Extended boom devices for orbital maintenance and safety of space shuttl

Warren, H. R.

English

NASA Technical Reports Server

USE OF EXTENDIBLE BOOM DEVICES FOR SPACE SHUTTLE AND EVA OPERATIONS 
H. Robert Warren 
Spar Aerospace Products Ltd. 
Toronto, Canada 
1.0 INTRODUCTION 
The purpose of t h i s  paper  i s  t o  g i v e  a " s t a t e -o f - the -a r t "  
review on a p a r t i c u l a r  dev ice  t h a t  could have w i d e  a p p l i c a t i o n  i n  
o r b i t a l  maintenance and s a f e t y  a c t i v i t i e s  on t h e  space s h u t t l e .  
This  i s  t h e  e x t e n d i b l e  boom dev ice  f o r  which w e  use t h e  g e n e r a l  
t e r m  of STEM ( S t o r a b l e  Tubular Extendib le  Member). 
The STEM p r i n c i p a l  w a s  f i r s t  invented  i n  t h e  Nat iona l  
Research Council  j u s t  a f t e r  World War I1 and i n  1959 w a s  adapted 
by Spar ( a t  t h a t  t i m e  t h e  SPAR Div i s ion  of The de Havi l land  A i r -  
c r a f t  of  Canada) f o r  t h e  1 5 0 f t .  sounding antennas on t h e  Aloue t t e  
I ionospher ic  r e sea rch  sa te l l i t e .  
S ince  then  over  350 of  t h e  u n i t s  have flown s u c c e s s f u l l y  
on r o c k e t s  and satel l i tes  f o r  a v a r i e t y  of  a p p l i c a t i o n s ,  some of 
which w i l l  be desc r ibed  i n  t h i s  paper .  By showing t h e  v a r i e d  uses  
t o  which t h e  basic p r i n c i p l e  has  been p u t ,  it is  hoped t o  i l l u s t r a t e  
t h e  s p e c i a l i z e d  des ign  techniques  t h a t  have been developed and t h e  
e x t e n t  of f l i g h t  exper ience  gained t o  d a t e .  
The p r i n c i p l e  of o p e r a t i o n  f o r  t h e  STEM i s  shown i n  F igure  
1. During launch t h e  material, i n  t h e  form of  a f l a t  s t r i p ,  i s  
wound on a s t o r a g e  drum. I n  o r b i t ,  t h e  drum i s  r o t a t e d  so t h a t  t h e  
r e s i l i e n t  s p r i n g  m a t e r i a l  forms i n t o  a t u b u l a r  shape of  h igh  
s t r e n g t h .  To i n c r e a s e  t h e  s t r e n g t h  and reduce packaging s i z e ,  t h e  
BI-STEM p r i n c i p l e  i n  F igu res  2 and 3 has  a l s o  been developed. With 
e i t h e r  t ype ,  t h e  d r i v e  arrangement can be motorized,  i f  p a r t i a l  ex- 
t e n s i o n  o r  r e t r a c t i o n  i s  r e q u i r e d ,  o r ,  us ing  t h e  s p r i n g  energy of 
t h e  element material, ex tens ion  can be achieved by simply r e l e a s i n g  
t h e  t i p  of t h e  u n i t .  
I n  Sec t ion  2.0 i l l u s t r a t i o n s  a r e  g iven  of STEM u n i t s  t h a t  
have a l r eady  been developed and have e i t h e r  flown, or  been q u a l i f i e d  
f o r  f l k g h t .  Sec t ion  3.0 reviews c u r r e n t  and f u t u r e  developments 
which have more d i r e c t  r e l evance  t o  t h e  space s h u t t l e  program. 
ist ics t h a t  are a v a i l a b l e  t o  t h e  des igne r  f o r  f u t u r e  space s h u t t l e  
a p p l i c a t i o n s .  
2.0 STEM U N I T S  DEVELOPED PAST PROGRAMS 
Sec t ion  4 .0  provides  a b r i e f  summary of des ign  c h a r a c t e r -  
The boom u n i t s  desc r ibed  h e r e  i l l u s t r a t e  t h e  s ta te -of - the-  
a r t  i n  t h e  t i m e  p e r i o d  1960-1969. 
The f i g u r e s  are grouped accord ing  t o  func t ion .  F igures  4 
t o  1 0  are a c t u a t o r s .  F igures  11 & 1 2  show an antenna. F igure  1 3  
i l l u s t r a t e s  a docking a p p l i c a t i o n  and Figures  1 4  and 15 are a s t r o -  
nau t  'a ids .  
103 
https://ntrs.nasa.gov/search.jsp?R=19700030293 2020-03-11T22:48:13+00:00Z
Fig. 1. The STEM principle 
I ELEMENT I 
\ LELEMENT~ A 4  
I 
Fig. 2 The BI-STEM principle 
Jr.---d--+ 
SECTION A-A 
Fig. 
STORAGE SPOOL 
3. BI -STEM dimensions 
104 
T h i s  u n i t ,  termed a TELE-STEM, w a s  used t o  ex tend  t h e  
r a d a r  t ransponder  on the  Agena Ta rge t  Docking Vehic le .  
t o  a te lephone  cord .  A s  t he  boom w a s  r e q u i r e d  t o  wi ths t and  the  
bendins  l o a d s  r e s u l t i n s  from restart of t h e  Asena e n s i n e ,  it w a s  
Cable deployment w a s  a r ranged  by an  e x t e r n a l  c o i l  s imilar  
des igned  wi th  a system-of c lose- f  i t t i n g  t e l e s c o p i n g  
r e s i s t e d  t h e  bending moment wh i l e  t h e  STEM provided 
f o r c e  . 
cubes which 
t h e  a c t u a t i o n  
105 

Gemini 6 i s  shown i n  o r b i t  i n  t h i s  f i g u r e ,  w i th  a STEM 
boom a t  t h e  base  ex tending  a t h r e e - a x i s  magnetometer. 
I n  t h i s  case, cable deployment f o r  t h e  in s t rumen t  l e a d s  
i s  achieved by a f l a t  conductor  cab le  which f eeds  up t h e  c e n t r e  
of t h e  STEM element.  
A des ign  f e a t u r e  which has  been developed f o r  i n s t rumen t  
a p p l i c a t i o n s  such as t h i s  is an i n t e r l o c k e d  element which pro- 
v ided  g r e a t l y  i n c r e a s e d  t o r s i o n a l  r i g i d i t y .  This  i s  o f t e n  re- 
q u i r e d  i f  t h e  in s t rumen t  must be o r i e n t e d  i n  a p a r t i c u l a r  d i r e c t i o n .  
f 07 
A view of t he  A-26 magnetometer boom w i t h  t h e  cover 
removed shows t h e  system used t o  feed  t h e  26 element f l a t  con- 
duc to r  cable i n t o  t h e  c e n t e r  of t h e  STEM. A s p e c i a l  in te rchange  
chamber is used t o  enable  t h e  c a b l e  t o  be rewound a s  t h e  element 
i s  r e t r a c t e d  wi thou t  r ecour se  t o  s l i p  r i n g s .  
108 
A ground a p p l i c a t i o n  shown he re  i s  a u n i t  designed t o  
enab le  a camera and l i g h t  u n i t  t o  be f ed  i n t o  t h e  c a v i t y  of a 
l a r g e  s o l i d  f u e l  r o c k e t  t o  i n s p e c t  f o r  c r acks  i n  t h e  g r a i n .  
The STEM element i s  maintained i n  a f l a t  form as it 
passes  through a series of  a r t i c u l a t e d  l i n k s  which enab le  t h e  
u n i t  t o  be f ed  up p a s t  s e v e r a l  co rne r s  b e f o r e  e n t e r i n g  t h e  pro- 
p e l l a n t  chamber. 
i n s p e c t i o n  head, could be u s e f u l  t o  i n s p e c t  i n a c c e s s i b l e  areas 
i n  t h e  wings or f u s e l a g e  of  t h e  space s h u t t l e .  
Such a dev ice ,  p o s s i b l y  combined wi th  a f i b r e  o p t i c s  
109 
An example of the extension of a large diameter STEM boom 
is shown here with a 3.12 inch ground mast supporting a large 
tip mass. 
The bending moment and compressive loads generated in such 
a ground environment are similar to those which could arise in 
a space shuttle cargo transfer operation. 
110 
An important current application is the use of booms to 
extend flexible solar cell panels. 
Here four BI-STEMS, 0.86 in. in diameter, are extended 
in synchronism to deploy a pair of Hughes roller type solar cell 
panels. 
An alternative arrangement is with a single central boom 
flanked by two panels which are attached to a tip mounted tee-bar. 
Such designs require the boom to withstand compressive 
loads both during and after the extension so that the panel is 
kept in tension. 
111 
I n  t h i s  view o f  t h e  recovery o p e r a t i o n  of  one of t h e  
Gemini c a p s u l e s l  t h e  HF recovery antenna can be seen  extended 
from t h e  s p a c e c r a f t .  A s i m i l a r  u n i t  w a s  used f o r  o r b i t a l  H F  
communications. 
The whipping a c t i o n  caused by heavy sea s ta te  c o n d i t i o n s  
r e q u i r e d  t h e  use  of a n e s t i n g  technique  wi th  8 s e p a r a t e  e lements  
i n s i d e  one ano the r  a t  t h e  r o o t  of t h e  antenna.  
At t h e  base of t h e  antenna t h e  wh i t e  s i l i c o n e  guard 
s l e e v e  can be seen .  Th i s  prevented  t h e  i n g r e s s  of  sea water t o  
t h e  i n s i d e  of t h e  uni t .  
112 
The HF an tenna  used for Gemini recovery o p e r a t i o n  i s  
shown i n  t h i s  view. 
113 
E a r l y  i n  t h e  Gemini program, a s o f t  docking procedure 
w a s  eva lua ted .  For t h i s ,  t h e  two s p a c e c r a f t  ma in ta in  format ion  
wh i l e  a g r a p p l i n g  boom ex tends  i n t o  a r e c e i v i n g  cone. A f t e r  t h e  
t i p  of t h e  boom i s  secured  i n  t h e  cone, t h e  boom i s  r e t r a c t e d ,  
t h u s  b r i n g i n g  t h e  two v e h i c l e s  t o g e t h e r .  
Although t h i s  approach w a s  abandoned f o r  Gemini i n  favour  
of  a hard docking procedure,  i t s  f e a s i b i l i t y  w a s  demonstrated 
w i t h  dynamic tests conducted a t  NASA/MSC us ing  space frames on a 
l a r g e  a i r  b e a r i n g  t a b l e  t o  s imula t e  t h e  f u l l  scale v e h i c l e s .  
114 
An example of  an a s t r o n a u t  a id  i s  t h e  back pack u n i t  
developed f o r  t h e  U.S. A i r  Force.  Three STEM u n i t s  wi th  s p e c i a l  
end f i t t i n g s  are used t o  enab le  an a s t r o n a u t  t o  secu re  himself  
a t  an e x t e r n a l  l o c a t i o n  on a s p a c e c r a f t .  I n  t h i s  way, t o rque  
r e a c t i o n s  from a maintenance t a s k  can be t r a n s f e r r e d  t o  t h e  space- 
c r a f t .  
The c o n t r o l  pack enab le s  t h e  t h r e e  booms t o  be a c t u a t e d  
e i t h e r  i n  unison or i n d i v i d u a l l y .  
115 
A second a s t r o n a u t  t o o l  is t h e  E x t r a  Vehicular  C r e w  
T r a n s f e r  (EVCT) dev ice  shown he re .  Used wi th  a p i s t o l  g r i p ,  
it enab les  t h e  a s t r o n a u t  t o  ex tend  t h e  boom up t o  25 f e e t  and 
g rapp le  o n t o  a b a r  on an a d j a c e n t  s p a c e c r a f t .  
personnel  t r a n s f e r  between two v e h i c l e s  even i f  t h e r e  i s  a 
f a i l u r e  i n  t h e  docking system. 
I n  t h i s  way, he has  an emergency procedure t o  permi t  
116 
3.0 STEM UNITS FOR CURRENT AND FUTURE PROGRAMS 
The next series of figures shows the present status of 
Figures 16 to 19 show actuation applications, Figures 20 
boom technology and touches on future applications envisaged. 
to 23 described a novel approach to in-orbit manufacture of a 
space structure, and Figure 24 is a space shuttle application. 
The unit shown here is a 2 inch steel BI-STEM originally 
designed for a ground application but converted to serve as a 
25 foot instrument boom on the Apollo J missions. 
Using two such units, it is planned to extend a mass 
spectrometer and a gamma ray spectrometer laterally from the 
service module while the Apollo is in orbit around the moon. 
The elements are silver plated to minimize thermal bending 
and made of extra-thickness maraging steel to withstand manoeuver- 
ing loads as the spacecraft maintains its attitude. 
carefully studied in such cases to assess the binding loads in the 
boom and the probable tip deflection. 
The dynamics of the combined boom and spacecraft must be 
117 
An artist's impression of an actuating boom performing 
grappling functions on the lunar surface is shown here. 
Such a device is now being developed for the Viking 
Soil Sampler experiment where unusual environmental conditions 
of wind, and blowing sand are combined with digging loads from 
the sampler's operation. Prior to this, the unit must also 
survive pre-launch sterilization and the hard vacuum of the long 
interplanetary voyage. 
118 
One of t h e  major t a s k s  f o r  t h e  a s t r o n a u t s  on t h e  AAP o r  
Skylab p r o j e c t  i s  t o  t r a n s f e r  f i l m  packs and cameras from t h e  
a i r l o c k  o u t  t o  t h e  work s t a t i o n s  on t h e  Apollo Telescope Mount 
(ATM) . 
A p r e f e r r e d  approach f o r  t h i s  i s  t h e  use of a 2.0 i nch  
BI-STEM hard mounted near  t h e  ha t ch  of t h e  a i r l o c k .  With one 
a s t r o n a u t  i n  t h i s  l o c a t i o n  t o  load  t h e  f i l m  packs on t h e  end of 
t h e  boom and a second a s t r o n a u t  a t  t h e  ATM work s t a t i o n ,  t h e  
unexposed f i l m  can be passed o u t  and t h e  exposed f i l m  r e t u r n e d  
t o  t h e  workshop. 
AAP CLUSTER 
a 
LUNAR MODULE/).. _ _ _ _  
TELESCOPE MOUNT /!- 
INSTRUMENTATION UGT ARRAY PANELS 
ADAPTER SECFION 
h 
Feasibility of the Skylab film transfer activity has been 
demonstrated by rehearsals on the full scale mock-up in the large 
neutral buoyancy water tank at NASA/ESSFC. 
In this photograph the first astronaut is shown at the 
airlock location guiding the boom down to the ATM lower work 
station. 
120 
The STEM FA3 tool shown here embodies a 105ft. element in 
a replaceable cassette with a guillotine fitting to cutt off pre- 
determined lengths of element. These can then be assembled into 
spaceframes of various configurations as required. 
12 1 
An example of spaceframe formed with the STEM FAB 
approach is shown in this photograph. In this case, the 
frame was strong enough to be scaled by a 200 lb. man. 
122 
A unique f o r m  of s e l f - l o c k i n g  co rne r  j o i n t  s u i t a b l e  f o r  
t r i a n g u l a t e d  s t r u c t u r e s  i s  shown he re .  The a s t r o n a u t  needs only  
t o  i n s e r t  t h e  end of t h e  STEM element and a pre loaded  lock ing  
s p r i n g  i s  t r i p p e d  clamping t h e  element onto  a c e n t r a l  co re .  
STEM Tube Before Jnrertion 
123 
An artist's impression of a large dish antenna structure 
formed from such triangulated components is shown here. 
124 
Perhaps t h e  most obvious a p p l i c a t i o n  f o r  a c t u a t o r  booms 
on t h e  space  s h u t t l e  i s  t h e  ca rgo  t r a n s f e r  f u n c t i o n ,  
Th i s  view shows such an arrangement wi th  a system o f  
booms be ing  used t o  t r a n s f e r  a f u e l  tank  i n t o  t h e  n u c l e a r  s h u t t l e  
as conceived by Lockheed Missiles and Space Corpora t ion ,  
requirement  h e r e  and c o n s i d e r a t i o n  must also be g iven  t o  t echn iques  
for r e s i s t i n g  bending l o a d s  i n  t h e  e v e n t  of la teral  motion of t h e  
cargo.  
Synchroniza t ion  of t h e  boom e x t e n s i o n  rates is a d e s i g n  
12 5 
4 .O CONCLUSIONS 
With the need for equipment in the space shuttle to be re- 
liable, of light weight and basically simple, STEM units can be 
used for a number of orbital applications and offer the benefit of 
extensive flight experience. 
The designer has a wide range of characteristics to choose 
from in meeting particular requirements. Some of these are as 
follows : 
Bending strength and stiffness 
Torsional strength and stiffness 
Compressive strength 
Thermal curvature 
Natural element curvature 
Synchronization of multiple units 
Element length and diameter 
Package size 
Extension rate 
Extension power 
The STEM device is a good example of the benefits that can 
derive from a joint Canadian-NASA program such as Alouette - ISIS. 
It is hoped that with the space shuttle program, a similar interna- 
tional co-operation can be achieved. 
12 6 


Use of extendible boom devices for space shuttle and EVA operations

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