL. IN RETROSPECT I FEEL THAT WE MAY HAVE PERFORMED THE EMER DSCNT EARLIER THAN WE SHOULD HAVE. IN ADDITION; SINCE WE WERE ABOVE FL410 ONE OF US SHOULD HAVE HAD OXYGEN MASK ON AND USING IT. THERE WAS DIFFICULTY IN ESTABLISHING COMS WITH ATC INITIALLY SINCE I DID NOT SELECT THE MASK MIKE AND ATTEMPTED TWICE TO DECLARE THE EMER. I FEEL THAT IN THIS TYPE OF SIT ONE NEEDS TO KNOWS EXACTLY WHAT BUTTONS TO PUSH AND WHERE THEY ARE. ONCE COMS WITH ATC WERE ACCOMPLISHED THEN THE PROB AROSE OF COMMUNICATING WITH EACH OTHER. I FEEL THAT AS A CREW WE WORKED OUT DIFFICULTIES WELL AND HANDLED SIT ACCORDINGLY. IN RETROSPECT; I FEEL IT IS VERY BENEFICIAL TO HAVE ALL NAV SYS UP AND DISPLAYED. ONE NEEDS TO KNOW WHERE YOU ARE AND WHERE YOU COULD GO IF NEEDED. I ALSO FEEL THAT HAVING THE TCASII DISPLAYED AND LOOKING DOWN AT THE MAX RANGE IS VERY BENEFICIAL IN THE EVENT YOU NEED TO COME DONE IMMEDIATELY. IT PROVIDES AN EXTRA MARGIN OF SITUATIONAL AWARENESS.