Uranium Mining, and Processing

Primary Uranium Minerals
Uraninite	UO2.x
Pitchblende	UO2.x (x = 0.2-0.6)
Coffinite	U(SiO4)1-x(OH)4x
Brannerite	(U, CA, Y, CE)(Ti, Fe)2O6
Davidite	(REE)(Y, U)(Ti, Fe3+)20O38
Thucholite	Thorium- and uranium-bearing organic material

Secondary Uranium Minerals
Autunite	Ca(UO2)2(PO4)2·8-12 H2O
Carnotite	K2(UO2)2(VO4)2·1-3 H2O
Gummite	A mixture of uraninite and secondary uranium minerals of variable composition
Seleeite	Mg(UO2)2(PO4)2·10 H2O
Torbernite	Cu(UO2)2(PO4)2·12 H2O
Tyuyamunite	Ca(UO2)2(VO4)2·5-8 H2O
Uranocircite	Ba(UO2)2(PO4)2·8-10 H2O
Uranophane	Ca(UO2)2(HSiO4)2·5 H2O
Zeunerite	Cu(UO2)2(AsO4)2·8-10 H2O

Conventional Agitation Leach

Uranium is highly soluble as a sulfate in sulfuric acid, and as a carbonate in alkaline solution in the U6+ valence state. If it occurs in the U4+ state it must oxidized before becoming soluble; this is a two-step reaction, with a chemical oxidant first used to oxidize iron, for example, from the ferrous Fe2+to the ferric Fe3+ state, and in turn the oxidized iron causes oxidation of the uranium from U4+ to U6+

The first step in the agitated leaching process is to finely grind the ore (typically to about 300- to 500-micron size) in a water–slurry mixture. The ore slurry is thickened to a higher density (about 50 percent solids), and then forwarded to a series of stirred tanks where the leaching takes place. Acid and oxidants are added—for acid leaching, temperatures of 50°C to 60°C are used, whereas alkaline leaching requires a higher temperature of 90°C to 95°C. The tanks can be at normal atmospheric pressure or pressurized. Acid and a suitable oxidant (e.g., oxygen, hydrogen peroxide, sodium chlorate, or manganese dioxide) is added to oxidize U4+ to U6+. The acid is the lixiviant—or liquid solution—that dissolves the metal in the U6+ sulfate form. 

Alternatively, a mixture of sodium carbonate and sodium bicarbonate can be used if the ore gangue has a high acid consumption. The choice of a carbonate or acid leaching route is based on the consumption of each chemical by the ore matrix or host rock, reagent availability, and environmental and economic considerations. The choice of oxidant is based on many of the same considerations as the choice of lixiviant.

In either acid or alkaline leaching, the ore slurry—with the uranium in solution—requires the separation of the solids from the uranium-containing liquid. This is commonly performed using filters (horizontal belt, pressure, or drum filters) or a series of thickeners or decanters. In both cases, the slurry is washed with acidified water for the acid leach process, or water only in the case of the alkaline leach option, in what is termed countercurrent decantation. The washed solids, now referred to as tailings, are generally neutralized with lime or other alkaline material if acid leaching of the ore was employed to extract the uranium. The tailings are then forwarded to a tailings impoundment facility for storage.

The clear liquid containing the uranium in solution is further purified using a solvent extraction or ion exchange technology. After uranium removal, the solution—known as “raffinate” or “barren solution”—is recycled back to the filters or decantation process. The concentrated, purified uranium solution (referred to as “pregnant solution” or “eluate”) is advanced to a precipitation stage using hydrogen peroxide, magnesium oxide, or sodium hydroxide. The resultant uranium precipitate is then filtered or centrifuged, dried or calcined, and packaged into suitable drums for shipping

Uranium Enrichment

Uranium when mined is in the form of a stable oxide (U3O8) or peroxide. After initial purification to remove impurities, which is done by heating strongly and subsequent agglomeration and crushing, the purified uranium oxide is then reduced in a kiln by hydrogen to form uranium dioxide by the following reaction.

U3O8 + 2H2 → 3UO2 + 2H2O

The reduced oxide of uranium is then reacted with hydrogen fluoride to form uranium tetrafluoride which is further reacted with gaseous fluorine to produce uranium hexafluoride which is then used as a starting input material in an enrichment plant. The reactions by which the above mentioned conversion takes place are given below.

UO2 + 4HF → UF4 + 2H2O

UF4 + F2 → UF6

Enrichment Methods

Gaseous diffusion: Uranium hexafluoride is first heated and converted from a solid to a gas. It is then made to pass through a series of semi-permeable membranes which are a part of compressors and converters. Since the U-235 isotope molecules are lighter than the U-238 isotope molecules, they tend to diffuse faster through the pores of the membranes and hence can be separated. The two streams of gas produced have different U-235 concentrations and hence are separated. Several repetitions of this process are required to obtain concentrations of U-235 isotope in the gas are high enough to the extent that it can be used in a nuclear reactor. [3] The enriched UF6 gas is then allowed to liquefy and subsequently solidify before being transported to a nuclear power plant. This technology contributes to about 27% of the world's enriched uranium.

Gas centrifuge: This method of uranium enrichment also utilizes the difference in mass of the uranium isotopes are an aid in their separation. A gas centrifuge system consists of several cylinders which rotate at high speeds that create a strong centrifugal force within. The U-238 molecules being heavier tend to line the outer wall of the cylinder while the lighter U-235 molecules stay more towards the center. The two streams are separated and the depleted stream is pumped back for further U-235 extraction. This method of enrichment proves to be more energy efficient as compared to the diffusion method by a factor of 50:1 and hence is currently used to produce 50% of the world enriched uranium.

Grades of Enriched Uranium

Different grades of uranium can be produced through enrichment which then has different applications. These are broadly classified under the following categories.

Slightly Enriched Uranium (SEU): This has a concentration of 0.9% to 2% of U-235 isotope and is most commonly used as a substitute to natural uranium in heavy water reactors. One benefit of using this instead of natural uranium is that lesser quantity of fuel is required to produce the same amount of energy and as a result, the amount of nuclear waste to manage at the end of the production is significantly reduced.

Low Enriched Uranium (LEU): This has a concentration lower than 20% of U-235 isotope. It is commonly used in light water reactors and research reactors.

Highly Enriched Uranium (HEU): This has a concentration higher than 20% of U-235 isotope. When the concentration is over 80%, it is termed as weapons grade uranium which is necessary for a nuclear chain reaction to occur. Highly Enriched Uranium with concentrations greater than 40% is used in naval reactors in powering submarines and in fast neutron reactors.

Nuclear power reactors

The vast majority of all nuclear power reactors require 'enriched' uranium fuel in which the proportion of the uranium-235 isotope has been raised from the natural level of 0.7% to about 3.5% to 5%.  The enrichment process needs to have the uranium in gaseous form, so on the way from the mine it goes through a conversion plant which turns the uranium oxide into uranium hexafluoride.

About 27 tonnes of fresh fuel is required each year by a 1000 MWe nuclear reactor.

Uranium Oxide.

 The most common forms of uranium oxide are U3O8 and UO2. Both oxide forms are solids that have a low solubility in water and are relatively stable over a wide range of environmental conditions. U3O8 is the most stable form of uranium and is the form found in nature. The most common form of U3O8 is “yellow cake,” a solid named for its characteristic color that is produced during the uranium mining and milling process. UO2 is a solid ceramic material and is the form in which uranium is most commonly used as a nuclear reactor fuel.  At ambient temperatures, UO2 will gradually convert to U3O8.  Uranium oxides are extremely stable in the environment and are thus generally considered the preferred chemical form for storage or disposal.

 Isotope Separation

 Natural uranium is a mixture of 0.711% 235U and 92.89% of 238U. The enrichment process enriches the 235U content in natural uranium to the desired percentage. Low-enriched uranium which is typically used in nuclear reactors has 3-4% percent of 235U, while the highly enriched uranium has more than 50% of 235U and is typically used in nuclear weapons.

 Uranium is made from uraninite, which is a mixture of UO2, UO3, oxides of lead, thorium and rare earth elements. Uraninite is calcined to evaporate some impurities, then agglomerated and crushed. U3O8 is then put in a kiln with hydrogen:

 U3O8 + 2H2 =⇒ 3UO2 + 2H2O,                  Heat = −109kJ/mole       (1)

UO3 + H2 =⇒ UO2 + H2O                              Heat = −109kJ/mole       (2)

 The uranium dioxide is then treated with hydrogen fluoride in another kiln.

 UO2 + 4HF =⇒ UF4 + 2H2O,                        Heat = −176kJ/mole       (3)

 Finally the tetrafluoride is fed into a fluidized bed reactor with fluorine to produce the uranium hexafluoride (238UF6, 235 UF6) that is used in the separation process.

 UF4 + F2 =⇒ UF6                                                                                             (4)

 After the separation of molecules the UF6 is vaporized in autoclaves with steam and reacted with hydrogen at 700°C:

UF6 + 2H2O + H2 =⇒ U3O8 + 6HF                                                              (5)

 The final product is the so-called yellow cake, which is the basic raw material for nuclear fuel fabrication.

 Uranium hexafluoride is used because it has great storage properties. It can be used as a solid, liquid or gas, with minimum variations in pressure or temperature. It is usually stored as a solid, when in use it can be turned into liquid which is ideal for pumping. For the actual separation process it is used as a gas.

Uranium Hexafluoride.

 UF6  is the chemical form of uranium that is used during the uranium enrichment process. Within a reasonable range of temperature and pressure, it can be a solid, liquid, or gas. Solid UF6 is a white, dense, crystalline material that resembles rock salt.  UF6 does not react with oxygen, nitrogen, carbon dioxide, or dry air, but it does react with water or water vapor (including humidity in the air). When UF6 comes into contact with water, such as water vapor in the air, the UF6 and water react, forming corrosive hydrogen fluoride (HF) and a uranium-fluoride compound called uranyl fluoride (UO2F2). For this reason, UF6 is always handled in leak-tight containers and processing equipment. Although very convenient for processing, UF6 is not considered a preferred form for long-term storage or disposal because of its relative instability.

Enrichment processes require uranium to be in a gaseous form at relatively low temperature, hence uranium oxide from the mine is converted to uranium hexafluoride in a preliminary process, at a separate conversion plant.

Enriched UF₆ is transported to a fuel fabrication plant where it is converted to uranium dioxide powder. This powder is then pressed to form small fuel pellets, which are then heated to make a hard ceramic material. The pellets are then inserted into thin tubes to form fuel rods. These fuel rods are then grouped together to form fuel assemblies, which are several meters long. 

The number of fuel rods used to make each fuel assembly depends on the type of reactor. A pressurized water reactor may use between 121-193 fuel assemblies, each consisting of between 179-264 fuel rods.

There are currently two generic commercial methods employed internationally for enrichment: gaseous diffusion (referred to as first generation) and gas centrifuge (second generation), which consumes only 2% to 2.5%^[9] as much energy as gaseous diffusion, with centrifuges being at least a "factor of 20" more efficient.

The gas centrifuge process uses a large number of rotating cylinders in series and parallel formations. Each cylinder's rotation creates a strong centripetal force so that the heavier gas molecules containing ²³⁸U move tangentially toward the outside of the cylinder and the lighter gas molecules rich in ²³⁵U collect closer to the center.

Today, 5% U-235 is the maximum level of enrichment for fuel used in normal power reactors. 

Uranium Metal.

 Uranium metal is heavy, silvery white, malleable, ductile, and softer than steel. It is one of the densest materials known (19 g/cm3), being 1.6 times more dense than lead. Uranium metal is not as stable as U3O8 or UO2 because it is subject to surface oxidation. It tarnishes in air, with the oxide film preventing further oxidation of bulk metal at room temperature. Water attacks uranium metal slowly at room temperature and rapidly at higher temperatures. Uranium metal powder or chips will ignite spontaneously in air at ambient temperature.

History of Cell Biology

During the 17th Century

· 1665 Robert Hooke had successfully invented the microscope. Because of this discovery, Robert Hooke was the first one to have a close look of a cell appears to be. His description of these cells was published in Micrographia. However, the cell walls observed by Hooke gave no indication of the nucleus and other organelles found in most living cells.

· 1674  A live cell was observed by Anton van Leeuwenhoek, the very first successful effort to do such.

 
During the 18th Century

· There were not much discovery in the field of Cell Biology during this time. It took another hundred years after those first cell observations for the ubiquitous nature of cells to be fully recognized.

During the 19th Century

·1825 French scientist Francoise Raspail established one of the concepts of cell theory: that all cells arise from pre-existing cells. The basis of this was the witnessing of binary fission under a microscope wherein a single cell divided into two daughter cells.

·1836 Theodore Schwann and Matthias Scleiden proposed the cell theory in 1836. The concept of the theory holds that: (1) The cell is the unit of structure, physiology, and organization in living things, (2) The cell retains a dual existence as a distinct entity and a building block in the construction of organisms, (3) Cells form by free-cell formation, similar to the formation of crystals (spontaneous generation).

·1855 The third doctrine of Schwann and Scleiden was proven wrong by Rudolf Virchow. In this year, he formally enunciated in his powerful dictum that, “Omnis cellula e cellula“, which is translated as “All cells only arise from pre-existing cells“.

· In the middle of the 19th century, Scientists had accepted the fact that it was simply not possible to view cell structures which measure less than a half of a micrometer with the use of a microscope. But because of the development of the cathode ray tube, they’ve later discovered that aside from using light, electrons can be used to view these structures.

20th Century up to the present

·        1919 Phoebus Levene, a Russian physician and chemist, first discovered the order of the three major components of a single nucleotide (phosphate, pentose sugar, and nitrogenous base). He was also the first to discover the carbohydrate component of RNA (ribose), and carbohydrate component of DNA (deoxyribose). Years later, Levene finally identified how DNA and RNA molecules are put together

·1933 The first prototype of the electron microscope was constructed. It is a type of microscope which utilizes a beam of electrons to create an image of the specimen.

·1943 A scientist named Erwin Chargaff began to challenge Levene’s previous conclusions. In 1950, he noted that the nucleotide composition of DNAdiffers among species and do not repeat in the same order reached two major conclusions.

· Chargaff concluded that almost all DNA, no matter what organism or tissue type it comes from, still maintains certain properties, even as its composition varies. He postulated the “Chargaff’s Rule” which says that the amount of cytosine is equal to the amount of guanine, and the amount of thymine is equal to the amount of adenine. In short, the total amount of pyrimidines (thymine and cytosine) approximates the amount of purines (adenine and guanine).

·1951 Meanwhile in the field of cytology, George Grey has successfully made the first continuous cell line to be cultured. The cell line was derived from the cervical cancer cells of Henrietta Lacks, thus these cells were referred to as HeLa cells. These cells played a significant role in the course of cell biology.

·1953 James Watson and Francis Crick derived the three-dimensional and double helical model of the DNA (Pray 2009). After that, the process of replicating the DNA was discovered.

·1961 The endeavor of cracking the genetic code started.
As with the rapid growth of molecular biology in the mid-20th century, cell biology research exploded. It became possible to maintain, grow, and manipulate cells outside of living organisms. The minimal media requirements for cells were characterized years later. Sterile cell culture techniques were further developed.

·  Further advances in electron microscopy greatly facilitated the development of transfection methods. The process of genetic engineering, or the act of modifying an organism’s genetic material either by adding genes or deleting some parts of it, was declared as a separate field in the 1970s.

·1970 Reverse transcriptase in retroviruses was first discovered.

·1977 Frederick Sanger introduced the process of DNA sequencing. The first ever organism to have its genome sequence is a bacteriophage.

·1980 The Polymerase Chain Reaction, a method used to amplify a copy of a segment of a DNA was inverted by Kary Mullis .

1998 Hamilton and Baulcombe discovered the siRNA as part of post-transcriptional gene silencing in plants.

Solar Energy

Our sun is a natural nuclear reactor. It releases tiny packets of energy called photons, which travel the 93 million miles from the sun to Earth in about 8.5 minutes. Solar energy is the technology used to harness the sun's energy and make it useable. A solar cell is a device that converts light directly into electricity using the photoelectric effect.

When photons hit a solar cell, they knock electrons loose from their atoms. If conductors are attached to the positive and negative sides of a cell, it forms an electrical circuit. When electrons flow through such a circuit, they generate electricity. Multiple cells make up a solar panel, and multiple panels (modules) can be wired together to form a solar array. The more panels you can deploy, the more energy you can expect to generate.

Photovoltaic (PV) solar panels are made up of many solar cells. Solar cells are made of silicon, like semiconductors. They are constructed with a positive layer and a negative layer, which together create an electric field, just like in a battery. PV solar panels generate direct current (DC) electricity. With DC electricity, electrons flow in one direction around a circuit.

In traditional solar modules (polycrystalline and monocrystalline), silicon wafers are impregnated with impurities to create a semiconductor that converts sunlight into electric current. Electrical contacts are then created to join one solar cell to another. As silicon reflects, an anti-reflective coating is placed on top of the silicon wafers, usually titanium dioxide or silicon oxide.

The solar cells are laid between a superstrate layer on the top and a backsheet layer on the bottom. The superstrate is usually glass, and the backsheet is plastic. This is then placed inside an aluminium frame to create a finished solar panel.

A solar inverter takes the DC electricity from the solar array and uses that to create AC electricity. Inverters are like the brains of the system. Along with inverting DC to AC power, they also provide ground fault protection and system stats, including voltage and current on AC and DC circuits, energy production and maximum power point tracking.

 How a home solar energy installation works? First, sunlight hits a solar panel on the roof. The panels convert the energy to DC current, which flows to an inverter. The inverter converts the electricity from DC to AC, which you can then use to power your home. It’s beautifully simple and clean, and it’s getting more efficient and affordable all the time.

The history of Science and technology

The development of Science and technology is as old as mankind. Many ‘inventions’ claimed after the 11th century in fact dated back to the Greeks and Chinese many centuries before. Scientific information proposed by the Greek philosopher Aristotle (384 – 322 BC) and others was lost in the Dark Ages in Britain and Europe after the collapse of the Roman Empire.

The birth of technology (2 million years BC)

Tools

The birth of ‘technology’ was when the first human-like species, Homo habilis (‘skilful person’ 2.6 million years BC) made sharp cutting edges from stone. Later, Homo neanderthalis or cave men (200 000 – 30 000 years BC) used tools and weapons and were the very successful ancestors of Homo sapiens, the species we recognise as our ancestors today.

Metals

 Lead (Pb), one of the softest metals, was being extracted from rock in 6500 BC in Anatolia (now Turkey) followed by copper (Cu) three thousand years later in Mesopotamia. The Iron Age was built on a hard, strong and versatile metal, iron (Fe).

 The wheel

Around 4500 BC the wheel and axle combination became the most important invention of all time. Carts came into common use. By 2000 BC wheels had spokes, and then rapid development occurred with waterwheels and windmills to provide power.

New inventions (9th – 18th century)

 Arab alchemy

Turning common metals into precious metals, proved to be a dead end around the 9th century AD. Nevertheless, Arabs were clever chemists and discovered many chemicals that we use today. Gunpowder

The recipe for making gunpowder appeared in a book in Europe in 1242. Roger Bacon (1214 – 1294), an English  friar and philosopher, was the first to describe its formula. Guns soon followed.

 Printing

Spreading knowledge and information was a very slow process before the invention of typography. Johannes Gutenberg (1398 – 1468) developed the first mechanical printing machine in the 1440s. The first printed book was the Bible in 1456 with a run of 150 copies. Each Bible previously took three years to make by hand.

The telescope

 The telescope was invented by Dutchman Hans Lippershey (1570 – 1619). In 1610, using his improved design, Galileo Galilei (1564 - 1642) was able to prove that the Earth revolved around the Sun. This confirmed the ideas of the Polish astronomer Nicolaus Copernicus (1473 – 1543) but it angered the Catholic Church who had adopted the idea that the Earth was at the centre of everything.

The microscope

 Looking at small things became possible when a Dutch maker of spectacles, Hans Janssen and his son, put glass lenses together in 1590 to make a primitive microscope. Anton van Leeuwenhoek (1632 – 1723) took this invention a step further in 1676 with a magnification of 270 times and discovered tiny single-celled creatures in pond water. Ultimately, this helped our understanding of microorganisms and disease.

Lightning conductor

 In 1752, Benjamin Franklin (1706 –1790), the American statesman, philosopher and scientist proved that lightning was a form of electricity when he flew a kite in a thunderstorm. Around 1754, Franklin and the Czech scientist, Prokop Diviš (1698 - 1765) independently developed the lighting conductor to protect buildings from being hit and damaged by lighting. and scientist proved that lightning was a form of electricity when he flew a kite in a thunderstorm. Around 1754, Franklin and the Czech scientist, Prokop Diviš (1698 - 1765) independently developed the lighting conductor to protect buildings from being hit and damaged by lighting.

The first Industrial Revolution (1760 – 1840)

Steam power This era saw the development of steam engines to power factory machinery. Heating water in a boiler to make steam to power a vehicle was a major technological advance. James Watt (1736 – 1819) is recognised as the inventor of the steam engine in 1765. Water could be pumped out of mines and industrial processes speeded up. George Stephenson’s (1781 - 1848) Rocket was the first locomotive to pull heavy loads a long distance. This led to the rapid expansion of railways throughout Britain and the world. The combination of iron and steam paved the way for the great Victorian engineering projects of Isambard Kingdom Brunel (1806 - 1859). He designed bridges, tunnels, viaducts and ships.

Photography

In 1826, after years of experiments, the French inventor Joseph Nicéphore Niépce (1765 - 1833), using ‘bitumen of Judea’ spread on a pewter plate and an exposure of eight hours in bright sunlight, produced the first permanent picture. His technique was improved upon by his colleague Louis Daguerre (1787 - 1851) by using compounds of silver, the basis of modern photography.

The second Industrial Revolution (19th century – 1945)

The electric light

 After many refinements, Thomas Edison’s (1847 – 1931) electric light bulbs were the best and by 1879 they would last for hundreds of hours, much longer than any of their rivals. They were also cheap. To sell bulbs, energy was needed, so Edison’s Electric Illumination Company built their own power station in New York. After many decades he successfully persuaded the public to opt for clean, convenient electric light rather than gas lights.

The telephone

 This is an invention that made money. Alexander Graham Bell (1847 – 1922) was the first in the race to patent a machine in 1876 that you could use to talk to someone on the other side of the world. Admittedly, it was initially from one room to another. The message was “Mr. Watson, come here, I want you”. A year later in 1877 he set up his company and demonstrated long distance calls.

The motor car

 Until the 1860s all prototype motor cars were steam driven. German inventor Nicolas Otto (1832 - 1891) created an improved internal combustion engine in 1876 and this is still the way cars work today. In 1885, the first car, the Benz Patent Motorwagen, was developed by Karl Benz (1844 - 1929). It was a long time before cars became common. Petrol, a cleaning fluid, was only available from the chemist. Famous names such as Rolls Royce and Henry Ford developed the technology; Rolls Royce for the rich and Henry Ford for the man in the street.

The movies

It has been only just over one hundred years since the first movie, or film, was shown by the brothers Auguste and Louis Lumière (1862 - 1954 and 1864 - 1948) in 1895 at the Grand Café in Paris. The terrifying film was entitled The Arrival of a Train at Ciotat Station. Surprisingly, the brothers decided that films didn’t have much of a future and went back to photography. In 1889, George Eastman (1854 - 1932) pioneered celluloid film with holes punched in the side so that the movie camera could show the film precisely frame by frame.

X-rays

Science is impressive when something is discovered that cannot be seen. German physicist Wilhelm Rontgen (1845 – 1923) working with electrical discharges in glass tubes noticed in 1895 that there was a faint glow on a nearby screen. These rays were invisible and could pass through most materials. He also recorded them on photographic paper and thus the first X-ray image was developed. He quickly realised the medical potential of his discovery. Henri Becquerel (1852 – 1908) discovered radioactivity in 1896 while trying to find more out about X-rays. Marie Curie (1867 – 1934), a Polish born French chemist and physicist and two times Nobel Prize winner, is best remembered for her research into radioactivity and new radioactive elements.

Communications

 Radio waves travel in all directions at an incredible 300 000 km per second. The German physicist Heinrich Hertz (1857 – 1854) was the first to prove they existed but it was Guglielmo Marconi (1874 – 1937) who set up the world’s first radio stations to transmit and receive Morse code. In 1896, he sent the first message across the Atlantic from Cornwall to Newfoundland. He was awarded the Nobel Prize for Physics in 1909. It was not until 1915 that engineers were able to transmit sound effectively. The first clear television pictures to be transmitted were sent by Scottish-born John Logie Baird (1888 – 1946). He founded the Baird Television Company Limited and worked on programmes for the BBC (British Broadcasting Corporation).

Flight

At the turn of the century, in 1903, two bicycle repairmen from Ohio, Wilbur and Orville Wright (1867 – 1912 and 1871 – 1948) built and flew the first really successful aeroplane near Kitty Hawk, North Carolina. From that time progress was rapid and the military advantages of flight were realised in WWI.

Rockets and space flights

 The earliest rockets were used in China in the 11th century but by the 19th century speed and accuracy were much improved. Knowledge of astronomy meant that scientists knew the relative movements of the planets in relation to the Earth. A Russian mathematics teacher, Konstantin Tsiolkovsky (1857 – 1935), was the first person to draw up plans for space stations and air locks to allow space walks. He correctly calculated that a rocket would have to travel at 8 km per second to leave the atmosphere and that liquid rocket fuel would be essential. American scientist Robert Goddard (1882 – 1945) not knowing of Tsiolkovsky’s ideas independently developed liquid fuelled rockets from 1926. Ultimately, NASA took up the challenge but the Russians eventually won the race to put a man into orbit. Yuri Gagarin (1934 – 1968) orbited the earth in 1961. In the US, NASA scientists redressed the balance in the space race with their moon landing in 1969.

The atomic bomb

Science and technological advances can be seen as good or bad. The invention of gunpowder must have seemed like that. In 1932, physicists John Cockcroft (1897 – 1967) and Earnest Walton (1903 – 1995) did the impossible. They split the atom. They proved Albert Einstein’s (1879 – 1955) theory of relativity (E=mc²) and unlocked the secrets of the atomic nucleus. Splitting the atom was a brilliant scientific achievement. However, having that knowledge allowed scientists to develop the atomic bomb. The use of an atomic bomb on Hiroshima and Nagasaki in Japan to end the WWII in 1945 was a political decision that was highly controversial. We now know that there is no turning back once scientific and technological discoveries have been made.

The third Scientific‑Technical Revolution (1945 - )

After the WWII new discoveries and advances in science and technology came thick and fast. Plastics were developed for the first time. In 1949, the first practical programmed electronic computer ran mathematical problems. It fitted into one room! In the 1960s, the electronic silicon chip was invented; computers became smaller and more powerful. In 1984, the CD was born and the digital revolution began. The worldwide web has given us access to billions of documents with information and images as well as online shopping and banking. Mobile telephone technology means we have instant contact with friends and family. During this period, there have also been huge advances in genetics since the discovery of the structure of DNA in 1953. Today, Biotechnology and genetic engineering show fast growth trends and, also, are big business. It is interesting to wonder what next? Maybe space is the final frontier, as suggested in Star Trek!

Radio communication

Marconi had born in Italy in 1874. He was privately educated. During his early years Marconi had an interest in science and electricity. At the age of 18, Marconi became a neighbor of university of Bologna physicist Aigusto Righi who had done research on Heinrich Herd’s work. Righi permitted Marconi to attend lectures at the university and also use the university laboratory and library.

In the early1890s, he began working on the idea of wireless telegraphy and began to conduct experiments on radio waves; Building much of his own equipment in the attic of his home. As no encouragement was coming from Italy government, he went to England with his mother and met the chief engineer of post office London. In 1896 his inventions of “wireless telegraphy “were demonstrated at Royal society London.

·         1897- Marconi transmitted Morse code signal over a distance of six Kms. He established a Marconi company. Wireless telegraphy was born.

·         1898- The wireless signal was transmitted on a 12 miles distance.

·         1901- He established a wireless transmission station, at Wexford, to link England and Ireland.

·         This signal was also received in Canada, where he used 150m high antenna for signal detection. The distance covered was 3500 Km. for this; the transmission wavelength used was nearly 350m (850kHzs). It was observed that during night, the signal reached farther and farther but in day time it was reduces to half the distance about 1100Kms.

·         1902- The signal crossed Atlantic.

·         1904- A commercial service was established to transmit night news summaries to ships.

·         1907- A regular Trans Atlantic radio telegraph service was begun.

·        1909-  Marconi shared Nobel Prize in physics for his radio work.

·         The company struggled to provide reliable communication to others. Long after it was apparent that the future of radio communication lay with continuous wave transmissions.

·         1915- After the introduction of the oscillating vacuum tube (valve), the first radio broad-casting began in 1920.

·         1922- Regular entertainment broadcasting service commissioned for BBC.

              

      Wireless communication

        Marconi was born into the Italian nobility as Guglielmo Giovanni Maria Marconi in Bologna on 25 April 1874,his mother being from Ireland.he was educated privately. During his early years, Marconi had an interest in science and electricity and in the early 1890s he began working on the idea of "wireless telegraphy",A relatively new development came from Heinrich Hertz, who in 1888 demonstrated that one could produce and detect electromagnetic radiation, generally referred to as radio waves.

Marconi, then twenty years old, began to conduct experiments in radio waves, building much of his own equipment in the attic of his home at the Villa Griffone in Pontecchio (now an administrative subdivision of Sasso Marconi), Italy with the help of his butler Mignani. In the summer of 1894, he built a storm alarm made up of a battery, a coherer, and an electric bell, which went off when it picked up the radio waves generated by lightning. He continued to work in the attic. Late one night in December 1894 he demonstrated a radio transmitter and receiver to his mother, a set-up that made a bell ring on the other side of the room by pushing a telegraphic button on a bench.. In 1895 he succeeded in sending wireless signals over a distance of one and half mile.

Finding little interest or appreciation for his work in Italy, Marconi travelled to London in early 1896 at the age of 21, accompanied by his mother, to seek support for his work.  While there, Marconi gained the interest and support of William Preece, the Chief Electrical Engineer of the British Post. Marconi made his first demonstration of his system for the British government in July 1896. A further series of demonstrations for the British followed—by March 1897, Marconi had transmitted Morse code signals over a distance of about 6 kilometres  across Salisbury PlainOffice. On 13 May 1897, Marconi sent the world's first ever wireless communication over open sea. The experiment, based in Wales, witnessed a message transversed over the Bristol Channel from Flat Holm Island to Lavernock Point in Penarth, a distance of 6 kilometres. The message read "Are you ready". The transmitting equipment was almost immediately relocated to Brean Down Fort on the Somerset coast, stretching the range to 16 kilometres . Impressed by these and other demonstrations, Preece introduced Marconi's ongoing work to the general public at two important London lectures: "Telegraphy without Wires", at the Toynbee Hall on 11 December 1896; and "Signaling through Space without Wires", given to the Royal Institution on 4 June 1897. In 1897 Marconi wireless Telegraph Company born.

 In December 1898, the British lightship service authorized the establishment of wireless communication between the South Foreland lighthouse at Doverand the East Goodwin lightship, twelve miles distant. On 17 March 1899 the East Goodwin lightship sent a signal on behalf of the merchant vessel Elbewhich had run aground on Goodwin Sands. The message was received by the radio operator of the South Foreland lighthouse, who summoned the aid of the Ramsgate lifeboat. In 1899 he established wireless communication between France and England across the English Channel. He was awarded a patent no 7777 for his "tuned or syntonic telegraphy".

 Marconi began investigating the means to signal completely across the Atlantic in order to compete with the transatlantic telegraph cables. Marconi established a wireless transmitting station at Marconi House, Rosslare Strand, Co. Wexford in 1901 to act as a link between Poldhu in Cornwall, England and Clifden in Co. Galway, Ireland. He soon made the announcement that the message was received at Signal Hill in St John's, Newfoundland (now part of Canada) on 12 December 1901, using a 500-foot (150 m) kite-supported antenna for reception—signals transmitted by the company's new high-power station at Poldhu, Cornwall. The distance between the two points was about 2,200 miles (3,500 km). The exact wavelength used is not known, but it is fairly reliably determined to have been in the neighbourhood of 350 meters (frequency ≈850 kHz). 

Marconi prepared a better organized and documented test. In February 1902, the SS Philadelphia sailed west from Great Britain with Marconi aboard, carefully recording signals sent daily from the Poldhu station. The test results produced coherer-tape reception up to 1,550 miles (2,490 km), and audio reception up to 2,100 miles (3,400 km). The maximum distances were achieved at night, and these tests were the first to show that radio signals for medium wave and longwave transmissions travel much farther at night than in the day. During the daytime, signals had been received up to only about 700 miles (1,100 km), less than half of the distance claimed earlier at Newfoundland, where the transmissions had also taken place during the day.

On 17 December 1902, a transmission from the Marconi station in Glace Bay, Nova Scotia, Canada became the world's first radio message to cross the Atlantic from North America. In 1901, Marconi built a station near South Wellfleet, Massachusetts that sent a message of greetings on 18 January 1903 from United States President Theodore Roosevelt to King Edward VII of the United Kingdom. However, consistent transatlantic signalling was difficult to establish.

In 1904, a commercial service was established to transmit nightly news summaries to subscribing ships, which could incorporate them into their on-board newspapers. A regular transatlantic radio-telegraph service was finally begun on 17 October 1907 between Clifden, Ireland and Glace Bay, but even after this the company struggled for many years to provide reliable communication to others.

Over the years, the Marconi companies gained a reputation for being technically conservative, in particular by continuing to use inefficient spark-transmitter technology, which could be used only for radio-telegraph operations, long after it was apparent that the future of radio communication lay with continuous-wave transmissions which were more efficient and could be used for audio transmissions. Somewhat belatedly, the company did begin significant work with continuous-wave equipment beginning in 1915, after the introduction of the oscillating vacuum tube (valve). The New Street Works factory in Chelmsford was the location for the first entertainment radio broadcasts in the United Kingdom in 1920, employing a vacuum tube transmitter and featuring Dame Nellie Melba. In 1922, regular entertainment broadcasts commenced from the Marconi Research Centre at Great Baddow, forming the prelude to the BBC, and he spoke of the close association of aviation and wireless telephony in that same year at a private gathering with Florence Tyzack Parbury, and even spoke of interplanetary wireless communication.

Born in Bologna, Italy, in 1874, Guglielmo Marconi was a Nobel Prize-winning physicist and inventor credited with the groundbreaking work necessary for all future radio technology. Through his experiments in wireless telegraphy, Marconi developed the first effective system of radio communication.

In 1914, Marconi was made a Senator in the Italian Senate and appointed Honorary Knight Grand Cross of the Royal Victorian Orderin the UK. During World War I, Italy joined the Allied side of the conflict, and Marconi was placed in charge of the Italian military's radio service. He attained the rank of lieutenant in the Italian Army and of commander in the Italian Navy. In 1929, he was made a marquess by King Victor Emmanuel III.

Italian inventor and engineer Guglielmo Marconi (1874-1937) developed, demonstrated and marketed the first successful long-distance wireless telegraph and in 1901 broadcast the first transatlantic radio signal. His company’s Marconi radios ended the isolation of ocean travel and saved hundreds of lives, including all of the surviving passengers from the sinking Titanic. In 1909 he shared the Nobel Prize in Physics for his radio work.

Goodbye to Sparks

By the late 1920s most radio transmitters were using vacuum tubes rather than sparks to generate radio waves. And then the vacuum tubes were abandoned in favor of transistors.

Scientists and engineers have continued to innovate quickly in the field of radio technology. Radio, television, satellite communications, mobile phones, radar, and many other inventions and gadgets have made Hertz’s discovery an indispensable part of modern life.

Crystal detectors.

A natural mineral crystal forms the semiconductor side of the junction. The most common crystal used was galena (PbS, lead sulfide), a naturally occurring ore of lead, although many other minerals were also used including silicon, iron pyrite, molybdenite and carborundum.[3] Galena is a semiconductor with a small bandgap of about 0.4 eV and is used without treatment directly as it is mined.

Historically, many other minerals and compounds besides galena were used for the crystal, the most important being iron pyrite ("fool's gold", iron disulfide, FeS2), silicon, molybdenite (MoS2), and silicon carbide (carborundum, SiC). Some of these other junctions, particularly carborundum, were stable enough that they were equipped with a more permanent spring-loaded contact rather than a cat's whisker.[7] For this reason, carborundum detectors were preferred for use in large commercial wireless stations and military and shipboard stations that were subject to vibration from waves and gunnery exercises. Carborundum detectors, which used large-area contacts, were also particularly robust in this regard. To increase sensitivity, some of these junctions such as silicon carbide were biased by connecting a battery and potentiometer across them to provide a small constant forward voltage across the junction. Later, when AM radio transmission was developed to transmit sound, around World War I, crystal detectors proved able to receive this transmission as well.

After about 1920, receivers using crystal detectors were largely superseded by the first amplifying receivers, which used vacuum tubes. These did not require the fussy adjustments that crystals required, were more sensitive, and also were powerful enough to drive loudspeakers. The point-contact semiconductor detector was subsequently resurrected around World War II because of the military requirement for microwave radardetectors. Vacuum-tube detectors do not work at microwave frequencies Silicon and germanium point-contact diodes were developed. Wartime research on p-n junctions in crystals paved the way for the invention of the point-contact transistor in 1947.The germanium diodes that became widely available after the war proved to be as sensitive as galena and did not require any adjustment, so germanium diodes replaced cat's-whisker detectors in the few crystal radios still being made, largely putting an end to the manufacture of this antique radio component.

De Forest quickly refined his device into the triode, which became the basis of long-distance telephone and radio communications, radars, and early digital computers for 50 years, until the advent of the transistor in the 1960s.

 In 1915, AT&T used the innovation to conduct the first transcontinental telephone calls, in conjunction with the Panama-Pacific International Exposition at San Francisco. In October, 1915 AT&T conducted test radio transmissions from the Navy's station in Arlington, Virginia that were heard as far away as Paris and Hawaii.

Beginning in 1913 Armstrong prepared papers and gave demonstrations that comprehensively documented how to employ three-element vacuum tubes in circuits that amplified signals to stronger levels than previously thought possible, and that could also generate high-power oscillations usable for radio transmission. In late 1913 Armstrong applied for patents covering the regenerative circuit, and on October 6, 1914 U.S. patent 1,113,149 was issued for his discovery.

Electromagnetic wave equations

Where 

 is a vector differential operator.

From the start, Maxwell’s theory was the most elegant of all… the fundamental hypothesis of Maxwell’s theory contradicted the usual views, and was not supported by evidence from decisive experiments.”

Producing and Detecting Radio Waves

In November 1886 Hertz constructed the apparatus shown below.

The Oscillator. At the ends are two hollow zinc spheres of diameter 30 cm. The spheres are each connected to copper wires which run into the middle where there is a gap for sparks to jump between.

He applied high voltage a.c. electricity across the central spark-gap, creating sparks.

The sparks caused violent pulses of electric current within the copper wires. These pulses reverberated within the wires, surging back and forth at a rate of roughly 100 million per second.

As Maxwell had predicted, the oscillating electric charges produced electromagnetic waves – radio waves – which spread out through the air around the wires. Some of the waves reached a loop of copper wire 1.5 meters away, producing surges of electric current within it. These surges caused sparks to jump across a spark-gap in the loop

This was an experimental triumph. Hertz had produced and detected radio waves. He had passed electrical energy through the air from one device to another one located over a meter away. Over the next three years, in a series of brilliant experiments, Hertz fully verified Maxwell’s theory. He proved beyond doubt that his apparatus was producing electromagnetic waves, demonstrating that the energy radiating from his electrical oscillators could be reflected, refracted, produce interference patterns, and produce standing waves just like light. No connecting wires were needed. 

Strangely, though, Hertz did not appreciate the monumental practical importance of the electromagnetic waves he had produced.  He said “I do not think that the wireless waves I have discovered will have any practical application.”

The waves Hertz first generated in November 1886 quickly changed the world.

By 1896 Guglielmo Marconi had applied for a patent for wireless communications. By 1901 he had transmitted a wireless signal across the Atlantic Ocean from Britain to Canada.

Scientists and non-scientists alike owe a lot to Heinrich Hertz. At the age of 35 Hertz became very ill, suffering severe migraines. Heinrich Rudolf Hertz died aged 36 in Bonn on January 1, 1894 of blood-vessel inflammation resulting from immune system problems.

“An electric spark generates electro-magnetic radiation.” A circular coil placed away from the source, can receive these signals at a distance. An induction coil can generate Alternating Current, from a Direct Current source. Therefore the secondary of induction coil can be used to generate sparks (signal). Marconi built his wireless telegraphy on these principles.