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Chapter 7

Neutral

Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

SPACE ENVIRONMENT AND ITS EFFECTS ON SPACE SYSTEMS

Chapter 7

Neutral Environment

by

V. L. Pisacane

Chapter 7

Neutral

Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

7 – 2

TOPICS

Introduction

Earth Atmosphere

Atmospheric Models

Planetary Atmospheres

Propagation

Atomic Oxygen

Aerodynamic Forces

Effusion

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Environment

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INTRODUCTION 1/2

An atmosphere is the layer of gas that surrounds a celestial body

The planets were formed with atmospheres primarily of hydrogen and helium

On the terrestrial planets (Mercury, Venus, Earth, and Mars) the thermal velocities of the atmosphere due to the solar wind was greater than the escape velocity of the gravitational field so the lighter constituents were loss

Mercury has essentially no atmosphere while the other terrestrial planets have retained the heavier molecular constituents such as carbon dioxide, nitrogen, oxygen, ozone, and argon

The outer or gaseous planets (Jupiter, Saturn, Uranus, and Neptune) being farther from the Sun and more massive were able to retain much of their the lighter molecular constituents such as hydrogen and helium

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

INTRODUCTION 2/2

Over time, the atmospheres of the terrestrial planets evolved, primarily by release of trapped volatiles by outgassing through bombardment of the surface by particulates and volcanic actions

As the distance from the center of a planet increases, the atmospheric pressure and density decrease approaching the interplanetary environment without a sharp discontinuity

In the case of the Earth, 50% of the mass of the atmosphere is below 5 km altitude and 75% is below 11 km

Planetary atmospheres absorb energy from the Sun, redistribute atmospheric constituents, and together with any electrical and magnetic forces present produce the planet’s climate

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Chapter 7

Neutral

Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

EARTH ATMOSPHERE Lower Atmosphere 1/2

Earth atmosphere divided into 5 distinct layers

Troposphere – Extend 9 km at poles to 17 km at equator – Heated by Earth so temperature decreases – Temperature decrease ~6.5 K/km – Contains 90% of the total atmosphere mass – Upper boundary is tropopause

Stratosphere – Extends from tropopause to ~ 50 km – Temp increases by UV absorption in Ozone layer – 99% of total mass in Stratosphere and

Troposphere – Upper boundary is stratopause

Mesosphere – Extends from stratopause to 80-85 km – Temperature decreases with altitude – Most meteoroids burn up in Mesosphere – Constituents in an excited state from solar

radiation causing ionosphere – Upper boundary is mesopause

7 – 5

http://en.wikipedia.org/wiki/Atmosphere_of_Earth

Chapter 7

Neutral

Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

EARTH ATMOSPHERE Lower Atmosphere 2/2

Thermosphere

– Extends from mesopause to 200-300 km – Temperature increases to 1800 K – Small change in solar activity can cause large

change in temperature – Upper boundary is thermopause or exobase

Exosphere – Extends from thermopause/exobase upwards – Sometimes considered outer layer of

thermosphere – Temperature is essentially constant – Density so low particles travel ballistic paths

and may escape

7 – 6

http://en.wikipedia.org/wiki/Atmosphere_of_Earth

Chapter 7

Neutral

Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

EARTH ATMOSPHERE Upper Atmosphere

Thermosphere extends from 80-85 km to altitude where temperature is constant typically 200-500 km

Exosphere extends from thermopause to outer space

In lower thermosphere temperatures rise rapidly with altitude

Above 200 300 km temperature remains relatively constant

Temperature varies significantly between day and night and between the minimum and maximum solar activity

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http://www.windows2universe.org/earth/Atmosphere/thermosphere_temperature.html&edu=high

Thermopause

Thermopause

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Space Environment and its Effects on Space Systems ©VLPisacane,2012

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EARTH ATMOSPHERE Homosphere and Heterosphere

It is possible to stratified the atmosphere by composition into two regions: the homosphere and the heterosphere separated by the turbopause or homopause

Turbopause/homeopause ~80-100 km

Homosphere is the well-mixed region of the atmosphere lying below the turbopause that has constant constituents

Heterosphere is the region above the homopause or turbopause with significantly variation in composition as a function of altitude

Hydrogen and helium, being lighter, are found in the upper heterosphere while nitrogen and oxygen, being heavier are found in the lower heterosphere

Figure 7.6 Vertical structure of the atmosphere Source unknown

Chapter 7

Neutral

Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

7 – 9

EARTH ATMOSPHERE Composition Homosphere

Lower atmosphere (< 80 km) constituents are constant due to turbulent mixing

Region from 0-~80 km is known as the homosphere

Gas Volume Molecular Mass Nitrogen (N2) 780,840 ppmv (78.084%) 0.78084x2x14.007 = 21.8745

Oxygen (O2) 209,460 ppmv (20.946%) 0.20946x2x15.999 = 6.7023

Argon (Ar) 9,340 ppmv (0.9340%) 0.009340x39.948 = 0.3734

Carbon dioxide (CO2) 390 ppmv (0.039%) Total = 28.9502 ≈ 29 kg kmol-1

Neon (Ne) 18.18 ppmv (0.001818%)

Helium (He) 5.24 ppmv (0.000524%)

Methane (CH4) 1.79 ppmv (0.000179%)

Krypton (Kr) 1.14 ppmv (0.000114%)

Hydrogen (H2) 0.55 ppmv (0.000055%)

Nitrous oxide (N2O) 0.3 ppmv (0.00003%)

Carbon monoxide (CO) 0.1 ppmv (0.00001%)

Xenon (Xe) 0.09 ppmv (9×10−6%) (0.000009%)

Ozone (O3) 0.0 to 0.07 ppmv (0 to 7×10−6%)

Nitrogen dioxide (NO2) 0.02 ppmv (2×10−6%) (0.000002%)

Iodine (I2) 0.01 ppmv (1×10−6%) (0.000001%)

Ammonia (NH3) Trace

Not included in above dry atmosphere:

Water vapor (H2O) ~0.40% over full atmosphere, typically 1%-4% at surface

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

7 – 10

EARTH ATMOSPHERE Composition of Heterosphere

r

Turbopause

Source unknown

Note: Different

scale length for

each species

Maximum solar

activity

Minimum solar

activity

From Pisacane Ed Fundamental of space systems, Oxford Press, 2005

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

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EARTH ATMOSPHERE Pressure and Density Equations

Assume hydrostatic equilibrium

From the perfect gas law Integration with H defined as the scale height

Density follows as

where T = temperature constant with height h, K

g = acceleration of gravity assumed constant, m s-2

M = molecular mass, kg-kmol-1

` p = pressure at height h po = pressure at height ho

R = universal gas constant, J kmol-1 kg-1 r = density at height h ro = density at height h0

H ≡ RT/Mg, scale height h = height

0)Adh(gpAAdhdh

dpp r

dhgdp r

M

RTp r dh

RT

Mgpdp

H

hhexpphh

RT

Mgexppp 0

000 Mg

RTH

r

r

H

hhexphh

RT

Mgexp

RT

Mp

RT

pM 000

0

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

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EARTH ATMOSPHERE Earth Scale Height

Problem: Determine the scale height of the Earth’s atmosphere

Solution: Scale height is given by Eq. 7.47 as

where at the surface of the Earth M = 29 kg kmol-1 T = 273.15 K (0oC) g = 9.8 0665 m s-2

R = 8314.472 J kmol-1 K-1

Consequently

Since temperature decreases fater than the decrease in g in the stratosphere the scale height decreases from the value at the Earth’s surface

Mg

RTH

km0.8 80665.929

15.273472.8314H

Source unknown

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

7 – 13

EARTH ATMOSPHERE Pressure and Density with Lapse Rate

If the temperature as a function of altitude is approximated by

the pressure and density is given by

where L = lapse rate, K m-1

T0 = temperature at height h0, K T = temperature at height h, K g = acceleration of gravity, m s-2

M = molecular mass, kg-kmol-1

` p = pressure at height h po = pressure at height ho R = universal gas constant, J kmol-1 kg-1 r = density at height h ro = density at height h0 H ≡ RT/Mg, scale height

00 hhLTT

0L

H/h

0

RL

Mg

0

0

0 ephhT

L1pp

0L

H/h

0

1RL

Mg

0

0

0 ehhT

L1

r

rr

Chapter 7

Neutral

Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

EARTH ATMOSPHERE Lapse Rate

Several lapse Rates are employed

Dry Adiabatic Lapse rate (DALR) 10 K km-1

– Adiabatic process ─ no transfer of heat or mass across the boundaries

– Temperature changes within air parcel only caused by increases or decreases of internal molecular activity

– Dry air parcel rising cools at rate of 10 k km-1 – Dry air parcel sinking cools at rate of 10 k km-1

Saturated Adiabatic Lapse Rate (SALR) 5.5 K km-1 – Rising air parcel containing water vapor will cool at dry

adiabatic lapse rate until it reaches condensation temperature, or dew point

– Condensation releases latent heat in parcel and thus cooling rate of the parcel reduces

– SALR depends on temperature and pressure but in middle troposphere is between 5 and 6 K km-1

Environmental Adiabatic Lapse Rate (EALR) 6.5 K km-1 – Actual lapse rate is function of actual temperature – Standard model temperature gives ~ 6.5 K km-1

7 – 14

http://www.ux1.eiu.edu/~cfjps/1400/atmos_struct.html

Chapter 7

Neutral

Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

ATMOSPHERIC MODELS Selected Available Models

US Standard Atmosphere

Harris–Priester Model

Jacchia Reference Atmosphere 1977

Atmospheric Handbook

COSPAR international Reference Atmosphere (CIRA) Model

Mass-Spectrometer-Incoherent-Scatter (MSIS)-90 Model

NRL Mass-Spectrometer-Incoherent-Scatter Empirical (MSISE)-00 Model

Just a few of the models that are available

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Chapter 7

Neutral

Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

ATMOSPHERIC MODELS Model Input Parameters

7 – 16

Source unknown

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

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ATMOSPHERIC MODELS U. S. Standard Atmosphere

The standard atmosphere gives the average pressure, temperature, and air density as a function of altitudes

It is a piece-wise continuous with 7 regions – Sea level pressure = 101,325 N/m2 (1 bar = 100,000 N/m2) – Sea level temperature = 288.15 K – Sea level density =1.225 kg/m3

– M = molecular mass of air = 28.9644 kg kmol-1

– Geometric height, z, actual physical height above mean sea level – Geopotential height, h, where g0h = ∫gdz = potential energy, g0=9.8 m s-2 in MKS

Chapter 7

Neutral

Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

ATMOSPHERIC MODELS Jacchia Reference Atmosphere Model

Jacchia Reference Atmospheres were published in 1970, 1971, and 1977

Density, temperature, and composition are given for altitudes 90 ─ 2500 km

Effects include – season – latitude – local time (diurnal bulge) – solar activity – geomagnetic activity – atmospheric rotation – atmospheric tides – Earth oblateness on altitude – semi-annual and seasonal-latitudinal effects

Model are based mostly on satellite drag data

Assuming diffusive equilibrium, the atmospheric profiles are defined by the exospheric temperature

Outputs – Temperature, – Mean molecular mass – Density – Number densities of the major gas constituents (N2, O, O2, Ar, He, and H)

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Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

ATMOSPHERIC MODELS COSPAR international Reference Atmosphere CIRA-86 Model

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Source unknown

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

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ATMOSPHERIC MODELS NRL-MSISE Reference Atmosphere

Mass-Spectrometer-Incoherent-Scatter models: – MSIS-86 – MSISE-90 – NRLMSISE-00

NRLMSISE-00 represents improvements over the earlier MSISE-90 model by including additional drag and accelerometer data from spacecraft

Inputs and outputs of the NRLMSISE-00 model are given

INPUTS OUTPUTS

Year, day, UT sec He number density

Altitude O number density

Geodetic latitude O2 number density

Geodetic longitude N number density

Local apparent solar time N2 number density

F10.7 81 day average Ar number density

F10.7 prior day daily value H number density

AP magnetic index day Anomalous oxygen

number density

AP magnetic index 3 h before current time

Total mass density

AP magnetic index 6 h before current time

Exospheric temperature

AP magnetic index 9 h before current time

Temperature at altitude

AP magnetic index average of eight 3 hours indices from 12 to 33 h before current time

AP magnetic index average of eight 3 hours indices from 36 to 57 h before current time

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

ATMOSPHERIC MODELS NRL-MSISE Sample Result ─ Lower Atmosphere

Day = 172 UT(Sec) = 29000 Geodetic Latitude(Deg) = 60 Geodetic Longitude(Deg) = 120 Local Apparent Solar Time(Hrs) = 16 81 day Average of F10.7 Flux = 150 Daily F10.7 Flux for Previous Day = 150 AP=Magnetic Index (Daily) = 4

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Source unknown

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

ATMOSPHERIC MODELS MSIS-90e Density Distribution

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Source unknown

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

ATMOSPHERIC MODELS NRLMSISE-00 Model Example 1

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Model – NRLMSISE-00 – F10,7 prev day 70.0 10-22 W m-2 Hz-1 – F10.7 81 day average 60.0 10-22 W m-2 Hz-1

– Daily Ap 15.0

Conditions – Sun at equator – Sun in orbital plane

Orbit – Altitude: 1000 km circular – Inclination: polar – Epoch: 0h UT 21 Mar 2014 (Vernal Equinox) – Period: 1.75 h r – Rev per day: 13.72

Average Density (cm-3) 2.8822E+05

Average Front Flux (cm-2 s-1) 2.1229E+11

Average Back Flux (cm-2 s-1) 1.5933E+04

Front Fluence (cm-2) 6.6948E+18

Back Fluence (cm-2) 5.0246E+11

1 revolution

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

ATMOSPHERIC MODELS NRLMSISE-00 Model Example 2

7 – 24

Model – NRLMSISE-00 – F10,7 prev day 70.0 10-22 W m-2 Hz-1 – F10.7 81 day average 60.0 10-22 W m-2 Hz-1

– Daily Ap 15.0

Conditions – Sun at Tropic of Cancer, 23.44 deg North – Sun orthogonal to orbital plan

Orbit – Altitude: 1000 km circular – Inclination: polar – Epoch: 0h UT 21 June 2014 – Period: 1.75 h r – Rev per day 13.72

Average Density (cm-3) 2.6291E+05

Average Front Flux (cm-2 s-1) 1.9362E+11

Average Back Flux (cm-2 s-1) 1.9209E+04

Front Fluence (cm-2) 6.1061E+18

Back Fluence (cm-2) 6.0576E+11

Chapter 7

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Environment

Space Environment and its Effects on Space Systems ©VLPisacane,2012

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PLANETARY ATMOSPHERES Planetary Scale Heights

* Surface defined by pressure of 1 bar = 100 kPa where 1.01325 bar = 1 atm pressure

Recall

rr

H

hhexp 0

0

Chapter 7

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Space Environment and its Effects on Space Systems ©VLPisacane,2012

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PLANETARY ATMOSPHERES Planetary Compositions

1 bar = 100 kPa where 1.01325 bar = 1 atm pressure

Planet Surface Pressure (bars) Surface temperature (K) Major Constituents

Mercury 10-15 440

42% Oxygen 29% Sodium 22% Hydrogen 6% Helium 0,5% Potassium < 1% Trace elements

Venus 92 737 96.5% Carbon Dioxide 3.5% Nitrogen Trace elements

Earth 1 288

78.08% Nitrogen 20.95% Oxygen 0.9% Argon Trace elements

Mars .01 210

95% Carbon Dioxide 3% Nitrogen 1 % Argon 1 % Oxygen <1% Trace elements

Jupiter Unknown 165 @ 1 bar 89.8% Hydrogen 10.2% Helium Trace elements

Saturn Unknown 134 @ 1 bar 96.3% Hydrogen 3.25% Helium Trace elements

Uranus Unknown 76 @ 1 bar

82.5% Hydrogen 15.2% Helium 2.3% Methane Trace elements

Neptune Unknown 72 @t 1 bar

80.9% Hydrogen 19.0% Helium 1.5% Methane Trace elements

Source: http://nssdc.gsfc.nasa.gov/planetary/factsheet/