2G (or 2-G) is short for second-generation cellular technology. Second-generation 2G cellular networks were commercially launched on the GSM standard in Finland by Radiolinja (now part of Elisa Oyj) in 1991.[1] Three primary benefits of 2G networks over their predecessors were that phone conversations were digitally encrypted; 2G systems were significantly more efficient on the spectrum enabling far greater wireless penetration levels; and 2G introduced data services for mobile, starting with SMS text messages. 2G technologies enabled the various networks to provide the services such as text messages, picture messages, and MMS (multimedia messages). All text messages sent over 2G are digitally encrypted, allowing the transfer of data in such a way that only the intended receiver can receive and read it.

After 2G was launched, the previous mobile wireless network systems were retroactively dubbed 1G. While radio signals on 1G networks are analog, radio signals on 2G networks are digital. Both systems use digital signaling to connect the radio towers (which listen to the devices) to the rest of the mobile system.

With General Packet Radio Service (GPRS), 2G offers a theoretical maximum transfer speed of 50 kbit/s (40 kbit/s in practice).[2] With EDGE (Enhanced Data Rates for GSM Evolution), there is a theoretical maximum transfer speed of 1 Mbit/s (500 kbit/s in practice).[2]

The most common 2G technology was the time division multiple access (TDMA)-based GSM, originally from Europe but used in most of the world outside North America. Over 60 GSM operators were also using CDMA2000 in the 450 MHz frequency band (CDMA450) by 2010.[3]


2.5G (GPRS)

2.5G ("second and a half generation") is used to describe 2G-systems that have implemented a packet-switched domain in addition to the circuit-switched domain. It doesn't necessarily provide faster service because bundling of timeslots is used for circuit-switched data services (HSCSD) as well.

2.75G (EDGE)

GPRS networks evolved to EDGE networks with the introduction of 8PSK encoding. While the symbol rate remained the same at 270.833 samples per second, each symbol carried three bits instead of one. Enhanced Data rates for GSM Evolution (EDGE), Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC) is a backward-compatible digital mobile phone technology that allows improved data transmission rates, as an extension on top of standard GSM. EDGE was deployed on GSM networks beginning in 2003, initially by AT&T in the United States.

Past 2G networks

2G has been superseded by newer technologies such as 2.5G, 2.75G, 3G, and 4G; however, 2G networks are still used in most parts of the world. Various carriers have made announcements that 2G technology in the United States is in the process of being shut down so that carriers can reclaim those radio bands and re-purpose them for newer technologies (e.g. 4G LTE).

Country Network Total decommission date Details
Taiwan FarEasTone 30 June 2017 [4]
Taiwan Chunghwa Telecom 30 June 2017 [4]
Taiwan Taiwan Mobile 30 June 2017 [4]
Japan NTT Docomo 2010 [5]
Japan au KDDI 2010
Japan Softbank 2010
Republic of Korea KT 2011
Republic of Korea LG Uplus 2011
Republic of Korea SK Telecom 2011
Thailand AIS 31 October 2019 Thailand’s National Broadcasting and Telecommunications Commission (NBTC) has approved October 31, 2019, as the date for shutdown of the county’s 2G mobile network. According to the NBTC, the shutdown will increase efficiency for network operators and open the door for 5G wireless broadband service by 2020. Operators are expected to migrate their 2G users to 3G and 4G services. Provincial governments will assist in informing 2G users of the move. The NBTC will cease in its use of 2G standards and inform handset retailers and importers of the network’s impending closure. [6]
Thailand TrueMove H 31 October 2019
Thailand DTAC 31 October 2019
United States AT&T 2017 AT&T's 2G GSM service was shut down in January 2017.[7][8][9] This shutdown had a notable impact on the electronic security industry, where many 2G GSM radios were in use for alarm signal communication to central station dispatch centers. 2G GSM radios were required to be replaced by newer generation radios to avoid service outages.[10]
United States Verizon 2019 Verizon plans to shut down its 2G and 3G CDMA-based network by 31 December 2019.[11] Making it the first LTE-only network in United States.
United States T-Mobile 2020 (TBC) T-Mobile US has postponed shutdown of their 2G network until 2020.[12]
Australia Telstra 2016 Telstra closed their GSM network on 1 December 2016, being the first mobile provider in Australia to switch off 2G.[13]
Australia Optus 2017 Optus shut down 2G in Western Australia and Northern Territory on 3 April 2017 and completed the shutdown within the rest of Australia on 1 August 2017.[14]
Australia Vodafone 2018 Vodafone closed its legacy GSM network on 30 June 2018.[15]
New Zealand Spark (CDMA) 2012 Spark's 2G network (CDMA) was shut down on 31 July 2012. Spark now operates 3G and 4G networks, and was the first mobile provider in New Zealand to switch off 2G.[16]
New Zealand 2degrees 2018 2degrees shutdown its 2G network on 15 March 2018.[17]
Netherlands T-Mobile 2020 (TBC) T-Mobile Netherlands will shutdown 2G services by 2020.[18]
Switzerland Swisscom 2021 Telecommunications in Switzerland is mainly operated by state-owned Swisscom, and the two privately held Salt and Sunrise Communications AG as these companies have a license to operate 2G. Swisscom will cease 2G services due to its "public service requirements" only by 1 January 2021.[19]
Switzerland Sunrise 2018 (TBC) Sunrise Communications AG has announced plans to phase out its GSM network by the end of 2018. GSM, GPRS and EDGE will be ended by the end of 2018 in favour of expanded 4G and 4G+ coverage.[20]
Singapore Singtel 2017
Singapore M1 2017
Singapore StarHub 2017
India Airtel 2019 (TBC) Bharti Airtel, the largest carrier will shut down the 2G network later after 2019.
India Reliance (including JIO) 2017 Reliance Communications, a group led by Reliance ADAG, decided to shut down its entire 2G network at the end of November 2017. It is the first operator in the country to do so.[21]Also Jio, a second largest carrier led by Reliance Industries (RIL) operates as the only 4G-LTE network in India.
Trinidad and Tobago bmobile 2016 bmobile decommissioned its 2G GSM network in order to roll out its LTE network on Band 2 (1900 MHz) on 9 December 2016. bmobile's 2G EDGE network will still be active.
México Movistar 2020 Movistar Mexico will start the shutdown of its 2G network in April 2019[22]
México AT&T Mexico 2020 AT&T Mexico has started the shutdown of its 2G network on the country.[22]

See also


  1. ^ "Radiolinja's History". 20 April 2004. Archived from the original on 23 October 2006. Retrieved 23 December 2009.
  2. ^ a b "Wi-Fi and mobile Internet (3G or 4G)". Proximus. Archived from the original on 12 October 2016. Retrieved 15 October 2017.
  3. ^ "CDMA Worldwide". Archived from the original on 30 January 2010. Retrieved 23 December 2009.
  4. ^ a b c "Taiwan's NCC urges 2G users to upgrade by June". www.telecomasia.net. Retrieved 15 April 2019.
  5. ^ "China nears full mobile broadband coverage on back of increased 4G adoption". South China Morning Post. 18 July 2016. Retrieved 15 April 2019.
  6. ^ "Thailand to Close 2G Network".
  7. ^ Gryta, Thomas (3 August 2012). "AT&T to Leave 2G Behind". Wall Street Journal. Retrieved 26 December 2016.
  8. ^ "AT&T 2G Sunset". povertymobile. 2016-01-20. Retrieved 2017-01-11.
  9. ^ "AT&T's Donovan Says 2G Network in 'Soft Lock', Decommissioning to Begin in Coming Months". FierceWireless.com. Retrieved 2017-01-11.
  10. ^ "2G Sunset Overview". Telguard. 21 July 2011. Retrieved 26 December 2016.
  11. ^ Danno, Mike. "Verizon to Shut Down 2G CDMA 1X Network by the End of 2019". FierceWireless. Retrieved 12 September 2016.
  12. ^ Abent, Eric (14 September 2016). "T-Mobile Takes a Swing at AT&T, Says Its 2G Network Will Stay Active through 2020". SlashGear. Retrieved 26 December 2016.
  13. ^ Turner, Adam (4 November 2016). "Budget Mobile Customers Brace for Australia's 2G Shutdown". Sydney Morning Herald. Retrieved 26 December 2016.
  14. ^ "2G Network Closure Update" (Press release). Optus. Retrieved 6 July 2017.
  15. ^ "We've switched off our 2G network". Vodafone Australia.
  16. ^ "Telecom closes CDMA network". The New Zealand Herald. Retrieved 1 August 2012.
  17. ^ "2degrees to close down 2G access in March 2018". 2degrees. Retrieved 26 September 2017.
  18. ^ "T-Mobile Netherlands plans GSM shutdown by 2020".
  19. ^ "Swisscom is equipping its mobile network for the future". Retrieved 2 November 2015.
  20. ^ "Sunrise to shut down GSM network by end-2018". Retrieved 20 June 2017.
  21. ^ "RComm to Shut Down 2G Network in a Month, Will Continue with 4G Only Network Like JIO".
  22. ^ a b Escalona, Claudia Juárez. "Movistar y AT&T ponen en marcha apagón 2G". El Economista. Retrieved 2019-03-26.
Preceded by
1st Generation (1G)
Mobile Telephony Generations Succeeded by
3rd Generation (3G)

1G refers to the first generation of wireless cellular technology (mobile telecommunications). These are the analog telecommunications standards that were introduced in the 1980s and continued until being replaced by 2G digital telecommunications. The main difference between the two mobile cellular systems (1G and 2G), is that the radio signals used by 1G networks are analog, while 2G networks are digital.

Although both systems use digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system, the voice itself during a call is encoded to digital signals in 2G whereas 1G is only modulated to higher frequency, typically 150 MHz and up. The inherent advantages of digital technology over that of analog meant that 2G networks eventually replaced them almost everywhere.

One such standard is Nordic Mobile Telephone (NMT), used in Nordic countries, Switzerland, the Netherlands, Eastern Europe and Russia. Others include Advanced Mobile Phone System (AMPS) used in North America and Australia, TACS (Total Access Communications System) in the United Kingdom, C-450 in West Germany, Portugal and South Africa, Radiocom 2000 in France, TMA in Spain, and RTMI in Italy. In Japan there were multiple systems. Three standards, TZ-801, TZ-802, and TZ-803 were developed by NTT (Nippon Telegraph and Telephone Corporation), while a competing system operated by Daini Denden Planning, Inc. (DDI) used the Japan Total Access Communications System (JTACS) standard.

The antecedent to 1G technology is the mobile radio telephone.

2G spectrum case

The 2G spectrum case was a $40 billion alleged scam by the politicians and government officials under the United Progressive Alliance (Congress) coalition government in India. The Union Government of that time was accused of undercharging mobile telephone companies for frequency allocation licenses, which they used to create 2G spectrum subscriptions for cell phones. The Government chose NM Rothschild and Sons to design a first-of-its-kind e-auction mechanism in the world, a US$2.27 billion landmark deal. The difference between the money collected and that mandated to be collected was estimated by the Comptroller and Auditor General of India at ₹1.76 trillion (US$24 billion), based on 2010 3G and BWA spectrum-auction prices. In a charge sheet filed on 2 April 2011 by the Central Bureau of Investigation (CBI), the loss was pegged at ₹3,098,455 million (US$43 billion). In a 19 August 2011 reply to the CBI, the Telecom Regulatory Authority of India (TRAI) said that the government had gained over ₹30 billion (US$420 million) by selling 2G spectrum.On 2 February 2012, the Supreme Court of India ruled on a Public Interest Litigation (PIL) related to the 2G spectrum allocation. The court declared the allotment of spectrum "unconstitutional and arbitrary", cancelling the 122 licenses issued in 2008 under A. Raja, the Minister of Communications & IT from 2007 to 2009, the primary official accused. According to the court, Raja "wanted to favour some companies at the cost of the public exchequer" and "virtually gifted away important national asset[s]." The zero-loss theory was discredited on 3 August 2012 when, after a Supreme Court directive, the Government of India revised the base price for 5-MHz 2G spectrum auctions to ₹140 billion (US$1.9 billion), raising its value to about ₹28 billion (US$390 million) per MHz (near the Comptroller and Auditor General estimate of ₹33.5 billion (US$470 million) per MHz).According to some analysts, many corruption scandals including the 2G spectrum case, the coal mining scam, Adarsh Housing Society scam and the Commonwealth Games scam were major factors behind the Indian National Congress-led UPA government's massive defeat in the 2014 Lok Sabha election. The severity of the corruption charges led to a loss of trust between Congress and the party. Time magazine listed the India's Telecoms Scandal as one of the Top 10 abuses of power.On 21 December 2017, the special court in New Delhi acquitted all accused in the 2G spectrum case including prime accused A Raja and Kanimozhi. This verdict was based on the fact that CBI could not find any evidence against the accused in those 7 years. As per the judgement, "Some people created a scam by artfully arranging a few selected facts and exaggerating things beyond recognition to astronomical levels." On 19 and 20 March 2018, the Enforcement Directorate and CBI respectively filed appeals against this verdict in the Delhi High Court.


3G, short for third generation, is the third generation of wireless mobile telecommunications technology. It is the upgrade for 2G and 2.5G GPRS networks, for faster internet speed. This is based on a set of standards used for mobile devices and mobile telecommunications use services and networks that comply with the International Mobile Telecommunications-2000 (IMT-2000) specifications by the International Telecommunication Union. 3G finds application in wireless voice telephony, mobile Internet access, fixed wireless Internet access, video calls and mobile TV.

3G telecommunication networks support services that provide an information transfer rate of at least 0.2 Mbit/s. Later 3G releases, often denoted 3.5G and 3.75G, also provide mobile broadband access of several Mbit/s to smartphones and mobile modems in laptop computers. This ensures it can be applied to wireless voice telephony, mobile Internet access, fixed wireless Internet access, video calls and mobile TV technologies.

A new generation of cellular standards has appeared approximately every tenth year since 1G systems were introduced in 1979 and the early to mid-1980s. Each generation is characterized by new frequency bands, higher data rates and non–backward-compatible transmission technology. The first 3G networks were introduced in 1998 and 4G networks in 2008.

1G :1979

2G :1988

3G :1998

4G :2008

5G :2018

Astra 2G

Astra 2G is one of the Astra communications satellites owned and operated by SES, launched to the Astra 28.2°E orbital slot in December 2014, at 03:37:49 Baikonur time.Astra 2G is positioned at 28.5°E (part of the Astra 28.2°E orbital slot) and is the last of three 'second generation' satellites launched to this slot to replace the first generation Astra 2A, Astra 2B, Astra 2C and Astra 2D craft originally positioned there between 1998 and 2001, and it joined Astra 2E and Astra 2F launched in 2013 and 2012, respectively.

Bulk modulus

The bulk modulus ( or ) of a substance is a measure of how resistant to compression that substance is. It is defined as the ratio of the infinitesimal pressure increase to the resulting relative decrease of the volume. Other moduli describe the material's response (strain) to other kinds of stress: the shear modulus describes the response to shear, and Young's modulus describes the response to linear stress. For a fluid, only the bulk modulus is meaningful. For a complex anisotropic solid such as wood or paper, these three moduli do not contain enough information to describe its behaviour, and one must use the full generalized Hooke's law.

Elastic modulus

An elastic modulus (also known as modulus of elasticity) is a quantity that measures an object or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is defined as the slope of its stress–strain curve in the elastic deformation region: A stiffer material will have a higher elastic modulus. An elastic modulus has the form:

where stress is the force causing the deformation divided by the area to which the force is applied and strain is the ratio of the change in some parameter caused by the deformation to the original value of the parameter. If stress is measured in pascals, then since strain is a dimensionless quantity, the units of λ will be pascals as well.

Specifying how stress and strain are to be measured, including directions, allows for many types of elastic moduli to be defined. The three primary ones are:

Three other elastic moduli are Poisson's ratio, Lamé's first parameter, and P-wave modulus.

Homogeneous and isotropic (similar in all directions) materials (solids) have their (linear) elastic properties fully described by two elastic moduli, and one may choose any pair. Given a pair of elastic moduli, all other elastic moduli can be calculated according to formulas in the table below at the end of page.

Inviscid fluids are special in that they cannot support shear stress, meaning that the shear modulus is always zero. This also implies that Young's modulus for this group is always zero.

In some English texts the here described quantity is called elastic constant, while the inverse quantity is referred to as elastic modulus.


GSM (Global System for Mobile communications) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation (2G) digital cellular networks used by mobile devices such as mobile phones and tablets. It was first deployed in Finland in December 1991. As of 2014, it has become the global standard for mobile communications – with over 90% market share, operating in over 193 countries and territories.2G networks developed as a replacement for first generation (1G) analog cellular networks, and the GSM standard originally described a digital, circuit-switched network optimized for full duplex voice telephony. This expanded over time to include data communications, first by circuit-switched transport, then by packet data transport via GPRS (General Packet Radio Services) and EDGE (Enhanced Data rates for GSM Evolution, or EGPRS).

Subsequently, the 3GPP developed third-generation (3G) UMTS standards, followed by fourth-generation (4G) LTE Advanced standards, which do not form part of the ETSI GSM standard.

"GSM" is a trademark owned by the GSM Association. It may also refer to the (initially) most common voice codec used, Full Rate.

General Packet Radio Service

General Packet Radio Service (GPRS) is a packet oriented mobile data standard on the 2G and 3G cellular communication network's global system for mobile communications (GSM). GPRS was established by European Telecommunications Standards Institute (ETSI) in response to the earlier CDPD and i-mode packet-switched cellular technologies. It is now maintained by the 3rd Generation Partnership Project (3GPP).GPRS is typically sold according to the total volume of data transferred during the billing cycle, in contrast with circuit switched data, which is usually billed per minute of connection time, or sometimes by one-third minute increments. Usage above the GPRS bundled data cap may be charged per MB of data, speed limited, or disallowed.

GPRS is a best-effort service, implying variable throughput and latency that depend on the number of other users sharing the service concurrently, as opposed to circuit switching, where a certain quality of service (QoS) is guaranteed during the connection. In 2G systems, GPRS provides data rates of 56–114 kbit/sec. 2G cellular technology combined with GPRS is sometimes described as 2.5G, that is, a technology between the second (2G) and third (3G) generations of mobile telephony. It provides moderate-speed data transfer, by using unused time division multiple access (TDMA) channels in, for example, the GSM system. GPRS is integrated into GSM Release 97 and newer releases.

Grumman S-2 Tracker

The Grumman S-2 Tracker (S2F prior to 1962) was the first purpose-built, single airframe anti-submarine warfare (ASW) aircraft to enter service with the United States Navy. Designed and initially built by Grumman, the Tracker was of conventional design — propeller-driven with twin radial engines, a high wing that could be folded for storage on aircraft carriers, and tricycle undercarriage. The type was exported to a number of navies around the world. Introduced in 1952, the Tracker and its E-1 Tracer derivative saw service in the U.S. Navy until the mid-1970s, and its C-1 Trader derivative until the mid-1980s, with a few aircraft remaining in service with other air arms into the 21st century. Argentina and Brazil are the last countries to still use the Tracker.

High Speed Packet Access

High Speed Packet Access (HSPA) is an amalgamation of two mobile protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), that extends and improves the performance of existing 3G mobile telecommunication networks using the WCDMA protocols. A further improved 3GPP standard, Evolved High Speed Packet Access (also known as HSPA+), was released late in 2008 with subsequent worldwide adoption beginning in 2010. The newer standard allows bit-rates to reach as high as 337 Mbit/s in the downlink and 34 Mbit/s in the uplink. However, these speeds are rarely achieved in practice.

IPhone (1st generation)

The iPhone (colloquially known as the iPhone 2G after 2008) is the first smartphone designed and marketed by Apple Inc. After years of rumors and speculation, it was officially announced on January 9, 2007, and was later released in the United States on June 29, 2007. It featured quad-band GSM cellular connectivity with GPRS and EDGE support for data transfer.

Development of the iPhone dated back to 2005, when former Apple CEO Steve Jobs conceived the idea of a device that users could directly interact with the display interface. The design was expanded upon over the next 2 years in complete secrecy, before being announced in Q1 2007.

Although several aspects of the iPhone are considered obsolete by current standards, the device is seen as an archetype of current cell phones, ditching physical hardware buttons and stylus in favor of a touch-based user interface. Its successor, the iPhone 3G, was announced in June of 2008.

IPod Touch

The iPod Touch (stylized and marketed as iPod touch) is a brand of iOS-based all-purpose mobile devices designed and marketed by Apple Inc. with a touchscreen-controlled user interface. It connects to the Internet only through Wi-Fi base stations, does not use cellular network data, and is therefore not a smartphone. Similarly to an iPhone, it can be used as a music player, digital camera, web browser, note-logger, and handheld gaming device. As of May 2013, 100 million iPod Touch units had been sold since 2007.iPod Touch models are sold by storage space and color, with all models of the same generation typically offering otherwise identical features, processors, and performance, in addition to available operating system upgrades; an exception was the fifth generation, as the low-end (16 GB) model was initially sold without a rear-facing camera. The current iPod touch is the sixth-generation model, released on July 15, 2015.

The iPod Touch is currently the only product in Apple's iPod product line, following the discontinuation of the iPod Nano and iPod Shuffle on July 27, 2017. Following the discontinuation, Apple revised the storage and pricing for the iPod Touch with 32 and 128 GB of storage.

Kaman SH-2G Super Seasprite

The Kaman SH-2G Super Seasprite is an American ship-based helicopter with anti-submarine, anti-surface threat capability, including over-the-horizon targeting. This aircraft extends and increases shipboard sensor and weapon capabilities against several types of enemy threats, including submarines of all types, surface ships, and patrol craft that may be armed with anti-ship missiles. It was originally developed for the United States Navy in 1980s as a reengined version of the older Kaman SH-2 Seasprite.

The SH-2G's primary missions include anti-submarine and anti-surface warfare, anti-ship missile defense, and anti-ship surveillance and targeting. Secondary missions may include medical evacuation, search and rescue, personnel and cargo transfer, as well as small boat interdiction, amphibious assault air support, gun fire spotting, mine detection and battle damage assessment.

List of free-to-air channels at 28°E

This is a list of all of the free-to-air channels that are currently available via satellite from SES Astra satellites (Astra 2E/2F/2G) located at 28.2 °E. These are the same group of satellites used for the Sky pay-TV platform and the Freesat free-to-air platform, therefore existing installations for these platforms would not require a realignment of the satellite dish or the purchase of any additional equipment.

Mobile broadband

Mobile broadband is the marketing term for wireless Internet access through a portable modem, USB wireless modem, or a tablet/smartphone or other mobile device. The first wireless Internet access became available in 1991 as part of the second generation (2G) of mobile phone technology. Higher speeds became available in 2001 and 2006 as part of the third (3G) and fourth (4G) generations. In 2011, 90% of the world's population lived in areas with 2G coverage, while 45% lived in areas with 2G and 3G coverage. Mobile broadband uses the spectrum of 225 MHz to 3700 MHz.

Shear modulus

In materials science, shear modulus or modulus of rigidity, denoted by G, or sometimes S or μ, is defined as the ratio of shear stress to the shear strain:


= shear stress
is the force which acts
is the area on which the force acts
= shear strain. In engineering , elsewhere
is the transverse displacement
is the initial length

The derived SI unit of shear modulus is the pascal (Pa), although it is usually expressed in gigapascals (GPa) or in thousands of pounds per square inch (ksi). Its dimensional form is M1L−1T−2, replacing force by mass times acceleration.


The Thorad-Agena was an American expendable launch system, derived from the Thor and Delta rockets. The first stage of the rocket was a stretched Thor variant named "Long Tank Thrust Augmented Thor". The Long Tank Thor first stage was later adopted by NASA's Delta program for its "Thrust Augmented Improved Delta", which first flew in 1968. The second stage was the Agena-D, which had already been used in conjunction with the standard configuration Thor, as the Thor-Agena. Three Castor rockets would be used as boosters. Most launches carried Corona (KeyHole) reconnaissance satellites, particularly spacecraft of the KH-4 series, however some scientific and technology development satellites were also flown, mostly towards the end of the program.

43 launches took place from 1966-72 with two complete failures and one partial.

The launch of a KH-4A photoreconnaissance satellite on May 9, 1967, malfunctioned when the Thor's first stage failed to cut off on schedule and continued burning until LOX depletion, thus putting the satellite into an incorrect orbit that seriously reduced its image quality.

The first total failure was the launch of a Nimbus weather satellite on May 5, 1968, when control of the Thor failed during launch and it was destroyed by Range Safety action at T+120 seconds. This mission was noteworthy because the satellite carried a pair of isotopic power generators known as SNAP (Systems For Nuclear Auxiliary Power). As the possibility of a launch failure had been considered during their design, the power generators were equipped with a very sturdy casing to prevent their radioactive contents from escaping into the environment. After the destruction of Nimbus-B's launch vehicle, Navy crews began an extensive search for the SNAP generators. On September 27, the Nimbus satellite was located in 300 feet of water near the Santa Barbara Islands with the SNAP units nearby. They were successfully fished out of the ocean two weeks later and their protective casings found to be intact. The fuel inside them was taken out and reused in a subsequent Nimbus launch.

As part of the investigation, parts of the Thor were recovered and examined. It was discovered that the yaw gyro was installed improperly and had missing alignment pins, apparently because a pad technician had mistakenly broken them off during installation. Without the pins, the gyro rotated out of position with the effect that the booster lost control almost as soon as the pitch and roll sequence started.

The other total failure was the attempted launch of a KH-4B photo-reconnaissance satellite on February 17, 1971. A technician mistakenly added too much lubricant to the Thor's fuel system, the result being that the excess fluid formed a frozen plug in a section of plumbing. The booster lifted and flew normally until the start of the pitch and roll program about 20 seconds after liftoff at which point the turbopump gearbox disintegrated due to loss of lubricant. Flying debris tore up the Thor's thrust section, causing total loss of thrust. With the main engine being the only source of attitude control, the launch vehicle tumbled uncontrollably and exploded 30 seconds after launch, the debris impacting in Bear Creek Canyon a quarter mile from the launch complex.

The Thorad-Agena was flown in two different configurations, the SLV-2G, and the SLV-2H. These differed in that the SLV-2G used Castor 1 strap-on boosters, whereas the 2H used Castor 2s.

Young's modulus

Young's modulus or Young modulus is a mechanical property that measures the stiffness of a solid material. It defines the relationship between stress (force per unit area) and strain (proportional deformation) in a material in the linear elasticity regime of a uniaxial deformation.

Young's modulus is named after the 19th-century British scientist Thomas Young. However, the concept was developed in 1727 by Leonhard Euler, and the first experiments that used the concept of Young's modulus in its current form were performed by the Italian scientist Giordano Riccati in 1782, pre-dating Young's work by 25 years. The term modulus is the diminutive of the Latin term modus which means measure.

0G radio telephones (1946)
1G (1979)
2G (1991)
2G transitional
(2.5G, 2.75G)
3G (2001)
3G transitional
(3.5G, 3.75G, 3.9G)
4G (2009)
IMT Advanced (2013)
5G (2019)
IMT-2020 (under development)
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