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The flight crew can select primary or vernier RCS thrusters for attitude control in orbit. Normally, the vernier thrusters are selected for on-orbit attitude hold. ... The forward RCS had 14 primaries and two vernier engines. The aft RCS had 12 primary and two vernier engines in each pod. The primary
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family (prior to the Atlas III), in addition to maneuvering, the verniers were used for roll control, although the booster engines could also perform this function. After main engine cutoff, the verniers would execute solo mode and fire for several seconds to make fine adjustments to the vehicle
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Due to their weight and the extra plumbing required for their operation, vernier rockets are seldom used in new designs. Instead, as modern rocket engines gained better control, larger thrusters could also be fired for very short pulses, resulting in the same change of
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RCS engines provided 870 pounds of vacuum thrust each, and the verniers provided 24 pounds of vacuum thrust each. The oxidizer-to-fuel ratio for each engine is 1.6-to-1. The nominal chamber pressure of the primary thrusters was 152
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On space vehicles with two sizes of attitude control thrusters, the main ACS (Attitude
Control System) thrusters are used for larger movements, while the verniers are reserved for smaller adjustments.
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Vernier thrusters are used when a heavy spacecraft requires a wide range of different thrust levels for attitude or velocity control, as for maneuvering during docking with other spacecraft.
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attitude. The Thor/Delta family also used verniers for roll control but were mounted on the base of the thrust section flanking the main engine.
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67:. Depending on the design of a craft's maneuvering and stability systems, it may simply be a smaller thruster complementing the main
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had thrust vectoring nozzle, only three were equipped with this feature and only ignited a brief moment during the ascent).
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rocket also used the LR-101 for vehicle roll maneuver since one engine cannot do a roll maneuver (although the later
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modules with twin vernier nozzles each, and the central RD-108 with four steerable vernier thrusters
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were used for roll control and to fine-tune the vehicle attitude after the main engine cutoff. The
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for vehicle maneuvering because the main engine is fixed in place. For earlier versions of the
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s VRCS for a duration of 33 minutes to attain an orbit between 180.5 and 190.0
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363:"STS-130 prepares for undocking – MMOD impact on hatch cleared"
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had six vernier engines or thrusters in its "Vernier
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281:. NASA's Glenn Research Center. Archived from
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279:"Rocket Control: Examples of Controls"
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35:Vernier thrusters on the side of an
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75:thrusters, or may be a part of the
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361:Bergin, Chris (19 February 2010).
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310:. NASA Kennedy Spaceflight Center
212:while docked: for example during
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71:, or it may complement larger
16:Rocket engines for maneuvering
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400:. You can help Knowledge by
59:for fine adjustments to the
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452:Spacecraft attitude control
396:This rocketry article is a
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210:International Space Station
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79:. The name is derived from
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308:"Reaction Control Systems"
235:(334.3 and 351.9 km).
337:"LR-101 VERNIER ENGINE"
202:Reaction Control System
77:reaction control system
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447:Spacecraft components
365:. NASAspaceflight.com
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168:Proton rocket family
148:Zenit rocket family
129:, showing the four
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251:Cold gas thruster
140:R-7 rocket family
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285:on March 7, 2011
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256:Vernier throttle
246:Space propulsion
81:vernier calipers
73:attitude control
45:vernier thruster
27:vernier thruster
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367:. Retrieved
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312:. Retrieved
289:December 30,
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283:the original
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218:George Zamka
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110:Atlas rocket
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369:20 February
222:Terry Virts
175:SM-65 Atlas
441:Categories
314:2011-10-03
262:References
220:and pilot
216:commander
162:, and the
53:spacecraft
51:used on a
227:Endeavour
187:Delta III
240:See also
183:Delta II
117:Examples
99:momentum
65:velocity
61:attitude
23:A 1960s
346:24 June
214:STS-130
173:On the
166:on the
164:RD-0214
158:on the
146:on the
224:fired
191:GEM 46
177:, the
156:RD-856
152:RD-855
150:, the
131:RD-107
127:Soyuz
47:is a
398:stub
371:2010
348:2017
322:psia
291:2011
206:VRCS
196:The
185:and
160:R-36
154:and
144:RD-8
138:The
233:nmi
204:" (
106:R-7
63:or
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