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GPS IIR-1
GPS IIR-1 or GPS SVN-42 was the first Block IIR GPS satellite to be launched. It was to have been operated as part of the United States Air Force Global Positioning System. It was launched on 17 January 1997, however it was destroyed 13 seconds into its flight due to a malfunction of the Delta II rocket that was carrying it.〔 It was estimated to have cost US$40 million, with its carrier rocket costing $55 million. The satellite which was used for the IIR-1 mission was the second production IIR satellite, SVN-42.
==Launch==
GPS IIR-1 was launched on a Delta II 7925-9.5 rocket, serial number D241, from Launch Complex 17A at the Cape Canaveral Air Force Station. The launch occurred at 16:28:01 GMT (11:28 local time), on 17 January 1997. Thirteen seconds later, the rocket's flight termination system was activated by its onboard computer. This detonated explosive charges aboard the rocket, causing it to explode. At the time of explosion, the rocket was above the launch complex. It was the lowest-altitude launch failure at Cape Canaveral since Atlas-Centaur AC-5 in 1965 and only the third total loss of a Delta in the previous two decades.
An investigation determined that the failure was caused by a crack in the casing of the number 2 GEM-40 solid rocket motor, which started to form at T+6 seconds and grew from there.〔 At T+12 seconds, the SRB casing ruptured and debris struck the number 8 SRB next to it, causing that motor to fail as well.〔(【引用サイトリンク】title=NAVSTAR GPS 2R-1 - Summary )〕 One second later, the range safety destruct charges automatically activated, blowing the first stage of the Delta apart and detonating the remaining SRBs. The upper stages were blasted free. At T+21 seconds, the Range Safety Officer sent a manual destruct command to blow them up. The GPS satellite and payload shroud survived intact until impacting the ground. It could not be determined with certainty what had tripped the destruct system on the first stage, possible explanations including a lanyard being pulled, a shock wave from the rupture of the number 2 SRB, or heat generated by the event.
The booster had been damaged by pressure from a support in a new transportation system which had recently been introduced. Following the failure, the system was revised, and ultrasound inspections of boosters on future flights were introduced.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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