l5_space_environ_done2

l5_space_environ_done2 - THE ENVIRONMENT OF SPACE Image...

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THE ENVIRONMENT OF SPACE Col. John Keesee 1 Image courtesy of NASA.
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OUTLINE • Overview of effects • Solar Cycle • Gravity • Neutral Atmosphere • Ionosphere • GeoMagnetic Field •P l a s m a • Radiation 2
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OVERVIEW OF THE EFFECTS OF THE SPACE ENVIRONMENT • Outgassing in near vacuum • Atmospheric drag • Chemical reactions • Plasma-induced charging • Radiation damage of microcircuits, solar arrays, and sensors • Single event upsets in digital devices • Hyper-velocity impacts 3
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4 • Solar Cycle affects all space environments. • Solar intensity is highly variable • Variability caused by distortions in magnetic field caused by differential rotation • Indicators are sunspots and flares Solar Cycle
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LONG TERM SOLAR CYCLE INDICES 5 • Sunspot number R 10 (solar min) d R d 150 (solar max) • Solar flux F 10.7 Radio emission line of Fe (2800 MHz) Related to variation in EUV Measures effect of sun on our atmosphere Measured in solar flux units (10 -22 w/m 2 ) 50 (solar min) d F 10.7 d 240 (solar max)
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SHORT TERM SOLAR CYCLE INDEX • Geomagnetic Index A p – Daily average of maximum variation in the earth’s surface magnetic field at mid lattitude (units of 2 u 10 -9 T) A p = 0 quiet A p = 15 to 30 active A p > 50 major solar storm 6
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GRAVITY force At surface of earth " !0 G m 1 m 2 r 2 (" r G ! 6.672 u 10 0 11 m 3 kg 0 1 2 2 E e 2 E e g sec m 9.8 R Gm g R Gm m f | ! 0 ! 7
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MICROGRAVITY 8 • Satellites in orbit are in free fall - accelerating radially toward earth at the rate of free fall. • Deviations from zero-g – Atmospheric drag – Gravity gradient – Spacecraft rotation (rotation about Y axis) – Coriolis forces 2 2 5 . 0 Z U a m A C x D ¸ ¸ ¸ ¸ ¸ ¹ · ¨ ¨ ¨ ¨ ¨ © § ! & & 2 2 2 2zw z yw x xw x ! 0 ! 0 ! & & & & & & 2 2 z z x x ! ! & & & & x z z o y z x & & & & & & & 0 ! ! ! 2
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ATMOSPHERIC MODEL NEUTRAL ATMOSPHERE 9 • Turbo sphere (0 ~ 120Km) is well mixed (78% N 2 , 21% O 2 ) – Troposphere (0 ~ 10Km) warmed by earth as heated by sun – Stratosphere (10 ~ 50 Km) heated from above by absorption of UV by 0 3 – Mesosphere (50 ~ 90Km) heated by radiation from stratosphere, cooled by radiation into space – Thermosphere (90 ~ 600Km) very sensitive to solar cycle, heated by absorption of EUV. • Neutral atmosphere varies with season and time of day
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10 Layers of the Earth’s Atmosphere TEMPERATURE MAGNETOSPHERE Pressure Molecular mean free path EXOSPHERE Sunlit Spray region Warm region Maximum height for balloons THERMOSPHERE Aurora Aurora Airglow MESOSPHERE IONOSPHERE Noctilucent cloud D E F 1 F 2 Ozone region Sound waves reflected here Mother-of-pearl clouds Cirrus clouds Altocumulus clouds cumulus clouds Stratus clouds Tropopause STRATOSPHERE Mount Blanc Ben Nevis Temperature curve -100 0 C -50 0 C 0 0 C 50 0 C 100 0 C 1,000 mb 10 -8 mb 10 -6 cm 10 -4 cm 1 cm 1 km 100 km 100 mb 1 mb 10 -2 mb 10 -4 mb 10 -6 mb 10 -10 mb Miles 10,000 5,000 5,000 2,000 2,000 1,000 1,000 500 500 200 200 100 100 50 50 20 20 10 50,000 30,000 20,000 10,000 5 ,000 10 5 2 1 Kilometers Feet Mount Everest TROPOSPHERE
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DENSITY ALTITUDE MODEL Assume perfect gas and constant temperature n is number density (number/m 3 ) dpA - n m g A d h = o k is Boltzmann’s constant M is average molecular mass H ~ 8.4km h ~ 120km n = n o exp (-h/H) H {
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This note was uploaded on 11/08/2011 for the course AERO 16.851 taught by Professor Ldavidmiller during the Fall '03 term at MIT.