Satellite Thermal Control Engineering
prepared for “SME 2004"
OLYMPUS
HIPPARCOS
MSG
ULYSSES
SOHO
ERS
ENVISAT
CASSINI
L1
HUYGENS
ECS
ARIANE
ISS
SPACELAB
ISO
ARTEMIS
GIOTTO
[email protected]
European Space Agency, Estec, Thermal and Structure Division
Keplerlaan 1, PO Box 299, 2200AG Noordwijk, The Netherlands
Tel25jun04,
+31 715654554,
Fax +31 715656142
SME04,
[email protected]
1 of 66
ESTEC
Thermal & Structure Division
Satellite Thermal Control Engineering
What you will learn?
1. heat transfer basics
3. role
– conduction
– why thermal control required?
– radiation
– importance of thermo-optical
properties
4. design
– what is thermal design?
– which types of S/C design
exist?
2. satellite energy balance
– from ground to space
– simple satellite thermal
behaviour
5. means
SME04, 25jun04, [email protected]
– what to control the
flux/temperatures
2 of 66
ESTEC
Thermal & Structure Division
1. Heat Transfer Basics
ROSETTA* FM in LSS, dec01
Thermal Control Engineering
1. heat transfer basics
2. satellite energy balance
3. role
4. design
5. means
*without Solar Panels
SME04, 25jun04, [email protected]
3 of 66
ESTEC
Thermal & Structure Division
1.1 Satellite Heat Transfer Modes
ROSETTA* FM in LSS, dec01
1. Heat Transfer Basics
1.1
satellite heat transfer modes
1.2
conduction
1.3
radiation
*without Solar Panels
SME04, 25jun04, [email protected]
4 of 66
ESTEC
Thermal & Structure Division
1.1 Satellite Heat Transfer Modes
• Conduction
– between any body
– eventually by contact through an interface
• Radiation
– main mode of heat transfer in vacuum/space
• Convection
– manned tended satellites (ISS, shuttle, launchers, ascent…)
• Ablation
– combination of 3 and chemical reaction (re-entry vehicles)
SME04, 25jun04, [email protected]
5 of 66
ESTEC
Thermal & Structure Division
1.2 Conduction
ROSETTA* FM in LSS, dec01
1. Heat Transfer Basics
1.1
satellite heat transfer modes
1.2
conduction
1.3
radiation
*without Solar Panels
SME04, 25jun04, [email protected]
6 of 66
ESTEC
Thermal & Structure Division
1.2 Conduction
• Definition
– propagation of energy from particle to particle
– in solid, liquid or gaseous continuous matter, homogeneous or not
– without matter displacement
r
q
r
r
q = − k ∇T
• Fourier’s Law
r
– q
– k
r
n
T(x,y,z)
is the heat flow rate vector (W/m2)
is the material thermal conductivity (W/m2.K)
– one-dimensional conduction
Th
T(x)
k
A
Tc
l
SME04, 25jun04, [email protected]
k A
Q=
(Th − Tc )
l
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ESTEC
Thermal & Structure Division
1.2 Conduction - Data
Thermal Conductivity
1.E+03
Copper
1.E+02
Aluminium
AA5083-T0
k (W/m.K)
1.E+01
304 ss
G-10 // to warp
1.E+00
Ti
Epoxy
1.E-01
PE //
1.E-02
Cu-Ni (70-30)
Brass Cu-Zn (90-10)
Mylar PET amorphous
1.E-03
1.E-04
1
10
100
1000
Temperature (K)
SME04, 25jun04, [email protected]
8 of 66
ESTEC
Thermal & Structure Division
1.3 Radiation
ROSETTA* FM in LSS, dec01
1. Heat Transfer Basics
1.1
satellite heat transfer modes
1.2
conduction
1.3
radiation
*without Solar Panels
SME04, 25jun04, [email protected]
9 of 66
ESTEC
Thermal & Structure Division
1.3 Radiation
• Characteristics
– propagation of electro-magnetic energy in straight line
– between surfaces separated by
• absorbing, scattering media
• or in vacuum
– hence without matter displacement
– reflected, absorbed or transmitted on surrounding bodies
• Source
– thermal agitation of particles
SME04, 25jun04, [email protected]
10 of 66
ESTEC
Thermal & Structure Division
1.3 Radiation - Black Body
• Black Body
– is real or fictitious surface
– that absorbs all incident radiant energy i.e.
α (θ , λ ) = α = 1
• from every direction
• at every wavelengths
– isotropic emitter
ε (θ , λ ) = ε = 1
• radiated energy depends only on temperature
• Black Body Emitted Energy
hemispherical spectral
emissive power
hemispherical total
emissive power
Planck’s Law
Eλ ,T
2π h c2
=
hc


5  kB λT
λ e
− 1




Stefan-Boltzmann’s Law
∞
(W/m2.µm)
Ebb ,T = ∫ Eλ ,T dλ = σ T 4
SME04, 25jun04, [email protected]
(W/m2)
0
11 of 66
ESTEC
Thermal & Structure Division
Radiation
– Black Body Laws
Planck
and
Stefan-Boltzmann
Planck1.3
and
Stefan-Boltzmann
Laws
0.8
0.8
1.50
1.50
12
12µm
µm
0.5
0.5µm
µm
5776
5776KK
255
255KK
1.25
1.25
HemisphericalSpectral
Spectral
λ,Τ
EEλ,Τ
, ,Hemispherical
EmissivePower
Power(10
(1077W/m
W/m22.µ.µm)
m)
Emissive
HemisphericalSpectral
Spectral
λ,Τ
EEλ,Τ
, ,Hemispherical
14
2
14 W/m
2 .µm)
Emissive
Power
(10
Emissive Power (10 W/m .µm)
1.0
1.0
1.00
1.00
0.6
0.6
0.75
0.75
0.4
0.4
0.2
0.2
SUN
SUN
EARTH
EARTH
4
4
Area
Area==σσTTSS
0.0
0.0
0.1
0.1
0.50
0.50
0.25
0.25
4
4
Area
Area==σσTTEE
1.0
10.0
1.0
10.0
λ,
λ,Wavelength
Wavelength(µm)
(µm)
SME04, 25jun04, [email protected]
0.00
0.00
100.0
100.0
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ESTEC
Thermal & Structure Division
1.3 Radiation - Real Body
• can absorb, reflect or transmit radiation energy
Φλ incident
ρd Φλ diffusely
reflected
- all parameters are wavelength and
angular dependent
ρs Φλ
specularly
reflected
- general case: semi-transparent
α (λ ) + ρ (λ ) + τ (λ ) = 1
ρ = ρs + ρd
α Φλ absorbed
τ Φλ transmitted
- opaque
hence
SME04, 25jun04, [email protected]
τ (λ ) = 0
α (λ ) + ρ (λ ) = 1
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ESTEC
Thermal & Structure Division
1.3 Radiation - Real Body
• Surface Emissivity
– ratio of surface radiated energy to that of a black body at the same T
– always <1 for a real surface
∞
ε (θ , λ ) =
∫α
Eλ ,T dλ
λ ,T
<1
0
∞
∫E
λ ,T
for a black body
ε (θ , λ ) = ε = 1
dλ
0
– depends on direction θ and wavelength λ of emitted energy
– therefore can be
• directional (d) or hemispherical (h)
• spectral (s) or total (t)
• averaged over all directions, wavelengths or both
SME04, 25jun04, [email protected]
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ESTEC
Thermal & Structure Division
1.3 Radiation - Real Body
• Surface Absorptivity
– ratio of surface absorbed energy to incident energy
– always <1 for a real surface
∞
α (θ , λ ) =
∫α
0
Eλ ,T dλ
λ ,T
<1
∞
∫E
λ ,T
for a black body
dλ
α (θ , λ ) = α = 1
0
– depends on incident energy direction θ and wavelength λ
– therefore can be
• directional (d) or hemispherical (h)
• spectral (s) or total (t)
• averaged over all directions, wavelengths or both
SME04, 25jun04, [email protected]
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ESTEC
Thermal & Structure Division
1.3 Radiation - Real Body
• Absorptivity vs Emissivity
– for a given direction θ and at any wavelength λ
2nd Kirchoff’s Law
α (θ , λ ) = ε (θ , λ ) ∀θ , ∀λ
– in general hemispherical total values are different
α ≠ε
because
–
α and ε have a strong wavelength dependence
–
source temperature of incident radiation (Sun at 5776 K) different
than surface temperature (satellite –250 -> 300°C)
SME04, 25jun04, [email protected]
16 of 66
ESTEC
Thermal & Structure Division
1.3 Radiation - Real Body
• Solar Absorptivity αS and Hemispherical Emissivity εH
αS is the solar absorptivity
αS = εS integrated over 0.2-2.8 µm
⇒ refers to UV wavelengths
i.e. 95% solar spectrum
εH is the hemispherical emissivity
αH = εH integrated over 5-50 µm
⇒ refers to IR wavelengths
i.e. body at –250/300°C
but
αS ≠ εH because the spectra are different
SME04, 25jun04, [email protected]
17 of 66
ESTEC
Thermal & Structure Division
1.3 Radiation - Data
• Spectral Reflectance ρ
– integration over solar
(5776K) wavelengths
• α s=0.20
– integration over
infrared
black body (300K)
wavelengths
• ε h=0.87
12
12µm
µm
1.3
1.3
1.0
1.0
0.8
0.8
5776 K
5776 K
255 K
255 K
Reflectance
Reflectance
1.00
1.00
0.75
0.75
µµ
0.5
0.5 m
m
0.50
0.50
0.5
0.5
0.25
0.25
0.3
0.3
0.0
0.0
0.1
0.1
1.0
1.0
10.0
10.0
ρ Spectral Reflectance (-)
ρ, ,Spectral
Reflectance (-)
• Black Body Emittance
1.5
1.5
λ,Τ, Hemispherical Spectral
EE
λ,Τ, Hemispherical Spectral
EmissivePower
Power(10
(101414or
or10
107 7W/m
W/m2.2µ.µ
m)
Emissive
m)
– Zinc Oxide Potassium
Silicate Coating
MAP
MAPPSG120-FD
PSG120-FDReflectance
Reflectance
0.00
0.00
100.0
100.0
λλ, ,Wavelength
Wavelength(µ(µm)
m)
SME04, 25jun04, [email protected]
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ESTEC
Thermal & Structure Division
1.3 Radiation - Data
• Typical Values
Finish
VD Au
VDA
black paint
white paint
SSM (Ag 2 mils)
OSR
αS
0.23
0.15
0.94
0.20
0.10
0.09
εH
0.03
0.05
0.81
0.88
0.60
0.82
SME04, 25jun04, [email protected]
αS/εH
9.20
3.00
1.16
0.23
0.17
0.11
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ESTEC
Thermal & Structure Division
1.3 Radiation - Black Body
• Radiated Energy between Black Bodies
(
Qij = Ai Fij σ Ti 4 − T j4
)
with Fij, the view factor
between surface i and surface j
or
(
Qij = Ai σ Ti 4 − T j4
when
Ai
Ti
Qij
Aj
dAi
Tj
dAj
)
Fij = 1
SME04, 25jun04, [email protected]
20 of 66
ESTEC
Thermal & Structure Division
2. Satellite Energy Balance
ROSETTA* FM in LSS, dec01
Thermal Control Engineering
1. heat transfer basics
2. satellite energy balance
3. role
4. design
5. means
*without Solar Panels
SME04, 25jun04, [email protected]
21 of 66
ESTEC
Thermal & Structure Division
2. Satellite Energy Balance
WHAT HAPPENS from
GROUND
to
SPACE ?
SME04, 25jun04, [email protected]
22 of 66
ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Thermal Environment
• Ultra-high Vacuum, 10-14 bar < p < 10-17 bar => no convection
– temperature levels
• Deep Space, @ 2.7 K
RA
MB
U
N
PE
– imbalance, temperature levels and gradients
UMBRA
• Solar Eclipse
– SSO SPOT, ENVISAT 32 mn
– GEO MSG
72 mn
– HEO CLUSTER
5 h max
RA
MB
U
PEN
0°52’
SME04, 25jun04, [email protected]
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ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Thermal Environment
intense Solar Flux, SC=1367 W/m2 @ 1 AU
–
imbalance, temperature levels and gradients
Solar Intensity vs Sun Distance
1000000
Earth
10.0
10000
1000
1.0
Saturn
100
0.1
Mars
10
Jupiter
1
0.1
1
0.0
10
Sun Distance (AU)
SME04, 25jun04, [email protected]
Solar Intensity (SC)
SC
ΦS = 2
dS
100.0
Mercury
100000
Intensity (W/m2)
•
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ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Thermal Environment
σ TE 4 4 π R E 2
• Albedo Flux
– reflected by Sun illuminated side of Planet
– albedo = ratio of solar reflected energy to
local solar flux
– Earth albedo
aE = 0.33 ± 0.13 equivalent to 410 W/m2
– aE varies with landscape
clouds 0.4-0.8
forest 0.05-0.10
ocean 0.05
emitted
(1 − a ) SC πRE
2
absorbed
• Planet Flux
– infrared energy radiated by the Planet
– Earth=blackbody @255 K (-18 °C)
equivalent to 240 W/m2
a SC π RE
SC
reflected
incident
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ESTEC
Thermal & Structure Division
2
Equilibrium
Temperature
of
2. Satellite
Energy Balance
Equilibrium
Temperature
of aa Sphere
Sphere
from
from Ground
Ground to
to Space
Space
100000.0
100000.0
Altitude(km)
(km)
Altitude
10000.0
10000.0
1000.0
1000.0
100.0
100.0
10.0
10.0
Black
Black
White
White
Gold
Gold
Air
Air
1.0
1.0
0.1
0.1
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0
204
24
0
200
20
SME04, 25jun04, [email protected]
0
106
16
0
102
12
80
80
0
40
40
0
0
-04
-4
0
-08
-8
0
-102
-12
Temperature
Temperature(degC)
(degC)
ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Black Sphere
• Assumptions
– satellite=black sphere hence α=ε=1
– infinitely conductive, deep space at 0 K
– low orbit around Earth
• in Sun
– no Planet, no albedo
(π r ) q = (4 π r ) σ T
2
2
4
α=ε=1
S
qS
=σ T 4
4
r
qS
T
T = 5o C
SME04, 25jun04, [email protected]
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ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Black Sphere
• in Sun with Earth
– no albedo
(π r ) q
2
S
(
)
(
)
+ F 4 π r 2 σ TE4 = 4 π r 2 σ T 4
F=1/2
α=ε=1
qS σ TE4
+
=σ T 4
4
2
r
qS
Earth
TE
T
T = 27o C
∆T = 22 o C
SME04, 25jun04, [email protected]
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ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Black Sphere
• in Sun with Earth and Albedo
(π r ) q
2
S
(
)
(
)
(
)
+ F 4 π r 2 σ TE4 + F 4 π r 2 a q S = 4 π r 2 σ T 4
σ TE4
1 a
=σ T 4
 +  qS +
2
 4 2
α=ε=1
Earth
r
qS
T = 56 o C
F=1/2
TE
T
∆T = 29o C
qS
SME04, 25jun04, [email protected]
albedo=a qS
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ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Real Body
radiated to deep space
qs
Qr = ei Ai Fi, space s (Ti 4 − Tspace4 )
solar absorbed
qs Fi,s Ai ai
albedo absorbed
qs
qs a Fi,a Ai ai
radiated to planet
Qp =ei Ai Fi,p s (Ti −Tp )
4
SME04, 25jun04, [email protected]
4
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ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Real Body
• Real Body in Sun
– assumes that body in infinitely conductive, no albedo, no planet flux
– assumes that sink temperature is 0 K (not far from deep space)
qs
As
T is independent of area A
depends only of α/ε
A
α As qs = ε A σ T
4
α
qs
4
T=
Fs
ε
σ
where F S is the projected area
As
Fs =
A
SME04, 25jun04, [email protected]
α
T=
ε
4
4
Fs 394 K
with qs = 1367 W/m2
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ESTEC
Thermal & Structure Division
flat plate
cylinder
S
S
n
r
θ
θ
r
h
n
l
sphere
w
Surface
1-s plate
2-s plate
cylinder
sphere
cube
FS
1
1/2
1/π
1/4
1/6
α 1.00 0.20 0.94 0.23 0.15 0.20
ε 1.00 0.88 0.81 0.025 0.05 0.20
α/ε 1.00 0.23 1.16 9.20 3.00 1.00
Ap / A
Steady-State Temperature (degC)
1.00 121
-1 136
413 245 121
0.50
58
-44
71
304 163
58
0.32
23
-69
34
242 116
23
0.25
5
-81
16
212
94
5
0.17
-21 SME04,
-99 25jun04,
-12 [email protected]
165
58
-21
black
CFRP
sand-blasted
Al
VDA
VDAu
black paint
Electrodag 501
(-)
white paint
PSG120-FD
2
(W/m )
S
1367.0
black
body
for θ=0, TS = 0 K and qs = 1367 W/m2
PLAY with
α/ε
RATIO
0.90
0.80
1.13
133
68
32
14
-14
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ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Real Body
• Steady-state: General Case
– assumes that body in infinitely conductive
– solar, albedo and planet fluxes
– view factor to sink temperature at Ts≠0 K
Fs, Fa, Fp solar, albedo, planet factors (-)
qs, qa, qp solar, albedo, planet fluxes (W/m2)
a
Ts
BS
Q
albedo factor
sink temperature
Gebhart factor to sink
power dissipation
(
(-)
(K)
(-)
(W)
Bs
qs
As
Ts
A
qa = a qs
qp
α solar absorbtivity (-)
ε infrared emissivity (-)
A radiative area
(m2)
)
ε A BS σ T 4 − TS4 = α Fs A qs + α Fa A qa + ε Fp A q p + Q
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ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Real Body
Ts
Bs
As
qs
qa = a qs
A
solar
infrared
dissipation
α (Fs + a Fa ) qs Fp 4
Q
4
T =4
+ Tp + TS +
ε
BS
σ BS
ε A BS σ
qp
when sink Ts surrounds (BS=1) body at T and only solar flux qs
α
qs
T=
Fs + TS4
ε
σ
4
SME04, 25jun04, [email protected]
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ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Examples
ULYSSES
(1989)
•s
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ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Examples
ISO
(1995)
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ESTEC
Thermal & Structure Division
2. Satellite Energy Balance - Examples
ARTEMIS
(2001)
SME04, 25jun04, [email protected]
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ESTEC
Thermal & Structure Division
3. Role
ROSETTA* FM in LSS, dec01
Thermal Control Engineering
1. heat transfer basics
2. satellite energy balance
3. role
4. design
5. means
*without Solar Panels
SME04, 25jun04, [email protected]
38 of 66
ESTEC
Thermal & Structure Division
3. Role
• maintain within Specified Ranges
–
–
–
–
temperatures
temperature gradients (K/length)
temperature stability (K/time)
radiative/conductive
heat flow
(W)
SPOT 5 Solid State Recorder (ALS)
On Board Data Compression Unit (ALS)
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ESTEC
Thermal & Structure Division
3. Role
SOHO, STM
• of What?
–
–
–
–
electronic units
instrument e.g. optical bench
S/C structure
interface between modules
PLM
15
Instruments
Visual Monitoring Camera (AST)
SVM
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ESTEC
Thermal & Structure Division
3. Role - Typical Requirement
• Narrow Temperature Ranges
– electronics equipment
• classical equipment
• battery
• propulsion system
[ -10, +40] °C
[ 0, +20] °C
[ +10, +50] °C
• limited Temperature Gradients
–
–
–
< 5°C
across optical instrument (1.5 m)
< 2°C/m for structural element
< 5°C
between MMH and NTO tanks
∆T
∆T/∆x
∆T
• Stable Temperatures
–
–
–
< 5 K/h
< 0.1 K/mn
< 100 µK/mn
∆T/∆t
∆T/∆t
∆T/∆t
for typical electronic unit
for CCD camera
for cryogenic telescope
• Why is it so important?
– low temperatures
– narrow temperature ranges
– small temperature gradients
for reliability of components
for sensitivity of detectors, units
for pointing of instruments, S/C
SME04, 25jun04, [email protected]
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ESTEC
Thermal & Structure Division
4. Design
ROSETTA* FM in LSS, dec01
Thermal Control Engineering
1. heat transfer basics
2. satellite energy balance
3. role
4. design
5. means
*without Solar Panels
SME04, 25jun04, [email protected]
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ESTEC
Thermal & Structure Division
4. Design
stored energy
(mCP )i
conducted* flux
dTi
=
dt
∑
j
radiated* flux
fluid flow
(not visualised)
internal external
loads
loads
Cij (Tj −Ti ) + ∑ Rij s (Tj −Ti )+ ∑ Fij (Tj −Ti ) + Qii + Qie
4
*/convective
Space
Node s
Ts
j
*incl. to space
*excl. to planet
radi
Ris σ ation
(T 4i T 4
s )
tion*
c
u
d
con
-T i)
T
(
k
C ik
Node k
Tk
4
j
tion*
c
u
d
con
-T j)
T
i
(
C ij
Node i
Ti mCi α i ε i
tion
radia 4-T i4 )
T
Rikσ( k
Solar UV
Node j
Tj
tion
radia 4 T 4 )
- j
Rijσ (Ti
Pla
ne
Al
t
be
IR
do
UV
* convective
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ESTEC
Thermal & Structure Division
4. Design
Balance HEAT FLOWS
to fulfil
REQUIREMENTS
results in
TEMPERATURES
• through Heating
– absorb from external sources (solar, albedo, planet IR)
• selective coatings
– use the internal sources
• electronic dissipations, MLI insulation efficiency
– dissipate heat internally
• heater
• RTG, RHU
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ESTEC
Thermal & Structure Division
4. Design
– transfer heat from hot area
• conduction, radiation
• latent heat of evaporation/condensation
• or through Cooling
– reject to deep space (3 K)
• with low α/ε radiative coatings on radiators
– transfer heat to cold area
• by conduction,
• radiation
• through condensation/boiling in fluid loops or heat pipes
– through cryogenic techniques
• cryostats
• coolers (Peltier, Joule-Thomson…)
– ablation
SME04, 25jun04, [email protected]
45 of 66
ESTEC
Thermal & Structure Division
4. Design – Radiative Concept
PROBA1 FM
• Principle
– when internal power dissipation small w.r.t.
external absorbed energy
– balance between
• absorbed incident radiant energy (solar…)
• emitted radiant energy (σT4)
• Characteristics
– no insulation
– average temperature driven by
• external fluxes
– local temperature hot spots still possible
• Application: PROBA1
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ESTEC
Thermal & Structure Division
4. Design – Insulated Concept
• Principle
– when heat source irradiates few sides
• Sun, planet IR (Mercury, Mars, Moon)
XMM FM
1999
– balance between
• internally dissipated power (P)
• emitted radiant energy (σT4)
HYPPARCOS FM, 1990
• Characteristics
– insulation of Sun illuminated sides (MLI)
– shadow sides
• with high IR emissivity
• radiate to deep space => RADIATORS
– preferred attitude for radiators
– average temperature driven by
• internal power dissipation
– local temperature hot spots still possible
SME04, 25jun04, [email protected]
47 of 66
ESTEC
Thermal & Structure Division
4. Design – Insulated Concept
ASTRA-1K FM Antenna Deployment
• Advantages w.r.t. Radiative Concept
– less sensitive to
• eclipses
• external loads changes
– temperatures are more uniform
– little ageing of unirradiated coatings
We are between
those
2 CONCEPTS
SME04, 25jun04, [email protected]
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ESTEC
Thermal & Structure Division
5. Means
ROSETTA* FM in LSS, dec01
Thermal Control Engineering
1. heat transfer basics
2. satellite energy balance
3. role
4. design
5. means
*without Solar Panels
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ESTEC
Thermal & Structure Division
5. Means - Limitations
• Cooling Limitations
– radiator
– cryo-coolers
– liquid He
100 mW
1W
few mW
at 100 K
at 50 K
at 4 K
for 0 W dissipation
for 100 W dissipation
for 1 ton/2 years
• Heat Transport Limitation/Performance
– conduction (pure Al tube k=200 W/m.K)
1.5 W @20°C
l=1.00 m
Ø=2 cm
11 kW@20°C
l=0.70 m
Ø=4.04 m
– heat pipe (Al tube)
11 kW @20°C
l=0.70 m
Ø=2.5 cm
– radiation (from a black surface ε=1)
11 kW @20°C
A= 88 m2
11 kW @20°C
A= 27 m2
SME04, 25jun04, [email protected]
∆T= 25 K
∆T= 3 K
m= 0.8 kg
m= 24 t
∆T= 3 K
m=
2 kg
∆T= 25 K
∆T= 290 K
50 of 66
ESTEC
Thermal & Structure Division
5. Means
α φs A
ε Aσ T
4
RADIATION
CONDUCTION
- coating
- absorber
- MLI blanket
- radiator
- structural material
- doubler, filler, adhesive
LATENT HEAT-ABLATION
PASSIVE
ACTIVE
- TPS
- PCM
k
A
∆T
l
- washer, strap, bolt, tyrap,
stand-off
- foam
HEATERS
HEAT PIPES - FLOOPS
- thermostat control
- fixed/variable conductance
- electronic control
- ground control
- loop heat pipe
- monophasic/diphasic fluid
PASSIVE
ACTIVE
LOUVRES
COOLERS
ENERGY
ENERGY
CONTRIBUTION
CONTRIBUTION
- mechanical
- electrical
SME04, 25jun04, [email protected]
ENERGY
ENERGY
TRANSFER
TRANSFER
51 of 66
ESTEC
Thermal & Structure Division
5. Means
• Passive Systems Pros/Cons
– no mechanical moving parts or moving fluids, no power consumption
• simple to design/implement/test
• low mass and cost
• highly reliable
– BUT low heat transport capability
• except heat pipes
• Active Systems Pros/Cons
– mechanical moving parts or moving fluids or electrical power required
•
•
•
•
complex design
generate constraints on S/C design and test configurations
high mass and cost
less reliable than PTC means
SME04, 25jun04, [email protected]
52 of 66
ESTEC
Thermal & Structure Division
5. Means - PTC – Radiation, Coatings
Coated Sphere Equilibrium
Temperature in Sun
• controls Heat absorbed by
External S/C Surfaces
– with α, solar absorptivity
α/ε=10
500 K
α/ε=2
337 K
α/ε=1.5
314 K
α/ε=1
284 K
α/ε=0.75
• controls Heat radiated
to Space
264 K
α/ε=0.5
– with ε, IR emissivity
238 K
α
α/ε=0.25
200 K
ε
SME04, 25jun04, [email protected]
53 of 66
ESTEC
Thermal & Structure Division
5. Means - PTC - Radiation, MLI Blankets
ε
ε
ε
ε
• Purpose
Thot
– insulating material
– acts as a radiation barrier
– decreases heat flow inside S/C
• Sun, albedo, IR planet
• ascent aerothermal after fairing jettison
• ME/ABM firing
Tcold
– decreases heat losses from S/C
Thot
• IR energy
ε/n
Tcold
• Principle
– stack of n layers with low emissivity ε
– connected only by radiation with limited
contact areas
– equivalent to reduce the emissivity by n
SME04, 25jun04, [email protected]
54 of 66
ESTEC
Thermal & Structure Division
5. Means - PTC - Radiation, MLI Blankets
• Standard MLI
– stack of thin polymer foils
• Kapton®, Mylar® (5-25 foils)
– separated (avoid contact) by
• spacer/mesh (Dacron®/Trevira®)
• embossed, crinkled
• perforated or not
– 1x
bka/VDA-net
unperf.
3-23 x VDA/my/VDA-net perf.
1x
VDA/my or ka/VDA perf.
– attachment
1 mil
0.25 mil
1 mil
space exposed side
internal layers
innermost layer
• stand-offs + clip washers
• sewed/glued velcro
• dacron yarn
SME04, 25jun04, [email protected]
55 of 66
ESTEC
Thermal & Structure Division
5. Means - PTC - Radiation, Radiators
• Purpose
– cool detectors, optical components, mirrors
– improve the performances of
Qspace
• Scientific P/L (all wavelength ranges)
• Earth observation (mainly IR)
• Principle
– direct coupling to deep space @2.73 K
Q space = Q electric + Q losses
– heat lift decreases in T4
Qelectric
Qlosses
insulation
satellite
6 W/m2 @100K
SME04, 25jun04, [email protected]
56 of 66
ESTEC
Thermal & Structure Division
5. Means - PTC - Radiation, Radiators
MLI
INTEGRAL STM
radiators
SME04, 25jun04, [email protected]
57 of 66
ESTEC
Thermal & Structure Division
5. Means - PTC – Conduction, Increase
• Structural Material Selection
– Al alloy
– Ti alloy
– steel
120-170 W/m.K
7-15 W/m.K
10-40 W/m.K
doubler
facesheets
S/C wall
unit
honeycomb
• Thermal Doublers
strap
– spread heat dissipation under unit
– 1 mm thick Al alloy sheet
• Straps/Braid (detector to radiator)
– Cu, Al alloy wrapped in MLI/SLI
– short < 10 cm
radiator
S/C structure
• Contact Area
SME04, 25jun04, [email protected]
58 of 66
ESTEC
Thermal & Structure Division
5. Means - PTC – Conduction, Increase
• Interface Fillers
– better unit to S/C conductance
– graphite (Sigraflex®)
• laminated graphite sheet
• electrical conductor
• thickness
0.25 mm
unit
– silicone elastomer (Cho-therm® 1671)
filler
• silicone binder, filled with boron nitride
particles, reinforced with fibreglass
cloth
• electrical isolator
honeycomb
SME04, 25jun04, [email protected]
59 of 66
ESTEC
Thermal & Structure Division
5. Means - ATC - Louvres
bi-metallic spring
housing (low ε)
blades
(low ε)
– dumps more/less power to space
– accommodate extreme variation of
energy
• internal power
• solar fluxes (interplanetary S/C)
frame
(low ε)
– with little temperature change
– save heater power
radiator
(high ε)
actuator
• Principle
blades
θ
S/C radiator
bearings
• Purpose
S/C radiator
bearings
– blades covering a standard radiator
– 16 blades on bearings rotates
– opens/closes radiator to deep space
• variation of IR emittance ε
– actuator: bi-metallic spring sensing
the radiator temperature
bearings
SME04, 25jun04, [email protected]
60 of 66
ESTEC
Thermal & Structure Division
5. Means - ATC - Louvres
SENER Louvre on ROSETTA* PFM
Louvre on CASSINI-HUYGENS
louvre
*without Solar Panels
SME04, 25jun04, [email protected]
61 of 66
ESTEC
Thermal & Structure Division
5. Means - ATC - Heaters
• Purpose
– additional source of heat inside S/C
• replace power when unit is switched-off
• warm up dormant units prior to swon
• control temperature and gradient
metal
run
line in
line out
kapton
SME04, 25jun04, [email protected]
62 of 66
ESTEC
Thermal & Structure Division
5. Means - ATC - Heaters
ROSETTA FM Heaters
heaters
PCU
Battery 3
ROSETTA FM ROSINA DPU
heaters
Battery 2
SME04, 25jun04, [email protected]
63 of 66
ESTEC
Thermal & Structure Division
5. Means - ATC - Heaters
ROSETTA FM Thruster 12A
ROSETTA FM OSIRIS PEM-H
glue
FCV
selfredundant
heaters
SME04, 25jun04, [email protected]
64 of 66
ESTEC
Thermal & Structure Division
5. Means - ATC - Heat Pipes
Grooved Heat Pipe
• Purpose
– transport heat by convection with small ∆T
– avoid temperature gradients
• Principle
–
–
–
–
liquid vaporizes at evaporator
gas flows to cold end
gas condensates at cold end
liquid returns by capillary forces
Qin
groove
Qout
adiabatic section
evaporator
liquid
vapour
liquid
condenser
SME04, 25jun04, [email protected]
65 of 66
ESTEC
Thermal & Structure Division
5. Means - ATC - Heat Pipes
Ø 12 mm
Telecom Panel Heat Pipe (Swales)
bi-tube
saddle
SME04, 25jun04, [email protected]
66 of 66
ESTEC
Thermal & Structure Division