爱华网The space age began on Oct. 4, 1957.太空时代开始了10月4日，1957年。 On that day, the Soviet Union launched Sputnik (later referred to as Sputnik 1), the first artificial satellite to orbit Earth.在那一天，前苏联发射人造地球卫星（后来被称为人造地球卫星1），第一颗人造地球卫星送入轨道。 The first piloted space flight was made on April 12, 1961, when Yuri A. Gagarin, a Soviet cosmonaut, orbited Earth in the spaceship Vostok (later called Vostok 1).第一次驾驶太空飞行是4月12日，1961年，当尤里加加林答，苏联宇航员，飞船运行轨道在地球东方（后来被称为东方1号）。
Unpiloted vehicles called space probes have vastly expanded our knowledge of outer space, the planets, and the stars.无人驾驶车辆称为太空探测器大大拓展了我们的外空，行星，星星的知识。 In 1959, one Soviet probe passed close to the moon and another hit the moon. 1959年，一位苏联探测器月球通过接近月球，另一个打击。 A United States probe flew past Venus in 1962.一个美国探测器飞抵金星在1962年过去。 In 1974 and 1976, the United States launched two German probes that passed inside the orbit of Mercury, close to the sun.在1974年和1976年，美国推出了两个德国探针，水星轨道内的传递，接近太阳。 Two other US probes landed on Mars in 1976.另外两名美国探测器登陆火星于1976年。 In addition to studying every planet except Pluto, space probes have investigated comets and asteroids.除了研究每一个行星冥王星除外，太空探测器研究彗星和小行星。
The first piloted voyage to the moon began on Dec. 21, 1968, when the United States launched the Apollo 8 spacecraft.第一个试点开始向月球航行12月21日，1968年，当美国发动了阿波罗8号飞船。 It orbited the moon 10 times and returned safely to Earth.它绕月球的10倍，并安全返回地球。 On July 20, 1969, US astronauts Neil A. Armstrong and Buzz Aldrin landed their Apollo 11 lunar module on the moon. 7月20日，1969年，美国宇航员尼尔阿姆斯特朗和巴兹奥尔德林在月球上降落的阿波罗11号登月舱。 Armstrong became the first person to set foot on the moon.阿姆斯特朗成为第一个在月球上设置的脚。 United States astronauts made five more landings on the moon before the Apollo lunar program ended in 1972.美国宇航员之前的阿波罗登月计划结束于1972年在月球上五个多着陆。
During the 1970's, astronauts and cosmonauts developed skills for living in space aboard the Skylab and Salyut space stations. 20世纪70年代，航天员和宇航员开发的用于乘坐太空实验室和礼炮号空间站太空生活技能。 In 1987 and 1988, two Soviet cosmonauts spent 366 consecutive days in orbit.在1987年和1988年，苏联宇航员花了两个连续366天的轨道。
On April 12, 1981, the United States space shuttle Columbia blasted off. 4月12日，1981年，美国哥伦比亚号航天飞机升空。 The shuttle was the first reusable spaceship and the first spacecraft able to land at an ordinary airfield.航天飞机是第一个可重复使用的飞船和第一艘能够降落在一个普通的机场。 On Jan. 28, 1986, a tragic accident occurred. 1月28日，1986年，一个悲剧性的事故发生。 The US space shuttle Challenger tore apart in midair, killing all seven astronauts aboard.美国挑战者号航天飞机在空中四分五裂，七名宇航员全部丧生。 The shuttle was redesigned, and flights resumed in 1988.航天飞机进行了重新设计，并于1988年恢复飞行。 A second tragedy struck the shuttle fleet on Feb. 1, 2003.第二个悲剧发生在2003年2月1日的航天飞机。 The Columbia broke apart as it reentered Earth's atmosphere, killing all seven of its crew members.哥伦比亚号解体，因为它重新进入地球大气层，造成其所有的机组人员七。
The solar-powered Helios Prototype aircraft, piloted by remote control, soars above the Hawaiian Islands. 太阳能为动力的太阳神原型飞机，通过遥控器控制试点，在夏威夷群岛上腾飞。 In August 2001, the aircraft reached a record-breaking altitude of 96,863 feet (29,524 meters). 2001年8月，飞机达到了（29524米）破纪录的海拔96863英尺。 Helios, designed by engineers at the National Aeronautics and Space Administration (NASA), tested concepts that could be applied to an aircraft designed to fly in the thin atmosphere of Mars or Earth's upper atmosphere. 太阳神，大气上层设计工程师在美国国家航空和航天局（NASA），测试的概念，可能是地球的应用到飞机设计或火星稀薄的大气中飞行的。 Helios crashed during a test flight in June 2003. 赫利俄斯坠毁在2003年6月试飞研究。 Image credit: NASA 图片来源：NASA
In the early years of the space age, success in space became a measure of a country's leadership in science, engineering, and national defense.在太空时代的最初几年，航天工程成功成为衡量一个国家的领导科学和国防。 The United States and the Soviet Union were engaged in an intense rivalry called the Cold War.美国和苏联是在激烈的竞争从事所谓的冷战。 As a result, the two nations competed with each other in developing space programs. In the 1960's and 1970's, this "space race" drove both nations to tremendous exploratory efforts.结果，两个国家相互竞争的发展空间计划“。在1960年代和1970年代，这个”太空竞赛驱车两个国家极大的探索性的努力。 The space race had faded by the end of the 1970's, when the two countries began to pursue independent goals in space.太空竞赛已经褪色，由空间结束的1970年，当时两国开始在追求独立的目标。
A major dispute in the development of space programs has been the proper balance of piloted and unpiloted exploration.一个在空间计划发展的主要争端一直是试点和无人驾驶探索适当的平衡。 Some experts favor unpiloted probes because they may be cheaper, safer, and faster than piloted vehicles.一些专家赞成无人驾驶探测器，因为他们可能更便宜，更安全，速度比飞行器。 They note that probes can make trips that would be too risky for human beings to attempt.他们指出，探头可以使人次太大，不能企图人类的风险。 On the other hand, probes generally cannot react to unexpected occurrences.另一方面，探头一般不能突然发生的事件作出反应。 Today, most space planners favor a combined, balanced strategy of unpiloted probes and piloted expeditions.今天，多数赞成空间规划相结合，试点的无人驾驶探测器和探险均衡战略。 Probes can visit uncharted regions of space or patrol familiar regions where the data to be gathered fall within expected limits.探头可以访问空间或巡逻的地方要收集的数据在预期范围熟悉的地区属于未知的区域。 But in some cases, people must follow the probes and use human ingenuity, flexibility, and courage to explore the mysteries of the universe.但在某些情况下，人们必须遵循的探针和使用人类的智慧，灵活性和勇于探索宇宙的奥秘。
What is space? 什么是空间？
Space is the near-emptiness in which all objects in the universe move.空间是近空虚在宇宙中移动所有对象。 The planets and the stars are tiny dots compared with the vast expanse of space.行星和恒星的小点相比，广袤的空间。
The beginning of space 年初的空间
Earth is surrounded by air, which makes up its atmosphere.地球周围的空气，它构成了它的大气层。 As the distance from Earth increases, the air becomes thinner.由于距地球距离的增加，空气变得更薄。 There is no clear boundary between the atmosphere and outer space.没有清晰的边界外层空间和大气层之间。 But most experts say that space begins somewhere beyond 60 miles (95 kilometers) above Earth.但多数专家认为，太空60英里以外的地方开始公里）以上的地（95。
Outer space just above the atmosphere is not entirely empty.正上方的大气层外空间并不完全是空的。 It contains some particles of air, as well as space dust and occasional chunks of metallic or stony matter called meteoroids.它包含了一些空气粒子，以及所谓的太空尘埃和流星体的金属或石质的问题偶尔块。 Various kinds of radiation flow freely.各种辐射流动自由。 Thousands of spacecraft known as artificial satellites have been launched into this region of space.众所周知，作为人造卫星发射航天器数以千计的这个空间区域。
Earth's magnetic field, the space around the planet in which its magnetism can be observed, extends far out beyond the atmosphere.地球的磁场，周围是其磁性可以观察到行星的空间，远远超出了大气中。 The magnetic field traps electrically charged particles from outer space, forming zones of radiation called the Van Allen belts.磁场陷阱带电粒子来自外太空，形成辐射区域被称为范艾伦辐射带。
The region of space in which Earth's magnetic field controls the motion of charged particles is called the magnetosphere.区域的空间中，地球的磁场控制带电粒子运动被称为磁层。 It is shaped like a teardrop, with the point extending away from the sun.它的形状像一个泪滴，用点离太阳距离延伸。 Beyond this region, Earth's magnetic field is overpowered by that of the sun.除了这个地区，地球的磁场是浓烈的太阳。 But even such vast distances are not beyond the reach of Earth's gravity.但即使如此巨大的距离不超过地球的引力范围。 As far as 1 million miles (1.6 million kilometers) from Earth, this gravity can keep a satellite orbiting the planet instead of flying off into space.至于一○○○○○○英里距地球（160万公里），这可以保持重力卫星送入太空轨道飞行，而不是离开地球。
Space between the planets is called interplanetary space.行星之间的空间称为行星际空间。 The sun's gravity controls the motion of the planets in this region.太阳的引力控制着这一地区的行星的运动。 That is why the planets orbit the sun.这就是为什么行星轨道的太阳。
Huge distances usually separate objects moving through interplanetary space.巨大的物体移动的距离通常是单独通过星际空间。 For example, Earth revolves around the sun at a distance of about 93 million miles (150 million kilometers).例如，地球围绕在约九千三点○万英里（150万公里）的距离太阳。 Venus moves in an orbit 68 million miles (110 million kilometers) from the sun.金星的轨道移动六八〇〇〇〇〇〇英里（110万公里）从太阳。 Venus is the planet that comes closest to Earth -- 25 million miles (40 million kilometers) away -- whenever it passes directly between Earth and the sun.金星是最接近地球的地球 - 25000000英里（40万公里）远 - 当它通过直接与地球和太阳。 But this is still 100 times as far away as the moon.但是，这仍是100倍，远在月球。
Space between the stars is called interstellar space.恒星之间的空间称为星际空间。 Distances in this region are so great that astronomers do not describe them in miles or kilometers.在这一地区的距离是如此之大，天文学家没有描述他们以英里或公里。 Instead, scientists measure the distance between stars in units called light-years.相反，科学家测量恒星间名为光年单位的距离。 For example, the nearest star to the sun is Proxima Centauri, 4.2 light-years away.例如，在太阳最近的恒星是比邻星，4.2光年。 A light-year equals 5.88 trillion miles (9.46 trillion kilometers).一光年相当于5.88万亿英里（9.46万亿公里）。 This is the distance light travels in one year at its speed of 186,282 miles (299,792 kilometers) per second.这是光在一年的距离旅行在其186282英里每秒（299792公里）速度。
Various gases, thin clouds of extremely cold dust, and a few escaped comets float between the stars.各种气体，极冷尘云淡，少数逃脱彗星恒星之间浮动。 Interstellar space also contains many objects not yet discovered.星际空间还包含许多对象尚未发现。
Launch vehicles used in the United States include the Titan 4 rocket, the Atlas 5 rocket, and the space shuttle. These vehicles carry space probes and artificial satellites into outer space. 启动合众国车辆用于包括泰坦4火箭，阿特拉斯5型火箭，和航天飞机。这些车辆进行空间探测和人造卫星进入太空。 The space shuttle has also carried people and International Space Station modules. 航天飞机还进行人民和国际空间站的模块。 Image credit: World Book illustrations by Oxford Illustrators Limited 图片来源：世界图书有限公司由牛津插图插画
Getting into space and back 获得进入太空和背部
Overcoming gravity is the biggest problem for a space mission.克服重力的太空任务最大的问题。 A spacecraft must be launched at a particular velocity (speed and direction).航天器必须启动一个在特定速度（速度和方向）。
Gravity gives everything on Earth its weight and accelerates free-falling objects downward.地球引力使一切它的重量和加速自由落体对象向下。 At the surface of Earth, acceleration due to gravity, called g, is about 32 feet (10 meters) per second each second.在地球表面，重力加速度，叫G，二是约32英尺（10米）每秒每个。
A powerful rocket called a launch vehicle or booster helps a spacecraft overcome gravity.一个强大的火箭称为运载火箭的航天器或助推器有助于克服重力。 All launch vehicles have two or more rocket sections known as stages. The first stage must provide enough thrust (pushing force) to leave Earth's surface.所有发射车有两个或多个阶段的部分称为火箭。第一阶段必须提供足够的推力（推力）离开地球的表面。 To do so, this stage's thrust must exceed the weight of the entire launch vehicle and the spacecraft.为此，这一阶段的重点必须超过了整个航天器的重量和运载火箭。 The booster generates thrust by burning fuel and then expelling gases.助推器推力产生的气体通过燃烧燃料，然后驱逐出境。 Rocket engines run on a special mixture called propellant. Propellant consists of solid or liquid fuel and an oxidizer, a substance that supplies the oxygen needed to make the fuel burn in the airlessness of outer space.火箭发动机运行在一个特殊的混合物称为推进剂。推进剂空间由固体或液体燃料和氧化剂，这种物质是外需的氧气供应，使燃料在燃烧airlessness。 Lox, or liquid oxygen, is a frequently used oxidizer.液氧，或液态氧，是一种常用的氧化剂。
The minimum velocity required to overcome gravity and stay in orbit is called orbital velocity.所需的最低速度，以克服重力和轨道停留在被称为轨道速度。 At a rate of acceleration of 3 g's, or three times the acceleration due to gravity, a vehicle reaches orbital velocity in about nine minutes.在一个重力加速率的3 G的，或三倍重力加速度，一辆轨道速度达到九分钟左右。 At an altitude of 120 miles (190 kilometers), the speed needed for a spacecraft to maintain orbital velocity and thus stay in orbit is about 5 miles (8 kilometers) per second.第二次在一个海拔120英里（190公里））每需要，为航天器的速度保持这样的速度和轨道停留在轨道英里（8公里，约5。
Launch vehicles used by Asian nations include India's PSLV rocket, China's Long March 3B rocket, and Japan's H-IIA rocket. These vehicles carry space probes and artificial satellites into outer space. 亚洲国家启动车辆使用包括印度的PSLV火箭，中国的长征三号乙火箭，日本的H - IIA的火箭。这些车辆进行空间探测和人造卫星进入太空。 The Long March rocket also launches the Shenzhou spacecraft, which can carry people into orbit. 长征火箭发射的神舟号飞船也，它可以携带进入轨道的人。 Image credit: World Book illustrations by Oxford Illustrators Limited 图片来源：世界图书有限公司由牛津插图插画
In many rocket launches, a truck or tractor moves the rocket and its payload (cargo) to the launch pad.在许多火箭发射，一辆卡车或拖拉机移动火箭，其有效载荷（货物）的发射台。 At the launch pad, the rocket is moved into position over a flame pit, and workers load propellants into the rocket through special pipes.在发射台，火箭进入了一个火焰坑的位置，进了火箭推进剂工人负载通过特殊的管道。
At launch time, the rocket's first-stage engines ignite until their combined thrust exceeds the rocket's weight.在发射时，火箭的第一级发动机点火，直到他们的总推力超过了火箭的重量。 The thrust causes the vehicle to lift off the launch pad.推力使车辆抬离发射台。 If the rocket is a multistage model, the first stage falls away a few minutes later, after its propellant has been used up.如果火箭是一个多阶段模式，第一阶段跌倒了几分钟后，在其推进剂已经用完。 The second stage then begins to fire.第二阶段，然后开始开火。 A few minutes later, it, too, runs out of propellant and falls away.几分钟后，它也耗尽推进剂和跌倒了。 If needed, a small upper stage rocket then fires until orbital velocity is achieved.如果需要的话，小的上面级火箭的轨道速度，然后大火直到实现。
The launch of a space shuttle is slightly different.该航天飞机的发射略有不同。 The shuttle has solid-propellant boosters in addition to its main rocket engines, which burn liquid propellant.穿梭在除了其主火箭发动机，固体推进剂燃烧液体推进剂助推器。 The boosters combined with the main engines provide the thrust to lift the vehicle off the launch pad.与主联合的助推器发动机提供的推力，解除了发射台车辆。 After slightly more than two minutes of flight, the boosters separate from the shuttle and return to Earth by parachute.经过两年多一点的飞行分钟，从航天飞机的助推器和降落伞返回地球分开。 The main engines continue to fire until the shuttle has almost reached orbital velocity.主发动机继续火，直到航天飞机已接近轨道速度。 Small engines on the shuttle push it the remainder of the way to orbital velocity.航天飞机上的小型发动机推的方式对其余的轨道速度。
To reach a higher altitude, a spacecraft must make another rocket firing to increase its speed.为了达到一个更高的高度，航天器必须进行另一次火箭发射，以增加它的速度。 When the spacecraft reaches a speed about 40 percent faster than orbital velocity, it achieves escape velocity, the speed necessary to break free of Earth's gravity.当飞船到达比百分之四十左右的轨道速度更快的速度，它达到逃逸速度，速度必须打破地球的重力作用。
Launch vehicles used by European nations include the European Space Agency's Ariane 5 rocket and Russia's A class and Proton rockets. 欧洲国家启动车辆使用包括欧洲航天局的阿丽亚娜5型火箭和俄罗斯的A类和质子火箭。 These vehicles carry space probes and artificial satellites into outer space. 这些车辆进行空间探测和人造卫星进入太空。 The A Class rocket has also carried people into space, and the Proton rocket has carried International Space Station modules. Image credit: World Book illustrations by Oxford Illustrators Limited A级火箭的人也进行空间之中，与质子火箭已进行国际空间站模块：。图片来源由牛津世界图书插图插画有限公司
Returning to Earth involves the problem of decreasing the spacecraft's great speed.返回地球涉及降低飞船的伟大速度问题。 To do this, an orbiting spacecraft uses small rockets to redirect its flight path into the upper atmosphere.要做到这一点，一个轨道航天器使用小型火箭重定向到大气层上部的飞行路径。 This action is called de-orbit.这个动作被称为脱轨。 A spacecraft returning to Earth from the moon or from another planet also aims its path to skim the upper atmosphere.从一个航天器重返月球或从另一个星球到地球的目的还在于它的路径，撇去上层大气。 Air resistance then provides the rest of the necessary deceleration (speed reduction).空气阻力然后提供必要的减速（减速）休息。
At the high speeds associated with reentering the atmosphere from space, air cannot flow out of the way of the onrushing spacecraft fast enough.在气氛与空间的高重返速度有关，空气不能流通方式走出了飞船的onrushing速度不够快。 Instead, molecules of air pile up in front of it and become tightly compressed.相反，空气分子的堆积在它面前，成为紧紧压缩。 This squeezing heats the air to a temperature of more than 10,000 degrees F (5,500 degrees C), hotter than the surface of the sun.这压缩的空气加热到太阳的温度超过10,000华氏度（5500摄氏度）的，热比表面。 The resulting heat that bathes the spacecraft would burn up an unprotected vehicle in seconds.由此产生的热量，沐浴飞船将在几秒钟内燃烧了一个未受保护的车辆。 Insulating plates of quartz fiber glued to the skin of some spacecraft create a heat shield that protects against the fierce heat.石英纤维隔热板的热粘在皮肤的一些航天器创建一个热保护罩激烈，针对。 Refrigeration may also be used.也可用于制冷。 Early spacecraft had ablative shields that absorbed heat by burning off, layer by layer, and vaporizing.早期的航天器的烧蚀盾牌吸收蒸发热量燃烧掉了，一层又一层，和。
Many people mistakenly believe that the spacecraft skin is heated through friction with the air.许多人错误地认为飞船是通过皮肤与空气摩擦热。 Technically, this belief is not accurate.从技术上讲，这种信念是不准确的。 The air is too thin and its speed across the spacecraft's surface is too low to cause much friction.空气过于薄，其在航天器的表面速度太低，造成多大的摩擦。
For unpiloted space probes, deceleration forces can be as great as 60 to 90 g's, or 60 to 90 times the acceleration due to gravity, lasting about 10 to 20 seconds.对于无人驾驶空间探测器，减速的力量可以作为伟大的60到90克的，或60至90倍的重力加速度大约10到20秒，持久。 Space shuttles use their wings to skim the atmosphere and stretch the slowdown period to more than 15 minutes, thereby reducing the deceleration force to about 11/2 g's.航天飞机用自己的翅膀脱脂大气和舒展放缓至15分钟以上，从而减少了减速力约11 / 2 G的。
When the spacecraft has lost much of its speed, it falls freely through the air.当飞船失去了它的速度快很多，它属于自由地在空气中。 Parachutes slow it further, and a small rocket may be fired in the final seconds of descent to soften the impact of landing.进一步降落伞缓慢，小火箭可能会在最后几秒的后裔发射软化的着陆冲击。 The space shuttle uses its wings to glide to a runway and land like an airplane.航天飞机使用它的翅膀，滑行到跑道，像飞机的土地。 The early US space capsules used the cushioning of water and "splashed down" into the ocean.早期的美国太空舱使用的水缓冲和“溅落”进入海洋。
Living in space 住在太空
When people orbit Earth or travel to the moon, they must live temporarily in space.当人们在地球轨道或月球旅行，他们必须暂时住在太空中。 Conditions there differ greatly from those on Earth.条件有很大的不同，从地球上的人。 Space has no air, and temperatures reach extremes of heat and cold.空间有没有空，气温达到极端炎热和寒冷。 The sun gives off dangerous radiation.太阳散发出危险的辐射。 Various types of matter also create hazards in space.各类物质在太空中也创造危害。 For example, particles of dust called micrometeoroids threaten vehicles with destructive high-speed impacts.例如，所谓的微流星体的尘埃粒子破坏性威胁高速车辆的影响。 Debris (trash) from previous space missions can also damage spacecraft.从以前的空间碎片特派团（垃圾）也破坏飞船。
On Earth, the atmosphere serves as a natural shield against many of these threats.在地球上，大气作为对付这些威胁的许多天然屏障。 But in space, astronauts and equipment need other forms of protection.但在太空中，宇航员和设备需要保护的其他形式。 They must also endure the physical effects of space travel and protect themselves from high acceleration forces during launch and landing.他们还必须忍受太空旅行对身体的影响，并保护在发射和降落高加速力本身。
The basic needs of astronauts in space must also be met.宇航员在太空的基本需求也必须得到满足。 These needs include breathing, eating and drinking, elimination of body wastes, and sleeping.这些需求包括呼吸，进食和饮水，身体废物消除，睡觉。
Protection against the dangers of space 防护空间的危险
Engineers working with specialists in space medicine have eliminated or greatly reduced most of the known hazards of living in space.工程师在航天医学专家合作已经消除或大大减少了在太空生活的已知危害最大。 Space vehicles usually have double hulls for protection against impacts.航天器通常有双重保护对船体的影响。 A particle striking the outer hull disintegrates and thus does not damage the inner hull.一个粒子撞击船体外解体，因此不会损坏内船体。
Astronauts are protected from radiation in a number of ways.宇航员免受辐射的多种方式。 Missions in earth orbit remain in naturally protected regions, such as Earth's magnetic field.留在地球轨道飞行任务在自然保护的地区，如地球的磁场。 Filters installed on spacecraft windows protect the astronauts from blinding ultraviolet rays.航天器的Windows安装的过滤器防止紫外线致盲的宇航员。
The crew must also be protected from the intense heat and other physical effects of launch and landing.船员也必须受到保护，免受高温和强烈的发射和着陆等物理效应。 Space vehicles require a heat shield to resist high temperatures and sturdy construction to endure crushing acceleration forces.航天器隔热板需要抵抗高温，结构坚固忍受破碎加速力。 In addition, the astronauts must be seated in such a way that the blood supply will not be pulled from their head to their lower body, causing dizziness or unconsciousness.此外，宇航员必须坐在这样一种方式，血液供应不会从它们的头，他们的下半身，造成头晕或昏迷。
Aboard a spacecraft, temperatures climb because of the heat given off by electrical devices and by the crew's bodies.一艘飞船，由于气温给予关火电设备和船员的尸体往上爬。 A set of equipment called a thermal control system regulates the temperature.一套设备称为热控系统调节温度。 The system pumps fluids warmed by the cabin environment into radiator panels, which discharge the excess heat into space.该系统由泵将液体加热散热器面板客舱环境，排出多余的热量进入太空。 The cooled fluids are pumped back into coils in the cabin.泵的冷却液是在客舱内回圈。
Microgravity 微重力
An apparently weightless floating makes some tasks challenging inside an orbiting spacecraft. 一个明显失重漂浮使得一些具有挑战性的任务，航天器内的轨道。 In this photograph, a shuttle astronaut struggles with a floating computer printout. 在这张照片中，航天飞机宇航员斗争与浮动计算机打印输出。 Image credit: NASA 图片来源：NASA
Once in orbit, the space vehicle and everything inside it experience a condition called microgravity.一旦进入轨道，航天器，一切都在它里面的经验这种情况称为微重力。 The vehicle and its contents fall freely, resulting in an apparently weightless floating aboard the spacecraft.车辆及其内容属于自由，在一个明显失重导致这艘飞船浮动。 For this reason, microgravity is also referred to as zero gravity.出于这个原因，微重力也被称为零重力。 However, both terms are technically incorrect.但是，这两个方面在技术上是不正确的。 The gravitation in orbit is only slightly less than the gravitation on Earth.在轨道引力只比地球引力少。 The spacecraft and its contents continuously fall toward Earth.该航天器，其内容不断下降对地球。 But because of the vehicle's tremendous forward speed, Earth's surface curves away as the vehicle falls toward it.但由于车辆的前进速度巨大，地球表面的距离为车辆曲线向它的范围。 The continuous falling seems to eliminate the weight of everything inside the spacecraft.连续下跌似乎消除一切航天器内的重量。 For this reason, the condition is sometimes referred to as weightlessness.出于这个原因，条件是有时被称为失重。
Microgravity has major effects on both equipment and people.微重力环境对设备和人员都产生重大影响。 For example, fuel does not drain from tanks in microgravity, so it must be squeezed out by high-pressure gas.例如，燃料不外流，从坦克在微重力，所以它必须被挤压用高压气体。 Hot air does not rise in microgravity, so air circulation must be driven by fans.热空气不能上升，微重力，这样空气流通必须由球迷驱动。 Particles of dust and droplets of water float throughout the cabin and only settle in filters on the fans.粉尘颗粒和水浮液滴整个机舱，只定居在球迷的过滤器。
The human body reacts to microgravity in a number of ways.人类身体对微重力的多种方式。 In the first several days of a mission, about half of all space travelers suffer from persistent nausea, sometimes accompanied by vomiting.在一个特派团开始的几天，约有一半患有太空游客持续恶心，有时伴有呕吐。 Most experts believe that this "space sickness," called space adaptation syndrome, is the body's natural reaction to microgravity.大多数专家认为，这种“空间运动病”，所谓的空间适应综合症，是人体的自然反应，微重力。 Drugs to prevent motion sickness can provide some relief for the symptoms of space adaptation syndrome, and the condition generally passes in a few days.药物预防晕车的空间可为适应综合症的一些症状缓解，条件一般在几天内通过。
Microgravity also confuses an astronaut's vestibular system -- that is, the organs of balance in the inner ear -- by preventing it from sensing differences in direction.微重力也混淆了航天员的前庭系统 - 通过防止感应方向不同了 - 也就是说，在内耳的平衡器官。 After a few days in space, the vestibular system disregards all directional signals.经过几天的空间，前庭系统无视全方位的信号。 Soon after an astronaut returns to Earth, the organs of balance resume normal operation.不久后，宇航员返回地球，平衡的器官恢复正常运作。
Recording medical information on a spacecraft enables physicians to identify any abnormal changes in the body that could indicate physical disorders or stress. 医疗信息记录航天器上使医生能够识别任何不正常的疾病或压力的变化在体内，可能表示身体。 Image credit: NASA 图片来源：NASA
Over a period of days or weeks, an astronaut's body experiences deconditioning. In this process, muscles grow weak from lack of use, and the heart and blood vessels "get lazy."在一个星期内的天，或宇航员的身体经验失调。在这个过程中，从使用的肌肉会变得很脆弱缺乏，心脏和血管的“偷懒”。 Strenuous exercise helps prevent deconditioning.剧烈运动有助于防止失调。 Space travelers ride exercise bikes, use treadmills, and perform other types of physical activity.骑自行车锻炼太空旅行者，使用跑步机，并执行其他类型的体力活动。
After many months in space, a process called demineralization weakens the bones.在太空中经过许多个月，这一过程称为脱矿削弱了骨头。 Most physicians believe that demineralization results from the absence of stress on the bones in a weightless environment.大多数医生认为，从骨头上的压力没有在失重的环境中脱矿的结果。 The experiences of Soviet cosmonauts who spent long periods in orbit showed that vigorous exercise and a special diet can minimize demineralization.是谁花了很长时间在轨苏联宇航员的经验表明，剧烈运动和特殊的饮食可减少脱矿。
Meeting basic needs in space 会议在基本需求空间
Piloted space vehicles have life-support systems designed to meet all the physical needs of the crew members.驾驶车辆的空间设计，以满足所有的机组人员身体的需要生命支持系统。 In addition, astronauts can carry portable life-support systems in backpacks when they work outside the main spacecraft.此外，宇航员可以携带背包便携式生命支持系统时，飞船外的主要工作。
Breathing 呼吸
A piloted spacecraft must have a source of oxygen for the crew to breathe and a means of removing carbon dioxide, which the crew exhales.有人驾驶飞船必须有船员呼吸的氧气来源和消除二氧化碳，呼出的船员手段。 Piloted space vehicles use a mixture of oxygen and nitrogen similar to Earth's atmosphere at sea level.驾驶车辆的使用空间，在海平面的氧和氮的类似地球的大气层的混合物。 Fans circulate air through the cabin and over containers filled with pellets of a chemical called lithium hydroxide.通过循环风机机舱及以上的化学名为氢氧化锂空气颗粒填充的容器。 These pellets absorb carbon dioxide from the air.这些子弹从空气中吸收二氧化碳的碳。 Carbon dioxide can also be combined with other chemicals for disposal.二氧化碳也可以结合其他化学品的处置。 Charcoal filters help control odors.木炭过滤器有助于控制气味。
Eating and drinking 饮食和饮水
The food on a spacecraft must be nutritious, easy to prepare, and convenient to store.飞船上的食品必须营养丰富，容易准备，又方便店。 On early missions, astronauts ate freeze-dried foods -- that is, frozen foods with the water removed.在早期的任务，宇航员吃的冻干食品 - 也就是说，冷冻食品与水移除。 To eat, the astronauts simply mixed water into the food.吃，航天员只需将食物混合水。 Packaging consisted of plastic tubes.包装包括塑料管。 The astronauts used straws to add the water.宇航员用秸秆加水。
Over the years, the food available to space travelers became more appetizing.多年来，食品提供给太空旅行者变得更加美味。 Today, astronauts enjoy ready-to-eat meals much like convenience foods on Earth.今天，宇航员享用现成的吃，就像地球上的方便食品的饭菜。 Many space vehicles have facilities for heating frozen and chilled food.车辆有许多空间加热冷冻和冷藏食品设施。
Water for drinking is an important requirement for a space mission.饮用水是一个空间飞行任务的重要条件。 On space shuttles, devices called fuel cells produce pure water as they generate electricity for the spacecraft.在航天飞机，称为燃料电池设备生产纯净水，因为它们产生的航天器的电力。 On long missions, water must be recycled and reused as much as possible.在执行一项长期任务，必须对水进行回收，并尽可能重用。 Dehumidifiers remove moisture from exhaled air.除湿机去除湿气从呼出的空气。 On space stations, this water is usually reused for washing.在空间站，这通常是重复使用水清洗。
Eliminating body wastes 消除体内废物
The collection and disposal of body wastes in microgravity poses a major challenge.在微重力的搜集和身体废物的处置是一个重大的挑战。 Astronauts use a device that resembles a toilet seat.宇航员使用的设备，类似于一个马桶。 Air flow produces suction that moves the wastes into collection equipment under the seat. On small spacecraft, crew members use funnels for urine and plastic bags for solid wastes. While working outside the spacecraft, astronauts wear special equipment to contain body wastes.
Bathing 沐浴
The simplest bathing method aboard a spacecraft is a sponge bath with wet towels. Astronauts on early space stations used a fully enclosed, collapsible plastic shower stall. This allowed the astronauts to spray their bodies with water, then vacuum the stall and towel themselves dry. Newer space stations have permanent shower stalls.
Sleeping
To sleep aboard a spacecraft, astronauts can zip themselves into sleeping bags strapped to the wall. Blindfolds block the sunlight that streams in the windows periodically during orbit. Image credit: NASA
Space travelers can sleep in special sleeping bags with straps that press them to the soft surface and to a pillow. However, most astronauts prefer to sleep floating in the air, with only a few straps to keep them from bouncing around the cabin. Astronauts may wear blindfolds to block the sunlight that streams in the windows periodically during orbit. Typically, sleep duration in space is about the same as that on Earth.
Recreation 康乐
Recreation on long space flights is important to the mental health of the astronauts. Sightseeing out the spacecraft window is a favorite pastime. Space stations have small collections of books, tapes, and computer games. Exercise also provides relaxation.
Controlling inventory and trash
Keeping track of the thousands of items used during a mission poses a major challenge in space. Drawers and lockers hold some materials. Other equipment is strapped to the walls, ceilings, and floors. Computer-generated lists keep track of what is stored where, and computerized systems check the storage and replacement of materials. The crew aboard the spacecraft may stow trash in unused sections of the vehicle, throw it overboard to burn up harmlessly in the atmosphere, or bring it back to Earth for disposal.
Communicating with Earth
A mission control facility on the earth supervises the activities of astronauts in space. From this center, flight directors communicate with astronauts through the use of television pictures, radio transmissions, computers, and other monitoring equipment. Image credit: NASA
Communication between astronauts in space and mission control, the facility on Earth that supervises their space flight, occurs in many ways. The astronauts and mission controllers can talk to each other by radio. Television pictures can travel between space vehicles and Earth. Computers, sensors, and other equipment continuously send signals to Earth for monitoring. Facsimile machines on spacecraft also can receive information from Earth.
Working in space
Once a space vehicle reaches its orbit, the crew members begin to carry out the goals of their mission. They perform a variety of tasks both inside and outside the spacecraft.
Navigation, guidance, and control
Astronauts use computerized navigation systems and make sightings on stars to determine their position and direction. On Earth, sophisticated tracking systems measure the spacecraft's location in relation to Earth. Astronauts typically use small firings of the spacecraft's rockets to tilt the vehicle or to push it in the desired direction. Computers monitor these changes to ensure they are done accurately.
Activating equipment
Much of the equipment on a space vehicle is turned off or tied down during launch. Once in space, the astronauts must set up and turn on the equipment. At the end of the mission, they must secure it for landing.
Conducting scientific observations and research
Astronauts use special instruments to observe Earth, the stars, and the sun. They also experiment with the effects of microgravity on various materials, plants, animals, and themselves.
Docking 对接
As a spacecraft approaches a target, such as a space station or an artificial satellite, radar helps the crew members control the craft's course and speed. Once the spacecraft reaches the correct position beside the target, it docks (joins) with the target by connecting special equipment. Such a meeting in space is called a rendezvous. A space shuttle can also use its robot arm to make contact with targets.
Maintaining and repairing equipment
The thousands of pieces of equipment on a modern space vehicle are extremely reliable, but some of them still break down. Accidents damage some equipment. Other units must be replaced when they get old. Astronauts must find out what has gone wrong, locate the failed unit, and repair or replace it.
Assembling space stations
Astronauts may serve as construction workers in space, assembling a space station from components carried up in the shuttle. On existing space stations, crews often must add new sections or set up new antennas and solar panels. Power and air connectors must be hooked up inside and outside the station.
Leaving the spacecraft
Flying free in space, an astronaut becomes a human satellite. A jet-powered backpack first used in 1984 allows astronauts to maneuver outside the spacecraft without a safety line. Image credit: NASA
At times, astronauts must go outside the spacecraft to perform certain tasks. Working outside a vehicle in space is called extravehicular activity (EVA). To prepare for EVA, astronauts put on their space suits and move to a special two-doored chamber called an air lock. They then release the air from the air lock, open the outer hatch, and leave the spacecraft. When they return, they close the outer door and let air into the air lock. Then they open the inner door into the rest of the spacecraft, where they remove their space suits.
A space suit can keep an astronaut alive for six to eight hours. The suit is made from many layers of flexible, airtight materials, such as nylon and Teflon. It provides protection against heat, cold, and space particles. Tight mechanical seals connect the pieces of the space suit. Equipment in a backpack provides oxygen and removes carbon dioxide and moisture. A radio enables the astronaut to communicate with other crew members and with Earth. The helmet must allow good visibility while at the same time blocking harmful solar radiation. Gloves are a crucial part of the space suit. They must be thin and flexible enough for the astronaut to feel small objects and to handle tools.
The dawn of the space age
As people began to dream of flying above Earth's surface, they realized that objects in the sky could become destinations for human travelers. In the early 1600's, the German astronomer and mathematician Johannes Kepler became the first scientist to describe travel to other worlds. He also developed the laws of planetary motion that explain the orbits of bodies in space.
The English scientist Sir Isaac Newton first described the laws of motion in a work published in 1687. These laws enabled scientists to predict the kinds of flight paths needed to orbit Earth and to reach other worlds. Newton also described how an artificial satellite could remain in orbit. His third law, which states that for every action there is an equal and opposite reaction, explains why a rocket works.
Early dreams of space flight
During the 1700's, scientists realized that air got thinner at higher altitudes. This meant that air probably was entirely absent between Earth and other worlds, so wings would be useless. Many imaginative writers proposed fanciful techniques for travel to these worlds.
In 1903, Konstantin E. Tsiolkovsky, a Russian high-school teacher, completed the first scientific paper on the use of rockets for space travel. Several years later, Robert H. Goddard of the United States and Hermann Oberth of Germany awakened wider scientific interest in space travel. Working independently, these three men addressed many of the technical problems of rocketry and space travel. Together, they are known as the fathers of space flight.
In 1919, Goddard explained how rockets could be used to explore the upper atmosphere in his paper "A Method of Reaching Extreme Altitudes." The paper also described a way of firing a rocket to the moon. In a book called The Rocket into Interplanetary Space (1923), Oberth discussed many technical problems of space flight. He even described what a spaceship would be like. Tsiolkovsky wrote a series of new studies in the 1920's. These works included detailed descriptions of multistage rockets.
The first space rockets
During the 1930's, rocket research went forward in the United States, Germany, and the Soviet Union. Goddard's team had built the world's first liquid-propellant rocket in 1926, despite a lack of support from the US government. German and Soviet rocket scientists received funding from their governments to develop military missiles.
In 1942, during World War II, German rocket experts under the direction of Wernher von Braun developed the V-2 guided missile. Thousands of V-2's were fired against European cities, especially London, causing widespread destruction and loss of life.
After World War II ended in 1945, many German rocket engineers went to work for the US government to help develop military missiles. The US Navy worked on larger rockets, such as the Aerobee and the Viking. In 1949, the rocket team built and tested the world's first two-stage rocket, with a V-2 missile as a first stage and a small WAC Corporal rocket as a second stage. This rocket reached an altitude of 250 miles (400 kilometers).
By 1947, the Soviet Union had secretly begun a massive program to develop long-range military missiles. In the 1940's, the small but influential British Interplanetary Society published accurate plans for piloted lunar landing vehicles, space suits, and orbital rendezvous. A US group, the American Rocket Society, concentrated on missile engineering. In 1950, a new International Astronautical Federation began to hold annual conferences.
The first artificial satellites
The vehicles shown here helped the United States and the Soviet Union achieve milestones in the exploration of space. The United States no longer builds these rockets, but Russia continues to use the Soviet A Class design in the Soyuz rocket. 这里展示的车辆帮助美国和苏联在实现空间探索的里程碑。美国不再建造这些火箭，但俄罗斯将继续使用联盟号火箭的设计，在苏联的一个类。
• Jupiter C, US Lifted Explorer I, the first US satellite, in 1958. •木星ç，美国解除总管，我在美国第一个卫星，于1958年。 68 feet (21 meters) 68英尺（21米）
• Mercury-Redstone, US Launched Alan Shepard in 1961. •汞红石，在1961年美国发动艾伦谢泼德。 83 feet (25 meters) 八三英尺（25米）
• A Class (Sputnik), Soviet. •一个类（人造卫星），苏联。 Boosted Sputnik 1, the first artificial satellite, in 1957. 带动人造地球卫星1，第一颗人造卫星1957年，在。 98 feet (29 meters) Image credit: WORLD BOOK illustrations by Oxford Illustrators Limited 98英尺（29米）图片来源：牛津插画书籍插图的有限的世界
In 1955, both the United States and the Soviet Union announced plans to launch artificial satellites with scientific instruments on board. 1955年，无论是美国和苏联宣布计划推出使用机载科学仪器人造卫星。 The satellites were to be sent into orbit as part of the International Geophysical Year, a period of international cooperation in scientific research beginning in July 1957.该卫星将进入轨道将作为国际地球物理年，在科学研究的国际合作，开始1957年7月期间的一部分。 The Soviets provided detailed descriptions of the radio equipment to be included on their satellite.苏联提供的无线电设备的详细说明，以对他们的卫星包括在内。 But the Soviet rocket program had been kept secret until that time.但是，苏联火箭方案已经秘而不宣，直到那个时候。 As a result, many people in other countries did not believe that the Soviets had the advanced technology required for space exploration.因此，在其他国家的许多人不相信，苏联拥有先进的技术，太空探索需要。
Then, on Oct. 4, 1957, the Soviets stunned the world by succeeding in their promise -- and by doing so ahead of the United States.然后，在1957年10月4日，苏联在震惊世界的承诺的成功-并通过这样做领先于美国。 Only six weeks earlier, the Soviet two-stage R-7 missile had made its first 5,000-mile (8,000-kilometer) flight. This time, it carried Sputnik (later referred to as Sputnik 1), the first artificial satellite.只有六个星期前，前苏联两个阶段的R - 7导弹已进行了首次5000英里（8000公里）的飞行。这一次，它携带一颗人造卫星（以后简称为人造地球卫星1），第一颗人造卫星。 Sputnik means traveling companion in Russian.人造地球卫星在俄罗斯途径携带的伴侣。 The R-7 booster hurled the 184-pound (83-kilogram) satellite and its main rocket stage into orbit around Earth.的R - 7助推器投掷184磅（83公斤）的卫星及其阶段的主要火箭送入地球轨道附近。 Radio listeners worldwide picked up Sputnik's characteristic "beep-beep" signal.世界各地的电台听众拿起人造卫星的特征“哔哔”的信号。
The vehicles shown here helped the United States and the Soviet Union achieve milestones in the exploration of space. The United States no longer builds these rockets, but Russia continues to use the Soviet A Class design in the Soyuz rocket. 这里展示的车辆帮助美国和苏联在实现空间探索的里程碑。美国不再建造这些火箭，但俄罗斯将继续使用联盟号火箭的设计，在苏联的一个类。
• A Class (Vostok), Soviet. Carried Yuri Gagarin, the first person to orbit the earth, in 1961. •一个类（东方），苏联。尤里加加林携带的第一人，1961年地球轨道，在。 126 feet (38 meters) 126英尺（38米）
• Saturn 5, US Launched Neil Armstrong, the first person to set foot on the moon, in 1969. •土星5号，美国发动尼尔阿姆斯特朗，第一个登上月球上设置了1969年，在。 363 feet (111 meters) Image credit: WORLD BOOK illustrations by Oxford Illustrators Limited 363英尺（111米）图片来源：牛津插画书籍插图的有限的世界
The space race begins 太空竞赛的开始
The Western world reacted to the launch of Sputnik with surprise, fear, and respect.西方世界第一颗人造卫星的反应是惊奇，恐惧，尊重推出。 Soviet Premier Nikita S. Khrushchev ordered massive funding of follow-up projects that would continue to amaze and dazzle the world.苏联总理尼基塔赫鲁晓夫下令学后续项目，将继续对世界感到惊奇和迷惑大量资金。 In the United States, leaders vowed to do whatever was needed to catch up.在美国，领导人发誓要尽一切需要迎头赶上。 Thus the "space race" began.因此，“太空竞赛”开始的。
More Soviet successes followed.更多苏联成功之后。 A month after Sputnik, another satellite, Sputnik 2, carried a dog named Laika into space.一个月后，人造地球卫星，另一颗卫星，人造卫星2，开展名为莱卡送入太空狗。 The flight proved that animals could survive the unknown effects of microgravity.这次飞行证明，动物能够生存微重力未知的影响。 In 1959, Luna 2 became the first probe to hit the moon. 1959年，成为第一个月球探测器2击中月球。 Later that year, Luna 3 photographed the far side of the moon, which cannot be seen from Earth.当年晚些时候，月球3号拍摄到的月亮，这不能从地球上看到的那一边。
The first United States satellite was Explorer 1, launched on Jan. 31, 1958. This satellite was followed by Vanguard 1, which was launched on March 17, 1958. These and later US satellites were much smaller than their Soviet counterparts because the rockets the United States used to carry satellites were smaller and less powerful than those used by the Soviet Union.关于美国的第一颗卫星总管1，启动于1958年1月31日。这颗卫星其次是先锋1，这是1958年3月17日推出。后来美国的卫星，这些均明显小于他们的苏联同行，因为火箭的美国用来进行卫星更小，更强大的苏维埃联盟以外的使用。 The Soviet Union's rockets gave it an early lead in the space race.苏联的火箭给了它一个太空竞赛初带领。 Because bigger rockets would be needed for piloted lunar flight, both the United States and the Soviet Union began major programs of rocket design, construction, and testing.因为更大的火箭将月球飞行驾驶需要，无论是美国和苏联开始和火箭的测试主要方案的设计，建设。
Organizing and managing space activities 空间活动的组织和管理
A key to the ultimate success of US space programs was centralized planning. In 1958, a civilian space agency called the National Aeronautics and Space Administration (NASA) was established.一个美国太空计划的关键，最终成功了集中的计划。1958年，民用航天局称美国国家航空和航天局（NASA）成立。 NASA absorbed various aviation researchers and military space laboratories.美国宇航局的研究人员吸收各种航空和军用空间实验室。 The formation of NASA helped forge agreement among competing interests, including military branches, universities, the aerospace industry, and politicians.美国航天局帮助建立的政治家形成相互竞争的利益的协议，包括军事部门，大学，航天工业，以及。
Soviet space activities, on the other hand, were coordinated by special executive commissions.苏联太空活动的手，另一方面，他们特别执行委员会协调。 These commissions tried to tie together various space units from military and industrial groups, as well as competing experts and scientists. But the commissions did not coordinate Soviet activities effectively enough to meet the complex challenges of the space race.这些委员会试图以配合军事和工业集团一起，从不同的空间单元，科学家以及竞争的专家。但委员会并没有苏联的活动有效地协调，足以满足太空竞赛的复杂挑战。
Space probes 空间探测器
A space probe is an unpiloted device sent to explore space.一个太空探测器是一种无人驾驶设备发送的探索空间。 A probe may operate far out in space, or it may orbit or land on a planet or a moon.一个调查可能远在太空中运行，也可能轨道或在星球或月球的土地。 It may make a one-way journey, or it may bring samples and data back to Earth.它可能使一个单向的旅程，也可能带来的样品和数据传回地球。 Most probes transmit data from space by radio in a process called telemetry.大多数探头发射的无线电遥测的过程中所谓的空间数据。
Lunar and planetary probes that land on their targets may be classified according to their landing method.月球和行星探测器上他们的目标土地，可以按其着陆方法。 Impact vehicles make no attempt to slow down as they approach the target.影响车辆不作任何试图减慢他们接近目标。 Hard-landers have cushioned instrument packages that can survive the impact of a hard landing.硬登陆器有缓冲工具包，能够抵抗硬着陆的影响。 Soft-landers touch down gently.软登陆器着陆平缓。 Penetrators ram deeply into the surface of a target.穿透公羊深入到一个目标的表面。
How a space probe carries out its mission 如何进行太空探测器的使命
Probes explore space in a number of ways.探头探索多种方式的空间。 A probe makes observations of temperature, radiation, and objects in space.阿让在空间探测温度，辐射观测和对象。 A probe also observes nearby objects.调查亦发现附近的一个对象。 In addition, a space probe exposes material from Earth to the conditions of space so that scientists can observe the effects.此外，太空探测器距离地球物质暴露在空间条件，使科学家能够观察其效果。 A probe may also perform experiments on its surroundings, such as releasing chemicals or digging into surface dirt.一个探头也可以执行其环境实验，如化学物质释放到表面的污垢，或发掘。 Finally, a probe's motion enables controllers on Earth to determine conditions in space.最后，一个探头的议案，使地球上的控制器，以确定在空间条件。 Changes in course and speed can provide information about atmospheric density and gravity fields.在课程和速度的变化可以提供有关大气密度和重力场信息。
Early unpiloted explorations 早期的无人驾驶探索
Beginning in the 1940's, devices called sounding rockets carried scientific instruments into the upper atmosphere and into nearby space.在1940年代初，设备称为探空火箭进了附近的高层大气和空间科学仪器进入。 They discovered many new phenomena and took the first photographs of Earth from space.他们发现了许多新现象，并从太空对地球的第一张照片。
The 1957 launch of Sputnik 1 marked the beginning of the space age. 1957年第一颗人造卫星发射1标志着太空时代的开始。 Sputnik 1 carried only a few instruments and transmitters, but it paved the way for the sophisticated probes that would later explore space.人造地球卫星1只进行一些文书和发射器，但它铺平了尖端探针，后来探索太空的方式。
Many early satellites probed uncharted regions of space.许多早期的卫星空间探测未知区域。 During the late 1950's and the 1960's, the Explorer satellites of the United States and the Kosmos satellites of the Soviet Union analyzed the space environment between Earth and the moon.在1950年代后期和1960年代，美国和苏联的宇宙卫星资源管理器分析了卫星地球和月球之间的空间环境。 United States Pegasus satellites recorded the impacts of micrometeorites.美国飞马座卫星记录的微小陨石的影响。 During the early 1970's, Soviet Prognoz satellites studied the sun.在70年代初，苏联Prognoz卫星研究太阳。
Lunar probes 月球探测器
In 1958, both the United States and the Soviet Union began to launch probes toward the moon. 1958年，无论是美国和苏联开始向月球发射探测器。 The first probe to come close to the moon was Luna 1, launched by the Soviet Union on Jan. 2, 1959.第一个探测到接近月亮是月球1，由苏联发射1月2日，1959年。 It passed within about 3,700 miles (6,000 kilometers) of the moon and went into orbit around the sun.它通过在大约700英里的月亮（6000公里），进入轨道围着太阳。 The United States conducted its own lunar fly-by two months later with the probe Pioneer 4.美国开展自己的月球飞行两个月后与探针先锋4。 The Soviet Luna 2 probe, launched on Sept. 12, 1959, was the first probe to hit the moon.苏联月球2探针，在1959年9月12日推出，是第一次探测月球打。 One month later, Luna 3 circled behind the moon and photographed its hidden far side.一个月后，月球3号在月球上空盘旋，并拍摄背后其隐藏的另一侧。
The Soviet Union began to test lunar hard-landers in 1963.苏联于1963年开始测试月球硬登陆器。 After many failures, they succeeded with Luna 9, launched in January 1966.经过多次失败后，他们成功地与月神1966年1月9日推出。 The US Surveyor program made a series of successful soft landings beginning in 1966.美国验船程序作出了一系列的成功软着陆，1966年开始。 Between 1970 and 1972, three Soviet probes returned lunar soil samples to Earth in small capsules. 1970年至1972年，三苏联月球探测土壤样品返回地球，在小胶囊。 Two of them sent remote-controlled jeeps called Lunokhods, which traveled across the lunar surface.其中两人送遥控吉普车所谓Lunokhods，它在月球表面的旅行。
Beginning in 1966, the United States sent five probes called Lunar Orbiters into orbit to photograph the moon's surface.在1966年开始，美国派出5探测器送入轨道，拍摄名为月球表面的月球探测器。 The Lunar Orbiters revealed the existence of irregular "bumps" of gravity in the moon's gravitational field caused by dense material buried beneath the lunar seas.月球轨道器发现的不规则“凸起”在月亮的引力场下的月球重力的海域埋藏密度大的物质所造成的存在。 These areas of tightly packed matter were called mascons, which stood for mass concentrations.问题的紧凑这些地区被称为mascons，这对于质量浓度站着。 If the mascons had not been discovered, they might have interfered with the Apollo missions that sent astronauts to the moon.如果mascons没被发现，他们可能已经干扰了阿波罗登月计划的宇航员送往月球。
The United States space probe Clementine orbited the moon from February to May 1994.美国太空探测器在月球轨道飞行克莱二月至1994年5月。 The probe photographed the moon extensively.该探测器拍摄月球广泛。 In addition, Clementine measured the height and depth of mountains, craters, and other features, and gathered data on mascons.此外，克莱门测量了山，火山口，和其他功能的高度和深度，并聚集在mascons数据。 From January 1998 to July 1999, another US probe, Lunar Prospector, orbited over the moon's poles.从1998年1月至1999年7月，另一位美国探测，月球勘探者，绕在月球的两极。 The probe found strong evidence of large amounts of frozen water mixed with the soil at both poles.探头发现，在与土壤混合两极大量冰水的有力证据。
The SMART-1 probe went into orbit around the moon in November 2004.在SMART - 1探测器进入轨道绕月球2004年11月。 SMART-1 was built and launched by the European Space Agency (ESA), an association of European nations. SMART - 1号的建造和欧洲空间局（ESA），一个欧洲国家协会发起。 The craft's instruments were designed to investigate the moon's origin and conduct a detailed survey of the chemical elements on the lunar surface.飞船的文书，旨在探讨月球的起源和在月球表面进行了详细的调查的化学元素。
Solar probes 太阳能探头
Beginning in 1965, the United States launched a series of small Pioneer probes into orbit around the sun to study solar radiation.在1965年开始，美国推出围绕太阳探测器的小先锋系列研究太阳辐射进入轨道。 Many of these probes were still operating more than 20 years after launch.这些探针许多人仍然经营超过20年后推出。
In 1974 and 1976, the United States launched two German-built Helios probes. These probes passed inside the orbit of Mercury to measure solar radiation. The Ulysses probe was launched in 1990 by the United States and the ESA. In 1994, Ulysses became the first probe to observe the sun from an orbit over the sun's poles.
The surface of Mars was sampled for signs of life by the Viking 2 lander in 1976. A mechanical sampling arm dug the grooves near the round rock at the lower left. The cylinder at the right covered the sampling device and was ejected after landing. The cylinder is about 12 inches (30 centimeters) long. Image credit: NASA/National Space Science Data Center
Probes to Mars
The Soviet Union launched the first probes aimed at another planet, two Mars probes, in 1960. However, neither probe reached orbit. After more Soviet failures, the United States launched two Mariner probes toward Mars in 1964. Mariner 4 flew past the planet on July 14, 1965, and sent back remarkable photographs and measurements. The probe showed that the atmosphere of Mars was much thinner than expected, and the surface resembled that of the moon.
In 1971, the Soviet probe Mars 3 dropped a capsule that made the first soft landing on Mars. However, the capsule failed to return usable data. That same year, the US probe Mariner 9 reached Mars and photographed most of the planet's surface. Mariner 9 also passed near and photographed Mars's two small moons, Phobos and Deimos.
The planet Mars, like Earth, has clouds in its atmosphere and a deposit of ice at its north pole. But unlike Earth, Mars has no liquid water on its surface. The rustlike color of Mars comes from the large amount of iron in the planet's soil. Image credit: NASA/JPL/Malin Space Science Systems
Two US probes, Viking 1 and Viking 2, landed in 1976 and operated for years, measuring surface weather and conducting complex experiments to detect life forms. The probes found no evidence of life.
In 1992, the United States launched the probe Mars Observer. In 1993, NASA lost contact with the probe three days before it would have orbited Mars. Contact was never restored, and the probe was presumed lost.
The United States launched the Pathfinder probe in December 1996. The probe landed on Mars on July 4, 1997. Two days later, a six-wheeled vehicle called Sojourner rolled down a ramp from the probe to the Martian surface. The vehicle was only 24.5 inches long, 18.7 inches wide, and 10.9 inches high (63 by 48 by 28 centimeters). Its mass was 11.5 kilograms, equivalent to a weight of 25.4 pounds on Earth.
Mars Global Surveyor studied the composition of the Martian surface, photographed the surface in detail, and measured its elevation. The space probe went into orbit around Mars in 1997. Image credit: NASA/JPL
The vehicle used a device called an alpha proton X-ray spectrometer to gather data on the chemical makeup of rocks and soil. Sojourner transmitted this information to Pathfinder, and the probe relayed the information to Earth.
Scientists on Earth controlled Sojourner. However, because radio signals take about 10 minutes to travel from Earth to Mars, the scientists could not control Sojourner in real time -- that is, as the vehicle moved. To avoid obstacles, Sojourner used a number of automatic devices.
In 1996, the United States launched a probe called the Mars Global Surveyor to map the planet's surface. The probe used a laser device to determine the elevation of the Martian surface. That instrument produced maps of the entire surface that are accurate to within 3 feet (1 meter) of elevation. Another instrument determined the composition of some of the minerals on the surface. A camera revealed layered sediments that may have been deposited in liquid water, and small gullies that appear to have been carved by water.
The Mars Odyssey probe, shown in this illustration orbiting Mars, found evidence of water ice beneath the surface of Mars in 2002. The probe, launched in 2001, also analyzed the chemical composition of the planet's surface. Image credit: NASA/JPL
In 2001, the United States launched the Mars Odyssey probe to Mars. The craft carried instruments to help identify minerals on the surface, to search for evidence of water and ice beneath the surface, and to measure radiation that might harm any future human explorers. In 2002, Mars Odyssey discovered vast quantities of ice within 3 feet (1 meter) of the surface, most of it near the south pole.
In 2003, three probes were launched to Mars, one by the ESA and two by the United States. The ESA's Mars Express probe went into orbit around the planet in December 2003. It transmitted stunning pictures of the planet's surface, confirmed the presence of water ice in the planet's southern region, and detected methane in the Martian atmosphere, a possible indicator of life. Mars Express carried a lander called Beagle 2 that failed to land safely and was lost.
The United States launched rovers nicknamed Spirit and Opportunity. In January 2004, Spirit landed in Gusev Crater, and Opportunity landed in an area called Meridiani Planum. The rovers used cameras and other instruments to analyze soil and rocks. In March 2004, US scientists concluded that Meridiani Planum once held large amounts of liquid water. Opportunity's analysis had shown that the rock there contained minerals and structures normally found in Earth rocks that formed in water.
Mariner 10 is the only space probe that has visited the planet Mercury. It flew past Venus in 1974, then made three passes near Mercury in 1974 and 1975. A probe called Messenger, launched in 2004, was scheduled to make its first visit to Mercury in 2008. Image credit: NASA
Probes to Venus and Mercury
The Soviet Union launched the first probes toward Venus in 1961, but these attempts failed. The first successful probe to fly past Venus and return data was the US Mariner 2, on Dec. 14, 1962. Mariner 5 flew past Venus in 1967 and returned important data. Mariner 10 passed Venus and then made three passes near Mercury in 1974 and 1975.
Soviet attempts to obtain data from Venus finally succeeded in 1967. Venera 4 dropped a probe by parachute, and it transmitted data from the planet's extremely dense atmosphere. In 1970, Venera 7 reached the surface of the planet, still functioning. Between 1975 and 1985, several other probes landed and conducted observations for up to 110 minutes before the temperature and pressure destroyed them. In 1978, the United States sent two probes to Venus, Pioneer Venus 1 and 2. Pioneer Venus 1 was an orbiter. Pioneer Venus 2 dropped four probes into the planet's atmosphere.
Probes that orbited Venus generated rough maps of its surface by bouncing radio waves off the ground. Pioneer Venus 1 mapped most of the surface to a resolution of about 50 miles (80 kilometers). This means that objects at least 50 miles apart showed distinctly on the map. In 1983, two Soviet probes carried radar systems that mapped most of the planet's northern hemisphere to a resolution of 0.9 mile (1.5 kilometers). In 1990, the US probe Magellan mapped almost the entire surface to a resolution of about 330 feet (100 meters).
In 2004, the United States launched the Messenger probe to Mercury. Messenger was to enter orbit around Mercury in 2011 after flying by Venus twice and by Mercury three times. The probe was to orbit Mercury for one Earth year while mapping Mercury's surface and studying its composition, interior structure, and magnetic field.
Probes to Jupiter and beyond
Probes to Jupiter and beyond must meet special challenges. Radiation belts near Jupiter are so intense that computer circuits must be shielded. The dim sunlight at the outer planets requires lengthy camera exposures. And the vast distances mean that radio commands take hours to reach the probes.
Probes have visited Jupiter, Saturn, Uranus, and Neptune. Only Pluto has not been visited.
US probes Pioneer 10 and Pioneer 11 were sent to Jupiter in 1972 and 1973. After observing Jupiter, Pioneer 11 was redirected toward Saturn, arriving there in 1979. It was renamed Pioneer-Saturn. From 1979 to 1981, sophisticated Voyager probes provided much more detailed data on Jupiter and Saturn. They still explore space. Voyager 2 flew past Uranus in January 1986 and Neptune in August 1989. The probes sent back spectacular photos of the outer planets and their rings and moons, and recorded a great deal of scientific data. Active volcanoes were found on Io, a moon of Jupiter, and geysers were discovered on Triton, a moon of Neptune. Other moons exhibited bizarre ice and rock formations.
The Galileo space probe, launched on a mission to Jupiter by the United States in 1989, was far more sophisticated than earlier planetary probes. It consisted of two parts -- an atmosphere probe and a larger orbiting spacecraft. On the way to Jupiter, Galileo flew past the asteroids Gaspra and Ida. In July 1995, the atmosphere probe separated from the spacecraft. Both parts reached Jupiter five months later. As planned, the probe plunged into Jupiter's atmosphere. The spacecraft orbited Jupiter until 2003, studying the planet, its satellites, and its rings.
In 1997, the United States launched the Cassini probe to investigate Saturn, its rings, and satellites. Cassini carried a separate probe built by the ESA to explore the satellite Titan. Cassini began orbiting Saturn in 2004.
Probes to comets
Two Soviet probes flew past Venus and dropped instruments into its atmosphere, then intercepted Halley's Comet as it passed by the sun in 1986. In 1985, the ESA launched its first interplanetary probe, called Giotto. It passed closer to the comet's nucleus than any other probe and returned dramatic close-up images. Japan also sent two small probes. After several years of inactivity, Giotto was reactivated to fly past the comet Grigg-Skjellerup in July 1992.
The United States did not send a probe to Halley's Comet due to budget limitations. But NASA scientists used a small probe already in space to explore another comet. The International Sun-Earth Explorer 3 satellite had spent several years between Earth and the sun. In 1983, its course was shifted into interplanetary space, and it was renamed the International Cometary Explorer. On Sept. 11, 1985, it passed a comet named Giacobini-Zinner, becoming the first probe to reach a comet.
In 1999, NASA launched a probe called Stardust to visit Comet Wild 2. In 2004, Stardust passed near the comet and gathered samples from the cloud of dust and gas surrounding the comet's nucleus. Stardust was scheduled to return the samples to Earth in 2006. Also in 2004, the European Space Agency launched the Rosetta spacecraft, which was to go into orbit around Comet Churyumov-Gerasimenko in 2014. Rosetta carried a small probe designed to land on the comet's nucleus.
Probes to asteroids
NASA launched the Near Earth Asteroid Rendezvous (NEAR) probe in February 1996. In June 1997, the probe flew within 753 miles (1,216 kilometers) of the asteroid Mathilde. Images produced from NEAR data show that the asteroid is about 40 miles (65 kilometers) wide. Other data indicate that Mathilde is only about as dense as water. Astronomers suspect that the asteroid is so light because it is full of tiny holes.
Craters cover the surface of the asteroid Eros. The asteroid is about 21 miles (33 kilometers) long, about 1 1/2 times the length of Manhattan Island. Image credit: NASA
NEAR flew past the asteroid Eros at a distance of 2,378 miles (3,829 kilometers) in December 1998. Eros is slightly smaller than Mathilde, but about twice as dense as that asteroid. Eros appears to be made of solid rock. NEAR went into orbit around Eros in February 2000. In March 2000, the probe was renamed Near Earth Asteroid Rendezvous-Shoemaker (NEAR-Shoemaker) in honor of American astronomer Eugene Shoemaker. NEAR-Shoemaker landed on Eros in February 2001.
In October 1998, NASA launched a probe called Deep Space 1 (DS1). The probe flew within only about 16 miles (26 kilometers) of the asteroid Braille in July 1999. DS1 failed to return clear images of Braille, which scientists believe is between 0.6 and 3 miles (1 and 5 kilometers) across. However, the flight successfully tested several new types of equipment for space probes. This equipment included a navigation system that operates automatically, rather than under the direction of people and computers on Earth. Also included was an ion rocket, which operates by shooting electrically charged particles called ions out of its nozzle.
Human beings enter space
In 1958, scientists in the United States and the Soviet Union began serious efforts to design a spacecraft that could carry human beings. Both nations chose to develop a wingless capsule atop a launch vehicle that would consist of a modified long-range missile.
The prospect of human beings traveling in space greatly worried scientists. Tests with animals had shown that space travel probably involved no physical danger, but there were serious concerns about possible psychological hazards. Some experts feared that the stresses of launch, flight, and landing might drive a space traveler to terror or unconsciousness.
Vostok and Mercury: The first human beings in space
The Soviet Vostok capsule, left, stood about 16 feet (4.9 meters) high. The US Mercury capsule, center, was 9 1/2 feet (2.9 meters) high. Each vehicle carried one space pilot. The US Gemini spacecraft, right, stood 19 feet (5.8 meters) high and held two astronauts. Image credit: World Book illustration by Oxford Illustrators Limited
The Soviet Union's Vostok (East) program and the Mercury program of the United States represented the first efforts to send a human being into space. The Vostok capsule weighed about 10,000 pounds (4,500 kilograms). It was to be carried into orbit atop a modified R-7 missile. The capsule consisted of a spherical pilot's cabin and a cylindrical service module, the section containing the propulsion system. An ejection seat was designed to provide an escape for the astronaut in case of a mishap during launch. The life-support system used a mixture of oxygen and nitrogen similar to the atmosphere at sea level.
The US Mercury capsule weighed about 3,000 pounds (1,360 kilograms) and was to be carried into space atop a Redstone or Atlas rocket. The cone-shaped capsule would use parachutes to land in the ocean, where the water would provide extra cushioning. The life-support system used pure oxygen at low pressure. In the event of a booster malfunction during launch, the capsule and pilot would be pulled free by a solid-fuel rocket attached to the nose of the capsule.
While US plans proceeded in the glare of publicity, Soviet developments took place in great secrecy. Both nations made unpiloted orbital tests in 1960 and 1961, some of which suffered booster failures. Both nations also sent animals into space during this period. One of these animals was a chimpanzee named Ham, who made an 18-minute flight in a Mercury capsule on Jan. 31, 1961.
The first fatality in a piloted space program occurred on March 23, 1961. A Soviet cosmonaut trainee named Valentin V. Bondarenko burned to death in a pressure chamber fire. Soviet officials covered up the accident.
The first human being in space was a Soviet air force pilot named Yuri A. Gagarin. He was launched aboard Vostok (later referred to as Vostok 1) on April 12, 1961. In 108 minutes, Gagarin orbited Earth once and returned safely. An automatic flight control system managed the spacecraft's operations during the entire flight. A 25-hour, 17-orbit flight by cosmonaut Gherman Titov aboard Vostok 2 followed in August of that year.
The first seven US astronauts, selected for the Mercury program, were, left to right, Donald K. Slayton, Walter M. Schirra, Jr., Gordon Cooper, M. Scott Carpenter, Virgil I. Grissom, John H. Glenn, Jr., and Alan B. Shepard, Jr. Image credit: NASA
The Mercury program made its first piloted flight on May 5, 1961, when a Redstone rocket launched astronaut Alan B. Shepard, Jr., in a capsule he named Freedom 7. Shepard flew a 15-minute suborbital mission -- that is, a mission that did not reach the speed and altitude required to orbit Earth.
A suborbital flight on July 21, 1961, by astronaut Virgil I. Grissom almost ended tragically. The Mercury capsule's side hatch opened too soon after splashdown in the Atlantic Ocean, and the spacecraft rapidly filled with water. Grissom managed to swim to safety.
On Feb. 20, 1962, John H. Glenn, Jr., became the first American to orbit Earth. Glenn completed three orbits in less than five hours. He pointed his capsule in different directions, tested its various systems, and observed Earth.
Three months later, astronaut M. Scott Carpenter repeated Glenn's three-orbit mission. A six-orbit mission by Walter M. Schirra, Jr., in October 1962 further extended the testing of the spacecraft. The final Mercury mission took place in May 1963, with Gordon Cooper aboard. The mission lasted 11/2 days.
Meanwhile, the Soviet Union continued to launch Vostok missions. In August 1962, Vostok 3 and Vostok 4 lifted off just a day apart and passed near each other in space. Another two capsules -- Vostok 5 and Vostok 6 -- were launched in June 1963. One of the pilots spent almost five days in orbit, a new record. The other pilot, Valentina Tereshkova, became the first woman in space.
Voskhod and Gemini: The first multiperson space flights
In 1961, the United States announced the Gemini program, which would send two astronauts into space in an enlarged version of the Mercury capsule. This announcement spurred Soviet planners to modify their Vostok capsule to carry up to three cosmonauts. Political pressure to upstage US efforts was so intense that Soviet engineers sacrificed certain safety features, such as ejection seats, to enlarge the capsule.
The world's first multiperson space capsule, Voskhod (Sunrise) -- later referred to as Voskhod 1 -- was launched on Oct. 12, 1964. Cosmonauts Vladimir M. Komarov, Konstantin P. Feoktistov, and Boris B. Yegorov spent 24 hours in orbit. They became the first space travelers to land inside their capsule on the ground, rather than in the ocean.
In March 1965, cosmonaut Alexei A. Leonov stepped through an inflatable air lock attached to Voskhod 2 to become the first person to walk in space. After the capsule's automatic flight control system failed, Leonov and Pavel I. Belyayev had to land it manually. They missed their planned landing zone and came down in an isolated forest. The cosmonauts had to fend off hungry wolves until rescuers reached them the following day.
The first US astronaut to walk in space was Edward H. White II on June 3, 1965. A 26-foot (8-meter) cord linked White to the Gemini 4 spacecraft during the spacewalk. He controlled his movements in space by using a handheld rocket gun filled with gas. Image credit: NASA
The first piloted Gemini mission, Gemini 3, was launched on March 23, 1965. Astronauts Grissom and John W. Young used the capsule's maneuvering rockets to alter its path through space. With Gemini 4, launched on June 3, 1965, copilot Edward H. White II became the first American to walk in space. The astronauts aboard Gemini 5, launched on Aug. 21, 1965, spent almost eight days in space, a record achieved by using fuel cells to generate electricity.
Gemini 6 was originally intended to link up with an Agena rocket sent into space a few hours earlier. After the unpiloted Agena was lost in a booster failure, NASA combined Gemini 6 with an already scheduled 14-day Gemini 7 mission. Gemini 7 was launched as planned, on Dec. 4, 1965, and Gemini 6 took off 11 days later. Within hours, Schirra and Thomas P. Stafford moved their spacecraft to within 1 foot (30 centimeters) of Gemini 7 and its crew, Frank Borman and James A. Lovell, Jr. The two spacecraft orbited Earth together for several hours before separating.
On March 16, 1966, Gemini 8 completed the world's first docking of two space vehicles when it linked up with an Agena rocket in space. However, the spacecraft went into a violent tumble. Astronauts Neil A. Armstrong and David R. Scott managed to regain control of the spacecraft and make an emergency splashdown in the western Pacific Ocean.
Additional tests of docking and extravehicular activity took place on the remaining four Gemini missions. On these missions, astronauts and flight controllers also gained vital experience in preparation for the tremendous challenges of piloted lunar flight.
Apollo: Mission to the moon
The race to the moon dominated the space race of the 1960's. In a 1961 address to Congress, President John F. Kennedy called for the United States to commit itself to "landing a man on the moon and returning him safely to Earth" before the 1960's ended. This goal was intended to show the superiority of US science, engineering, management, and political leadership.
NASA considered several proposals for a piloted lunar mission. The agency selected a plan known as lunar-orbit rendezvous. A spacecraft would carry three astronauts to an orbit around the moon. Two of the astronauts would then descend to the lunar surface.
The spacecraft would consist of three parts, or modules -- a command module (CM), a service module (SM), and a lunar module (LM), which was originally called the lunar excursion module (LEM). The cone-shaped CM would be the spacecraft's main control center. The SM would contain fuel, oxygen, water, and the spacecraft's electric power system and propulsion system. The CM and SM would be joined for almost the entire mission as the command/service module (CSM).
Only the LM would land on the moon. This module would consist of two sections -- a descent stage and an ascent stage. The two stages would descend to the lunar surface as a single unit, but only the ascent stage would leave the moon.
A Saturn 5 booster would launch the spacecraft toward the moon. As the craft approached the moon, rockets on the SM would adjust its course so that it would go into a lunar orbit. With the craft in orbit, the LM would separate from the CSM and carry the two astronauts to the surface. After the astronauts completed their activities on the moon, the LM's ascent stage would blast off from the descent stage and rendezvous with the CSM.
After the returning astronauts entered the command module, the CSM would cast off the LM's ascent stage. The CSM would then return to Earth. As the craft approached Earth, the CM would separate from the SM and would splash down in the ocean.
Lunar-orbit rendezvous would be complex but relatively economical. The mission would save a tremendous amount of fuel by landing only the small LM on the moon and then launching only its ascent stage.
Making ready
Tragedy struck during preparations for the first piloted Apollo flight, a trial run in low earth orbit. During a ground test on Jan. 27, 1967, a flash fire inside the sealed CM killed astronauts Grissom, White, and Roger B. Chaffee. An electrical short circuit probably started the fire, and the pure oxygen atmosphere caused it to burn fiercely.
A few months later, the Soviet space program also suffered a disaster. The Soyuz (Union) 1 capsule was launched with Vladimir Komarov aboard as pilot. It was supposed to link up with a second piloted spaceship, but Soyuz 1 developed problems and the second ship was never launched. Controllers ordered Soyuz 1 to return to Earth. But a parachute failure caused the capsule to crash, killing Komarov.
While the Apollo CSM and the Soyuz capsule were being redesigned, unpiloted tests took place as planned. The United States launched the first Saturn 5 booster on Nov. 9, 1967, with complete success. Early in 1968, an LM was sent into orbit, where it test-fired its engines. Soyuz vehicles linked up automatically in orbit in 1967 and 1968.
Orbiting the moon
By late 1968, the United States had redesigned the Apollo CSM. However, the lunar module remained far behind schedule.
NASA officials knew about Soviet preparations for a piloted lunar fly-by. To beat the Soviets, NASA decided to fly a piloted mission to orbit the moon, without an LM. The orbital mission would also test navigation and communication around the moon.
Apollo 8, the first piloted expedition to the moon, blasted off from the Kennedy Space Center near Cape Canaveral, Florida, on Dec. 21, 1968. Hundreds of thousands of people crowded nearby beaches to watch the launch. The spacecraft carried astronauts Borman, Lovell, and William A. Anders. After three days, the crew fired the SM engine to change course into a lunar orbit. They made observations and took photographs, then headed back to Earth. Apollo 8 landed safely in the Pacific Ocean near Hawaii on December 27.
Two additional test flights were made to ensure the safety and effectiveness of the lunar module. The LM was tested in low orbit around Earth by the Apollo 9 astronauts and in lunar orbit by the Apollo 10 crew.
Landing on the moon
Apollo 11 was the first mission to land astronauts on the moon. It blasted off on July 16, 1969, carrying three astronauts -- Neil A. Armstrong, Buzz Aldrin, and Michael Collins.
The first two stages of a Saturn 5 rocket carried the spacecraft to an altitude of 115 miles (185 kilometers) and a speed of 15,400 miles (24,800 kilometers) per hour, just short of orbital velocity. The third stage fired briefly to accelerate the vehicle to the required speed. It then shut down while the vehicle coasted in orbit. The astronauts checked the spacecraft and lined up the flight path for the trip to the moon. The third stage was then restarted, increasing the speed to an escape velocity of 24,300 miles (39,100 kilometers) per hour. On the way to the moon, the crew pulled the CSM away from the Saturn rocket. They turned the CSM around and docked it to the LM, which was still attached to the Saturn. The linked vehicles then pulled free of the Saturn.
For three days, Apollo 11 coasted toward the moon. As the spaceship traveled farther from Earth, the pull of Earth's gravity became weaker. But Earth's gravity constantly tugged at the spacecraft, slowing it down. By the time the ship was 215,000 miles (346,000 kilometers) from Earth, its speed had dropped to 2,000 miles (3,200 kilometers) per hour. But then the moon's gravity became stronger than Earth's, and the craft picked up speed again.
Apollo 11 was aimed to pass directly behind the moon. However, it was moving much too fast for the moon's weak gravity to capture it. A braking rocket burn changed its course into a low lunar orbit.
Once in lunar orbit, Armstrong and Aldrin separated the LM from the CSM. They fired the LM's descent stage and began the landing maneuver. They used the LM's rockets to slow its descent. Collins remained in the CSM.
To help NASA mission controllers recognize voice signals from the CSM and the LM, the astronauts used different call signs for the two vehicles. They called the CSM Columbia and the LM Eagle.
The LM's computer controlled all landing maneuvers, but the pilot could override the computer if something unexpected occurred. For the final touchdown, Armstrong looked out the window and selected a level landing site. Probes extended down from the LM's landing legs and signaled when the LM was about 5 feet (1.5 meters) above the surface. The engine shut off, and the LM touched down at a lowland called the Sea of Tranquility on July 20, 1969. Aldrin radioed a brief report on the vehicle's status. Moments later, Armstrong radioed back his famous announcement: "Houston, Tranquility Base here. The Eagle has landed."
Exploring the moon
Immediately after the LM touched down, the astronauts performed a complete check to make sure that the landing had not damaged any equipment. Then they prepared to go outside.
The first people on the moon were US astronauts Neil A. Armstrong, who took this picture, and Buzz Aldrin, who is pictured next to a seismograph. A television camera and a United States flag are in the background. Their lunar module, Eagle, stands at the right. Image credit: NASA
Armstrong and Aldrin had worn space suits during the landing. They transferred their air hoses from a cabin supply to their backpack units, then released the air from the cabin and opened a small hatch below their front windows. First Armstrong and then Aldrin crawled backward through the hatch. They descended a ladder mounted on one of the LM's legs to a wide pad at the base of the leg.
A television camera mounted on the side of the LM sent blurred images of the astronauts back to Earth. Armstrong stepped off the pad onto the moon and said, "That's one small step for a man, one giant leap for mankind." Most of the huge TV audience did not hear Armstrong say the word a before man because of a gap in the transmission.
The astronauts had no trouble adjusting to the weak lunar gravity. They found rocks and soil samples and photographed their positions before picking them up. The astronauts also set up automatic science equipment on the moon. Meanwhile, from the orbiting CSM, Collins conducted various scientific observations and took photographs.
Returning to Earth
The LM's descent stage served as a launch pad for the ascent stage liftoff. To lighten the spacecraft, the crew left all extra equipment behind, including backpacks and cameras. The ascent stage rocketed into orbit, where it linked up with the waiting CSM. The astronauts transferred samples and film into the CSM, then cast off the LM ascent stage. The crew fired the on-board rocket again to push the CSM out of lunar orbit and set their course for Earth.
After splashdown, three balloons righted the Apollo 11 spacecraft in the water, and an orange collar helped keep it afloat. Image credit: NASA
The CM splashed down in the Pacific Ocean on July 24. NASA immediately put the lunar material, the astronauts, and all equipment that had been exposed to the lunar environment into isolation. The purpose of the isolation, which lasted about 17 days for the astronauts, was to determine whether any germs or other harmful material had been brought from the moon. Nothing harmful was found.
The second flight to the moon was as successful as the first. The Apollo 12 LM made a precision landing on the lunar surface on Nov. 19, 1969. Astronauts Charles (Pete) Conrad, Jr., and Alan L. Bean walked to a landed space probe, Surveyor 3, and retrieved samples for study.
The flight of Apollo 13
The flight of Apollo 13, which was supposed to result in the third lunar landing, almost ended in disaster. The flight, from April 11 to 17, 1970, became a mission to save the lives of three astronauts -- James A. Lovell, Jr., Fred W. Haise, Jr., and John L. Swigert, Jr.
During the spacecraft's approach to the moon, one of the two oxygen tanks in the SM exploded. The blast also disabled the remaining tank. The tanks provided both breathing oxygen and fuel for the electrical power systems of the CM and the SM. Moments later, Swigert reported "OK, Houston, we've had a problem."
After the explosion, flight controllers at Mission Control in Houston quickly realized that the astronauts probably did not have enough oxygen and battery power to get them back to Earth. The flight controllers ordered the crew to power up the LM, which was still docked with the CSM. The crew then shut down the CSM, saving its power supply until power would be needed for descent to Earth. The LM had its own power and oxygen supplies, but it was not designed to support three astronauts. The astronauts used only minimal electric power during the 3-day return trip to Earth, and all three of them survived.
A NASA investigation later determined the cause of the tank explosion. Months before the launch, wires leading to a fan thermostat inside the tank had been tested at too high a voltage. As a result, the wire's insulation had burned off. When the fan was turned on during the flight, the wires short-circuited. The short caused a fire in the pure oxygen environment of the tank, resulting in the explosion. The blast blew off one side of the SM and broke the feed line to the other tank.
Other moon landings
Apollo astronauts landed on the moon six times between 1969 and 1972. Each mission brought various instruments to the moon, which usually included a seismograph -- a device that detects and records moonquakes and other small movements of the moon's crust. On later missions, mission controllers sent the empty Saturn third stage and the discarded LM ascent stage hurtling to the moon's surface to create seismic waves. These waves provided information about the moon's internal structure.
An important task of the Apollo astronauts was the recovery of samples from the lunar surface for study. On some flights, they used drills to collect soil samples to a depth of 10 feet (3 meters). Astronauts gathered about 840 pounds (384 kilograms) of samples. Some missions launched small scientific satellites near the moon.
After investigating the Apollo 13 accident, NASA redesigned the CM and SM. The inquiry and modifications set back the Apollo 14 mission from October 1970 to January 1971. The Apollo 14 LM, carrying astronauts Alan B. Shepard, Jr., and Edgar D. Mitchell, landed near Fra Mauro Crater on February 5. Fra Mauro had originally been the target for Apollo 13.
Apollo 15 landed near the Apennine Mountains of the moon on July 30, 1971.阿波罗15号登陆月球附近的亚平宁山脉7月30日，1971年。 Astronauts David R. Scott and James B. Irwin became the first astronauts to drive across the moon's surface. They drove a battery-powered lunar roving vehicle, often called the lunar rover, more than 17 miles (27 kilometers). Apollo 16, carrying John W. Young and Charles M. Duke, Jr., landed in the Descartes region on April 20, 1972. The last lunar mission, Apollo 17, landed in the Taurus Mountains on Dec. 11, 1972. Eugene A. Cernan and Harrison H. Schmitt rode the LM to the surface on this mission.
The Apollo expeditions achieved the goal of demonstrating US technological superiority, and the race to the moon ended with a clear-cut US triumph. Apollo provided unique scientific data, much of which would have been impossible to gather through the use of probes alone. The data enabled scientists to study the origin of the moon and the inner planets of the solar system with much greater certainty than ever before. In addition, the Apollo program forced hundreds of industrial and research teams to develop new tools and technologies that were later applied to more ordinary tasks. For example, microelectronics and new medical monitoring equipment were developed as a result of the Apollo program. These advancements enriched the US economy. Most importantly, the Apollo missions stirred people's imagination and raised their awareness of Earth's place in the universe.
Soviet attempts to reach the moon
The Soviet Soyuz spacecraft could carry three cosmonauts. The capsule stood 23 3/8 feet (7.1 meters) high. Image credit: World Book illustration by Oxford Illustrators Limited
Officials in the Soviet Union publicly denied there had ever been a Soviet equivalent to the Apollo program. This official story became widely accepted around the world. But in the late 1980's, the Soviet Union began to release new information indicating that the Soviet government actually had an ambitious lunar program that failed.
Soviet plans for piloted lunar flight may have been hampered by a lack of central authority. Rivalry among different spacecraft design teams and other space organizations prevented cooperation. The Soviet equivalent of the Apollo CSM was a two-person lunar modification of the Soyuz capsule, called the L-1. The Soviet lunar module, the L-3, resembled the LM developed in the United States. However, it would carry only one cosmonaut. The Soviet booster, the N-1, was bigger than the Saturn 5 but less powerful, because it used less efficient fuels.
Piloted Soviet L-1 capsules were scheduled to fly past the moon as part of a test program. This program was planned for 1966 and 1967, well before the United States could attempt a lunar landing. The Soviet Union conducted unpiloted test flights under the cover name Zond. Three pairs of Soviet cosmonauts trained for a lunar mission.
The Soviet moon ships had serious problems. Many of the boosters for the L-1 lunar fly-by blew up. In addition, the unpiloted L-1 spacecraft developed serious flaws. It was still too dangerous to allow cosmonauts aboard. Soviet efforts to reach the moon were also frustrated by the continued failure of the giant N-1 booster. Four secret test flights were made between 1969 and 1972. However, all of the vehicles exploded.
The Apollo-Soyuz Test Project
In 1972, the United States and the Soviet Union agreed to participate in the first international piloted space mission. They planned to perform an orbital rendezvous between a Soviet Soyuz capsule and a US Apollo capsule. The Apollo-Soyuz Test Project began on July 15, 1975. The Apollo capsule, commanded by Thomas P. Stafford, successfully linked up with the Soyuz capsule, commanded by Alexei A. Leonov.
Space stations
A space station is a place where people can live and work in space for long periods. It orbits Earth, usually about 200 to 300 miles (300 to 480 kilometers) high. A space station may serve as an observatory, laboratory, factory, workshop, warehouse, and fuel depot. Space stations are much larger than piloted spacecraft, so they provide more comforts. Piloted spacecraft may transport people between Earth and the space station. Unpiloted spacecraft may supply the station with food, water, equipment, and mail.
Small space stations can be built on Earth and launched into orbit by large rockets. Larger stations are assembled in space. Rockets or space shuttles carry modules (sections) of the station into space, where astronauts assemble them. Old modules can be replaced, and new modules can be added to expand the station.
A space station has at least one docking port to which a visiting spacecraft can attach itself. Most docking ports consist of a rimmed doorway called a hatch that can connect with a hatch on the visiting spacecraft to form an airtight seal. When the two hatches open, they form a pressurized tunnel between the station and the visiting spacecraft.
The main tasks of a space station crew involve scientific research. For example, they might analyze the effects of microgravity on various materials, investigate Earth's surface, or study the stars and planets.
Astronauts at a space station also devote much of their time to the assembly of equipment and the expansion of the station's facilities. This includes erecting beams, connecting electrical and gas lines, and welding permanent joints between sections of the station. The crew must also fix or replace broken equipment.
Salyut and Skylab
In the 1960's, missions to the moon dominated the US and Soviet space programs. But both countries also developed simple space stations during this period. These early stations had a cylindrical shape, with a docking port at one end and solar power panels sticking out from the sides. The stations were designed to hold enough air, food, and water to last for about 6 to 12 months. The piloted spacecraft originally built for lunar flight -- the US Apollo and the Soviet Soyuz -- were modified to transport people to the space stations.
Salyut
The Soviet Union launched the first space station, Salyut (Salute) 1, on April 19, 1971. It consisted of a single module with one docking port. On June 7, 1971, three cosmonauts -- Georgi T. Dobrovolsky, Victor I. Patsayev, and Vladislav N. Volkov -- linked their Soyuz 11 spacecraft with Salyut 1. They spent 23 days aboard the space station, making medical observations and performing experiments. In a tragic accident, the air leaked out of the Soyuz 11 spacecraft during the return journey, killing all three cosmonauts.
In 1974, Salyut 3 hosted a 15-day mission to photograph Earth. Salyut 4 received two missions in 1975. The second lasted 63 days. In 1976, Salyut 5 repeated the Salyut 3 photography mission.
In 1977, the Soviet Union launched Salyut 6. It had two docking ports, one at either end of the main module. This new design enabled a space station crew to receive a visit from a second crew or a resupply vehicle. A modified, unpiloted Soyuz spacecraft called Progress began delivering new supplies and equipment to Salyut 6 in January 1978. Thus it became the first space station to be resupplied and refueled. These capabilities greatly extended the useful life of space stations and enabled crews to repair and modernize them. Spare parts and more advanced instruments could be sent to the stations as needed. Salyut 6 operated for almost five years. It received visits by 16 crews, who spent up to six months in orbit. Between 1982 and 1986, Salyut 7 housed expeditions lasting up to eight months.
An orbiting solar telescope known as the Solar and Heliospheric Observatory (SOHO) studies the sun's interior, its atmosphere, and the solar wind, a stream of electrically charged particles that flow from the sun's surface. The European Space Agency launched the telescope in 1995. Image credit: NASA/ESA/Solar & Heliospheric Observatory
Skylab
The first US space station was Skylab, launched into orbit by a Saturn 5 booster on May 14, 1973. Skylab was built from the empty third stage of a Saturn 5 rocket, with an attached air lock module, docking port, and solar telescope.
Astronauts Pete Conrad, Joseph P. Kerwin, and Paul J. Weitz arrived at Skylab on May 25. The station had suffered damage during launch, losing most of its thermal insulation and one of its two solar power panels. In addition, debris had jammed the other solar panel so it could not open. The crew worked outside the station several times to free the stuck panel. The success of this 28-day expedition proved the usefulness of people in space for the repair and maintenance of space stations.
Two more crews carried out Skylab missions. These astronauts continued to operate the station while conducting medical experiments, photographing Earth, and observing the sun. The second mission lasted 59 days, and the third ran for 84 days.
United States space officials hoped to keep Skylab in orbit long enough to host a space shuttle mission. However, the station fell from its orbit in July 1979 and broke apart. Fragments of the station landed in western Australia and in the Indian Ocean.
Mir
The Soviet space station Mir (Peace) was launched on Feb. 20, 1986. Mir featured two docking ports -- one at each end -- and four other hatches. They were designed for the attachment of laboratory modules, with the original Mir serving as the hub and the modules looking like spokes of a wheel. Mir also had modernized equipment and improved solar power panels.
After the launch of Mir, the Soviet Union sent three laboratory modules into orbit, where they docked with the core module. Many cosmonauts spent several months in space. Beginning in 1987, each crew was relieved by a new crew before leaving Mir, except for a period of a few months in 1989.
Russia took over the operation of Mir after the Soviet Union broke apart in 1991. In 1994, Russia privatized the government-owned business that was in charge of Mir and other rocket and space projects. The business was given the name Energia Rocket and Space Corporation. In 1995, US space shuttles began to dock with Mir. Russia connected an additional science module to Mir in 1995 and another in 1996, completing the station.
A dangerous accident occurred in June 1997. A cosmonaut was practicing maneuvers that would dock a supply craft with the station. The craft collided with a module of Mir called Spektr. The crash opened a small hole in Spektr and damaged one of its four solar panels. Spektr began to leak air. The crew quickly disconnected the solar-power cables that led through the portal connecting Spektr to the rest of Mir. The crew then closed the hatch, sealing off Spektr.
Mir continued to operate on reduced power. In July 1997, Russia sent emergency supplies and equipment to the station.
In March 2001, Russia destroyed Mir by guiding it into the atmosphere. Much of the station burned, and the remainder fell into the Pacific Ocean.
The International Space Station
Two modules of the International Space Station were launched and assembled in 1998 by the United States and Russia. Image credit: NASA
In 1984, President Ronald Reagan authorized the building of a large, permanent space station "within a decade." Designs for the new station changed often and the estimated cost increased. The promised completion date slipped later and later. In 1993, President Bill Clinton directed NASA to redesign the proposed space station to reduce the cost and amount of time it would take to build. The United States, Brazil, Canada, Japan, Russia, and the ESA would become partners in a program to build the redesigned space station. The International Space Station would be built from several pressurized modules and solar power panels.
Construction began in 1998. Russia launched the first module, called Zarya, in November of that year. A month later, the space shuttle Endeavour carried the module Unity into orbit and docked it with Zarya. A crew of one American astronaut and two Russian cosmonauts moved into the station in 2000.
Space shuttles
During the 1950's and the 1960's, aviation researchers worked to develop winged rocket planes. Advocates of winged spaceplanes pointed out that such vehicles could land on ordinary airfields. Adding wings to a spacecraft increases the vehicle's weight, but wings make landing the vehicle much easier and cheaper than splashdowns at sea. Ocean landings require many ships and aircraft, and the salt water usually damages the spacecraft beyond repair.
NASA began to develop a reusable space shuttle while the Apollo program was still underway. In 1972, US President Richard M. Nixon signed an executive order that officially started the space shuttle project. The shuttles were designed to blast off like a rocket and land like an airplane, making up to 100 missions.
The space shuttle system consists of three parts: (1) an orbiter, (2) an external tank, and (3) two solid rocket boosters. The nose of the winged orbiter houses the pressurized crew cabin. From the flight deck at the front of the orbiter, pilots can look through the front and side windows. The middeck, located under the flight deck, contains additional seats, equipment lockers, food systems, sleeping facilities, and a small toilet compartment. An air lock links the middeck with the payload bay, the area that holds the cargo. The tail of the orbiter houses the main engines and a smaller set of engines used for maneuvering in space.
The external tank is attached to the orbiter's belly. It contains the liquid propellants used by the main engines. Two rocket boosters are strapped to the sides of the external tank. They contain solid propellants.
The designers of the space shuttle had to overcome a number of major technological challenges. The shuttle's main engines had to be reusable for many missions. The shuttle needed a flexible but reliable system of computer control. And it required a new type of heat shield that could withstand many reentries into Earth's atmosphere.
The shuttle era begins
The space shuttle Columbia was launched for the first time in 1981. In 2003, it broke apart as it reentered Earth's atmosphere, and all seven astronauts on board were killed. A shuttle can land like a plane but must be launched attached to two rocket boosters and an external fuel tank. Image credit: NASA
In 1977, NASA conducted flight tests of the first space shuttle, Enterprise, with a modified 747 jumbo jet. The jet carried the orbiter into the air and back on several flights and released it in midair on several more.
The shuttle's first orbital mission began on April 12, 1981. That day, the shuttle Columbia was launched, with astronauts John W. Young and Robert L. Crippen at the controls. The 54-hour mission went perfectly. Seven months later, the vehicle made a second orbital flight, proving that a spacecraft could be reused.
Although the first four shuttle flights each carried only two pilots, the crew size was soon expanded to four, and later to seven or eight. Besides the two pilots, shuttle crews included mission specialists (experts in the operation of the shuttle) and payload specialists (experts in the scientific research to be performed).
The large capacity of the space shuttle's orbiter opened the possibility of including other passengers besides NASA astronauts and scientists. Citizens who participated in shuttle missions included representatives of the companies launching payloads and members of the US Congress.
Sally K. Ride became the first US woman in space on June 18, 1983. In this photograph, Ride eats a meal on the shuttle Challenger during her second shuttle flight in October 1984. Image credit: NASA
In 1984, NASA created a special "Space Flight Participant" program to offer the opportunity of space travel to more Americans. President Reagan announced that the first participant would be a schoolteacher. Later flights were expected to carry journalists, artists, and other interested civilians.
Types of shuttle missions
Space shuttles carry artificial satellites, space probes, and other heavy loads into orbit around Earth. In addition to launch operations, the shuttles can retrieve artificial satellites that need servicing. Astronauts aboard the shuttle can repair the satellites and then return them to orbit. Shuttle crews can also conduct many kinds of scientific experiments and observations.
Commercial satellite launches
The first launch of a payload for a customer took place in November 1982. The shuttle Columbia launched two communications satellites. Solid-rocket boosters helped the satellites climb to their designated orbits. Many later satellite launches followed. NASA discovered that using the space shuttle to launch satellites was more flexible than it had expected. However, the length of time required to ready each space shuttle for its next launch was also greater than NASA planners had expected and sometimes caused expensive delays.
Military missions
About one-fourth of the shuttle missions during the 1980's were conducted for military purposes. Astronauts on these missions sent special observation satellites into orbit and tested various military instruments. To prevent the discovery of information about the capabilities of these satellites, unusual secrecy surrounded the missions. NASA did not reveal launch times of the missions in advance or release any conversations between mission control and the astronauts in space. In the early 1990's, the United States phased out the use of shuttles for such missions and resumed the use of cheaper, single-use rockets.
Shuttle astronauts have performed many challenging missions in space. In 1992, three astronauts worked outside the shuttle Endeavour to capture a communications satellite. Image credit: NASA
Repair missions
The space shuttle enables astronauts to retrieve, repair, and relaunch broken satellites. This important capability was first demonstrated in April 1984, when two astronauts from the shuttle Challenger repaired the Solar Maximum Mission satellite -- the only solar observatory in orbit. This success underscored the flexibility and capability of human beings in space. Since then, astronauts have repaired several other satellites in space.
In 1993, a crew from the shuttle Endeavour repaired the orbiting Hubble Space Telescope. After the telescope had been launched in 1990, NASA engineers discovered an error in its primary mirror. The Endeavour astronauts installed optical equipment that cancelled out the effect of the error. The crew also replaced certain scientific instruments, the solar panels, and the gyroscopes, devices used in pointing the telescope.
Spacelab missions
Spacelab was a facility that enabled shuttle crews to perform a wide variety of scientific experiments in space. It was built as a part of the space shuttle program by the European Space Agency. The first Spacelab mission was launched in 1983 in the space shuttle Columbia. In 1998, the same shuttle carried Spacelab on its last mission. Each mission focused on research in a particular area of science or technology, such as astronomy, the life sciences, and microgravity.
Spacelab consisted of a piloted space laboratory and several separate platforms called pallets. The pressurized laboratory was connected to the crew compartment by a tunnel. It had facilities for scientists to conduct experiments in manufacturing, medicine, the production of biological materials, and other areas. The pallets carried large scientific instruments that were used to conduct experiments in astronomy and other fields. Scientists operated the instruments from the laboratory, from the shuttle's orbiter, or from the ground. Spacelab facilities were shared by the ESA and the United States.
The Challenger disaster
The crew of the last flight of the US space shuttle Challenger consisted of, back row from left, Ellison Onizuka, Christa McAuliffe, Gregory Jarvis, and Judith Resnik; front row from left, Michael Smith, Francis Scobee, and Ronald McNair. All seven crew members were killed on Jan. 28, 1986, when the shuttle broke up shortly after liftoff. Image credit: NASA
The 10th launch of the space shuttle Challenger was scheduled as the 25th space shuttle mission. Francis R. (Dick) Scobee was the mission commander. The crew included Christa McAuliffe, a high-school teacher from New Hampshire. The five other crew members were Gregory B. Jarvis, Ronald E. McNair, Ellison S. Onizuka, Judith A. Resnik, and Michael J. Smith.
After several launch delays, NASA officials overruled the concerns of engineers and ordered a liftoff on a cold morning, Jan. 28, 1986. The mission ended in tragedy. Challenger disintegrated into a ball of fire. The accident occurred 73 seconds into flight, at an altitude of 46,000 feet (14,020 meters) and at about twice the speed of sound.
Strictly speaking, Challenger did not explode. Instead, various structural failures caused the spacecraft to break apart. Although Challenger disintegrated almost without warning, the crew may have briefly been aware that something was wrong. The crew cabin tore loose from the rest of the shuttle and soared through the air. It took almost three minutes for the cabin to fall to the Atlantic Ocean, where it smashed on impact, killing the seven crew members.
All shuttle missions were halted while a special commission appointed by President Reagan determined the cause of the accident and what could be done to prevent such disasters from happening again. In June 1986, the commission reported that the accident was caused by a failure of O rings in the shuttle's right solid rocket booster. These rubber rings sealed the joint between the two lower segments of the booster. Design flaws in the joint and unusually cold weather during launch caused the O rings to allow hot gases to leak out of the booster through the joint. Flames from within the booster streamed past the failed seal and quickly expanded the small hole. The flaming gases then burned a hole in the shuttle's external fuel tank. The flames also cut away one of the supporting beams that held the booster to the side of the external tank. The booster tore loose and ruptured the tank. The propellants from the tank formed a giant fireball as structural failures tore the vehicle apart.
The commission said NASA's decision to launch the shuttle was flawed. Top-level decision-makers had not been informed of problems with the joints and O rings or of the possible damaging effects of cold weather.
Shuttle designers made several technical modifications, including an improved O-ring design and the addition of a crew bail-out system. Although such a system would not work in all cases, it could save the lives of shuttle crew members in some situations. Procedural changes included stricter safety reviews and more restrictive launching conditions.
Back into space
The space shuttle resumed flying on Sept. 29, 1988, with the launch of the redesigned shuttle Discovery. The main purpose of the five-man mission was to place a communications satellite into orbit. During the next few years, many long-delayed missions were carried out. Astronauts launched a number of unpiloted space probes, such as Galileo, Magellan, and Ulysses. Large scientific research satellites such as the Hubble Space Telescope, the Compton Gamma Ray Observatory, and the Upper Atmosphere Research Satellite were placed into orbit. In 1993, a shuttle crew flew to the orbiting Hubble Space Telescope and repaired its optical system.
Shuttles also launched military satellites and communications satellites. Spacelab research missions studied astronomy and space medicine. A less ambitious launch schedule was worked out, and major delays became less frequent.
NASA also made improvements in the shuttle fleet. New computers and life-support hardware were installed. A drag parachute and new brakes made landings easier to control. The computerized automatic flight control system and life-support systems were also improved.
Docking with Mir
A historic docking occurred in 1995, when the United States space shuttle Atlantis, left, became the first US spacecraft to link up with Russia's space station Mir, right. The station had been in orbit around the earth since 1986. A camera mounted in a Russian Soyuz spacecraft took this photograph. Image credit: NASA
Spacecraft from the United States and Russia resumed joint operations in 1995, 20 years after the Apollo-Soyuz mission. On June 29, after three years of negotiations, planning, and practice missions, the space shuttle Atlantis docked with Russia's Mir space station.
Atlantis carried a replacement crew of Russian cosmonauts to Mir and brought the station's former crew home to Earth. Among the returning crew members was astronaut Norman Thagard, who had ridden a Russian rocket to Mir on March 14, 1995. Thagard had spent 115 days in space, breaking the previous US record of 84 days in space.
On March 22, 1995, three cosmonauts who were on Mir when Thagard arrived had made their return voyage to Earth. They included Valery Polyakov, who set an international record of 438 days in space.
Unlike the largely symbolic Apollo-Soyuz mission, the Atlantis-Mir docking was the first in a series of missions. Astronauts began regular visits to Mir, carried up and back by shuttles. The shuttles delivered replacement parts and scientific equipment, as well as water, food, and air. In addition, the astronauts and cosmonauts began to test techniques to be used to build and maintain the International Space Station.
On July 15, 1996, astronaut Shannon Lucid, aboard Mir, broke Thagard's record by spending her 116th consecutive day in space. Lucid had been launched aboard Atlantis on March 22, 1996, and had been on Mir since March 23. On Sept. 7, 1996, Lucid broke the women's record of 168 consecutive days in space. That record had been set by cosmonaut Yelena Kondakova in 1995. On September 26, Lucid returned to Earth aboard Atlantis, having spent 188 consecutive days in space.
The Soviet space shuttle
The Soviet Union carried out its own shuttle program in great secrecy during the 1980's. The Soviet shuttle, Buran (Snowstorm), resembled the US shuttle, but Soviet engineers made many modifications. For example, Buran had no main engines on board. Instead, an expendable booster provided all its launching power.
On Nov. 15, 1988, a heavy booster called Energia carried Buran into orbit without a crew. An automatic flight control system managed the two-orbit flight. Buran landed on a runway at the Baykonur Cosmodrome in Kazakhstan, then part of the Soviet Union.
Beginning in 1989, shortages of funds caused long delays in further development of the Buran program. In 1993, work on the program ended.
The Columbia disaster
The crew of the last flight of the US space shuttle Columbia consisted of, from left to right, David M. Brown, Rick D. Husband, Laurel B. Clark, Kalpana Chawla, Michael P. Anderson, William C. McCool, and Ilan Ramon, the first Israeli astronaut. All seven crew members were killed on Feb. 1, 2003, when the shuttle broke up as it reentered Earth's atmosphere. Image credit: NASA
Disaster struck the US space shuttle fleet again on Feb. 1, 2003, when Columbia, the fleet's oldest shuttle, broke apart over the southwestern United States as it reentered Earth's atmosphere. The flight was Columbia's 28th launch and the shuttle fleet's 113th mission. The accident occurred about 16 minutes before the shuttle was due to land. All seven crew members died, including Rick D. Husband, the mission commander, and Ilan Ramon, the first Israeli astronaut. The five other crew members were Michael P. Anderson, David M. Brown, Kalpana Chawla, Laurel Blair Salton Clark, and William C. McCool.
After the disaster, NASA halted shuttle flights and appointed an independent commission to investigate the accident. Investigators collected thousands of pieces of shuttle debris that had fallen to Earth after the accident. They also studied communications, sensor readings, video recordings, and other records from the mission; tested shuttle equipment; and interviewed NASA employees.
In August, the commission reported that the accident had been caused by a chunk of foam insulation that broke away from the shuttle's external fuel tank and struck Columbia's left wing at high speed shortly after liftoff. Investigators concluded that the impact created a hole in the heat-resistant panels that protected the wing from high temperatures during reentry. As the shuttle reentered Earth's atmosphere, the hole allowed superheated air to enter the wing and damage its internal structure. Eventually, the wing was destroyed, and the shuttle went out of control and broke apart.
The commission's report called for NASA to develop systems for inspecting and repairing protective tiles and panels while the shuttle is in orbit. It recommended reinforcing the panels and working to limit or prevent the shedding of foam from the external fuel tank.
The report also criticized NASA's management and safety procedures. Investigators concluded that pressure to meet budgets and deadlines had contributed to a decline in the safety of the shuttle program. The panel also found that NASA management had failed to act on safety concerns raised by engineers. The report recommended that NASA improve safety procedures and create an independent Technical Engineering Authority to oversee and enforce safety standards.
In 2004, US President George W. Bush announced plans to retire the space shuttle fleet by 2010, following the completion of the International Space Station. Bush proposed replacing the shuttle with a new spacecraft designed to carry astronauts to the moon and, eventually, Mars.
Other nations in space
A number of nations other than the United States and Russia have developed rocket and space programs. These programs are smaller than the US and Russian programs. Most of them concentrate on single applications such as the launching of scientific satellites.
European nations
Several European nations built boosters to launch small scientific research satellites. In 1965, France became the first nation in western Europe to launch a satellite. The United Kingdom sent another satellite into orbit in 1971.
In 1975, the European Space Agency (ESA) was organized. Its western European member nations combine their financial and scientific resources in the development of spacecraft, instruments, and experiments. The ESA supervised the construction of Spacelab, launched the space probe Giotto toward Halley's Comet, and built the Ulysses solar probe. The ESA also developed a series of Ariane booster rockets to launch communications satellites for paying customers. By the late 1980's, Ariane rockets were launching more commercial satellites than US rockets were. ESA spacecraft lift off from Kourou in French Guiana, on the northern coast of South America. See European Space Agency (ESA).
Besides its activities as a member of the ESA, Germany independently built two solar probes called Helios. One probe was launched in 1974, and another was launched in 1976. These probes flew within 28 million miles (45 million kilometers) of the sun -- closer than any other probe had reached.
Japan 日本
Japan became the fourth nation in space when it launched a satellite in February 1970. The nation's space program blossomed in the 1980's. In 1985, Japan fired two probes toward Halley's Comet. Two separate programs developed a family of small, efficient spaceboosters. The H-1 rocket, a medium-sized booster with liquid hydrogen fuel, also became operational. In 1990, Japan launched a lunar probe.
In 1994, Japan launched its first heavy-lifting booster, the H-2. In 1996, an H-2 lofted the Advanced Earth Observing Satellite. The satellite began to gather data on Earth's lands, seas, and atmosphere.
Japan sends small scientific research satellites into orbit from Kagoshima Space Center on the island of Kyushu. Rockets carrying larger satellites take off from Tanegashima Space Center on Tanega Island, about 60 miles (95 kilometers) to the south. Japan is developing a laboratory module for the International Space Station.
China 中国
In April 1970, China sent its first satellite into space aboard a CZ-1 launcher. In the 1980's, China developed impressive space technology that included liquid-hydrogen engines, powerful Long March rockets, and recoverable satellites. China has three satellite launch sites -- Jiuquan, Taiyuan, and Xichang.
In the 1990's, China began developing the Shenzhou, a spacecraft designed to carry astronauts. The Shenzhou resembles Russia's Soyuz capsule. In October 2003, China became the third nation to launch a person into space. Chinese astronaut Yang Liwei orbited Earth aboard a Shenzhou craft for 21 hours before landing safely. Astronauts in the Chinese space program are sometimes called taikonauts.
India 印度
India first launched a satellite into orbit in July 1980. The Indian Space Research Organisation builds boosters. India launches rockets from the island of Sriharikota, off its eastern coast.
Canada 加拿大
Canada has an active space research program and a communications satellite program. That nation took part in the US space shuttle program by designing and building the shuttle's robot arm. Canada also built a larger robot arm that was installed on the International Space Station.
Other nations
Israel sent its first satellite into orbit in 1988. Australia has launched modified US rockets from Woomera, in central Australia. Italy has launched United States rockets from the San Marco platform in the Indian Ocean, off the coast of Kenya. Several countries, including Brazil, Sweden, and South Africa, have sent scientific sounding rockets into space.
Plans for the future
In the early 2000's, scientists and engineers were developing new kinds of spacecraft and more efficient rockets. Industrial researchers were working on manufacturing techniques that would use the space environment to advantage. Encouraged by the commercial potential of space activities, private companies had begun to provide launch services.
Developing new spacecraft
Several organizations were developing technologies for a craft that would replace the space shuttles after 2010. These organizations included NASA, ESA, Japan's National Space Development Agency, and several private companies. Their chief objective was to cut flight costs.
One way to achieve this goal would be to develop a reusable launch vehicle (RLV). All the main parts of an RLV would be reused, giving the craft an advantage over a shuttle. A shuttle's main fuel tank drops away after use and so must be replaced for each flight. In one RLV design, a special airplane would carry a spacecraft to a high altitude and release it. The spacecraft would then fire its own rockets to go into orbit. After completing its mission, the craft would land as an airplane does. Another type of RLV would be a single-stage-to-orbit (SSTO) craft -- a vehicle that would take off by itself and not discard any components. Depending on the design of an SSTO, the craft might take off and land vertically, as a rocket does, or horizontally, as an airplane does.
In the early 2000's, NASA officials decided that an RLV replacement for the shuttle would prove too difficult to develop by 2010. In the meantime, the agency concentrated on developing the Orbital Space Plane (OSP), a reusable spacecraft that would carry crew and light cargo to and from the International Space Station. A disposable booster would carry the OSP into space.
Developing more efficient rockets
Scientists and engineers were working on alternatives to fuel-burning rockets. Two main alternatives were (1) the ion rocket and (2) the nuclear rocket. For a given amount of fuel, both alternatives can create at least twice as much acceleration as a fuel-burning rocket. In addition, both can operate for a long time before running out of fuel. Neither ion rockets nor nuclear rockets would launch spacecraft; they would create thrust after fuel-burning boosters had performed that task.
An ion rocket is an electrical device. Electric energy heats a fuel, converts its atoms to ions (electrically charged atoms), and expels the ions to create thrust. Designers have already used small ion rockets to keep communications satellites in position above Earth. An ion rocket has also propelled a space probe called Deep Space 1 on a mission to asteroids and comets.
A nuclear rocket uses heat from a nuclear reactor to change a liquid fuel into a gas and expel the gas. This kind of rocket would not be practical as a launcher because some radioactive materials might escape into the atmosphere. However, a small nuclear rocket that created thrust continuously could decrease the time of missions to other planets.
Expanding space activities
Two major areas of space utilization have been the gathering and communication of information. Satellites monitor weather systems on Earth, and space probes gather information on the other planets and the sun. Since the 1960's, communications satellites have regularly relayed television signals between points on Earth's surface.
The next major area of space utilization may be the manufacture of medicinal and industrial products. Manufacturers may use the low gravity, high-vacuum environment of space to create substances that are purer or stronger than those produced on Earth. These substances might include drugs; semiconductors, the materials of which computer chips are made; and special alloys (mixtures of metals). As profitable manufacturing processes are developed, private companies may even build and operate "orbiting factories."
Private space flight
Many private companies have begun to develop launch services to compete with the national and international organizations. One firm, Sea Launch Company, boosted a communications satellite from a floating platform in the Pacific Ocean in October 1999. The company used a Ukrainian-built Zenit rocket to launch the satellite. Sea Launch is owned by corporations in the United States, Russia, Norway, and Ukraine.
In 1996, a group of space-flight enthusiasts announced the creation of the X Prize. The group offered a $10 million award to the first privately funded team to build and launch a craft capable of carrying a pilot and two passengers into space. To qualify for the prize, the craft had to fly to an altitude of 62 miles (100 kilometers), land safely, and then make a repeat flight within two weeks. More than 20 teams from many countries registered to compete for the prize. The award was later renamed the Ansari X Prize for a family that donated a large portion of the prize money.
On June 21, 2004, one of the X Prize competitors, Scaled Composites of Mojave, California, became the first private company to launch a person into space. The company's rocket, called SpaceShipOne, carried American test pilot Michael Melvill more than 62 miles above Earth on a brief suborbital test flight. The rocket was launched from a specially designed airplane called the White Knight. SpaceShip0ne went on to win the X Prize with successful launches on Sept. 29 and Oct. 4, 2004.
Contributor: James Oberg, MS, Spaceflight Engineer; author, UFOs and Outer Space Mysteries.
How to cite this article: To cite this article, World Book recommends the following format: Oberg, James. "Space exploration." World Book Online Reference Center. 2004. 2004。 World Book, Inc. http://www.worldbookonline.com/wb/Article?id=ar522550.
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