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Topic: Atmospheric drag

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	Drag - Wikipedia, the free encyclopedia
		For a solid object moving through a fluid or gas, drag is the sum of all the aerodynamic or hydrodynamic forces in the direction of the external fluid flow.
		Beyond these two kinds of drag there is a third kind of drag, called wave drag, that occurs when the solid object is moving through the fluid at or near the speed of sound in that fluid.
		The overall drag of an object is characterized by a dimensionless number called the drag coefficient, and is calculated using the drag equation.
	en.wikipedia.org /wiki/Drag (197 words)

	Atmospheric drag - Wikipedia, the free encyclopedia
		Atmospheric drag is a form of drag, which is the force that opposes an object moving through a liquid or gas.
		In astrodynamics depending on the situation atmospheric drag can be regarded as inefficiency requiring expense of additional energy during launch of the space object or as a bonus simplifying return from orbit.
		is the body's coefficient of drag (that has to be determined experimentally), A is the body's cross-sectional area, Ï is the air density, and v is the body's velocity.
	en.wikipedia.org /wiki/Atmospheric_drag (108 words)

	Neutral Gases (Site not responding. Last check: 2007-11-06)
		Atmospheric drag and torques due to the motion of a spacecraft through the residual atmosphere are important considerations for satellite lifetime on orbit and for attitude control.
		Drag is a primary determinant of lifetime on orbit for LEO spacecraft, which must compensate by "reboosting" to maintain altitude and avoid reentry.
		At orbital altitudes, the residual atmosphere is sufficiently tenuous that it is considered collisionless, and the spacecraft's interaction with it is considered in terms of free molecular flow, i.e., the incident and emitted fluxes of molecules are considered as independent.
	powerweb.grc.nasa.gov /pvsee/publications/seeov/neugas.html (1035 words)

	Atmospheric reentry biography .ms (Site not responding. Last check: 2007-11-06)
		Atmospheric entry is the transition from the vacuum of space to the atmosphere of any planet or other celestial body.
		Compared with landing on a planet without atmosphere, atmospheric entry has the advantage that no rocket is needed for deceleration.
		Conventional wisdom dictates that aerobraking is best achieved through orienting the returning space craft to fly at a high drag attitude coupled with ultra strong heat shields on the spacecraft, to convert the craft's high kinetic energy into thermal energy (heat) by atmospheric friction.
	reentry.biography.ms (1107 words)

	Low Earth orbit - Wikipedia, the free encyclopedia
		A low Earth orbit (LEO) is a circular orbit around Earth between the atmosphere and the Van Allen radiation belt, with a low angle of inclination.
		Objects in low earth orbit encounter atmospheric gases in the thermosphere (approximately 80-500 km up) or exosphere (approximately 500 km and up), depending on orbit height.
		Atmospheric and gravity drag associated with launch typically add 1,500-2,000 m/s to the delta-V required to reach normal LEO orbital velocity of 7,800 m/s.
	en.wikipedia.org /wiki/Low_Earth_orbit (408 words)

	Glossary : Drag (aka N1) (Site not responding. Last check: 2007-11-06)
		The magnitude of the drag force is directly proportional to the product of the vehicle's cross-sectional area, its drag coefficient, its velocity, and the atmospheric density, and inversely proportional to its mass.
		The effect of drag is to cause the orbit to decay, or spiral downward.
		Drag is the predominant force affecting satellite lifetime.
	www.windows.ucar.edu /glossary/glossary_drag.html (158 words)

	Mars Global Surveyor Aerobraking at Mars
		The post drag state of the spacecraft as well as the orbit determination results from analysis of the radiometric tracking data are important inputs into the aerobraking trajectory control process.
		The dynamic pressure parameter which is related to the force the vehicle experiences as it flies through the atmosphere is easily deduced during the navigation orbit determination process and from accelerometer measurements obtained during an atmospheric drag pass.
		In response, the periapsis altitude of the spacecraft was raised to an altitude of 132 km.
	mars.sgi.com /mgs/sci/aerobrake/SFMech.html (5412 words)

	3.2.3. Atmospheric density modelling.
		Atmospheric density varies with altitude and is highly dependent on solar heating and geomagnetic activity.
		Atmospheric drag models commonly in use for these calculations include the DTM model [ Barlier et al., 1987 ] and the MSIS model [ Hedin, 1987 ].
		The state of the current atmospheric density models for satellite drag modeling is reviewed by Marcos et al., [1993 ] where the influence of surface properties was also evaluated.
	www.agu.org /revgeophys/marsha01/node13.html (510 words)

	The GFS Atmospheric Model description
		The documentation of the GFS atmospheric model as of 2003 is in NCEP Office Note # 442.
		Negative atmospheric moisture values are not filled for moisture conservation, except for a temporary moisture filling that is applied in the radiation calculation.
		The treatment of the gravity-wave drag parameterization in the lower troposphere is improved by the use of the Kim and Arakawa (1995) enhancement.
	www.emc.ncep.noaa.gov /gmb/moorthi/gam.html (4190 words)

	Reentry [Definition] (Site not responding. Last check: 2007-11-06)
		Atmospheric entry is the transition from the vacuum In physics, a vacuum is the absence of matter in a volume of space.
		Compared with landing on a planet without atmosphere, atmospheric entry has the advantage that no rocket A rocket is a vehicle, missile or aircraft which obtains thrust by the reaction to the ejection of fast moving exhaust from within a rocket engine.
		When the cause of the disturbance is moving slowly relative to the speed of sound, the pressure wave enables the fluid to redistribute itself to accommodate the disturbance, and the fluid behaves similarly to an incomp...
	www.wikimirror.com /Reentry (3512 words)

	Trajectory Part 2: Atmosphere Flat-Fire Point-Mass (Site not responding. Last check: 2007-11-06)
		Because of this complexity with an atmosphere that is made up of various gases, the topography of the landscape, and gravity, drag turns out to be a very complicated function of the size, shape, velocity, and angular velocity of the bullet, and of the temperature, density, and altitude of the air through which it moves.
		F is the vector sum of all the atmospheric dynamic forces acting on the projectile, m is the projectile mass, g is the acceleration due to gravity.
		While an atmospheric drag is always in the negative direction to the bullets flight the wind component can be either in the negative or in the positive direction to the bullets flight.
	www.aeroballisticsonline.com /ballistics/trajectory_part_2.html (5182 words)

	Terminal velocity (Site not responding. Last check: 2007-11-06)
		The terminal velocity of an object falling towards the ground is the speed at which the gravitational force pulling it downwards is equal and opposite to the atmospheric drag (also called air resistance) pushing it upwards.
		This equation is derived from the drag equation by setting drag equal to mg, the gravitational force on the object.
		The drag force increases with speed, and always opposes the object’s motion, so if the object is falling, the drag force is upward, and if the object is rising, the drag force is downward.
	www.mywiseowl.com /articles/Terminal_velocity (476 words)

	Drag and solar radiation (Site not responding. Last check: 2007-11-06)
		The atmospheric drag is dependent on the atmospheric density, which varies significantly along the orbit, because of changes in the satellite's altitude and geomagnetic influences, but also from day to day, depending mainly on the solar activity.
		Both atmospheric drag and solar radiation pressure act upon a large satellite with a complex shape, of which the attitude varies along the orbit.
		To compute the drag, the effective cross-sectional area A is determined, based on the area and orientation of the panels with respect to the satellite's velocity vector.
	www.deos.tudelft.nl /ers1/operorbs/node5.html (336 words)

	Contract Abstracts (Site not responding. Last check: 2007-11-06)
		The use of atmospheric plasma to sterilize/decontaminate instrumentation contaminated with biofilms is a new application of a proved baseline technology.
		Atmospheric Glow Technologies proposes to solve this inadequacy of filter regeneration by developing a cost effective and efficient metallic filter which will remove substantial concentrations of diesel soot by the generation of the patented One Atmosphere Uniform Glow Discharge Plasma (OAUGDP®) which can be fun continuously or intermittently to meet demands of emission reduction.
		In order for the plasma actuator to be utilized on aircraft to modify the flight performance, i.e., reduce drag or increase attack angles, the surface flow controller's induced surface airflow velocity must be increased by a magnitude of two to five.
	www.atmosphericglow.com /b2c5.html (3887 words)

	RSE 24
		Drag was mentioned in several texts, and but nothing specific was stated, I felt that a balance must be struck between drag loss and gravity loss to obtain the best thrust profile.
		Factoring in the atmospheric drag was the last step in determining the optimum thrust profile for a launch vehicle.
		You have to design the nose of the rocket to withstand the force of drag, and the heat of air friction, and as a negative force to thrust, but drag can be largely ignored for any practical thrust profile.
	web.wt.net /~markgoll/rse24.htm (518 words)

	Atmospheric Drag Density Data from AD-A, AD-B, and AD-C (Site not responding. Last check: 2007-11-06)
		This experiment was designed to determine nonsystematic changes of upper atmospheric density by conducting studies of the drag on a 3.6-m diameter, low-density sphere caused by short-term variations in solar activity.
		The general techniques used to deduce density values from satellite drag data can be found in L. Jacchia and J. Slowey, 'Accurate drag determination for eight artificial satellites of atmospheric densities and temperatures,' Smithsonian Astrophysical Observatory special report no. 100, Cambridge, Mass., July 1962.
		Predicted world maps and atmosphere drag density tables on microfiche are archived at NSSDC.
	gcmd.gsfc.nasa.gov /records/GCMD_AD-ABC.html (207 words)

	MCC Answer (Site not responding. Last check: 2007-11-06)
		However, the largest contributor to orbital decay is atmospheric drag.
		Atmospheric drag is dependent on the density of the atmosphere at the given orbital altitude.
		Atmospheric density is primarily affected by solar flux and the seasons -- so it is constantly changing.
	spaceflight.nasa.gov /feedback/expert/answer/mcc/exp7/08_07_10_23_16.html (294 words)

	Skin Friction and Roughness Drag
		Atmospheric data may be computed in the atmospheric calculator included here.
		The drag assigned to roughness also implicitly accounts for all other sources of drag at zero lift that are not explicitly included.
		This category includes interference drag, some trim drag, drag due to unaligned control surfaces, drag due to landing gear door gaps, and any excess drag of the individual surfaces.
	adg.stanford.edu /aa241/drag/skinfriction.html (670 words)

	Naval Network and Space Operations Command - Tracking of Space Objects (Site not responding. Last check: 2007-11-06)
		The Navy is using a space sensor capable of measuring upper atmospheric drag effects on satellites to help analysts predict their orbits with greater precision.
		Molecules that have no electrical charge, along with oxygen ions, are the components in the upper atmosphere that most directly impact the amount of atmospheric drag on satellites and other objects orbiting the Earth.
		Drag on LEO objects is the largest source of error in orbit determination, primarily because of the inaccuracy of upper atmospheric density estimates.
	www.nnsoc.navy.mil /news/lorass.htm (1149 words)

	Space Vehicle Maneuver (Site not responding. Last check: 2007-11-06)
		Atmospheric drag is undesirable for certain spacecraft such as Earth orbiting satellites, since extra energy is needed to overcome the frictional force.
		When the drag is used to slow down and the space vehicle is captured into the satellite orbit of the planet, it is called aerocapture.
		To effectively take advantage of the atmospheric drag the spacecraft is covered with a surface layer called the heat shield.
	ares.ame.arizona.edu /microsensors/orbit.html (194 words)

	[No title]
		Drag functions relate the velocity of the bullet to the aerodynamic drag at that velocity.
		Atmosphere Model, specify either 'Use ICAO' for the International Civil Aviation Organization atmosphere model, or 'Use Army Standard Metro' for the older atmosphere used by Army Ordnance from 1905 to 1960 and is still used today by the U.S. sporting commercial ammunition industry.
		The Yaw Drag Coefficient is a measure of atmospheric retardation of the forward motion of the projectile due to that component of the projectile face shown to the air that is offset from a nonzero yaw angle.
	www.cartestsoftware.com /jballistics/jbtourdo.html (12740 words)

	@TITLE = SPACE ENVIRONMENT (Site not responding. Last check: 2007-11-06)
		Approximately 99 percent of the atmosphere is in the stratosphere and troposphere.
		The temperature of the atmosphere in the mesosphere decreases as the altitude increases.
		Atmospheric drag causes a satellite to slow down, thus the satellite "falls" to a lower altitude to gain velocity.
	www-tradoc.army.mil /dcscd/chap5im.htm (7499 words)

	:: NASA Quest > Aerospace :: (Site not responding. Last check: 2007-11-06)
		Extra drag is created when an aircraft flies near to or faster than the speed of sound (at transonic and supersonic speeds).
		Thrust is created by pushing some of the surrounding atmosphere back with greater velocity, or by adding extra material with high velocity to the atmosphere.
		From buoyancy to the four forces to atmospheric differences, many factors must be considered before actually designing an aircraft to fly through the atmosphere of Mars.
	quest.arc.nasa.gov /aero/planetary/atmospheric/summary.html (410 words)

	Max-Planck-Institut für Meteorologie (Site not responding. Last check: 2007-11-06)
		The strength of the atmospheric forcing is modified by including atmospheric surface-layer physics, which is itself directly dependent on the instantaneous sea-ice condition provided by the sea-ice model.
		In earlier applications, the atmospheric drag on sea ice was computed from the local momentum transfer over ice.
		The large-scale roughness length, on the other hand, depends on the local skin drags and on the form drag, where the latter is given as a function of the ice-plus-snow freeboard and the ice concentration, both provided by the sea-ice model.
	www.mpimet.mpg.de /de/web/science/rep_abstract.php?id=95 (236 words)

	Physics 1020
		The situation at the other end of the hose is P2 = atmospheric pressure, h2 = 0 (the hose is still at ground level), and we want to solve for v2.
		The reason that the bicycle rider does not have to peddle as hard is due to the pressure drag behind the truck resulting from turbulent air flow as well as a reduction in air resistance.
		When we wet the ball we reduce the ability of the fuzz to disrupt the boundary layer and the pressure drag is increased.
	www.colorado.edu /physics/phys1020/phys1020_sp02/HW14Soln.html (796 words)

	Space Technology 7
		On ST7, isolated test masses inside the spacecraft are shielded from the atmosphere, so their orbit is unaffected by the drag.
		When the spacecraft is forced to follow the test masses, it too orbits as if it were not subject to atmospheric drag.
		ST7 will fly far beyond the atmosphere, so atmospheric drag is not a concern, but other smaller noise forces are.
	nmp.jpl.nasa.gov /st7/ABOUT/concept2.html (503 words)

	Numerical Calculation of a Baseball Trajectory
		Because the ball is spherical and probably has little spin, the aerodynamic force is nearly all drag and acts opposite to the direction of velocity.
		Because the drag is a non-linear function of velocity, we will not be able to find an analytic solution and a numerical solution will be necessary.
		The traditional way to express the drag of an object such as a sphere is through a drag coefficient defined as the drag force divided by the product of the frontal area and the dynamic pressure.
	www.pdas.com /bb2.htm (848 words)

	Experimental Studies on Atmospheric Pressure Glow discharge for Drag Reduction and Microwave invisibility (Site not responding. Last check: 2007-11-06)
		The plasma assisted stealth technology and air drag reduction with boundary layer flow control on moving aircrafts are of major importance and interest in the field of aerodynamics.
		The air drag reduction is possible because the plasma constituents i.e.
		We have produced the atmospheric pressure glow discharge plasma in helium gas covering a volume between dielectric covered parallel-plates and also a planar surface that is required for aerodynamic applications.
	www.aeroindiaseminar.com /Ganesh.htm (335 words)

	JPL.NASA.GOV: If Santa Were a Martian
		The region between the polar vortex and the rest of the atmosphere is called the 'transition zone.' In this zone, strong winds swirl around the pole and the zone itself weaves in and out in the typical fashion of a terrestrial jet stream.
		Scientists and engineers have long known that Mars' atmosphere "breathes" -- moving up and down, growing or decreasing in density with the effects of dust storms, winds and other influences.
		With concerns about atmospheric changes that any pilot could relate to, "it might be said this is as close as we've ever come to flying on another planet," said Dr. Richard Zurek of JPL, who co-chairs the atmospheric advisory group to the project.
	www.jpl.nasa.gov /news/features-print.cfm?feature=544 (681 words)

	Mars Exploration Rover Mission: Features
		Over a three-month period that ends in January, Odyssey's orbit is being lowered and circularized through aerobraking, carefully designed passes through the top of the atmosphere that slow the spacecraft through the effects of atmospheric drag.
		They depend upon Mars Global Surveyor and Odyssey data to assess martian atmospheric behavior, with a special watch for the large martian dust storms which can increase in a big way the air density at aerobraking altitudes of about 100 kilometers, or about 60 miles.
		In planning each aerobraking pass through the atmosphere, the team walks a fine line between getting the desired amount of drag out of the pass without subjecting the spacecraft to overheating from unforeseen pockets of dense air.
	marsrovers.jpl.nasa.gov /spotlight/polarvortex02.html (291 words)

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