space environment & it's effects on space systems course sampler
DESCRIPTION
This class on the space environment and its effects on space systems is for technical and management personnel who wish to gain an understanding of the important issues that must be addressed in the development of space instrumentation, subsystems, and systems. The goal is to assist students to achieve their professional potential by endowing them with an understanding of the fundamentals of the space environment and its effects. The class is designed for participants who expect to either, plan, design, build, integrate, test, launch, operate or manage payloads, subsystems, launch vehicles, spacecraft, or ground systems.Each participant will receive a copy of the reference textbook: Pisacane, VL. The Space Environment and its Effects on Space Systems. AIAA Education Series, 2008.TRANSCRIPT
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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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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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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
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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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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
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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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Space Environment and its Effects on Space Systems ©VLPisacane,2012
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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
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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
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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
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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
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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
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Space Environment and its Effects on Space Systems ©VLPisacane,2012
ATMOSPHERIC MODELS Model Input Parameters
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Source unknown
Chapter 7
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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
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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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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
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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
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Space Environment and its Effects on Space Systems ©VLPisacane,2012
ATMOSPHERIC MODELS MSIS-90e Density Distribution
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Source unknown
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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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Space Environment and its Effects on Space Systems ©VLPisacane,2012
ATMOSPHERIC MODELS NRLMSISE-00 Model Example 2
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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 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
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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
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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/