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	Pogo oscillation -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-11)
		Pogo oscillation is the term for a potentially dangerous type of ((physics) a regular periodic variation in value about a mean) oscillation found in (A jet engine containing its own propellant and driven by reaction propulsion) rocket engines.
		Although the term is frequently written POGO, it is not an (A word formed from the initial letters of a multi-word name) acronym, but in fact a reference to the bouncing of a (Plaything consisting of a pole with foot rests and a strong spring; propelled by jumping) pogo stick.
		Pogo was also the cause of some of the problems experienced by (additional info and facts about Apollo 6) Apollo 6.
	www.absoluteastronomy.com /encyclopedia/p/po/pogo_oscillation.htm (268 words)

	Pogo oscillation - TheBestLinks.com - Hertz, Rocket, Positive feedback, Resonant frequency, ... (Site not responding. Last check: 2007-10-11)
		Pogo oscillation is the term used to describe longitudinal oscillations in a rocket during launch.
		Pogo results when the propellant feed lines and storage systems of a rocket have a resonant frequency close to the the longitudinal resonant frequency of the rocket structure, which results in oscillation of the fuel in the feed lines, creating a positive feedback situation in which the oscillating fuel flow causes additional longitudinal vibration.
		Pogo is typically suppressed by the inclusion of damping mechanisms, such as accumulators, in the propellant feed lines that dampen out the vibrations.
	www.thebestlinks.com /Pogo_oscillation.html (214 words)

	What is Pogo? (Site not responding. Last check: 2007-10-11)
		The pogo oscillation typically falls in the range of 5–60 hertz (cycles per second) and tracks the slowly changing frequency of the vehicle's vibration.
		Pogo is a particular concern for piloted vehicles because, depending on the frequency, oscillations as low as 0.25 g's in amplitude can impair an astronaut's ability to read instrument panels.
		Typically, pogo occurs when the natural frequency of a propellant feed line, which is primarily controlled by cavitation bubbles caused by the operation of an engine pump, comes close to a readily excited natural frequency of longitudinal structural vibration.
	www.aero.org /publications/crosslink/winter2004/05_sidebar1.html (238 words)

	Rocketdyne Technical Consulting Threshold Journal: Pogo
		While the Jupiter oscillations were not pogo, they were the first hint of the importance of inlet pressure and cavitation on tuning feed line resonant frequencies in the vehicle problems that would follow.
		The large oscillations at the fuel pump were puzzling and were assumed to be caused by some type of coupling through the vehicle structure.
		The oscillations occurred at 105-140 seconds after liftoff, at 5 Hz, with an amplitude of 1/3 G at the aft of the vehicle where the five F-1 engines were located.
	www.engineeringatboeing.com /articles/pogo.htm (3898 words)

	Clavius: Vehicles - pogo and the saturn v
		"Pogo" is a rocket scientist's slang for a longitudinal vibration or oscillation that sometimes occurs in rockets.
		Engineers eliminate pogo either by adjusting the frequencies at which the structure or propellants vibrate, or by "damping" the vibration in either or both.
		Pogo in turn introduces a different kind of combustion instability in the engine, but it has nothing to do with the standing-wave type of instability.
	www.clavius.org /techsvpogo.html (1172 words)

	Pogo oscillations (Henry Spencer)
		It's an oscillation in which surges in engine thrust cause surges in acceleration, which cause surges in fuel pressure in the plumbing, which cause surges in flow rates, which cause surges in engine thrust.
		Pogo damping was added to the Saturn V first stage's outboard engines after Apollo 6; it turned out that suitable chambers already existed in the valves, so merely filling them with helium was all that was necessary.
		A fix (a Pogo suppressor on the center engine) was in the pipeline, but 13's booster had already been stacked and retrofitting it was awkward, so they decided not to bother.
	yarchive.net /space/rocket/pogo.html (2315 words)

	Mitigating Pogo on Liquid-Fueled Rockets
		Accelerations induced by pogo were a critical factor in the human-flight rating of the Titan II launch vehicle.
		Pogo presented serious challenges for the developers of Titan II and remains a prime consideration in the design of launch vehicles today.
		The pogo model with the estimated pump parameters supported the hypothesis that the high accelerations on the earlier missions were caused by interaction of the launch vehicle/space vehicle structure with the propulsion system during periods when the oxidizer pump was undergoing unsteady cavitation.
	www.aero.org /publications/crosslink/winter2004/05.html (2418 words)

	Apollo Expeditions to the Moon: Chapter 9 (Site not responding. Last check: 2007-10-11)
		Pogo oscillation subjects the entire space-vehicle stack to stresses and strains that, under certain circumstances, can grow to a magnitude sufficient to damage or even destroy the vehicle.
		This motion, caused by a synchronization of engine thrust pulsations with natural vibration frequencies of the vehicle structure, tends to be self-amplifying as the structural oscillations disturb the flow of propellants and thus magnify the thrust pulsations.
		The second anomaly, loss of structural panels from the lunar module adapter (the structural section that would house the lunar module), was originally thought to have been caused by the pogo oscillations.
	www.etsimo.uniovi.es /solar/history/SP-350/ch-9-1.html (686 words)

	Apollo Expeditions to the Moon: Chapter 3 (Site not responding. Last check: 2007-10-11)
		This "pogo" oscillation (the name derived from the child's toy) would be felt particularly strongly in the command module.
		Analysis, supported by data collected in engine tests, confirmed that the oscillation was caused by resonance coupling between the springlike elastic structure of the tankage, and the rocket engines' propellant-feed systems.
		Susceptibility to pogo (a phenomenon not unknown to missile designers) had been thoroughly investigated by the Saturn stage contractors, who had certified that their respective designs would be pogo-free.
	www.hq.nasa.gov /office/pao/History/SP-350/ch-3-5.html (297 words)

	Moonport, Ch20-3
		In the closing seconds of the first stage burn, the vehicle went through 30 seconds of severe longitudinal oscillation - the pogo effect, it was called, because the space vehicle vibrated up and down like a child's pogo stick.
		In a gross sense it is the interaction between the various frequencies that causes the vehicle to oscillate.
		The results indicated that any pogo effect could be suppressed by detuning the natural frequencies of the propellant feed system and the vehicle structure.
	www.hq.nasa.gov /office/pao/History/SP-4204/ch20-3.html (1171 words)

	info: Pogoing (Site not responding. Last check: 2007-10-11)
		Pogoing is a dance move or series of moves where one tends to jump up and down, with arms at one's sides.
		Before coming on as bassist, Vicious was an extremely loyal fan of the band and started 'the pogo' as an attempt to see over the crowd at the increasingly-populated Sex Pistols gigs.
		During the mid-90's many bands, desiring to be viewed with a 'classic punk' image (as opposed to all the more-rampant offshoots), embraced the pogo as a sign of true punk and its roots.
	www.info-assicurazione.com /Pogoing.html (704 words)

	Engineering Case Library (Site not responding. Last check: 2007-10-11)
		When the Titan missile was considered as a booster for manned spacecraft, a severe problem of longitudinal oscillations up to 5 g's was encountered.
		The cause and cure of this oscillation were unknown.
		After 3 million dollars worth of study of this "Pogo bounce" it was identified as a coupled oscillation between the structure and the propulsion system.
	www.civeng.carleton.ca /ECL2/view_case.php?id=1286 (86 words)

	Titan 2
		This was the eleventh Titan II flight and the third to use increased pressure in the propellant tanks of stage I to reduce longitudinal oscillations (POGO).
		The main problem was that POGO level satisfactory in the weapon system was too high to meet NASA standards for the Gemini program, and further reduction in the POGO level required a much more elaborate and extensive analytic and experimental program than had so far been considered necessary.
		Before GLV-2 was erected in the vertical test facility, a longitudinal oscillation (POGO) kit was installed in stage I. The kit comprised an oxidizer standpipe and a fuel surge chamber designed to suppress pressure pulses in the propellant feed lines and thus reduce POGO to a level consistent with manned flight.
	www.friends-partners.org /partners/mwade/lvs/titan2.htm (17389 words)

	Chapter 8 - Hydrodynamics of Pumps - Christopher E. Brennen (Site not responding. Last check: 2007-10-11)
		Instead the oscillations would persist until the cavitation number was raised to the value at the point C where the disappearance of auto-oscillation would cause recovery to the point D.
		The frequency of partial cavitation oscillation on a single foil is usually less than 0.1 U/c, where U is the velocity of the oncoming stream, and c is the chord length of the foil.
		It is, however, important to note that the dynamics of the cavitating inducer pumps are crucial in determining the limits of these Pogo instabilities, and provide one of the main motivations for the measurements of the dynamic transfer functions of cavitating inducers described in chapter 9.
	caltechbook.library.caltech.edu /22/01/chap8.htm (12194 words)

	Apollo 8 (Site not responding. Last check: 2007-10-11)
		When it was erected in the Vertical Assembly Building on 20 December 1967, it was thought that the rocket would be used for an unmanned test flight carrying a boilerplate Command/Service Module.
		Although Apollo 6 had suffered several major problems (it suffered severe pogo oscillation during its first stage and two second stage engines shutdown early), Marshall Space Flight Center, in charge of the Saturn V, was confident that it could solve all the issues without the need for another unmanned test flight.
		Towards the end of the second stage burn, the rocket underwent pogo oscillations that Frank Borman estimated were of the order of 12 Hz and about Â±0.25 g (Â±2.5 m/sÂ²).
	www.donob.com /encyclopedia/Apollo_8 (6573 words)

	Combustion instability (Doug Jones; Henry Spencer)
		Pogo oscillation is extremely common (although not quite universal) in substantial rockets built without Pogo suppressors, but that isn't where the F-1 had its real problems.
		Basically, oversimplifying somewhat, details of injector design fix the frequencies where the engine is most vulnerable to high-frequency oscillation, and if the major resonant frequencies of the chamber are above them, problems are unlikely.
		That's when you get an oscillation resonating within the chamber, as a standing or travelling wave with a wavelength some fraction of one of the chamber's dimensions.
	yarchive.net /space/rocket/combustion_instability.html (2149 words)

	Chariots For Apollo, ch10-6
		Also, five years earlier, in 1963, pogo had threatened to end the Gemini program when the Titan II suffered this phenomenon on launch after launch.
		The lower oscillation was probably the result of carrying just "a hunk of junk," to simulate lunar module weight, on the earlier flight.
		At one time during the pogo studies, Lee B. James (who had replaced Rudolph as the Huntsville Saturn V manager) said, 1,000 engineers from government and industry were working on the problem.
	www.apolloexplorer.co.uk /books/SP-4205/ch10-6.html (1405 words)

	On The Shoulders of Titans - Ch7-2
		Every Titan II so far flown had displayed Pogo, although the level had varied, reaching a low of just over one-third the force of gravity (±0.35g) in the 17th test flight on 13 May 1963.
		With this statement as a basis, MSC and SSD were to arrange a formal agreement on the goals of reduced Pogo, a stable second-stage engine, and improved engines.
		That was small consolation, however; Pogo reached plus or minus 0.75g, very nearly the worst since the disastrous flight of Missile N-11 in December 1962.
	history.nasa.gov /SP-4203/ch7-2.htm (3067 words)

	Tennis Tutor PLus Model 4 Review - Talk Tennis
		Also, the random oscillation simulates real match play: the balls come unpredictably and you have to use good footwork.
		The random oscillation is a true workout because you don't know when the ball will pop.
		I know one problem with old tennis ball machines I used to use is that they just oscillated left-right with no varying depth, which is very "unrealistic" and can be boring.
	tt.tennis-warehouse.com /showthread.php?t=53875 (2777 words)

	Which one should I choose? Little Prince 1 or Tennis Tutor Plus 2? - Talk Tennis
		I have been using sam sp-4 more than a month sam tennis ball machines are very solid and reliable.
		I mean, it has tripple oscillation, which varies the DEPTH of the ball as well as the left-right action, whereas the SAM and Tennis Tutors only vary left-right.
		Triple oscillation is a great feature of a family who enjoy playing tennis but not for the serious tennis player.
	tt.tennis-warehouse.com /showthread.php?t=54424 (1254 words)

	Apollo Expeditions to the Moon: Chapter 10
		Folded and stowed as it was in the nose of the Saturn V, its frail body caused some concern about its ability to stand up to the stress of a Saturn launch.
		Some of the earlier Saturn launches had shown what was called a pogo oscillation, named after the pogo-stick phenomenon.
		We wanted to make certain that the LM would be able to take that longitudinal acceleration and shock.
	history.nasa.gov /SP-350/ch-10-3.html (646 words)

	POGO
		This "pogo" oscillation (the name derived from the child's toy) would be felt
		The pogo transposable element family of Drosophila melanogaster.
		The pogo mouse is a novel neurological mutant, which was discovered,
	www.mongabay.com /reference/environment/POGO.html (165 words)

	Www pogo com - Comic creator: Walt Kelly (Site not responding. Last check: 2007-10-11)
		Over the years Pogo often referred to Georgia and to several of the For all its superficial identification with Georgia and the South, Pogo was a comic
		Pogo Linux, the first vendor to be named a MySQL Certified Hardware Partner, Read the answers to some frequently asked questions about the Pogo Linux
		It was during his time at Dell that he created the character of Pogo, a possum.
	agesites.com /agss/www-pogo-com.html (257 words)

	[No title]
		The excessive usage observed during the STS-3 post-landing engine purge was not experienced on this flight, probably as a result of the replacement of a defective L02 POGO recirculation check valve.
		The vehicle response was bounded by oscillations in each axis with peak amplitudes reasonably close to preflight predictions.
		The vehicle was damping a low -amplitude pitch oscillation on prefinal, and the body flap went to trail.
	members.aol.com /WSNTWOYOU/STS4MR.HTM (14592 words)

	Apollo 6
		The primary objectives of the mission were to demonstrate structural and thermal integrity and compatibility of the launch vehicle and spacecraft, confirm launch loads and dynamic characteristics and verify stage separations, propulsion, guidance and control, electrical systems, emergency detection system and mission support facilities and operations, including Command Module recovery.
		The Saturn V structure underwent a severe pogo oscillation, without damage to the spacecraft structure.
		Due to a manufacturing flaw, structural panels were lost from the Lunar Module adapter.
	home.online.no /~cvogt/apollo_6.htm (205 words)

	Untitled Document (Site not responding. Last check: 2007-10-11)
		Two minutes and five seconds after launch, the Saturn V structure underwent a severe pogo oscillation, without damage to the spacecraft structure.
		Due to a manufacturing flaw and unrelated to the pogo oscillations, structural panels were lost from the lunar module adapter.
		Finally, after the completion of first stage firing and part way through the second stage burn, two of the five second stage J-2 engines shut down prematurely.
	www.sierratel.com /patplc/Apollo6.htm (353 words)

	HSF - The Shuttle (Site not responding. Last check: 2007-10-11)
		The main engines are reusable, high-performance, liquid-propellant rocket engines with variable thrust.
		A pogo suppression system prevents engine thrust oscillation.
		Each controller operates in conjunction with other components to provide a self-contained system for engine control, checkout and monitoring.
	www.stsliftoff.com /Documents/shutref/orbiter/prop (157 words)

	:: oscillation :: related - ( dynamic tribology testing high frequency friction ...
		:: oscillation :: related - (dynamic tribology testing high frequency friction test rig wear tester) by Spell-Dictionary
		dynamic tribology testing high frequency friction test rig wear tester pacific decadal north atlantic parasitic madden julian oft astm d57 southern el nino arctic index reflectivity pogo
		oft oscillation friction wear test rig astm d57
	www.spell-dictionary.com /db/oscillation (103 words)

	[No title] (Site not responding. Last check: 2007-10-11)
		The Orbiter fuel cell 1 condenser exit temperature cycled between 147 deg and 165 deg F throughout launch and during the mission.
		This oscillation had no effect of fuel cell operation or impact on the mission.
		At external tank (ET) separation, the right aft reaction control system (RCS) experienced two anomalies.
	members.aol.com /WSNTWOYOU/STS22MR.HTM (1608 words)

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