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to give everything they had to this cause. However, when they failed to live the Law of
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Consecration, which was a promise to voluntarily give all their property to the community for equal
|
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distribution, Joseph Smith received a revelation that God would build Zion later, when the people
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9827_377
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were ready. Both the Community of Christ and the LDS Church have come to understand Zion as
|
9827_378
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primarily a community way of life that is centered around Jesus Christ, but many people still
|
9827_379
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believe that, when they are ready, they will be able to build the literal city of Zion as well.
|
9827_380
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See also
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9827_381
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Cunning Folk Traditions and the Latter Day Saint Movement
|
9827_382
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History of The Church of Jesus Christ of Latter-day Saints
Mormonism in the 19th century
|
9827_383
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Death in 19th-century Mormonism
Mormonism in the 20th century
Mormonism in the 21st century
|
9827_384
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Origin of Latter Day Saint polygamy
Latter Day Saint Historians
|
9827_385
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Criticism of The Church of Jesus Christ of Latter-day Saints
Mormonism and history
|
9827_386
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Restorationism (Christian primitivism)
List of articles about Mormonism
|
9827_387
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References
|
9827_388
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Sources
|
9827_389
|
Leonard J. Arrington and Davis Bitton, The Mormon Experience: A History of the Latter-day Saints,
|
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(Urbana: 1992).
|
9827_391
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Richard P. Howard, The Church Through the Years, (Herald House: 1992).
|
9827_392
|
Dallin H. Oaks and Marvin S. Hill, "Carthage Conspiracy", (University of Illinois Press).
|
9827_393
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Further reading
|
9827_394
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Matthew Bowman, The Mormon People: The Making of an American Faith Random House (January 24, 2012)
|
9827_395
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Historiography
|
9827_396
|
Turner, John G. "More than a Curiosity: Mormonism and Contemporary Scholarship," Journal of
|
9827_397
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Religion (April 2014) 94#2 pp 229–241. DOI: 10.1086/674956
|
9827_398
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External links
Official website of the LDS Church History Department
|
9827_399
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Open Access Journal of Mormon History
|
9828_0
|
The J-2 is a liquid-fuel cryogenic rocket engine used on NASA's Saturn IB and Saturn V launch
|
9828_1
|
vehicles. Built in the U.S. by Rocketdyne, the J-2 burned cryogenic liquid hydrogen (LH2) and
|
9828_2
|
liquid oxygen (LOX) propellants, with each engine producing of thrust in vacuum. The engine's
|
9828_3
|
preliminary design dates back to recommendations of the 1959 Silverstein Committee. Rocketdyne won
|
9828_4
|
approval to develop the J-2 in June 1960 and the first flight, AS-201, occurred on 26 February
|
9828_5
|
1966. The J-2 underwent several minor upgrades over its operational history to improve the engine's
|
9828_6
|
performance, with two major upgrade programs, the de Laval nozzle-type J-2S and aerospike-type
|
9828_7
|
J-2T, which were cancelled after the conclusion of the Apollo program.
|
9828_8
|
The engine produced a specific impulse (Isp) of in a vacuum (or at sea level) and had a mass of
|
9828_9
|
approximately . Five J-2 engines were used on the Saturn V's S-II second stage, and one J-2 was
|
9828_10
|
used on the S-IVB upper stage used on both the Saturn IB and Saturn V. Proposals also existed to
|
9828_11
|
use various numbers of J-2 engines in the upper stages of an even larger rocket, the planned Nova.
|
9828_12
|
The J-2 was America's largest production LH2-fuelled rocket engine before the RS-25. A modernized
|
9828_13
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version of the engine, the J-2X, was considered for use on the Earth Departure Stage of NASA's
|
9828_14
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Space Shuttle replacement, the Space Launch System.
|
9828_15
|
Unlike most liquid-fueled rocket engines in service at the time, the J-2 was designed to be
|
9828_16
|
restarted once after shutdown when flown on the Saturn V S-IVB third stage. The first burn, lasting
|
9828_17
|
about two minutes, placed the Apollo spacecraft into a low Earth parking orbit. After the crew
|
9828_18
|
verified that the spacecraft was operating nominally, the J-2 was re-ignited for translunar
|
9828_19
|
injection, a 6.5 minute burn which accelerated the vehicle to a course for the Moon.
|
9828_20
|
Components
|
9828_21
|
Thrust chamber and gimbal system
|
9828_22
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The J-2's thrust chamber assembly served as a mount for all engine components, and was composed of
|
9828_23
|
the thrust chamber body, injector and dome assembly, gimbal bearing assembly, and augmented spark
|
9828_24
|
igniter.
|
9828_25
|
The thrust chamber was constructed of thick stainless steel tubes, stacked longitudinally and
|
9828_26
|
furnace-brazed to form a single unit. The chamber was bell-shaped with a 27.5:1 expansion area
|
9828_27
|
ratio for efficient operation at altitude, and was regeneratively cooled by the fuel. Fuel entered
|
9828_28
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from a manifold, located midway between the thrust chamber throat and the exit, at a pressure of
|
9828_29
|
more than . In cooling the chamber, the fuel made a one-half pass downward through 180 tubes and
|
9828_30
|
was returned in a full pass up to the thrust chamber injector through 360 tubes. Once propellants
|
9828_31
|
passed through the injector, they were ignited by the augmented spark igniter and burned to impart
|
9828_32
|
a high velocity to the expelled combustion gases to produce thrust.
|
9828_33
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The thrust chamber injector received the propellants under pressure from the turbopumps, then mixed
|
9828_34
|
them in a manner that produced the most efficient combustion. 614 hollow oxidizer posts were
|
9828_35
|
machined to form an integral part of the injector, with fuel nozzles (each swaged to the face of
|
9828_36
|
the injector) threaded through and installed over the oxidizer posts in concentric rings. The
|
9828_37
|
injector face was porous, being formed from layers of stainless steel wire mesh, and was welded at
|
9828_38
|
its periphery to the injector body. The injector received LOX through the dome manifold and
|
9828_39
|
injected it through the oxidizer posts into the combustion area of the thrust chamber, while fuel
|
9828_40
|
was received from the upper fuel manifold in the thrust chamber and injected through the fuel
|
9828_41
|
orifices which were concentric with the oxidizer orifices. The propellants were injected uniformly
|
9828_42
|
to ensure satisfactory combustion. The injector and oxidizer dome assembly was located at the top
|
9828_43
|
of the thrust chamber. The dome provided a manifold for the distribution of the LOX to the injector
|
9828_44
|
and served as a mount for the gimbal bearing and the augmented spark igniter.
|
9828_45
|
The augmented spark igniter (ASI) was mounted to the injector face and provided the flame to ignite
|
9828_46
|
the propellants in the combustion chamber. When engine start was initiated, the spark exciters
|
9828_47
|
energized two spark plugs mounted in the side of the combustion chamber. Simultaneously, the
|
9828_48
|
control system started the initial flow of oxidizer and fuel to the spark igniter. As the oxidizer
|
9828_49
|
and fuel entered the combustion chamber of the ASI, they mixed and were ignited, with proper
|
9828_50
|
ignition being monitored by an ignition monitor mounted in the ASI. The ASI operated continuously
|
9828_51
|
during entire engine firing, was uncooled, and was capable of multiple reignitions under all
|
9828_52
|
environmental conditions.
|
9828_53
|
Thrust was transmitted through the gimbal (mounted to the injector and oxidizer dome assembly and
|
9828_54
|
the vehicle's thrust structure), which consisted of a compact, highly loaded () universal joint
|
9828_55
|
consisting of a spherical, socket-type bearing. This was covered with a Teflon/fiberglass coating
|
9828_56
|
that provided a dry, low-friction bearing surface. The gimbal included a lateral adjustment device
|
9828_57
|
for aligning the combustion chamber with the vehicle, so that, in addition to transmitting the
|
9828_58
|
thrust from the injector assembly to the vehicle thrust structure, the gimbal also provided a pivot
|
9828_59
|
bearing for deflection of the thrust vector, thus providing flight attitude control of the vehicle.
|
9828_60
|
Propellant Feed System
|
9828_61
|
The propellant feed system consists of separate fuel and oxidizer turbopumps (the bearings of which
|
9828_62
|
were lubricated by the fluid being pumped because the extremely low operating temperature of the
|
9828_63
|
engine precluded use of lubricants or other fluids), several valves (including the main fuel valve,
|
9828_64
|
main oxidizer valve, propellant utilization valve and fuel and oxidizer bleed valves), fuel and
|
9828_65
|
oxidizer flowmeters, and interconnecting lines.
|
9828_66
|
Fuel turbopump
|
9828_67
|
The fuel turbopump, mounted on the thrust chamber, was a turbine-driven, axial flow pumping unit
|
9828_68
|
consisting of an inducer, a seven-stage rotor, and a stator assembly. It was a high-speed pump
|
9828_69
|
operating at 27,000 rpm, and was designed to increase hydrogen pressure from (absolute) through
|
9828_70
|
high-pressure ducting at a flowrate which develops . Power for operating the turbopump was provided
|
9828_71
|
by a high-speed, two-stage turbine. Hot gas from the gas generator was routed to the turbine inlet
|
9828_72
|
manifold which distributed the gas to the inlet nozzles where it was expanded and directed at a
|
9828_73
|
high velocity into the first stage turbine wheel. After passing through the first stage turbine
|
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