Feasibility of movable surface fins for spacecraft temperature contro

Maples, D.

Wiebelt, J. A.

English

NASA Technical Reports Server

https://ntrs.nasa.gov/search.jsp?R=19660006897 2020-03-16T23:12:08+00:00Z
OKLAHOMA STATE UNIVERSITY 
NASA GRANT N s G - 4 5 4  
December, 1965 
. 
PROGRESS REPORT ON NASA NsG-454 FOR 
JUNE 1 TO NOVEMBER 30,  1965 
By J. A .  Wiebelt and 
D .  Maples 
Prepared Under Grant Number NsG-454 by 
School of Mechanical Engineering 
Oklahoma State University 
St i l lwater ,  Oklahoma 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
INTRODUCTION 
T h i s  r e p o r t  i s  t o  cover t h e  p rogres s  on NASA g r a n t  NsG-454 f o r  t h e  s i x  
month pe r iod  from June 1, 1965 t o  November 30,  1965. The g r a n t  purpose was 
t o  examine a n a l y t i c a l l y  and expe r imen ta l ly  t h e  f e a s i b i l i t y  of using movable 
f i n s  on a s u r f a c e  f o r  s p a c e c r a f t  temperature  c o n t r o l .  For t h i s  system, t h e  
geometry proposed i s  shown i n  F igu re  1. 
THERMOSTATIC STRIP .003" THICK \ ;y:!iGHT AND PERPENDICULAR AT LOW T E R REST R I A L  EMITTANCE COATING 
CY 4 = HIGH 
GIFFUSE WHITE 
PAINT 
-y SPECULAR 
I I I METALLIC W A L L  OF 
SPACECRAFT SKIN--/ b,,, 4 HIGH REFLECTANCE 
F i g u r e  1. Temperature Con t ro l  Su r face  
A n a l y t i c a l  work t o  d a t e  was r e p o r t e d  i n  NASA CR-91 (1)" and NASA CR-155 (2)" 
f o r  t h e  s y s t e m  w i t h  f i n s  c o n s t r u c t e d  of b i m e t a l l i c  m a t e r i a l .  A s  a r e s u l t  of t h e  
a n a l y t i c a l  i n fo rma t ion ,  s e v e r a l  experimental  t e s t s  were devised.  The f i r s t  of 
t h e s e  t e s t s  was d e s c r i b e d  i n  t h e  progress  r e p o r t  da t ed  June 1, 1965. I n  t h i s  
t e s t  ser ies  a model w i t h  two-inch f i n s  spaced two inches  a p a r t  was c o n s t r u c t e d .  
T h i s  model was t e s t e d  i n  t h e  space s imula t ion  f a c i l i t y  a t  Goddard S p a c e f l i g h t  
C e n t e r ,  R e s u l t s  of t h e s e  t e s t s  were not  cons ide red  t o  i n d i c a t e  t h a t  t h e  model 
would a c t  a s  a s u i t a b l e  temperature  c o n t r o l  system. T h i s  conc lus ion  was reached 
upon n o t i n g  t h a t  t h e  t h e r m o s t a t i c  f i n s  r e a c t e d  p r i m a r i l y  t o  t h e  s o l a r  i r r a d i a t i o n  
r a t h e r  than t o  t h e  s p a c e c r a f t  s k i n  m a t e r i a l .  
A f t e r  t h e  i n i t i a l  s e r i e s  of t e s t s  were concluded i t  was decided t h a t  f u r t h e r  
t e s t i n g  shou la  be c a r r i e d  on a t  Oklahoma S t a t e  U n i v e r s i t y  i n  a small  space 
s i m u l a t o r  t o  be c o n s t r u c t e d  from miscel laneous s u r p l u s  equipment. T h i s  s i x  
mQnth p e r i o d , h a s  been p r i m a r i l y  involved i n  t h e  c o n s t r u c t i o n  of the  s i m u l a t o r  
vacuum system, c o l d  w a l l  l i n e r ,  and t e s t  f i x t u r e s .  Also a modified f i n  system . 
Jr 
Numbers i n  p a r e n t h e s i s  r e f e r  t o  r e f e r e n c e s  a t  t h e  end of t h e  r e p o r t .  
was devised i n  an  at tempt  t o  avoid the u n d e s i r a b l e  coup l ing  of f i n  movement 
t o  s o l a r  i r r a d i a t i o n .  Th i s  system was t e s t e d  i n  a c o l d  w a l l  t e s t  which w i l l  
be desc r ibed .  
Space Simulat ion System Cons t ruc t ion  
A small  space s imula to r  was c o n s t r u c t e d  us ing  s u r p l u s  equipment from s e v e r a l  
sou rces .  The b a s i c  c o n t a i n e r  was a s t a i n l e s s  s t e e l  chamber 24 i nches  i n  diameter  
and 48 i nches  long. A l i q u i d  n i t rogen  coo led  l i n e r  18 i n c h e s  i n  diameter and 27  
inches  long was mounted i n s i d e  t h e  s t a i n l e s s  chamber. Two views of t h e  chamber 
and t h e  l i n e r  a r e  shown i n  F i g u r e s  2 and 3 .  The chamber i s  evacuated us ing  one 
s i x - i n c h  o i l  d i f f u s i o n  pump w i t h  a l o w  t empera tu re  b a f f l e .  A s  can be seen  i n  
t h e  photographs,  a s i x - i n c h  f l a n g e d  window p o r t  was provided on t h e  f r o n t  of 
t h e  chamber. 
T h i s  chamber was assembled and l eak  checked du r ing  t h e  i n i t i a l  p o r t i o n  o f  
t h e  s i x  month pe r iod .  I n  i t s  p re sen t  c o n f i g u r a t i o n  t h e  chamber may be opened 
and c l o s e d  and w i l l  r e g u l a r l y  pump down t o  t h e  10-5 t o r r  range w i t h  no n i t r o g e n  
c o o l i n g .  With l i q u i d  n i t r o g e n  coo l ing ,  t h e  t y p i c a l  chamber p r e s s u r e  i s  i n  t h e  
10-7 t o r r  r ange .  
A General  E l e c t r i c  t y p e  151 s ix - inch  q u a r t z  window i s  a v a i l a b l e  t o  f i t  t h e  
s i x - i n c h  f l anged  opening on t h e  f r o n t  of t h e  chamber. T h i s  window i s  f o r  t h e  
s o l a r  s imula to r  beam. S o l a r  i r r a d i a t i o n  w i l l  be  s imula t ed  w i t h  e i t h e r  a 2 . 5  
KW Hanovia Xenon a r c  lamp system o r  two l a r g e  carbon a rc  lamps. A t  t h e  p r e s e n t  
t ime,  t h e  Xenon a r c  i s  be ing  considered because of t h e  c l e a n l i n e s s  and ease  o f  
o p e r a t i o n .  T h i s  s o l a r  s imula t ion  system w i l l  be  d e l i v e r e d  f o r  u se  on two 
r e s e a r c h  p r o j e c t s .  It i s  a n t i c i p a t e d  t h a t  t h e  system w i l l  be  a v a i l a b l e  f o r  
t e s t i n g  about 50% of  t h e  time. I n  t h e  use of t h e  Xenon a r c  lamp system, u l t r a -  
v i o l e t  s i m u l a t i o n  w i l l  be  accomplished. T h i s  w i l l  r e q u i r e  ex t ra  c a r e  i n  t h e  
s e l e c t i o n  of material  f o r  t h e  temperature  c o n t r o l  systems. 
Modified Temperature Con t ro l  System 
A s  i n d i c a t e d  i n  t h e  i n t r o d u c t i o n ,  t h e  t h e r m o s t a t i c  f i n  system as  o r i g i n a l l y  
conceived appea r s  t o  r e a c t  unfavorably i n  t h e  presence of s o l a r  i r r a d i a t i o n ,  An 
a t t e m p t  t o  avo id  t h i s  problem which i s  being cons ide red  i s  shown i n  F i g u r e  4 .  S i n c e  
t h i s  photograph does no t  show t h e  d e t a i l s  of t h e  f i n  system a d e s c r i p t i v e  drawing 
i s  shown i n  F igu re  5. A s  shown i n  Figure 5 ,  t h e  t h e r m o s t a t i c  m a t e r i a l  was connected 
t o  t h e  base  m a t e r i a l  w i t h  a l a r g e r  a rea  of c o n t a c t  and t h e  upper p o r t i o n s  of t h e  
f i n s  were made of a poor thermal conductor.  The purpose of t h i s  system was t o  
r educe  t h e  h e a t i n g  e f f e c t  of t h e  s o l a r  environment.  
For  t e s t i n g  purposes ,  t h e s e  fins were made w i t h  a two-inch h e i g h t  and one- 
i n c h  spac ing ,  T h i s  f i n  system would have a l a r g e r  s o l a r  abso rp tance  i n  t h e  grooves 
due t o  t h e  geometry, bu t  i t  was be l i eved  t h a t  t h e  g r e a t e r  a c t i v i t y  ga ined  by t h e  
i n c r e a s e d  l e n g t h  was advantageous.  
T h i s  c o n t r o l  system was mounted over a h e a t e r  and i n s u l a t e d  w i t h  m u l t i - l a y e r e d  
aluminum i n s u l a t i o n  a s  shown in Figure 6. A c o l d  w a l l  t e s t  of t h e  f i n  system was 
2 
1 Figure 2 .  V i e w  I of S m a l l  Space Simulator 
Figure 3 .  Viet? I1 of Small Space Simulator 
3 
F i g u r e  4 .  Modified Fin System (Photograph) 
F i g u r e  5 .  Modified F i n  System ( P i c t o r i a l )  
4 
F i g u r e  6 .  F i n s  i n  T e s t  F i x t u r e , '  
r u n  w i t h  v e r y  u n r e l i a b l e  r e s u l t s .  A f t e r  t h e  complet ion of t h e  t e s t ,  examinat ion 
of t h e  t e s t  system showed a complete cover ing  of  t h e  system w i t h  o i l .  T h i s  o i l  
was determined t o  have come from a G l y p t a l  p a i n t e d  h e a t e r  e lement .  
A secondary r e s u l t  o f  t h i s  t e s t  was t h e  o b s e r v a t i o n  t h a t  energy l o s s  from 
t h e  i n s u l a t i o n  c o u l d  n o t  be p r e d i c t e d .  
a t e s t  i n s u l a t i o n  system was devised .  T h i s  c o n s i s t e d  o f  n i n e  l a y e r s  of  aluminum 
f o i l  w i t h  a porous  c l o t h  spacer  between each l a y c r .  Two s e p a r a t e  i d e n t i c a l  h a l v e s  
were b u i l t  w i t h  i n n e r  dimensions of 3 inches  by 6 i n c h e s  by 6 inches .  These t w o  
h a l v e s  were sandwiched over a n  improved h e a t e r  and s u i t a b l y  ins t rumented  w i t h  
thermocouples .  A schematic  of t h e  system used a long  w i t h  thermocouple l o c a t i o n s  
is  shown i n  F i g u r e  7. 
While o t h e r  models were be ing  prepared ,  
S i n c e  t h e  measured p r o p e r t i e s  wcre n o t  expec ted  t o  be r? f u n c t i o n  of t h e  
t e m p e r a t u r e ,  t e s t s  were made w i t h  t h e  c o l d  w a l l  l i n e r  z t  room tempera ture .  The 
da t a  o b t a i n e d  from t h e s e  r u n s  i s  shown i n  Table  I. T h i s  d z t a  was ana lyzed  on 
t h e  b a s i s  t h a t  t h e  h e a t e r  element was i s o l a t e d  by t h e  i n s u l a t i o n  box from t h e  
c o l d  w a l l  e n c l o s u r e .  I n  a s i m p l i f i e d  manner, t h i s  would r e s u l t  i n  energy l o s s  
from t h e  h e a t e r  a s  shown i n  t h e  s k e t c h  of F i g u r e  8. 
For a n a l y s i s  purposes ,  t h e  energy l e a v i n g  t h e  h e a t e r  could be c o n s i d e r e d  a s  
b e i n g  t r a n s p o r t e d  by r a d i a t i o n .  T h i s  energy would b e  t r a n s p o r t e d  from t h e  h e a t e r  
s u r f a c e s  a t  TI t o  t h e  i n n e r  w s l l  n t  T2, t h e n  through t h e  m u l t i l a y e r  s h i e l d  t o  T3, 
and f i n a l l y  from t h e  o u t e r  s h i e l d  s u r f a c e  t o  t h e  c o l d  w a l l s  2.t T 4 .  Consider ing  
5 
\ 
0 a 
m 
\ 
1 
E 
(u 
6 
c 
. .TABLE I 
INSULATION BOX TEST DATA 
I 
Run No. P r e s s u r e  Power Inpu t  Temperatures i n  O F  
Torr  Watts . 1  ‘ 2  3 4 5 6 7 8 9  
1 4 0.765 150 153 163 88 162.5 148 87 87 78 , 
2 95 1 . 1 2  98 100 117 89 117 98.5 88 .5  87.5 79 
3 80 x 2.55 168 177 230 123 229 170 1 2 1  115 79 
4 82  1.10 94 96 113 84 112 94 84 83 74 
5 4 . 4  1.10 202 205 215 101 215 200 96 95 79 
6 3.2 0 . 7 7 7  184 186 194 98 193 182 94 93 80 
7 2 .5  x 0.578 . 158 159 166 92 166 156 88 88 79 
COLD WALL 
\ MULTILAYER SHIELD /- 
HEATER 
Figure  8. Sketch of I n s u l a t i o n  Box f o r  Analys is  
COLD WALL 
t h e s e  energy f lows by r a d i a t i o n  t h e  fo l lowing  equa t ions  can be w r i t t e n .  
4 4 4 4 4 4 
Q (TI - T2 = K23 c (T2 - T3 = K34 (T3 - T 4  = K12 
7 
c 
I n  t h i s  expres s ion  K 1 2 ,  K 2 3 ,  and K34 s h o u l d  not be s t r o n g  f u n c t i o n s  of t h e  
temperatures .  Using on ly  d a t a  from runs 5 ,  6 ,  and 7 t h e s e  v a l u e s  were 
c a l c u l a t e d .  (Runs 1 through 4 were not used because of e x c e s s i v e  pressure 
i n  t h e  vacuum chamber). The r e s u l t s  of t h e  c a l c u l a t i o n s  a r e  t a b u l a t e d  i n  
Tab le  11. 
TABLE I1 
INSULATION BOX TEST RESULTS 
Max % Devia t ion  
From Mean Value 
Run No. K 1 2  K2 3 K34 
5 0.128 0.02305 0.1954 8% 
6 0 .138  0.02015 0.1682 
7 0.1322 0.0212 0.180 
7% 
1% 
A s  can  be seen t h e  i n s u l a t i o n  t e s t  was v e r y  s u c c e s s f u l  and r e s u l t e d  i n  a 
t e s t  f i x t u r e  f o r  which t h e  energy  flows cou ld  be c a l c u l a t e d  w i t h  e r r o r s  l e s s  
than 10%. T h i s  accuracy  i s  s a t i s f a c t o r y  s i n c e  a m a j o r i t y  of t h e  energy inpu t  
t o  tes t  models w i l l  go through t h e  c o n t r o l  s u r f a c e  r a t h e r  t h a n  tprough t h e  
i n s u l a t i o n ,  
Cold Wall T e s t  of Thermosta t ic  F i n  System 
After t h e  i n s u l a t i o n  box was prepared  and t e s t e d ,  a f i n  system wi th  two-inch 
f i n s  on two-inch spac ing  w i t h  "as received ' '  f i n  s u r f a c e s  was p repa red .  
was s i x - i n c h e s  squa re  a s  compared to a p rev ious  one f o o t  square model t e s t e d  a t  
Goddard S p a c e f l i g h t  Cen te r ,  
vacuum chamber and w i l l  be t e s t e d  f o r  e f f e c t i v e  emi t t ance  wi th  c o l d  w a l l s .  It 
i s  a n t i c i p a t e d  t h a t  t h e s e  t e s t s  w i l l  i n d i c a t e  t h e  a d v i s a b i l i t y  of c o n t i n u i n g  any 
two-inch t h e r m o s t a t i c  f i n  system tes ts .  It i s  conce ivable  t h a t  such a system 
might b e  of v a l u e  for tempera ture  c o n t r o l  on s p a c e c r a f t  wh ich ' a re  o r i e n t e d  i n  
space  r e l a t i v e  t o  t h e  sun. T h i s  t ype  c o n t r o l  i s  s i m i l a r  t o  t h e  p r e s e n t  louver  
systems i n  use on t h e  Mariner s p a c e c r a f t .  
T h i s  model 
A t  t h e  p re sen t  t ime t h i s  model i s  mounted i n  t h e  
A second t h e r m o s t a t i c  f i n  model w i th  one-inch f i n s  and one-inch spac ing  is 
be ing  p repa red .  
p a i n t  base .  A s i x - i n c h  square model w i l l  be prepared  and w i l l  be t e s t e d  fo r  
e f f e c t i v e  emi t t ance  a s  a f u n c t i o n  of base tempera ture  and s o l a r  abso rp tance .  
T h i s  w i l l  be c a r r i e d  out  i n  s e p a r a t e  t e s t s ,  f i r s t  w i t h  no s o l a r  i r r a d i a t i o n  and 
t h e n  w i t h  s o l a r  i r r a d i a t i o n .  These t e s t s  should r e s u l t  i n  cu rves  of e f f e c t i v e  
s o l a r  abso rp tance  and e f f e c t i v e  emi t tance  a s  a f u n c t i o n  of base  tempera ture .  
T h i s  model w i l l  have a luminized  f i n s  wi th  a Dow Corning whi te  
8 
Proposed Fu tu re  Work 
. 
Since  most of t h e  t e s t s - w h i c h  have been run  wi th  t h e  f i n  system c o n s t r u c t e d  
of b i m e t a l l i c  m a t e r i a l  have been u n s a t i s f a c t o r y ,  i t  i s  proposed t h a t  a s e t  of 
models be cons t ruc t ed  wi th  immovable f i n s .  These models would haye f i n s  of one- 
inch  he igh t  on one-inch spac ing  over a s i x - i n c h  square model. With p lane  f i n s  i n  
known p o s i t i o n s ,  t h e  e f f e c t i v e  emit tance and e f f e c t i v e  absorp tance  can be measured 
wi thout  t h e  unknown a c t i o n  of t h e  b i m e t a l l i c  f i n  e lements .  I f  t h e s e  f i n s  show 
c h a r a c t e r i s t i c s  which a r e  d e s i r a b l e  f o r  a temQerature c o n t r o l  system, t h e  method 
of moving t h e  f i n s  could  be redesigned.  That i s ,  i t  i s  proposed t h a t  t h e  e x p e r i -  
mental  model be cons t ruc t ed  t o  ag ree  wi th  t h e  a n a l y t i c a l  model. 
S e v e r a l  of t h e  r i g i d  f i n  models w i l l  be cons t ruc t ed  and t e s t e d  f o r  t h e  important  
parameters ,  These models w i l l  have f i n  p o s i t i o n s  vary ing  from completely c l o s e d  
t o  completely open p o s i t i o n s .  I n  order t o  approximate t h e  a n a l y t i c a l  model, t h e  
f i n s  w i l l  be  a luminized po l i shed  m a t e r i a l ,  probably p l a s t i c s .  
w i l l  be  used on t h e  base  m a t e r i a l .  
A good whi te  p a i n t  
These models a r e  p r e s e n t l y  being designed.  
Another item t o  be at tempted during t h e  next  six-month pe r iod  w i l l  be  c o a t i n g  
A m e t h l y - s i l i c a t e  base  Dow Corning of t h e r m o s t a t i c  f i n  m a t e r i a l  w i th  white  p a i n t .  
p a i n t  w i l l  be  used a s  t h e  t e s t  p a i n t .  
p o s s i b i l i t y  of decoupl ing t h e  f i n s  from t h e  s o l a r  i r r a d i a t i o n  i n  t h i s  manner. 
T h i s  i s  be ing  cons idered  because of t h e  
These tes ts  p l u s  t h e  i n s t a l l a t i o n  and c a l i b r a t i o n  of t h e  s o l a r  s imula to r  
w i l l  be  t h e  g o a l s  of t h e  r e s e a r c h  e f f o r t .  
References 
1. Wiebel t ,  J .  A , ,  and J. F. Parmer, "Spacecraf t  Temperature Con t ro l  by Thermo- 
s t a t i c  Fins-Analysis" ,  NASA CR-91, August,  1964. 
, 
6 
2 .  Wiebel t ,  J A , ,  J. F. Parmer and G .  J. K n e i s s l ,  "Spacecraf t  Temperature 
Con t ro l  by Thermosta t ic  Fins-Analysis  P a r t  XI ,I' NASA CR-155, January ,  
1965. 
9 


Spacecraft temperature control by thermostatic fins Progress report, 1 Jun. - 30 Nov. 1965

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