Thrusters

Semi-submersible rigs are often referred to as semis , and are a floating type of rig. Like the jack-up, a semi is self contained. The structure is supported by large pontoons which are ballasted with water to provide the required stability and height. The rig is held in position by anchors and mooring lines or dynamically positioned by thrusters. A large diameter steel pipe ( riser ) is connected to the sea-bed and serves as a conduit for the drill string. The blowout preventer (BOP) is also located at the sea-bed ( sub sea stack ). 

Drill ships are used in deep water and remote areas, and these vessels are equipped with a drilling unit positioned in the middle of the ship. Positioning is achieved dynamically by computer controlled thrusters. The ample storage space allows operation for long periods of time without re-supply. 

Other examples of government and military applications of laser-based profilometry include the evaluation of rocket thruster nozzles to locate and measure flame erosion remote inspection of hypervelocity test track and the measurement of sludge deposits on tube internal surfaces. 

Arc furnaces Archery bows Archimedes number Architectural fabrics Architectural lamnates Arc-jet thrusters... 

Harding, J. T., Kazarof, J. M., and Appel, M. A., Iridium-coated Rhenium Thrusters by CVD, NASA Technical Memo. 101309, NASA Lewis Res. Cent., Cleveland, OH (1988)... 

Iridium Coating for Spacecraft Rocket Nozzles. The coating of rocket nozzles with iridium is a good example of the ability of CVD to provide a complete composite material, in this case a structural refractory shell substrate coated with a corrosion- and oxidation-resistant component. The device is a thruster rocket nozzle for a satellite. The rocket uses a liquid propellant which is a mixture of nitrogen tetroxide and monomethyl hydrazine. 

Main uses. Caesium metal is used in the production of vacuum tubes as a scavenger to reduce residual gaseous impurities after the tubes have been sealed. Cs may be generated in situ by heating a pellet of caesium chromate mixed with a metal powder (Zr, Ca, Ba). Cs metal is used as the propellant in ion thrusters (employed in satellites for orientation control) it is ionized in a vacuum chamber, the Cs+ are then accelerated through a nozzle (high specific impulse because of high atomic mass). 

Thrusters of pumps, hot water pumps. .. Bearings (PTTE lubricated)... 

PATR 3449 S. Vishnefsky, "Feasibility Study of Side Thruster for MAW System (Aug 1966)... 

The use of N2H4 as a hypergolic propellant fuel for rocket propulsion is discussed in detail in this Vol under Hypergolic Propellants. It has also been used extensively as a monopropellant fuel or in combination with hydrazine nitrate and/or water as a thruster for maneuvering space vehicles (Ref 31)... 

The use of N2H<, as a hypergolic rocket fuel is described under the topic Hypergolic Propellants in this Vol. Another major research effort has seen the development of hydrazine thruster rockets based upon the catalytic de-... 

P.l. Moynihan, Minimum Impulse Tests of 0.45-N Liquid Hydrazine Catalytic Thrusters, ... 

More sophisticated uses of LP, which take advantage of the LP engine s capability of being throttled and restarted, are in thrusters. 

Thrusters are rockets for maneuvering and controlling the attitude of space vehicles. The usual monopropellant for thrusters is catalytically decomposed Hydrazine. The usual catalysts are iridium, rhodium or ruthenium and their mixts. For a review of Hydrazine thrusters see Refs 33, 34 35. Russi (Ref 34) emphasizes that, in spite of many studies and the general acceptance and apparent success of hydrazine thrusters, new rocket motor design is still largely empirical. A biproplnt consisting of Hydrazine mixed with Hydrazine Nitrate has also been tried in thrusters but is no longer popular... 

A Survey of Monopropellant Hydrazine Thruster Technology , Aerospace Corp, San Bernadino, Calif (1974) 35) R. Meetin ... 

Chemists are not alone. The Mars Climate Orbiter crashed into Mars in September 1999 following a confusion in programming of software that modeled forces in English units instead of the metric units that were expected by the thruster controllers and other programs. This incident is related in the delightfully titled NASA document Mars Climate Orbiter Mishap Investigation Report. (Stephenson 1999) The mishap cost around 125,000,000. 

With the advent of the B-52 plane and its requirements for multi-crew, multi-function, integrated escape systems, there was developed (ca 1951. a device which Could furnish thrust to position ejection seats and to unlock hatches. This device became known as thruster and since... 

BJStroking Devices. They may be subdivided into "open and "closed CAD s. In the first type (such as in catapults and removers), there is separation of piston from cylinder, accompanied by escape of proplnt gases(See illustration on p 6 of Ref 14). In the "closed" types(such as used in thrusters and ejectors), the piston does not separate from the cylinder and the gas does not escape into atmosphere,but may be bypassed to other CAD s. Function of catapult remover... 

Cartridge Thruster. See under Cartridge-Actuated Deuces... 

Thrust see Amyl nitrite Inhalants Thrusters see Amphetamines Thunder see GBL Tic see PCP (phencyclidine)... 

Applications. To date, the liquid propellant systems used in chemical propulsion range from a small trajectory control thruster with only 0.2 lbf (0.89 N) thrust for orbital station-keeping to large booster rocket engines with over l. 0 million lbf (4.44 MN) thrust. Bipropellant propulsion systems are the most extensively used type today for... 

Fig. 37.19. (a) Small thruster used in Milstar and (b) high thrust-to-weight liquid oxygen/kerosene engines for commercial launch vehicles. (Courtesy Aerojet Propulsion)... 

Lozano, P. C. Studies on the Ion-Droplet Mixed Regime in Colloid Thrusters. Ph.D. Thesis [Online], Massachusetts Institute of Technology, Cambridge, MA, January 2003. http //theses.mit.edU/Dienst/UI/2.0/Describe/0018.mit. etheses%2f2003-l (accessed Nov 7, 2004). 

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