Space exploration
<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" rowspan="2" width=210 BGCOLOR="#9999FF" TEXT="#080000" bgproperties="fixed" background="09376ba3.gif"> <bR> <bR> <bR> <div> <A HREF="future_files.htm" TARGET="_top" TITLE="Astronomy Future files"><U>Astronomy Future files</U></A></div> <bR> <div> <A HREF="space_exploration_m.htm#top_of_page" TARGET="TRLX_Middle" TITLE="Space exploration"><U><I><B>Top of page</B></I></U></A></div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B>Links in this page:</B></div> <div> <A HREF="space_exploration_m.htm#the_began_of_space_age" TARGET="TRLX_Middle" TITLE="Space exploration"><U>The began of space age</U></A></div> <bR> <div> <A HREF="space_exploration_m.htm#space_explorationwhat_is_space_" TARGET="TRLX_Middle" TITLE="Space exploration"><U><B>SPACE EXPLORATION/What Is Space?</B></U></A></div> <div> <A HREF="space_exploration_m.htm#the_beginning_of_space" TARGET="TRLX_Middle" TITLE="Space exploration"><U>The Beginning of Space</U></A></div> <bR> <div> <A HREF="space_exploration_m.htm#space_explorationgetting_into_space" TARGET="TRLX_Middle" TITLE="Space exploration"><U><B>SPACE EXPLORATION/Getting Into </B></U></A><A HREF="space_exploration_m.htm#space_explorationgetting_into_space" TARGET="TRLX_Middle" TITLE="Space exploration"><U><B>Space and Back</B></U></A> </div> <div> <A HREF="space_exploration_m.htm#preparing_the_spacecraft" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Preparing the Spacecraft</U></A></div> <div> <A HREF="space_exploration_m.htm#space_explorationliving_in_space" TARGET="TRLX_Middle" TITLE="Space exploration"><U><B>SPACE EXPLORATION/Living in Space</B></U></A><B> </B></div> <div> <A HREF="space_exploration_m.htm#protection_against_the_dangers_of_space" TARGET="TRLX_Middle" TITLE="Space exploration"><U><B>Protection Against the Dangers of Space</B></U></A></div> <div> <A HREF="space_exploration_m.htm#microgravity" TARGET="TRLX_Middle" TITLE="Space exploration"><U><B>Microgravity </B></U></A></div> <div> <A HREF="space_exploration_m.htm#meeting_basic_needs_in_space" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Meeting Basic Needs in Space</U></A> </div> <div> <A HREF="space_exploration_m.htm#breathing" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Breathing</U></A></div> <div> <A HREF="space_exploration_m.htm#eating_and_drinking" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Eating and Drinking</U></A></div> <div> <A HREF="space_exploration_m.htm#eliminating_body_wastes" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Eliminating Body Wastes</U></A></div> <div> <A HREF="space_exploration_m.htm#bathing" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Bathing</U></A></div> <div> <A HREF="space_exploration_m.htm#sleeping" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Sleeping</U></A></div> <div> <A HREF="space_exploration_m.htm#recreation" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Recreation</U></A></div> <div> <A HREF="space_exploration_m.htm#communicating_with_the_earth" TARGET="TRLX_Middle" TITLE="Space exploration"><U><B>Communicating With the Earth</B></U></A></div> <div> <A HREF="space_exploration_m.htm#working_in_space" TARGET="TRLX_Middle" TITLE="Space exploration"><U><B>Working in Space</B></U></A></div> <div> <A HREF="space_exploration_m.htm#navigation_guidance_and_control" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Navigation, Guidance, and Control</U></A></div> <div> <A HREF="space_exploration_m.htm#activating_equipment" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Activating Equipment</U></A></div> <div> <A HREF="space_exploration_m.htm#docking" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Docking</U></A></div> <div> <A HREF="space_exploration_m.htm#maintaining_and_repairing_equipment" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Maintaining and Repairing Equipment</U></A></div> <div> <A HREF="space_exploration_m.htm#assembling_space_stations" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Assembling Space Stations</U></A></div> <div> <A HREF="space_exploration_m.htm#leaving_the_spacecraft" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Leaving the Spacecraft</U></A></div> <bR> <div> <A HREF="space_exploration_m.htm#top_of_page" TARGET="TRLX_Middle" TITLE="Space exploration"><U><I><B>Top of page</B></I></U></A></div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <A HREF="space_exploration_m.htm#space_explorationthe_dawn_of_the_space" TARGET="TRLX_Middle" TITLE="Space exploration"><U><B>SPACE EXPLORATION/The Dawn of the Space Age</B></U></A></div> <div> <A HREF="space_exploration_m.htm#early_dreams_of_space_flight" TARGET="TRLX_Middle" TITLE="Space exploration"><U>Early Dreams of Space Flight</U></A></div> <div> <A HREF="space_exploration_m.htm#the_first_space_rockets" TARGET="TRLX_Middle" TITLE="Space exploration"><U>The First Space Rockets</U></A></div> <bR> </td> <td 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<div> Space exploration</div> <div> <A NAME="top_of_page"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Space exploration is our human response to curiosity about the earth, the moon, the planets, the sun and other stars, and the galaxies. Manned and unmanned space vehicles venture far beyond the boundaries of the earth to collect valuable information about the universe. Human beings have visited the moon and have lived in space stations for long periods. Space exploration helps us see the earth in its true relation with the rest of the universe. Such exploration could reveal how the sun, the planets, and the stars were formed and whether life exists beyond our own world.</div> <bR> <div> <A NAME="the_began_of_space_age"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>The space age began on Oct. 4, 1957. On that day, the Soviet Union launched Sputnik (later referred to as Sputnik 1), the first artificial satellite to orbit the earth. The first manned space flight was made on April 12, 1961, when Yuri A. Gagarin, a Soviet cosmonaut, orbited the earth in the spaceship Vostok (later called Vostok 1).</div> <bR> <div> Unmanned vehicles called space probes have vastly expanded our knowledge of outer space, the planets, and the stars. In 1959, one Soviet probe passed close to the moon and another hit the moon. A United States probe flew past Venus in 1962. In 1974 and 1976, the United States launched two German probes that passed inside the orbit of Mercury, close to the sun. Two other U. S. probes landed on Mars in 1976. In addition to studying every planet except Pluto, space probes have investigated comets and asteroids.</div> <bR> <div> The first manned voyage to the moon began on Dec. 21, 1968, when the United States launched the Apollo 8 spacecraft. It orbited the moon 10 times and returned safely to the earth. On July 20, 1969, U. S. astronauts Neil A. Armstrong and Edwin E. Aldrin, Jr. , landed their Apollo 11 lunar module on the moon. Armstrong became the first person to set foot on the moon. United States astronauts made five more landings on the moon before the Apollo lunar program ended in 1972.</div> <bR> <div> During the 1970's, astronauts and cosmonauts developed skills for living in space aboard the Skylab and Salyut space stations. In 1987 and 1988, two Soviet cosmonauts spent a record 366 consecutive days in orbit.</div> <bR> <div> On April 12, 1981, the U. S. space shuttle Columbia blasted off. The shuttle was the first reusable spaceship and the first spacecraft able to land at an ordinary airfield. On Jan. 28, 1986, a tragic accident occurred. The U. S. space shuttle Challenger tore apart in midair, killing all seven astronauts aboard. The shuttle was redesigned, and flights resumed in 1988.</div> <bR> <div> During the early years of the space age, success in space became a measure of a country's leadership in science, engineering, and national defense. The United States and the Soviet Union were engaged in an intense rivalry called the Cold War. As a result, the two nations competed with each other in developing their space programs. Throughout the 1960's and 1970's, this "space race" drove both nations to tremendous exploratory efforts. But the competition often emphasized showmanship over science. The space race had faded by the end of the 1970's, when the United States and the Soviet Union began to pursue independent goals in space. Today, space programs are characterized by a steadier pace and by more international cooperation.</div> <bR> <div> A major dispute in the development of space programs has been the proper balance of manned and unmanned exploration. Some experts favor unmanned probes because they may be cheaper, safer, and faster than manned vehicles. They note that probes can make trips that would be too risky for human beings to attempt. On the other hand, probes generally cannot react to unexpected occurrences. Today, most space planners favor a combined, balanced strategy of unmanned probes and manned expeditions. Probes can visit uncharted regions of space or patrol familiar regions where the data to be gathered fall within expected limits. But in some cases, people must follow the probes and use human ingenuity, flexibility, and courage to explore the mysteries of the universe.</div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B> <A NAME="space_explorationwhat_is_space_"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>SPACE EXPLORATION/What Is Space?</B></div> <bR> <div> Space is the near-emptiness in which all objects in the universe move. The planets, the stars, and even the swarms of billions of stars called galaxies are tiny dots compared with the vast expanse of space.</div> <bR> <div> <A NAME="the_beginning_of_space"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>The Beginning of Space</div> <div> The earth is surrounded by air, which makes up its atmosphere. As the distance from the earth increases, the air becomes thinner. There is no clear boundary between the atmosphere and outer space. But most experts say that space begins somewhere beyond 60 miles (95 kilometers) above the earth.</div> <bR> <div> Outer space just above the atmosphere is not entirely empty. It contains some particles of air, as well as space dust and occasional chunks of metallic or stony matter called meteoroids. Various kinds of radiation flow freely. Thousands of spacecraft known as artificial satellites have been launched into this region of space.</div> <bR> <div> The earth's magnetic field, the space around the planet in which its magnetism can be observed, extends far out beyond the atmosphere. The magnetic field traps electrically charged particles from outer space, forming zones of radiation called the Van Allen belts.</div> <bR> <div> The region of space in which the earth's magnetic field controls the motion of charged particles is called the magnetosphere. It is shaped like a teardrop, with the point extending away from the sun. Beyond this region, the earth's magnetic field is overpowered by that of the sun. But even such vast distances are not beyond the reach of the earth's gravity. As far as 1 million miles (1. 6 million kilometers) from the earth, this gravity keeps satellites orbiting the planet instead of flying off into space.</div> <bR> <div> Space Between the Planets is called interplanetary space. The sun's gravity controls the motion of the planets in this region. That is why the planets orbit the sun.</div> <bR> <div> Huge distances usually separate objects moving through interplanetary space. For example, the earth revolves around the sun at a distance of about 93 million miles (150 million kilometers). Venus moves in an orbit 68 million miles (110 million kilometers) from the sun. Venus is the planet that comes closest to the earth--25 million miles (40 million kilometers) away--whenever it passes directly between the earth and the sun. But this is still 100 times as far away as the moon.</div> <bR> <div> Space Between the Stars is called interstellar space. Distances in this region are so great that astronomers do not describe them in miles or kilometers. Instead, scientists measure the distance between stars in units called light-years. For example, the nearest star to the sun is Proxima Centauri, 4. 3 light-years away. A light-year equals 5. 88 trillion miles (9. 46 trillion kilometers). This is the distance light travels in one year at its speed of 186,282 miles (299,792 kilometers) per second.</div> <bR> <div> Various gases, thin clouds of extremely cold dust, and a few escaped comets float between the stars. Interstellar space also contains many objects not yet discovered.</div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B> <A NAME="space_explorationgetting_into_space"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>SPACE EXPLORATION/Getting Into Space and Back</B></div> <bR> <div> Space exploration involves great technical challenges. A spacecraft must be launched at a particular velocity (speed and direction). A space vehicle that carries a crew must also be able to slow down and land safely.</div> <bR> <div> <A NAME="preparing_the_spacecraft"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Preparing the Spacecraft</div> <div> Manufacturers build space vehicles in special factories under extremely clean conditions. The slightest contamination could introduce flaws that might later cause equipment failure. The vehicle is then transported to the launch site by truck, rail, aircraft, or barge. There, crews assemble and test the spacecraft to make sure it is in working order. When a vehicle is ready for flight, workers move it to a launch pad for fueling.</div> <bR> <div> Overcoming Gravity is the biggest problem for a space mission. Gravity gives everything on the earth its weight and makes free-falling objects accelerate downward. At the surface of the earth, acceleration due to gravity, called g, is about 32 feet (10 meters) per second each second.</div> <bR> <div> A powerful rocket called a launch vehicle helps a spacecraft overcome gravity. All launch vehicles have two or more rocket sections known as stages. The first stage must provide enough thrust (pushing force) to leave the earth's surface. To do so, the booster's thrust must exceed its weight. The excess force--that is, the thrust minus the weight of the vehicle--accelerates the spacecraft and lifts it into the sky. The booster generates thrust by burning fuel and then expelling gases. 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. Lox, or liquid oxygen, is a frequently used oxidizer.</div> <bR> <div> The minimum velocity required to overcome gravity and stay in space is called orbital velocity. 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. 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.</div> <bR> <div> In many rocket launches, a truck or tractor moves the rocket and its payload (cargo) to the launch pad. At the launch pad, the rocket is moved into position over a flame pit, and workers load propellants into the rocket through special pipes.</div> <bR> <div> At launch time, the rocket's first-stage engines ignite until their combined thrust exceeds the rocket's weight. The thrust causes the vehicle to lift off the launch pad. If the rocket is a multistage model, the first stage falls away a few minutes later, after its propellant has been used up. The second stage then begins to fire. A few minutes later, it, too, runs out of propellant and falls away. If needed, a small upper stage rocket then fires until orbital velocity is achieved.</div> <bR> <div> The launch of a space shuttle is slightly different. The shuttle has solid-propellant boosters in addition to its main rocket engines, which burn liquid propellant. The boosters combined with the main engines provide the thrust to lift the vehicle off the launch pad. After slightly more than two minutes of flight, the boosters separate from the shuttle and return to the earth by parachute. The main engines continue to fire until the shuttle has almost reached orbital velocity. Small engines on the shuttle push it the remainder of the way to orbital velocity.</div> <bR> <div> To reach a higher altitude, a spacecraft must make another rocket firing to increase its speed. When the spacecraft reaches a speed about 40 per cent faster than orbital velocity, it achieves escape velocity, the speed necessary to break free of the earth's gravity.</div> <bR> <div> Returning to the Earth involves the problem of decreasing the spacecraft's great speed. To do this, an orbiting spacecraft uses small rockets to redirect its flight path into the upper atmosphere. This action is called de-orbit. A spacecraft returning to the earth from the moon or from another planet also aims its path to skim the upper atmosphere. Air resistance then provides the rest of the necessary deceleration (speed reduction).</div> <bR> <div> At the high speeds associated with reentering the atmosphere from space, air cannot flow out of the way of the onrushing spacecraft fast enough. Instead, molecules of air pile up in front of it and become tightly compressed. 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. The resulting heat that bathes the spacecraft would burn up an unprotected vehicle in seconds. Insulating plates of quartz fiber glued to the skin of some spacecraft create a heat shield that protects against the fierce heat. Refrigeration may also be used. Early spacecraft had ablative shields that absorbed heat by burning off, layer by layer, and vaporizing.</div> <bR> <div> Many people mistakenly believe that the spacecraft skin is heated through friction with the air. Technically, this belief is not accurate. The air is too thin and its speed across the spacecraft's surface is too low to cause much friction.</div> <bR> <div> For unmanned 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. 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 1 1/2 g's.</div> <bR> <div> When the spacecraft has lost much of its speed, it falls freely through the air. Parachutes slow it further, and a small rocket may be fired in the final seconds of descent to soften the impact of landing. Some spacecraft, including the space shuttle, use their wings to glide to a runway and land like an airplane. The early U. S. space capsules used the cushioning of water and "splashed down" into the ocean.</div> <bR> <div> <B> <A NAME="space_explorationliving_in_space"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>SPACE EXPLORATION/Living in Space</B></div> <bR> <div> When people orbit the earth or travel to the moon, they must live temporarily in space. Conditions there differ greatly from those on the earth. Space has no air, and temperatures reach extremes of heat and cold. The sun gives off dangerous radiation. Various types of matter also create hazards in space. For example, particles of dust called micrometeoroids threaten vehicles with destructive high-speed impacts. Debris (trash) from previous space missions can also damage spacecraft.</div> <bR> <div> On the earth, the atmosphere serves as a natural shield against many of these threats. But in space, astronauts and equipment need other forms of protection. They must also endure the physical effects of space travel and protect themselves from high acceleration forces during launch and landing.</div> <bR> <div> The basic needs of astronauts in space must also be met. These needs include breathing, eating and drinking, elimination of body wastes, and sleeping.</div> <bR> <div> <B> <A NAME="protection_against_the_dangers_of_space"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>Protection Against the Dangers of Space</B></div> <bR> <div> Engineers working with specialists in space medicine have eliminated or greatly reduced most of the known hazards of living in space. Space vehicles usually have double hulls for protection against impacts. A particle striking the outer hull disintegrates and thus does not damage the inner hull.</div> <bR> <div> Astronauts are protected from radiation in a number of ways. Missions in earth orbit remain in naturally protected regions, such as the earth's magnetic field. Filters installed on spacecraft windows protect the astronauts from blinding ultraviolet rays.</div> <bR> <div> The crew must also be protected from the intense heat and other physical effects of launch and landing. Space vehicles require a heat shield to resist high temperatures and sturdy construction to endure crushing acceleration forces. 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.</div> <bR> <div> Aboard a spacecraft, temperatures climb because of the heat given off by electrical devices and by the crew's bodies. A set of equipment called a thermal control system regulates the temperature. The system pumps fluids warmed by the cabin environment into radiator panels, which discharge the excess heat into space. The cooled fluids are pumped back into coils in the cabin.</div> <bR> <div> <B> <A NAME="microgravity"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>Microgravity</B></div> <bR> <div> Once in orbit, the space vehicle and everything inside it experience a condition called microgravity. The vehicle and its contents fall freely, resulting in an apparently weightless floating aboard the spacecraft. For this reason, microgravity is also referred to as zero gravity. However, both terms are technically incorrect. The gravitation in orbit is only slightly less than the gravitation on the earth. The spacecraft and its contents continuously fall toward the earth. But because of the vehicle's tremendous forward speed, the earth's surface curves away as the vehicle falls toward it. The continuous falling seems to eliminate the weight of everything inside the spacecraft. For this reason, the condition is sometimes referred to as weightlessness.</div> <bR> <div> Microgravity has major effects on both equipment and people. For example, fuel does not drain from tanks in microgravity, so it must be squeezed out by high-pressure gas. Hot air does not rise in microgravity, so air circulation must be driven by fans. Particles of dust and droplets of water float throughout the cabin and only settle in filters on the fans.</div> <bR> <div> The human body reacts to microgravity in a number of ways. In the first several days of a mission, about half of all space travelers suffer from persistent nausea, sometimes accompanied by vomiting. Most experts believe that this "space sickness," called space adaptation syndrome, is the body's natural reaction to microgravity. 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.</div> <bR> <div> 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. After a few days in space, the vestibular system disregards all directional signals. Soon after an astronaut returns to the earth, the organs of balance resume normal operation.</div> <bR> <div> 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. "Strenuous exercise helps prevent deconditioning. Space travelers ride exercise bikes, use treadmills, and perform other types of physical activity.</div> <bR> <div> After many months in space, a process called demineralization weakens the bones. Most physicians believe that demineralization results from the absence of stress on the bones in a weightless environment. The experiences of Soviet cosmonauts who spent long periods in orbit showed that vigorous exercise and a special diet can minimize demineralization.</div> <bR> <div> <A NAME="meeting_basic_needs_in_space"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Meeting Basic Needs in Space</div> <bR> <div> Manned space vehicles have life-support systems designed to meet all the physical needs of the crew members. In addition, astronauts can carry portable life-support systems in backpacks when they work outside the main spacecraft.</div> <bR> <div> <A NAME="breathing"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Breathing</div> <div> A manned spacecraft must have a source of oxygen for the crew to breathe and a means of removing carbon dioxide, which the crew exhales. Manned space vehicles use a mixture of oxygen and nitrogen similar to the earth's atmosphere at sea level. Fans circulate air through the cabin and over containers filled with pellets of a chemical called lithium hydroxide. These pellets absorb carbon dioxide from the air. Carbon dioxide can also be combined with other chemicals for disposal. Charcoal filters help control odors.</div> <bR> <div> <A NAME="eating_and_drinking"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Eating and Drinking</div> <div> The food on a spacecraft must be nutritious, easy to prepare, and convenient to store. On early missions, astronauts ate freeze-dried foods--that is, frozen foods with the water removed. To eat, the astronauts simply mixed water into the food. Packaging consisted of plastic tubes. The astronauts used straws to add the water.</div> <bR> <div> Over the years, the food available to space travelers became more appetizing. Today, astronauts enjoy ready-to-eat meals much like convenience foods on the earth. Many space vehicles have facilities for heating frozen and chilled food.</div> <bR> <div> Water for drinking is an important requirement for a space mission. On space shuttles, devices called fuel cells produce pure water as they generate electricity for the spacecraft. On long missions, water must be recycled and reused as much as possible. Dehumidifiers remove moisture from exhaled air. On space stations, this water is usually reused for washing.</div> <bR> <div> <A NAME="eliminating_body_wastes"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Eliminating Body Wastes</div> <div> The collection and disposal of body wastes in microgravity poses a major challenge. Astronauts use a device that resembles a toilet seat. 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.</div> <bR> <div> <A NAME="bathing"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Bathing</div> <div> 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.</div> <bR> <div> <A NAME="sleeping"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Sleeping</div> <div> 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 the earth.</div> <bR> <div> <A NAME="recreation"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>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.</div> <bR> <div> Controlling Inventory and Trash</div> <div> 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 the earth for disposal.</div> <bR> <div> <B> <A NAME="communicating_with_the_earth"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>Communicating With the Earth</B></div> <bR> <div> Communication between astronauts in space and mission control, the facility on the 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 the earth. Computers, sensors, and other equipment continuously send signals to the earth for monitoring. Facsimile machines on spacecraft also can receive information from the earth.</div> <bR> <div> <B> <A NAME="working_in_space"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>Working in Space</B></div> <bR> <div> 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.</div> <bR> <div> <A NAME="navigation_guidance_and_control"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Navigation, Guidance, and Control</div> <div> Astronauts use computerized navigation systems and make sightings on stars to determine their position and direction. On the earth, sophisticated tracking systems measure the spacecraft's location in relation to the 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.</div> <bR> <div> <A NAME="activating_equipment"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Activating Equipment</div> <div> 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.</div> <bR> <div> Conducting Scientific Observations and Research</div> <div> Astronauts use special instruments to observe the earth, the stars, and the sun. They also experiment with the effects of microgravity on various materials, plants, animals, and themselves.</div> <bR> <div> <A NAME="docking"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Docking</div> <div> 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.</div> <bR> <div> <A NAME="maintaining_and_repairing_equipment"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Maintaining and Repairing Equipment</div> <div> 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.</div> <bR> <div> <A NAME="assembling_space_stations"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Assembling Space Stations</div> <div> 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.</div> <bR> <div> <A NAME="leaving_the_spacecraft"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Leaving the Spacecraft</div> <div> 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.</div> <bR> <div> 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 the 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.</div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B> <A NAME="space_explorationthe_dawn_of_the_space"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>SPACE EXPLORATION/The Dawn of the Space Age</B></div> <bR> <div> As people began to dream of flying above the 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.</div> <bR> <div> In 1687, the English scientist Sir Isaac Newton first described the laws of motion. These laws enabled scientists to predict the kinds of flight paths needed to orbit the 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.</div> <bR> <div> <A NAME="early_dreams_of_space_flight"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Early Dreams of Space Flight</div> <div> During the 1700's, scientists realized that air got thinner at higher altitudes. This meant that air probably was entirely absent between the earth and other worlds, so wings would be useless. Many imaginative writers proposed fanciful techniques for travel to these worlds.</div> <bR> <div> 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.</div> <bR> <div> 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.</div> <bR> <div> <A NAME="the_first_space_rockets"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>The First Space Rockets</div> <div> 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 U. S. government. German and Soviet rocket scientists received funding from their governments to develop military missiles.</div> <bR> <div> 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.</div> <bR> <div> After World War II ended in 1945, many German rocket engineers went to work for the U. S. government to help develop military missiles. The U. S. 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).</div> <bR> <div> 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 manned lunar landing vehicles, space suits, and orbital rendezvous. A U. S. group, the American Rocket Society, concentrated on missile engineering. In 1950, a new International Astronautical Federation began to hold annual conferences.</div> <bR> <div> The First Artificial Satellites</div> <div> In 1955, both the United States and the Soviet Union announced plans to launch artificial satellites with scientific instruments on board. 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. The Soviets provided detailed descriptions of the radio equipment to be included on their satellite. But the Soviet rocket program had been kept secret until that time. As a result, many people in other countries did not believe that the Soviets had the advanced technology required for space exploration.</div> <bR> <div> Then, on Oct. 4, 1957, the Soviets stunned the world by succeeding in their promise--and by doing so ahead of the United States. 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. Sputnik means traveling companion in Russian. The R-7 booster hurled the 184-pound (83-kilogram) satellite and its main rocket stage into orbit around the earth. Radio listeners worldwide picked up Sputnik's characteristic "beep-beep" signal.</div> <bR> <div> The Space Race Begins</div> <div> The Western world reacted to the launch of Sputnik with surprise, fear, and respect. Soviet Premier Nikita S. Khrushchev ordered massive funding of follow-up projects that would continue to amaze and dazzle the world. In the United States, leaders vowed to do whatever was needed to catch up. Thus the "space race" began.</div> <bR> <div> More Soviet successes followed</div> <div> A month after Sputnik, another satellite, Sputnik 2, carried a dog named Laika into space. The flight proved that animals could survive the unknown effects of microgravity. In 1959, Luna 2 became the first probe to hit the moon. Later that year, Luna 3 photographed the far side of the moon, which cannot be seen from the earth.</div> <bR> <div> 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 U. S. 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. The Soviet Union's rockets gave it an early lead in the space race. Because bigger rockets would be needed for manned lunar flight, both the United States and the Soviet Union began major programs of rocket design, construction, and testing.</div> <bR> <div> Organizing and Managing Space Activities</div> <div> A key to the ultimate success of U. S. space programs was centralized planning. In 1958, a civilian space agency called the National Aeronautics and Space Administration (NASA) was established. NASA absorbed various aviation researchers and military space laboratories. The formation of NASA helped forge agreement among competing interests, including military branches, universities, the aerospace industry, and politicians.</div> <bR> <div> Soviet space activities, on the other hand, were coordinated by special executive commissions. 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.</div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B>SPACE EXPLORATION/Space Probes</B></div> <bR> <div> A space probe is an unmanned device sent to explore space. A probe may operate far out in space, or it may orbit or land on a planet or a moon. It may make a one-way journey, or it may bring samples and data back to the earth. Most probes transmit data from space by radio in a process called telemetry.</div> <bR> <div> Lunar and planetary probes that land on their targets may be classified according to their landing method. Impact vehicles make no attempt to slow down as they approach the target. Hard-landers have cushioned instrument packages that can survive the impact of a hard landing. Soft-landers touch down gently. Penetrators ram deeply into the surface of a target.</div> <bR> <div> How a Space Probe Carries Out Its Mission</div> <div> Probes explore space in a number of ways. A probe makes observations of temperature, radiation, and objects in space. A probe also observes nearby objects. In addition, a space probe exposes material from the earth to the conditions of space so that scientists can observe the effects. A probe may also perform experiments on its surroundings, such as releasing chemicals or digging into surface dirt. Finally, a probe's motion enables controllers on the earth to determine conditions in space. Changes in course and speed can provide information about atmospheric density and gravity fields.</div> <bR> <div> Early Unmanned Explorations</div> <div> Beginning in the 1940's, devices called sounding rockets carried scientific instruments into the upper atmosphere and into nearby space. They discovered many new phenomena and took the first photographs of the earth from space.</div> <bR> <div> The 1957 launch of Sputnik 1 marked the beginning of the space age. Sputnik 1 carried only a few instruments and transmitters, but it paved the way for the sophisticated probes that would later explore space.</div> <bR> <div> Many early satellites probed uncharted regions of space. 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 the earth and the moon. United States Pegasus satellites recorded the impacts of micrometeorites. During the early 1970's, Soviet Prognoz satellites studied the sun.</div> <bR> <div> Lunar Probes</div> <div> In 1958, both the United States and the Soviet Union began to launch probes toward the moon. The first probe to come close to the moon was Luna 1, launched by the Soviet Union on Jan. 2, 1959. It passed within about 3,700 miles (6,000 kilometers) of the moon and went into orbit around the sun. The United States conducted its own lunar fly-by two months later with the probe Pioneer 4. The Soviet Luna 2 probe, launched on Sept. 12, 1959, was the first probe to hit the moon. One month later, Luna 3 circled behind the moon and photographed its hidden far side.</div> <bR> <div> The Soviet Union began to test lunar hard-landers in 1963. After many failures, they succeeded with Luna 9, launched in January 1966. The U. S. Surveyor program made a series of successful soft landings beginning in 1966. Between 1970 and 1972, three Soviet probes returned lunar soil samples to the earth in small capsules. Two of them sent remote-controlled jeeps called Lunokhods, which traveled across the lunar surface.</div> <bR> <div> Beginning in 1966, the United States sent five probes called Lunar Orbiters into orbit to photograph the moon's surface. 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. These areas of tightly packed matter were called mascons, which stood for mass concentrations. If the mascons had not been discovered, they might have interfered with the Apollo missions that sent astronauts to the moon.</div> <bR> <div> Solar Probes</div> <div> Beginning in 1965, the United States launched a series of small Pioneer probes into orbit around the sun to study solar radiation. Many of these probes were still operating more than 20 years after launch. In 1974 and 1976, the United States launched two German-built Helios probes, which passed inside the orbit of Mercury to measure solar radiation. The Ulysses space probe was launched in 1990 by the United States and the European Space Agency, an association of 14 European nations. The probe was expected to observe the sun's polar regions in 1994 and 1995.</div> <bR> <div> Probes to Mars</div> <div> 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.</div> <bR> <div> In 1971, the Soviet probe Mars 3 dropped a capsule that made the first soft landing on Mars, but it failed to return usable data. That same year, the U. S. 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.</div> <bR> <div> Two U. S. 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.</div> <bR> <div> In 1992, the United States launched the probe Mars Observer. In 1993, NASA lost contact with the probe three days before it was scheduled to go into orbit around Mars. Communication was never restored, and the probe was presumed lost.</div> <bR> <div> Probes to Venus</div> <div> 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 U. S. 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.</div> <bR> <div> 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 Venus, 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.</div> <bR> <div> Probes that orbited Venus generated rough maps of the planet's surface by bouncing radio waves off the ground. Pioneer Venus 1 used radar to map most of the planet's 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 northern hemisphere of Venus to a resolution of 0. 9 mile (1. 5 kilometers). The U. S. probe Magellan reached Venus in 1990 and mapped almost the entire surface to a resolution of about 330 feet (100 meters).</div> <bR> <div> Probes to Jupiter and Beyond</div> <div> Probes to the outer planets--Jupiter, Saturn, Uranus, Neptune, and Pluto--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.</div> <bR> <div> The United States launched its first probes to Jupiter, Pioneer 10 and Pioneer 11, 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. These probes continue to 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 huge amounts 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 formations of ice and rock.</div> <bR> <div> 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. Galileo was expected to reach Jupiter in 1995. By 1989, the only planet not yet visited was Pluto.</div> <bR> <div> Probes to Comets</div> <div> Two Soviet probes flew past Venus and dropped instruments into the planet's atmosphere, then intercepted Halley's Comet as it passed by the sun in 1986. In 1985, the European Space Agency launched its first interplanetary probe. The probe, called Giotto, passed closer to the comet's nucleus than any other probe. Giotto returned dramatic close-up images of the comet. Japan also sent two small probes. After several years of inactivity, Giotto was reactivated to fly past the comet Grigg-Skjellerup in July 1992.</div> <bR> <div> The United States did not send a probe to Halley's Comet because of budget limitations. However, NASA scientists realized that a small probe already in space could be diverted to explore another comet. The International Sun-Earth Explorer 3 satellite had spent several years in space between the 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.</div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B>SPACE EXPLORATION/Human Beings Enter Space</B></div> <bR> <div> 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.</div> <bR> <div> 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.</div> <bR> <div> <B>Vostok and Mercury: The First Human Beings in Space</B></div> <bR> <div> 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.</div> <bR> <div> The U. S. 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.</div> <bR> <div> While U. S. plans proceeded in the glare of publicity, Soviet developments took place in great secrecy. Both nations made unmanned 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.</div> <bR> <div> The first fatality in a manned 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.</div> <bR> <div> 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 the earth once and returned safely. An autopilot device controlled the spacecraft during the entire flight. A 25-hour, 17-orbit flight by cosmonaut Gherman Titov aboard Vostok 2 followed in August of that year.</div> <bR> <div> The Mercury program made its first manned 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 the earth.</div> <bR> <div> 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.</div> <bR> <div> On Feb. 20, 1962, John H. Glenn, Jr. , became the first American to orbit the earth. Glenn completed three orbits in less than five hours. He pointed his capsule in different directions, tested its various systems, and observed the earth.</div> <bR> <div> 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 L. Gordon Cooper aboard. The mission lasted 1 1/2 days.</div> <bR> <div> 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.</div> <bR> <div> <B>Voskhod and Gemini: The First Multiperson Space Flights</B></div> <bR> <div> 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 U. S. efforts was so intense that Soviet engineers sacrificed certain safety features, such as ejection seats, to enlarge the capsule.</div> <bR> <div> 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.</div> <bR> <div> 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 autopilot 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.</div> <bR> <div> The first manned 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.</div> <bR> <div> Gemini 6 was originally intended to link up with an Agena rocket sent into space a few hours earlier. After the unmanned 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 the earth together for several hours before separating.</div> <bR> <div> 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.</div> <bR> <div> 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 manned lunar flight.</div> <bR> <div> <B>Apollo: Mission to the Moon</B></div> <bR> <div> 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 the earth" before the 1960's ended. This goal was intended to show the superiority of U. S. science, engineering, management, and political leadership.</div> <bR> <div> NASA considered several proposals for flying a manned lunar mission. The agency selected a plan in which a vehicle called the command/service module (CSM) would orbit the moon but would not land on it. Instead, a special spacecraft called a lunar module (LM) would take two astronauts to the moon's surface. When the astronauts had completed their activities on the lunar surface, the LM would blast off from the moon and return the astronauts to the orbiting CSM. This procedure was called lunar orbit rendezvous, and it seemed complex. However, a tremendous amount of rocket fuel would be saved by not having to land the heavy CSM on the moon and launch it into space again. The entire mission would require only one Saturn 5 booster. In 1962, lunar orbit rendezvous became the official U. S. strategy. When the Soviet government secretly decided to try to beat the United States to the moon, it chose the same strategy.</div> <bR> <div> Making Ready</div> <div> Tragedy struck during preparations for the first manned Apollo flight, a trial run in low earth orbit. On Jan. 27, 1967, a flash fire inside the sealed cabin killed astronauts Grissom, White, and Roger B. Chaffee during a ground test. An electrical short circuit probably started the fire, and the pure oxygen atmosphere caused it to burn fiercely.</div> <bR> <div> A few months later, the Soviet space program also suffered a disaster. The Soyuz (Union) 1 capsule was launched with a single cosmonaut. It was supposed to link up with a second manned spaceship, but Soyuz 1 developed problems and the second ship was never launched. Controllers ordered Soyuz 1 to return to the earth. But a parachute failure caused the capsule to crash to the ground, killing the pilot, Komarov.</div> <bR> <div> While the Apollo CSM and the Soyuz capsule were being redesigned, other tests took place as planned. An unmanned U. S. launch of the first Saturn 5 booster on Nov. 9, 1967, was a complete success. Early in 1968, an unmanned LM was sent into orbit, where it test-fired its engines.</div> <bR> <div> Orbiting the Moon</div> <div> By late 1968, the United States had redesigned the Apollo CSM, and engineers had overcome technical problems with the Saturn 5 rockets. But the lunar module remained far behind schedule.</div> <bR> <div> NASA officials knew about Soviet preparations for a manned lunar fly-by. Because the CSM and the Saturn booster were ready, NASA boldly decided to fly a manned mission to orbit the moon, without the LM. The orbital mission would test navigation and communication around the moon. It would also provide good training for both astronauts and mission controllers. In addition, such a mission would prevent the Soviets from possibly upstaging the later lunar landing with a simpler manned lunar fly-by mission. </div> <bR> <div> Apollo 8, the first manned expedition to the moon, blasted off from the Kennedy Space Center in Cape Canaveral, Fla. , 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 an on-board rocket to change course into a circular orbit around the moon. They made observations and took photographs, then headed back to the earth. Apollo 8 landed safely in the Pacific Ocean near Hawaii on December 27.</div> <bR> <div> Two additional test flights were made to ensure the safety and effectiveness of the lunar module. The LM was tested in low orbit around the earth by the Apollo 9 astronauts and in lunar orbit by the Apollo 10 crew.</div> <bR> <div> Landing on the Moon</div> <div> 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, Edwin E. Aldrin, Jr. , and Michael Collins.</div> <bR> <div> 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--fast enough to escape the pull of the earth's gravity. 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.</div> <bR> <div> For three days, Apollo 11 drifted toward the moon. The earth's gravity constantly tugged at the spacecraft, slowing it down. But as the spaceship traveled farther from the earth, the pull of the earth's gravity became weaker. By the time the ship was 215,000 miles (346,000 kilometers) from the earth, its speed had dropped to 2,000 miles (3,200 kilometers) per hour. But then the moon's gravity began to pull the spaceship toward it, and the craft picked up speed again.</div> <bR> <div> 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 was needed to change course into a low lunar orbit.</div> <bR> <div> Once in lunar orbit, the crew checked out the lunar module. The lunar module had four legs that were attached to a descent stage, which had the engine and fuel tanks for landing. A smaller ascent stage on top had a tiny crew cabin and a small engine to launch the astronauts back into space. Lockers at the base of the LM held exploratory and scientific equipment.</div> <bR> <div> Armstrong and Aldrin separated the LM from the CSM. They fired the LM's descent stage and began the landing maneuver. They had to use the LM's rockets for braking because there was no atmosphere to help slow the descent. Collins remained in the CSM in lunar orbit.</div> <bR> <div> To help NASA mission controllers recognize voice signals from the command/service module and from the lunar module, the astronauts used different call signs for the two vehicles. They called the CSM Columbia and the LM Eagle.</div> <bR> <div> 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 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, LM pilot Armstrong radioed back his famous announcement: "Houston, Tranquility Base here. The Eagle has landed. "</div> <bR> <div> Exploring the Moon</div> <div> 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.</div> <bR> <div> 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 backwards 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.</div> <bR> <div> A television camera mounted on the side of the LM sent blurred images of the astronauts back to the 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.</div> <bR> <div> 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. Meanwhile, from the orbiting CSM, Collins conducted various scientific observations and took photographs.</div> <bR> <div> Returning to the Earth</div> <div> 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 the earth.</div> <bR> <div> The trip home resembled the trip to the moon</div> <div> The craft splashed down in the Pacific Ocean on July 24. NASA immediately put the lunar material, the astronauts, and all equipment that was exposed to the lunar environment into isolation. The isolation, which lasted about 17 days for the astronauts, was designed to determine whether any germs or other harmful material had been brought from the moon. Nothing harmful was found.</div> <bR> <div> Other Moon Landings</div> <div> Apollo astronauts made a total of six landings on the moon 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 rocket 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.</div> <bR> <div> 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.</div> <bR> <div> The Apollo 12 lunar module made a precision landing on Nov. 19, 1969. Astronauts Charles (Pete) Conrad, Jr. , and Alan L. Bean were able to walk to a landed space probe, Surveyor 3, and retrieve samples for study. The Apollo 13 mission in April 1970 was cut short after an explosion severely damaged the spacecraft's life-support and electrical systems. The crew, commanded by Lovell, had to use the LM's life-support systems to survive until they could get back to the earth. Apollo 14, with astronauts Alan B. Shepard, Jr. , and Edgar D. Mitchell, landed near the Fra Mauro Crater on Feb. 5, 1971.</div> <bR> <div> Apollo 15 landed near the Apennine Mountains of the moon on July 30, 1971. 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 were the astronauts on this mission.</div> <bR> <div> The Apollo expeditions achieved the goal of demonstrating U. S. technological superiority, and the race to the moon ended with a clear-cut U. S. 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 U. S. economy. Most importantly, the Apollo missions stirred people's imagination and raised their awareness of the earth's place in the universe.</div> <bR> <div> <B>Soviet Attempts to Reach the Moon</B></div> <bR> <div> 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.</div> <bR> <div> Soviet plans for manned 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.</div> <bR> <div> Manned 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 unmanned test flights under the cover name Zond. Three pairs of Soviet cosmonauts trained for a lunar mission.</div> <bR> <div> The Soviet moon ships had serious problems. Many of the boosters for the L-1 lunar fly-by blew up. In addition, the unmanned 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.</div> <bR> <div> <B>The Apollo-Soyuz Test Project</B></div> <bR> <div> In 1972, the United States and the Soviet Union agreed to participate in the first international manned space mission. They planned to perform an orbital rendezvous between a Soviet Soyuz capsule and a U. S. 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.</div> <bR> <div> <B>SPACE EXPLORATION/Space Stations</B></div> <bR> <div> A space station is a place where people can live and work in space for long periods. It orbits the 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 manned spacecraft, so they provide more comforts. Manned spacecraft may transport people between the earth and the space station. Unmanned spacecraft may supply the station with food, water, equipment, and mail.</div> <bR> <div> Small space stations can be built on the 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.</div> <bR> <div> 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.</div> <bR> <div> The main tasks of a space station crew involve scientific research. For example, they might analyze the effects of microgravity on various materials, investigate the earth's surface, or study the stars and planets.</div> <bR> <div> 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.</div> <bR> <div> <B>Salyut and Skylab</B></div> <bR> <div> In the 1960's, missions to the moon dominated the U. S. 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 manned spacecraft originally built for lunar flight--the U. S. Apollo and the Soviet Soyuz--were modified to transport people to the space stations.</div> <bR> <div> Salyut</div> <div> 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.</div> <bR> <div> In 1974, Salyut 3 hosted a 15-day mission to photograph the earth. Salyut 4 received two missions in 1975. The second lasted 63 days. In 1976, Salyut 5 repeated the Salyut 3 photography mission.</div> <bR> <div> 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, unmanned 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.</div> <bR> <div> Skylab</div> <div> The first U. S. 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.</div> <bR> <div> 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.</div> <bR> <div> Two more crews carried out Skylab missions. These astronauts continued to operate the station while conducting medical experiments, photographing the earth, and observing the sun. The second mission lasted 59 days, and the third ran for 84 days.</div> <bR> <div> 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.</div> <bR> <div> <B>Mir</B></div> <bR> <div> 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.</div> <bR> <div> After the launch of Mir, the Soviet Union sent three laboratory modules into orbit, where they docked with the core module. Cosmonaut crews spent up to a year 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 when the space station was unoccupied.</div> <bR> <div> <B>Alpha</B></div> <bR> <div> 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, then called Freedom, to reduce the cost and amount of time it would take to build. The United States, Canada, Japan, Russia, and the European Space Agency would become partners in a program to build the redesigned space station. The station, called Alpha, would be built from several pressurized modules and solar power panels.</div> <bR> <div> The United States would provide much of the structural framework of the station, including the main truss (support) structure and many of the solar panels. The United States would also provide a laboratory module for scientific work and a habitation module to serve as living quarters for a six-person crew. Russia would provide three research modules and a service module for various housekeeping and life-support functions. Russia also planned to provide solar panels for the station. The National Space Development Agency of Japan and the European Space Agency planned to build laboratory modules for the station. Canada would provide a robot arm for the station, and Italy planned to provide a pressurized module.</div> <bR> <div> The Alpha space station would serve as a major international laboratory for scientific research. More than 30 flights of the U. S. space shuttle and Russian launch vehicles would be necessary to construct the station in space.</div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B>SPACE EXPLORATION/Space Shuttles</B></div> <bR> <div> 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.</div> <bR> <div> NASA began to develop a reusable space shuttle while the Apollo program was still underway. In 1972, U. S. 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.</div> <bR> <div> 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.</div> <bR> <div> 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.</div> <bR> <div> 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 the earth's atmosphere.</div> <bR> <div> <B>The Shuttle Era Begins</B></div> <bR> <div> 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. On the first free test flight, astronauts Fred W. Haise, Jr. , and Gordon Fullerton tested the vehicle's landing capabilities. Several more test flights followed.</div> <bR> <div> The first space shuttle 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.</div> <bR> <div> 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).</div> <bR> <div> When NASA recruited astronauts for the space shuttle program in 1978, several women engineers and scientists were selected to train as mission specialists. On June 18, 1983, Sally K. Ride became the first U. S. woman in space, on the space shuttle Challenger. Guion S. Bluford, Jr. , became the first black American in space on Aug. 30, 1983. Marc Garneau became the first Canadian in space on Oct. 5, 1984. On Sept. 12, 1992, Mae C. Jemison became the first black woman in space.</div> <bR> <div> 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 U. S. Congress.</div> <bR> <div> 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.</div> <bR> <div> <B>Types of Shuttle Missions</B></div> <bR> <div> Space shuttles carry artificial satellites, space probes, and other heavy loads into orbit around the 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.</div> <bR> <div> Commercial Satellite Launches</div> <div> 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.</div> <bR> <div> Military Missions</div> <div> 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.</div> <bR> <div> Repair Missions</div> <div> 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.</div> <bR> <div> Spacelab Missions</div> <div> Spacelab is a facility that enables 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. Spacelab consists of a manned space laboratory and several separate platforms called pallets. The pressurized laboratory is connected to the crew compartment by a tunnel. It has facilities for scientists to conduct experiments in manufacturing, medicine, the production of biological materials, and other areas. The pallets carry large scientific instruments that are used to conduct experiments in astronomy and other fields. Scientists operate the instruments from the laboratory, from the shuttle's orbiter, or from the ground. Spacelab facilities are shared by ESA and the United States.</div> <bR> <div> The first Spacelab mission was launched on Nov. 28, 1983, in the space shuttle Columbia. Since then, many shuttle flights have carried the Spacelab. Each Spacelab mission focused on research in a particular area of science or technology, such as astronomy, life sciences, and microgravity.</div> <bR> <div> <B>The Challenger Disaster</B></div> <bR> <div> 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.</div> <bR> <div> 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.</div> <bR> <div> 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.</div> <bR> <div> 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 pieces that held the booster to the side of the external tank. The booster tore loose and ruptured the tank. The propellants from the tank mixed and formed a giant fireball as structural failures tore the vehicle apart.</div> <bR> <div> 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.</div> <bR> <div> 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.</div> <bR> <div> <B>Back Into Space</B></div> <bR> <div> The space shuttle resumed flying on Sept. 29, 1988, with the launch of the redesigned space 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. Shuttle astronauts launched a number of unmanned 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. 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.</div> <bR> <div> 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 autopilot was also improved.</div> <bR> <div> <B>The Soviet Space Shuttle</B></div> <bR> <div> As NASA struggled to resume shuttle flights, the Soviet Union readied its own space shuttle. Its shuttle program took place in great secrecy. The Soviet shuttle, Buran (Snowstorm), resembled the U. S. shuttle. But although Soviet engineers may have started with the U. S. model, they made many modifications. For example, they moved the nose landing gear to a safer position, and they installed a braking parachute. Their maneuvering rockets used a different kind of fuel. The Soviet shuttle used expendable boosters and had no main engines to recover.</div> <bR> <div> A heavy booster called Energia, which made its first flight on May 15, 1987, was designed to carry the Soviet shuttle and other space projects into orbit. On Nov. 15, 1988, a second Energia rocket carried Buran into orbit without a crew. An autopilot controlled the two-orbit flight. Buran landed on a runway at the Baykonur Cosmodrome (now called the Tyuratam Cosmodrome) in Kazakhstan, then part of the Soviet Union. The first Buran had no crew support equipment. Cosmonauts trained for manned missions, and a second shuttle was built. But beginning in 1989, shortages of funds caused long delays in the further development of the Buran program. In 1993, work on the shuttle program ended.</div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B>S</B><B>PACE EXPLORATION/Other Nations in Space</B></div> <bR> <div> A number of nations have developed rocket and space programs from the 1960's to the 1980's. These programs were on a smaller scale than the U. S. and Soviet programs. Nevertheless, they have made important contributions to the exploration of space.</div> <bR> <div> European Nations</div> <div> Several European nations built boosters to launch small scientific research satellites. In 1965, France became the first European nation to launch a satellite. Great Britain sent another satellite into orbit in 1971.</div> <bR> <div> In 1975, the European Space Agency (ESA) was organized. Its 14 Western European member nations combine their financial and scientific resources in the development of spacecraft, instruments, and experiments. ESA supervised the construction of Spacelab, launched the space probe Giotto toward Halley's Comet, and built the Ulysses solar probe. ESA also developed the Ariane booster rocket to launch communications satellites for paying customers. ESA spacecraft lift off from Kourou in French Guiana, on the northern coast of South America.</div> <bR> <div> Besides its activities as a member of 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.</div> <bR> <div> 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 space boosters. The H-1 rocket, a medium-sized booster with liquid hydrogen fuel, also became operational. In 1990, Japan launched a lunar probe.</div> <bR> <div> 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 planned international space station Alpha.</div> <bR> <div> China</div> <div> 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.</div> <bR> <div> India first launched a satellite into orbit in July 1980. The Indian Space Research Organization builds boosters. India launches rockets from the island of Sriharikota, off its eastern coast.</div> <bR> <div> Canada has an active space research program and a communications satellite program. It took part in the U. S. space shuttle program by designing and building the shuttle's robot arm. Canada is building a larger robot arm for the space station Alpha.</div> <bR> <div> Other Nations</div> <div> Israel sent its first satellite into orbit in 1988. Australia has launched modified U. S. rockets from Woomera, in central Australia. Italy has launched U. S. 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.</div> <bR> <DIV ALIGN="LEFT"></DIV> <div> <B>SPACE EXPLORATION/Plans for the Future</B></div> <bR> <div> Space exploration plans call for expanding activities in space. Preparations will also be made for the establishment of a base on the moon and for expeditions to Mars. Many of these projects may become international ventures.</div> <bR> <div> Developing More Powerful Spacecraft</div> <div> Several nations, including Germany and the United States, are working to develop a vehicle called an aerospace plane. Unlike the shuttle, which requires drop-away boosters to reach space, the aerospace plane would propel itself both in space and in an atmosphere. It might take off from an airport like a plane, rocket into orbit without dropping any stages or tanks, and land at an airport. The aerospace plane could also be launched from an aircraft carrier.</div> <bR> <div> Engineers will also test new technologies for the design and construction of more powerful spacecraft. These technologies include advanced propulsion, such as high-efficiency engines. Nuclear rockets could get more than twice the thrust of ordinary rockets from the same amount of propellant, enabling spacecraft to travel farther on less fuel. Some scientists speculate that many years from now, spacecraft may run on reactions between matter and some form of antimatter--that is, matter composed of atomic particles with their electric charges reversed.</div> <bR> <div> Unmanned probes will continue to explore distant planets and interstellar space. Advanced life-support systems for people on long space missions may include both biological systems, such as greenhouses, and chemical processors for recycling wastes.</div> <bR> <div> Expanding Space Activities</div> <div> Manufacturing products in space has long been a goal of space planners. New industrial processes may create products in space that are purer, cheaper, or more powerful than those manufactured on the earth. Such items could include semiconductors, drugs, or alloys of certain metals.</div> <bR> <div> Some space theorists suggest that enormous electric power satellites in space could beam clean energy to the earth. Even a simple, huge mirror could reflect sunlight onto the ground and thus generate useful illumination and even power.</div> <bR> <div> Scientists are experimenting with a promising new space technology involving the use of strong, thin cables called space tethers. A tether up to 78 miles (125 kilometers) long could connect two orbiting spacecraft. The motions of the two spacecraft would generate useful forces. Swinging one of the spacecraft could increase these forces. A tether coated with a substance that conducts electricity might generate energy as it passes through the earth's magnetic field. The tether and the magnetic field act like a generator, producing electricity through the process called electromagnetic induction. This energy could provide power for a space station. Tethered spacecraft might also transport payloads between a space vehicle and a space station.</div> <bR> <div> Since the early 1980's, the United States Department of Defense has worked to develop a space-based system of defense against nuclear missiles. This project is called the Strategic Defense Initiative, also known as SDI or "Star Wars. "SDI would use weapons mounted on artificial satellites to destroy attacking missiles in flight. Many of the program's experiments involve improvements in space propulsion and power.</div> <bR> <div> The most potentially rewarding space activity might be the detection of asteroids that threaten to collide with the earth. A spacecraft armed with explosives could be launched and exploded near such asteroids to deflect them away from the earth.</div> <bR> <div> Advanced shielding technologies could be developed to enable probes--and later, people--to venture deep into radiation belts or close to the sun. Plans also call for continued efforts to identify other intelligent life in the universe. Other civilizations may be sending signals that human beings could recognize. The failure to detect such signals after years of searching would in itself be important.</div> <bR> <div> Establishing a Base on the Moon. NASA's official space exploration program calls for setting up a base on the moon in the early 2000's. Many space planners believe that the establishment of a moon base is an important step toward the creation of a base on Mars. Scientists may also study the possibility of obtaining valuable resources on the moon, such as oxygen or metals.</div> <bR> <div> Sending People to Mars may become the next great adventure of space exploration. Such a mission could take place in the early 2000's. The round trip between Mars and the earth would take about two years, so the spaceship must be large enough to hold the necessary fuel, food, and other supplies and to provide adequate living space for the crew.</div> <bR> <div> Because both the earth and Mars constantly orbit the sun, their relative positions change tremendously. The planets line up to provide the simplest, cheapest flight path for only a few weeks every 26 months. This period during which a mission must begin is called the launch window.</div> <bR> <div> Mars will be easier to approach than the moon because it has an atmosphere. A spaceship can skim the upper atmosphere or fire rockets to slow down and enter an orbit around Mars. From orbit, the astronauts can explore the planet's two moons, Phobos and Deimos. These moons may be captured asteroids, so they are of great interest to scientists. The first manned expeditions might establish a base on Phobos. Some scientists believe that Phobos may contain minerals or ice, which could be converted into rocket fuel.</div> <bR> <div> The following is one explanation of how astronauts might land on Mars, conduct their experiments, and return to the earth. To land on Mars, a small landing craft would leave the main spaceship as it orbited the planet. Rockets would propel the landing vehicle toward the atmosphere, which would provide most of the braking. Rockets and a large parachute would help direct the lander to a safe site on the surface.</div> <bR> <div> A Mars mission would have many scientific goals. For example, study of the Martian climate might help scientists predict climatic changes on the earth. Astronauts would take deep drill samples of the Martian soil and polar caps for this study. The geology of Mars would provide information about the history of the solar system. And the search for life, or for fossilized traces of extinct life forms, would continue.</div> <bR> <div> Liftoff from Mars would work much like the blastoffs from the moon. The Martian lander would link up in space with the main spaceship for the return journey to the earth. Soon after the first missions to Mars, permanent bases on Phobos and on Mars would probably be established.</div> <bR> <div> The earth's climate resembles the climate of Mars more closely than that of any other planet. If Mars had more air and were a little warmer, it would be much like the earth. In future centuries, engineers may be able to warm the surface of Mars with huge solar mirrors. They may import material from the asteroid belt to thicken the air. Over time, the climate on Mars could be so changed that human beings could live there without life-support systems. This process is called terraforming.</div> <bR> <div> Some visionaries imagine a time when large numbers of people would live and work in space. They foresee individuals being born, living, and dying without ever setting foot on the earth. Orbiting space colonies or modified planets, they believe, could provide homes for millions of people. Sometime in the distant future, there could be more human beings living in space than on the earth.</div> <bR> </td> </tr></table></body>