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Spacecraft propulsion

Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. Space propulsion or in-space propulsion deals with propulsion systems used in the vacuum of space and should not be confused with launch vehicles. Several methods, both pragmatic and hypothetical, have been developed each having its own drawbacks and advantages. Most satellites have simple reliable chemical thrusters or resistojet rockets for orbital station-keeping and some use momentum wheels for attitude control. Soviet bloc satellites have used electric propulsion for decades, newer Western geo-orbiting spacecraft are starting to use them for north-south station-keeping and orbit raising. Interplanetary vehicles use chemical rockets as well, although a few have used ion thrusters and Hall-effect thrusters to great success. Artificial satellites are first launched into the desired altitude by conventional liquid/solid propelled rockets after which the satellite may use onboard propulsion systems for orbital stationkeeping.

Once in the desired orbit, they need some form of attitude control so that they are pointed with respect to the Earth, the Sun, some astronomical object of interest. They are subject to drag from the thin atmosphere, so that to stay in orbit for a long period of time some form of propulsion is necessary to make small corrections. Many satellites need to be moved from one orbit to another from time to time, this requires propulsion. A satellite's useful life is over once it has exhausted its ability to adjust its orbit. For interplanetary travel, a spacecraft can use its engines to leave Earth's orbit, it is not explicitly necessary as the initial boost given by the rocket, gravity slingshot, monopropellant/bipropellent attitude control propulsion system are enough for the exploration of the solar system. Once it has done so, it must somehow make its way to its destination. Current interplanetary spacecraft do this with a series of short-term trajectory adjustments. In between these adjustments, the spacecraft moves along its trajectory with a constant velocity.

The most fuel-efficient means to move from one circular orbit to another is with a Hohmann transfer orbit: the spacecraft begins in a circular orbit around the Sun. A short period of thrust in the direction of motion accelerates or decelerates the spacecraft into an elliptical orbit around the Sun, tangential to its previous orbit and to the orbit of its destination; the spacecraft falls along this elliptical orbit until it reaches its destination, where another short period of thrust accelerates or decelerates it to match the orbit of its destination. Special methods such as aerobraking or aerocapture are sometimes used for this final orbital adjustment; some spacecraft propulsion methods such as solar sails provide low but inexhaustible thrust. The concept has been tested by the Japanese IKAROS solar sail spacecraft. No spacecraft capable of short duration interstellar travel has yet been built, but many hypothetical designs have been discussed; because interstellar distances are great, a tremendous velocity is needed to get a spacecraft to its destination in a reasonable amount of time.

Acquiring such a velocity on launch and getting rid of it on arrival remains a formidable challenge for spacecraft designers. When in space, the purpose of a propulsion system is to change the v, of a spacecraft; because this is more difficult for more massive spacecraft, designers discuss spacecraft performance in amount of change in momentum per unit of propellant consumed called specific impulse. The higher the specific impulse, the better the efficiency. Ion propulsion engines have high specific impulse and low thrust whereas chemical rockets like monopropellant or bipropellant rocket engines have a low specific impulse but high thrust; when launching a spacecraft from Earth, a propulsion method must overcome a higher gravitational pull to provide a positive net acceleration. In orbit, any additional impulse very tiny, will result in a change in the orbit path. 1) Prograde/Retrogade - Increases/Decreases altitude of orbit 2) Perpendicular to orbital plane - Changes Orbital inclination The rate of change of velocity is called acceleration, the rate of change of momentum is called force.

To reach a given velocity, one can apply a small acceleration over a long period of time, or one can apply a large acceleration over a short time. One can achieve a given impulse with a large force over a short time or a small force over a long time; this means that for manoeuvring in space, a propulsion method that produces tiny accelerations but runs for a long time can produce the same impulse as a propulsion method that produces large accelerations for a short time. When launching from a planet, tiny accelerations cannot overcome the planet's gravitational pull and so cannot be used. Earth's surface is situated deep in a gravity well; the escape velocity required to get out of it is 11.2 kilometers/second. As human beings evolved in a gravitational field of 1g, an ideal propulsion system would be one that provides a continuous acceleration of 1g (though human bodies can tolerate much larger accele

Longmeadow, Massachusetts

Longmeadow is a town in Hampden County, Massachusetts, in the United States. The population was 15,784 at the 2010 census. Longmeadow was first settled in 1644, incorporated October 17, 1783; the town was farmland within the limits of Springfield. It remained pastoral until the street railway was built c. 1910, when the population tripled over a fifteen-year period. After Interstate 91 was built in the wetlands on the west side of town, population tripled again between 1960 and 1975. During the 19th and early 20th centuries, Longmeadow was best known as the site from which Longmeadow brownstone was mined. Several famous American buildings, including Princeton University's Neo-Gothic library, are made of Longmeadow brownstone. In 1894, the more populous and industrialized "East Village" portion of the town containing the brownstone quarries split off to become East Longmeadow. Designed by famed golf course architect Donald Ross in 1922, the Longmeadow Country Club was the proving ground for golf equipment designed and manufactured by the Spalding Co. of Chicopee.

Bobby Jones, a consultant for Spalding, was a member in standing at LCC and made a number of his instructional films at LCC in the 1930s. Longmeadow is located in the western part of the state, just south of the city of Springfield, is bordered on the west by the Connecticut River and Agawam, to the east by East Longmeadow, to the south by Enfield, Connecticut, it extends 3 miles north to south and 4 miles east to west. It is 20 miles north of Hartford. More than 30% of the town is permanent open space. Conservation areas on the west side of town include more than 750 acres bordering the Connecticut River; the area supports a wide range of wildlife including deer, wild turkeys and eagles. Springfield's Forest Park, which at 735 acres is the largest city park in New England, forms the northern border of the town; the private Twin Hills and public Franconia golf courses, plus town athletic fields and conservation land, cover nearly 2/3 of the eastern border of the town. Two large public parks, the Longmeadow Country Club, three conservation areas account for the bulk of the remaining formal open space.

20% of the houses in town are in proximity to a "dingle", a tree-lined steep-sided sandy ravine with a wetland at the bottom that provides a privacy barrier between yards. Longmeadow has a town common referred to as "The Green", located along U. S. Route 5 on the west side of town, it is about 0.5 miles long. 100 houses date back before 1900, most of which are in the historic district, are located near the town green. Longmeadow’s Town Green is a historic district on the National Register of Historic Places, it is surrounded by a number of buildings dating back to the 18th and 19th centuries. Longmeadow is unique as the town green has maintained its residential purpose and has resisted commercial pressure; the current function as listed by the National Register of Historic Places is domestic and landscape. The current sub-function as listed by the National Register of Historic Places is park and single dwelling. Houses along the photogenic main street are set back farther than in most towns of similar residential density.

The town has three remodeled elementary schools, two secondary schools, one high school. The commercial center of town is an area called "The Longmeadow Shops", including restaurants and clothing stores. According to the United States Census Bureau, the town has a total area of 9.7 square miles, of which 9.1 square miles are land and 0.50 square miles, or 5.34%, are water. As of the census of 2000, there were 15,633 people, 5,734 households, 4,432 families residing in the town; the population density was 1,732.5 inhabitants per square mile. There were 5,879 housing units at an average density of 651.5 per square mile. The racial makeup of the town was 95.42% White, 0.69% African American, 0.05% Native American, 2.90% Asian, 0.06% Pacific Islander, 0.26% from other races, 0.62% from two or more races. Hispanic or Latino of any race were 1.09% of the population. There were 5,734 households out of which 37.1% had children under the age of 18 living with them, 69.1% were married couples living together, 6.4% had a female householder with no husband present, 22.7% were non-families.

20.4% of all households were made up of individuals and 14.0% had someone living alone, 65 years of age or older. The average household size was 2.66 and the average family size was 3.09. In the town, the population was spread out with 26.8% under the age of 18, 4.6% from 18 to 24, 22.0% from 25 to 44, 28.7% from 45 to 64, 17.8% who were 65 years of age or older. The median age was 43 years. For every 100 females, there were 87.7 males. For every 100 females age 18 and over, there were 82.0 males. The median income for a household in the town was $109,586, the median income for a family was $115,578. Males had a median income of $68,238 versus $40,890 for females; the per capita income for the town was $48,949. About 1.0% of families and 2.1% of the population were below the poverty line, including 0.3% of those under age 18 and 8.3% of those age 65 or over. The town is chartered as an Open Town Meeting form of government; the town government consists of a Select Board with five members, elected by the town.

The public school system is governed by the School Committee. The School Committee is made up of seven voting members elected by the town, the superintendent of schools, two assistant-superintendents, a secretary, a student representative; the Longmeadow public school system operates six schools. Blueberry Hill School, Center School, Wol

The Siegel–Schwall Band (1971 album)

The Siegel–Schwall Band is an album by the blues-rock group the Siegel–Schwall Band. Released in 1971, it was their fifth album, their first to be released by Wooden Nickel Records, it is not to be confused with the band's 1966 debut album, titled The Siegel-Schwall Band. The Siegel–Schwall Band won the 1973 Grammy Award for Best Album Cover; the cover was illustrated with art direction by Acy R. Lehman. Side one:" Country Road" – 3:19 "Devil" – 5:10 "Leavin'" – 3:10 "Corrina" – 6:05 Side two:"I Won't Hold My Breath" – 4:01 "Next to You" – 4:20 "Hush Hush" – 11:06 Corky Siegelpiano, vocals Jim Schwallguitar, vocals Rollo Radfordbass, vocals Shelly Plotkindrums Produced by Bill Traut and Peter Szillies Engineers: John Janus, Roger Anfinsen, Joe Lopes, Gary Taylor, Randy Kling Mixing: Martin Feldman Photography: Colin Johnson Artwork: Harvey Dinnerstein Art direction: Acy Lehman

Term limit

A term limit is a legal restriction that limits the number of terms an officeholder may serve in a particular elected office. When term limits are found in presidential and semi-presidential systems they act as a method of curbing the potential for monopoly, where a leader becomes "president for life"; this is intended to protect a democracy from becoming a de facto dictatorship. Sometimes, there is an lifetime limit on the number of terms an officeholder may serve. Term limits have a long history. Ancient Athens and Ancient Rome, two early classic republics, had term limits imposed on their elected offices as did the city-state of Venice. In ancient Athenian democracy, only offices selected by sortition were subject to term limits. Elected offices were all subject to possible re-election, although they were minoritarian, these positions were more prestigious and those requiring the most experience, such as military generals and the superintendent of springs. In the Roman Republic, a law was passed imposing a limit of a single term on the office of censor.

The annual magistrates—tribune of the plebs, quaestor and consul—were forbidden reelection until a number of years had passed.. There was a term limit of 6 months for a dictator. Many modern presidential republics employ term limits for their highest offices; the United States placed a limit of two terms on its presidency by means of the 22nd Amendment to the Constitution in 1951. There are no term limits for Vice Presidency and Senators, although there have been calls for term limits for those offices. Under various state laws, some state governors and state legislators have term limits. Formal limits in America date back to the 1682 Pennsylvania Charter of Liberties, the colonial frame of government of the same year, authored by William Penn and providing for triennial rotation of the Provincial Council, the upper house of the colonial legislature.. The Russian Federation has a rule for the head of state that allows the President of Russia to serve more than two terms if not consecutive. For governors of federal subjects, the same two-term limit existed until 2004, but now there are no term limits for governors.

Term limits are common in Latin America, where most countries are presidential republics. Early in the last century, the Mexican revolutionary Francisco Madero popularized the slogan Sufragio Efectivo, no Reelección. In keeping with that principle, members of the Congress of Mexico cannot be reelected for the next immediate term under article 50 and 59 of the Constitution of Mexico, adopted in 1917; the President of Mexico is limited to a single six-year term, called the Sexenio. This makes every presidential election in Mexico a non-incumbent election. Countries that operate a parliamentary system of government are less to employ term limits on their leaders; this is because such leaders have a set "term" at all: rather, they serve as long as they have the confidence of the parliament, a period which could last for life. Many parliaments can be dissolved for snap elections which means some parliaments can last for mere months while others can continue until their expiration dates; such countries may impose term limits on the holders of other offices—in republics, for example, a ceremonial presidency may have a term limit if the office holds reserve powers.

Term limits may be divided into two broad categories: lifetime. With consecutive term limits, an officeholder is limited to serving a particular number of terms in that particular office. Upon hitting the limit in one office, an officeholder may not run for the same office again. After a set period of time, the clock resets on the limit, the officeholder may run for election to his/her original office and serve up to the limit again. With lifetime limits, once an officeholder has served up to the limit, he/she may never again run for election to that office. Lifetime limits are much more restrictive than consecutive limits. Research shows that legislative term limits increase legislative polarization, reduce the legislative skills of politicians, reduce the legislative productivity of politicians, weaken legislatures vis-a-vis the executive, reduce voter turnout. Parties respond to the implementation of term limits by recruiting candidates for office on more partisan lines. Term limits have not reduced campaign spending, reduced the gender gap in political representation, increased the diversity of law-makers, increased the constituent service activities of law-makers.

Term limits in the United States Term of office List of political term limits Reelection Real Term Limits: Now More Than Ever, an article by Doug Bandow in favor of term limits Legislative Term Limits: An Overview at the Library of Congress Web Archives, term limits information from the National Conference of State Legislatures

USS Sanctuary (AH-17)

USS Sanctuary was a Haven-class hospital ship that served in the U. S. Navy in World War II and the Vietnam War. Sanctuary was laid down as SS Marine Owl by the Sun Dry Dock Co.. Chester, Pa.. Subsequently converted to a hospital ship by the Todd Shipbuilding Co. at Hoboken, N. J. whose citizens matched the cost of conversion with the purchase of war bonds, she was commissioned on 20 June 1945, Commander John M. Paulsson, USNR, in command of the ship. Following the shakedown, Sanctuary departed Norfolk on 31 July for the Pacific, she arrived at Pearl Harbor four days after the Japanese acceptance of surrender terms and, on 22 August, continued on to the Far East to assist in the repatriation of former POWs. Proceeding via Okinawa, Sanctuary arrived off Wakayama in Task Group 56.5 on 11 September. On the afternoon of the 13th, she commenced taking on sick and ambulatory cases. By 03:00 on the 14th, she had exceeded her rated bed capacity of 786. A call was put out to the fleet requesting cots; the request was answered.

Despite a typhoon encountered en route, Sanctuary delivered her charges safely to Army personnel at Naha. Arriving on the 22d, she embarked more ex-POWs. On the 25th, she discharged her liberated prisoners. A typhoon warning next sent her to sea. There, she exchanged passengers for patients. Between 18 November and 17 December, Sanctuary completed a run to Saipan and Guam, back to San Francisco. During late December 1945 and January 1946, she made two round trips between Hawaii. On 7 February, she departed San Francisco for deactivation, she was decommissioned on 15 August. For the next 15 years, she was berthed with the Atlantic Reserve Fleet: on 1 September 1961 her name was stricken from the Navy list, she was transferred to the Maritime Administration for berthing with the National Defense Reserve Fleet. On 1 March 1966, Sanctuary was reinstated on the Navy list. Towed to Louisiana, she was modernized at the Avondale Westwego. Modernization had given her a heliport, three x-ray units, a blood bank, an artificial kidney machine, ultrasonic diagnostic equipment, a recompression chamber and other modern equipment, culinary, etc. to supplement her 20 wards and four operating rooms.

Three hundred and sixteen medical personnel were assigned to staff the Naval Hospital. Her mission had shifted in emphasis: from that of an "ambulance" ship carrying wounded and sick to hospitals in rear areas, to that of a equipped hospital carrying medical facilities close to the combat area. On 8 March 1967, Sanctuary departed San Francisco for the Far East. On 2 April, she joined the 7th Fleet at Subic Bay. On the 10th, she arrived at South Vietnam. "SANCTUARY received WIA casualties directly from the field and wounded who had received prior treatment at shore medical facilities, sick and wounded that required special treatment not available ashore." That afternoon she took on her first casualties – ten marines badly burned when their amphibious tank detonated a land mine, which, in turn, had exploded the gasoline tank. By midnight, 136 patients had been received. By the end of April, she had admitted 717 patients – 319 combat casualties, 72 non-combat injuries, 326 suffering from various diseases – and treated 682 outpatients.

Only two of her patients died. Assigned to duty off South Vietnam on a non-rotating basis, Sanctuary began her extended overseas tour spending a minimum of 50 days operating on the line each quarter, followed by an availability and upkeep period at Subic Bay. By April 1968, after a year on that schedule, she had admitted 5,354 patients and treated another 9,187 on an outpatient basis. Helicopters, bringing patients from the battlefield, transferring them from and to other medical facilities, or carrying passengers to and from the ship, had made more than 2,500 landings on her deck; the following month, Sanctuary's schedule was changed to 90-day on-the-line periods. Her operating area and her itinerary on the line, remained the same, she continued to operate off the northern provinces of South Vietnam. Granted brief rest and recreation out of the area, Sanctuary — the only Navy hospital off Vietnam after 16 March 1970 – maintained her busy schedule to that date and increased it thereafter through 1970 and into 1971 during which time she was scheduled for 120-day on-the-line schedules.

On 23 April 1971, she departed Da Nang for the last time. During May, she called at Sasebo.

Tue Bjørn Thomsen

Tue Bjørn Thomsen was a professional boxer from Denmark, whose best performance as an amateur was winning the bronze medal at the 1997 World Amateur Boxing Championships in Budapest, Hungary. Born in Egedesminde, Greenland to family of Danish and Icelandic heritage, he made his professional debut in late 1997. On March 31, 2000 he won the vacant IBC Super Cruiserweight Title by defeating Nate Miller of the United States, in the Esbjerg Stadionhal in Esbjerg, Denmark. On April 23, 2006, Thomsen was knifed to death during a bar fight in central Copenhagen. Professional boxing record for Tue Bjørn Thomsen from BoxRec