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Topic: Atmospheric reentry

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	Atmospheric reentry Summary
		Atmospheric reentry is the process by which vehicles that are outside the atmosphere of a planet can enter that atmosphere and reach the planetary surface intact.
		The technology of atmospheric reentry was a consequence of the Cold War.
		Atmospheric reentry was successfully developed, which made possible nuclear-armed intercontinental ballistic missiles.
	www.bookrags.com /Atmospheric_reentry (8737 words)

	Britain.tv Wikipedia - Atmospheric re-entry
		Atmospheric reentry is the process by which vehicles that are outside the atmosphere of a planet can enter that atmosphere and reach the planetary surface intact.
		The technology of atmospheric reentry was a consequence of the Cold War.
		Atmospheric reentry was successfully developed, which made possible nuclear-armed intercontinental ballistic missiles.
	www.britain.tv /wikipedia.php?title=Atmospheric_re-entry (7854 words)

	Spacecraft Reentry Breakup Overview and FAQs
		Although many people believe that satellites burn up during atmospheric reentry, some satellite components can and do survive the reentry heating (of course, satellites like the space shuttle orbiter survive reentry entirely because they are protected by specially designed heat shields).
		During reentry, the object is decelerating quickly and the loads on the structure can exceed 10 Gs (10 times the acceleration of gravity).
		Reentry risk estimates are supported by the fact that, over the last 40 years, more than 5,400 metric tons of materials are believed to have survived reentry with no reported casualties (of course, it is possible that casualties have occurred somewhere in the world, but have not been reported).
	www.aero.org /capabilities/cords/reentry-overview.html (747 words)

	Pravda.RU:Spacecraft reentry record: only one person struck by debris
		Although many people believe that satellites burn up during atmospheric reentry, some satellite components can and do survive the reentry heating (of course, satellites like the space shuttle orbiter survive reentry entirely because they are protected by specially designed heat shields).
		During reentry, the object is decelerating quickly and the loads on the structure can exceed 10 Gs (10 times the acceleration of gravity).
		Reentry risk estimates are supported by the fact that, over the last 40 years, more than 1,400 metric tons of materials are believed to have survived reentry with no reported casualties (of course, it is possible that casualties have occurred somewhere in the world, but have not been reported).
	newsfromrussia.com /main/2001/03/23/3118_.html (706 words)

	UFO Area Appendix 1: Offical UFO Investigations in France: the GEPAN/SEPRA Project (Site not responding. Last check: 2007-10-14)
		An atmosphere is said to be "superrefractive" when a horizontal light or radio ray curves downward with a radius of curvature that is less than the distance to the center of the planet.
		As is well known, atmospheric ducting is the explanation for certain optical mirages, and in particular the arctic illusion called "fata morgana" where distant ocean or surface ice, which is essentially flat, appears to the viewer in the form of vertical columns and spires, or "castles in the air."
		Atmospheric turbulence would distort the duct and could cause sudden changes in angle of perhaps a few tenths of a degree, which would be interpreted as a sudden change in altitude of the order of half a kilometer.
	www.ufoarea.com /events_france_gepan_sepra.html (5559 words)

	DASH 2002
		Attached to this was a reentry capsule, 0.4m in diameter and 0.2m high, with a mass of 16 kg.
		The main objective of the mission was to demonstrate high-velocity atmospheric earth reentry at the velocity over 10 km/s and to conduct "high-velocity reentry measurements" by onboard instruments during the flight.
		The orbiter in GTO was to adjust the orbital period by the drift motor (DFM) for the reentry to the planned point in the Sahara desert in Mauritania Three days after the launch, the capsule was to have separated from the orbiter and conduct reentry over the Sahara desert in Mauritania.
	www.astronautix.com /craft/dash2002.htm (1187 words)

	Ballistic Missile Basics
		A pure ballistic trajectory limits the effectiveness of a chemical or biological attack because, generally, the reentry speed is so high that it is difficult to distribute the agent in a diffuse cloud or with sufficient precision to ensure a release under the shear layer of the atmosphere.
		The heat generated during reentry is not only dependent on atmospheric density, but is also inversely proportional to the square root of the radius of the RV's nose cone and proportional to the cube of its velocity.
		During reentry, the ablative processes begin in the upper atmosphere when the pyrolysis temperature of the material is reached resulting from an increase in atmospheric friction.
	www.fas.org /nuke/intro/missile/basics.htm (5746 words)

	13. ATMOSPHERIC FLIGHT
		Without an atmosphere, as in the case of a landing on the Moon, one is forced to the weight-consuming expedient of rocket braking.
		A body approaching a planetary atmosphere possesses a large amount of energy; and one of the most important of the problems of atmospheric penetration is the dissipation of this energy in a manner that will not prove disastrous to the vehicle, either during penetration or on landing.
		The approximate density variation in the Earth's atmosphere and the estimated density variation in the atmospheres of Venus and Mars are shown in figure 7.
	www.hq.nasa.gov /office/pao/History/conghand/atmosphe.htm (3828 words)

	"Physical Evidence Related to UFO Reports" page 5 (Site not responding. Last check: 2007-10-14)
		An atmosphere is said to be "superrefractive" when a horizontal light or radio ray curves downward with a radius of curvature that is less than the distance to the center of the planet.
		As is well known, atmospheric ducting is the explanation for certain optical mirages, and in particular the arctic illusion called "fata morgana" where distant ocean or surface ice, which is essentially flat, appears to the viewer in the form of vertical columns and spires, or "castles in the air."
		Atmospheric turbulence would distort the duct and could cause sudden changes in angle of perhaps a few tenths of a degree, which would be interpreted as a sudden change in altitude of the order of half a kilometer.
	www.scientificexploration.org /jse/articles/ufo_reports/sturrock/5.html (5616 words)

	Spacecraft
		It finally re-entered the atmosphere on 23 March 2001, near the Fiji islands in the Pacific Ocean.
		Atmospheric friction converts this energy into heat, enough heat than to melt or even evaporate the re-entering material, even if it is a tough metal.
		For this reason the space shuttle starts re-entering the atmosphere bottom-first, and only after almost all its velocity is lost does it turn around to the nose-first attitude of an airplane.
	www-istp.gsfc.nasa.gov /stargaze/Spaccrft.htm (988 words)

	Pioneer 13 Quicklook
		Released from the carrier vehicle in mid-November 1978, the probes entered the atmosphere at 41,600 km/hr and carried a variety of experiments to measure chemical composition, pressure, density, and temperature of the mid-to-lower atmosphere.
		The carrier vehicle, not designed for atmospheric reentry, followed the probes into the Venusian environment and relayed data about the characteristics of the extreme outer atmosphere until it was destroyed by atmospheric heating.
		Prior to atmospheric entry, each probe deployed a yo-yo despin device to reduce its spin rate from 48 to 15 rpm.
	leonardo.jpl.nasa.gov /msl/QuickLooks/pioneer13QL.html (533 words)

	NSS 1740.14 - August, 1995
		NASA programs and projects that use atmospheric reentry as a means to remove space structures from orbit at the end of mission life will limit the amount of debris that can survive uncontrolled reentry.
		For a piece of debris that survives atmospheric reentry, the debris casualty area is the debris cross-sectional area plus a factor for the cross-section of a standing individual.
		The total debris casualty area for a reentry event is the sum of the debris casualty areas for all debris pieces surviving atmospheric reentry.
	www.orbitaldebris.jsc.nasa.gov /library/NSS1740_14/nss1740_14-1995.html (13345 words)

	Atmospheric Reentry Encyclopedia Article @ LaunchBase.com (Launch Base) (Site not responding. Last check: 2007-10-14)
		And more importantly, NASA thinks it can use them for the atmospheric reentry of spacecraft.
		Chapter 10, titled "Moment Equations in Constant Density Atmosphere" concerned the subjects of entry vehicle roll resonance and tricyclic theory.
		Despite the omissions from the earlier version, "Dynamics of Atmospheric Re-Entry" is a very useful book and still in print, though very expensive (current list price of $105.95).
	www.launchbase.com /encyclopedia/Atmospheric_reentry (8036 words)

	Space Weather: Atmospheric Drag
		If magnetic activity is also triggered at Earth, intense currents flowing through the upper atmosphere, and energy deposited by high speed particles at high latitudes dramatically increases the heating and expansion of the atmosphere in these regions.
		With all of the uncertainties in the prediction of atmospheric density along the satellites orbital path, even our most sophisticated programs are unable to determine the time of a satellite's reentry to better than 10% accuracy or within 2.4 hours in a 24 hour period.
		The reentry location is rarely a problem because most of the satellite is totally vaporized during the decent.
	www.windows.ucar.edu /spaceweather/sat_drag.html (481 words)

	Reentry Vehicle Technology
		Clearly the problem of reentry to Earth's atmosphere was a significant challenge for the early spaceflight researchers, as they considered how best to overcome the heat generated by friction as a spacecraft slowed in the atmosphere.
		GE decided to use the heat-sink concept, whereby the heat of reentry was conducted from the surface of the vehicle to a mass of material that could soak it up quickly.
		It spent a lot of time in the upper atmosphere, trailing a stream of ionized gas that showed up dramatically on radar, which was not good for a warhead.
	www.centennialofflight.gov /essay/Evolution_of_Technology/reentry/Tech19.htm (1642 words)

	Reentry Series (Site not responding. Last check: 2007-10-14)
		The Reentry Series is one of several proposed series of dynamic environmental works which involve the synthesis and aestheticised use of otherwise naturally occurring, very large scale, time dependent visual phenomena.
		Capable of launching 10 reentry vehicles, each weighing 400 to 800 pounds, the final stage consists of the so-called "bus", a guidance platform capable of the precise individual release of each of the 10 reentry vehicles (originally nuclear warheads).
		Their reentry creates an atmospheric shock wave that produces a luminous plasma field which is nominally 50 meters in diameter.
	billdolson.com /reentryseries/ttproject.htm (1616 words)

	Columbia Lost (Site not responding. Last check: 2007-10-14)
		The analysis was led by a flight director on duty the morning of Columbia's reentry as planned.
		Investigators since have determined that hot gasses penetrated the wing during atmospheric reentry, triggering the destruction of the ship.
		Among the possibilities examined for the April analysis were reducing the shuttle's mass or chilling its left wing before reentry.
	www.floridatoday.com /columbia/columbiastory2A51316A.htm (501 words)

	Micro- What it is?
		atmospheric reentry, landing on a parachute: atmospheric drag decelerates the vehicle
		The difference is that gravity acts directly on a person and other masses, just like on the vehicle, while forces like atmospheric drag and thrust first act on the vehicle, and through the vehicle on the person.
		In the first case the person and the vehicle floor are not pushed toward each other, while in the other cases they are.
	wings.buffalo.edu /sa/aiaa/index_files/Page622.htm (239 words)

	SPACE.com -- Burning Questions About Spacecraft, Black Box May Give Answers
		"Reentries are beginning to be a fact of life to those of us in the space business," he said.
		Reactions of materials during hardware reentry is one area of important research, said Nicholas Johnson, NASA's Chief Scientist and Program Manager for Orbital Debris at the Johnson Space Center in Houston, Texas.
		Even high melting-point materials can demise during reentry if they are small enough or thin enough, so strict prohibitions on their use are not necessary.
	www.space.com /missionlaunches/reentry_blackbox_020610.html (1407 words)

	[No title] (Site not responding. Last check: 2007-10-14)
		This research paper proposes to quantify the guidance feasibility for a "dynamic" reentry path in the earth atmosphere.
		However, for other kinds of trajectories (especially skip reentry) there are questions about their intrinsic possibilities of guidance namely with respect to the range control accuracy.
		A comparison between the various dynamical reentry trajectories is carried out, for which changes in flight conditions are fast and re-bouncing may occur (non-equilibrium conditions), including the classical trajectories, where changes in flight conditions are slow and regular (Shuttle-like, quasi-equilibrium conditions).
	www.mrc.uidaho.edu /entryws/abs/abs_Rodrigues.html (262 words)

	Atmospheric Reentry Demonstrator - Wikipedia, the free encyclopedia
		The Advanced Reentry Demonstrator (ARD) was a suborbital reentry test flown on the third Ariane 5 flight.
		The ARD was launched on October 21, 1998, and was released shortly after separation of the launcher's cryogenic main stage (at an altitude of about 216 km) 12 minutes after lift-off from the Guiana Space Centre, Europe's spaceport in Kourou, French Guiana.
		During reentry the heat shield temperature reached 900°C and the cone and heatshield thermal protection was in a perfect state after retrieval.
	en.wikipedia.org /wiki/Atmospheric_Reentry_Demonstrator (325 words)

	Hyperseed MAC: SRC Entry Observing Campaign, information on thermal protection systems
		Reentry = process of re-entering the atmosphere of an artificial satellite or crew vehicle.
		Purpose of reentry = enter atmosphere at shallow angle so that energy of speed is converted to energy of heat in a controlled manner (skin does not get too hot).
		However, it is impossible to reproduce both the heat flux to the surface from radiation generated just behind the shock and from convective flow at the same time.
	reentry.arc.nasa.gov /science.html (897 words)

	Chemical Rocket Launcher
		This means that it must have liquid propellant engine with either regenerative cooling (plumbing circulating cold propellant), or radiative cooling, it must withstand high stress during atmospheric reentry, and it cannot use expensive, ablative shield protecting it from the heat during reentry.
		The slow reentry is also better for the environment than the conventional, hot reentry which generates ozone destroying nitrogen oxides in the upper atmosphere.
		During the reentry the engines are on the hot, fore side of the engine cluster.
	www.islandone.org /LEOBiblio/SPBI101.HTM (4559 words)

	Inflatable Emergency Atmospheric-Entry Vehicles
		Such a vehicle would act as an atmospheric decelerator at supersonic speed in the upper atmosphere,and a smaller, central astronaut pod could then separate at lower altitudes and parachute separately to Earth.
		As low as this pressure is, it is at least ten times the expected dynamic pressure on the vehicle during the heating portion of very high atmospheric reentry, and hence it is sufficient to enable the ballute to retain its shape.
		From thermal reentry heating analyses performed at JPL, the diameter of the inflated ballute would be made large enough (30 to 40 m) to limit the maximum temperature to about 500 °C — safely below the 600 °C limit for PBO, or equivalent.
	www.nasatech.com /Briefs/Aug04/NPO40156.html (523 words)

	DASH - Summary
		The DASH (Demonstrator of Atmospheric Reentry System with Hyper Velocity) mission is a collaborative mission between ISAS and NASDA.
		In order to reduce the reentry point dispersion, the attitude of the orbiter is maneuvered by the cold-gas jets based on the earth-horizon sensor and the sun sensor.
		The geometry of the reentry capsule is designed to have natural aerodynamic stability as well as to perform a ballistic reentry flight.
	www.spaceandtech.com /spacedata/logs/2002/2002-003_dash_sumpub.shtml (354 words)

	Ariane 5
		During reentry the heatshield temperature reached 900?C and the cone and heatshield thermal protection was in a perfect state after retrieval.
		The Atmospheric Reentry Demonstrator capsule (ARD) was released by the Ariane 503 launcher as planned, shortly after separation of the launcher's cryogenic main stage, at 16h49min21sec (UT) at an altitude of about 216 km, 12 minutes after lift-off which occurred at 16h37min21sec (UT).
		At H0 +12 mn, at an altitude of 209 km, the Atmospheric Reentry Demonstrator was released and 3mn 14sec later the storable-propellant upper stage propelled the stage assembly and Maqsat 3, a representative mockup of a commercial satellite, towards its injection point.
	www.xs4all.nl /~carlkop/ariavijf.html (1324 words)

	[No title] (Site not responding. Last check: 2007-10-14)
		After the reentry burn when you arrive and altitude of 120km go to an AOA of 40, this doesn't change your reentry angle (1°) until atmospheric drag occur.
		During reentry you can calculate the rate of descent you need to be on the right glidepath with vv=sv/sh*vh, where vv is your rate of descent, sv the altitude (Surface MFD), sh the lateral distance to the base (Map MFD) and vh is your horizontal velocity (Surface MFD).
		The more steep the reentry angle, the more chances to reach lower and more dense atmosphere at high speed (basically smashing against atmosphere), which means you get burned, so you better make the entry angle less steep.
	orbit.m6.net /v2/read.asp?id=24465 (4097 words)

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