托福阅读背景知识的积累需要大家在备考中好好准备，相信大家在每天不断的练习中，一定会有不小的进步，一起来看看今天的托福阅读材料之国际空间站冷却系统故障吧。
ThecrewoftheInternationalSpaceStationhavebeenforcedtoreducepowerafterhalfthecoolingsystemsuddenlyshutdownovertheweekend.
NasaofficialsinsistedthethreeAmericansandthreeRussiansaboardwerenotindanger.
Urgentspacewalkrepairsarebeingdiscussedforthisweek.
Withoutthermalcontrols，temperaturesontheISS‘sSun-facingsidecansoarto121C(250F)，plungingtominus157C(-250F)onthedarkside，Nasasays.
“Theremightbeafortablespotsomewhereinthemiddleofthestation，butsearchingforitwouldn’tbemuchfun，”astatementonitswebsiteadds.
Thestationisnowoperatingonasinglestring，theAssociatedPressreports，andhasnosafeguardincaseoffurthercoolingsystemfailures.
Alarmssound
TroublearoseonSaturdaynightwhenoneofthetwoammonia-fedcoolingloopsshutdown，triggeringalarmsthroughouttheISS.
Thetwoammonialinesensurethatallthestation‘selectronicequipmentdoesnotoverheat.
AstronautTracyCaldwellDysonsetinmotionequipmentshutdownproceduresand，withcrewmateDouglasWheelock，installedajumpercabletokeepalltheroomscool.
TheGlobalPositioningSystemcircuit，severalpowerconvertersandasetofdevicesthatroutemandstovariouspiecesofequipmentwereswitchedoff.
Twoofthefourgyroscopes-partofthespacestation’spointingandnavigatingsystem-wereinitiallyshutdownbutthecrewinstalledajumpercabletobringupathirdgyroscope，leavingthestationinamuchmorestableposition，APsays.
FlightcontrollerstriedtorestartthedisabledammoniapumpearlyonSundaybutthecircuitbreakertrippedagain.
Anyrepairslaterthisweekalmostcertainlywillinvolvereplacingthefaultyammoniapump，adifficultjobthatwouldrequiretwospacewalks，APadds.
“It‘sprettyclearthatwe’regoingtowanttohaveacourseofactiontotakeasquicklyaspossible，”NasaspokesmanRobNaviassaidattheJohnsonSpaceCenterinHouston，Texas.
“Thisisnotsomethingwewanttolingerover.”
Twosparepumpsarestoredontheoutsideofthestation.TwooftheAmericansonboardarealreadyscheduledtoconductaspacewalkonThursdayforroutinemaintenance.
NospaceshuttlevisitstotheISSareplannedbeforeNovember.
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