Category FLIGHT and M ОТІOIM

Staying on Course

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

Staying on Course

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

Staying on Course

О A conceptual illustration by NASA shows how samples could be launched from the surface of Mars in a capsule that would bring them back to Earth as part of future missions to Mars.

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.

Developing the F-117

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.

Подпись: О The Tacit Blue was a research aircraft built to demonstrate that curved surfaces could avoid radar. It flew first in 1982 after several years of development and was retired in 1985.

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.

Whittle, Frank

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.

T

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.

Подпись: THE FIRST JET PLANE
Whittle, Frank

Подпись:

Подпись: Whittle invented the jet engine, but a German designed the first successful jet plane. In 1936, Hans von Ohain (1911-1988) patented a type of jet engine. Soon after, he perfected his design with the German aircraft manufacturer Heinkel. On August 27, 1939, it was used on a plane to produce the first jet-powered plane flight. After World War II, von Ohain moved to the United States. When he and Whittle met, Whittle regarded him coldly, feeling that von Ohain had stolen some of his work. When von Ohain finally convinced him that was not the case, they became friends and worked together. When Frank Whittle won the Charles Stark Draper Prize and the SAE Aerospace Engineering Award, he did so jointly with Hans von Ohain.

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.

. Success in Business

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."

Working Together

The Apollo triumph persuaded many people that the United States had won

Подпись: О In 1995, U.S. Space Shuttle astronaut Robert Gibson met and shook hands with cosmonaut Vladimir Dezhurov during the first international docking mission of the Space Shuttle with the Russian space station Mir. The mission, STS-71, commemorated the Apollo-Soyuz Test Project twenty years earlier, which brought the space race to a symbolic close. the space race. No Soviets flew to the Moon, although unmanned Zond space­craft may have flown test flights for a Moon mission. Soviet plans for a Moon landing were abandoned, prob­ably because of serious problems with the rocket launcher and the lunar space­craft. The closest the Soviet Union came to the Moon was when two small robot vehicles crawled over the dusty lunar surface. Instead, the Soviets turned their attention to orbital space stations, such as Salyut 1 (1971) and later Mir. In 1975, on the Apollo-Soyuz Test Project, American and Soviet astronauts flew together in space. A new era of cooperation had begun.

By the 1980s, the space race was over. Relations between the United States and the Soviet Union improved, with the signing of treaties agreeing to bans on nuclear weapons testing and cut­backs in the production of missiles.

The United States introduced the Space Shuttle in 1981. Although they launched their Buran shuttle in 1988, the Soviets never seriously competed with the new, reusable spacecraft.

In 1989, the Soviet Union broke apart into separate countries. Since then, Russia has worked as a partner with the United States to build and operate the International Space Station. New partic­ipants in space include the European Space Agency (ESA) and China. (China became the third nation to launch an astronaut, in 2003.)

The space race provided significant technological spin-offs (especially in electronics) and led to an increase in sci­ence education. A future space race might be a commercial contest between companies offering space tourism, but most people believe that the future of scientific space exploration lies in inter­national cooperation rather than in a race for the stars.

SEE ALSO:

• Apollo Program • Astronaut

• Gagarin, Yuri • Glenn, John

• Spaceflight • Sputnik

Подпись: ~Подпись: ГV.

Testing and Using SVS

Подпись:
Testing and Using SVSПодпись: The TIFS aircraft is a modified C-131 Samaritan military aircraft, which is itself based on a Convair 580 turboprop airliner. It was built in the 1950s and converted to a flying simulator in the late 1960s. TIFS has two cockpits. One is used to test new developments. The other (standard) cockpit can take over at any point if necessary. This double cockpit is an important feature, because it allows a test pilot safely and repeatedly to push a system all the way to failure, which is risky to do in a conventional flight test, especially near the ground. The research cockpit can be programmed to make the plane fly like other kinds of aircraft. In its test flights, it has doubled for a variety of airliners, experimental aircraft, the B-2 Spirit stealth bomber, and even the Space Shuttle. As well as simulating other aircraft, it also is used to test new avionics systems. In this case, the second cockpit can be replaced by a nose section containing the new avionics, and the research pilot sits at a crew station in the aircraft's cabin. Pilots say it is more realistic to fly TIFS than a simulator on the ground because it sounds, feels, and performs like the real airplane. The TIFS plane entered service as a military transport on March 22, 1955, so it cele-brated its fiftieth anniversary in 2005. к J
In 1999, synthetic vision was tested in flight by a modified C-131 military aircraft named the Total In-Flight Simulator (TIFS). For the tests, TIFS was fitted with screens to try a variety of dif­ferent images and data. The research flights were made out of Asheville Regional Airport in North Carolina.

Подпись: О A pilot testing SVS in 1999 was able to compare the virtual world on his screen with a view from the cockpit.Testing and Using SVSПодпись: — SEE ALSO: Testing and Using SVSResearch pilots using the synthetic vision system reported that they soon forgot they were looking at a computer-generated image and not at the real world.

System designers are already thinking about other ways in which SVS might be used in the future. One possible application is in air traffic control systems at airports.

Airport traffic con­trollers work in a con­trol room that looks out across the airport, but some parts of an airport may be obscured by buildings or bad weather. SVS could provide con­trollers with a clear, computer-generated view of the entire air­port in all conditions. Although synthet­ic vision has been developed for civil aviation, military forces also are interest­ed in the systems. Synthetic vision already has been flight tested in military airplanes and helicopters.

• Air Traffic Control • Avionics

• Cockpit • Global Positioning System • Pilot

Other Kinds of Wings

Fixed-wing airplanes are not the only aircraft that use wings. A helicopter’s rotor blades are actually long, thin wings. High-performance parachutes called parafoils are really inflatable wings. The parachute is made of two layers of fabric with dividers between them, forming a line of pockets, or cells. As the parachute moves along,
air fills the cells and forms a wing shape. The parachutist con­trols and steers the parafoil by pulling control lines that change the wing’s shape.

A flexible fabric hang glider is yet another type of wing. Called a Rogallo wing, this early hang glider was developed in the 1940s by hus­band and wife, Francis and Gertrude Rogallo. When space exploration began, NASA investigated the Rogallo wing as a way of landing the Gemini manned spacecraft. Round parachutes eventually were used instead, but the Rogallo wing was used by other designers, who devel­oped it into the modern hang glider.

Racecars also use wings. However, racecar wings do the opposite job of air­craft wings. They produce a downward force, called downforce, when they cut through air. This pushes the car down harder against the ground, giving its tires better grip, and enabling it to take corners faster without loss of traction.

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SEE ALSO:

• Aerodynamics • Aileron and

Rudder • Bernoulli’s Principle

• Lift and Drag • Stall

Tightening Security

Such attacks highlighted a new threat to air travel and the need for tighter securi­ty at airports. The Hague Convention of 1970, an international agreement signed by more than 130 nations, was drawn up to combat skyjacking and stop terrorists from escaping to “friendly” countries.

From 1973, the Federal Aviation Administration in the United States has required all airlines to screen passengers and their baggage to prevent people from carrying weapons-or objects that might be used as weapons-onto flights. Airports tightened security procedures, especially at check-in and during bag­gage handling. Armed guards, called sky marshals, traveled on some flights.

When an airplane is hijacked, mili­tary craft may escort it to a landing field
agreed to by the authorities. After it has landed, troops and police will surround the hijacked aircraft while skilled nego­tiators try to talk the skyjackers into releasing the hostages and surrendering. Armed assault also may be used. In 1976, following the hijacking of an Air France flight, Israeli commandos flew in to attack the Palestinian hijackers, who were holed up at Entebbe Airport in Uganda, Africa. The commandos rescued more than 100 hostages. In most hijack­ing situations, however, airport and law enforcement agencies usually try to avoid a gun battle, which risks injuring or even killing innocent hostages.

Skyjacking incidents decreased in the United States during the 1980s and 1990s, but violent terrorist incidents continued to take place in other parts of the world. Some of these skyjackings resulted in airplanes crashing. In 1996, a stolen Ethiopian airliner crashed into the Indian Ocean. About fifty passengers

Tightening Security

managed to survive, but the crash killed 125 of the people onboard.

The Soviet Plan

The Soviets had been developing power­ful rocket motors for some time, and they originally had hoped to launch a large satellite packed with scientific instruments. They scaled down their plan when they learned how small Vanguard was (the U. S. satellite weighed only 3.5 pounds, or 1.5 kilograms).

To ensure success, the Soviets opted to start by launching Sputnik 1, an “artificial moon” simpler and smaller than their science satellite, but still much bigger and heavier than its U. S. rival. Soviet space scientists were confi­
dent of putting this small satellite into orbit, even if its scientific value would be limited.

Sputnik 1 was designed and built in conditions of great secrecy by a team of Soviet scientists and engineers led by Sergey Korolev (1907-1966), chief designer of the Soviet space bureau. Korolev had helped design the long – range ballistic missiles from which the R-7 satellite launcher rocket was devel­oped. After successful R-7 test flights in the summer of 1957, a modified version of the R-7 was prepared to launch Sputnik 1 .

Terminal Velocity

When something falls through the air toward the ground, the force of gravity makes it accelerate. As it accelerates, the drag (air resistance) it experiences increases. If it falls for long enough, its weight is exactly balanced by drag, and it stops accelerating. This velocity is called its terminal velocity.

A large but very light object, such as a feather, reaches its terminal velocity very quickly. A heavier object of the same size has a higher terminal velocity, because a higher speed is needed to cre­ate enough drag to balance its weight.

In the usual skydiving position­falling with arms and legs held out-a skydiver’s terminal velocity is about 120 miles per hour (195 kilometers per hour). With arms and legs pulled in, however, there is less drag, and the skydiver accelerates. Terminal velocity increases to about 200 miles per hour (320 kilo­meters per hour) before weight and drag are once again balanced.

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SEE ALSO:

• Gravity • Laws of Motion

• Relativity, Theory of • Skydiving

• Speed

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