ground plane and near-surface thermal analysis for nasa ...frank b. leahy and john r. sharp nasa...

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



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.



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)



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



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



♦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



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



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



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)



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


Temperature (°C)

95th P ercentile Day

99th percentile Day

5th P ercentile Day

1s t percentile Day

a) b)

July January



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


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


Diffuse (W

/m2)

95th P ercentilea) b)

(a) Direct (b) Diffuse



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


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


Sky T

emperature (°C)

95th P ercentile Day

99th percentile Day

5th P ercentile Day

1s t percentile Day

a) b)

July January



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



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



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



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



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

ground plane and near-surface thermal analysis for nasa ...frank b. leahy and john r. sharp nasa...

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