Synthetic DNA

The invention: 



A method for replicating viral deoxyribonucleic

acid (DNA) in a test tube that paved the way for genetic engineering.



The people behind the invention:



Arthur Kornberg (1918- ), an American physician and

biochemist

Robert L. Sinsheimer (1920- ), an American biophysicist

Mehran Goulian (1929- ), a physician and biochemist









The Role of DNA



Until the mid-1940’s, it was believed that proteins were the

carriers of genetic information, the source of heredity. Proteins

appeared to be the only biological molecules that had the complexity

necessary to encode the enormous amount of genetic information

required to reproduce even the simplest organism.

Nevertheless, proteins could not be shown to have genetic properties,

and by 1944, it was demonstrated conclusively that deoxyribonucleic

acid (DNA) was the material that transmitted hereditary

information. It was discovered that DNA isolated from a

strain of infective bacteria that can cause pneumonia was able to

transform a strain of noninfective bacteria into an infective strain;

in addition, the infectivity trait was transmitted to future generations.

Subsequently, it was established that DNA is the genetic material

in virtually all forms of life.

Once DNA was known to be the transmitter of genetic information,

scientists sought to discover how it performs its role. DNA is a

polymeric molecule composed of four different units, called “deoxynucleotides.”

The units consist of a sugar, a phosphate group, and a

base; they differ only in the nature of the base, which is always one of

four related compounds: adenine, guanine, cytosine, or thymine. The

way in which such a polymer could transmit genetic information,

however, was difficult to discern. In 1953, biophysicists James D.Watson

and Francis Crick brilliantly determined the three-dimensional

structure of DNAby analyzing X-ray diffraction photographs of DNA

fibers. From their analysis of the structure of DNA,Watson and Crick

inferredDNA’s mechanism of replication. Their work led to an understanding

of gene function in molecular terms.

Watson and Crick showed that DNA has a very long doublestranded

(duplex) helical structure. DNAhas a duplex structure because

each base forms a link to a specific base on the opposite

strand. The discovery of this complementary pairing of bases provided

a model to explain the two essential functions of a hereditary

molecule: It must preserve the genetic code from one generation to

the next, and it must direct the development of the cell.

Watson and Crick also proposed that DNA is able to serve as a

mold (or template) for its own reproduction because the two strands

ofDNApolymer can separate. Upon separation, each strand acts as a

template for the formation of a new complementary strand. An adenine

base in the existing strand gives rise to cytosine, and so on. In

this manner, a new double-stranded DNAis generated that is identical

to the parent DNA.





DNA in a Test Tube



Watson and Crick’s theory provided a valuable model for the reproduction

of DNA, but it did not explain the biological mechanism

by which the process occurs. The biochemical pathway of DNA reproduction

and the role of the enzymes required for catalyzing the

reproduction process were discovered by Arthur Kornberg and his

coworkers. For his success in achievingDNAsynthesis in a test tube

and for discovering and isolating an enzyme—DNA polymerase—

that catalyzed DNA synthesis, Kornberg won the 1959 Nobel Prize

in Physiology or Medicine.

To achieve DNAreplication in a test tube, Kornberg found that a

small amount of preformed DNA must be present, in addition to

DNApolymerase enzyme and all four of the deoxynucleotides that

occur in DNA. Kornberg discovered that the base composition of

the newly made DNAwas determined solely by the base composition

of the preformed DNA, which had been used as a template in

the test-tube synthesis. This result showed that DNA polymerase

obeys instructions dictated by the template DNA. It is thus said to

be “template-directed.” DNA polymerase was the first templatedirected

enzyme to be discovered.

Although test-tube synthesis was a most significant achievement,

important questions about the precise character of the newly

made DNAwere still unanswered. Methods of analyzing the order,

or sequence, of the bases in DNA were not available, and hence it

could not be shown directly whetherDNAmade in the test tube was

an exact copy of the template of DNA or merely an approximate

copy. In addition, some DNAs prepared by DNA polymerase appeared

to be branched structures. Since chromosomes in living cells

contain long, linear, unbranched strands of DNA, this branching

might have indicated that DNA synthesized in a test tube was not

equivalent to DNA synthesized in the living cell.

Kornberg realized that the best way to demonstrate that newly

synthesizedDNAis an exact copy of the original was to test the new

DNAfor biological activity in a suitable system. Kornberg reasoned

that a demonstration of infectivity in viral DNA produced in a test

tube would prove that polymerase-catalyzed synthesis was virtually

error-free and equivalent to natural, biological synthesis. The

experiment, carried out by Kornberg, Mehran Goulian at Stanford

University, and Robert L. Sinsheimer at the California Institute of

Technology, was a complete success. The viral DNAs produced in a

test tube by the DNA polymerase enzyme, using a viral DNA template,

were fully infective. This synthesis showed that DNA polymerase

could copy not merely a single gene but also an entire chromosome

of a small virus without error.





Consequences











The purification of DNApolymerase and the preparation of biologically

active DNA were major achievements that influenced

biological research on DNA for decades. Kornberg’s methodology

proved to be invaluable in the discovery of other enzymes that synthesize

DNA. These enzymes have been isolated from Escherichia

coli bacteria and fromother bacteria, viruses, and higher organisms.

The test-tube preparation of viral DNA also had significance in

the studies of genes and chromosomes. In the mid-1960’s, it had not

been established that a chromosome contains a continuous strand of

DNA. Kornberg and Sinsheimer’s synthesis of a viral chromosome

proved that it was, indeed, a very long strand of uninterrupted

DNA.

Kornberg and Sinsheimer’s work laid the foundation for subsequent

recombinant DNAresearch and for genetic engineering technology.

This technology promises to revolutionize both medicine

and agriculture. The enhancement of food production and the generation

of new drugs and therapies are only a few of the subsequent

benefits that may be expected.





See also : Artificial hormone; Cloning; Genetic“fingerprinting”;

Genetically engineered insulin; In vitro plant culture;

Synthetic amino acid;Artificial gene synthesis.





Further Reading

Synthetic amino acid

 The invention :



Amethod for synthesizing amino acids by combining
water, hydrogen, methane, and ammonia and exposing the
mixture to an electric spark.



The people behind the invention : 



Stanley Lloyd Miller (1930- ), an American professor of
chemistry

Harold Clayton Urey (1893-1981), an American chemist who
won the 1934 Nobel Prize in Chemistry



Aleksandr Ivanovich Oparin (1894-1980), a Russian biochemist

John Burdon Sanderson Haldane (1892-1964), a British scientist







Prebiological Evolution



The origin of life on Earth has long been a tough problem for scientists

to solve. While most scientists can envision the development

of life through geologic time from simple single-cell bacteria

to complex mammals by the processes of mutation and natural selection,

they have found it difficult to develop a theory to define

how organic materials were first formed and organized into lifeforms.

This stage in the development of life before biologic systems

arose, which is called “chemical evolution,” occurred between

4.5 and 3.5 billion years ago. Although great advances in

genetics and biochemistry have shown the intricate workings of

the cell, relatively little light has been shed on the origins of this intricate

machinery of the cell. Some experiments, however, have

provided important data from which to build a scientific theory of

the origin of life. The first of these experiments was the classic

work of Stanley Lloyd Miller.

Miller worked with Harold Clayton Urey, a Nobel laureate, on the

environments of the early earth. John Burdon Sanderson Haldane, a

British biochemist, had suggested in 1929 that the earth’s early atmosphere

was a reducing one—that it contained no free oxygen. In

1952, Urey published a seminal work in planetology, The Planets, in

which he elaborated on Haldane’s suggestion, and he postulated

that the earth had formed from a cold stellar dust cloud. Urey

thought that the earth’s primordial atmosphere probably contained

elements in the approximate relative abundances found in the solar

system and the universe.

It had been discovered in 1929 that the Sun is approximately 87

percent hydrogen, and by 1935 it was known that hydrogen encompassed

the vast majority (92.8 percent) of atoms in the universe.

Urey reasoned that the earth’s early atmosphere contained mostly

hydrogen, with the oxygen, nitrogen, and carbon atoms chemically

bonded to hydrogen to form water, ammonia, and methane. Most

important, free oxygen could not exist in the presence of such an

abundance of hydrogen.

As early as the mid-1920’s, Aleksandr Ivanovich Oparin, a Russian

biochemist, had argued that the organic compounds necessary

for life had been built up on the early earth by chemical combinations

in a reducing atmosphere. The energy from the Sun would

have been sufficient to drive the reactions to produce life. Haldane

later proposed that the organic compounds would accumulate in

the oceans to produce a “dilute organic soup” and that life might

have arisen by some unknown process from that mixture of organic

compounds.





Primordial Soup in a Bottle



Miller combined the ideas of Oparin and Urey and designed a

simple, but elegant, experiment. He decided to mix the gases presumed

to exist in the early atmosphere (water vapor, hydrogen, ammonia,

and methane) and expose them to an electrical spark to determine

which, if any, organic compounds were formed. To do this,

he constructed a relatively simple system, essentially consisting of

two Pyrex flasks connected by tubing in a roughly circular pattern.

The water and gases in the smaller flask were boiled and the resulting

gas forced through the tubing into a larger flask that contained

tungsten electrodes. As the gases passed the electrodes, an electrical

spark was generated, and from this larger flask the gases and any

other compounds were condensed. The gases were recycled through

the system, whereas the organic compounds were trapped in the

bottom of the system.

Miller was trying to simulate conditions that had prevailed on

the early earth. During the one week of operation, Miller extracted

and analyzed the residue of compounds at the bottom of the system.

The results were truly astounding. He found that numerous organic

compounds had, indeed, been formed in only that one week. As

much as 15 percent of the carbon (originally in the gas methane) had

been combined into organic compounds, and at least 5 percent of

the carbon was incorporated into biochemically important compounds.

The most important compounds produced were some of

the twenty amino acids essential to life on Earth.

The formation of amino acids is significant because they are the

building blocks of proteins. Proteins consist of a specific sequence of

amino acids assembled into a well-defined pattern. Proteins are necessary

for life for two reasons. First, they are important structural

materials used to build the cells of the body. Second, the enzymes

that increase the rate of the multitude of biochemical reactions of life

are also proteins. Miller not only had produced proteins in the laboratory

but also had shown clearly that the precursors of proteins—

the amino acids—were easily formed in a reducing environment

with the appropriate energy.

Perhaps the most important aspect of the experiment was the

ease with which the amino acids were formed. Of all the thousands

of organic compounds that are known to chemists, amino acids

were among those that were formed by this simple experiment. This

strongly implied that one of the first steps in chemical evolution was

not only possible but also highly probable. All that was necessary

for the synthesis of amino acids were the common gases of the solar

system, a reducing environment, and an appropriate energy source,

all of which were present on early Earth.



Consequences



Miller opened an entirely new field of research with his pioneering

experiments. His results showed that much about chemical

evolution could be learned by experimentation in the laboratory.

As a result, Miller and many others soon tried variations on

his original experiment by altering the combination of gases, using

other gases, and trying other types of energy sources. Almost all

the essential amino acids have been produced in these laboratory

experiments.

Miller’s work was based on the presumed composition of the

primordial atmosphere of Earth. The composition of this atmosphere

was calculated on the basis of the abundance of elements

in the universe. If this reasoning is correct, then it is highly likely

that there are many other bodies in the universe that have similar

atmospheres and are near energy sources similar to the Sun.

Moreover, Miller’s experiment strongly suggests that amino acids,

and perhaps life as well, should have formed on other planets.



See also : Artificial hormone; Artificial kidney .



Further Reading :

Synchrocyclotron

The invention: 



A powerful particle accelerator that performed

better than its predecessor, the cyclotron.



The people behind the invention:



Edwin Mattison McMillan (1907-1991), an American physicist

who won the Nobel Prize in Chemistry in 1951

Vladimir Iosifovich Veksler (1907-1966), a Soviet physicist

Ernest Orlando Lawrence (1901-1958), an American physicist

Hans Albrecht Bethe (1906- ), a German American physicist









The First Cyclotron



The synchrocyclotron is a large electromagnetic apparatus designed

to accelerate atomic and subatomic particles at high energies.

Therefore, it falls under the broad class of scientific devices

known as “particle accelerators.” By the early 1920’s, the experimental

work of physicists such as Ernest Rutherford and George

Gamow demanded that an artificial means be developed to generate

streams of atomic and subatomic particles at energies much

greater than those occurring naturally. This requirement led Ernest

Orlando Lawrence to develop the cyclotron, the prototype for most

modern accelerators. The synchrocyclotron was developed in response

to the limitations of the early cyclotron.

In September, 1930, Lawrence announced the basic principles behind

the cyclotron. Ionized—that is, electrically charged—particles

are admitted into the central section of a circular metal drum. Once

inside the drum, the particles are exposed to an electric field alternating

within a constant magnetic field. The combined action of the

electric and magnetic fields accelerates the particles into a circular

path, or orbit. This increases the particles’ energy and orbital radii.

This process continues until the particles reach the desired energy

and velocity and are extracted from the machine for use in experiments

ranging from particle-to-particle collisions to the synthesis of

radioactive elements.

Although Lawrence was interested in the practical applications

of his invention in medicine and biology, the cyclotron also was applied

to a variety of experiments in a subfield of physics called

“high-energy physics.” Among the earliest applications were studies

of the subatomic, or nuclear, structure of matter. The energetic

particles generated by the cyclotron made possible the very type of

experiment that Rutherford and Gamow had attempted earlier.

These experiments, which bombarded lithium targets with streams

of highly energetic accelerated protons, attempted to probe the inner

structure of matter.

Although funding for scientific research on a large scale was

scarce beforeWorldWar II (1939-1945), Lawrence nevertheless conceived

of a 467-centimeter cyclotron that would generate particles

with energies approaching 100 million electronvolts. By the end of

the war, increases in the public and private funding of scientific research

and a demand for higher-energy particles created a situation

in which this plan looked as if it would become reality, were it not

for an inherent limit in the physics of cyclotron operation.





Overcoming the Problem of Mass





In 1937, Hans Albrecht Bethe discovered a severe theoretical limitation

to the energies that could be produced in a cyclotron. Physicist

Albert Einstein’s special theory of relativity had demonstrated

that as any mass particle gains velocity relative to the speed of light,

its mass increases. Bethe showed that this increase in mass would

eventually slow the rotation of each particle. Therefore, as the rotation

of each particle slows and the frequency of the alternating electric

field remains constant, particle velocity will decrease eventually.

This factor set an upper limit on the energies that any cyclotron

could produce.

Edwin Mattison McMillan, a colleague of Lawrence at Berkeley,

proposed a solution to Bethe’s problem in 1945. Simultaneously and

independently, Vladimir Iosifovich Veksler of the Soviet Union proposed

the same solution. They suggested that the frequency of the

alternating electric field be slowed to meet the decreasing rotational

frequencies of the accelerating particles—in essence, “synchroniz-

ing” the electric field with the moving particles. The result was the

synchrocyclotron.

Prior toWorldWar II, Lawrence and his colleagues had obtained

the massive electromagnet for the new 100-million-electronvolt cyclotron.

This 467-centimeter magnet would become the heart of the

new Berkeley synchrocyclotron. After initial tests proved successful,

the Berkeley team decided that it would be reasonable to convert

the cyclotron magnet for use in a new synchrocyclotron. The

apparatus was operational in November of 1946.

These high energies combined with economic factors to make the

synchrocyclotron a major achievement for the Berkeley Radiation

Laboratory. The synchrocyclotron required less voltage to produce

higher energies than the cyclotron because the obstacles cited by

Bethe were virtually nonexistent. In essence, the energies produced

by synchrocyclotrons are limited only by the economics of building

them. These factors led to the planning and construction of other

synchrocyclotrons in the United States and Europe. In 1957, the

Berkeley apparatus was redesigned in order to achieve energies of

720 million electronvolts, at that time the record for cyclotrons of

any kind.





Impact



Previously, scientists had had to rely on natural sources for highly

energetic subatomic and atomic particles with which to experiment.

In the mid-1920’s, the American physicist Robert Andrews Millikan

began his experimental work in cosmic rays, which are one natural

source of energetic particles called “mesons.” Mesons are charged

particles that have a mass more than two hundred times that of the

electron and are therefore of great benefit in high-energy physics experiments.

In February of 1949, McMillan announced the first synthetically

produced mesons using the synchrocyclotron.

McMillan’s theoretical development led not only to the development

of the synchrocyclotron but also to the development of the

electron synchrotron, the proton synchrotron, the microtron, and

the linear accelerator. Both proton and electron synchrotrons have

been used successfully to produce precise beams of muons and pimesons,

or pions (a type of meson).

The increased use of accelerator apparatus ushered in a new era

of physics research, which has become dominated increasingly by

large accelerators and, subsequently, larger teams of scientists and

engineers required to run individual experiments. More sophisticated

machines have generated energies in excess of 2 trillion

electronvolts at the United States’ Fermi National Accelerator Laboratory,

or Fermilab, in Illinois. Part of the huge Tevatron apparatus

at Fermilab, which generates these particles, is a proton synchrotron,

a direct descendant of McMillan and Lawrence’s early

efforts.



See also: Atomic bomb; Cyclotron; Electron microscope;

Field ionmicroscope; Geiger counter; Hydrogen bomb;

Mass spectrograph;Neutrino detector; Scanning tunneling microscope;

Synchrocyclotron



Further Reading :

Supersonic passenger plane

The invention: 



The first commercial airliner that flies passengers at

speeds in excess of the speed of sound.





The people behind the invention:



Sir Archibald Russell (1904- ), a designer with the British

Aircraft Corporation

Pierre Satre (1909- ), technical director at Sud-Aviation

Julian Amery (1919- ), British minister of aviation, 1962-1964

Geoffroy de Cource (1912- ), French minister of aviation,

1962

William T. Coleman, Jr. (1920- ), U.S. secretary of

transportation, 1975-1977









Birth of Supersonic Transportations



On January 21, 1976, the Anglo-French Concorde became the

world’s first supersonic airliner to carry passengers on scheduled

commercial flights. British Airways flew a Concorde from London’s

Heathrow Airport to the Persian Gulf emirate of Bahrain in

three hours and thirty-eight minutes. At about the same time, Air

France flew a Concorde from Paris’s Charles de Gaulle Airport to

Rio de Janeiro, Brazil, in seven hours and twenty-five minutes.

The Concordes’ cruising speeds were about twice the speed of

sound, or 1,350 miles per hour. On May 24, 1976, the United States

and Europe became linked for the first time with commercial supersonic

air transportation. British Airways inaugurated flights

between Dulles International Airport in Washington, D.C., and

Heathrow Airport. Likewise, Air France inaugurated flights between

Dulles International Airport and Charles de Gaulle Airport.

The London-Washington, D.C., flight was flown in an unprecedented

time of three hours and forty minutes. The Paris-

Washington, D.C., flight was flown in a time of three hours and

fifty-five minutes.





The Decision to Build the SST



Events leading to the development and production of the Anglo-

French Concorde went back almost twenty years and included approximately

$3 billion in investment costs. Issues surrounding the

development and final production of the supersonic transport (SST)

were extremely complex and at times highly emotional. The concept

of developing an SST brought with it environmental concerns

and questions, safety issues both in the air and on the ground, political

intrigue of international proportions, and enormous economic

problems from costs of operations, research, and development.

In England, the decision to begin the SST project was made in October,

1956. Under the promotion of Morien Morgan with the Royal

Aircraft Establishment in Farnborough, England, it was decided at

the Aviation Ministry headquarters in London to begin development

of a supersonic aircraft. This decision was based on the intense competition

from the American Boeing 707 and Douglas DC-8 subsonic

jets going into commercial service. There was little point in developing

another subsonic plane; the alternative was to go above the speed

of sound. In November, 1956, at Farnborough, the first meeting of the

Supersonic Transport Aircraft Committee, known as STAC, was held.

Members of the STAC proposed that development costs would be

in the range of $165 million to $260 million, depending on the range,

speed, and payload of the chosen SST. The committee also projected

that by 1970, there would be a world market for at least 150 to 500 supersonic

planes. Estimates were that the supersonic plane would recover

its entire research and development cost through thirty sales.

The British, in order to continue development of an SST, needed a European

partner as a way of sharing the costs and preempting objections

to proposed funding by England’s Treasury.

In 1960, the British government gave the newly organized British

Aircraft Corporation (BAC) $1 million for an SST feasibility study.

Sir Archibald Russell, BAC’s chief supersonic designer, visited Pierre

Satre, the technical director at the French firm of Sud-Aviation.

Satre’s suggestion was to evolve an SST from Sud-Aviation’s highly

successful subsonic Caravelle transport. By September, 1962, an

agreement was reached by Sud and BAC design teams on a new

SST, the Super Caravelle.

There was a bitter battle over the choice of engines with two British

engine firms, Bristol-Siddeley and Rolls-Royce, as contenders.

Sir Arnold Hall, the managing director of Bristol-Siddeley, in collaboration

with the French aero-engine company SNECMA, was eventually

awarded the contract for the engines. The engine chosen was

a “civilianized” version of the Olympus, which Bristol had been developing

for the multirole TRS-2 combat plane.



The Concorde Consortium



On November 29, 1962, the Concorde Consortium was created

by an agreement between England and the French Republic, signed

by Ministers of Aviation Julian Amery and Geoffroy de Cource

(1912- ). The first Concorde, Model 001, rolled out from Sud-

Aviation’s St. Martin-du-Touch assembly plant on December 11,

1968. The second, Model 002, was completed at the British Aircraft

Corporation a few months later. Eight years later, on January 21,

1976, the Concorde became the world’s first supersonic airliner to

carry passengers on scheduled commercial flights.

Development of the SST did not come easily for the Anglo-

French consortium. The nature of supersonic flight created numerous

problems and uncertainties not present for subsonic flight. The

SST traveled faster than the speed of sound. Sound travels at 760

miles per hour at sea level at a temperature of 59 degrees Fahrenheit.

This speed drops to about 660 miles per hour at sixty-five thousand

feet, cruising altitude for the SST, where the air temperature

drops to 70 degrees below zero.

The Concorde was designed to fly at a maximum of 1,450 miles

per hour. The European designers could use an aluminum alloy

construction and stay below the critical skin-friction temperatures

that required other airframe alloys, such as titanium. The Concorde

was designed with a slender curved wing surface. The design incorporated

widely separated engine nacelles, each housing two Olympus

593 jet engines. The Concorde was also designed with a “droop

snoot,” providing three positions: the supersonic configuration, a

heat-visor retracted position for subsonic flight, and a nose-lowered

position for landing patterns.





Impact



Early SST designers were faced with questions such as the intensity

and ionization effect of cosmic rays at flight altitudes of sixty to

seventy thousand feet. The “cascade effect” concerned the intensification

of cosmic radiation when particles from outer space struck a

metallic cover. Scientists looked for ways to shield passengers from

this hazard inside the aluminum or titanium shell of an SST flying

high above the protective blanket of the troposphere. Experts questioned

whether the risk of being struck by meteorites was any

greater for the SST than for subsonic jets and looked for evidence on

wind shear of jet streams in the stratosphere.

Other questions concerned the strength and frequency of clear air

turbulence above forty-five thousand feet, whether the higher ozone

content of the air at SST cruise altitude would affect the materials of

the aircraft, whether SST flights would upset or destroy the protective

nature of the earth’s ozone layer, the effect of aerodynamic heating

on material strength, and the tolerable strength of sonic booms

over populated areas. These and other questions consumed the designers

and researchers involved in developing the Concorde.

Through design research and flight tests, many of the questions

were resolved or realized to be less significant than anticipated. Several

issues did develop into environmental, economic, and international

issues. In late 1975, the British and French governments requested

permission to use the Concorde at New York’s John F.

Kennedy International Airport and at Dulles International Airport

for scheduled flights between the United States and Europe. In December,

1975, as a result of strong opposition from anti-Concorde

environmental groups, the U.S. House of Representatives approved

a six-month ban on SSTs coming into the United States so that the

impact of flights could be studied. Secretary of TransportationWilliam

T. Coleman, Jr., held hearings to prepare for a decision by February

5, 1976, as to whether to allow the Concorde into U.S. airspace.

The British and French, if denied landing rights, threatened

to take the United States to an international court, claiming that

treaties had been violated.

The treaties in question were the Chicago Convention and Bermuda

agreements of February 11, 1946, and March 27, 1946. These

treaties prohibited the United States from banning aircraft that both

France and Great Britain had certified to be safe. The Environmental

Defense Fund contended that the United States had the right to ban

SST aircraft on environmental grounds.

Under pressure from both sides, Coleman decided to allow limited

Concorde service at Dulles and John F. Kennedy airports for a

sixteen-month trial period. Service into John F. Kennedy Airport,

however, was delayed by a ban by the Port Authority of New York

and New Jersey until a pending suit was pursued by the airlines.

During the test period, detailed records were to be kept on the

Concorde’s noise levels, vibration, and engine emission levels. Other

provisions included that the plane would not fly at supersonic

speeds over the continental United States; that all flights could be

cancelled by the United States with four months notice, or immediately

if they proved harmful to the health and safety of Americans;

and that at the end of a year, four months of study would begin to

determine if the trial period should be extended.

The Concorde’s noise was one of the primary issues in determining

whether the plane should be allowed into U.S. airports. The Federal

Aviation Administration measured the effective perceived noise

in decibels. After three months of monitoring the Concorde’s departure

noise at 3.5 nautical miles was found to vary from 105 to 130

decibels. The Concorde’s approach noise at one nautical mile from

threshold varied from 115 to 130 decibels. These readings were approximately

equal to noise levels of other four-engine jets, such as

the Boeing 747, on landing but were twice as loud on takeoff.





The Economics of Operation



Another issue of significance was the economics of Concorde’s

operation and its tremendous investment costs. In 1956, early predictions

of Great Britain’s STAC were for a world market of 150 to

500 supersonic planes. In November, 1976, Great Britain’s Gerald

Kaufman and France’s Marcel Cavaille said that production of the

Concorde would not continue beyond the sixteen vehicles then contracted

for with BAC and Sud-Aviation. There was no demand by

U.S. airline corporations for the plane. Given that the planes could

not fly at supersonic speeds over populated areas because of the

sonic boom phenomenon, markets for the SST had to be separated

by at least three thousand miles, with flight paths over mostly water

or desert. Studies indicated that there were only twelve to fifteen

routes in the world for which the Concorde was suitable. The planes

were expensive, at a price of approximately $74 million each and

had a limited seating capacity of one hundred passengers. The

plane’s range was about four thousand miles.

These statistics compared to a Boeing 747 with a cost of $35 million,

seating capacity of 360, and a range of six thousand miles. In

addition, the International Air Transport Association negotiated

that the fares for the Concorde flights should be equivalent to current

first-class fares plus 20 percent. The marketing promotion for

the Anglo-French Concorde was thus limited to the elite business

traveler who considered speed over cost of transportation. Given

these factors, the recovery of research and development costs for

Great Britain and France would never occur.



See also : Airplane; Bullet train; Dirigible; Rocket; Stealth aircraft;

                 Supersonic transport











Further Reading

Supercomputer

The invention: 



A computer that had the greatest computational
power that then existed.



The person behind the invention: 



Seymour R. Cray (1928-1996), American computer architect and
designer









The Need for Computing Power



Although modern computers have roots in concepts first proposed

in the early nineteenth century, it was only around 1950 that they became

practical. Early computers enabled their users to calculate equations

quickly and precisely, but it soon became clear that even more

powerful computers—machines capable of receiving, computing, and

sending out data with great precision and at the highest speeds—

would enable researchers to use computer “models,” which are programs

that simulate the conditions of complex experiments.

Few computer manufacturers gave much thought to building the

fastest machine possible, because such an undertaking is expensive

and because the business use of computers rarely demands the

greatest processing power. The first company to build computers

specifically to meet scientific and governmental research needs was

Control Data Corporation (CDC). The company had been founded

in 1957 by William Norris, and its young vice president for engineering

was the highly respected computer engineer Seymour R.

Cray. When CDC decided to limit high-performance computer design,

Cray struck out on his own, starting Cray Research in 1972. His

goal was to design the most powerful computer possible. To that

end, he needed to choose the principles by which his machine

would operate; that is, he needed to determine its architecture.





The Fastest Computer



All computers rely upon certain basic elements to process data.

Chief among these elements are the central processing unit, or CPU

(which handles data), memory (where data are stored temporarily

before and after processing), and the bus (the interconnection between

memory and the processor, and the means by which data are

transmitted to or from other devices, such as a disk drive or a monitor).

The structure of early computers was based on ideas developed

by the mathematician John von Neumann, who, in the 1940’s,

conceived a computer architecture in which the CPU controls all

events in a sequence: It fetches data frommemory, performs calculations

on those data, and then stores the results in memory. Because it

functions in sequential fashion, the speed of this “scalar processor”

is limited by the rate at which the processor is able to complete each

cycle of tasks.

Before Cray produced his first supercomputer, other designers

tried different approaches. One alternative was to link a vector processor

to a scalar unit. Avector processor achieves its speed by performing

computations on a large series of numbers (called a vector)

at one time rather than in sequential fashion, though specialized

and complex programs were necessary to make use of this feature.

In fact, vector processing computers spent most of their time operating

as traditional scalar processors and were not always efficient at

switching back and forth between the two processing types.

Another option chosen by Cray’s competitors was the notion of

“pipelining” the processor’s tasks. A scalar processor often must

wait while data are retrieved or stored in memory. Pipelining techniques

allow the processor to make use of idle time for calculations

in other parts of the program being run, thus increasing the effective

speed. A variation on this technique is “parallel processing,” in

which multiple processors are linked. If each of, for example, eight

central processors is given a portion of a computing task to perform,

the task will be completed more quickly than the traditional von

Neumann architecture, with its single processor, would allow.

Ever the pragmatist, however, Cray decided to employ proved

technology rather than use advanced techniques in his first supercomputer,

the Cray 1, which was introduced in 1976. Although the

Cray 1 did incorporate vector processing, Cray used a simple form

of vector calculation that made the technique practical and easy to

use. Most striking about this computer was its shape, which was far

more modern than its internal design. The Cray 1 was shaped like a

cylinder with a small section missing and a hollow center, with

what appeared to be a bench surrounding it. The shape of the machine

was designed to minimize the length of the interconnecting

wires that ran between circuit boards to allow electricity to move the

shortest possible distance. The bench concealed an important part

of the cooling system that kept the system at an appropriate operating

temperature.

The measurements that describe the performance of supercomputers

are called MIPS (millions of instructions per second) for scalar

processors and megaflops (millions of floating-point operations per

second) for vector processors. (Floating-point numbers are numbers

expressed in scientific notation; for example, 1027.) Whereas the fastest

computer before the Cray 1 was capable of some 35 MIPS, the

Cray 1 was capable of 80 MIPS. Moreover, the Cray 1 was theoretically

capable of vector processing at the rate of 160 megaflops, a rate

unheard of at the time.





Consequences



Seymour Cray first estimated that there would be few buyers for

a machine as advanced as the Cray 1, but his estimate turned out to

be incorrect. There were many scientists who wanted to perform

computer modeling (in which scientific ideas are expressed in such

a way that computer-based experiments can be conducted) and

who needed raw processing power.

When dealing with natural phenomena such as the weather or

geological structures, or in rocket design, researchers need to make

calculations involving large amounts of data. Before computers,

advanced experimental modeling was simply not possible, since

even the modest calculations for the development of atomic energy,

for example, consumed days and weeks of scientists’ time.

With the advent of supercomputers, however, large-scale computation

of vast amounts of information became possible. Weather

researchers can design a detailed program that allows them to analyze

complex and seemingly unpredictable weather events such

as hurricanes; geologists searching for oil fields can gather data

about successful finds to help identify new ones; and spacecraft

designers can “describe” in computer terms experimental ideas

that are too costly or too dangerous to carry out. As supercomputer

performance evolves, there is little doubt that scientists will

make ever greater use of its power.





Seymour R. Cray

Seymour R. Cray was born in 1928 in Chippewa Falls, Wisconsin.
The son of a civil engineer, he became interested in radio
and electronics as a boy. After graduating from high school in
1943, he joined the U.S. Army, was posted to Europe in an infantry
communications platoon, and fought in the Battle of the
Bulge. Back from the war, he pursued his interest in electronics
in college while majoring in mathematics at the University of
Minnesota. Upon graduation in 1950, he took a job at Engineering
Research Associates. It was there that he first learned
about computers. In fact, he helped design the first digital computer,
UNIVAC.
Cray co-founded Control Data Corporation in 1957. Based
on his ideas, the company built large-scale, high-speed computers.
In 1972 he founded his own company, Cray Research Incorporated,
with the intention of employing new processing methods
and simplifying architecture and software to build the
world’s fastest computers. He succeeded, and the series of computers
that the company marketed made possible computer
modeling as a central part of scientific research in areas as diverse
as meteorology, oil exploration, and nuclear weapons design.
Through the 1970’s and 1980’s Cray Research was at the
forefront of supercomputer technology, which became one of
the symbols of American technological leadership.
In 1989 Cray left Cray Research to form still another company,
Cray Computer Corporation. He planned to build the
next generation supercomputer, the Cray 5, but advances in microprocessor
technology undercut the demand for supercomputers.
Cray Computer entered bankruptcy in 1995.Ayear later
he died from injuries sustained in an automobile accident near
Colorado Springs, Colorado.



See also :  Apple II computer; BINAC computer; Colossus computer;

ENIAC computer; IBM Model 1401 computer; Personal computer; Seymour R. Cray







Further Reading

Slater, Robert. Portraits in Silicon. Cambridge, Mass.: MIT Press,

1987.











Understanding Supercomputing

Steelmaking process

The invention: 



Known as the basic oxygen, or L-D, process, a

method for producing steel that worked about twelve times

faster than earlier methods.



The people behind the invention:



Henry Bessemer (1813-1898), the English inventor of a process

for making steel from iron



Robert Durrer (1890-1978), a Swiss scientist who first proved

the workability of the oxygen process in a laboratory



F. A. Loosley (1891-1966), head of research and development at

Dofasco Steel in Canada



Theodor Suess (1894-1956), works manager at Voest









Ferrous Metal 



The modern industrial world is built on ferrous metal. Until
1857, ferrous metal meant cast iron and wrought iron, though a few
specialty uses of steel, especially for cutlery and swords, had existed
for centuries. In 1857, Henry Bessemer developed the first largescale
method of making steel, the Bessemer converter. By the 1880’s,
modification of his concepts (particularly the development of a ‘’basic”
process that could handle ores high in phosphor) had made
large-scale production of steel possible.
Bessemer’s invention depended on the use of ordinary air, infused
into the molten metal, to burn off excess carbon. Bessemer himself
had recognized that if it had been possible to use pure oxygen instead
of air, oxidation of the carbon would be far more efficient and rapid.
Pure oxygen was not available in Bessemer’s day, except at very high
prices, so steel producers settled for what was readily available, ordinary
air. In 1929, however, the Linde-Frakl process for separating the
oxygen in air from the other elements was discovered, and for the
first time inexpensive oxygen became available.
Nearly twenty years elapsed before the ready availability of pure
oxygen was applied to refining the method of making steel. The first
experiments were carried out in Switzerland by Robert Durrer. In

1949, he succeeded in making steel expeditiously in a laboratory setting
through the use of a blast of pure oxygen. Switzerland, however,
had no large-scale metallurgical industry, so the Swiss turned
the idea over to the Austrians, who for centuries had exploited the
large deposits of iron ore in a mountain in central Austria. Theodor
Suess, the works manager of the state-owned Austrian steel complex,
Voest, instituted some pilot projects. The results were sufficiently
favorable to induce Voest to authorize construction of production
converters. In 1952, the first ‘’heat” (as a batch of steel is
called) was “blown in,” at the Voest works in Linz. The following
year, another converter was put into production at the works in
Donauwitz. These two initial locations led to the basic oxygen process
sometimes being referred to as the L-D process.





The L-D Process




The basic oxygen, or L-D, process makes use of a converter similar
to the Bessemer converter. Unlike the Bessemer, however, the LD
converter blows pure oxygen into the molten metal from above
through a water-cooled injector known as a lance. The oxygen burns
off the excess carbon rapidly, and the molten metal can then be
poured off into ingots, which can later be reheated and formed into
the ultimately desired shape. The great advantage of the process is
the speed with which a “heat” reaches the desirable metallurgical
composition for steel, with a carbon content between 0.1 percent
and 2 percent. The basic oxygen process requires about forty minutes.
In contrast, the prevailing method of making steel, using an
open-hearth furnace (which transferred the technique from the
closed Bessemer converter to an open-burning furnace to which the
necessary additives could be introduced by hand) requires eight to
eleven hours for a “heat” or batch.
The L-D process was not without its drawbacks, however. It was
adopted by the Austrians because, by carefully calibrating the timing
and amount of oxygen introduced, they could turn their moderately
phosphoric ore into steel without further intervention. The
process required ore of a standardized metallurgical, or chemical,
content, for which the lancing had been calculated. It produced a
large amount of iron-oxide dust that polluted the surrounding at-

mosphere, and it required a lining in the converter of dolomitic
brick. The specific chemical content of the brick contributed to the
chemical mixture that produced the desired result.
The Austrians quickly realized that the process was an improvement.
In May, 1952, the patent specifications for the new process
were turned over to a new company, Brassert Oxygen Technik, or
BOT, which filed patent applications around the world. BOT embarked
on an aggressive marketing campaign, bringing potential
customers to Austria to observe the process in action. Despite BOT’s
efforts, the new process was slow to catch on, even though in 1953
BOT licensed a U.S. firm, Kaiser Engineers, to spread the process in
the United States.
Many factors serve to explain the reluctance of steel producers
around the world to adopt the new process. One of these was the
large investment most major steel producers had in their openhearth
furnaces. Another was uncertainty about the pollution factor.
Later, special pollution-control equipment would be developed
to deal with this problem. A third concern was whether the necessary
refractory liners for the new converters would be available. A
fourth was the fact that the new process could handle a load that
contained no more than 30 percent scrap, preferably less. In practice,
therefore, it would only work where a blast furnace smelting
ore was already set up.
One of the earliest firms to show serious interest in the new technology
was Dofasco, a Canadian steel producer. Between 1952 and
1954, Dofasco, pushed by its head of research and development, F.
A. Loosley, built pilot operations to test the methodology. The results
were sufficiently promising that in 1954 Dofasco built the first
basic oxygen furnace outside Austria. Dofasco had recently built its
own blast furnace, so it had ore available on site. It was able to devise
ways of dealing with the pollution problem, and it found refractory
liners that would work. It became the first North American
producer of basic oxygen steel.
Having bought the licensing rights in 1953, Kaiser Engineers was
looking for a U.S. steel producer adventuresome enough to invest in
the new technology. It found that producer in McLouth Steel, a
small steel plant in Detroit, Michigan. Kaiser Engineers supplied
much of the technical advice that enabled McLouth to build the first

U.S. basic oxygen steel facility, though McLouth also sent one of its
engineers to Europe to observe the Austrian operations. McLouth,
which had backing from General Motors, also made use of technical
descriptions in the literature.





The Specifications Question










One factor that held back adoption of basic oxygen steelmaking
was the question of specifications. Many major engineering projects
came with precise specifications detailing the type of steel to be
used and even the method of its manufacture. Until basic oxygen
steel was recognized as an acceptable form by the engineering fra-

ternity, so that job specifications included it as appropriate in specific
applications, it could not find large-scale markets. It took a
number of years for engineers to modify their specifications so that
basic oxygen steel could be used.
The next major conversion to the new steelmaking process occurred
in Japan. The Japanese had learned of the process early,
while Japanese metallurgical engineers were touring Europe in
1951. Some of them stopped off at the Voest works to look at the pilot
projects there, and they talked with the Swiss inventor, Robert
Durrer. These engineers carried knowledge of the new technique
back to Japan. In 1957 and 1958, Yawata Steel and Nippon Kokan,
the largest and third-largest steel producers in Japan, decided to implement
the basic oxygen process. An important contributor to this
decision was the Ministry of International Trade and Industry, which
brokered a licensing arrangement through Nippon Kokan, which in
turn had signed a one-time payment arrangement with BOT. The
licensing arrangement allowed other producers besides Nippon
Kokan to use the technique in Japan.
The Japanese made two important technical improvements in
the basic oxygen technology. They developed a multiholed lance for
blowing in oxygen, thus dispersing it more effectively in the molten
metal and prolonging the life of the refractory lining of the converter
vessel. They also pioneered the OG process for recovering
some of the gases produced in the converter. This procedure reduced
the pollution generated by the basic oxygen converter.
The first large American steel producer to adopt the basic oxygen
process was Jones and Laughlin, which decided to implement the
new process for several reasons. It had some of the oldest equipment
in the American steel industry, ripe for replacement. It also
had experienced significant technical difficulties at its Aliquippa
plant, difficulties it was unable to solve by modifying its openhearth
procedures. It therefore signed an agreement with Kaiser Engineers
to build some of the new converters for Aliquippa. These
converters were constructed on license from Kaiser Engineers by
Pennsylvania Engineering, with the exception of the lances, which
were imported from Voest in Austria. Subsequent lances, however,
were built in the United States. Some of Jones and Laughlin’s production
managers were sent to Dofasco for training, and technical

advisers were brought to the Aliquippa plant both from Kaiser Engineers
and from Austria.
Other European countries were somewhat slower to adopt the
new process. Amajor cause for the delay was the necessary modification
of the process to fit the high phosphoric ores available in Germany
and France. Europeans also experimented with modifications
of the basic oxygen technique by developing converters that revolved.
These converters, known as Kaldo in Sweden and Rotor in
Germany, proved in the end to have sufficient technical difficulties
that they were abandoned in favor of the standard basic oxygen
converter. The problems they had been designed to solve could be
better dealt with through modifications of the lance and through
adjustments in additives.
By the mid-1980’s, the basic oxygen process had spread throughout
the world. Neither Japan nor the European Community was
producing any steel by the older, open-hearth method. In conjunction
with the electric arc furnace, fed largely on scrap metal, the basic
oxygen process had transformed the steel industry of the world.



Impact




The basic oxygen process has significant advantages over older
procedures. It does not require additional heat, whereas the openhearth
technique calls for the infusion of nine to twelve gallons of
fuel oil to raise the temperature of the metal to the level necessary to
burn off all the excess carbon. The investment cost of the converter
is about half that of an open-hearth furnace. Fewer refractories are
required, less than half those needed in an open-hearth furnace.
Most important of all, however, a “heat” requires less than an hour,
as compared with the eight or more hours needed for a “heat” in an
open-hearth furnace.
There were some disadvantages to the basic oxygen process. Perhaps
the most important was the limited amount of scrap that could
be included in a “heat,” a maximum of 30 percent. Because the process
required at least 70 percent new ore, it could be operated most
effectively only in conjunction with a blast furnace. Counterbalancing
this last factor was the rapid development of the electric arc
furnace, which could operate with 100 percent scrap. Afirm with its

own blast furnace could, with both an oxygen converter and an electric
arc furnace, handle the available raw material.
The advantages of the basic oxygen process overrode the disadvantages.
Some other new technologies combined to produce this
effect. The most important of these was continuous casting. Because
of the short time required for a “heat,” it was possible, if a plant had
two or three converters, to synchronize output with the fill needs of
a continuous caster, thus largely canceling out some of the economic
drawbacks of the batch process. Continuous production, always
more economical, was now possible in the basic steel industry, particularly
after development of computer-controlled rolling mills.
These new technologies forced major changes in the world’s steel
industry. Labor requirements for the basic oxygen converter were
about half those for the open-hearth furnace. The high speed of the
new technology required far less manual labor but much more technical
expertise. Labor requirements were significantly reduced, producing
major social dislocations in steel-producing regions. This effect
was magnified by the fact that demand for steel dropped
sharply in the 1970’s, further reducing the need for steelworkers.
The U.S. steel industry was slower than either the Japanese or the
European to convert to the basic oxygen technique. The U.S. industry
generally operated with larger quantities, and it took a number
of years before the basic oxygen technique was adapted to converters
with an output equivalent to that of the open-hearth furnace. By
the time that had happened, world steel demand had begun to
drop. U.S. companies were less profitable, failing to generate internally
the capital needed for the major investment involved in
abandoning open-hearth furnaces for oxygen converters. Although
union contracts enabled companies to change work assignments
when new technologies were introduced, there was stiff resistance
to reducing employment of steelworkers, most of whom had lived
all their lives in one-industry towns. Finally, engineers at the steel
firms were wedded to the old methods and reluctant to change, as
were the large bureaucracies of the big U.S. steel firms.
The basic oxygen technology in steel is part of a spate of new
technical developments that have revolutionized industrial production,
drastically reducing the role of manual labor and dramatically
increasing the need for highly skilled individuals with technical ex-

pertise. Because capital costs are significantly lower than for alternative
processes, it has allowed a number of developing countries
to enter a heavy industry and compete successfully with the old industrial
giants. It has thus changed the face of the steel industry.







Henry Bessemer

Henry Bessemer was born in the small village of Charlton,
England, in 1813. His father was an early example of a technician,
specializing in steam engines, and operated a business
making metal type for printing presses. The elder Bessemer
wanted his son to attend university, but Henry preferred to
study under his father. During his apprenticeship, he learned
the properties of alloys. At seventeen he moved to London to
open his own business, which fabricated specialty metals.
Three years later the Royal Academy held an exhibition of
Bessemer’s work. His career, well begun, moved from one invention
to another until at his death in 1898 he held 114 patents.
Among them were processes for casting type and producing
graphite for pencils; methods for manufacturing glass, sugar,
bronze powder, and ships; and his best known creation, the Bessemer
converter for making steel from iron. Bessemer built his
first converter in 1855; fifteen years later Great Britain was producing
half of the world’s steel.
Bessemer’s life and career were models of early Industrial
Age industry, prosperity, and longevity. Amillionaire from patent
royalties, he retired at fifty-nine, lived another twenty-six
years, working on yet more inventions and cultivating astronomy
as a hobby, and was married for sixty-four years. Among
his many awards and honors was a knighthood, bestowed by
Queen Victoria.



See also : Assembly line; Buna rubber; Disposable razor; Laminated glass;

 Memory metal; Neoprene; Oil-well drill bit; Steelmaking Wikipedia .







Further Reading :



Restructuring of the Steel Industry in Eight Countries.



Steel Phoenix: The Fall and Rise of the U.S. Steel Industry






Secondary Steelmaking: Principles and Applications

Stealth aircraft

The invention:



The first generation of “radar-invisible” aircraft,
stealth planes were designed to elude enemy radar systems.



The people behind the invention:
Lockhead Corporation, an American research and development firm
Northrop Corporation, an American aerospace firm









Radar



During World War II, two weapons were developed that radically

altered the thinking of the U.S. military-industrial establishment

and the composition of U.S. military forces. These weapons

were the atomic bombs that were dropped on the Japanese cities of

Hiroshima and Nagasaki by U.S. forces and “radio detection and

ranging,” or radar. Radar saved the English during the Battle of Britain,

and it was radar that made it necessary to rethink aircraft design.

With radar, attacking aircraft can be detected hundreds of

miles from their intended targets, which makes it possible for those

aircraft to be intercepted before they can attack. During World

War II, radar, using microwaves, was able to relay the number, distance,

direction, and speed of German aircraft to British fighter interceptors.

This development allowed the fighter pilots of the Royal

Air Force, “the few” who were so highly praised byWinston Churchill,

to shoot down four times as many planes as they lost.

Because of the development of radar, American airplane design

strategy has been to reduce the planes’ cross sections, reduce or

eliminate the use of metal by replacing it with composite materials,

and eliminate the angles that are found on most aircraft control surfaces.

These actions help make aircraft less visible—and in some

cases, almost invisible—to radar. The Lockheed F-117A Nightrider

and the Northrop B-2 Stealth Bomber are the results of these efforts.





 Airborne “Ninjas”



Hidden inside Lockheed Corporation is a research and development

organization that is unique in the corporate world.

This facility has provided the Air Force with the Sidewinder heatseeking

missile; the SR-71, a titanium-skinned aircraft that can fly

at four times the speed of sound; and, most recently, the F-117A

Nightrider. The Nightrider eluded Iraqi radar so effectively during

the 1991 Persian Gulf War that the Iraqis nicknamed it Shaba,

which is an Arabic word that means ghost. In an unusual move

for military projects, the Nightrider was delivered to the Air

Force in 1982, before the plane had been perfected. This was done

so that Air Force pilots could test fly the plane and provide input

that could be used to improve the aircraft before it went into full

production.

The Northrop B-2 Stealth Bomber was the result of a design philosophy

that was completely different from that of the F-117A

Nightrider. The F-117A, for example, has a very angular appearance,

but the angles are all greater than 180 degrees. This configuration

spreads out radar waves rather than allowing them to be concentrated

and sent back to their point of origin. The B-2, however,

stays away from angles entirely, opting for a smooth surface that

also acts to spread out the radar energy. (The B-2 so closely resembles

the YB-49 FlyingWing, which was developed in the late 1940’s,

that it even has the same wingspan.) The surface of the aircraft is

covered with radar-absorbing material and carries its engines and

weapons inside to reduce the radar cross section. There are no vertical

control surfaces, which has the disadvantage of making the aircraft

unstable, so the stabilizing system uses computers to make

small adjustments in the control elements on the trailing edges of

the wings, thus increasing the craft’s stability.

The F-117A Nightrider and the B-2 Stealth Bomber are the “ninjas”

of military aviation. Capable of striking powerfully, rapidly,

and invisibly, these aircraft added a dimension to the U.S. Air Force

that did not exist previously. Before the advent of these aircraft, missions

that required radar-avoidance tactics had to be flown below

the horizon of ground-based radar, which is 30.5 meters above the

ground. Such low-altitude flight is dangerous because of both the

increased difficulty of maneuvering and vulnerability to ground

fire. Additionally, such flying does not conceal the aircraft from the

airborne radar carried by such craft as the American E-3A AWACS

and the former Soviet Mainstay. In a major conflict, the only aircraft

that could effectively penetrate enemy airspace would be the Nightrider

and the B-2.

The purpose of the B-2 was to carry nuclear weapons into hostile

airspace undetected.With the demise of the Soviet Union, mainland

China seemed the only remaining major nuclear threat. For this reason,

many defense experts believed that there was no longer a need

for two radar-invisible planes, and cuts in U.S. military expenditures

threatened the B-2 program during the early 1990’s.



Consequences



The development of the Nightrider and the B-2 meant that the

former Soviet Union would have had to spend at least $60 billion to

upgrade its air defense forces to meet the challenge offered by these

aircraft. This fact, combined with the evolution of the Strategic Defense

Initiative, commonly called “Star Wars,” led to the United

States’ victory in the arms race. Additionally, stealth technology has

found its way onto the conventional battlefield.

As was shown in 1991 during the Desert Storm campaign in Iraq,

targets that have strategic importance are often surrounded by a

network of anti-air missiles and gun emplacements. During the

Desert Storm air war, the F-117A was the only Allied aircraft to be

assigned to targets in Baghdad. Nightriders destroyed more than 47

percent of the strategic areas that were targeted, and every pilot and

plane returned to base unscathed.

Since the world appears to be moving away from superpower

conflicts and toward smaller regional conflicts, stealth aircraft may

come to be used more for surveillance than for air attacks. This is

particularly true because the SR-71, which previously played the

primary role in surveillance, has been retired from service.



See also : Airplane; Cruise missile; Hydrogen bomb; Radar;
Rocket; Stealth aircraft Wikipedia .

Sonar

The invention:



A device that detects soundwaves transmitted

through water, sonar was originally developed to detect enemy

submarines but is also used in navigation, fish location, and

ocean mapping.



The people behind the invention:



Jacques Curie (1855-1941), a French physicist

Pierre Curie (1859-1906), a French physicist

Paul Langévin (1872-1946), a French physicist







Active Sonar, Submarines, and Piezoelectricity



Sonar, which stands for sound navigation and ranging, is the

American name for a device that the British call “asdic.” There are

two types of sonar. Active sonar, the more widely used of the two

types, detects and locates underwater objects when those objects reflect

sound pulses sent out by the sonar. Passive sonar merely listens

for sounds made by underwater objects. Passive sonar is used

mostly when the loud signals produced by active sonar cannot be

used (for example, in submarines).

The invention of active sonar was the result of American, British,

and French efforts, although it is often credited to Paul Langévin,

who built the first working active sonar system by 1917. Langévin’s

original reason for developing sonar was to locate icebergs, but the

horrors of German submarine warfare inWorldWar I led to the new

goal of submarine detection. Both Langévin’s short-range system

and long-range modern sonar depend on the phenomenon of “piezoelectricity,”

which was discovered by Pierre and Jacques Curie in

1880. (Piezoelectricity is electricity that is produced by certain materials,

such as certain crystals, when they are subjected to pressure.)

Since its invention, active sonar has been improved and its capabilities

have been increased. Active sonar systems are used to detect

submarines, to navigate safely, to locate schools of fish, and to map

the oceans.

Sonar Theory, Development, and Use



Although active sonar had been developed by 1917, it was not

available for military use until World War II. An interesting major

use of sonar before that time was measuring the depth of the ocean.

That use began when the 1922 German Meteor Oceanographic Expedition

was equipped with an active sonar system. The system

was to be used to help pay German WorldWar I debts by aiding in

the recovery of gold from wrecked vessels. It was not used successfully

to recover treasure, but the expedition’s use of sonar to determine

ocean depth led to the discovery of the Mid-Atlantic Ridge.

This development revolutionized underwater geology.

Active sonar operates by sending out sound pulses, often called

“pings,” that travel through water and are reflected as echoes when

they strike large objects. Echoes from these targets are received by

the system, amplified, and interpreted. Sound is used instead of

light or radar because its absorption by water is much lower. The

time that passes between ping transmission and the return of an

echo is used to identify the distance of a target from the system by

means of a method called “echo ranging.” The basis for echo ranging

is the normal speed of sound in seawater (5,000 feet per second).

The distance of the target from the radar system is calculated by

means of a simple equation: range = speed of sound × 0.5 elapsed

time. The time is divided in half because it is made up of the time

taken to reach the target and the time taken to return.

The ability of active sonar to show detail increases as the energy

of transmitted sound pulses is raised by decreasing the

sound wavelength. Figuring out active sonar data is complicated

by many factors. These include the roughness of the ocean, which

scatters sound and causes the strength of echoes to vary, making

it hard to estimate the size and identity of a target; the speed of

the sound wave, which changes in accordance with variations in

water temperature, pressure, and saltiness; and noise caused by

waves, sea animals, and ships, which limits the range of active sonar

systems.

Asimple active pulse sonar system produces a piezoelectric signal

of a given frequency and time duration. Then, the signal is amplified

and turned into sound, which enters the water. Any echo that is produced

returns to the system to be amplified and used to determine the identity

and distance of the target.

Most active sonar systems are mounted near surface vessel keels

or on submarine hulls in one of three ways. The first and most popular

mounting method permits vertical rotation and scanning of a

section of the ocean whose center is the system’s location. The second

method, which is most often used in depth sounders, directs

the beam downward in order to measure ocean depth. The third

method, called wide scanning, involves the use of two sonar systems,

one mounted on each side of the vessel, in such a way that the

two beams that are produced scan the whole ocean at right angles to

the direction of the vessel’s movement.

Active single-beam sonar operation applies an alternating voltage

to a piezoelectric crystal, making it part of an underwater loudspeaker

(transducer) that creates a sound beam of a particular frequency.

When an echo returns, the system becomes an underwater

microphone (receiver) that identifies the target and determines its

range. The sound frequency that is used is determined by the sonar’s

purpose and the fact that the absorption of sound by water increases

with frequency. For example, long-range submarine-seeking sonar

systems (whose detection range is about ten miles) operate at 3 to 40

kilohertz. In contrast, short-range systems that work at about 500 feet

(in mine sweepers, for example) use 150 kilohertz to 2 megahertz.



Impact



Modern active sonar has affected military and nonmilitary activities

ranging from submarine location to undersea mapping and

fish location. In all these uses, two very important goals have been

to increase the ability of sonar to identify a target and to increase the

effective range of sonar. Much work related to these two goals has

involved the development of new piezoelectric materials and the replacement

of natural minerals (such as quartz) with synthetic piezoelectric

ceramics.

Efforts have also been made to redesign the organization of sonar

systems. One very useful development has been changing beammaking

transducers from one-beam units to multibeam modules

made of many small piezoelectric elements. Systems that incorporate

these developments have many advantages, particularly the ability

to search simultaneously in many directions. In addition, systems

have been redesigned to be able to scan many echo beams simultaneously

with electronic scanners that feed into a central receiver.

These changes, along with computer-aided tracking and target

classification, have led to the development of greatly improved active

sonar systems. It is expected that sonar systems will become

even more powerful in the future, finding uses that have not yet

been imagined.



Paul Langévin

If he had not published the Special Theory of Relativity in

1905, Albert Einstein once said, Paul Langévin would have

done so not long afterward. Born in Paris in 1872, Langévin was

among the foremost physicists of his generation. He studied in

the best French schools of science—and with such teachers as

Pierre Curie and Jean Perrin—and became a professor of physics

at the College de France in 1904. He moved to the Sorbonne

in 1909.

Langévin’s research was always widely influential. In addition

to his invention of active sonar, he was especially noted for

his studies of the molecular structure of gases, analysis of secondary

X rays from irradiated metals, his theory of magnetism,

and work on piezoelectricity and piezoceramics. His suggestion

that magnetic properties are linked to the valence electrons of atoms

inspired Niels Bohr’s classic model of the atom. In his later

career, a champion of Einstein’s theories of relativity, Langévin

worked on the implications of the space-time continuum.

DuringWorldWar II, Langévin, a pacifist, publicly denounced

the Nazis and their occupation of France. They jailed him for it.

He escaped to Switzerland in 1944, returning as soon as France

was liberated. He died in late 1946.







See also :  Aqualung ; Bathyscaphe ; Bathysphere ; Geiger counter ;

Gyrocompass ; Radar ; Richter scale ;  Paul Langévin .



 Further Reading