Micro electromechanical systems

The term MEMS, for Micro Electro Mechanical Systems, was coined in the 1980’s to describe new, sophisticated mechanical systems on a chip, such as micro electric motors, resonators, gears, and so on. Today, the term MEMS in practice is used to refer to any microscopic device with a mechanical function, which can be fabricated in a batch process (for example, an array of microscopic gears fabricated on a microchip would be considered a MEMS device but a tiny laser-machined stent or watch component would not). In Europe, the term MST for Micro System Technology is preferred, and in Japan MEMS are simply referred to as "micromachines". The distinctions in these terms are relatively minor and are often used interchangeably.

Though MEMS processes are generally classified into a number of categories – such as surface machining, bulk machining, LIGA, and EFAB – there are indeed thousands of different MEMS processes. Some produce fairly simple geometries, while others offer more complex 3-D geometries and more versatility. A company making accelerometers for airbags would need a completely different design and process to produce an accelerometer for inertial navigation. Changing from an accelerometer to another inertial device such as a gyroscope requires an even greater change in design and process, and most likely a completely different fabrication facility and engineering team.

MEMS technology has generated a tremendous amount of excitement, due to the vast range of important applications where MEMS can offer previously unattainable performance and reliability standards. In an age where everything must be smaller, faster, and cheaper, MEMS offers a compelling solution. MEMS have already had a profound impact on certain applications such as automotive sensors and inkjet printers. The emerging MEMS industry is already a multi-billion dollar market. It is expected to grow rapidly and become one of the major industries of the 21st century. Cahners In-Stat Group has projected sales of MEMS to reach $12B by 2005. The European NEXUS group projects even larger revenues, using a more inclusive definition of MEMS.

Nuclear fusion

If nuclei are forced to collide, they can undergo nuclear fusion. This process may release or absorb energy. When the resulting nucleus is lighter than that of iron, energy is normally released; when the nucleus is heavier than that of iron, energy is generally absorbed. This process of fusion occurs in stars, which derive their energy from hydrogen and helium. They form, through stellar nucleosynthesis, the light elements (lithium to calcium) as well as some of the heavy elements (beyond iron and nickel, via the S-process). The remaining abundance of heavy elements, from nickel to uranium and beyond, is due to supernova nucleosynthesis, the R-process.

Of course, these natural processes of astrophysics are not examples of nuclear "technology". Because of the very strong repulsion of nuclei, fusion is difficult to achieve in a controlled fashion. Hydrogen bombs obtain their enormous destructive power from fusion, but their energy cannot be controlled. Controlled fusion is achieved in particle accelerators; this is how many synthetic elements are produced. A fusor can also produce controlled fusion and is a useful neutron source. However, both of these devices operate at a net energy loss. Controlled, viable fusion power has proven elusive, despite the occasional hoax. Technical and theoretical difficulties have hindered the development of working civilian fusion technology, though research continues to this day around the world.

Nuclear fusion was initially pursued only in theoretical stages during World War II, when scientists on the Manhattan Project (led by Edward Teller) investigated it as a method to build a bomb. The project abandoned fusion after concluding that it would require a fission reaction to detonate. It took until 1952 for the first full hydrogen bomb to be detonated, so-called because it used reactions between deuterium and tritium. Fusion reactions are much more energetic per unit mass of fuel than fission reactions, but starting the fusion chain reaction is much more difficult.

Frozen gas model

The frozen gas model describes a special case of a gas that is not in equilibrium. The name "frozen gas" can be misleading. A frozen gas is not "frozen" like ice is frozen water. Rather a frozen gas is "frozen" in time (all chemical reactions are assumed to have stopped). Chemical reactions are normally driven by collisions between molecules. If gas pressure is slowly reduced such that chemical reactions can continue then the gas can remain in equilibrium. However, it is possible for gas pressure to be so suddenly reduced that almost all chemical reactions stop. For that situation the gas is considered frozen.

The distinction between equilibrium and frozen is important because it is possible for a gas such as air to have significantly different properties (speed-of-sound, viscosity, et cetera) for the same thermodynamic state; e.g., pressure and temperature. Frozen gas can be a significant issue in the wake behind an entry vehicle. During reentry, free stream air is compressed to high temperature and pressure by the entry vehicle's shock wave. Non-equilibrium air in the shock layer is then transported past the entry vehicle's leading side into a region of rapidly expanding flow that causes freezing. The frozen air can then be entrained into a trailing vortex behind the entry vehicle. Correctly modeling the flow in the wake of an entry vehicle is very difficult. Thermal protection shield (TPS) heating in the vehicle's afterbody is usually not very high, but the geometry and unsteadiness of the vehicle's wake can significantly influence aerodynamics (pitching moment) and particularly dynamic stability.

Aerospace manufacturer

Aerospace manufacturing is a high technology industry that produces "aircraft, guided missiles, space vehicles, aircraft engines, propulsion units, and related parts". Most of the industry is geared toward governmental work. For each Original Equipment Manufacturer (OEM), the US government has assigned a CAGE code. These codes help to identify each manufacturer, repair facilities, and other critical aftermarket vendors in the aerospace industry.

In the United States of America, the Department of Defense and the National Aeronautics and Space Administration (NASA) are the two largest consumers of aerospace technology and products. Others include the very large airline industry. The aerospace industry employed 472,000 wage and salary workers in 2006. Most of those jobs were in Washington state and in California, with Missouri and Texas also important. The leading aerospace manufacturers in the U.S. are Boeing, United Technologies Corporation, and Lockheed Martin.

These manufacturers are facing an increasing labor shortage as skilled U.S. workers age and retire. Apprenticeship programs such as the Aerospace Joint Apprenticeship Council (AJAC) work in collaboration with Washington state aerospace employers and community colleges to train new manufacturing employees to keep the industry supplied.

Important locations of the civilian aerospace industry worldwide include Washington state (Boeing), California (Boeing, Lockheed Martin, etc.); Montreal, Canada (Bombardier, Pratt & Whitney Canada); Toulouse, France (Airbus/EADS); and Hamburg, Germany (Airbus/EADS); as well as São José dos Campos, where the Brazilian Embraer company is based.

In the European Union, aerospace companies such as EADS, BAE Systems, Thales, Dassault, Saab and Finmeccanica account for a large share of the global aerospace industry and research effort, with the European Space Agency as one of the largest consumers of aerospace technology and products.

In India, Bangalore is a major center of the aerospace industry, where Hindustan Aeronautics Limited, the National Aerospace Laboratories and the Indian Space Research Organisation are headquartered. The Indian Space Research Organisation (ISRO) launched India's first Moon orbiter, Chandrayaan-1, in October 2008.

In Russia, large aerospace companies like Oboronprom and the United Aircraft Building Corporation (encompassing Mikoyan, Sukhoi, Ilyushin, Tupolev, Yakovlev, and Irkut which includes Beriev) are among the major global players in this industry. The historic Soviet Union was also the home of a very major aerospace industry.

The United Kingdom formerly attempted to maintain its own large aerospace industry, making its own airliners and warplanes, but it has largely turned its lot over to cooperative efforts with continental companies, and it has turned into a large import customer, too, from countries such the United States. However, the UK has a very active aerospace sector, including the largest defence contractor in the world, BAE Systems, supplying fully assembled aircraft, aircraft components, sub-assemblies and sub-systems to other manufacturers, both in Europe and all over the world.

Canada has formerly manufactured some of its own designs for jet warplanes, etc. (e.g. the CF-100 fighter), but for some decades, it has relied on imports from the United States to fill these needs. However Canada still manufactures some military planes although they are generally not combat or fighter planes.

Observations and explorations of Venus

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the solar system, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the solar system. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970 Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.