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National Aeronautics and Space Administration
www.nasa.gov
Ground Plane and Near-Surface Thermal
Analysis for NASA’s Constellation
Programs
TFAWS-08-1017
Ground Plane and Near-Surface Thermal
Analysis for NASA’s Constellation
Programs
TFAWS-08-1017
Joseph F. Gasbarre, Ruth M. Amundsen, Salvatore Scola
NASA Langley Research Center
Frank B. Leahy and John R. Sharp
NASA Marshall Space Flight Center
TFAWS 2008
August 21, 2008
Joseph F. Gasbarre, Ruth M. Amundsen, Salvatore Scola
NASA Langley Research Center
Frank B. Leahy and John R. Sharp
NASA Marshall Space Flight Center
TFAWS 2008
August 21, 2008
2National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Outline
♦Background
♦Near-Surface Thermal Modeling Importance
♦Near-Surface Thermal Modeling Challenges
♦Cases Where Vehicle Effects on the Ground Plane are Significant
♦Cases Where Vehicle Effects on Ground Plane are Negligible
♦Near-Surface Natural Environment
♦Parametric Study Results
♦Conclusions
3National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Near-Surface Thermal Modeling Importance
♦Ares I and Ares I-X utilize passive thermal control of the avionics • Pre-launch ground-supplied purge to pre-condition avionics to survive
ascent w/o purge (thermal capacity)
• KSC on-pad environments significant in determining initial temperatures
♦For lunar-based vehicles/habitats, surface regolith temperature
can be greatly influenced by vehicle and vice versa• Example: Regolith range of ~200°C in proximity to lander, engine nozzle
predictions different by 50°C compared to constant surface temperature.
4National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Near-Surface Thermal Modeling Challenges
♦Most software tools for spacecraft thermal analysis were
originally designed for spacecraft in orbit
♦Vehicle on surface presents different challenges
♦Using standard TD orbit calculations, planet IR load
overestimated• Vehicle coupled to ‘space’ sink over entire spherical 360°• ‘Space’ is relatively warm sky temperature
• Planet IR heat load counted on top of space/sky sink
♦Using modeled planet surface can lead to run time issues• Large planet surface � large bounding box
• Many rays must be shot from planet to accurately characterize vehicle
interaction
♦Methods developed for two scenarios• Substantial vehicle effect on ground (short/close)
• Negligible vehicle effect on ground (tall/thin)
5National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Cases Where Vehicle Effects on Ground
Plane Are Significant
♦Vehicle substantially affects ground temperature variation• Vehicle close to surface
• Vehicle form short/squat
• Substantial vehicle shadow on surface
• Examples− Orion Flight Test Program’s Pad Abort tests
− Lunar surface missions
♦Ground thermal variation affects vehicle• Ground temperatures modeled with ground plane
• Ground plane modeled to constant-temperature depth
• Low conductivity lunar regolith intensifies shadow effect
♦Modeled ground plane used for planet IR and albedo
6National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Cases Where Vehicle Effects on the Ground Plane
are Significant
♦ First set of Orion flight tests to
be held at White Sands Missile
Range (WSMR) in NM
♦ Pad Abort Test: Orion Launch
Abort System and Crew
Module placed on separation
ring approx. 1 m off ground
♦ Interaction of ground and
vehicle effects internal heat
load and sizing of
environmental control system
♦ Shadow to sunlit ground
gradients up to 60ºF
♦ Progression of shadow
follows path of sun overhead;
dependent on time of year
Slideshow of PA-1 Test Article
showing diurnal shadow contours
(6 AM – 7 PM LST)
Orion Pad Abort 1 Flight Test
7National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
♦Ares I, V and I-X:• Vehicle form tall, thin
• Blockage from the Mobile Launch Platform
• Vehicle has little effect on ground temperature variation
• Local ground temperature variation has little impact on vehicle
♦When ground temperature not influenced by vehicle, avoid
including modeled ground plane in radiation calculations• Bounding box for radiation calculation becomes huge, oct cells large,
renders oct cell division less useful
• Shooting rays from ground plane takes enormous number of rays to get
accurate calculation
Cases Where Vehicle Effects on Ground
Plane Are Negligible
Ares I-X with Entire Ground Plane
8National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Why to Avoid Rays Shot From Planet
♦With tall/thin vehicle, tremendous number of rays needed to
hit vehicle from planet
♦Shooting rays only from vehicle allows faster, more accurate
calculations
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Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Ares I, I-X Analysis
♦Tall, thin vehicle: little effect on ground
♦Ground temperatures defined, not calculated
♦Hybrid of planetary heating and ground surface plane
methods used
♦Solar flux calculations:• Solar flux and albedo: geo lat/long orbit type with time of day and
location; modeled planet unused
• Diffuse solar flux: radiation from entire sky hemisphere;
modeled planet included for blocking (no rays shot)
♦ IR calculations:• Use modeled planet surface
• Do not shoot rays from planet
• Radiation conductors calculated vehicle-to-planet only
• If planetary IR modeled via orbit, IR heating from planet would be
double book-kept since vehicle radiatively coupled to a 360° spherical “sky radiation” sink temperature
10National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Near-Surface Natural Environments
♦Definition of the surrounding natural environment is an
important factor to consider when performing near-surface
thermal analysis
♦Natural environments include diurnal variation of air
temperature, solar flux, and sky temperature
♦Currently, these data have been obtained for the primary
launch site (Kennedy Space Center, FL) and the testing site
for the Ares I launch abort system (White Sands Missile
Range, NM)
♦Hot and cold diurnal profiles are obtained by calculating the
high (95th or 99th) and low (5th or 1st) percentiles, respectively,
for each hour of the hot and cold months (July and January)
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Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Air Temperature Diurnal Thermal Profile
♦Hot and Cold Diurnal Temperature Profiles for KSC• Red lines represent the 50 hottest and coldest days in the KSC POR
• 95th and 99th profiles are from July
• 5th and 1st profiles are from January
0 2 4 6 8 10 12 14 16 18 20 2222
24
26
28
30
32
34
36
38
Hour of the Day (LST)
Temperature (°C)
0 2 4 6 8 10 12 14 16 18 20 22-10
-5
0
5
10
15
Hour of the Day (LST)
Temperature (°C)
95th P ercentile Day
99th percentile Day
5th P ercentile Day
1s t percentile Day
a) b)
July January
12National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Solar Insolation Data
♦Hot Diurnal Solar Insolation Profile for KSC• Days with high direct incident (a) will be clear, sunny days, therefore
the diffuse (b) will be low
• Cloudy days will have little to no direct incident, and mostly diffuse (not
shown here)
• Red lines represent the 50 highest days of direct incident in July
0 2 4 6 8 10 12 14 16 18 20 220
100
200
300
400
500
600
700
800
900
Hour of the Day (LST)
Direct Incident (W
/m2)
95th P ercentile
0 2 4 6 8 10 12 14 16 18 20 220
100
200
300
400
500
600
700
800
900
Hour of the Day (LST)
Diffuse (W
/m2)
95th P ercentilea) b)
(a) Direct (b) Diffuse
13National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Sky Radiative Sink Diurnal Thermal Profile
♦Hot and Cold Diurnal Sky Temperature Profiles for KSC• Red lines represent the 50 highest and lowest sky temperature days in
the KSC POR
• 95th and 99th profiles are from July
• 5th and 1st profiles are from January
0 2 4 6 8 10 12 14 16 18 20 2220
22
24
26
28
30
32
34
Hour of the Day (LST)
Sky T
emperature (°C)
0 2 4 6 8 10 12 14 16 18 20 22-35
-30
-25
-20
-15
-10
-5
0
5
10
Hour of the Day (LST)
Sky T
emperature (°C)
95th P ercentile Day
99th percentile Day
5th P ercentile Day
1s t percentile Day
a) b)
July January
14National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Parametric Study Method
♦Planet size & relative environmental effects should be
determined early in the analysis process
♦Significantly reduced models can be used for this purpose
♦All environmental loads should be applied to reduced model
15National Aeronautics and Space Administration
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Parametric Study Results
♦ Reduced models can provide relative heat transfer for each mode
♦ Quickly shows which modes are most significant
♦ Quickly shows effects of planet size on the total energy balance
0.24
0.33 0.35
0.36
0.37
0.23
0.32 0.34 0.35
0.35
0.53
0.35
0.30
0.29
0.28
0.00
-0.0
1
-0.0
8
-0.1
0
-0.1
3
-0.9
1
-0.9
5 -0.8
4
-0.8
0
-0.7
7
-0.0
9 -0.0
4
-0.0
8
-0.0
9
-0.1
0
-1.00
-0.80
-0.60
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
1.00
39.8°C 36.4°C 38.1°C 38.5°C 38.9°C
2 20 100 200 1000
Re
lati
ve H
eat
Tra
nsfe
r
Direct Solar Albedo Diffuse Solar Planet IR Sky Rad. Convection
Dp/Dv
Tv
In this example,
sky radiation is
huge factor
In this example,
direct solar,
albedo, diffuse
all of same order
16National Aeronautics and Space Administration
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Parametric Studies
♦Reduced models also helpful for resolving shadow regions
♦Small, light components will be affected differently depending
on shadow resolution
♦ Relative heat transfer plots can also be produced
a.) Low inner region nodalization,
determine effective area
b.) Higher inner region nodalization,
determine effective area
c.) Higher inner region nodalization,
smaller inner area
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Summary
♦This paper describes thermal modeling techniques of ongoing
Constellation projects
♦No current flight or test model correlation of methods• Results verified by hand-calculations and previous modeling methods
♦Constellation thermal engineers plan to correlate using
measured ground data as soon as possible• Pad Abort testing at White Sands, Ares I-X demonstration flight from
KSC, etc.
♦Future refinements and improvement based on ground data
correlations and environmental parameters will be done
♦Natural environment data well-characterized for KSC and
WSMR
♦Parametric studies allow determination of most important
parameters
18National Aeronautics and Space Administration
Thermal & Fluids Analysis Workshop 2008 TFAWS-08-1017
Acknowledgments
♦Ken Kittredge and Mark Wall of Marshall Space Flight Center
for their inputs in developing the ground-based modeling
techniques for Ares I and Ares I-X
♦Technical support from the team at Cullimore & Ring