托福阅读材料之国际空间站

　　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。

　　The crew of the International Space Station have been forced to reducepower after half the cooling system suddenly shut down over the weekend.

　　Nasa officials insisted the three Americans and three Russians aboard werenot in danger.

　　Urgent spacewalk repairs are being discussed for this week.

　　Without thermal controls，temperatures on the ISS‘s Sun-facing side can soarto 121C (250F)，plunging to minus 157C (-250F) on the dark side，Nasa says.

　　“There might be a comfortable spot somewhere in the middle of thestation，but searching for it wouldn’t be much fun，” a statement on its websiteadds.

　　The station is now operating on a single string，the Associated Pressreports，and has no safeguard in case of further cooling system failures.

　　Alarms sound

　　Trouble arose on Saturday night when one of the two ammonia-fed coolingloops shut down，triggering alarms throughout the ISS.

　　The two ammonia lines ensure that all the station‘s electronic equipmentdoes not overheat.

　　Astronaut Tracy Caldwell Dyson set in motion equipment shutdown proceduresand，with crewmate Douglas Wheelock，installed a jumper cable to keep all therooms cool.

　　The Global Positioning System circuit，several power converters and a set ofdevices that route commands to various pieces of equipment were switchedoff.

　　Two of the four gyroscopes - part of the space station’s pointing andnavigating system - were initially shut down but the crew installed a jumpercable to bring up a third gyroscope，leaving the station in a much more stableposition，AP says.

　　Flight controllers tried to restart the disabled ammonia pump early onSunday but the circuit breaker tripped again.

　　Any repairs later this week almost certainly will involve replacing thefaulty ammonia pump，a difficult job that would require two spacewalks，APadds.

　　“It‘s pretty clear that we’re going to want to have a course of action totake as quickly as possible，” Nasa spokesman Rob Navias said at the JohnsonSpace Center in Houston，Texas.

　　“This is not something we want to linger over.”

　　Two spare pumps are stored on the outside of the station. Two of theAmericans on board are already scheduled to conduct a spacewalk on Thursday forroutine maintenance.

　　No space shuttle visits to the ISS are planned before November.