游余

Have you noticed what happens if you let theair out of a balloon？ The air goes one way and theballoon moves in the other way. Rockets work inmuch the same way. Waste1 air comes out of therocket at high speed2 and pushes the rocket forward.

Most modern launchers3， such as EuropesAriane 5， are made up of a great number of parts.They are very heavy. Most things in the rockets arefuel4. Rockets need so much fuel to get over Earthsgravity5. Only when they reach a speed of 28，000km/h are they traveling fast enough to get into orbit6.

Most rockets are made up of two or three stages7.When a stage has used up all of its fuel， it breaksaway. It then falls back （usually into the ocean and farfrom people） or burns up in the air.

Large launchers often get another boost8 fromrockets of the first stage. These may use solid9 orliquid10 fuel. They， too， are usually thrown awayafter use.

你有沒有注意到，如果把氣球里的空氣放出來會(huì)發(fā)生什么呢？空氣朝一個(gè)方向流出，而氣球會(huì)朝另一個(gè)方向移動(dòng)?；鸺倪\(yùn)作原理大致相同。廢氣從火箭中高速排出，推動(dòng)火箭前進(jìn)。

大多數(shù)現(xiàn)代發(fā)射器，如歐洲的阿麗亞娜五號(hào)，由很多部分組成。它們很重?；鸺锎蟛糠侄际侨剂??；鸺枰绱硕嗟娜剂喜拍芸朔厍虻囊?。只有當(dāng)它們達(dá)到每小時(shí)28000 公里的速度時(shí)，才能以足夠快的速度進(jìn)入軌道。

大多數(shù)火箭由兩級(jí)或三級(jí)組成。當(dāng)火箭的一級(jí)耗盡了所有燃料后，它就會(huì)分離，然后會(huì)落回地球（通常會(huì)落到海洋中，遠(yuǎn)離人群）或在大氣中燃燒掉。

大型發(fā)射器通常會(huì)從第一級(jí)火箭中獲得更多的動(dòng)力。這些火箭使用的是固體或液體燃料，燃盡之后也會(huì)被丟掉。

Notes

1. waste 材料；物質(zhì)等；廢棄的；無用的

2. speed 運(yùn)動(dòng)；速度

3. launcher 火箭；導(dǎo)彈等的；發(fā)射器；運(yùn)載火箭

4. fuel 燃料；燃燒劑

5. gravity 重力；地心引力

6. orbit 環(huán)繞地球；太陽等運(yùn)行的；軌道

7. stage 火箭的；級(jí)

8. boost 推動(dòng)；促進(jìn)；推動(dòng)力

9. solid 固體的；固態(tài)的

10. liquid [ ] . 液態(tài)的袁液化的