The Boeing 601 (sometimes referred to as the BSS-601 , and previously as the HS-601 ) is a retired communications satellite bus designed in 1985 and introduced in 1987 by Hughes Space and Communications Company . The series was extremely popular in the 1990s, with more than 84 purchased by customers globally. The more advanced 601HP derivative (for "high power") was introduced in 1995. Hughes, and the 601 platforms, were acquired by Boeing in 2000.
24-518: The last commercial 601 satellite was ordered in 2001 and launched in 2004. The NASA Space Communications and Navigation (SCaN) Program Office in December 2007 selected the BSS-601HP for its third generation TDRS spacecraft, adding the two 15-foot (4.5m) diameter steerable antennas. The TDRS-M satellite, launched on August 18, 2017, became the last 601 satellite to reach orbit. The Boeing-601 model
48-558: A light bulb with a power rating of 100 W is turned on for one hour, the energy used is 100 watt hours (W·h), 0.1 kilowatt hour, or 360 kJ . This same amount of energy would light a 40-watt bulb for 2.5 hours, or a 50-watt bulb for 2 hours. Power stations are rated using units of power, typically megawatts or gigawatts (for example, the Three Gorges Dam in China is rated at approximately 22 gigawatts). This reflects
72-541: A turbine, which generates 648 MW e (i.e. electricity). Other SI prefixes are sometimes used, for example gigawatt electrical (GW e ). The International Bureau of Weights and Measures , which maintains the SI-standard, states that further information about a quantity should not be attached to the unit symbol but instead to the quantity symbol (e.g., P th = 270 W rather than P = 270 W th ) and so these unit symbols are non-SI. In compliance with SI,
96-495: A unit of time, namely 1 J/s. In this new definition, 1 absolute watt = 1.00019 international watts. Texts written before 1948 are likely to be using the international watt, which implies caution when comparing numerical values from this period with the post-1948 watt. In 1960, the 11th General Conference on Weights and Measures adopted the absolute watt into the International System of Units (SI) as
120-424: Is done is one watt. 1 W = 1 J / s = 1 N ⋅ m / s = 1 k g ⋅ m 2 ⋅ s − 3 . {\displaystyle \mathrm {1~W=1~J{/}s=1~N{\cdot }m{/}s=1~kg{\cdot }m^{2}{\cdot }s^{-3}} .} In terms of electromagnetism , one watt
144-733: Is named after the Scottish inventor James Watt . The unit name was proposed by C. William Siemens in August 1882 in his President's Address to the Fifty-Second Congress of the British Association for the Advancement of Science . Noting that units in the practical system of units were named after leading physicists, Siemens proposed that watt might be an appropriate name for a unit of power. Siemens defined
168-535: Is named in honor of James Watt (1736–1819), an 18th-century Scottish inventor , mechanical engineer , and chemist who improved the Newcomen engine with his own steam engine in 1776. Watt's invention was fundamental for the Industrial Revolution . When an object's velocity is held constant at one meter per second against a constant opposing force of one newton , the rate at which work
192-523: Is the rate at which electrical work is performed when a current of one ampere (A) flows across an electrical potential difference of one volt (V), meaning the watt is equivalent to the volt-ampere (the latter unit, however, is used for a different quantity from the real power of an electrical circuit). 1 W = 1 V ⋅ A . {\displaystyle \mathrm {1~W=1~V{\cdot }A} .} Two additional unit conversions for watt can be found using
216-807: The Telecom 87 conference in Geneva, Switzerland. The 601 bus is divided into two modules. The first module houses the propulsion system, batteries, and electronics for the bus, and bears launch vehicle loads. The second module contains shelves carrying the communications equipment, payload electronics, and heat pipes . Solar arrays , reflectors , and antenna feeds are mounted to the payload module. The standard 601 platform supports up to 48 transponders and provides up to 4,800 watts of power. The 601HP supports up to 60 transponders and provides up to 10,000 watts. A significant number of Boeing 601s have experienced failures in orbit, some resulting in complete failure of
240-470: The above equation and Ohm's law . 1 W = 1 V 2 / Ω = 1 A 2 ⋅ Ω , {\displaystyle \mathrm {1~W=1~V^{2}/\Omega =1~A^{2}{\cdot }\Omega } ,} where ohm ( Ω {\displaystyle \Omega } ) is the SI derived unit of electrical resistance . The watt
264-515: The energy company Ørsted A/S uses the unit megawatt for produced electrical power and the equivalent unit megajoule per second for delivered heating power in a combined heat and power station such as Avedøre Power Station . When describing alternating current (AC) electricity, another distinction is made between the watt and the volt-ampere . While these units are equivalent for simple resistive circuits , they differ when loads exhibit electrical reactance . Radio stations usually report
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#1732787825955288-460: The maximum power output it can achieve at any point in time. A power station's annual energy output, however, would be recorded using units of energy (not power), typically gigawatt hours. Major energy production or consumption is often expressed as terawatt hours for a given period; often a calendar year or financial year. One terawatt hour of energy is equal to a sustained power delivery of one terawatt for one hour, or approximately 114 megawatts for
312-647: The optional electronic propulsion system, called Xenon Ion Propulsion System or XIPS , for station keeping. At least four satellites with XIPS propulsion have experienced partial or total failure of the XIPS system which significantly reduced the lifespan of the satellite. HS-376 The Boeing 376 (sometimes referred to as the BSS-376 , and previously as the HS-376 ) is a communications satellite bus introduced in 1978 by Hughes Space and Communications Company . It
336-488: The power of their transmitters in units of watts, referring to the effective radiated power . This refers to the power that a half-wave dipole antenna would need to radiate to match the intensity of the transmitter's main lobe . The terms power and energy are closely related but distinct physical quantities. Power is the rate at which energy is generated or consumed and hence is measured in units (e.g. watts) that represent energy per unit time . For example, when
360-595: The power subsystem and the command and telemetry subsystems. The despun section contained the communications payload, including the antennas and transponders. The stock version had a launch mass of 1,100 to 1,450 kg (2,430 to 3,200 lb), a mass of 540 to 790 kg (1,190 to 1,740 lb) after reaching geostationary orbit and an 8 to 10-year design life. When stowed for launch, its dimensions were 2.8 to 3.15 m (9 ft 2 in to 10 ft 4 in) in height and 2.16 m (7 ft 1 in) in diameter. With its solar panels fully extended its height
384-421: The satellite. An unconfirmed number of 601s launched prior to August 1997 have a design flaw in their SCPs, where a tin-plated relay forms crystalline "whiskers " under certain specific conditions. These whiskers eventually caused an electrical short. Each satellite contains two SCPs and the backup unit will take control in the event of a failure of the primary unit. In some cases, both SCPs have failed, rendering
408-589: The spacecraft unusable. A notable example was the Galaxy IV satellite. At least eight 601s have experienced SCP failures; four of which were double failures resulting in total loss of the satellite. Hughes switched to nickel plating on later 601s to resolve this problem, at the expense of payload weight. Some 601HPs have experienced problems with their batteries, resulting in a reduction of eclipse protection. This would require some transponders to be shut down during eclipse periods. Some Boeing-601 satellites featured
432-569: The unit of power. In the electric power industry , megawatt electrical ( MWe or MW e ) refers by convention to the electric power produced by a generator, while megawatt thermal or thermal megawatt (MWt, MW t , or MWth, MW th ) refers to thermal power produced by the plant. For example, the Embalse nuclear power plant in Argentina uses a fission reactor to generate 2,109 MW t (i.e. heat), which creates steam to drive
456-570: The unit within the existing system of practical units as "the power conveyed by a current of an Ampère through the difference of potential of a Volt". In October 1908, at the International Conference on Electric Units and Standards in London, so-called international definitions were established for practical electrical units. Siemens' definition was adopted as the international watt. (Also used: 1 A × 1 Ω.) The watt
480-413: Was 6.6 to 8 m (22 to 26 ft). Its power system generated approximately 1,100 to 1,200 watts of power at beginning of life , thanks to two cylindrical solar panels. The bottom panel was retracted around the body and top panel for launch, and extended downwards for operation. It also had two NiCd batteries for solar eclipses. There were four variations of this platform: The HS-376
504-477: Was Hughes’ first major design and development for a communications satellite with three-axis, or body stabilization. All previous Hughes satellite models ( HS-376 ) had been cylindrical spacecraft that were spin-stabilized at 50 revolutions per minute. Design of the Boeing-601 began in 1985, with full-scale development following two years later. The new satellite's first official public presentation took place at
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#1732787825955528-413: Was a spin-stabilized bus, a successor to Hughes HS-333 . The satellite bus was designed and manufactured by Hughes . This spin-stabilized platform had two main sections. The spinning section was kept rotating at 50 rpm to maintain attitude, and a despun section was used by the payload to maintain radio coverage. The spinning section included the apogee kick motor , most of the attitude control,
552-469: Was a very successful satellite platform with 58 satellites ordered, built and launched. It was also the first satellite to launch from the Space Shuttle . Watt The watt (symbol: W ) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m ⋅s . It is used to quantify the rate of energy transfer . The watt
576-420: Was defined as equal to 10 units of power in the practical system of units. The "international units" were dominant from 1909 until 1948. After the 9th General Conference on Weights and Measures in 1948, the international watt was redefined from practical units to absolute units (i.e., using only length, mass, and time). Concretely, this meant that 1 watt was defined as the quantity of energy transferred in
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