A strong, square cross-section, central column to which experimental and accessory compartments are attached is described. The attachment may be by direct bolting or through vibration and/or thermal isolators, as needed. Structural and thermal characteristics are evaluated

Punwani, K. G.

English

NASA Technical Reports Server

A VERSATILE STRUCTURE F O R  GAS YArLOAXG 
Kunar 6. Yunwani 
Adjunct A s s i s t a n t  P i ~ f e 5 ~ 0 r  
N C  A % T  S t a t e  U n i v e r s i t y  
Greensboro, NC 27411 
M e c tt a n i c a 1 En 3 i ne er i n g ne p ar t ~ e n t  
ABSTRACT 
This paper  d e s c r i b e s  a s t r u c t u r e ,  and sone of i t s  c h a r a c t e l - i s t i c s ,  
tdhich i s  t o  be used by t h e  ABT S tuden t  Space S h u t t l e  Prografi for 
c a r r y i n g  G A S  e x p e r i ~ e n t s .  The s t r u c t u r e  i s  s u f f i c i e n t l y  ve i - sa t i l e  that .  
o t h e r  GAS e s p e r i m e n t e r s  nay be a b l e  t o  use it. The concept  is eas i ly  
capatl lE o f  being  ex tended  t o  the  5 cu . f t .  c a n n i s t e r .  
, 
DESCRIPTION OF STRUCTURE 
The concept  i s  5 i M p l y  t h a t  o f  a s t r o n g ,  s q u a r e  Ci-.oSS-5ec'tiGn, cerit i ial  
c (1 1 u A n  t o  w h i c h ex per  i n e 11 t a 1 and ac  c e ssor y c o #par t M en t 5 a r e  a t  t a c hecl , 
The a t t a c h n e n t  nay be t ty  d i r e c t  b o l t i n g  or through v i b r a t i o n  anct/or 
thei-fial i s o l a t o r s ,  a5  needed. 
I t  war f e l t  t h a t  ZI hollow 4">:4", I f Z "  wa 1 1 t ti i c kpe s 5 ,  4106 1 - T &  A1 C ~ H  i n ~ i ~  
L a l u m n  would be adequate .  Because Alu#i inun  t u b e s  of t h e s e  diplensions are 
n o t  c o n n e r c i a l  s t o c k  i t e n s ,  i t  was f a b r i c a t e d  i n  t h e  fo l lowing  nanner: 
Four 318" t h i c k  6061-T6 A l u h i n u n  p l a t e s ,  two o f  which a r e  3.35" wide and  
the re f ia in ing  two a r e  3" wide, were slid i n t o  a 9 " ~ 4 " , l f 8 "  wal l  t h i c k -  
iie55, 6063-TS Allminun tube ,  and sean-welded a t  each  end t o  t h e  tube .  
(Chamfer5 Mere n i l l e d  on t h e  p l a t e 5  p r i o r  t o  welding t o  p rov ide  space 
for  t h e  ue ld  n a t e r i a l  t o  e n t e r  and c r e a t e  a strong tIond.1 The ends o f  
!.his ~ o c i p o s i t e  coluliln W E ~ E  H i l l e d  t o  renove excess  weld n a t e r i a l ,  and 
l o  fiak.e i t s  ends a t  r i g h t - a n g l e s  t o  i t s  5ide5.  D e t a i l s  o f  the co1c;m 
a r e  f u r t h e r  e l u c i & t e d  i n  Fi . jure 1 .  There is na r eason  f o r  t h e  c h o i c e  
o f  a d i f f e r e n t  a l l o y  f o r  the o u t e r  tube  o t h e r  than  t h a t  i t  was r e a d i l y  
i w a  i 1 a b  1 e.  
The next  5 t e p  was t o  provide  Means f o r  a t t a c h i n g  t h e  colur-tn t o  NASA'E 
!2tandai7d Experiment t iounting P l a t e  (Ni.IP1 C l l ,  p . 1 9 ,  and C21, i t em ( a ) ,  
Elnd t o  i n c o r p o r a t e  l a t e r - a 1  s u p p o r t s  C21, i t e n  ( h ) .  This was accofiplishec 
I:ty coj i s t ruc t l i ig  two i i i i t i a l l y  i d e n t i c a l  19.75" d i a r t e t e r ,  1 /4"  th ic l , ,  
6061 -T6 A l u m i n u m  p l a t e s ,  with 3 " ~ 3 " ,  13.75" deep,  s t i i b ~  a t  t h e i r  c e n t e r s  
each  f a b r i c a t e d  a5 fo l lows :  A 1 "  t h i c k  bO5l-Tb Alufiinirfi p l a t e  #as 
-127- 
https://ntrs.nasa.gov/search.jsp?R=19840019707 2020-03-22T09:33:52+00:00Z
m i l l e d  down t o  0.25" t h i c k n e s s  l e a v i n g  the s t u b  a t  the c e n t e r .  (The r e a -  
% a n  f o r  this rrethod of manufacture  i s  t h a t  b o l t i n g  o r  welding a s t u b  
a n t o  a 0.25" p l a t e  could ,  i t  was f e l t ,  c r e a t e  s t r e n g t h  protllefis.) The 
r e n a i n i n g  0.25" p l a t e  uas  he ld  through f o u r  h o l e s  on a r o t a r y  t a b l e  and 
t he  edge was n i l l e d  t o  19.75" d i a n e t e r ,  E i g h t  countersunk c l e a r a n c e  
I-mles, two per  s i d e ,  were d r i l l e d  a t  each end o f  t h e  colunn,  cor respond-  
i n g  h o l e s  were d r i l l e d  and tapped  i n  the s t u b s  t o  a c c e p t  T r i d a i r  
I<H420J inserts E31 , and the colunn v a s  secu red  , u s i n g  Unkvako 
1960 series l i 4 - 2 0 x 3 / J 1 ' ,  a l l o y  s t e e l  s o c k e t  head cap  screws 141 , to  -the 
stutts. Dne p l a t e  is in t ended  f o r  a t tachr ren t  t o  N#F, the o t h e r  t o  c a r r y  
l a t e r a l  suppor t s .  ble s h a l l  r e f e r  t o  these,  r e s p e c t i v e l y ,  a s  A & T " s  Toy 
I:'late (ATP) and A8T's Botton P l a t e  ( A B P ) .  T h i s  a s s e n b l y  i s  Skiown i n  
F i g u r e  2 .  
I t  was i n i t i a l l y  f e l t  t h a t  the a t t a c h n e n t  of  ATP t o  NMP should  
i n c o r p o r a t e  t h e r n a l  i s o l a t o r s .  For this purpose twelve  Polypento  Nylon 
'101(6/5) E51 s p a c e r s ,  each  a s  s p e c i f i e d  i n  F i g u r e  3, were f a b r i c a t e d  
a n d  inserted a t  twe lve  l o c a t i o n s  i n  ATP. Twelve Unbrako 1960 s e r i e s  
10 -32~1 .25"  a l l o y  s t e e l  s o c k e t  head c ~ i p  screws  CJI a re  expec ted  t o  be 
a d e q u a t e  t o  hold t h e  corsplete  s t r u c t u r e  and a p p a r a t u s  i t o t a l  4ueigh.t 
at mst 100 1bs.I  t o  NHY dur ing  f l i g h t .  D e t a i l s  of t h e  rrounting o f  ATP 
L o  NHP a r e  shawn i n  F igu re  3. T h i s  Method of noun t iny  c r e a t e s  ail a i r  
space ,  aiid p u t s  Nylon h a r r i e r s  in t h e  h e a t  conduc t ion  pa th  hetween 
ATP and HHP. The e f f i c a c y  of  t h i s  dev ice ,  a s  a t t se rna l  i s o l a t o r ,  will 
B e  connented upon i n  the next  s e c t i o n .  However, the  a i r  gap r e n a i n s  
n e c e s s a r y  t o  pi*event o b s t r u c t i o n  o f  t h e  purge pOi'tS and grounding I:Ioint,s 
un N W .  The foui- h o l e s  i n  ATP w h i c h  were used t o  ho ld  i t  down f o r  
machining purposes  now s e r v e  t o  p rov ide  conven ien t  a c c e s s  t o  NiqP f o r  a 
groundi i ig  s t r a y ,  p lunb ing  f o r  p o s s i b l e  v e n t i n g  o f  b a t t e r i e s ,  ai7d peiv i i t  
pu rg ing .  
The s t r u c t u r e  USES foui' l a t e r a l  5Upj?rJPts, Each iiounted oi l  t o p  of 
ABP w i t h  f o u r  Unbrak.0 1860 s e r i e s  1 0 - 3 ? ~ 7 / 8 "  a l l o y  s t e e l  s o c k e t  head C Z I ~  
s c r ews  C91 , The l o c a t i o n s  o f  t h e  l a t e r a l  s u p p o r t s  a r e  shown i n  F i g u r e  4 ,  
'The d e t a i l s  of a l a t e r a l  suppor t  ai-e shown i n  F igu re  5. I t  c o n s i s t s  o f  
a thi.eaded base  thrGUgh w h i c h  a 1 /2-13 galvai i ized s t e e l  thireaded r o d  
i+Iovez. The rod i s  provided  wi th  a lock  n u t .  One end o f  the rod is 
squa red  t o  a l l o u  t h e  use  o f  a wrench t o  t u r n  i t ;  t h e  o t h e r  end i s  tu rned  
a n d  p r e s s - f i t t e d  i i i t o  the coiie ( p a r t  no. 13203:) O f  a Tifiken tZipei-.ed 
i-oiler hea r ing .  The c u p  i p a r t  no. A2126)  of  t h e  b e a r i n g  is  fiolli-sted i n  
FI Pcilypenco Nylon 101 ( 6 / 6 f  C51 hunper. Bade a iC0rd ing  t o  C21,- its& i h l ,  
The o p e r a t i o n  i s  s i n p l y  t h a t  o f  t u r n i n g  t h e  th readed  ~ o d s  by a wrench 
,Lhrough s lots  i n  ASP u n t i l  t h e  hunyers  pi-ess a g a l n s t  t h e  G A S  cannis te i -  
I d a 1 1 5  as n u c h  a s  dSSi red .  The lock  n u t s  a r e  t i g h t e n e d  t o  p reven t  .the 
' threaded rod f r o n  v i b r a t i n g  loose  d u r i n g  launch.  
The s t r u c t u r e  d e s c r i b e d  above c a n  e a s i l y  tie used i n  t h e  5 cii. f t .  
crai lnis ter  tly coins t ruc t ing  a l onge r  c e n t r a l  colufiii, p o s s i b l y  l f ic i- . ; .easi i iy 
L.he t h i cknes ;  of t h e  Top and Bottom P l a t e ;  ( i n  uhich case  t h e  stu t ls  
r-lay he b o l t e d ) ,  and poss i t t ly  i n c r e a s i n g  the nunher o f  screws holdii ig 
t h e  Top P l a t e  t.o N H P .  
-128- 
CHARACTERISTICS OF STRUCTURE 
This s e c t i o n  coi i ta i i is  a t v i e f  p r e s e n t a t i o n  of  sone  c h a r a c t e r i s t i c s  
o f  t h e  s t r u c t u r e  which a r e  p u b l i s h a b l e  a t  t h i s  tirie. The  c t l a r a c t e r i s t i c s  
m n t i o n e d  below a r e  anong t h o s e  which a r e  r e q u i r e d  t o  be  cons ide red  by 
NASA-NHE 16700.71 C h l  , t h e  a s s o c i a t e d  Gas Payload S a f e t y  Hanual E71 , 
%be GAS Exper i t ien te r  HandlooR C l l  , and A?iT"s own r e q u i r e n e n t s .  
(3 1 S t r u  c t u r  a 1 : 
The f o l l o u i n g  f o r n a t  c o i n c i d e s  with t h a t  i n  the S t r u c t u r e s  Hazarcls 
C h e c k l i s t  of t h e  S a f e t y  Manual E71 , pp.165-169. 
!j t r u c t u  r a 1 An a 1 y s e s 
i -cqui renents  of Appendix A of C71 i s  heyonil the scope  of this paper. 
:Et s u f f i c e s  t o  say  t h a t  our  p r e l i n i n a r y  e s t i a a t e s  trave shown t h a t  a l l  
elements i n  t h e  s t r u c t u r e  a r e  c a p a l l e  of w i ths t and ing  t h e  f l i g h t  l oads  
w i t h  & o r e  than t h e  f iargin of s a f e t y  r equ i r ed .  
a. The p r e s e n t a t i o n  of a d e t a i l e d  s t r e s s  a n a l y s i s  accordi i ig  t o  t h e  
I t  is  of  i i ipor tance  t o  o b t a i n  some insight. i n t o  the v i t s -a t ion  f r e -  
q u e n c i e s  of the s t r u c t u r e  wi thout  any c h a d l e r s  a t t a c h e d  t o  t h e  col?i#n. 
The s t r u c t u r e  will Le e x c i t e d  b y  t h e  no t ion  of NHP. If we r e g a r d  the 
ATP a n d  MMP assenb ly  a5 a r i g i d  tody  t h e  colufin fiay be regarded  as 
a n  e l a s t i c  tody  which i s  claf iped a t  i ts  upper end and a t t a c h e d  t o  aii 
c s l a s t i c  s u p p o r t  i i . e . ,  ABP) a t  i t s  lower end. U t i l i z i n g  t h e  g e n e r a l  
p r i n c i p l e  t h a t  s t i f f e n i n g  a s t r u c t u r e  r a i s e s  i t s  v i b r a t i o n  f r e q u e n c i e s ,  
w e  f i ay  o b t a i n  lowei: hounds t u  t h e  f r e q u e n c i e s  of t h e  colufin Ly i----egardiiiq 
i t  as f r e e  a t  i t s  lower E i l d .  I n  this Manner, W E  f i n d  t h a t  a l l  l o n g i t u -  
d i n a l  vibration f r e q u e n c i e s  a r e  g r e a t e r  t han  
1225 Hz 
a n d  a l i  l a t e r a l  v i t w a t i o n  f r e q u e n c i e s  a r e  grea tk i .  t tmn 
333 Hz 
Tt1es.e v a l u e s  a r e  f a r  i i i  excess  of the rninirrum value 35 Hz s p e c i f i e d  
b y  Appendix A o f  171.  ble t h e r e f o r e  conclude t h a t  t h e  colunn is r i g i d  uith 
i-e5pECt t o  any v i b r a t o r y  e x c i t a t i o n s  t r a n s m i t t e d  b y  NMP. These exc i -  
t a t i o n s  will L E  t r a n s n i t t e d  a l n o s t  u n a l t e r e d  t u  ABP. I t  now t ~ E C o i i E 5  
:iiipairtant t , ~  cu i i s ider  v i t r a t i o n  freqlleiiCie5 of ABF. Eecaiise dBF is 
!supported i n  a c o q l i c a t e d  R Z I ~ ~ W ,  cle nust r e s o r t  t o  t h e  f o l l o u i n g  
kechnique  f o r  t h e i r  de t e r f i i na t ion :  ABP is  c e r t a i n l y  f a r  fiui-e s t i f f  
t h a n  a 19.75" d i a n e t e r ,  0 .25"  t h i c k  A l u d i i i u f i  p l a t e  which i s  clanpelj 
;:it i t s  boulidary, t lecause of  t h e  4 " x 4 "  r eg ion  in ABP which i s  a l s o  
c-lanpeij. The fundafiental  f requency  o f  t h e  forprer p l a t e  is 
34 Hz 
We CoilClUde t h e r e f o r e  t h a t  n e i t h e r  t h e  ColUNil n o r  ABP will i7esoiiFrtE. 
-129- 
b. With  the excep t ion  of  i t e n s  (42 B (31 ,  which a r e  p rocedura l  r e q u i r e -  
ments  which will be fo l lowed  i n  s t r u c t u r a l  a n a l y s e s ,  i t  will tie e a s i l y  
!seen t h a t  a l l  o t h e r  g e n e r a l  p r a c t i c e s  l i s t e d  have been fol lowed.  
S t r u c t u r a l  Ma te r i a l ;  
A t  the t i n e  of w r i t i n g  we have n o t  conv inc ing ly  denons*trated t o  OUIP 
s e l v e s  t h a t  danaging s t r e s s  c o r r o s i o n  c r a c k i n g ,  hydrogen e n b r i t t l e t e n t ,  
or g a l v a n i c  c o r r o s i o n  will no t  occur .  Nor have we checked t h a t  the 
r r a t e r i a l s  have s u f f i c i e n t  f r a c t u r e  toughness  t o  be a b l e  t o  t o l e r a t e  
c r a c k s  of t h o s e  s i z e s  which nay be expec ted .  S t u d i e s  of t h i s  s o r t  will 
t a k e  p l a c e  soon a f t e r  we o b t a i n  docuf ien ta t ion  o f  r e l i a t t l e  reconnended 
p r a c t i c e  such as  NASA-MSFC-SPEC-522A. 
S t r u c t u r a l  Suppor t s  
’These will a l s o  be t aken  i n t o  c o n s i d e r a t i o n  i n  t h e  des ign  of s u p p o r t s  f o r  
t h e  chanbe r s  which a re  t o  be a t tac t red  t o  the colunn.  
I t  will be seen  t h a t  a l l  r e q u i r e n e n t s  of  this s e c t i o n  have been net. 
IC;) Therna l :  
I 
I t  is o f  c o n s i d e r a b l e  i n t e r e s t  t o  know how well t h e  s t r u c t u r e  is  
t .hern,ally i s o l a t e d  f r o n  t h e  c a n n i s t e r .  For this pLli’pOSe, W E  have dune 
sofie c a l c u l a t i o n s  a s sun ing  t h a t  t h e  s t r u c t u r e  and caii i i ist .er  intie? wa l l  
a r e  a t  c o n s t a n t  t e n p e r a t u r e ,  and h e a t  f l ows  tletweei-i then  i n  t h e  fo l lowing  
m d e s : 
i 1 Conduction through Nylon-Cap S c r e w  Assentlly 
i i )  Conduction through Air Gap tietween ATP and NlYP 
i v )  Radia t io i i  f r o #  ATP and AEF ta Caniiistei. liiliec U~dl 
i i i  1 Conductioii thixough La tepa l  SUpp!Ji7ts 
I f  R deno tes  the h e a t  flou r a t e ,  T C  deno tes  c a n n i s t e r  i n n e r  wai l  tekpe-  
r - a t u r e ,  and TS deno tes  s t r u c t u r e  t e q t e i r a t u r e ,  the energy ba lance  equat,ion 
1-eads a s  tielow: 
4 4 
G y  ITS) + 5, (TSj = D f G4 ( T C j  + G i l T C )  
l.rhere t h e  ii’s a r e  c a l c u l a b l e  treat coiidiictances.  
Given t h e  space  a v a i l a b l e  f o r  t i a t t e r y  s t o r a g e ,  ue expec t  t o  be a b l e  
t o  prov ide  a naxifiun va lue  f o r  R of 2.4  w a t t s .  Assufiiiig T C  = -15 ctegrees 
C e n t i g r a d e ,  t h e  above equa t ion  can be so lved  f o r  TS t o  g i v e  
The above c a l c u l a t i o n  i s  an i i lpcrrtant one showing . tha t  wi th  2.9 
m t t s  of power a v a i l a b l e  f o r  h e a t i n g ,  there i s  p r a c t i c a l l y  no t.herr;ial 
1 5 o l a t i o i i  of the  s t r u c t u r e  f rofi t h e  cai inls te iT.  They a r e  p r a c t i c a l l y  Fi t  
t h e  5 a t i ~  tEt ipei~atUre.  U E  do iiijt expec t  t o  tie atale t o  r a i s e  t h e  I:iO!4Ei7 
crva i lah le  f o r  t reat ing t o o  m c h  tieyond 2.4 w a t t s  because of bat-tery space 
u n a v a i l a b i l i t y .  We nay t h e r e f o r e  q u e s t i o n  t h e  n e c e s s s i t y  for t h e  Nylon 
::pacers and use Metal s p a c e r s  i n s t e a d .  I t  i s  a l s o  app?ii-.Eiit t h a t  any 
des  i I- e d t e np e r a t  LI r e c on t r ij 1 of  e ;.: p e r i n e n t a 1 a TI d a c c e s 5 0 i’ y c ha  nbe r S A list 
-1ak.e p l a c e  by i n s u l a t i o n  and h e a t i n g  of t h e  chanbe r s  d i r e c t l y .  
-130- 
REFERENCES 
1. GAS Exper inen te r  Handbook, Sounding Rocket D iv i s ion ,  NASA-GSFC. 
2. Update t o  C 1 3 ,  L E t t E i -  f r o n  C la rke  Prouty ,  Tec tmica l  t i a s o n  O f f i c e r ,  
3. Keense r t s ,  Cata log  No. 200-E, T r i d a i r  I n d u s t r i e s .  
4. Unbrako Socket  Screws Cata log ,  Forn 4085-15M-6/81 SPS, SPS 
Techno 1. og i e s . 
5. Polypenco Nylon Cata log ,  The Polyner  Corpora t ion ,  1975. 
6. NASA-RHB t730.7A, S a f e t y  P o l i c y  and Requ i renen t s  for Payloads  Using 
7 .  GAS Payloads  S a f e t y  nanual ,  NASA-GSFC, Nos. 1983. 
GAS Progran,  S p e c i a l  Payloads  Div i s ion ,  NASA-GSFC. 
t h e  Space T r a n s p o r t a t i o n  Sys ten .  
Acknowledsenent: The a u t h o r  wishes t o  e x p r e s s  h i s  deep ly  f e l t  g r a t i t i i d e  
t o  a l l  t h e  nenbers  o f  t h e  ABT Studen t  Space S h u t t l e  Progran f o r  t h e i r  
c o n t r i b u t i o n  and en thus i a sn .  In p a r t i c u l a r ,  t h e  napies E d w i n  C r a b t r e e  
a n d  Na than ie l  Hines I1 n u s t  be bent ioned  i n  connec t ion  w i t h  the s p e c i f i c  
idork o u t l i n e d  i n  t h i s  paper. 
-131- 
, I--? 
 
-I 
FIGURE 2 
-132- 
. 
FIGURE 3 
FIGURE 5 
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A versatile structure for GAS payloads

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