The orbital environment is complex, dynamic, and comprised of both natural and system-induced components. Several environment factors are important for materials. Materials selection/suitability determination requires consideration of each and all factors, including synergisms among them. Understanding and evaluating these effects will require ground testing, modeling, and focused flight experimentation

Purvis, C. K.

English

NASA Technical Reports Server

OVERVIEWOF NVIRONMENTALFACTORS* N 8 9 " 23 5 2 9
C. K. Purvis
NASA Lewis Research Center
Cleveland, Ohio
Original figures not available at time of publication.
PRECEDING PAGE BLANK NOT FILMED
https://ntrs.nasa.gov/search.jsp?R=19890014158 2020-03-20T03:14:55+00:00Z
THE ENVIRONMENT
Near-Earth space is a complex, dynamic environment. The energies,
densities, and constituents of the natural orbital environment vary with position
(attitude, latitude, longitude), local time, season, and solar activity. The
presence and activities of space systems modify many of the natural environment
constituents (such as neutral particles and plasmas) so that the local environment
may be quite different from the natural one. The local environment will interact
with the system, its subsystems, surfaces, and structures. The impact of these
interactions on the system must be assessed to ensure successful operation.
Effects of the environment on the surface and structural materials play a crucial
role in determining system function, reliability, and lifetime.
NEAR EARTH SPACE IS NOT EMPTY
M,3cjnet o0 ause
So_a,w,_a __:_:'_ '
THE EARTH'S MAGNETOSPHERE
IT CONTAINS
0 NEUTRAL ATOMS
0 _Lf_SMAS
0 FI+!L_[)S
0 RAI)IAT ION
0 PAK [ICULATES
VARIES WITH
0 LO(AL TIME (DAY/NIGHT)
0 bOLAR CYCLE
SYSTEM -_-N _'-PkI: L r_ AND OPERATIONS ALTER
LOCAL ENVIRONMENT
SYSTEP_ENVI _<ONMENT INTERACTIONS
0 !NCI{EASE WITH SYSTEM SIZE, POWER
AND ACTIVITY
0 IMPACT SYSTEM/SUBSYSTEM
- FUNCTIONAL
- OPFRATIONS
- i{ELIAB[LITY
- _ IFETIME
I
THETERRESTRIALSPACEENVIRONMENT
The terrestrial space environment comprises manyfactors, each of which can
have important effects on space systems. These effects must be accounted for to
ensure successful designs. This chart summarizesthe natural environment factors
(debris is included, though not truly a "natural" factor, because it is important
and not generated by the system being considered) and their effects, and notes
the importance of system-generated components. The "enhanced" or threat
environment is noted for completeness, but it is not considered further here.
Manyof the effects listed are materials related. It is the environment factors
associated with these effects on which we nowfocus. These are solar radiation,
meteoroids and debris, neutral atmosphere, plasmas, trapped radiation, and
system-generated contaminants. In what follows, each of these environments is
overviewed briefly. More details will be found in the individual "environment"
sections of the Workshop's focus sessions.
ENVIRONMENTALFACTOR
GRAVITY
SUNLIGHT& ALBEDO
METEOROIDS & DEBRIS
NEUTRAL ATMOSPHERE
FIELDS
PLASMAS
FAST CHARGED PARTICLES
SYSTEM GENERATED
ENHANCED
-EFFECTS ON SPACE SYSTEMS-
EFFECTS
ACCELERATION,TORQUES
HEATING, POWER, DRAG, TORQUES, PHOTOEMISSION,
MATERIAL DAMAGE, SENSOR NOISE
MECHANICAL DAMAGE, ENHANCED PLASMA INTERACTIONS
DRAG, TORQUE, MATERIAL DEGRADATION.HEATING
TORQUES. DRAG. SURFACE CHARGES, POTENTIALS
CHARGING, INDUCED ARCING, POWER LOSSES,
POTENTIALS,ENHANCED CONTAMINATION,CHANGE OF
E-M REFRACTIVE INDEX, PLASMA WAVES & TURBULENCE
RADIATION DAMAGE, ARCING, SINGLE EVENT UPSETS,
NOISE. HAZARD TO MAN
SYSTEMDEPENDENT: NEUTRALS.PLASMAS,FIELDS
VIBRATIO_ TORQUES,RADIATION, PARTICULATES
EMP & RELATED
THESOLARSPECTRUM
This chart gives an overview of the solar spectrum, from the gammaray out
to the far infrared. Some99.5%of the Sun's radiant energy is in the 1200Ato
I0 pmwavelength (2.5 x 10-15 - 3 x 10-13 Hz) range. The flux levels in the
visible and near-ultraviolet (UV) are relatively stable, whereas those in the
extreme ultraviolet (EUV), X, and gammaray region are highly variable and
dependon solar activity.
10 6 --
A I O5 -
i 11)2 -
_J I-
#
BI,Ill2}INUN- " " CON[)ITI{
1c_-!; L.] t I I I
IU 2 1l]20 11.]19 1(]1811]1711l TM 11115 11]i'1 ltjl :] 1012
FFI EQI.JI-NCY (I.tz)
t
GAMMI\-IIAY X-ItAY I]I_TRA- INFRARED
VI(.)LET
NASA-(]C]DDARD SPACE FI_IGIIT CENTER
till 1!L--NU 1_[.T, MAIIYLANI)
A lJ(;lJSl, 197(i
8
SOLARIRRADIANCE
The solar irradiance spectrum in orbit in the UVthrough IR range is well
approximated by black body radiation for a T = 5762°-K object.
The Solar Spectr.m
0.24
0.22
0.20
0.18
E 0,16
5 0.14
uJ 0.12
Z
,_ 0.106
cc 0.08
re
0.06
0.04
0.02
__- Oul_ide Earlh'_ Atmosphere 2
/IV _\ (A ...... d ....... OlJSJWcm )
/ J _ Sea Level I(Ivery Cleat Atmosl)hete
' I H20__..,_%_--7 (A ..... d ........ 01111Wcm "2)
_._ "'.,._,_ / Black Body at T : 5762 K 2
/i _._ O2, H22 _ //(A ...... I......... 0 1353Wcm") H20I _ c°2..
,Jk°, , , , ,
0.2 0 4 0,6 08 1 0 1 2 1 4 16 1 8 2.0 2.2 2.4 2.6
WAVELENGTH (j_rn)
Normally incident sohn, radiation at sea level on very clear days, solaP speetz'al irrsdianee
outside the Earth's atmosphere at 1 AU, and blnekbody spectral irrndianee curve at T = 5762°I(
(normnlized to I AU)
9
METEOROID ENVIRONMENT
Meteoroids are an obvious potential source of mechanical damage to
spacecraft materials. Total mass influx of meLeoroids is estimated as
I0 I0 gm/year. Average velocity of meteoroids is considered in the models to be
20 km/second and density is considered to be approximaLely .5 gm/cm 3 for
cometary meteoroids and approximately 2 gm/cm 3 for asteroidal ones. The figures
show one-year average estimates of cumulative number fluxes from various sources.
In modeling this environment, N is taken to be of the form N = Const/mm where m is
a slowly varying parameter of order unity (see right-hand figure).
N
16
3 8
Z -
X
t_
>
:; -0
a
o_
_0
O
.J
-16
I I I | J I i I I ]
f
/xomn[D ml-v[ _lcrs.
• 0c0_z ) \'_ -_'J _
[] r_cx_sI, [J.01;(ZPLOR[!111._ "_,. /
O PR._IRI( A[TIOR_ Nc_O_XT [Ig6X) +"_
+ APOLLOOSJ(Cl5; _H_i1.[ fl%?) _LI_XIN$, IRONS/ _
........... ': ....... ugss_" _\
i ! t t J ! I ! i "_
-i6 -8 0 8 16 2q
LOGIo MASS, g
Tarreotr_ed Inone-J.[hi.x rnLeo Of" meteor_da, N Ja tl_e _LL_
oi' particles with mo..a ireater t_mn m J2-ZOJ.
SKYLAB
• o S14O
180741.31 "'*
LUNAR ROCKS
LUNA 1B $PH
SEC
VIDICON
LUNAR
SEISMOGRAPHS
•11 .li ,t2 ,10 .I 4 ,4 ,| 0 _| Io I m
CI_ilItLJG(IVO p_rtJdo _Uxes _rIJfll V_I,JOL_ dotl eou_ces
10
METEOROID IMPACTS
Estimates of frequency of meteoroid impacts can be made using formulas given
in NASA SP-8013 and SP-8042. These models are old but are still used for design.
NASA SP-8013 GIVES COMETARY METEOROID FLUX N AT IAU AS:
LOGIo N: -14.37 -1.213 LOGIo M i0-6_ M _I00
LOGIo N: -14.34 -1.584 LOGIoM -0.063 (LOGIoM) 2 10-12__ M_10 -6
N = # OF IMPACTS OF MASS M GP_MS AND LARGER PER SQUARE METER PER SEC.
_LTIPLY BY DEFOCUSING FACTOR G
e
EXAMPLES:
M(GM) NIAu(m-2s-l)
1 3.9x10 -15
10 -6 7.9xi0 -8
10 -12 4.0x10 -5
AND EARTH SHIELDING FACTOR S(_)
R(Re) NR(m-2s-l) NR(m-2yr-i )
i .05
1.5
6
1.05
1.5
6
i .05
1.5
6
2 IxlO -15
2 9xlO -15
2 5xlO -15
4.3xi0 -8
5.8xi0 -8
-8
5.,Ix10
-5
2.2xi0
3.0xlO -5
2 6xlO -5
6.6xl 0 -8
9.1xi0 -8
7 9x10 -8
1 4
1 8
1 6
6 9xl 02
9 4x102
8.2xi02
[SEE ALSO NASA SP-8042 "METEOROID DAMAGE ASSESSMENT", 1970]
11
DISTRIBUTION OF DEBRIS IN EARTH ORBIT
This chart shows a representation of the distribJtion of debris in Earth
orbiL. The "ring" is at geosynchronous. Sources of debris include spent stages,
nonfunctional spacecraft, fragments from staging operations, exploded stages,
collision, disposed wastes, and residues from engine burns•
]2
CLOSER VIEW OF DEBRIS DISTRIBUTION
A closer view illustrating the relative uniformity of debris distribution
in low Earth orbit (LEO}. Density of the debris falls off at altitudes >1500 kin.
,°,•
13
ORBITAL DEBRIS MEASUREMENTS COMPARED TO METEOROID FLUX
This shows a comparison of meteoroid and debris fluxes for various particle
diameters. Debris is a more serious threat than meteoroids at the small and large
extrema. Data on debris fluxes in the l-mm to l-cm diameter range is lacking.
F
L
U
X
Intpn,,¢l
per
Cron-Sectionnl
M'-VR
I0 _.
I O|-
I o •
l 0"I- -
10-4..
104. .
lO"--
o.ooo I
_-"_ _'/_ f--O RBITI_R WINDOWS
=..= SOLARMAXDATA
M ETEO RO I DS . % -G ROU N D TELESCOPIC (M IT)
\
-G ROUN D EX PLOSION DATA
\
l l I . ! ..
O.OO I 11.01 O. I I I 0 l O0
PARTICLE DIAMETER (cln)
North American Air Defense Command
14
NEUTRAL ATMOSPHERE
Atmospheric pressure and density decrease rapidly in suborbital regions
(_200 km_, while kinetic temperature increases. At orbital altitudes, the
residual atmosphere is tenuous enough to be essentially collisionless.
1000
90O
000
100
DENSITY, kg/m 3
10"14 10-13 10.1o 10 4 104 10.4 10"2 100
PRESSURE
10.8 10.8 10 .4 10.2 100 102 104 106
PRESSURE, NIm 2
Total protrude and m,ss density as s function of jeo-
metric altitude
0oo
ilOO
600
400
200
0
0
C I
COESA (1976)-C °
-.,--.-- COESA (1962)-C
C
200 400 6O0
I i
800 1000 1200 1400 1600 180Q 200(,
Kinetlo TempKeturo IK)
Kinetic temperature versus altitude
)5
STANDARD ATMOSPHERE
The density, composition, and temperature of the residual atmosphere vary
with solar activity. In recent years the reactivity of atomic oxygen, which is
the dominant constituent of the residual atmosphere at LEO, has been recognized as
a serious threat to materials exposed to its ram flow. The motion of spacecraft
through the residual atmosphere in LEO at velocities of the order 7.5 to 8 km/sec
results in an equivalent impingement energy for 0 of 4.5 to 5 eV. Rapid
degradation of some materials in this environment has been observed on STS.
100(]
8OO
E
u/
o
6OOF-
p
<
u
n_ 40O
uJ
o
LU
2OO
0
1010
\\\
\
_'\.\\
i
1
H_---- I
O--._ i
N 2 .....
02Ar................I
................- ? > \
_"_ " N... "- _ "-,_,
I , I ,_.___L L___
1012 1014 1016 101B
NUMBER DENSITYf m"3
Relative concentrations of atmospheric constituents
dm'ing peziods of, minimum solar activity
1000
, I \
\
, I \
,I \ ._ -
800 _........ \_I Ho_E \ o--.--
.X:
,. \ o22_.._
o '".... I _,, \ Ar ....
600
""'..,.1 ',\ \
,..._,
< ,.,_',,\.
u \ ""... ,\.\G 400 \
o_ \ I ".,.',,.\
,,,. \ I ..... ,<\ l
\_,_. ............_... -_
200 I- \ "'_. ".... "q- /
.._, "..-.. --- ..:.;_
o
1010 1012 10 TM 1016 10 TM
NUMBER DENSITY, m"3
Relative ooncentrations of atmosphere constituents
during periods of maximu.m solar activity
16
ENVIRONMENTAL INTERACTIONS
Near-Earth plasma regimes include the cold (~.1 eV) relatively dense (to
-106/cm _} ionospheric plasmas whose densities aradually fall off with altitude;
the hot (~KeV to ~10's of KeV), tenuous (_l/cm 3) plasmas observed at
geosynchronous and associated with geomagnetic substorm activity; and the fluxes
of hot electrons due to these geosynchronous plasma injections which travel down
magnetic field lines and precipitate in the auroral zones. The latter two plasma
environments can charge spacecraft surfaces to kilovolt potentials; the cold
ionospheric component interacts strongly with spacecraft power systems.
NEAR EARTH PLASMAS
1,,_ SYNCHRONOUS
uj- ORBIT '" !_!,'C" L
lO'bl/\ \ ', ,, _:_:!;
PLASMAIO' 1 j ,z /
NUMBER I _ \: _,_'.:',;.F, "k,T 't
ALTITUDE, km vl..
IONOSPHERIC
PLASMAS
GEOSYNCHRONOUS
MODEL SUBSTORM
AURORAL PLASMAS
HIGH LATITUDES
ORIG/NAL PAGE IS
OF POOR QUALITY
17
PLASMA DENSITY AND COMPOSITION IN THE IONOSPHERE
Plasma density and composition in the ionosphere vary daily, seasonally,
latitudinally, and with solar activity, as is illustrated in these figures.
IONOSPHERE
! J ",
O*
IN • . Q]_ ! ,
le | 10'1 IS4 le s 10II
NUV4|Alsm:
Ionia oompoilllon of ;ha sollr mlrdmwl
daytime winter Lonoephnro (1-|41.
11,20
IOI
I+oo
7m
'_ * I00
_. so+
tM
304
lao I
NQATH SO
+.VI _J'f_] - :
| tZ¿
I I I l I I I I I
,o M Zo III | I, 1411 I " 44 ,OtlTH
OlInGR+I.PHII: II_IATOII .i_ I,---MIGNITIC IQUAIQIIi I
I_ Tn'uo i Idell
n,ylleil, eqml-elmnn-denllly m,,molm.o IUNill ll4/lm |) II-311,
l'-'nJghmm" _\ 'X "
I ', \',
,-L N.N.,_O, \ •
_--[ "tam'°' _+_"(N '
"--!+/
B ................. '_° ' "
_o2 la ] to4 le*'
.... Jrlll . ...... I
1411 111J
11,1¢1"11OI4:OKII_nATIOM I_11
Normal elec|ron dlst:'ibution
18
tion
DIURNAL VARIATION IN ION
This figure illustrates the diurnal
for solar maximum at mid-latitude.
DENSITY AND COMPOSITION
variation in ion density and composi-
MID LATITUDE ION COMPOSITION
SOLAR MAXIMUM
DAYTIWI[PO$1TIY[IONCO_qPO$1TION
_00 i I 'I ,I_I 4 # I I I
_- .,\ "7_" o%,o,,,0.-
=,,,,| _ ./..i" \\
i=._o,,{ J"_--- JJ
. g,,"),,,%_.
60 . ms--l-- ! I I I
f
tIGlON
>L50 11
I r
REGION
[m-_ im
O
lEGION
I00_
"_iOC
,Id
l{X
6_
10
NIGHTTIlttPOSITIVEIONCOtttPOSITION
' '_l-ll" '1"* ' " '
It ,o,.,,.
/ I o: i f/.<//_<<I/_//_/_
h,_"i°Nsl I i i
lOl IOI 101 i0,5
IONCONCDIIIIAIIONIcm'll
F
I[GION
> J.,$Oim
l
RI'GION
:I_-i)1..$0im
REGION
JO-I_ Im
19
GEOSYNCHRONOUSPLASMA ENVIRONMENT
This figure shows histograms of the occurrence freQ.encies of the electron
and ion temperatures and current at geosynchronous orbit measured by Applications
Technology Satellite (ATS)-5 and ATS-6. T(AVG) is two-third's the ratio of
energy density to number density; T(RPIS) is one-half the ratio of particle energy
flux to number flux.
The hot plasmas were observed to charge the ATS-5 and ATS-6 spacecraft to
kilovolt potentials in eclipse and to hundreds of volts in sunlight. Similar
charging effects are anticipated for large spacecraft in auroral zones at LFO.
The DMSP spacecraft (900 km) has been observed to charge to approximately 700
volts during auroral passage. Charging potentials are negative because electron
fluxes dominate the process.
lq_ CUWI|NT /ml-ql loll _ 0_
Oll Moo• Y TI[III'_IATUll TlUlqI:II&TUlU
--AVl
'' * .Tlk4 " -- lilM.
, .I J?
. i, G / , I: '_
u _S I
"I '
14 h IL_C_m, ¢_UnT are4 an I_eo A_ee IIt.l[CTm_
=nH -- ._,-* 14 -.v. --_Yg._
_m
", I"
is ', :,.F I',I t
"
°o ., j ,_ °o . ._ ,. -o . . ,.
,1_I ml ,P_l I TIIWl l"llllaV I
HLstograms of the Occurrence Frequencies o[ the
Electron and Ion Temperatures and Current at Geosy_chronous
Orbit as Measured by ATS-.5 and ATS-6, T(AVG) is 2/3's
the r_tio of energy density to number density; "P(RMS) is
one-haLl the ratio of particle ener_), flw( to number flux
20
TRAPPEDRADIATION: THEVANALLENBELTS
This figure shows VanAllen's first mapof the radiation belt, showing the
inner and outer zones of high count rate. The contours are labeled by the count
rate of a Geiger counter of about 1 cm2 area covered by 1 gm/cm2 of lead,
_.,: .' ' " J I0
"! _* -'P W"" .... Pro,onL £,>JO Me.
,o
_ /io r_,_m. E.>l.t M.
V_ AIIon'o (INI mop. _r the radieai.n bell, showinll fl,e
lnncr Ind O_lW _ o1'hlllh cYdYUfllroll, 1'hi cOfllOursii1 labcIcd hy I1_
¢ounl nile oT II O_lllr _goufll_¢o( ml_ul I cm _ stem _ovtrcd by I IIm/cm 0
of bed 12.11,
21
Trapped radiation
Data Center (NSSDC).
NSSDCTRAPPEDRADIATIONMODELS
models are available from the National Space Sciences
II-I iqp er _1-4 elec_l_m rl_mm br Iflo,_ch IW4,
t_m _rm._. !.$ I_v. Self urd w
AP8MIN OMNIDIRECTIONAL FLUX (PROTONS/CM'-SEC)
10 i0'
10 I0'
Er_erly > I 0 #,4eV
51 tO'
_ EIr_n hid.
J 51 I0'
ApflM|N R-), plot of eonet|n! intensity nttx oorlloU_l'_
with an en_rlrY of Z 1.0 MeV.
22
SYSTEMGENERATEDNVIRONMENT
The system-generated environment is system-specific and maybe quite
complex. It is generally considered to be the main source of contaminants which
can impact the system.
DEPENDSONSYSTEMCHARACTERISTICS
NEUTRALS:OUTGASSING,THRUSTEREJECTA,DUMPS,RAM/WAKE
CHEMICALREACTIONS:DEGRADATION,CONTAMINATION
LOCALLYENHANCEDPRESSURES
PLASMAS:
RAM/WAKE
PHOTOIONIZATIONRCHARGEXCHANGEOF NEUTRALS,DIRECT,
ENHANCEDPLASMAINTERACTIONS
COUPLINGTOAMBIENT: POTENTIALCHANGES
0
0
ENERGETICHARGEDPARTICLES:ELECTRONORIONBEAMS
.
- BEAM-PLASMAINTERACTIONS:HEATING,WAVES,EMI
- INTERACTIONSWITHNEUTRALS:EXITATION,IONIZATION,BPDf
- ENHANCEDPLASMAINTERACTIONS
- CURRENTBALANCEALTERATIONS:POTENTIALCHANGES
ELECTRICANDMAGNETICFIELDS: EXPOSEDV's, CURRENTS,RESIDUALS,VxB
- TORQUESANDFORCES:ATTITUDECONTROL
- PLASMASHEATHEFFECTS:PLASMAINTERACTIONS
- STIMULATIONOFWAVES,INSTABILITIES: EMI, PLASMAINTERACTIONS
_Electromagnetic interference
_Beamplasma discharge
23
SUMMARY
The orbital environment is complex, dynamic, and comprised of both natural
and system-induced components. Several environment factors are important for
materials. Materials selection/suitability determination requires consideration
of each and all factors, including synergisms amongthem. Understanding and
evaluating these effects will require ground testing, modeling, and focused flight
experimentation.
ORBITALENVIRONMENTIS COMPLEX
0 NATURAL
0 SYSTEM-INDUCED
ENVIRONMENTFACTORSIMPORTANTFORMATERIALSINCLUDE:
0
0
0
0
0
0
SOLAR RADIATION
METEOROIDS AND DEBRIS
NEUTRAL ATMOSPHERE
PLASMAS
TRAPPED RADIATION
SYSTEM-GENERATED CONTAMINANTS
MATERIALS SELECTION/SUITABILITY DETERMINATION REQUIRES CONSIDERATION OF ALL FACTORS
24


Overview of environmental factors

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