发信人: harry901.bbs@ptt.cc (感情学业面包何重要?), 看板: astronomy
标  题: Re: [astronomy]Why the Wait?
发信站: 批踢踢实业 (Thu Jan  8 02:32:38 2004)
转信站: Lion!cbs.ntu!news.nsysu!news.civil.ncku!utopia.leeym.com!freebsd.ntu!en
Origin: victor.m3.ntu.edu.tw

※ 引述《vega1.bbs@cbs.ntu.edu.tw (Vega)》之铭言：
问题跟解答都出来了阿...
: 转贴一则有关天文的问题，原寄者问的问题我很好奇，
: 因为无天文物理基础，也期望有好心人翻译一下，
: 如有侵犯之处请告知我会尽速删除
: Nerd Gerl <nerdgerl@rcip.com>
: http://groups.google.com
: Why are scientists sending objects to Mars at this time, as opposed to
: when Mars was closest to Earth?
为什麽要在这时候将物体送到火星?(我想这个是七八个月的问题)
而不是在火星最接近地球的时候??
: -----
: Douglas Iverson <Squonk-pups@webtv.net>
: WebTV Subscriber
: It has to do with the right angle of approach. Not too steep or shallow
: and the gravitational "slingshot" effect as Earth passes Mars. On the
: lighter, humorous side when you're going 100 million miles what
: difference does a few million more make.
: -----
: David Knisely <ka0czc@navix.net>
: Nerd Gerl wrote:
: > Why are scientists sending objects to Mars at this time, as opposed to
: > when Mars was closest to Earth?
: They are not sending objects to Mars at this time.  The probes which have
: arrived at Mars recently were launched about 7 or 8 months ago.  This was done
: to get them in a minimum-energy trajectory which allowed smaller and less
: expensive launch vehicles to be used.  Mars and the Earth are both moving at
: different speeds in their orbits, so if you launched straight towards Mars
: when Mars was closest to the Earth, Mars would not be there by the time your
: probe got to where Mars was when you launched.  You would have to "lead the
: target" and use a very very large booster to get it going towards Mars if you
: wanted to launch on the date of closest approach.  You would also probably
: have to use a bigger set of retrorockets to slow the spacecraft down so that
: it wouldn't just fly by the planet.  This would reduce the amount of
: scientific payload that you could carry on the spacecraft.  The minimum-energy
: trajectory takes longer for the spacecraft to travel to Mars, but it requires
:   a lot smaller launch vehicle and allows for more payload to be delivered to
: Mars.  Clear skies to you.
我都看得懂  但是懒得一句一句翻译  直接讲原因好了

因为火星与地球的公转周期不一样  所以当火星最接近地球的时候

如果这时把太空船送出去  那麽到时候太空船飞到该火星的位置时

火星已经移到别的地方了

所以这要经过计算  利用两个星球之间的引力  找出最适合发射的时间

这不仅仅可以节省燃料的使用  经费  等问题

还可以在最有利最能掌控的时间之内完成任务


--
ㄟ~~*s
请不要这样看我-.-
我不做黑的-_-

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