Category FLIGHT and M ОТІOIM

The calculations involved in space navi­gation are complex. The launch base (Earth), the space probe, and the probe’s target (a moon of one of the giant plan­ets, perhaps) are all moving through space. Ground controllers must calculate

launch speed and course precisely. If necessary, they make midcourse correc­tions by using computers to fire small rocket motors onboard the spacecraft. In this way, scientists can send a probe on voyages that will last for years.

When deciding on a launch date for a planetary probe, scientists choose a favorable “window,” usually when the target planet is at its closest. Moving between planets in space seldom involves traveling in a straight line. Keeping a space probe on the right course requires smart computing and

accurate gyroscopes on the spacecraft. The gyroscopes are used for inertial guidance to keep the space probe on course without reference to the Sun or stars. Instruments measure the slightest change in the spacecraft’s acceleration so that computers can calculate any adjust­ment to the course. When planning a multiplanet mission, scientists may be able to send the probe on a “slingshot” trajectory. This takes the probe around one planet and then uses the planet’s gravitational pull to accelerate it off to the next target. Pioneer 11 did this in 1975, swinging around Jupiter onto a path that took it to Saturn.

The Space Shuttle is about the same size and weight as a medium-size airliner, but crew conditions inside are cramped. The cargo bay takes up the middle of the spacecraft. The main engines and orbital maneuvering systems are in the tail sec­tion. The flight deck and living quarters, are confined to the forward fuselage. On the flight deck, two pilot seats are fitted with manual controls in addition to the automatic systems. The pilots have more than 2,000 separate displays and controls on the flight deck to monitor. The mid-deck area con­tains four crew sleep stations, the waste management system, a personal hygiene station, and a table used for work and meals.

The mid-deck also contains an area for scientific experiments.

О A large truss (support) for the International Space Station arrives at the Kennedy Space Center in 1999. The Space Shuttle carried the truss in its cargo bay to the space station, where it was installed by astronauts.

To carry out extravehicular activity (EVA), or spacewalks, the crew exits the Space Shuttle through an airlock, wear­ing spacesuits. The airlock has room for two crew members to change spacesuits. An EVA that involves a complex task in the payload bay may last up to 6 hours. One of the tools that Space Shuttle astronauts may use is the Remote Manipulator System (RMS), a 50-foot (15-meter) articulating arm, remotely controlled from the flight deck. The arm has a video camera near its tip, so the operator can see clearly when doing delicate assembly or repair work.

In 1977, Lockheed began the top-secret Have Blue project for the Defense Advanced Research Projects Agency (DARPA), the central research and devel­opment organization of the U. S. Depart­ment of Defense. Skunk Works came up with a design that looked like a pyramid with wings and two tails. It was almost invisible to radar when mounted on a pole on the ground, but would it fly? The plane’s unusual shape made it unstable, and it could not have flown successfully without the aid of comput­er technology. Computerized fly-by-wire systems were already in use on planes such as the F-16, constantly adjusting the flight controls to prevent the plane from losing stability and crashing. The secret stealth plane, designated the F-117, was equipped with such a system.

The F-117 was test flown in the Nevada desert in 1981. It was like no other plane. Anything that gave off a radar trace was eliminated from the air­craft, so antennae and sensors were designed to retract into the fuselage. The F-117 had no radar system of its

TECH ‘kTALK

THE F-117

The F-117 Nighthawk is a single-seat airplane powered by two General Electric turbofan engines. It flies at just below the speed of sound (Mach 1). Its principal weapons are two 2,000-pound (907-kilogram) laser-guided bombs, or air-to-surface missiles. The wings and fuselage are aerodynamically blended. They are made of a conventional material, aluminum, but are coated with spe­cial radar-absorbent materials. The Nighthawk weighs about 52,000 pounds (about 23,000 kilograms) when fully loaded.

own to betray its position. The cockpit was coated with a reflective material that radar beams bounced off in all directions. The engine intakes were screened, and exhaust gases were cooled by heat absorbers so that little trace showed on heat sensors.

Initially, the F-117 was not an easy aircraft to fly. Two early prototypes crashed, in 1978 and 1980, but the pro­gram continued with two more test air­craft. The first F-117A was handed over to the U. S. Air Force in 1982 and went operational the following year. It was still top secret, flying only at night. The public became aware of the mystery plane, named the Nighthawk, in 1989, when it took part in operations against Panama. F-117s also flew missions against Iraq during the Gulf War in 1991.

The Space Shuttle’s tail is a complicated structure that contains a total of thirty – three rocket engines and thrusters. There are three main engines that are used only during launch. Two smaller Orbital Maneuvering System (OMS) engines boost the spacecraft into orbit, change its orbit, and slow the spacecraft down to begin its return to Earth. In addition, there are twenty-four pri­mary thrusters and four smaller thrusters, called vernier thrusters, for small changes in speed and attitude control.

The Space Shuttle’s tail fin, or vertical stabi­lizer, stands more than 26 feet (8 meters) high. Its rudder is unique.

О NOTAR helicopters, with no tail rotor, offer reduced noise and vibration. They are also safer to fly in tight situations where a tail rotor might meet an obstruction.

The first privately operated space plane, SpaceShipOne, has an unusual tail. When the space plane reaches the highest point in its flight-about 70 miles (110 kilometers)— its twin tail booms swivel up so that they stick straight up from the small wings. This jackknifed position enables it to reenter the atmosphere safely. The reentry is ballis­tic, which means SpaceShipOne falls back into the atmosphere under the action of gravity alone, like a rock falling to Earth. No engine power is used. The jackknifed shape causes a lot of drag, which slows the craft down. At an altitude of 50,000-60,000 feet (15,250-18,300 meters), the pilot swivels the tail booms down again, and the craft glides down to land on a runway.

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It works not only as a rudder but also as a speed brake. When it swivels to the left or right, it works as a rudder. To work as a speed brake, it splits in two and opens like a book. Half of it swivels to the left, and the other half swivels to the right.

SEE ALSO:

• Aileron and Rudder • Control System • Pitch, Roll, and Yaw

• Stability and Control

Date of birth: June 1, 1907.

Place of birth: Coventry, England.

Died: August 9, 1996.

Major contributions: Invented the jet engine; built a jet engine used in an air­plane that set speed and altitude records. Awards: Knight of the Order of the British Empire; Albert Medal; Order of Merit; Charles Stark Draper Prize; SAE Aerospace Engineering Award.

he son of a mechanic, Frank Whittle joined the British Royal Air Force (RAF) at the age of six­teen. His work with model airplanes caught the eye of an officer who recom­mended him for officer training. During training, Whittle wrote a detailed essay about the possibility of developing a new kind of aircraft engine that would not turn a propeller. He wrote that planes could reach higher altitudes and faster speeds if exhaust from the engine provided the thrust.

Higher-ranking offi­cers dismissed Whittle’s ideas, but he continued to pursue them. His ini­tial plan used a piston to compress air, but he con­cluded that such an engine would weigh too much. Whittle developed a new approach using a turning turbine. Once again, however, his supe­riors rejected the idea. In 1930, Whittle patented the idea himself.

Little happened with Whittle’s idea until he was approached six years later by Rolf Dudley- Williams and James Tinlin, about the possi­bility of developing his engine. The three formed a company-Power Jets Limited-in 1936 and began work on building a model of Whittle’s
engine plans. On April 12, 1937, they tested the engine, which was mounted on a stand on the ground. It worked per­fectly. A scientist who learned of the success convinced the RAF to provide funding to develop an airplane that used the new engine.

That work took place slowly. A suc­cessful test of a newer version of the engine in 1939 spurred quicker work. The prototype plane, built by Gloster, arrived late in 1940, and Whittle built the engine at Power Jets facilities. The engine was tested successfully late in 1940. On May 15, 1941, the Gloster plane, with Whittle’s engine inside, flew for 17 minutes. It reached a top speed of 340 miles per hour (545 kilometers per
hour). The success convinced RAF offi­cials to move ahead with the aircraft.

In 1944, the British government took control of Whittle’s company. In 1948, Whittle resigned from the company and from the RAF due to ill health. For the next twenty years or so, he worked as a consultant for various companies. Some of his work focused on jet engines. Whittle also designed a new kind of drilling head for oil drills. In 1976, he moved to the United States, where he taught at the U. S. Naval Academy.

Airplanes joined the civilian bombing campaign in November 1916, when a German plane dropped six bombs on London. A typical large bomber plane of the war was the British Handley Page 0/100 (1916). The figure 100 referred to its wingspan, which was 100 feet (30 meters). The Handley Page 0/100 had two Rolls-Royce engines, giving it a top speed of 97 miles per hour (156 kilometers per hour), and it could fly for 8 to 9 hours. Such bombers flew from Britain to attack railroad depots, docks, and submarine bases along the coast of Belgium and in Germany. In 1917, a single 0/100 flew in several legs from Britain to the Greek island of Lemnos. From an airfield there, it bombed German warships in the Turkish city of Constantinople (now Istanbul).

Even larger bombers took to the sky. These giants included the four – engine Russian Ilya Muromets (designed by Igor Sikorsky) and the three-engine Italian Caproni Ca 42 (a triplane). The Zeppelin company in Germany built the R-type bombers, which carried engineers to service the

EDWARD RICKENBACKER (1890-1973)

Born in Columbus, Ohio, in 1890, Eddie Rickenbacker was a professional auto­mobile racer before World War I. He enlisted in the U. S. Army in 1917, serving as a driver before becoming a pilot. Rickenbacker shot down twenty-two enemy planes and four balloons, becom­ing the leading American ace pilot in World War I. During World War II, he worked as an inspector of military air­bases and survived three weeks on a raft in the Pacific Ocean after his plane came down. A successful businessman in peacetime, Rickenbacker later co-owned the Indianapolis Speedway and was president of Eastern Airlines.

engines on long flights. The biggest R – type bomber was still unfinished when the war ended. It had six engines and longer wings than a World War II Lancaster bomber.

A smaller German bomber, the Gotha, was made of plywood. It cruised at 80 miles per hour (130 kilometers per hour) and carried over 1,000 pounds (450 kilograms) of bombs, including incendiaries (firebombs). Gothas were used to raid London by night during 1917 and 1918. Gotha crews had to be tough-they sat in open cockpits, muf­fled against the cold.

The British and French retaliated with small, fast bombers, such as the DH-4 and Breguet Br-14, single-engine airplanes flying at around 120 miles per hour (190 kilometers per hour), which

was as fast as a fighter. The British were planning raids on Berlin, using their new V/1500 bomber, when the war ended in 1918. This plane could carry almost 100 times the weight of bombs carried by a 1914 plane.

The Wrights offered to build airplanes for the U. S. Army, but the army turned them down until 1908, when it agreed to pay $25,000 for an airplane that could carry a passenger and fly for an hour. Soon after, the Wrights struck a deal to license the plane to French investors as well. They designed and tested a new airplane with a passenger seat. On May 14, 1908, Wilbur took mechanic Charles Furnas into the air in the world’s first passenger plane.

In 1909, the brothers opened the Wright Company in Dayton to build air­planes. They also started a flying school. The brothers became unpopular, how­ever, when they brought several lawsuits charging other aviators with taking their ideas. Although law courts typically found in their favor, the brothers’ actions struck the public as mean-spirited.

In 1912, Wilbur died of typhoid fever, and Orville took over running the business. He spent much of the rest of his life vigorously promoting the brothers’ achievement. In 1948, at the age of seventy-seven, Orville died of a heart attack.

THE GRANDEST SIGHT "When it first turned that circle, . . .

I said then, and I believe still, it was. . . the grandest sight of my life. Imagine a locomotive that has left its track, and is climbing up in the air right toward you-a locomotive without any wheels, we will say, but with white wings instead. . . . Well, now, imagine this white locomotive, with wings that spread 20 feet each way, coming right toward you with a tremendous flap of its propellers, and you will have something like what I saw."

Scientists who specialize in aerody­namics are known as aerodynamicists.

They put a lot of time and effort into reducing drag because drag wastes fuel. A plane’s engines have to burn fuel to generate the power necessary to over­come drag. Improving a plane’s aerody­namics can enable it to fly farther with­out burning any more fuel. Because drag acts like a brake, reducing drag also enables the fastest airplanes to go even faster. Improving a glider’s aerodynamic design enables it to stay aloft longer.

One way to study aerodynamics is to use a wind tunnel. Air is blown through a tunnel with a model aircraft inside. As the air flows around the model, the forces acting on it are measured.

Scientists would like to be able to calculate precisely how a plane will per­
form in the air instead of having to build models to test every design and every change in a design. Such calculations, however, present a formidable task. That task involves calculating the aerody­namic forces acting on every part of an aircraft as it flies through the air at all angles and speeds. To do this, the air flowing around the aircraft is divided into tiny packets called cells. The forces acting on each and every cell must be calculated to figure out how each cell moves and how it affects the aircraft. Each cell affects all the cells around it. In turn, they affect other cells, which affect yet others, making the problem incredi­bly complicated.

The method of using computers, numbers, and mathematical equations to figure out how air flows around an object is known as computational fluid dynamics (CFD). Only the fastest super­computers have the ability to use CFD to tackle complicated aerodynamics.

The atmosphere is not the same all the way up from the ground. It is divided into four layers: the troposphere, strato­sphere, mesosphere, and thermosphere.

The lowest layer is the troposphere. It extends from Earth’s surface up to a height of about 4 miles (6.4 kilometers) at the poles and 11 miles (17.7 kilome­ters) at the equator. Most weather and clouds occur in the troposphere. Temperature falls with height, dropping to about -112°F (-80°C) at the top. Clouds are produced by water vapor ris­ing into the colder air and changing into water droplets or ice crystals.

Jet streams are fast air currents found near the top of the troposphere. They are studied by meteorologists, because they affect the weather below them. The jet streams’ winds blow from west to east. The wind speed is normally 35 to 75 miles per hour (56 to 121 kilometers per hour), but speeds of more than 250 miles per hour (402 kilometers per hour) have been recorded. An airliner using the jet stream to fly eastward can fly faster without burning any more fuel.

The layer above the troposphere is the stratosphere. The stratosphere is drier and less dense than the layer below it. It goes up to a height of about 31 miles (50 kilometers) above Earth’s sur­face and contains the ozone layer. Ozone is a type of oxygen with three atoms instead of the usual two. This gas soaks up harmful ultra-violet radiation from the Sun. Because of this, the temperature rises with height in the stratosphere, up to about 32°F (0°C) at the top.

The next layer is the mesosphere. It goes from about 31 miles (50 kilometers) above Earth’s surface up to about 53 miles (85 kilometers). Less is known

О This diagram shows the layers of the atmos­phere and the exosphere. Some satellites orbit Earth in the exosphere; others are out in space.

about the mesosphere than the lower layers because it is too high for most air­craft to fly in and too low for most spacecraft to orbit in. Temperature falls yet again in the mesosphere, down to about -148°F (-100°C).

In the early days of aviation, airplanes were small and flew slowly. The public showed little interest in air travel, and businesses did not consider air freight as a way to move their goods around. Not until 1912 did an airplane exceed 100 miles per hour (160 kilometers per hour) to match a railroad train or automobile. Planes were faster than ships, but they could not cross the wide oceans. Nor could they carry more than one or two people at a time.

The first known freight flight took place in 1910, when the Ohio company Morehouse-Martens hired Philip O. Parmalee to fly two packages of silk between its stores in Columbus and Dayton, Ohio. This was a publicity stunt, but the practice of carrying mail by air seemed a good idea and soon caught on.

AIRMAIL

Airmail flights began in September 1911, when the U. S. Postmaster-General awarded pilot Earl L.

Ovington the title of Air Mail Pilot Number One.

On May 15, 1918, the U. S.

Postal Service introduced a daily airmail service between New York City,

Washington, D. C., and Philadelphia. For the first few months, army avia­tors flew the airmail routes. Civilian pilots were then trained, and

the airmail service was gradually expanded. The first coast-to-coast airmail was delivered in the United States in 1921. The mail left San Francisco at 4:30 a. m. on February 22 and reached Long Island, New York, at 4:50 the following afternoon. Soon, regular flights operated between New York and San Francisco. In 1927, the Postal Service turned its airmail network over to the newly emerging airlines.

In 1912, there were only 2,400 licensed pilots in the world, more than 900 of whom were in France. There were fewer than 200 pilots in the United States. Things changed rapidly after World War I (1914-1918). Aircraft were bigger, faster, and more reliable. There were many more pilots available, trained as military fliers and now released from service. Record-breaking flights, such as the first crossing of the Atlantic Ocean in June 1919 by John Alcock and Arthur

Whitten Brown, showed that long­distance flight was no longer a dream.