Category FLIGHT and M ОТІOIM

Late in 1961, NASA chose Glenn to pilot the first American orbital flight. Getting that flight off the ground became a chal­lenge, however. The launch was delayed by problems with the booster rocket and by bad weather. There was even a brief scare over Glenn’s health when he was exposed to children who had the mumps, a disease Glenn had never had. Luckily, he did not become infected.

After ten delays, Glenn finally entered his Friendship 7 space capsule on February 20, 1962. At 10 A. M., the Atlas rocket began to fire and lifted the spacecraft into the air. “We’re under way,” said Glenn.

The flight went smoothly at first. A problem did develop at one point, and Glenn turned off the automatic controls to fly the spacecraft manually for the rest of the trip. Glenn orbited the Earth three times, reporting on what he saw below. Live television coverage carried his words across the country. At one point Glenn said, “I don’t know what you can say about a day in which you have seen four beautiful sunsets.”

During the second orbit, a more seri­ous problem appeared. A warning light suggested that the capsule’s heat shield was loose. This piece on the bottom of the capsule was supposed to protect Glenn when the spacecraft reentered Earth’s atmosphere. If the shield did not remain in place, the capsule-and Glenn-would burn up.

A set of small rockets that sat under­neath the heat shield was supposed to be ejected before reentry began. NASA offi­cials decided to leave them on, hoping that they would help hold the shield in place. In the end, the shield was fine-it turned out the problem was actually with the warning light. Reentry was smooth, although hot, and Glenn’s craft splashed down in the Atlantic Ocean. Soon after, he was picked up by a U. S. Navy ship.

hang glider is a small, light­weight aircraft with no engine. It is controlled by a person who hangs, suspended in a harness, below a triangular wing. The pilot controls the hang glider with body movements and a control bar.

Hang Gliding History

The hang glider concept dates from the pioneer days of aviation at the end of the nineteenth century. German aviator Otto Lilienthal made glider flights, hanging underneath batlike wings that he built himself. His contraptions fitted
the definition of hang glider because Lilienthal controlled them by swinging his body from side to side. He launched himself by running down the slope of a hill. Once in the air, Lilienthal’s control of the glider was always less than com­plete. Although he made more than

2,0 successful glides, a fatal crash in 1896 ended the career of this brave and inventive aviator.

Other inventors saw that the hang glider could lead to larger and more controllable airplanes. Hang gliding
experiments led to the development of larger, person-carrying gliders and then to the first powered airplanes.

Glider, or sailplane, flying developed for sport and recreation during the twentieth century, but hang gliders were mostly forgotten until the 1970s. In that decade, enthusiasts started building them as a cheap, enjoyable way of fly­ing. Their enthusiasm was aided by the availability of lightweight metals, such as aluminum, to construct the frames. New, tough, plastic-based materials were ideal for the wing surfaces. Hang gliding started in the United States, and it soon became popular in other countries.

Today, hang gliding is a popular sport with people who cannot afford to buy or rent a full-size glider. Hang glid­ing equipment is simpler and less costly. These small, portable aircraft are also excellent for people who enjoy flying in places that are not suitable for launch­ing a conventional glider. One of the joys of hang gliding is that the pilot can take the glider almost anyplace flying is permitted. If conditions are suitable, the pilot can be up in the air within a few minutes of unloading the glider from a car trailer. A hang glider is collapsed and folded for transportation and stor­age when not in use.

he Hubble Space Telescope is a reflecting telescope, one that col­lects light from distant objects. Launched into space in 1990, Hubble is run by the U. S. National Aeronautics and Space Administration (NASA) as an orbital observatory. The Hubble tele­scope is named for Edwin Powell Hubble (1889-1953), one of the world’s great astronomers. Its discoveries are valued by astronomers and other space scien­tists all over the world.

Discovering the Universe

At the beginning of the twentieth centu­ry, most astronomers thought there was only one galaxy visible in the universe— the Milky Way—the galaxy of which our Sun and its planets are a tiny part. In 1924, American astronomer Edwin Hubble was using the 100-inch (254- centimeter) Hooker telescope at the Mount Wilson Observatory, near Los Angeles, California. He observed anoth­er galaxy, Andromeda—one of countless galaxies, all of which are apparently moving away from one another at enor­mous speed. Hubble was the first astronomer to propose that the universe was actually expanding. For the first time, scientists realized the true vastness of the universe with its unimaginable number of stars.

Astronomers knew that their optical (light-collecting) telescopes on Earth

HUBBLE FACTS

• Hubble is 43.5 feet (13.3 meters) long-about the length of a school bus-and weighs 24,000 pounds (11,000 kilograms).

• Hubble orbits Earth at a height of about 375 miles (about 600 kilo­meters) and makes one orbit every 97 minutes.

• Compared to the largest telescopes on Earth, Hubble is not especially big-its primary mirror has a dia­meter of 7.9 feet (2.4 meters). It has a secondary mirror, just 12 inches (30 centimeters) in diameter.

• The telescope’s angular resolution, or sharpness of vision, is remarkable.

A person with vision as sharp as Hubble’s could stand in New York City and see bugs on a tabletop as far away as San Francisco.

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could give only a blurred picture of space. Gas and dust in Earth’s atmos­phere make the stars appear to twinkle, but these substances make it difficult to observe faint, distant stars. The atmos­phere also blocks or absorbs electromag­netic radiation from space in wave­lengths other than visible light—radia­tion such as infrared, ultraviolet, gamma rays, and X-rays.

For a clearer view, observatories sited large telescopes on the tops of moun­tains, high above the “optical pollution.”

The idea for a telescope in space, to pro­vide even more clarity, was proposed in 1946 by American scientist Lyman Spitzer. At the time, however, there was no way to get a telescope out there.

Food for the astronauts is brought up from Earth by visiting spacecraft. Most of the food is processed and packaged in pouches or cans, and all the astro­nauts have to do is heat it in a small food warmer or oven. Some food is dehydrated, and the crew adds water to it before eating. Small amounts of fresh food, such as fruit and vegetables, are delivered by spacecraft during their rou­tine trips. Almost all food is stored at room temperature. Although there is a small refrigerator, saving electrical power is a priority, so refrigeration is a luxury in space.

ISS crew members wear casual clothes—often a shirt and shorts or pants. They select their clothing before launch, and often the clothes are sent up to the space station before they arrive there. Astronauts sometimes wear cover­alls for work. There is no washing

О The crew of ISS Expedition Three included two Russians and an American who spent 128 days in 2001 manning the space station.

machine, and so space station crews do not change their clothes very often. Astronauts make their work clothes last, on average, ten days between changes. Underwear and socks are changed every other day. Discarded, dirty clothing is put in a disposal bag and shipped out on the next visit­ing Progress spacecraft. When the unmanned Progress burns up as it reenters Earth’s atmosphere, the dirty cloth­ing, along with the other space station garbage, burns up with it.

When they are off duty,

ISS crew can relax and talk to family and friends on Earth, listen to music, watch movies, play games, read, and work on keeping fit. The human body tends to weaken during long space flights in weight­less conditions, so exercise is a very important part of the astronauts’ routine.

Each crew member is provided with a pair of running shoes to wear when exercising on the treadmill, and another pair of shoes to wear when working out on the exercise bike.

SPACE GOLF

Most of the work done on the space sta­tion is serious science, but in November 2006 two astronauts—Mikhail Tyurin and Mike Lopez-Alegria—finished off a 5/2 hour spacewalk with a golf shot. Wearing Russian Orion spacesuits, the astronauts fixed a tee on a ladder out­side the space station. While Lopez – Alegria held his partner’s feet, the Russian played a one-handed golf shot. This stunt was paid for by a Canadian company in association with the Russian space agency. The ultra-lightweight golf ball (less than 100th the weight of a reg­ular golf ball) was expected to stay in orbit for only a few days.

he great English scientist Sir Isaac Newton (1642-1727) studied the way objects move when forces act on them. His work resulted in three laws of motion that scientists still use today.

On July 5, 1687, three volumes of work by Sir Isaac Newton were pub­lished. The three books were written in Latin, the language of science at that time. Their title is Philosophiae Naturalis Principia Mathematica, which means Mathematical Principles of Natural Philosophy. Natural philosophy was the name in Newton’s time for the science we call physics today. This work is so famous that it is usually simply called the Principia (the Principles).

The three volumes contain details of Newton’s three laws of motion and his law of gravitation. These laws explained and described how all sorts of objects move, even planets. Today, more than 300 years later, Newton’s laws of motion can be used to calculate how aircraft and spacecraft move.

First Law

Newton’s first law of motion says that an object at rest stays at rest, and a moving object moves at a steady speed in a straight line, unless it is acted upon by a force. This is another way of saying that an object does not start moving (or does not change the way it moves) all by itself. If it does start to accelerate, a force must be acting on it. To scientists, the word accelerate does not just mean speed up. It can mean to go faster or slower or to change direction.

An example of Newton’s first law is when an air­craft’s engine power is increased and the extra thrust makes the aircraft accelerate. When a rocket engine fires and a rocket rises off the launch pad, this is Newton’s first law in action as well. The tendency of an object to stay as it is (at rest or moving steadily) unless a force acts on it is known as inertia. Newton’s first law of motion is sometimes called the law of inertia. Inertia increases with

mass. This means that the more mass an object has, the greater the force that is needed to start it moving or stop it again.

A composite is made of two or more materials. Carbon fiber is a composite material. It is made of plastic strength­ened by strands (or fibers) of carbon. The first composite used to build aircraft was a material called Duramold in the 1930s. It was made from thin sheets or strips of wood laid on top of one another with their grains in different directions and then soaked with plastic glue. Having the grains of the layers lying in different
directions made the finished material stronger. A composite material called fiberglass was introduced in the 1950s. Fiberglass is made of plastic strength­ened with glass fibers. It was used in the Boeing 707 airliner.

Today about one-tenth of the Boeing 777 airliner is made of various compos­ite materials. About 24 percent of the new F-22 fighter plane is made from composites, with titanium (39 percent), aluminum (16 percent), steel (6 percent), and other materials (15 percent) forming the rest.

Stealth planes such as the Lockheed F-117 Nighthawk attack plane and the Northrop B-2 Spirit stealth bomber have more composite materials used in their construction than most aircraft, because composites do not reflect radar waves as metals do. Composites help stealth planes to disappear from an enemy’s radar screens.

GLIDER MATERIALS

Gliders, like other aircraft, used to be made from wood, but today they are made from fiberglass, which is extremely lightweight. The parts of the aircraft are made in molds. The inside of a mold forms the outside of the part. The mold is first painted with a substance called gelcoat.

(The gelcoat gives the glider a very smooth, glassy surface that is ideal for reducing air resistance.) Then mats of glass fibers are laid in the mold and soaked with liquid plastic. When the plastic with the glass fibers embedded in it has set hard, the part is popped out of the mold.

The same mold can be used over and over again to produce many identical parts.

an aircraft or spacecraft goes into produc­tion. Flight simulation, shown here for the X-33 in 1997, can provide crucial data to the designer. The X-33, conceived as a reusable space launch vehicle, was canceled in 2001 because of many technical difficulties, including flight instability.

When two or more objects exert forces on each other, their total momentum always stays the same. This is called the law of conservation of momentum, and it helps to explain why aircraft and rockets move.

A rocket engine sends out a high­speed jet of gas when it is fired. The rocket exerts a force on the gas and, according to Newton’s third law of motion, the gas reacts by exerting an equal and opposite force on the rocket. The jet of gas has momentum in one direction. The only way that the total momentum of the rocket and gas can remain the same is if the rocket gains the same momentum in the opposite direction. So, the rocket moves. The same conservation law applies to air­craft. The momentum of the gas rushing out of an aircraft’s jet engines is equal and opposite to the plane’s momentum.

The most advanced navigation system uses the Global Positioning System (GPS), a network of navigation satellites orbit­ing Earth. The GPS system carried by an aircraft picks up radio signals from at least four satellites and uses them to cal­culate the aircraft’s position, altitude, heading, and ground speed. Space-based navigation systems like this are begin­ning to replace radio navigation systems because they are more accurate. In addi­tion, they do not rely on large numbers of beacons on the ground; they are not affected by bad weather; and aircraft are never out of range of the system’s signals.

Navigating Spacecraft

All the planets in the solar system are spinning as well as moving around the Sun at very high speeds. Navigating a space probe from Earth to another pla­net could be compared to sitting on a spin­ning merry-go-round and trying to throw a ball at a spinning top

О The GPS control room at Schriever Air Force Base in Colorado controls the satellites that provide navigational data to users around the world.

placed on a distant moving car. In spite of the challenges, however, space scien­tists have figured out how to send space­craft where they want them to go. Most of the work needed to guide a space probe is done before the launch.

The movements of all the planets are known, and scientists can predict exact­ly where they will be at a given point in the future. The timing of a probe’s launch, the speed it travels, and its direction are all chosen so that the probe is launched from Earth on the right flight path to reach a planet. The pull of the Sun’s gravity and that of the planets has to be taken into account when cal­culating the probe’s flight path. In fact, gravity is sometimes used to accelerate a probe or to change its direction without having to burn any fuel.

When the Space Shuttle goes to the International Space Station, its launch time is chosen to place it in orbit near
the Space Station. The Space Shuttle only has to make small adjustments to its position to rendezvous with the Space Station.

The job of an airline pilot can seem exciting. Pilots jet around the world, and they are well paid, but the routine involves hard work, a lot of waiting time, and heavy responsibilities. The pilot and first officer’s tasks include fig­uring out a flight plan showing the route, flying height, and fuel capacity. They supervise loading and fueling of the aircraft, brief the cabin crew, and carry out preflight checks. Airline pilots must communicate constantly: with air traffic control before takeoff, during the flight, and while landing, and with their passengers during the flight. They check the aircraft’s technical performance, and position, the weather, and air traffic. At the end of a flight, pilots update the air­craft logbook and write reports about any incidents during a flight.

At all times, an airline pilot must be ready to act promptly should an emergency occur. A pilot is responsible for the safety of the aircraft and its pas­sengers. In the wake of the terrorist attacks in New York City in September 2001, airspace security was tightened up to protect potential terrorist targets.

О Most airline pilots in the United States belong to the Air Line Pilots Association, a labor union and professional organization for pilots founded in 1931.

Pilots are aware that the FAA may impose temporary flight restrictions (TFRs) to restrict aircraft movements in certain areas, for example around air shows, space launches, forest fires, or presidential visits.

TFRs also protect potential targets, such as military bases and government installations.

Since the early days of manned space­flight, spacecraft have been able to dock (link up) with each other. The Gemini program carried out the first docking in 1966 as a step toward a successful Moon landing mission. Apollo Command Modules docked with the U. S. Skylab space station. The Space Shuttle, Soyuz

DEFEATING RADAR

During the Cold War, the United States and Soviet Union competed with each other to produce the most advanced military radar for their combat aircraft. They also developed ground-based radar to give early warning of a missile attack. This competition led to research into ways of defeating enemy radar. There are six main methods used to con­fuse or block radar systems:

• Electronic jamming: Sending out radio signals to block or swamp enemy radar.

• Generating false targets:

Sending out radio signals that make extra, confusing information appear on enemy radar screens.

• Chaff: Dropping metal strips from an aircraft to create confusing radar reflections.

• Decoys: Employing small flying objects that look like full-size aircraft on a radar screen.

• Anti-radiation missiles:

Destroying enemy radar by homing in on radio signals they transmit.

• Stealth: Manufacturing military aircraft that produce little or no radar reflection.

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capsules, and unmanned Progress sup­ply craft have docked with the Russian Mir space station and with the International Space Station.

Docking is a difficult maneuver. In space, without any nearby landmarks by which to judge distance and speed, it is almost impossible to determine how far away a spacecraft is or how fast it is moving. A crew onboard the Mir

О Joining one spacecraft with another in space is called docking, and radar is needed for this maneuver to measure distances and speed of approach. This computer-generated image shows the Space Shuttle Atlantis docked to the Russian space station Mir, which orbited Earth from 1986 to 2001.

space station in 1997 discovered this problem when they were docking an unmanned supply craft with their space sta­tion without the use of radar. The craft, controlled by a cosmonaut in Mir, approached the station too fast and crashed into it.

Radar is usually used for all docking maneuvers. It provides accurate meas­urements of the distance between spacecraft and their closing speed. Linked to a spacecraft’s guidance system, it can carry out docking automatically. When the Apollo lunar excursion modules descended from lunar orbit to the Moon’s surface during the Apollo land­ings of the 1960s and 1970s, the descent was controlled by radar. Landing radar kept the guidance computer constantly updated with data on the spacecraft’s altitude and rate of descent.