(2) 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. We do not know the boundaries of the universe or what advances can come out of these explorations so we must thrust our emotions into the unknown and have an open mind to the possibilities.

So while the average person is wondering what space has to offer the person do not realize the many missions that have already went on in this field. The exploration of bodies in the solar system began within a few years of the first satellites. In 1926 American scientist Robert H. Goddard launched the world's first liquid-propellant rocket. Then both U.S. and Soviet space engineers set their sights on the Moon. Early Soviet launches in 1958 all failed and were never announced.

Several U.S. launches also failed, although two of them (Pioneers 1 and 3) reached nearly 100,000 km into space before falling back to Earth. In 1958 a great leap occurred when The National Aeronautics and Space Administration (NASA) was formed. This program is what runs all the space ideas and puts them into action The first probe to escape Earth's gravity was the Soviet LUNA 1, launch on (3) Jan. 2, 1959, which passed the Moon and continued into interplanetary space. The U.S. probe Pioneer 4, launched two months later, followed the same path.

Later Soviet probes either hit the Moon or passed it and took photographs of the hidden far side, relaying them back to Earth. The space age began on Oct. 4, 1957. On that day, the Soviet Union launched 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 1.

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. 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 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. The early years of the space age, success in space became a measure of a country's cience, engineering, and national defense. The United States and the Soviet Union (4) 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. 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 days in orbit. In the mid-1960's three NASA programs pursued the lunar objective. Ranger probes crashed into the Moon's surface but succeeded in sending high-resolution photographs prior to impact. SURVEYOR probes soft-landed on the Moon and analyzed its surface, while Lunar orbiters probes circled the Moon and sent back pictures both of potential landing sites for astronauts and of areas of general scientific interest.

Soviet efforts proceeded along similar lines and achieved limited successes shortly before their U.S. equivalents (Luna 9 made the first survivable hard landing on the Moon in 1966, and Luna 10 became the first probe to enter lunar orbit a few months later). The Soviets later operated a series of heavy automatic probes that retrieved small amounts of lunar soil, deployed a wheeled rover called the Lunokhod, and made lunar-orbit surveys. The USSR also aimed three Soviet rockets toward Mars in 1960, but all failed; the last caused great loss of life when it exploded during a launchpad checkout. Other shots in the Soviet series also failed, including later landing attempts. The first successful Mars probe was the U.S. MARINER 4, in 1964. Two more fly-by missions and an orbital photographic flight followed before the sophisticated landings of VIKING spacecraft in 1976. the first spacecraft to reach the planet successfully (5) was NASA's Mariner 2, in 1962.

Later Soviet VENETA atmospheric probes eventually returned some basic data, and Mariner 5 provided sophisticated measurements during a fly-by. While a Soviet probe survived briefly on the surface of Venus in 1971, with more advanced ladders following in 1975 and later. In 1977 (Aug. 20) The United States launched the probe Voyager 2, which flew past and photographed Jupiter in 1979, Saturn in 1981, Uranus in 1986, and Neptune in 1989. 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 then redesigned, and flights resumed in 1988. By mid-January 1986, NASA had successfully completed 55 space missions -- 24 aboard the space shuttles. On July 2 1985 The European Space Agency launched the probe Giotto, which passed Halley's Comet on March 14, 1986, photographed the comet's nucleus, and sent back data. The USSR sent two probes to reach the Martian moon Phobos in 1989, but one went out of control shortly after launch, and contact was lost with the other soon after it began returning data from Mars (6) orbit. Soviet probes toward VENUS also failed in early attempts.

In 1987 and 1988, two Soviet cosmonauts spent a record 366 consecutive days in orbit Jan. 28 1986, the U.S. space shuttle Challenger was destroyed in an accident shortly after launch, killing all seven crew members. 1989 (Oct. 18) The United States launched the probe Galileo, which reached Jupiter in 1995. Galileo was far more sophisticated than earlier planetary probes. In 1990 (Aug. 10) The U.S. space probe Magellan began to orbit Venus and return radar images of the planet's surface. In 1994, Ulysses became the first probe to observe the sun from an orbit over the sun's poles. March 22, 1995 Cosmonaut Valery Pol yakov completed a record 438 days in space aboard the Russian space station Mir.

A more recent launch was on July 4, 1997 when the Pathfinder and Sojourner sent live video to scientists about Mars. (7) Many break through's have occurred because of space travel, but there are also new techniques concerning the suits, medicine, food, or even the way astronauts go about their day. One problem is overcoming gravity it is the biggest problem for a space mission. A spacecraft must be launched at a particular velocity (speed and direction). Gravity gives everything on the earth its weight and accelerates free-falling objects downward. At the surface of the earth, acceleration due to gravity, called g, is about 32 feet (10 meters) per second each second.

A powerful rocket called a launch vehicle or booster 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, this stage's thrust must exceed the weight of the entire launch vehicle and the spacecraft. The booster generates thrust by burning fuel and then expelling gases. he minimum velocity required to overcome gravity and stay in orbit 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 the speed needed for a spacecraft to maintain orbital velocity and thus stay in orbit is about 5 miles per second. 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. At launch time, the rocket's first-stage engines ignite until their combined thrust exceeds (8) 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. 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. To reach a higher altitude, a spacecraft must make another rocket firing to increase its speed. When the spacecraft reaches a speed about 40 percent faster than orbital velocity, it achieves escape velocity, the speed necessary to break free of the earth's gravity.

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.

But in space, astronauts and (9) 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. The basic needs of astronauts in space must also be met. These needs include breathing, eating and drinking, elimination of body wastes, and sleeping. 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. 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. 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.

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. (10) 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. Once a space vehicle reaches its orbit, the crew members begin to carry out the goals of their mission. They perform a variety of tasks both inside and outside the spacecraft.

Navigation, guidance, and control. Astronauts use computerized navigation systems and make sightings on stars to determine their position and direction. On 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. Activating equipment.

Much of the equipment on a space vehicle is turned off or tied down during launch. Once in space, the astronauts must set up and turn on the equipment. At the end of the mission, they must secure it for landing. Conducting scientific observations and research.

Astronauts use special instruments to observe the earth, the stars, and the sun. They also experiment with the effects of microgravity on various materials, plants, animals, and themselves. 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 (11) reaches the correct position beside the target, it docks (joins) with the target by connecting special equipment. Such a meeting in space is called a rendezvous. A space shuttle can also use its robot arm to make contact with targets.

Maintaining and repairing equipment, the thousands of pieces of equipment on a modern space vehicle are extremely reliable, but some of them still break down. Accidents damage some equipment. Other units must be replaced when they get old. Astronauts must find out what has gone wrong, locate the failed unit, and repair or replace it. Assembling space stations. Astronauts may serve as construction workers in space, assembling a space station from components carried up in the shuttle.

On existing space stations, crews often must add new sections or set up new antennas and solar panels. Power and air connectors must be hooked up inside and outside the station. Leaving the spacecraft. 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-door ed chamber called an air lock. They then release the air from the air lock, open the outer hatch, and leave the spacecraft. When they return, they close the outer door and let air into the air lock.

Then they open the inner door into the rest of the spacecraft, where they remove their space suits. A space suit can keep an astronaut alive for six to eight hours. The suit is made from many layers of flexible, airtight materials, such as nylon and Teflon. It provides protection against heat, cold, and space particles. Tight mechanical seals connect the pieces of the space suit. (12) 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.