NATO Stock Number
A NATO Stock Number, or National Stock Number as it is known in the US, is a 13-digit numeric code, identifying all the'standardized material items of supply' as they have been recognized by all NATO countries including United States Department of Defense. Pursuant to the NATO Standardization Agreements, the NSN has come to be used in all treaty countries. However, many countries that use the NSN program are not members of NATO, e.g. Japan and New Zealand. A two-digit Material Management Aggregation Code suffix may be appended, to denote asset end use but it is not considered part of the NSN. In the United Kingdom it is known as a Domestic Management Code. An item having an NSN is said to be "stock-listed"; the NATO Stock Number consists of the National Item Identification Number. However the NIIN alone uniquely identifies the item, the FSC adds context by indicating the general classification of the item; the format of an NSN might be described as follows: abcd-ef-ghi-jklm Each element, a through m, was intended to be a single decimal digit.
As inventories grew in complexity, element g became alphanumeric, beginning with uppercase A for certain newly added items. By 2000, uppercase C was in use; the initial subgroup, abcd, is the Federal Supply Classification Group or National Supply Classification Group. In theory, similar items would always have related numbers in this section of the NSN, no matter how the section is referred to; as the number of items has increased and the system has become more complicated, it has not always been possible to keep similarity in numbers when the items are similar. The nine digits, ef-ghi-jklm, comprise the NIIN; this format improves readability but is optional as NIINs are listed without hyphens. The first two digits of the NIIN is used to record which country was the first to codify the item—which one first recognized it as an important item of supply; this is the country of origin, meaning the country of final manufacture. The formal name of the field is CC for Country Code or NCB, because NCB stands for National Codification Bureau.
The NCB is the organisation a government agency, in charge of maintaining the NCS database within a given country. The other 7 characters are a non significant identification number. Following are the NCB codes: As the list shows, users of the NCS system not only include the 29 NATO member countries, but the 33 NATO-sponsored countries as well, it is grouped into tiers indicating participation and access. Tier 1 Nations Nation has access to unclassified NSN data. There is a one-way data exchange and it does not participate in technical NCS management. Tier 2 Nations Nation has a codification system, certified as NCS compliant. There is a two-way data participation in technical NCS management. Tier 3 Nations: Nation is a NATO member and has a full membership in the NATO Codification Bureau. Other Nations. Pakistan and Papua New Guinea have NCB codes but are not in the 1st Tier. Fiji and Tonga are not in Tier 1 and their NCB codes are no longer listed. Ireland and Trinidad and Tobago do they have assigned NCB code numbers.
Ireland, Pakistan, Papua New Guinea, Trinidad and Tobago maintain connections through a liaison office. The first countries to receive NCB code numbers were the United Kingdom and New Zealand - as they had been involved in the program. NATO was assigned the NCB code for its items as it was the next number available after the 00 to 10 block set aside for the United States' own use. Canada received and because it was supplying items for the United States and the Commonwealth before the system was in place; the NCB code has been discontinued. Iceland and Luxembourg do not use them. All of Luxembourg's transactions are catalogued by Belgium and Iceland uses other nations' NSNs when they make or order any stock items; this is an alphanumeric four-symbol code consisting of either one letter followed by three numerals or two letters followed by two numerals. This code is shown either on the line underneath it on the container; the DODIC identifies the item, while the NSN identifies what type of item it is and how it is packaged and contained.
Sometimes the DODIC contains a two-numeral NCB code prefix for the manufacturer's or repacker's countr
A nut is a type of fastener with a threaded hole. Nuts are always used in conjunction with a mating bolt to fasten multiple parts together; the two partners are kept together by a combination of their threads' friction, a slight stretching of the bolt, compression of the parts to be held together. In applications where vibration or rotation may work a nut loose, various locking mechanisms may be employed: lock washers, jam nuts, specialist adhesive thread-locking fluid such as Loctite, safety pins or lockwire in conjunction with castellated nuts, nylon inserts, or oval-shaped threads. Square nuts, as well as bolt heads, were the first shape made and used to be the most common because they were much easier to manufacture by hand. While rare today due to the reasons stated below for the preference of hexagonal nuts, they are used in some situations when a maximum amount of torque and grip is needed for a given size: the greater length of each side allows a spanner to be applied with a larger surface area and more leverage at the nut.
The most common shape today is hexagonal, for similar reasons as the bolt head: six sides give a good granularity of angles for a tool to approach from, but more corners would be vulnerable to being rounded off. It takes only one sixth of a rotation to obtain the next side of the grip is optimal. However, polygons with more than six sides do not give the requisite grip and polygons with fewer than six sides take more time to be given a complete rotation. Other specialized shapes exist for certain needs, such as wingnuts for finger adjustment and captive nuts for inaccessible areas. A wide variety of nuts exists, from household hardware versions to specialized industry-specific designs that are engineered to meet various technical standards. Fasteners used in automotive and industrial applications need to be tightened to a specific torque setting, using a torque wrench. Nuts are graded with strength ratings compatible with their respective bolts. An SAE class 5 nut can support the proof load of an SAE class 5 bolt, so on.
Castellated nut Distorted thread locknut Centerlock nut Elliptical offset locknut Toplock nut Interfering thread nut Tapered thread nut Jam nut Jet nut Keps nut with a star-type lock washer Nyloc plate nut Polymer insert nut Security locknut Serrated face nut Serrated flange nut Speed nut Split beam nut BINX nut Note that flat sizes differ between industry standards. For example, wrench sizes of fastener used in Japanese built cars comply with JIS automotive standard. In normal use, a nut-and-bolt joint holds together because the bolt is under a constant tensile stress called the preload; the preload pulls the nut threads against the bolt threads, the nut face against the bearing surface, with a constant force, so that the nut cannot rotate without overcoming the friction between these surfaces. If the joint is subjected to vibration, the preload increases and decreases with each cycle of movement. If the minimum preload during the vibration cycle is not enough to hold the nut in contact with the bolt and the bearing surface the nut is to become loose.
Specialized locking nuts exist to prevent this problem, but sometimes it is sufficient to add a second nut. For this technique to be reliable, each nut must be tightened to the correct torque; the inner nut is tightened to about a quarter to a half of the torque of the outer nut. It is held in place by a wrench while the outer nut is tightened on top using the full torque; this arrangement causes the two nuts to push on each other, creating a tensile stress in the short section of the bolt that lies between them. When the main joint is vibrated, the stress between the two nuts remains constant, thus holding the nut threads in constant contact with the bolt threads and preventing self-loosening; when the joint is assembled the outer nut bears the full tension of the joint. The inner nut functions to add a small additional force to the outer nut and does not need to be as strong, so a thin nut can be used. Bickford, John H..
Monoculture is the agricultural practice of producing or growing a single crop, plant, or livestock species, variety, or breed in a field or farming system at a time. Polyculture, where more than one crop is grown in the same space at the same time, is the alternative to monoculture. Monoculture is used in both industrial farming and organic farming and has allowed increased efficiency in planting and harvest. Continuous monoculture, or monocropping, where the same species is grown year after year, can lead to the quicker buildup of pests and diseases, rapid spread where a uniform crop is susceptible to a pathogen; some examples of Monocultures aggressive with the environment are: Monoculture of African Palm Oil, Monoculture of Sugar Cane, Monocultures of Pines, Monoculture of Soybean. The practice has been criticized for its environmental effects and for putting the food supply chain at risk. Diversity can be added both in time, as with a crop rotation or sequence, or in space, with a polyculture.
Oligoculture has been suggested to describe a crop rotation of just a few crops, as is practiced by several regions of the world. The term monoculture is applied for other uses to describe any group dominated by a single variety, e.g. social monoculturalism, or in the field of musicology to describe the dominance of the American and British music-industries in Western pop music, or in the field of computer science to describe a group of computers all running identical software. The term is used in agriculture and describes the practice of planting the same cultivar over an extended area; each cultivar has the same standardized planting and harvesting requirements resulting in greater yields and lower costs. For example, researchers have discovered a native plant to Senegal, called Guiera senegalensis, grown next to millet increased millet production 900 percent, it is beneficial because a crop can be tailor-planted for a location that has special problems – like soil salt or drought or a short growing season.
When a crop is matched to its well-managed environment, a monoculture can produce higher yields than a polyculture. In the last 40 years, modern practices such as monoculture planting and the use of synthesized fertilizers have reduced the amount of additional land needed to produce food. However, planting the same crop in the same place each year depletes the nutrients from the earth that the plant relies on and leaves soil weak and unable to support healthy plant growth; because soil structure and quality is so poor, farmers are forced to use chemical fertilizers to encourage plant growth and fruit production. These fertilizers, in turn, disrupt the natural makeup of the soil and contribute further to nutrient depletion. Monocropping creates the spread of pests and diseases, which have to be treated with yet more chemicals; the effects of monocropping on the environment are severe when pesticides and fertilizers make their way into ground water or become airborne, creating pollution. In forestry, monoculture refers to the planting of one species of tree.
Monoculture plantings provide greater yields and more efficient harvesting than natural stands of trees. Single-species stands of trees are the natural way trees grow, but the stands show a diversity in tree sizes, with dead trees mixed with mature and young trees. In forestry, monoculture stands that are planted and harvested as a unit provide limited resources for wildlife that depend on dead trees and openings, since all the trees are the same size; the mechanical harvesting of trees can compact soils. Single-species planting causes trees to be more vulnerable when they are infected with a pathogen, or attacked by insects, or affected by adverse environmental conditions. Examples of monoculture include most fields of wheat or corn; the term is used where a single breed of farm animal is raised in large-scale concentrated animal feeding operations. In the United States, The Livestock Conservancy was formed to protect nearly 200 endangered livestock breeds from going extinct due to the increased reliance on just a handful of specialized breeds.
Crops used in agriculture are single strains that have been bred for high yield and for resistance to certain common diseases. Given that all plants in a monoculture are genetically similar, if a disease strikes to which they have no resistance, it can destroy entire populations of crops. Polyculture, the mixing of different crops, reduces the likelihood that one or more of the crops will be resistant to any particular pathogen. Studies have shown that planting a mixture of crop strains in the same field can combat disease effectively. Ending monocultures grown under disease conditions by introducing crop diversity has increased yields. In one study in China, the planting of several varieties of rice in the same field increased yields of non-resistant strains by 89% compared to non-resistant strains grown in monoculture because of a dramatic decrease in the incidence of disease, making pesticides less necessary; as of 2009 the wheat leaf-rust fungus occasioned a great deal of worry internationally, having decimated wheat crops in Uganda and Kenya, having started to make inroads into Asia as well.
Given the genetically similar strains of much of the world's wheat crops following the Green Revolution, the impacts of such diseases threaten agricultural production worldwide. In Ireland, exclusive use of one variety of potato, the "lumper", led to the Great Famine of 1845-1849. Lumpers provided inexpensive food to feed the Irish masses. Potatoes were propagated vegetatively with little to no genetic variation. Whe
Natural rubber called India rubber or caoutchouc, as produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds, plus water. Thailand and Indonesia are two of the leading rubber producers. Forms of polyisoprene that are used as natural rubbers are classified as elastomers. Rubber is harvested in the form of the latex from the rubber tree or others; the latex is a sticky, milky colloid drawn off by making incisions in the bark and collecting the fluid in vessels in a process called "tapping". The latex is refined into rubber ready for commercial processing. In major areas, latex is allowed to coagulate in the collection cup; the coagulated lumps are processed into dry forms for marketing. Natural rubber is used extensively in many applications and products, either alone or in combination with other materials. In most of its useful forms, it has a large stretch ratio and high resilience, is waterproof; the major commercial source of natural rubber latex is the Pará rubber tree, a member of the spurge family, Euphorbiaceae.
This species is preferred. A properly managed tree responds to wounding by producing more latex for several years. Congo rubber a major source of rubber, came from vines in the genus Landolphia. Dandelion milk contains latex; the latex exhibits the same quality as the natural rubber from rubber trees. In the wild types of dandelion, latex content varies greatly. In Nazi Germany, research projects tried to use dandelions as a base for rubber production, but failed. In 2013, by inhibiting one key enzyme and using modern cultivation methods and optimization techniques, scientists in the Fraunhofer Institute for Molecular Biology and Applied Ecology in Germany developed a cultivar, suitable for commercial production of natural rubber. In collaboration with Continental Tires, IME began a pilot facility. Many other plants produce forms of latex rich in isoprene polymers, though not all produce usable forms of polymer as as the Pará; some of them require more elaborate processing to produce anything like usable rubber, most are more difficult to tap.
Some produce other desirable materials, for example chicle from Manilkara species. Others that have been commercially exploited, or at least showed promise as rubber sources, include the rubber fig, Panama rubber tree, various spurges, the related Scorzonera tau-saghyz, various Taraxacum species, including common dandelion and Russian dandelion, most for its hypoallergenic properties, guayule; the term gum rubber is sometimes applied to the tree-obtained version of natural rubber in order to distinguish it from the synthetic version. The first use of rubber was by the indigenous cultures of Mesoamerica; the earliest archeological evidence of the use of natural latex from the Hevea tree comes from the Olmec culture, in which rubber was first used for making balls for the Mesoamerican ballgame. Rubber was used by the Maya and Aztec cultures – in addition to making balls Aztecs used rubber for other purposes such as making containers and to make textiles waterproof by impregnating them with the latex sap.
The Pará rubber tree is indigenous to South America. Charles Marie de La Condamine is credited with introducing samples of rubber to the Académie Royale des Sciences of France in 1736. In 1751, he presented a paper by François Fresneau to the Académie that described many of rubber's properties; this has been referred to as the first scientific paper on rubber. In England, Joseph Priestley, in 1770, observed that a piece of the material was good for rubbing off pencil marks on paper, hence the name "rubber", it made its way around England. In 1764 François Fresnau discovered. Giovanni Fabbroni is credited with the discovery of naphtha as a rubber solvent in 1779. South America remained the main source of latex rubber used during much of the 19th century; the rubber trade was controlled by business interests but no laws expressly prohibited the export of seeds or plants. In 1876, Henry Wickham smuggled 70,000 Pará rubber tree seeds from Brazil and delivered them to Kew Gardens, England. Only 2,400 of these germinated.
Seedlings were sent to India, British Ceylon, Dutch East Indies and British Malaya. Malaya was to become the biggest producer of rubber. In the early 1900s, the Congo Free State in Africa was a significant source of natural rubber latex gathered by forced labor. King Leopold II's colonial state brutally enforced production quotas. Tactics to enforce the rubber quotas included removing the hands of victims to prove they had been killed. Soldiers came back from raids with baskets full of chopped-off hands. Villages that resisted were razed to encourage better compliance locally. See Atrocities in the Congo Free State for more information on the rubber trade in the Congo Free State in the late 1800s and early 1900s. Liberia and Nigeria started production. In India, commercial cultivation was introduced by British planters, although the experimental efforts to grow rubber on a commercial scale were initiated as early as 1873 at the Calcutta Botanical Gardens; the first commercial Hevea plantations were established at Thattekadu in Kerala in 1902.
In years the plantation expanded to Karnataka, Tamil Nadu and the Andaman and Nicobar Islands of India. India today is the
MIL-STD-1750A or 1750A is the formal definition of a 16-bit computer instruction set architecture, including both required and optional components, as described by the military standard document MIL-STD-1750A. In addition to the core ISA, the definition defines optional instructions, such as a FPU and MMU; the standard does not define the implementation details of a 1750A processor. The 1750A supports 216 16-bit words of memory for the core standard; the standard defines an optional memory management unit that allows 220 16-bit words of memory using 512 page mapping registers, defining separate instruction and data spaces, keyed memory access control. Most instructions are 16 bits; the standard computer has 16 general purpose 16-bit registers. Registers 1 through 15 can be used as index registers. Registers 12 through 15 can be used as base registers. Any of the 16 registers could be used as a stack pointer for the SJS and URS instructions, but only register 15 was used as the stack pointer for the PSHM and POPM instructions.
The computer has instructions for 16, 32-bit binary arithmetic, as well as 32 and 48 bit floating point. I/O is via the I/O instructions, which have a separate 216 16-bit word address space and may have a specialized bus; because MIL-STD-1750A did not define implementation details, 1750A products are available from a wide variety of companies in the form of component and system-level offerings implemented in myriad technologies the most advanced and exotic of their respective periods. Of particular interest is the fact that 1750A systems offer high levels of radiation and other hazardous environment protection, making them suited for military and space applications. Examples of MIL-STD-1750A implementations include: CPU Technology, Inc. CPU1750A-FB, a high performance 1750A SOC designed to give existing applications a late life performance boost. Dynex Semiconductor MAS281. A radiation hardened SOC implementation on a 64-pin multichip module with an optional MMU. GEC-Plessey RH1750, a radiation-hardened version for aerospace and space flight applications.
GEC-Plessey, under its previous incarnation as Marconi Electronic Devices initially developed the MAS281 and MA31750A series of processors made available through Dynex Semiconductor Honeywell HX1750, fabricated on Honeywell's Silicon on Insulator CMOS process giving radiation hardness. The HX1750 includes an FPU and peripherals on chip. Johns Hopkins University Applied Physics Laboratory MIL-STD-1750AAV space flight qualified processor. A multi-board silicon on sapphire implementation designed for space flight. Marconi Electronic Devices MIL-STD-1750A. McDonnell-Douglas MD-281. A radiation hardened SoS three die implementation on a 64-pin multichip module. National Semiconductor F9450 series. Pyramid Semiconductor PACE P1750A; the family includes the P1750A CPU, the P1750AE Enhanced CPU, the P1753 Memory Management Unit, the P1754 Processor Interface Chip and the P1757ME Multi-Chip Module. This line was acquired from Performance Semiconductor in 2003. Royal Aircraft Establishment Farnborough MIL-STD-1750A implementation in AMD 2901 bit-slice technology.
Processors based on MIL-STD-1750A are programmed in JOVIAL, a high-level programming language defined by the United States Department of Defense, derived from ALGOL 58. To a lesser extent, Ada was used. There are C compilers, for example Cleanscape XTC-1750A. Older versions of GNU GCC contain support for MIL-STD-1750A. In addition, DDC-I provides its SCORE Integrated Development Environment with both Ada95 and C compilers, TADS Ada83 development environment, both targeting processors based on MIL-STD-1750A; the U. S. Air Force defined the standard in order to have a common computing architecture and thereby reduce the costs of software and computer systems for all military computing needs; this includes embedded tasks such as aircraft and missile control systems as well as more mundane general military computing needs. The advantages of this concept were recognized outside of the USAF and the 1750A was adopted by numerous other organizations, such as the European Space Agency, NASA, Israeli Aircraft Industries and many projects in academia.
Examples of military aircraft using the 1750A include: IAI Lavi fighter IBM Federal Systems AP-102 Avionics Computer US Army AH-64D Apache Longbow Helicopter USAF F-16 Digital Flight Control System and Fire Control Computer USN F-18 RFCS Flight Control Computer Fully space rated implementations make the 1750A one of the few types of computers that are applicable for use in deep space applications. Example spacecraft that use the 1750A are: EOS Aqua and Terra ESA Cluster ESA Envisat - Envisat's ASAR instrument, built by Matra Marconi Space and comprising the Central Electronics Sub-Assembly and Antenna Sub-Assembly used a total of 42 GEC-Plessey MA31750A processors in a dual-redundant configuration ESA Rosetta ISRO GSAT/INSAT/IRS series of spacecrafts ISRO Mars Orbiter Mission ISRO Space Recovery Experiment-1 Guidance and Navigation Computer Midcourse Space Experiment spacecraft developed at JHU/APL MSTI-1, 2 and 3 NASA Cassini NASA Landsat 7 NASA Mars Global Surveyor Naval Research Laboratory Clementine Lunar Orbiter NOAA GOES-13, GOES-O and GOES-P Orbital Sciences Corporation commercial communication satellite platforms USAF Titan-4 Guidance Computer Software Vendo
Reliability engineering is a sub-discipline of systems engineering that emphasizes dependability in the lifecycle management of a product. Dependability, or reliability, describes the ability of a system or component to function under stated conditions for a specified period of time. Reliability is related to availability, described as the ability of a component or system to function at a specified moment or interval of time. Reliability is theoretically defined as the probability of success. Testability and maintenance are defined as a part of "reliability engineering" in reliability programs. Reliability plays a key role in the cost-effectiveness of systems. Reliability engineering deals with the estimation and management of high levels of "lifetime" engineering uncertainty and risks of failure. Although stochastic parameters define and affect reliability, reliability is not achieved by mathematics and statistics. One cannot find a root cause by only looking at statistics. "Nearly all teaching and literature on the subject emphasize these aspects, ignore the reality that the ranges of uncertainty involved invalidate quantitative methods for prediction and measurement."
For example, it is easy to represent "probability of failure" as a symbol or value in an equation, but it is impossible to predict its true magnitude in practice, massively multivariate, so having the equation for reliability does not begin to equal having an accurate predictive measurement of reliability. Reliability engineering relates to safety engineering and to system safety, in that they use common methods for their analysis and may require input from each other. Reliability engineering focuses on costs of failure caused by system downtime, cost of spares, repair equipment and cost of warranty claims. Safety engineering focuses more on preserving life and nature than on cost, therefore deals only with dangerous system-failure modes. High reliability levels result from good engineering and from attention to detail, never from only reactive failure management; the word reliability can be traced back to 1816, is first attested to the poet Samuel Taylor Coleridge. Before World War II the term was linked to repeatability.
In the 1920s, product improvement through the use of statistical process control was promoted by Dr. Walter A. Shewhart at Bell Labs, around the time that Waloddi Weibull was working on statistical models for fatigue; the development of reliability engineering was here on a parallel path with quality. The modern use of the word reliability was defined by the U. S. military in the 1940s, characterizing a product that would operate when expected and for a specified period of time. In World War II, many reliability issues were due to the inherent unreliability of electronic equipment available at the time, to fatigue issues. In 1945, M. A. Miner published the seminal paper titled "Cumulative Damage in Fatigue" in an ASME journal. A main application for reliability engineering in the military was for the vacuum tube as used in radar systems and other electronics, for which reliability proved to be problematic and costly; the IEEE formed the Reliability Society in 1948. In 1950, the United States Department of Defense formed group called the "Advisory Group on the Reliability of Electronic Equipment" to investigate reliability methods for military equipment.
This group recommended three main ways of working: Improve component reliability. Establish quality and reliability requirements for suppliers. Collect field data and find root causes of failures. In the 1960s, more emphasis was given to reliability testing on system level; the famous military standard 781 was created at that time. Around this period the much-used military handbook 217 was published by RCA and was used for the prediction of failure rates of components; the emphasis on component reliability and empirical research alone decreased. More pragmatic approaches, as used in the consumer industries, were being used. In the 1980s, televisions were made up of solid-state semiconductors. Automobiles increased their use of semiconductors with a variety of microcomputers under the hood and in the dash. Large air conditioning systems developed electronic controllers, as had microwave ovens and a variety of other appliances. Communications systems began to adopt electronics to replace older mechanical switching systems.
Bellcore issued the first consumer prediction methodology for telecommunications, SAE developed a similar document SAE870050 for automotive applications. The nature of predictions evolved during the decade, it became apparent that die complexity wasn't the only factor that determined failure rates for integrated circuits. Kam Wong published a paper questioning the bathtub curve—see reliability-centered maintenance. During this decade, the failure rate of many components dropped by a factor of 10. Software became important to the reliability of systems. By the 1990s, the pace of IC development was picking up. Wider use of stand-alone microcomputers was common, the PC market helped keep IC densities follow
United States Armed Forces
The United States Armed Forces are the military forces of the United States of America. It consists of the Army, Marine Corps, Air Force, Coast Guard; the President of the United States is the Commander-in-Chief of the Armed Forces and forms military policy with the Department of Defense and Department of Homeland Security, both federal executive departments, acting as the principal organs by which military policy is carried out. All five armed services are among the seven uniformed services of the United States. From the time of its inception, the U. S. Armed Forces played a decisive role in the history of the United States. A sense of national unity and identity was forged as a result of victory in the First Barbary War and the Second Barbary War. So, the founders of the United States were suspicious of a permanent military force, it played a critical role in the American Civil War, continuing to serve as the armed forces of the United States, although a number of its officers resigned to join the military of the Confederate States.
The National Security Act of 1947, adopted following World War II and during the Cold War's onset, created the modern U. S. military framework. The Act established the National Military Establishment, headed by the Secretary of Defense, it was amended in 1949, renaming the National Military Establishment the Department of Defense, merged the cabinet-level Department of the Army, Department of the Navy, Department of the Air Force, into the Department of Defense. The U. S. Armed Forces are one of the largest militaries in terms of the number of personnel, it draws its personnel from a large pool of paid volunteers. Although conscription has been used in the past in various times of both war and peace, it has not been used since 1973, but the Selective Service System retains the power to conscript males, requires that all male citizens and residents residing in the U. S. between the ages of 18–25 register with the service. On February 22, 2019, however, a federal judge ruled that registering only males for Selective Service is unconstitutional.
As of 2017, the U. S. spends about US$610 billion annually to fund its military forces and Overseas Contingency Operations. Put together, the U. S. constitutes 40 percent of the world's military expenditures. The U. S. Armed Forces has significant capabilities in both defense and power projection due to its large budget, resulting in advanced and powerful technologies which enables a widespread deployment of the force around the world, including around 800 military bases outside the United States; the U. S. Air Force is the world's largest air force, the U. S. Navy is the world's largest navy by tonnage, the U. S. Navy and the U. S. Marine Corps combined are the world's second largest air arm. In terms of size, the U. S. Coast Guard is the world's 12th largest naval force; the history of the U. S. Armed Forces dates to 14 June 1775, with the creation of the Continental Army before the Declaration of Independence marked the establishment of the United States; the Continental Navy, established on 13 October 1775, Continental Marines, established on 10 November 1775, were created in close succession by the Second Continental Congress in order to defend the new nation against the British Empire in the American Revolutionary War.
These forces demobilized in 1784. The Congress of the Confederation created the current United States Army on 3 June 1784; the United States Congress created the current United States Navy on 27 March 1794 and the current United States Marine Corps on 11 July 1798. All three services trace their origins to their respective Continental predecessors; the 1787 adoption of the Constitution gave the Congress the power to "raise and support armies", to "provide and maintain a navy" and to "make rules for the government and regulation of the land and naval forces", as well as the power to declare war. The President is the U. S. Armed Forces' commander-in-chief; the United States Coast Guard traces its origin to the founding of the Revenue Cutter Service on 4 August 1790 which merged with the United States Life-Saving Service on 28 January 1915 to establish the Coast Guard. The United States Air Force was established as an independent service on 18 September 1947. S. Signal Corps, formed 1 August 1907 and was part of the Army Air Forces before becoming an independent service as per the National Security Act of 1947.
The United States Public Health Service Commissioned Corps was considered to be a branch of the United States Armed Forces from 29 July 1945 until its status as such was revoked on 3 July 1952. On March 1st, 2019, the Department of Defense sent a proposal to Congress that would establish the United States Space Force as an independent military service within the Department of the Air Force. If approved, this would become the sixth military service branch to be created. Command over the U. S. Armed Forces is established in the Constitution; the sole power of command is vested in the President by Article II as Commander-in-Chief. The Constitution presumes the existence of "executive Departments" headed by "principal officers", whose appointment mechanism is provided for in the Appointments Clause; this allowance in the Constitution formed the basis for creation of the Department of Defense in 1947 by the National Security Act. The DoD is headed by the Secretary of Defense, a civilian and member of the Cabinet.
The Defense Secretary is second in the U. S. Armed Forces chain of command, with the exception of the Coast Guard, under the Secretary of Homeland Security, is just below the President and serves as the