The Saint Helena Constitution took effect in 1989 and provided that the island would be governed by a Governor and Commander-in-Chief, and an elected Executive and Legislative Council. In 2002, the British Overseas Territories Act 2002 granted full British citizenship to the islanders, and renamed the Dependent Territories (including Saint Helena) the British Overseas Territories. In 2009, Saint Helena and its two territories received equal status under a new constitution, and the British Overseas Territory was renamed Saint Helena, Ascension and Tristan da Cunha.


The UK government has spent £250 million in the construction of the island's airport. Expected to be fully operational early 2016, it is expected to help the island towards self-sufficiency and encourage economic development, reducing dependence on British government aid. The airport is also expected to kick start the tourism industry, with up to 30,000 visitors expected annually. As of August, 2015 ticketing was postponed until an airline could be firmly designated.


Located in the South Atlantic Ocean on the Mid-Atlantic Ridge, more than 2,000 kilometres (1,200 mi) from the nearest major landmass, Saint Helena is one of the most remote places in the world. The nearest port on the continent is Namibe in southern Angola, and the nearest international airport the Quatro de Fevereiro Airport of Angola's capital Luanda; connections to Cape Town in South Africa are used for most shipping needs, such as the mail boat that serves the island, the RMS St Helena. The island is associated with two other isolated islands in the southern Atlantic, also British territories: Ascension Island about 1,300 kilometres (810 mi) due northwest in more equatorial waters and Tristan da Cunha, which is well outside the tropics 2,430 kilometres (1,510 mi) to the south. The island is situated in the Western Hemisphere and has the same longitude as Cornwall in the United Kingdom. Despite its remote location, it is classified as being in West Africa by the United Nations.


The island of Saint Helena has a total area of 122 km2 (47 sq mi), and is composed largely of rugged terrain of volcanic origin (the last volcanic eruptions occurred about 7 million years ago). Coastal areas are covered in volcanic rock and warmer and drier than the centre. The highest point of the island is Diana's Peak at 818 m (2,684 ft). In 1996 it became the island's first national park. Much of the island is covered by New Zealand flax, a legacy of former industry, but there are some original trees augmented by plantations, including those of the Millennium Forest project which was established in 2002 to replant part of the lost Great Wood and is now managed by the Saint Helena National Trust. When the island was discovered, it was covered with unique indigenous vegetation, including a remarkable cabbage tree species. The island's hinterland must have been a dense tropical forest but the coastal areas were probably also quite green. The modern landscape is very different, with widespread bare rock in the lower areas, although inland it is green, mainly due to introduced vegetation. There are no native land mammals, but cattle, cats, dogs, donkeys, goats, mice, rabbits, rats and sheep have been introduced, and native species have been adversely affected as a result. The dramatic change in landscape must be attributed to these introductions. As a result, the string tree (Acalypha rubrinervis) and the St Helena olive (Nesiota elliptica) are now extinct, and many of the other endemic plants are threatened with extinction.


There are several rocks and islets off the coast, including: Castle Rock, Speery Island, the Needle, Lower Black Rock, Upper Black Rock (South), Bird Island (Southwest), Black Rock, Thompson's Valley Island, Peaked Island, Egg Island, Lady's Chair, Lighter Rock (West), Long Ledge (Northwest), Shore Island, George Island, Rough Rock Island, Flat Rock (East), the Buoys, Sandy Bay Island, the Chimney, White Bird Island and Frightus Rock (Southeast), all of which are within one kilometre (0.62 miles) of the shore.


The national bird of Saint Helena is the Saint Helena plover, known locally as the wirebird. It appears on the coat of arms of Saint Helena and on the flag.


The climate of Saint Helena is tropical, marine and mild, tempered by the Benguela Current and trade winds that blow almost continuously. The climate varies noticeably across the island. Temperatures in Jamestown, on the north leeward shore, range between 21–28 °C (70–82 °F) in the summer (January to April) and 17–24 °C (63–75 °F) during the remainder of the year. The temperatures in the central areas are, on average, 5–6 °C (9.0–10.8 °F) lower. Jamestown also has a very low annual rainfall, while 750–1,000 mm (30–39 in) falls per year on the higher ground and the south coast, where it is also noticeably cloudier. There are weather recording stations in the Longwood and Blue Hill districts.


Saint Helena is divided into eight districts, each with a community centre. The districts also serve as statistical subdivisions. The island is a single electoral area and elects twelve representatives to the Legislative Council of fifteen.


Saint Helena was first settled by the English in 1659, and the island has a population of about 4,250 inhabitants, mainly descended from people from Britain – settlers ("planters") and soldiers – and slaves who were brought there from the beginning of settlement – initially from Africa (the Cape Verde Islands, Gold Coast and west coast of Africa are mentioned in early records), then India and Madagascar. Eventually the planters felt there were too many slaves and no more were imported after 1792.


In 1840, St Helena became a provisioning station for the British West Africa Squadron, preventing slavery to Brazil (mainly), and many thousands of slaves were freed on the island. These were all African, and about 500 stayed while the rest were sent on to the West Indies and Cape Town, and eventually to Sierra Leone.


Imported Chinese labourers arrived in 1810, reaching a peak of 618 in 1818, after which numbers were reduced. Only a few older men remained after the British Crown took over the government of the island from the East India Company in 1834. The majority were sent back to China, although records in the Cape suggest that they never got any farther than Cape Town. There were also a very few Indian lascars who worked under the harbour master.


The citizens of Saint Helena hold British Overseas Territories citizenship. On 21 May 2002, full British citizenship was restored by the British Overseas Territories Act 2002. See also British nationality law.


During periods of unemployment, there has been a long pattern of emigration from the island since the post-Napoleonic period. The majority of "Saints" emigrated to the UK, South Africa and in the early years, Australia. The population has steadily declined since the late 1980s and has dropped from 5,157 at the 1998 census to 4,255 in 2008. In the past emigration was characterised by young unaccompanied persons leaving to work on long-term contracts on Ascension and the Falkland Islands, but since "Saints" were re-awarded UK citizenship in 2002, emigration to the UK by a wider range of wage-earners has accelerated due to the prospect of higher wages and better progression prospects.


Most residents belong to the Anglican Communion and are members of the Diocese of St Helena, which has its own bishop and includes Ascension Island. The 150th anniversary of the diocese was celebrated in June 2009.


Other Christian denominations on the island include: Roman Catholic (since 1852), Salvation Army (since 1884), Baptist (since 1845) and, in more recent times, Seventh-day Adventist (since 1949), New Apostolic and Jehovah's Witnesses (of which one in 35 residents is a member, the highest ratio of any country). The Catholics are pastorally served by the Mission sui iuris of Saint Helena, Ascension and Tristan da Cunha, whose office of ecclesiastical superior is vested in the Apostolic Prefecture of the Falkland Islands.


Executive authority in Saint Helena is vested in Queen Elizabeth II and is exercised on her behalf by the Governor of Saint Helena. The Governor is appointed by the Queen on the advice of the British government. Defence and Foreign Affairs remain the responsibility of the United Kingdom.


There are fifteen seats in the Legislative Council of Saint Helena, a unicameral legislature, in addition to a Speaker and a Deputy Speaker. Twelve of the fifteen members are elected in elections held every four years. The three ex officio members are the Chief Secretary, Financial Secretary and Attorney General. The Executive Council is presided over by the Governor, and consists of three ex officio officers and five elected members of the Legislative Council appointed by the Governor. There is no elected Chief Minister, and the Governor acts as the head of government. In January 2013 it was proposed that the Executive Council would be led by a "Chief Councillor" who would be elected by the members of the Legislative Council and would nominate the other members of the Executive Council. These proposals were put to a referendum on 23 March 2013 where they were defeated by 158 votes to 42 on a 10% turnout.


One commentator has observed that, notwithstanding the high unemployment resulting from the loss of full passports during 1981–2002, the level of loyalty to the British monarchy by the St Helena population is probably not exceeded in any other part of the world. King George VI is the only reigning monarch to have visited the island. This was in 1947 when the King, accompanied by Queen Elizabeth (later the Queen Mother), Princess Elizabeth (later Queen Elizabeth II) and Princess Margaret were travelling to South Africa. Prince Philip arrived at St Helena in 1957 and then his son Prince Andrew visited as a member of the armed forces in 1984 and his sister the Princess Royal arrived in 2002.


In 2012, the government of St. Helena funded the creation of the St. Helena Human Rights Action Plan 2012-2015. Work is being done under this action plan, including publishing awareness-raising articles in local newspapers, providing support for members of the public with human rights queries, and extending several UN Conventions on human rights to St. Helena.


In recent years[when?], there have been reports of child abuse in St Helena. Britain’s Foreign and Commonwealth Office (FCO) has been accused of lying to the United Nations about child abuse in St Helena to cover up allegations, including cases of a police officer having raped a four-year-old girl and of a police officer having mutilated a two-year-old.


St Helena has long been known for its high proportion of endemic birds and vascular plants. The highland areas contain most of the 400 endemic species recognised to date. Much of the island has been identified by BirdLife International as being important for bird conservation, especially the endemic Saint Helena plover or wirebird, and for seabirds breeding on the offshore islets and stacks, in the north-east and the south-west Important Bird Areas. On the basis of these endemics and an exceptional range of habitats, Saint Helena is on the United Kingdom's tentative list for future UNESCO World Heritage Sites.


St Helena's biodiversity, however, also includes marine vertebrates, invertebrates (freshwater, terrestrial and marine), fungi (including lichen-forming species), non-vascular plants, seaweeds and other biological groups. To date, very little is known about these, although more than 200 lichen-forming fungi have been recorded, including 9 endemics, suggesting that many significant discoveries remain to be made.


The island had a monocrop economy until 1966, based on the cultivation and processing of New Zealand flax for rope and string. St Helena's economy is now weak, and is almost entirely sustained by aid from the British government. The public sector dominates the economy, accounting for about 50% of gross domestic product. Inflation was running at 4% in 2005. There have been increases in the cost of fuel, power and all imported goods.


The tourist industry is heavily based on the promotion of Napoleon's imprisonment. A golf course also exists and the possibility for sportfishing tourism is great. Three hotels operate on the island but the arrival of tourists is directly linked to the arrival and departure schedule of the RMS St Helena. Some 3,200 short-term visitors arrived on the island in 2013.


Saint Helena produces what is said to be the most expensive coffee in the world. It also produces and exports Tungi Spirit, made from the fruit of the prickly or cactus pears, Opuntia ficus-indica ("Tungi" is the local St Helenian name for the plant). Ascension Island, Tristan da Cunha and Saint Helena all issue their own postage stamps which provide a significant income.


Quoted at constant 2002 prices, GDP fell from £12 million in 1999-2000 to £11 million in 2005-06. Imports are mainly from the UK and South Africa and amounted to £6.4 million in 2004-05 (quoted on an FOB basis). Exports are much smaller, amounting to £0.2 million in 2004-05. Exports are mainly fish and coffee; Philatelic sales were £0.06 million in 2004-05. The limited number of visiting tourists spent about £0.4 million in 2004-05, representing a contribution to GDP of 3%.


Public expenditure rose from £10 million in 2001-02 to £12 million in 2005-06 to £28m in 2012-13. The contribution of UK budgetary aid to total SHG government expenditure rose from £4.6 million in to £6.4 million to £12.1 million over the same period. Wages and salaries represent about 38% of recurrent expenditure.


Unemployment levels are low (31 individuals in 2013, compared to 50 in 2004 and 342 in 1998). Employment is dominated by the public sector, the number of government positions has fallen from 1,142 in 2006 to just over 800 in 2013. St Helena’s private sector employs approximately 45% of the employed labour force and is largely dominated by small and micro businesses with 218 private businesses employing 886 in 2004.


Household survey results suggest the percentage of households spending less than £20 per week on a per capita basis fell from 27% to 8% between 2000 and 2004, implying a decline in income poverty. Nevertheless, 22% of the population claimed social security benefit in 2006/7, most of them aged over 60, a sector that represents 20% of the population.


In 1821, Saul Solomon issued a 70,560 copper tokens worth a halfpenny each Payable at St Helena by Solomon, Dickson and Taylor – presumably London partners – that circulated alongside the East India Company's local coinage until the Crown took over the island in 1836. The coin remains readily available to collectors.


Today Saint Helena has its own currency, the Saint Helena pound, which is at parity with the pound sterling. The government of Saint Helena produces its own coinage and banknotes. The Bank of Saint Helena was established on Saint Helena and Ascension Island in 2004. It has branches in Jamestown on Saint Helena, and Georgetown, Ascension Island and it took over the business of the St. Helena government savings bank and Ascension Island Savings Bank.


Saint Helena is one of the most remote islands in the world, has one commercial airport under construction, and travel to the island is by ship only. A large military airfield is located on Ascension Island, with two Friday flights to RAF Brize Norton, England (as from September 2010). These RAF flights offer a limited number of seats to civilians.


The ship RMS Saint Helena runs between St Helena and Cape Town on a 5-day voyage, also visiting Ascension Island and Walvis Bay, and occasionally voyaging north to Tenerife and Portland, UK. It berths in James Bay, St Helena approximately thirty times per year. The RMS Saint Helena was due for decommissioning in 2010. However, its service life has been extended indefinitely until the airport is completed.


After a long period of rumour and consultation, the British government announced plans to construct an airport in Saint Helena in March 2005. The airport was expected to be completed by 2010. However an approved bidder, the Italian firm Impregilo, was not chosen until 2008, and then the project was put on hold in November 2008, allegedly due to new financial pressures brought on by the Financial crisis of 2007–2010. By January 2009, construction had not commenced and no final contracts had been signed. Governor Andrew Gurr departed for London in an attempt to speed up the process and solve the problems.


On 22 July 2010, the British government agreed to help pay for the new airport using taxpayer money. In November 2011 a new deal between the British government and South African civil engineering company Basil Read was signed and the airport was scheduled to open in February 2016, with flights to and from South Africa and the UK. In March 2015 South African airline Comair became the preferred bidder to provide weekly air service between the island and Johannesburg, starting from 2016.


The first aircraft, a South African Beechcraft King Air 200, landed at the new airport on 15 September 2015, prior to conducting a series of flights to calibrate the airport's radio navigation equipment.


The first helicopter landing at the new airfield was conducted by the Wildcat HMA.2 ZZ377 from 825 Squadron 201 Flight, embarked on visiting HMS Lancaster on 23 October 2015.


A minibus offers a basic service to carry people around Saint Helena, with most services designed to take people into Jamestown for a few hours on weekdays to conduct their business. Car hire is available for visitors.


Radio St Helena, which started operations on Christmas Day 1967, provided a local radio service that had a range of about 100 km (62 mi) from the island, and also broadcast internationally on shortwave radio (11092.5 kHz) on one day a year. The station presented news, features and music in collaboration with its sister newspaper, the St Helena Herald. It closed on 25 December 2012 to make way for a new three-channel FM service, also funded by St. Helena Government and run by the South Atlantic Media Services (formerly St. Helena Broadcasting (Guarantee) Corporation).


Saint FM provided a local radio service for the island which was also available on internet radio and relayed in Ascension Island. The station was not government funded. It was launched in January 2005 and closed on 21 December 2012. It broadcast news, features and music in collaboration with its sister newspaper, the St Helena Independent (which continues).


Saint FM Community Radio took over the radio channels vacated by Saint FM and launched on 10 March 2013. The station operates as a limited-by-guarantee company owned by its members and is registered as a fund-raising Association. Membership is open to everyone, and grants access to a live audio stream.


St Helena Online is a not-for-profit internet news service run from the UK by a former print and BBC journalist, working in partnership with Saint FM and the St Helena Independent.


Sure South Atlantic Ltd ("Sure") offers television for the island via 17 analogue terrestrial UHF channels, offering a mix of British, US, and South African programming. The channels are from DSTV and include Mnet, SuperSport and BBC channels. The feed signal, from MultiChoice DStv in South Africa, is received by a satellite dish at Bryant's Beacon from Intelsat 7 in the Ku band.


SURE provide the telecommunications service in the territory through a digital copper-based telephone network including ADSL-broadband service. In August 2011 the first fibre-optic link has been installed on the island, which connects the television receive antennas at Bryant's Beacon to the Cable & Wireless Technical Centre in the Briars.


A satellite ground station with a 7.6-metre (25 ft) satellite dish installed in 1989 at The Briars is the only international connection providing satellite links through Intelsat 707 to Ascension island and the United Kingdom. Since all international telephone and internet communications are relying on this single satellite link both internet and telephone service are subject to sun outages.


Saint Helena has the international calling code +290 which, since 2006, Tristan da Cunha shares. Saint Helena telephone numbers changed from 4 to 5 digits on 1 October 2013 by being prefixed with the digit "2", i.e. 2xxxx, with the range 5xxxx being reserved for mobile numbering, and 8xxx being used for Tristan da Cunha numbers (these still shown as 4 digits).


Saint Helena has a 10/3.6 Mbit/s internet link via Intelsat 707 provided by SURE. Serving a population of more than 4,000, this single satellite link is considered inadequate in terms of bandwidth.


ADSL-broadband service is provided with maximum speeds of up to 1536 KBit/s downstream and 512 KBit/s upstream offered on contract levels from lite £16 per month to gold+ at £190 per month. There are a few public WiFi hotspots in Jamestown, which are also being operated by SURE (formerly Cable & Wireless).


The South Atlantic Express, a 10,000 km (6,214 mi) submarine communications cable connecting Africa to South America, run by the undersea fibre optic provider eFive, will pass St Helena relatively closely. There were no plans to land the cable and install a landing station ashore, which could supply St Helena's population with sufficient bandwidth to fully leverage the benefits of today's Information Society. In January 2012, a group of supporters petitioned the UK government to meet the cost of landing the cable at St Helena. On 6 October 2012, eFive agreed to reroute the cable through St. Helena after a successful lobbying campaign by A Human Right, a San Francisco-based NGA working on initiatives to ensure all people are connected to the Internet. Islanders have sought the assistance of the UK Department for International Development and Foreign and Commonwealth Office in funding the £10m required to bridge the connection from a local junction box on the cable to the island. The UK Government have announced that a review of the island's economy would be required before such funding would be agreed to.


The island has two local newspapers, both of which are available on the Internet. The St Helena Independent has been published since November 2005. The Sentinel newspaper was introduced in 2012.


Education is free and compulsory between the ages of 5 and 16  The island has three primary schools for students of age 4 to 11: Harford, Pilling, and St Paul’s. Prince Andrew School provides secondary education for students aged 11 to 18. At the beginning of the academic year 2009-10, 230 students were enrolled in primary school and 286 in secondary school.


The Education and Employment Directorate also offers programmes for students with special needs, vocational training, adult education, evening classes, and distance learning. The island has a public library (the oldest in the Southern Hemisphere) and a mobile library service which operates weekly rural areas.


The UK national curriculum is adapted for local use. A range of qualifications are offered – from GCSE, A/S and A2, to Level 3 Diplomas and VRQ qualifications:


Sports played on the island include football, cricket, volleyball, tennis, golf, motocross, shooting sports and yachting. Saint Helena has sent teams to a number of Commonwealth Games. Saint Helena is a member of the International Island Games Association. The Saint Helena cricket team made its debut in international cricket in Division Three of the African region of the World Cricket League in 2011.


The Governor's Cup is a yacht race between Cape Town and Saint Helena island, held every two years in December/January; the most recent event was in December 2010. In Jamestown a timed run takes place up Jacob's Ladder every year, with people coming from all over the world to take part.


There are scouting and guiding groups on Saint Helena and Ascension Island. Scouting was established on Saint Helena island in 1912. Lord and Lady Baden-Powell visited the Scouts on Saint Helena on the return from their 1937 tour of Africa. The visit is described in Lord Baden-Powell's book entitled African Adventures.


In phonetics, aspiration is the strong burst of breath that accompanies either the release or, in the case of preaspiration, the closure of some obstruents. In English, aspirated consonants are allophones in complementary distribution with their unaspirated counterparts, but in some other languages, notably most Indian and East Asian languages, the difference is contrastive.


To feel or see the difference between aspirated and unaspirated sounds, one can put a hand or a lit candle in front of one's mouth, and say pin [pʰɪn] and then spin [spɪn]. One should either feel a puff of air or see a flicker of the candle flame with pin that one does not get with spin. In most dialects of English, the initial consonant is aspirated in pin and unaspirated in spin.


In the International Phonetic Alphabet (IPA), aspirated consonants are written using the symbols for voiceless consonants followed by the aspiration modifier letter ⟨◌ʰ⟩, a superscript form of the symbol for the voiceless glottal fricative ⟨h⟩. For instance, ⟨p⟩ represents the voiceless bilabial stop, and ⟨pʰ⟩ represents the aspirated bilabial stop.


Voiced consonants are seldom actually aspirated. Symbols for voiced consonants followed by ⟨◌ʰ⟩, such as ⟨bʰ⟩, typically represent consonants with breathy voiced release (see below). In the grammatical tradition of Sanskrit, aspirated consonants are called voiceless aspirated, and breathy-voiced consonants are called voiced aspirated.


There are no dedicated IPA symbols for degrees of aspiration and typically only two degrees are marked: unaspirated ⟨k⟩ and aspirated ⟨kʰ⟩. An old symbol for light aspiration was ⟨ʻ⟩, but this is now obsolete. The aspiration modifier letter may be doubled to indicate especially strong or long aspiration. Hence, the two degrees of aspiration in Korean stops are sometimes transcribed ⟨kʰ kʰʰ⟩ or ⟨kʻ⟩ and ⟨kʰ⟩, but they are usually transcribed [k] and [kʰ], with the details of voice-onset time given numerically.


Preaspirated consonants are marked by placing the aspiration modifier letter before the consonant symbol: ⟨ʰp⟩ represents the preaspirated bilabial stop.


Unaspirated or tenuis consonants are occasionally marked with the modifier letter for unaspiration ⟨◌˭⟩, a superscript equal sign: ⟨t˭⟩. Usually, however, unaspirated consonants are left unmarked: ⟨t⟩.


Voiceless consonants are produced with the vocal folds open (spread) and not vibrating, and voiced consonants are produced when the vocal folds are fractionally closed and vibrating (modal voice). Voiceless aspiration occurs when the vocal cords remain open after a consonant is released. An easy way to measure this is by noting the consonant's voice-onset time, as the voicing of a following vowel cannot begin until the vocal cords close.


Phonetically in some languages, such as Navajo, aspiration of stops tends to be realised as voiceless velar airflow; aspiration of affricates is realised as an extended length of the frication.


Aspirated consonants are not always followed by vowels or other voiced sounds. For example, in Eastern Armenian, aspiration is contrastive even word-finally, and aspirated consonants occur in consonant clusters. In Wahgi, consonants are aspirated only in final position.


Armenian and Cantonese have aspiration that lasts about as long as English aspirated stops, in addition to unaspirated stops. Korean has lightly aspirated stops that fall between the Armenian and Cantonese unaspirated and aspirated stops as well as strongly aspirated stops whose aspiration lasts longer than that of Armenian or Cantonese. (See voice-onset time.)


Aspiration varies with place of articulation. The Spanish voiceless stops /p t k/ have voice-onset times (VOTs) of about 5, 10, and 30 milliseconds, whereas English aspirated /p t k/ have VOTs of about 60, 70, and 80 ms. Voice-onset time in Korean has been measured at 20, 25, and 50 ms for /p t k/ and 90, 95, and 125 for /pʰ tʰ kʰ/.


When aspirated consonants are doubled or geminated, the stop is held longer and then has an aspirated release. An aspirated affricate consists of a stop, fricative, and aspirated release. A doubled aspirated affricate has a longer hold in the stop portion and then has a release consisting of the fricative and aspiration.


Icelandic and Faroese have preaspirated [ʰp ʰt ʰk]; some scholars interpret these as consonant clusters as well. In Icelandic, preaspirated stops contrast with double stops and single stops:


Preaspirated stops also occur in most Sami languages; for example, in North Sami, the unvoiced stop and affricate phonemes /p/, /t/, /ts/, /tʃ/, /k/ are pronounced preaspirated ([ʰp], [ʰt] [ʰts], [ʰtʃ], [ʰk]) when they occur in medial or final position.


Although most aspirated obstruents in the world's language are stops and affricates, aspirated fricatives such as [sʰ], [fʰ] or [ɕʰ] have been documented in Korean, in a few Tibeto-Burman languages, in some Oto-Manguean languages, and in the Siouan language Ofo. Some languages, such as Choni Tibetan, have up to four contrastive aspirated fricatives [sʰ] [ɕʰ], [ʂʰ] and [xʰ].


True aspirated voiced consonants, as opposed to murmured (breathy-voice) consonants such as the [bʱ], [dʱ], [ɡʱ] that are common in the languages of India, are extremely rare. They have been documented in Kelabit Taa, and the Kx'a languages. Reported aspirated voiced stops, affricates and clicks are [b͡pʰ, d͡tʰ, d͡tsʰ, d͡tʃʰ, ɡ͡kʰ, ɢ͡qʰ, ᶢʘʰ, ᶢǀʰ, ᶢǁʰ, ᶢǃʰ, ᶢǂʰ].


Aspiration has varying significance in different languages. It is either allophonic or phonemic, and may be analyzed as an underlying consonant cluster.


In some languages, such as English, aspiration is allophonic. Stops are distinguished primarily by voicing, and voiceless stops are sometimes aspirated, while voiced stops are usually unaspirated.


They are unaspirated for almost all speakers when immediately following word-initial s, as in spill, still, skill. After an s elsewhere in a word they are normally unaspirated as well, except sometimes in compound words. When the consonants in a cluster like st are analyzed as belonging to different morphemes (heteromorphemic) the stop is aspirated, but when they are analyzed as belonging to one morpheme the stop is unaspirated.[citation needed] For instance, distend has unaspirated [t] since it is not analyzed as two morphemes, but distaste has an aspirated middle [tʰ] because it is analyzed as dis- + taste and the word taste has an aspirated initial t.


In many languages, such as Armenian, Korean, Thai, Indo-Aryan languages, Dravidian languages, Icelandic, Ancient Greek, and the varieties of Chinese, tenuis and aspirated consonants are phonemic. Unaspirated consonants like [p˭ s˭] and aspirated consonants like [pʰ ʰp sʰ] are separate phonemes, and words are distinguished by whether they have one or the other.


In Danish and most southern varieties of German, the "lenis" consonants transcribed for historical reasons as ⟨b d ɡ⟩ are distinguished from their fortis counterparts ⟨p t k⟩, mainly in their lack of aspiration.


Standard Chinese (Mandarin) has stops and affricates distinguished by aspiration: for instance, /t tʰ/, /t͡s t͡sʰ/. In pinyin, tenuis stops are written with letters that represent voiced consonants in English, and aspirated stops with letters that represent voiceless consonants. Thus d represents /t/, and t represents /tʰ/.


Wu Chinese has a three-way distinction in stops and affricates: /p pʰ b/. In addition to aspirated and unaspirated consonants, there is a series of muddy consonants, like /b/. These are pronounced with slack or breathy voice: that is, they are weakly voiced. Muddy consonants as initial cause a syllable to be pronounced with low pitch or light (陽 yáng) tone.


Many Indo-Aryan languages have aspirated stops. Sanskrit, Hindi, Bengali, Marathi, and Gujarati have a four-way distinction in stops: voiceless, aspirated, voiced, and breathy-voiced or voiced aspirated, such as /p pʰ b bʱ/. Punjabi has lost breathy-voiced consonants, which resulted in a tone system, and therefore has a distinction between voiceless, aspirated, and voiced: /p pʰ b/.


Some of the Dravidian languages, such as Telugu, Tamil, Malayalam, and Kannada, have a distinction between voiced and voiceless, aspirated and unaspirated only in loanwords from Indo-Aryan languages. In native Dravidian words, there is no distinction between these categories and stops are underspecified for voicing and aspiration.


Western Armenian has a two-way distinction between aspirated and voiced: /tʰ d/. Western Armenian aspirated /tʰ/ corresponds to Eastern Armenian aspirated /tʰ/ and voiced /d/, and Western voiced /d/ corresponds to Eastern voiceless /t/.


Some forms of Greek before the Koine Greek period are reconstructed as having aspirated stops. The Classical Attic dialect of Ancient Greek had a three-way distinction in stops like Eastern Armenian: /t tʰ d/. These stops were called ψιλά, δασέα, μέσα "thin, thick, middle" by Koine Greek grammarians.


There were aspirated stops at three places of articulation: labial, coronal, and velar /pʰ tʰ kʰ/. Earlier Greek, represented by Mycenaean Greek, likely had a labialized velar aspirated stop /kʷʰ/, which later became labial, coronal, or velar depending on dialect and phonetic environment.


The other Ancient Greek dialects, Ionic, Doric, Aeolic, and Arcadocypriot, likely had the same three-way distinction at one point, but Doric seems to have had a fricative in place of /tʰ/ in the Classical period, and the Ionic and Aeolic dialects sometimes lost aspiration (psilosis).


Later, during the Koine Greek period, the aspirated and voiceless stops /tʰ d/ of Attic Greek lenited to voiceless and voiced fricatives, yielding /θ ð/ in Medieval and Modern Greek.


The term aspiration sometimes refers to the sound change of debuccalization, in which a consonant is lenited (weakened) to become a glottal stop or fricative [ʔ h ɦ].


So-called voiced aspirated consonants are nearly always pronounced instead with breathy voice, a type of phonation or vibration of the vocal folds. The modifier letter ⟨◌ʰ⟩ after a voiced consonant actually represents a breathy-voiced or murmured dental stop, as with the "voiced aspirated" bilabial stop ⟨bʰ⟩ in the Indo-Aryan languages. This consonant is therefore more accurately transcribed as ⟨b̤⟩, with the diacritic for breathy voice, or with the modifier letter ⟨bʱ⟩, a superscript form of the symbol for the voiced glottal fricative ⟨ɦ⟩.


Some linguists restrict the double-dot subscript ⟨◌̤⟩ to murmured sonorants, such as vowels and nasals, which are murmured throughout their duration, and use the superscript hook-aitch ⟨◌ʱ⟩ for the breathy-voiced release of obstruents.


Hydrogen is a chemical element with chemical symbol H and atomic number 1. With an atomic weight of 7000100794000000000♠1.00794 u, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass.[note 1] Non-remnant stars are mainly composed of hydrogen in its plasma state. The most common isotope of hydrogen, termed protium (name rarely used, symbol 1H), has one proton and no neutrons.


The universal emergence of atomic hydrogen first occurred during the recombination epoch. At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H2. Since hydrogen readily forms covalent compounds with most non-metallic elements, most of the hydrogen on Earth exists in molecular forms such as in the form of water or organic compounds. Hydrogen plays a particularly important role in acid–base reactions as many acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a negative charge (i.e., anion) when it is known as a hydride, or as a positively charged (i.e., cation) species denoted by the symbol H+. The hydrogen cation is written as though composed of a bare proton, but in reality, hydrogen cations in ionic compounds are always more complex species than that would suggest. As the only neutral atom for which the Schrödinger equation can be solved analytically, study of the energetics and bonding of the hydrogen atom has played a key role in the development of quantum mechanics.


Hydrogen gas was first artificially produced in the early 16th century, via the mixing of metals with acids. In 1766–81, Henry Cavendish was the first to recognize that hydrogen gas was a discrete substance, and that it produces water when burned, a property which later gave it its name: in Greek, hydrogen means "water-former".


Industrial production is mainly from the steam reforming of natural gas, and less often from more energy-intensive hydrogen production methods like the electrolysis of water. Most hydrogen is employed near its production site, with the two largest uses being fossil fuel processing (e.g., hydrocracking) and ammonia production, mostly for the fertilizer market. Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks.


Hydrogen gas (dihydrogen or molecular hydrogen) is highly flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion for hydrogen is −286 kJ/mol:


Hydrogen gas forms explosive mixtures with air if it is 4–74% concentrated and with chlorine if it is 5–95% concentrated. The mixtures may be ignited by spark, heat or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C (932 °F). Pure hydrogen-oxygen flames emit ultraviolet light and with high oxygen mix are nearly invisible to the naked eye, as illustrated by the faint plume of the Space Shuttle Main Engine compared to the highly visible plume of a Space Shuttle Solid Rocket Booster. The detection of a burning hydrogen leak may require a flame detector; such leaks can be very dangerous. Hydrogen flames in other conditions are blue, resembling blue natural gas flames. The destruction of the Hindenburg airship was an infamous example of hydrogen combustion; the cause is debated, but the visible orange flames were the result of a rich mixture of hydrogen to oxygen combined with carbon compounds from the airship skin.


H2 reacts with every oxidizing element. Hydrogen can react spontaneously and violently at room temperature with chlorine and fluorine to form the corresponding hydrogen halides, hydrogen chloride and hydrogen fluoride, which are also potentially dangerous acids.


The energy levels of hydrogen can be calculated fairly accurately using the Bohr model of the atom, which conceptualizes the electron as "orbiting" the proton in analogy to the Earth's orbit of the Sun. However, the electromagnetic force attracts electrons and protons to one another, while planets and celestial objects are attracted to each other by gravity. Because of the discretization of angular momentum postulated in early quantum mechanics by Bohr, the electron in the Bohr model can only occupy certain allowed distances from the proton, and therefore only certain allowed energies.


A more accurate description of the hydrogen atom comes from a purely quantum mechanical treatment that uses the Schrödinger equation, Dirac equation or even the Feynman path integral formulation to calculate the probability density of the electron around the proton. The most complicated treatments allow for the small effects of special relativity and vacuum polarization. In the quantum mechanical treatment, the electron in a ground state hydrogen atom has no angular momentum at all—an illustration of how the "planetary orbit" conception of electron motion differs from reality.


There exist two different spin isomers of hydrogen diatomic molecules that differ by the relative spin of their nuclei. In the orthohydrogen form, the spins of the two protons are parallel and form a triplet state with a molecular spin quantum number of 1 (1⁄2+1⁄2); in the parahydrogen form the spins are antiparallel and form a singlet with a molecular spin quantum number of 0 (1⁄2–1⁄2). At standard temperature and pressure, hydrogen gas contains about 25% of the para form and 75% of the ortho form, also known as the "normal form". The equilibrium ratio of orthohydrogen to parahydrogen depends on temperature, but because the ortho form is an excited state and has a higher energy than the para form, it is unstable and cannot be purified. At very low temperatures, the equilibrium state is composed almost exclusively of the para form. The liquid and gas phase thermal properties of pure parahydrogen differ significantly from those of the normal form because of differences in rotational heat capacities, as discussed more fully in spin isomers of hydrogen. The ortho/para distinction also occurs in other hydrogen-containing molecules or functional groups, such as water and methylene, but is of little significance for their thermal properties.


The uncatalyzed interconversion between para and ortho H2 increases with increasing temperature; thus rapidly condensed H2 contains large quantities of the high-energy ortho form that converts to the para form very slowly. The ortho/para ratio in condensed H2 is an important consideration in the preparation and storage of liquid hydrogen: the conversion from ortho to para is exothermic and produces enough heat to evaporate some of the hydrogen liquid, leading to loss of liquefied material. Catalysts for the ortho-para interconversion, such as ferric oxide, activated carbon, platinized asbestos, rare earth metals, uranium compounds, chromic oxide, or some nickel compounds, are used during hydrogen cooling.


While H2 is not very reactive under standard conditions, it does form compounds with most elements. Hydrogen can form compounds with elements that are more electronegative, such as halogens (e.g., F, Cl, Br, I), or oxygen; in these compounds hydrogen takes on a partial positive charge. When bonded to fluorine, oxygen, or nitrogen, hydrogen can participate in a form of medium-strength noncovalent bonding with other similar molecules between their hydrogens called hydrogen bonding, which is critical to the stability of many biological molecules. Hydrogen also forms compounds with less electronegative elements, such as the metals and metalloids, in which it takes on a partial negative charge. These compounds are often known as hydrides.


Hydrogen forms a vast array of compounds with carbon called the hydrocarbons, and an even vaster array with heteroatoms that, because of their general association with living things, are called organic compounds. The study of their properties is known as organic chemistry and their study in the context of living organisms is known as biochemistry. By some definitions, "organic" compounds are only required to contain carbon. However, most of them also contain hydrogen, and because it is the carbon-hydrogen bond which gives this class of compounds most of its particular chemical characteristics, carbon-hydrogen bonds are required in some definitions of the word "organic" in chemistry. Millions of hydrocarbons are known, and they are usually formed by complicated synthetic pathways, which seldom involve elementary hydrogen.


Compounds of hydrogen are often called hydrides, a term that is used fairly loosely. The term "hydride" suggests that the H atom has acquired a negative or anionic character, denoted H−, and is used when hydrogen forms a compound with a more electropositive element. The existence of the hydride anion, suggested by Gilbert N. Lewis in 1916 for group I and II salt-like hydrides, was demonstrated by Moers in 1920 by the electrolysis of molten lithium hydride (LiH), producing a stoichiometry quantity of hydrogen at the anode. For hydrides other than group I and II metals, the term is quite misleading, considering the low electronegativity of hydrogen. An exception in group II hydrides is BeH
2, which is polymeric. In lithium aluminium hydride, the AlH−
4 anion carries hydridic centers firmly attached to the Al(III).


Although hydrides can be formed with almost all main-group elements, the number and combination of possible compounds varies widely; for example, there are over 100 binary borane hydrides known, but only one binary aluminium hydride. Binary indium hydride has not yet been identified, although larger complexes exist.


In inorganic chemistry, hydrides can also serve as bridging ligands that link two metal centers in a coordination complex. This function is particularly common in group 13 elements, especially in boranes (boron hydrides) and aluminium complexes, as well as in clustered carboranes.


Oxidation of hydrogen removes its electron and gives H+, which contains no electrons and a nucleus which is usually composed of one proton. That is why H+ is often called a proton. This species is central to discussion of acids. Under the Bronsted-Lowry theory, acids are proton donors, while bases are proton acceptors.


A bare proton, H+, cannot exist in solution or in ionic crystals, because of its unstoppable attraction to other atoms or molecules with electrons. Except at the high temperatures associated with plasmas, such protons cannot be removed from the electron clouds of atoms and molecules, and will remain attached to them. However, the term 'proton' is sometimes used loosely and metaphorically to refer to positively charged or cationic hydrogen attached to other species in this fashion, and as such is denoted "H+" without any implication that any single protons exist freely as a species.


To avoid the implication of the naked "solvated proton" in solution, acidic aqueous solutions are sometimes considered to contain a less unlikely fictitious species, termed the "hydronium ion" (H
3O+). However, even in this case, such solvated hydrogen cations are more realistically conceived as being organized into clusters that form species closer to H
9O+
4. Other oxonium ions are found when water is in acidic solution with other solvents.


Although exotic on Earth, one of the most common ions in the universe is the H+
3 ion, known as protonated molecular hydrogen or the trihydrogen cation.


Hydrogen has three naturally occurring isotopes, denoted 1H, 2H and 3H. Other, highly unstable nuclei (4H to 7H) have been synthesized in the laboratory but not observed in nature.


Hydrogen is the only element that has different names for its isotopes in common use today. During the early study of radioactivity, various heavy radioactive isotopes were given their own names, but such names are no longer used, except for deuterium and tritium. The symbols D and T (instead of 2H and 3H) are sometimes used for deuterium and tritium, but the corresponding symbol for protium, P, is already in use for phosphorus and thus is not available for protium. In its nomenclatural guidelines, the International Union of Pure and Applied Chemistry allows any of D, T, 2H, and 3H to be used, although 2H and 3H are preferred.


In 1671, Robert Boyle discovered and described the reaction between iron filings and dilute acids, which results in the production of hydrogen gas. In 1766, Henry Cavendish was the first to recognize hydrogen gas as a discrete substance, by naming the gas from a metal-acid reaction "flammable air". He speculated that "flammable air" was in fact identical to the hypothetical substance called "phlogiston" and further finding in 1781 that the gas produces water when burned. He is usually given credit for its discovery as an element. In 1783, Antoine Lavoisier gave the element the name hydrogen (from the Greek ὑδρο- hydro meaning "water" and -γενής genes meaning "creator") when he and Laplace reproduced Cavendish's finding that water is produced when hydrogen is burned.


Lavoisier produced hydrogen for his experiments on mass conservation by reacting a flux of steam with metallic iron through an incandescent iron tube heated in a fire. Anaerobic oxidation of iron by the protons of water at high temperature can be schematically represented by the set of following reactions:


Hydrogen was liquefied for the first time by James Dewar in 1898 by using regenerative cooling and his invention, the vacuum flask. He produced solid hydrogen the next year. Deuterium was discovered in December 1931 by Harold Urey, and tritium was prepared in 1934 by Ernest Rutherford, Mark Oliphant, and Paul Harteck. Heavy water, which consists of deuterium in the place of regular hydrogen, was discovered by Urey's group in 1932. François Isaac de Rivaz built the first de Rivaz engine, an internal combustion engine powered by a mixture of hydrogen and oxygen in 1806. Edward Daniel Clarke invented the hydrogen gas blowpipe in 1819. The Döbereiner's lamp and limelight were invented in 1823.


The first hydrogen-filled balloon was invented by Jacques Charles in 1783. Hydrogen provided the lift for the first reliable form of air-travel following the 1852 invention of the first hydrogen-lifted airship by Henri Giffard. German count Ferdinand von Zeppelin promoted the idea of rigid airships lifted by hydrogen that later were called Zeppelins; the first of which had its maiden flight in 1900. Regularly scheduled flights started in 1910 and by the outbreak of World War I in August 1914, they had carried 35,000 passengers without a serious incident. Hydrogen-lifted airships were used as observation platforms and bombers during the war.


The first non-stop transatlantic crossing was made by the British airship R34 in 1919. Regular passenger service resumed in the 1920s and the discovery of helium reserves in the United States promised increased safety, but the U.S. government refused to sell the gas for this purpose. Therefore, H2 was used in the Hindenburg airship, which was destroyed in a midair fire over New Jersey on 6 May 1937. The incident was broadcast live on radio and filmed. Ignition of leaking hydrogen is widely assumed to be the cause, but later investigations pointed to the ignition of the aluminized fabric coating by static electricity. But the damage to hydrogen's reputation as a lifting gas was already done.


In the same year the first hydrogen-cooled turbogenerator went into service with gaseous hydrogen as a coolant in the rotor and the stator in 1937 at Dayton, Ohio, by the Dayton Power & Light Co.; because of the thermal conductivity of hydrogen gas, this is the most common type in its field today.


The nickel hydrogen battery was used for the first time in 1977 aboard the U.S. Navy's Navigation technology satellite-2 (NTS-2). For example, the ISS, Mars Odyssey and the Mars Global Surveyor are equipped with nickel-hydrogen batteries. In the dark part of its orbit, the Hubble Space Telescope is also powered by nickel-hydrogen batteries, which were finally replaced in May 2009, more than 19 years after launch, and 13 years over their design life.


Because of its simple atomic structure, consisting only of a proton and an electron, the hydrogen atom, together with the spectrum of light produced from it or absorbed by it, has been central to the development of the theory of atomic structure. Furthermore, the corresponding simplicity of the hydrogen molecule and the corresponding cation H+
2 allowed fuller understanding of the nature of the chemical bond, which followed shortly after the quantum mechanical treatment of the hydrogen atom had been developed in the mid-1920s.


One of the first quantum effects to be explicitly noticed (but not understood at the time) was a Maxwell observation involving hydrogen, half a century before full quantum mechanical theory arrived. Maxwell observed that the specific heat capacity of H2 unaccountably departs from that of a diatomic gas below room temperature and begins to increasingly resemble that of a monatomic gas at cryogenic temperatures. According to quantum theory, this behavior arises from the spacing of the (quantized) rotational energy levels, which are particularly wide-spaced in H2 because of its low mass. These widely spaced levels inhibit equal partition of heat energy into rotational motion in hydrogen at low temperatures. Diatomic gases composed of heavier atoms do not have such widely spaced levels and do not exhibit the same effect.


Hydrogen, as atomic H, is the most abundant chemical element in the universe, making up 75% of normal matter by mass and over 90% by number of atoms (most of the mass of the universe, however, is not in the form of chemical-element type matter, but rather is postulated to occur as yet-undetected forms of mass such as dark matter and dark energy). This element is found in great abundance in stars and gas giant planets. Molecular clouds of H2 are associated with star formation. Hydrogen plays a vital role in powering stars through the proton-proton reaction and the CNO cycle nuclear fusion.


Throughout the universe, hydrogen is mostly found in the atomic and plasma states whose properties are quite different from molecular hydrogen. As a plasma, hydrogen's electron and proton are not bound together, resulting in very high electrical conductivity and high emissivity (producing the light from the Sun and other stars). The charged particles are highly influenced by magnetic and electric fields. For example, in the solar wind they interact with the Earth's magnetosphere giving rise to Birkeland currents and the aurora. Hydrogen is found in the neutral atomic state in the interstellar medium. The large amount of neutral hydrogen found in the damped Lyman-alpha systems is thought to dominate the cosmological baryonic density of the Universe up to redshift z=4.


Under ordinary conditions on Earth, elemental hydrogen exists as the diatomic gas, H2. However, hydrogen gas is very rare in the Earth's atmosphere (1 ppm by volume) because of its light weight, which enables it to escape from Earth's gravity more easily than heavier gases. However, hydrogen is the third most abundant element on the Earth's surface, mostly in the form of chemical compounds such as hydrocarbons and water. Hydrogen gas is produced by some bacteria and algae and is a natural component of flatus, as is methane, itself a hydrogen source of increasing importance.


A molecular form called protonated molecular hydrogen (H+
3) is found in the interstellar medium, where it is generated by ionization of molecular hydrogen from cosmic rays. This charged ion has also been observed in the upper atmosphere of the planet Jupiter. The ion is relatively stable in the environment of outer space due to the low temperature and density. H+
3 is one of the most abundant ions in the Universe, and it plays a notable role in the chemistry of the interstellar medium. Neutral triatomic hydrogen H3 can only exist in an excited form and is unstable. By contrast, the positive hydrogen molecular ion (H+
2) is a rare molecule in the universe.


H
2 is produced in chemistry and biology laboratories, often as a by-product of other reactions; in industry for the hydrogenation of unsaturated substrates; and in nature as a means of expelling reducing equivalents in biochemical reactions.


The electrolysis of water is a simple method of producing hydrogen. A low voltage current is run through the water, and gaseous oxygen forms at the anode while gaseous hydrogen forms at the cathode. Typically the cathode is made from platinum or another inert metal when producing hydrogen for storage. If, however, the gas is to be burnt on site, oxygen is desirable to assist the combustion, and so both electrodes would be made from inert metals. (Iron, for instance, would oxidize, and thus decrease the amount of oxygen given off.) The theoretical maximum efficiency (electricity used vs. energetic value of hydrogen produced) is in the range 80–94%.


An alloy of aluminium and gallium in pellet form added to water can be used to generate hydrogen. The process also produces alumina, but the expensive gallium, which prevents the formation of an oxide skin on the pellets, can be re-used. This has important potential implications for a hydrogen economy, as hydrogen can be produced on-site and does not need to be transported.


Hydrogen can be prepared in several different ways, but economically the most important processes involve removal of hydrogen from hydrocarbons. Commercial bulk hydrogen is usually produced by the steam reforming of natural gas. At high temperatures (1000–1400 K, 700–1100 °C or 1300–2000 °F), steam (water vapor) reacts with methane to yield carbon monoxide and H
2.


This reaction is favored at low pressures but is nonetheless conducted at high pressures (2.0  MPa, 20 atm or 600 inHg). This is because high-pressure H
2 is the most marketable product and Pressure Swing Adsorption (PSA) purification systems work better at higher pressures. The product mixture is known as "synthesis gas" because it is often used directly for the production of methanol and related compounds. Hydrocarbons other than methane can be used to produce synthesis gas with varying product ratios. One of the many complications to this highly optimized technology is the formation of coke or carbon:


Consequently, steam reforming typically employs an excess of H
2O. Additional hydrogen can be recovered from the steam by use of carbon monoxide through the water gas shift reaction, especially with an iron oxide catalyst. This reaction is also a common industrial source of carbon dioxide:


Hydrogen is sometimes produced and consumed in the same industrial process, without being separated. In the Haber process for the production of ammonia, hydrogen is generated from natural gas. Electrolysis of brine to yield chlorine also produces hydrogen as a co-product.


There are more than 200 thermochemical cycles which can be used for water splitting, around a dozen of these cycles such as the iron oxide cycle, cerium(IV) oxide–cerium(III) oxide cycle, zinc zinc-oxide cycle, sulfur-iodine cycle, copper-chlorine cycle and hybrid sulfur cycle are under research and in testing phase to produce hydrogen and oxygen from water and heat without using electricity. A number of laboratories (including in France, Germany, Greece, Japan, and the USA) are developing thermochemical methods to produce hydrogen from solar energy and water.


Under anaerobic conditions, iron and steel alloys are slowly oxidized by the protons of water concomitantly reduced in molecular hydrogen (H
2). The anaerobic corrosion of iron leads first to the formation of ferrous hydroxide (green rust) and can be described by the following reaction:


In its turn, under anaerobic conditions, the ferrous hydroxide (Fe(OH)
2 ) can be oxidized by the protons of water to form magnetite and molecular hydrogen. This process is described by the Schikorr reaction:


In the absence of atmospheric oxygen (O
2), in deep geological conditions prevailing far away from Earth atmosphere, hydrogen (H
2) is produced during the process of serpentinization by the anaerobic oxidation by the water protons (H+) of the ferrous (Fe2+) silicate present in the crystal lattice of the fayalite (Fe
2SiO
4, the olivine iron-endmember). The corresponding reaction leading to the formation of magnetite (Fe
3O
4), quartz (SiO
2) and hydrogen (H
2) is the following:


From all the fault gases formed in power transformers, hydrogen is the most common and is generated under most fault conditions; thus, formation of hydrogen is an early indication of serious problems in the transformer's life cycle.


Large quantities of H
2 are needed in the petroleum and chemical industries. The largest application of H
2 is for the processing ("upgrading") of fossil fuels, and in the production of ammonia. The key consumers of H
2 in the petrochemical plant include hydrodealkylation, hydrodesulfurization, and hydrocracking. H
2 has several other important uses. H
2 is used as a hydrogenating agent, particularly in increasing the level of saturation of unsaturated fats and oils (found in items such as margarine), and in the production of methanol. It is similarly the source of hydrogen in the manufacture of hydrochloric acid. H
2 is also used as a reducing agent of metallic ores.


Hydrogen is highly soluble in many rare earth and transition metals and is soluble in both nanocrystalline and amorphous metals. Hydrogen solubility in metals is influenced by local distortions or impurities in the crystal lattice. These properties may be useful when hydrogen is purified by passage through hot palladium disks, but the gas's high solubility is a metallurgical problem, contributing to the embrittlement of many metals, complicating the design of pipelines and storage tanks.


Apart from its use as a reactant, H
2 has wide applications in physics and engineering. It is used as a shielding gas in welding methods such as atomic hydrogen welding. H2 is used as the rotor coolant in electrical generators at power stations, because it has the highest thermal conductivity of any gas. Liquid H2 is used in cryogenic research, including superconductivity studies. Because H
2 is lighter than air, having a little more than 1⁄14 of the density of air, it was once widely used as a lifting gas in balloons and airships.


In more recent applications, hydrogen is used pure or mixed with nitrogen (sometimes called forming gas) as a tracer gas for minute leak detection. Applications can be found in the automotive, chemical, power generation, aerospace, and telecommunications industries. Hydrogen is an authorized food additive (E 949) that allows food package leak testing among other anti-oxidizing properties.


Hydrogen's rarer isotopes also each have specific applications. Deuterium (hydrogen-2) is used in nuclear fission applications as a moderator to slow neutrons, and in nuclear fusion reactions. Deuterium compounds have applications in chemistry and biology in studies of reaction isotope effects. Tritium (hydrogen-3), produced in nuclear reactors, is used in the production of hydrogen bombs, as an isotopic label in the biosciences, and as a radiation source in luminous paints.


Hydrogen is commonly used in power stations as a coolant in generators due to a number of favorable properties that are a direct result of its light diatomic molecules. These include low density, low viscosity, and the highest specific heat and thermal conductivity of all gases.


Hydrogen is not an energy resource, except in the hypothetical context of commercial nuclear fusion power plants using deuterium or tritium, a technology presently far from development. The Sun's energy comes from nuclear fusion of hydrogen, but this process is difficult to achieve controllably on Earth. Elemental hydrogen from solar, biological, or electrical sources require more energy to make it than is obtained by burning it, so in these cases hydrogen functions as an energy carrier, like a battery. Hydrogen may be obtained from fossil sources (such as methane), but these sources are unsustainable.


The energy density per unit volume of both liquid hydrogen and compressed hydrogen gas at any practicable pressure is significantly less than that of traditional fuel sources, although the energy density per unit fuel mass is higher. Nevertheless, elemental hydrogen has been widely discussed in the context of energy, as a possible future carrier of energy on an economy-wide scale. For example, CO
2 sequestration followed by carbon capture and storage could be conducted at the point of H
2 production from fossil fuels. Hydrogen used in transportation would burn relatively cleanly, with some NOx emissions, but without carbon emissions. However, the infrastructure costs associated with full conversion to a hydrogen economy would be substantial. Fuel cells can convert hydrogen and oxygen directly to electricity more efficiently than internal combustion engines.


Hydrogen is employed to saturate broken ("dangling") bonds of amorphous silicon and amorphous carbon that helps stabilizing material properties. It is also a potential electron donor in various oxide materials, including ZnO, SnO2, CdO, MgO, ZrO2, HfO2, La2O3, Y2O3, TiO2, SrTiO3, LaAlO3, SiO2, Al2O3, ZrSiO4, HfSiO4, and SrZrO3.


H2 is a product of some types of anaerobic metabolism and is produced by several microorganisms, usually via reactions catalyzed by iron- or nickel-containing enzymes called hydrogenases. These enzymes catalyze the reversible redox reaction between H2 and its component two protons and two electrons. Creation of hydrogen gas occurs in the transfer of reducing equivalents produced during pyruvate fermentation to water. The natural cycle of hydrogen production and consumption by organisms is called the hydrogen cycle.


Water splitting, in which water is decomposed into its component protons, electrons, and oxygen, occurs in the light reactions in all photosynthetic organisms. Some such organisms, including the alga Chlamydomonas reinhardtii and cyanobacteria, have evolved a second step in the dark reactions in which protons and electrons are reduced to form H2 gas by specialized hydrogenases in the chloroplast. Efforts have been undertaken to genetically modify cyanobacterial hydrogenases to efficiently synthesize H2 gas even in the presence of oxygen. Efforts have also been undertaken with genetically modified alga in a bioreactor.


Hydrogen poses a number of hazards to human safety, from potential detonations and fires when mixed with air to being an asphyxiant in its pure, oxygen-free form. In addition, liquid hydrogen is a cryogen and presents dangers (such as frostbite) associated with very cold liquids. Hydrogen dissolves in many metals, and, in addition to leaking out, may have adverse effects on them, such as hydrogen embrittlement, leading to cracks and explosions. Hydrogen gas leaking into external air may spontaneously ignite. Moreover, hydrogen fire, while being extremely hot, is almost invisible, and thus can lead to accidental burns.


Even interpreting the hydrogen data (including safety data) is confounded by a number of phenomena. Many physical and chemical properties of hydrogen depend on the parahydrogen/orthohydrogen ratio (it often takes days or weeks at a given temperature to reach the equilibrium ratio, for which the data is usually given). Hydrogen detonation parameters, such as critical detonation pressure and temperature, strongly depend on the container geometry.


The Space Race was a 20th-century competition between two Cold War rivals, the Soviet Union (USSR) and the United States (US), for supremacy in spaceflight capability. It had its origins in the missile-based nuclear arms race between the two nations that occurred following World War II, enabled by captured German rocket technology and personnel. The technological superiority required for such supremacy was seen as necessary for national security, and symbolic of ideological superiority. The Space Race spawned pioneering efforts to launch artificial satellites, unmanned space probes of the Moon, Venus, and Mars, and human spaceflight in low Earth orbit and to the Moon. The competition began on August 2, 1955, when the Soviet Union responded to the US announcement four days earlier of intent to launch artificial satellites for the International Geophysical Year, by declaring they would also launch a satellite "in the near future". The Soviet Union beat the US to this, with the October 4, 1957 orbiting of Sputnik 1, and later beat the US to the first human in space, Yuri Gagarin, on April 12, 1961. The Space Race peaked with the July 20, 1969 US landing of the first humans on the Moon with Apollo 11. The USSR tried but failed manned lunar missions, and eventually cancelled them and concentrated on Earth orbital space stations. A period of détente followed with the April 1972 agreement on a co-operative Apollo–Soyuz Test Project, resulting in the July 1975 rendezvous in Earth orbit of a US astronaut crew with a Soviet cosmonaut crew.


The Space Race can trace its origins to Germany, beginning in the 1930s and continuing during World War II when Nazi Germany researched and built operational ballistic missiles. Starting in the early 1930s, during the last stages of the Weimar Republic, German aerospace engineers experimented with liquid-fueled rockets, with the goal that one day they would be capable of reaching high altitudes and traversing long distances. The head of the German Army's Ballistics and Munitions Branch, Lieutenant Colonel Karl Emil Becker, gathered a small team of engineers that included Walter Dornberger and Leo Zanssen, to figure out how to use rockets as long-range artillery in order to get around the Treaty of Versailles' ban on research and development of long-range cannons. Wernher von Braun, a young engineering prodigy, was recruited by Becker and Dornberger to join their secret army program at Kummersdorf-West in 1932. Von Braun had dreams about conquering outer space with rockets, and did not initially see the military value in missile technology.


During the Second World War, General Dornberger was the military head of the army's rocket program, Zanssen became the commandant of the Peenemünde army rocket centre, and von Braun was the technical director of the ballistic missile program. They would lead the team that built the Aggregate-4 (A-4) rocket, which became the first vehicle to reach outer space during its test flight program in 1942 and 1943. By 1943, Germany began mass-producing the A-4 as the Vergeltungswaffe 2 ("Vengeance Weapon" 2, or more commonly, V2), a ballistic missile with a 320 kilometers (200 mi) range carrying a 1,130 kilograms (2,490 lb) warhead at 4,000 kilometers per hour (2,500 mph). Its supersonic speed meant there was no defense against it, and radar detection provided little warning. Germany used the weapon to bombard southern England and parts of Allied-liberated western Europe from 1944 until 1945. After the war, the V-2 became the basis of early American and Soviet rocket designs.


At war's end, American, British, and Soviet scientific intelligence teams competed to capture Germany's rocket engineers along with the German rockets themselves and the designs on which they were based. Each of the Allies captured a share of the available members of the German rocket team, but the United States benefited the most with Operation Paperclip, recruiting von Braun and most of his engineering team, who later helped develop the American missile and space exploration programs. The United States also acquired a large number of complete V2 rockets.


The German rocket center in Peenemünde was located in the eastern part of Germany, which became the Soviet zone of occupation. On Stalin's orders, the Soviet Union sent its best rocket engineers to this region to see what they could salvage for future weapons systems. The Soviet rocket engineers were led by Sergei Korolev. He had been involved in space clubs and early Soviet rocket design in the 1930s, but was arrested in 1938 during Joseph Stalin's Great Purge and imprisoned for six years in Siberia. After the war, he became the USSR's chief rocket and spacecraft engineer, essentially the Soviet counterpart to von Braun. His identity was kept a state secret throughout the Cold War, and he was identified publicly only as "the Chief Designer." In the West, his name was only officially revealed when he died in 1966.


After almost a year in the area around Peenemünde, Soviet officials moved most of the captured German rocket specialists to Gorodomlya Island on Lake Seliger, about 240 kilometers (150 mi) northwest of Moscow. They were not allowed to participate in Soviet missile design, but were used as problem-solving consultants to the Soviet engineers. They helped in the following areas: the creation of a Soviet version of the A-4; work on "organizational schemes"; research in improving the A-4 main engine; development of a 100-ton engine; assistance in the "layout" of plant production rooms; and preparation of rocket assembly using German components. With their help, particularly Helmut Groettrup's group, Korolev reverse-engineered the A-4 and built his own version of the rocket, the R-1, in 1948. Later, he developed his own distinct designs, though many of these designs were influenced by the Groettrup Group's G4-R10 design from 1949. The Germans were eventually repatriated in 1951–53.


The American professor Robert H. Goddard had worked on developing solid-fuel rockets since 1914, and demonstrated a light battlefield rocket to the US Army Signal Corps only five days before the signing of the armistice that ended World War I. He also started developing liquid-fueled rockets in 1921; yet he had not been taken seriously by the public, and was not sponsored by the government as part of the post-WW II rocket development effort. Von Braun, himself inspired by Goddard's work, was bemused by this when debriefed by his American handlers, asking them, "Why didn't you just ask Dr. Goddard?"[citation needed]


Von Braun and his team were sent to the United States Army's White Sands Proving Ground, located in New Mexico, in 1945. They set about assembling the captured V2s and began a program of launching them and instructing American engineers in their operation. These tests led to the first rocket to take photos from outer space, and the first two-stage rocket, the WAC Corporal-V2 combination, in 1949. The German rocket team was moved from Fort Bliss to the Army's new Redstone Arsenal, located in Huntsville, Alabama, in 1950. From here, von Braun and his team would develop the Army's first operational medium-range ballistic missile, the Redstone rocket, that would, in slightly modified versions, launch both America's first satellite, and the first piloted Mercury space missions. It became the basis for both the Jupiter and Saturn family of rockets.


In simple terms, the Cold War could be viewed as an expression of the ideological struggle between communism and capitalism. The United States faced a new uncertainty beginning in September 1949, when it lost its monopoly on the atomic bomb. American intelligence agencies discovered that the Soviet Union had exploded its first atomic bomb, with the consequence that the United States potentially could face a future nuclear war that, for the first time, might devastate its cities. Given this new danger, the United States participated in an arms race with the Soviet Union that included development of the hydrogen bomb, as well as intercontinental strategic bombers and intercontinental ballistic missiles (ICBMs) capable of delivering nuclear weapons. A new fear of communism and its sympathizers swept the United States during the 1950s, which devolved into paranoid McCarthyism. With communism spreading in China, Korea, and Eastern Europe, Americans came to feel so threatened that popular and political culture condoned extensive "witch-hunts" to expose communist spies. Part of the American reaction to the Soviet atomic and hydrogen bomb tests included maintaining a large Air Force, under the control of the Strategic Air Command (SAC). SAC employed intercontinental strategic bombers, as well as medium-bombers based close to Soviet airspace (in western Europe and in Turkey) that were capable of delivering nuclear payloads.


For its part, the Soviet Union harbored fears of invasion. Having suffered at least 27 million casualties during World War II after being invaded by Nazi Germany in 1941, the Soviet Union was wary of its former ally, the United States, which until late 1949 was the sole possessor of atomic weapons. The United States had used these weapons operationally during World War II, and it could use them again against the Soviet Union, laying waste its cities and military centers. Since the Americans had a much larger air force than the Soviet Union, and the United States maintained advance air bases near Soviet territory, in 1947 Stalin ordered the development of intercontinental ballistic missiles (ICBMs) in order to counter the perceived American threat.


In 1953, Korolev was given the go-ahead to develop the R-7 Semyorka rocket, which represented a major advance from the German design. Although some of its components (notably boosters) still resembled the German G-4, the new rocket incorporated staged design, a completely new control system, and a new fuel. It was successfully tested on August 21, 1957 and became the world's first fully operational ICBM the following month. It would later be used to launch the first satellite into space, and derivatives would launch all piloted Soviet spacecraft.


The United States had multiple rocket programs divided among the different branches of the American armed services, which meant that each force developed its own ICBM program. The Air Force initiated ICBM research in 1945 with the MX-774. However, its funding was cancelled and only three partially successful launches were conducted in 1947. In 1950, von Braun began testing the Air Force PGM-11 Redstone rocket family at Cape Canaveral. In 1951, the Air Force began a new ICBM program called MX-1593, and by 1955 this program was receiving top-priority funding. The MX-1593 program evolved to become the Atlas-A, with its maiden launch occurring June 11, 1957, becoming the first successful American ICBM. Its upgraded version, the Atlas-D rocket, would later serve as an operational nuclear ICBM and as the orbital launch vehicle for Project Mercury and the remote-controlled Agena Target Vehicle used in Project Gemini.


In 1955, with both the United States and the Soviet Union building ballistic missiles that could be utilized to launch objects into space, the "starting line" was drawn for the Space Race. In separate announcements, just four days apart, both nations publicly announced that they would launch artificial Earth satellites by 1957 or 1958. On July 29, 1955, James C. Hagerty, president Dwight D. Eisenhower's press secretary, announced that the United States intended to launch "small Earth circling satellites" between July 1, 1957, and December 31, 1958, as part of their contribution to the International Geophysical Year (IGY). Four days later, at the Sixth Congress of International Astronautical Federation in Copenhagen, scientist Leonid I. Sedov spoke to international reporters at the Soviet embassy, and announced his country's intention to launch a satellite as well, in the "near future". On August 30, 1955, Korolev managed to get the Soviet Academy of Sciences to create a commission whose purpose was to beat the Americans into Earth orbit: this was the de facto start date for the Space Race. The Council of Ministers of the Soviet Union began a policy of treating development of its space program as a classified state secret.


Initially, President Eisenhower was worried that a satellite passing above a nation at over 100 kilometers (62 mi), might be construed as violating that nation's sovereign airspace. He was concerned that the Soviet Union would accuse the Americans of an illegal overflight, thereby scoring a propaganda victory at his expense. Eisenhower and his advisors believed that a nation's airspace sovereignty did not extend into outer space, acknowledged as the Kármán line, and he used the 1957–58 International Geophysical Year launches to establish this principle in international law. Eisenhower also feared that he might cause an international incident and be called a "warmonger" if he were to use military missiles as launchers. Therefore, he selected the untried Naval Research Laboratory's Vanguard rocket, which was a research-only booster. This meant that von Braun's team was not allowed to put a satellite into orbit with their Jupiter-C rocket, because of its intended use as a future military vehicle. On September 20, 1956, von Braun and his team did launch a Jupiter-C that was capable of putting a satellite into orbit, but the launch was used only as a suborbital test of nose cone reentry technology.


The Soviet success caused public controversy in the United States, and Eisenhower ordered the civilian rocket and satellite project, Vanguard, to move up its timetable and launch its satellite much sooner than originally planned. The December 6, 1957 Project Vanguard launch failure occurred at Cape Canaveral Air Force Station in Florida, broadcast live in front of a US television audience. It was a monumental failure, exploding a few seconds after launch, and it became an international joke. The satellite appeared in newspapers under the names Flopnik, Stayputnik, Kaputnik, and Dudnik. In the United Nations, the Russian delegate offered the U.S. representative aid "under the Soviet program of technical assistance to backwards nations." Only in the wake of this very public failure did von Braun's Redstone team get the go-ahead to launch their Jupiter-C rocket as soon as they could. In Britain, the USA's Western Cold War ally, the reaction was mixed: some members of the population celebrated the fact that the Soviets had reached space first, while others feared the destructive potential that military uses of spacecraft might bring.


On January 31, 1958, nearly four months after the launch of Sputnik 1, von Braun and the United States successfully launched its first satellite on a four-stage Juno I rocket derived from the US Army's Redstone missile, at Cape Canaveral. The satellite Explorer 1 was 30.8 pounds (14.0 kg) in mass. It carried a micrometeorite gauge and a Geiger-Müller tube. It passed in and out of the Earth-encompassing radiation belt with its 194-by-1,368-nautical-mile (360 by 2,534 km) orbit, therefore saturating the tube's capacity and proving what Dr. James Van Allen, a space scientist at the University of Iowa, had theorized. The belt, named the Van Allen radiation belt, is a doughnut-shaped zone of high-level radiation intensity around the Earth above the magnetic equator. Van Allen was also the man who designed and built the satellite instrumentation of Explorer 1. The satellite actually measured three phenomena: cosmic ray and radiation levels, the temperature in the spacecraft, and the frequency of collisions with micrometeorites. The satellite had no memory for data storage, therefore it had to transmit continuously. Two months later in March 1958, a second satellite was sent into orbit with augmented cosmic ray instruments.


On April 2, 1958, President Eisenhower reacted to the Soviet space lead in launching the first satellite, by recommending to the US Congress that a civilian agency be established to direct nonmilitary space activities. Congress, led by Senate Majority Leader Lyndon B. Johnson, responded by passing the National Aeronautics and Space Act, which Eisenhower signed into law on July 29, 1958. This law turned the National Advisory Committee on Aeronautics into the National Aeronautics and Space Administration (NASA). It also created a Civilian-Military Liaison Committee, chaired by the President, responsible for coordinating the nation's civilian and military space programs.


On October 21, 1959, Eisenhower approved the transfer of the Army's remaining space-related activities to NASA. On July 1, 1960, the Redstone Arsenal became NASA's George C. Marshall Space Flight Center, with von Braun as its first director. Development of the Saturn rocket family, which when mature, would finally give the US parity with the Soviets in terms of lifting capability, was thus transferred to NASA.


In 1958, Korolev upgraded the R-7 to be able to launch a 400-kilogram (880 lb) payload to the Moon. Three secret 1958 attempts to launch Luna E-1-class impactor probes failed. The fourth attempt, Luna 1, launched successfully on January 2, 1959, but missed the Moon. The fifth attempt on June 18 also failed at launch. The 390-kilogram (860 lb) Luna 2 successfully impacted the Moon on September 14, 1959. The 278.5-kilogram (614 lb) Luna 3 successfully flew by the Moon and sent back pictures of its far side on October 6, 1959.


The US reacted to the Luna program by embarking on the Ranger program in 1959, managed by NASA's Jet Propulsion Laboratory. The Block I Ranger 1 and Ranger 2 suffered Atlas-Agena launch failures in August and November 1961. The 727-pound (330 kg) Block II Ranger 3 launched successfully on January 26, 1962, but missed the Moon. The 730-pound (330 kg) Ranger 4 became the first US spacecraft to reach the Moon, but its solar panels and navigational system failed near the Moon and it impacted the far side without returning any scientific data. Ranger 5 ran out of power and missed the Moon by 725 kilometers (391 nmi) on October 21, 1962. The first successful Ranger mission was the 806-pound (366 kg) Block III Ranger 7 which impacted on July 31, 1964.


By 1959, American observers believed that the Soviet Union would be the first to get a human into space, because of the time needed to prepare for Mercury's first launch. On April 12, 1961, the USSR surprised the world again by launching Yuri Gagarin into a single orbit around the Earth in a craft they called Vostok 1. They dubbed Gagarin the first cosmonaut, roughly translated from Russian and Greek as "sailor of the universe". Although he had the ability to take over manual control of his spacecraft in an emergency by opening an envelope he had in the cabin that contained a code that could be typed into the computer, it was flown in an automatic mode as a precaution; medical science at that time did not know what would happen to a human in the weightlessness of space. Vostok 1 orbited the Earth for 108 minutes and made its reentry over the Soviet Union, with Gagarin ejecting from the spacecraft at 7,000 meters (23,000 ft), and landing by parachute. The Fédération Aéronautique Internationale (International Federation of Aeronautics) credited Gagarin with the world's first human space flight, although their qualifying rules for aeronautical records at the time required pilots to take off and land with their craft. For this reason, the Soviet Union omitted from their FAI submission the fact that Gagarin did not land with his capsule. When the FAI filing for Gherman Titov's second Vostok flight in August 1961 disclosed the ejection landing technique, the FAI committee decided to investigate, and concluded that the technological accomplishment of human spaceflight lay in the safe launch, orbiting, and return, rather than the manner of landing, and so revised their rules accordingly, keeping Gagarin's and Titov's records intact.


Gagarin became a national hero of the Soviet Union and the Eastern Bloc, and a worldwide celebrity. Moscow and other cities in the USSR held mass demonstrations, the scale of which was second only to the World War II Victory Parade of 1945. April 12 was declared Cosmonautics Day in the USSR, and is celebrated today in Russia as one of the official "Commemorative Dates of Russia." In 2011, it was declared the International Day of Human Space Flight by the United Nations.


The US Air Force had been developing a program to launch the first man in space, named Man in Space Soonest. This program studied several different types of one-man space vehicles, settling on a ballistic re-entry capsule launched on a derivative Atlas missile, and selecting a group of nine candidate pilots. After NASA's creation, the program was transferred over to the civilian agency and renamed Project Mercury on November 26, 1958. NASA selected a new group of astronaut (from the Greek for "star sailor") candidates from Navy, Air Force and Marine test pilots, and narrowed this down to a group of seven for the program. Capsule design and astronaut training began immediately, working toward preliminary suborbital flights on the Redstone missile, followed by orbital flights on the Atlas. Each flight series would first start unmanned, then carry a primate, then finally men.


Three weeks later, on May 5, 1961, Alan Shepard became the first American in space, launched in a ballistic trajectory on Mercury-Redstone 3, in a spacecraft he named Freedom 7. Though he did not achieve orbit like Gagarin, he was the first person to exercise manual control over his spacecraft's attitude and retro-rocket firing. After his successful return, Shepard was celebrated as a national hero, honored with parades in Washington, New York and Los Angeles, and received the NASA Distinguished Service Medal from President John F. Kennedy.


Gagarin's flight changed this; now Kennedy sensed the humiliation and fear on the part of the American public over the Soviet lead. He sent a memo dated April 20, 1961, to Vice President Lyndon B. Johnson, asking him to look into the state of America's space program, and into programs that could offer NASA the opportunity to catch up. The two major options at the time seemed to be, either establishment of an Earth orbital space station, or a manned landing on the Moon. Johnson in turn consulted with von Braun, who answered Kennedy's questions based on his estimates of US and Soviet rocket lifting capability. Based on this, Johnson responded to Kennedy, concluding that much more was needed to reach a position of leadership, and recommending that the manned Moon landing was far enough in the future that the US had a fighting chance to achieve it first.


Kennedy ultimately decided to pursue what became the Apollo program, and on May 25 took the opportunity to ask for Congressional support in a Cold War speech titled "Special Message on Urgent National Needs". Full text


He justified the program in terms of its importance to national security, and its focus of the nation's energies on other scientific and social fields. He rallied popular support for the program in his "We choose to go to the Moon" speech, on September 12, 1962, before a large crowd at Rice University Stadium, in Houston, Texas, near the construction site of the new Manned Spacecraft Center facility. Full text


American Virgil "Gus" Grissom repeated Shepard's suborbital flight in Liberty Bell 7 on July 21, 1961. Almost a year after the Soviet Union put a human into orbit, astronaut John Glenn became the first American to orbit the Earth, on February 20, 1962. His Mercury-Atlas 6 mission completed three orbits in the Friendship 7 spacecraft, and splashed down safely in the Atlantic Ocean, after a tense reentry, due to what falsely appeared from the telemetry data to be a loose heat-shield. As the first American in orbit, Glenn became a national hero, and received a ticker-tape parade in New York City, reminiscent of that given for Charles Lindbergh. On February 23, 1962, President Kennedy escorted him in a parade at Cape Canaveral Air Force Station, where he awarded Glenn with the NASA service medal.


The United States launched three more Mercury flights after Glenn's: Aurora 7 on May 24, 1962 duplicated Glenn's three orbits; Sigma 7 on October 3, 1962, six orbits; and Faith 7 on May 15, 1963, 22 orbits (32.4 hours), the maximum capability of the spacecraft. NASA at first intended to launch one more mission, extending the spacecraft's endurance to three days, but since this would not beat the Soviet record, it was decided instead to concentrate on developing Project Gemini.


Gherman Titov became the first Soviet cosmonaut to exercise manual control of his Vostok 2 craft on August 6, 1961. The Soviet Union demonstrated 24-hour launch pad turnaround and the capability to launch two piloted spacecraft, Vostok 3 and Vostok 4, in essentially identical orbits, on August 11 and 12, 1962. The two spacecraft came within approximately 6.5 kilometers (4.0 mi) of one another, close enough for radio communication. Vostok 4 also set a record of nearly four days in space. Though the two craft's orbits were as nearly identical as possible given the accuracy of the launch rocket's guidance system, slight variations still existed which drew the two craft at first as close to each other as 6.5 kilometers (3.5 nautical miles), then as far apart as 2,850 kilometers (1,540 nautical miles). There were no maneuvering rockets on the Vostok to permit space rendezvous, required to keep two spacecraft a controlled distance apart.


The Soviet Union duplicated its dual-launch feat with Vostok 5 and Vostok 6 (June 16, 1963). This time they launched the first woman (also the first civilian), Valentina Tereshkova, into space on Vostok 6. Launching a woman was reportedly Korolev's idea, and it was accomplished purely for propaganda value. Tereshkova was one of a small corps of female cosmonauts who were amateur parachutists, but Tereshkova was the only one to fly. The USSR didn't again open its cosmonaut corps to women until 1980, two years after the United States opened its astronaut corps to women.


The Soviets kept the details and true appearance of the Vostok capsule secret until the April 1965 Moscow Economic Exhibition, where it was first displayed without its aerodynamic nose cone concealing the spherical capsule. The "Vostok spaceship" had been first displayed at the July 1961 Tushino air show, mounted on its launch vehicle's third stage, with the nose cone in place. A tail section with eight fins was also added, in an apparent attempt to confuse western observers. This spurious tail section also appeared on official commemorative stamps and a documentary.


On September 20, 1963, in a speech before the United Nations General Assembly, President Kennedy proposed that the United States and the Soviet Union join forces in their efforts to reach the Moon. Soviet Premier Nikita Khrushchev initially rejected Kennedy's proposal.


On October 2, 1997, it was reported that Khrushchev's son Sergei claimed Khrushchev was poised to accept Kennedy's proposal at the time of Kennedy's assassination on November 22, 1963. During the next few weeks he reportedly concluded that both nations might realize cost benefits and technological gains from a joint venture, and decided to accept Kennedy's offer based on a measure of rapport during their years as leaders of the world's two superpowers, but changed his mind and dropped the idea since he did not have the same trust for Kennedy's successor, Lyndon Johnson.


As President, Johnson steadfastly pursued the Gemini and Apollo programs, promoting them as Kennedy's legacy to the American public. One week after Kennedy's death, he issued an executive order renaming the Cape Canaveral and Apollo launch facilities after Kennedy.


Focused by the commitment to a Moon landing, in January 1962 the US announced Project Gemini, a two-man spacecraft that would support the later three-man Apollo by developing the key spaceflight technologies of space rendezvous and docking of two craft, flight durations of sufficient length to simulate going to the Moon and back, and extra-vehicular activity to accomplish useful work outside the spacecraft.


The greater advances of the Soviet space program at the time allowed their space program to achieve other significant firsts, including the first EVA "spacewalk" and the first mission performed by a crew in shirt-sleeves. Gemini took a year longer than planned to accomplish its first flight, allowing the Soviets to achieve another first, launching Voskhod 1 on October 12, 1964, the first spacecraft with a three-cosmonaut crew. The USSR touted another technological achievement during this mission: it was the first space flight during which cosmonauts performed in a shirt-sleeve-environment. However, flying without spacesuits was not due to safety improvements in the Soviet spacecraft's environmental systems; rather this innovation was accomplished because the craft's limited cabin space did not allow for spacesuits. Flying without spacesuits exposed the cosmonauts to significant risk in the event of potentially fatal cabin depressurization. This feat would not be repeated until the US Apollo Command Module flew in 1968; this later mission was designed from the outset to safely transport three astronauts in a shirt-sleeve environment while in space.


Between October 14–16, 1964, Leonid Brezhnev and a small cadre of high-ranking Communist Party officials, deposed Khrushchev as Soviet government leader a day after Voskhod 1 landed, in what was called the "Wednesday conspiracy". The new political leaders, along with Korolev, ended the technologically troublesome Voskhod program, cancelling Voskhod 3 and 4, which were in the planning stages, and started concentrating on the race to the Moon. Voskhod 2 would end up being Korolev's final achievement before his death on January 14, 1966, as it would become the last of the many space firsts that demonstrated the USSR's domination in spacecraft technology during the early 1960s. According to historian Asif Siddiqi, Korolev's accomplishments marked "the absolute zenith of the Soviet space program, one never, ever attained since." There would be a two-year pause in Soviet piloted space flights while Voskhod's replacement, the Soyuz spacecraft, was designed and developed.


On March 18, 1965, about a week before the first American piloted Project Gemini space flight, the USSR accelerated the competition, by launching the two-cosmonaut Voskhod 2 mission with Pavel Belyayev and Alexey Leonov. Voskhod 2's design modifications included the addition of an inflatable airlock to allow for extravehicular activity (EVA), also known as a spacewalk, while keeping the cabin pressurized so that the capsule's electronics wouldn't overheat. Leonov performed the first-ever EVA as part of the mission. A fatality was narrowly avoided when Leonov's spacesuit expanded in the vacuum of space, preventing him from re-entering the airlock. In order to overcome this, he had to partially depressurize his spacesuit to a potentially dangerous level. He succeeded in safely re-entering the ship, but he and Belyayev faced further challenges when the spacecraft's atmospheric controls flooded the cabin with 45% pure oxygen, which had to be lowered to acceptable levels before re-entry. The reentry involved two more challenges: an improperly timed retrorocket firing caused the Voskhod 2 to land 386 kilometers (240 mi) off its designated target area, the town of Perm; and the instrument compartment's failure to detach from the descent apparatus caused the spacecraft to become unstable during reentry.


Most of the novice pilots on the early missions would command the later missions. In this way, Project Gemini built up spaceflight experience for the pool of astronauts who would be chosen to fly the Apollo lunar missions.


The circumlunar program (Zond), created by Vladimir Chelomey's design bureau OKB-52, was to fly two cosmonauts in a stripped-down Soyuz 7K-L1, launched by Chelomey's Proton UR-500 rocket. The Zond sacrificed habitable cabin volume for equipment, by omitting the Soyuz orbital module. Chelomey gained favor with Khruschev by employing members of his family.


Korolev's lunar landing program was designated N1/L3, for its N1 superbooster and a more advanced Soyuz 7K-L3 spacecraft, also known as the lunar orbital module ("Lunniy Orbitalny Korabl", LOK), with a crew of two. A separate lunar lander ("Lunniy Korabl", LK), would carry a single cosmonaut to the lunar surface.