圖文閱讀:神七知識：什麼是第一宇宙速度
The first cosmic speed (V1) spacecraft as the earth's surface along the circular motion must have the speed, also known as speed around. The first two speed of the universe another name: the smallest space launch speed, maximum speed of the spacecraft. In a number of issues that when a spacecraft to the speed of the universe in the first run, it shows that the spacecraft is operating along the Earth's surface. In accordance with the mechanical theory can be calculated V1 = 7.9 km / sec. Spacecraft from the ground a few hundred kilometers above the surface of the high-altitude operation of the spacecraft in the face of gravity on the ground than when it is smaller, so the speed of slightly less than V1.
第二宇宙速度(V2) when the spacecraft in the first over of the universe V1 speed up to a certain value, it will be out of the earth's gravitational field around the sun as a man-made planet, the speed is called第二宇宙速度, also known as escape Speed. In accordance with the mechanical theory can be calculated第二宇宙速度V2 = 11.2 km / sec. As the gravity of the earth the moon has not yet exceeded the scope of it from the ground to launch lunar spacecraft, the initial rate of not less than 10.848 km / s can be.
The third speed of the universe (V3) from the Earth's surface to launch the spacecraft, flying out of the solar system, the vast roaming in the Milky Way need Minimum speed, the speed of the universe is called the third. In accordance with the mechanical theory of the universe can be calculated in the third speed V3 = 16.7 km / sec. It should be noted that this is to choose the speed of the spacecraft orbit the Earth and the revolution speed in the same direction when the calculated value of the V3; if not the direction, speed requirements will be GREater than 16.7 km / s by. It can be said that the speed of the spacecraft is free of the Earth and even the sun's gravitational the only factor, only the speed rockets can break through the universe.
The fourth speed of the universe (V4) of a speed of the universe, objects are expected to have 110 ~ 120km / s speed, you can enter Hewaixingxi out of the Milky Way, known as the pace of the fourth rate of the universe.
As the spacecraft in the Earth's dense atmosphere other than the extremely high vacuum space similar to the natural movement of celestial bodies flying, the first spacecraft to look for the realization of Air and the labor-saving means of delivery.
Does carry a rocket combustion agents, with antioxidants that can fly in space. But to break free of Earth's gravity and fly out to overcome the air resistance of the Earth, single-stage rockets can also be used STEP-ROCKETS relay, one level to speed up the end of the universe to reach the speed of the numerical requirements.
Modern arrows from the launch vehicle body structure, power plants, guidance and control systems, telemetry systems, testing outside the system, security and other self-destructive system constitutes an additional, on all levels between the level inter-agency connectivity, and separation, the spacecraft mounted on the end of the The location of the rocket to the top level by the end of grade separation and institutions linked to the rocket; outside the spacecraft equipped with a fairing, in order to launch the initial phase of the protection of the spacecraft.
The launch vehicle technology indicators, including the carrying capacity, precision orbit, rockets of different weights in the spacecraft's reliability and adaptability. And the weight of the spacecraft orbit, the rocket needed to provide energy and speed varies, with a variety of track between the speed of a certain relationship. If the spacecraft into a 185 km high circular orbit required speed of 7.8 km / s; spacecraft into the 1,000 km high circular orbit required speed of 8.3 km / s; spacecraft Into the geosynchronous transfer orbit speed of 10.25 kilometers requirements / s; spacecraft to detect the speed of the solar system requirements for 12 to 20 km / s, and so on. To this day, the Rockets can only rely on breakthroughs in the speed of the universe, the realization of the ideals of human space flight.
第一宇宙速度（V1） 航天器沿地球表面作圓周運動時必須具備的速度，也叫環繞速度。第一宇宙速度兩個別稱：航天器最小發射速度、航天器最大運行速度。在一些問題中說，當某航天器以第一宇宙速度運行，則說明該航天器是沿着地球表面運行的。按照力學理論可以計算出V1＝7．9公里／秒。航天器在距離地面表面數百公里以上的高空運行，地面對航天器引力比在地面時要小，故其速度也略小於V1。
第二宇宙速度（V2）當航天器超過第一宇宙速度V1達到一定值時，它就會脫離地球的引力場而成爲圍繞太陽運行的人造行星，這個速度就叫做第二宇宙速度，亦稱逃逸速度。按照力學理論可以計算出第二宇宙速度V2＝11．2公里／秒。由於月球還未超出地球引力的範圍，故從地面發射探月航天器，其初始速度不小於10．848公里／秒即可。
第三宇宙速度（V3）從地球表面發射航天器，飛出太陽系，到浩瀚的銀河系中漫遊所需要的最小速度，就叫做第三宇宙速度。按照力學理論可以計算出第三宇宙速度V3＝16．7公里／秒。需要注意的是，這是選擇航天器入軌速度與地球公轉速度方向一致時計算出的V3值；如果方向不一致，所需速度就要大於16．7公里／秒了。可以說，航天器的速度是掙脫地球乃至太陽引力的惟一要素，目前只有火箭才能突破宇宙速度。
第四宇宙速度（V4）宇宙速度的一級，預計物體具有110~120km/s的速度時，就可以脫離銀河系而進入河外星系，這個速度叫做第四宇宙速度。
由於航天器在地球稠密大氣層以外極高真空的宇宙空間以類似自然天體的運動規律飛行，所以實現航天首先要尋找不依賴空氣而又省力的運載工具。
火箭本身既攜有燃燒劑，又帶有氧化劑，能夠在太空中飛行。但要掙脫地球引力和克服空氣阻力飛出地球，單級火箭還做不到，必須用多級火箭接力，逐級加速，最終才能達到宇宙速度要求的數值。
現代運載火箭由箭體結構、動力裝置、制導和控制系統、遙測系統、外測系統、安全自毀和其他附加系統構成，各級之間靠級間段和分離機構連接，航天器裝在末級火箭的頂端位置，通過分離機構與末級火箭相連；航天器外面裝有整流罩，以便在發射初始階段保護航天器。
運載火箭的技術指標，包括運載能力、入軌精度、火箭對不同重量的航天器的適應能力和可靠性。航天器的重量和軌道不同，所需火箭提供的能量和速度也各不相同，各種軌道與速度之間有一定的對應關係。如把航天器送入185公里高的圓形軌道運行所需的速度爲7．8公里／秒；航天器進入1000公里高的圓形軌道運行所需速度爲8．3公里／秒；航天器進入地球同步轉移軌道運行所需速度爲10．25公里／秒；航天器探測太陽系所需速度爲12～20公里／秒等。直到今天，只有依靠火箭才能突破宇宙速度，實現人類飛天的理想。
