53
LL SPACE FLfGHT ~ ~ N T ~ R NSR 05-003-1 89 APRIL, 1969 SPACE SCEENCES LAB0
LL SPACE FLfGHT ~ ~ N T ~ R
NSR 05-003-1 89
APRIL, 1969
SPACE SCEENCES LAB0
G E 0 T E C H N I C A L E N G 111 E E R I N G
MATERIAL STUDIES RELATED TO LUNAR SURFACE EXPLORATION
James K. M i t c h e l l I a n C. Carmichael Joseph F r i s c h R ichard E. Goodman Paul A. W i therspoon Francois E. Heuz6
SUMMARY TECHNICAL REPORT
Prepared f o r Marsha l l Space F l i g h t Center H u n t s v i l l e , Alabama, under NASA Cont rac t
NSR 05-003-1 89
A p r i l 1969
Space Sciences Labora tory
U n i v e r s i t y o f C a l i f o r n i a , Berke ley 94720
T ' A B L E O F C O N T E N T S
LIST OF ILLUSTRATIONS . . . . . . . . . . . . . . . . . . . . . . . . . ii
LISTOFTABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
PREFACE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i v
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
SUMMARIES OF STUDIES AND CONCLUSIONS
Lunar S o i l and Rock Problems and Considerat ions i n t h e i r So lu t ion . . . . . . . . . . . . . . . . . . . . . . . . . 3
Engineering P r o p e r t i e s of Lunar S o i l s . . . . . . . . . . . . . . 8
Material Proper ty Evalua t ions from Boulder Tracks on t h e Lunar Surface . . . . . . . . . . . . . . . . . . . . . . . . . 10
Impact Records as a Source of Lunar Surface Material P r o p e r t y D a t a . . . . . . . . . . . . . . . . . . . . . . . . . 1 3
Lunar S t r a t ig raphy as Revealed by Crater Morphology . . . . . . . 15
Geochemical S tud ie s . . . . . . . . . . . . . . . . . . . . . . . 1 6 The Appl ica t ion of Geophysical Methods t o Lunar S i t e S tud ie s . . . 17
I n v e s t i g a t i o n of Rock Behavior and St rength . . . . . . . . . . . 19
The Measurement of S t r e s s e s i n Rock . . . . . . . . . . . . . . . 22
The Measurement of Rock Deformabil i ty i n Boreholes . . . . . . . . 26
T r a f f i c a b i l i t y . . . . . . . . . . . . . . . . . . . . . . . . . . 29
F r i c t i o n and Adhesion i n Ultra High Vacuum as Related t o Lunar Surface Explora t ions . . . . . . . . . . . . . . . . . . . 32
U t i l i z a t i o n of Lunar S o i l s f o r Shie ld ing Against Radia t ions , Meteoroid Bombardment and Temperature Gradients . . . . . . . . 34
The NX-Borehole Jack f o r Rock Deformabil i ty Measurements . . . . . 37
Permeabi l i ty and Thermal Conductivity S tud ie s f o r Lunar Surface Probes . . . . . . . . . . . . . . . . . . . . . . . . . 4 1
RECOMMENDATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
i
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
L I S T O F I L L U S T R A T I O N S
Drawing of P r i n c i p a l P a r t s of t h e 3-Component S t r e s s Gage Designed by the U. S. Bureau of Mines ( a f t e r Merril. 1967 R.I. 7015) . . . . . . . . . . . . . . . . . 25
Schematic Diagram of Experimental Equipment . . . . . . 33
NX Borehole P l a t e Bearing Test Device . . . . . . . . . 38
Device Disassembled . . . . . . . . . . . . . . . . . . 38
Borehole Jack Detail . . . . . . . . . . . . . . . . . . 39
ii
L I S T O F T A B L E S
Table ' 1
Table 2
Table 3
Table 4
Table 5
Table 6
Table 7
Table 8
Table 9
Table 10
Table 11
Table 12
T e s t Methods f o r Lunar S o i l and Rock Engineering Proper ty Determination e e e e . e . . . . a . 4
Summary of Lunar S o i l Proper ty Values . . a e . 9
Analysis Resu l t s - Sabine D Boulder Track . e e . e e 12
A p p l i c a b i l i t y of Geophysical Techniques t o t h e Solu t ion of Lunar Soil/Rock Engineer ing Problems . . e . 18
In-Si tu Tes t ing of Rock Behavior and St rength . a e 20
Laboratory Tes t ing of Rock Behavior and S t r eng th . e . . 21
Devices f o r Measuring S t r e s s e s i n Rock on the Ear th 23
Rat ing of In-Si tu S t r e s s Measuring Devices f o r Lunar Operation e e . . . . . . . . ., e . e 24
Devices f o r Measuring Rock Deformabil i ty i n Boreholes e . 27
Rat ing of Rock Deformabil i ty Measuring Devices f o r Lunar Operation . ., e . (. e . e e . e . e . . . . 28
Summary of Lunar S o i l Shie ld ing Study . . . . a . . a 36
Summary of T e s t Resul t s - Comparison of In-Si tu , Core, and Borehole Jack T e s t s . . e . . . . . . a . . 40
i ii
PREFACE
This r e p o r t summarizes the r e s u l t s of s t u d i e s conducted during the
pe r iod March 6, 1967 - June 30, 1968, under NASA research c o n t r a c t
NSR 05-003-189, "Materials S tud ie s Related t o Lunar Surface Exploration."
This s tudy w a s sponsored by t h e Advanced Lunar Missions Di rec to ra t e , NASA
Headquarters, and w a s under t h e t e c h n i c a l cognizance of D r . N. C. Costes,
Space Sciences Laboratory, George C. Marshal l Space F l i g h t Center. Complete
r e s u l t s of t h e work are presented i n a f o u r volume De ta i l ed Technical Report,
The r e s u l t s summarized h e r e i n r ep resen t t h e combined e f f o r t of f ive
f a c u l t y i n v e s t i g a t o r s and a f u l l t i m e p r o j e c t manager/engineer a s s i s t e d by
s i x graduate research a s s i s t a n t s , represent ing several engineer ing and
s c i e n t i f i c d i s c i p l i n e s p e r t i n e n t t o s tudy of l una r s u r f a c e material pro-
p e r t i e s . James K. Mi t che l l , P ro fes so r of C iv i l Engineering, se rved as
P r i n c i p a l I n v e s t i g a t o r and w a s r e spons ib l e f o r those phases of t h e work
concerned wi th problems r e l a t i n g t o luna r s o i l mechanics and the engineer-
i n g p r o p e r t i e s of l una r s o i l s . Co-invest igators were I an C. Cannichael,
P ro fes so r of Geology, i n charge of geo log ica l s t u d i e s ; Joseph F r i sch ,
P ro fes so r of Mechanical Engineering, who w a s respons ib le f o r a n a l y s i s of
f r i c t i o n and adhesion problems and t h e t e s t i n g of materials under high-
vacuum condi t ions ; Richard E. Goodman, Assoc ia te P ro fes so r of Geological
Engineering, who w a s concerned wi th t h e engineer ing geology and rock
mechanics a s p e c t s of t he l u n a r s u r f a c e ; and Paul A. Witherspoon, P ro fes so r
of Geological Engineering, who conducted s t u d i e s r e l a t e d t o thermal and
pe rmeab i l i t y measurements on t h e l u n a r su r face .
A s s i s t a n t S p e c i a l i s t , se rved as p r o j e c t manager and con t r ibu ted t o s t u d i e s
i n t h e areas of rock mechanics and engineer ing geology.
Francois E. H e w & ,
i v
1
INTRODUCTION
It i s axiomatic t h a t , among t h e myriad of t e c h n i c a l and s c i e n t i f i c
f a c t o r s t h a t must be considered i n t h e l u n a r exp lo ra t ion program, t h e
n a t u r e of l u n a r s o i l and rock s u r f a c e materials i s of prime importance i n
the design of s p a c e c r a f t l anding and s u r f a c e mob i l i t y systems , t h e design
of experiments t o be conducted on t h e luna r su r face , mission planning,
and, u l t i m a t e l y , t o mission success . Without s p e c i f i c knowledge of t h e
mechanical p r o p e r t i e s of l una r s o i l s , des igners and mission p lanners have
no choice b u t t o adopt u l t r aconse rva t ive designs and procedures i n an
e f f o r t t o i n s u r e a s t r o n a u t s a f e t y . Thus i t i s of paramount importance
t h a t as much s p e c i f i c information as p o s s i b l e about l una r s u r f a c e material
p r o p e r t i e s be obta ined p r i o r t o t h e f i r s t manned luna r mission, and t h a t
planning and design opt ions f o r f u r t h e r missions remain open t h e r e a f t e r i n
o rde r t o accommodate changes as more and more s p e c i f i c d a t a become available.
The s t u d i e s summarized i n t h i s r epor t were i n i t i a t e d i n an e f f o r t t o
b e t t e r de f ine both t h e s u r f a c e material r e l a t e d engineer ing problems and
t h e r e l evan t p r o p e r t i e s of the materials themselves. Information
developed as a r e s u l t of t h i s e f f o r t w a s then u t i l i z e d i n s p e c i f i c s t u d i e s
of problems considered t o be of c r i t i c a l importance and f o r t h e develop-
ment of a n a l y s i s and t e s t i n g methods t h a t appear p a r t i c u l a r l y promising
f o r t h e s tudy of l u n a r s u r f a c e p r o p e r t i e s by both remote and tact i le means.
The scope of work accomplished during the con t r ac t pe r iod i s indicated
by the fol lowing l i s t of conten ts of t he Deta i led Technical Report, The
names of t he i n v e s t i g a t o r s a s s o c i a t e d wi th each phase of t h e work are
i n d i c a t e d
VOLUME I
LUNAR SOIL MECHANICS AND SOIL PROPERTIES
1. Lunar S o i l and Rock Problems and Considerat ions i n Thei r So lu t ion (James K. Mi tche l l )
(James KO Mitche l l and S c o t t S. Smith)
(James K. Mi t che l l and S c o t t S. Smith)
4 . Impact Records as a Source of Lunar Surface Material Proper ty Data (James K O Mi tche l l , Donald W. Quigley and S c o t t S. Smith)
2. Engineering P r o p e r t i e s of Lunar S o i l s
Material P r o p e r t i e s Evalua t ions from Boulder Tracks on the Lunar Surface 3 .
2
5.
6 ,
1.
2,
3.
4 .
1,
2.
3'
Lunar S t r a t ig raphy as Revealed by Crater Morphology
Geochemical S tud ie s
(Francois E. Heuze' and Richard E , Goodman)
( I . S . E. Carmfchael and J. Nichol l s )
VOLUME I1
APPLICATION OF GEOPHYSICAL AND GEOTECHNICAL METHODS TO LUNAR SITE EXPLORATION
The Appl ica t ion of Geophysical Methods t o Lunar S i t e S tud ie s
I n v e s t i g a t i o n of Rock Behavior and S t r eng th
The Measurement of Stresses i n Rock
The Measurement of Rock Deformabil i ty i n Bore Holes
(Richard E. Goodman, Jan J. Roggeveen and Francois E. Heuze')
(Francois E. Heuze" and Richard E. Goodman)
(Francois E. Heuze" and Richard E , Goodman)
(Richard E. Goodman and Francois E , Heuze')
VOLUME I11
PRELIMINARY STUDIES ON SOIL/ROCK ENGINEERING PROBLEMS RELATED TO LUNAR EXPLORATION
Traf f i c a b i l i t y
F r i c t i o n and Adhesion in Ult rah igh Vacuum as Related t o Lunar Surface Explora t ions
U t i l i z a t i o n of Lunar S o i l s f o r Shie ld ing Against Radia t ions , Meteoroid Bombardment and Temperature Gradien ts
(James KO Mitche l l , S c o t t S. Smith and Donald W. Quigley) '
(J. Fr i sch and U. Chang)
(Francois E , Heuze' and Richard E. Goodman)
VOLUME I V
PRELIMINARY STUDIES FOR THE DESIGN OF ENGINEERING PROBES
1,
2 , Permeabi l i ty and Thermal Conduct ivi ty S tudies f o r Lunar Surface Probes
The NX-Borehole Jack f o r Rock Deformabil i ty Measurements (Richard E. Goodman, Tran K. Van and Francois E. Heuze')
(Paul A, Witherspoon and David F. Katz)
The p r i n c i p a l conclusions r e s u l t i n g from each of t hese s t u d i e s are
presented i n t h i s Summary Technical Report , followed by a l i s t i n g of recom-
mendations p e r t i n e n t t o the advancement of l una r exp lo ra t ion technology.
SUMMARIES OF STUDIES AND CONCLUSIONS
3
LUNAR SOIL AND ROCK PROBLEMS AND
CONSIDERATIONS I N THEIR SOLUTION
Geotechnical engineer ing problems t h a t are r e l a t e d t o l u n a r explora-
t i o n can be d iv ided i n t o (1) those needing s o l u t i o n f o r e a r l y l u n a r
s c i ence missions and (2) t hose r e l a t e d t o extended lunar exp lo ra t ion and
the development of l u n a r bases . Among t h e most important concerns during
e a r l y missions are bear ing capac i ty of t h e l u n a r su r face , s u r f a c e e ros ion
by rocket exhaus t , system contamination, l u n a r s u r f a c e t r a f f i c a b i l i t y ,
sampling, and i d e n t i f i c a t i o n of hazard areas. When extended exp lo ra t ion
and l u n a r base development begin, then problems of excavat ion, under-
ground cons t ruc t ion , i n s u l a t i o n and s h i e l d i n g , and cons t ruc t ion materials
w i l l become important .
Tables have been prepared, presented i n Vol. I of t he F i n a l Report,
which i n d i c a t e
1. The major problem areas and t h e s p e c i f i c p r o p e r t i e s of
l una r materials t h a t must be known i f reasonable s o l u t i o n s
are t o be obtained.
2. Approaches t o de te rmina t ion of t he d i f f e r e n t p r o p e r t i e s and
p r i o r i t i e s f o r proper ty determinat ion.
3 . Some s p e c i f i c test methods t h a t might be used t o acqu i r e the
needed d a t a f o r eva lua t ion of propert ies . , This t a b l e is
reproduced he re as Table 1.
It is concluded t h a t knowledge of l u n a r s o i l dens i ty , compress ib i l i t y ,
s t r e s s - s t r a i n , and s t r e n g t h are of g r e a t e s t importance, b u t t h a t t h i s
knowledge w i l l , f o r t he s h o r t range a t least , have t o be acqui red us ing
less than i d e a l test techniques.,
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8
ENGINEERING PROPERTIES OF LUNAR SOILS
A c r i t i c a l review of a v a i l a b l e informat ion from 34 sources concerning
the p r o p e r t i e s of l u n a r s o i l s has been made, wi th emphasis on information
der ived from Ranger, O r b i t e r , Surveyor and Luna Programs. A d e t a i l e d
t a b u l a t i o n of t h e proper ty va lues and t h e methods used f o r t h e i r determina-
t i o n i s given i n Table 2-1 of t h e De ta i l ed F i n a l Report. A s a r e s u l t of
t h i s review t e n t a t i v e va lues f o r use i n t h e a n a l y s i s of engineer ing
problems have been s e l e c t e d and are presented i n Table 2.
i n Table 2 are estimates presented by Bank* which r e f l e c t t h e r e s u l t s of
s t u d i e s by the Jet Propuls ion Laboratory i n connect ion w i t h the Surveyor
Program. It may be seen t h a t i n gene ra l t he va lues cor robora te each o the r .
Also i n d i c a t e d
*Bank, H, Letter t o 0. H. Vaughan and N o C. Costes , MSFC, March 21, 1968.
9
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10
MATERIAL PROPERTY EVALUATIONS FROM BOULDER
TRACKS ON THE LUNAR SURFACE
The a n a l y s i s of boulder t r a c k s on t h e l u n a r s u r f a c e as seen i n Lunar
O r b i t e r photographs should be p o t e n t i a l l y rewarding i n terms of y i e l d i n g
informat ion on s o i l and rock v a r i a b i l i t y a t d i f f e r e n t l oca t ions .
a b l e q u a n t i t a t i v e de te rmina t ions should be p o s s i b l e i n those cases where
r e l a t i v e l y accu ra t e va lues of boulder s i z e , t r a c k shape and s inkage, and
s lope angle can be obta ined , as should be the case f o r some of t h e
Surveyor r e s u l t s , and as w i l l be p o s s i b l e dur ing Apollo missions.
Theore t i ca l and experimental s t u d i e s are d e s i r a b l e i n o rde r t h a t a
r a t i o n a l a n a l y t i c a l framework may be developed. The r e s u l t s w i l l be use-
f u l no t only f o r boulder t r a c k a n a l y s i s , b u t a l s o f o r s tudy of t h e l u n a r
roving veh ic l e t r a f f i c a b i l i t y problem.
Reason-
The Sabine D boulder t r a c k w a s analyzed us ing several methods i n
a d d i t i o n t o those a l r eady presented i n t h e l i t e r a t u r e . The r e s u l t s of
these ana lyses are summarized i n Table 3. It w a s shown, using bear ing
capac i ty f a c t o r s f o r foo t ings on sand s lopes, t h a t a boulder of s p e c i f i c
g r a v i t y s i m i l a r t o t h a t f o r terrestrial rocks; i c e . , 2.7-3,0, would be
uns t ab le on a 30" s lope having Surveyor s o i l c h a r a c t e r i s t i c s .
o t h e r hand i t would be s t a b l e on a 13" s lope , t h e es t imated s lope on
which the Sabine D boulder f i n a l l y came t o rest.
On the
Analysis of t h e boulder w i t h i n t h e framework of empi r i ca l c o r r e l a t i o n s
developed f o r cons tan t v e l o c i t y r o l l i n g of spheres down s lopes of cohesion-
less s o i l l e d t o the very reasonable boulder dens i ty e s t ima te of 3.0.
From a p p l i c a t i o n of an e m p i r i c a l equat ion developed t o desc r ibe the
r o l l i n g r e s i s t a n c e of a r i g i d wheel i n sand a boulder d e n s i t y of 3.5 w a s
obtained. An estimate obta ined us ing t r a f f i c a b i l i t y r e l a t i o n s h i p s based
on t h e s o i l va lue system gave a dens i ty of 2.7 f o r an assumed va lue of n
equal t o 1. An a n a l y s i s based on s i m i l i t u d e r e l a t i o n s h i p s f o r t r a f f i c -
a b i l i t y gave an u n r e a l i s t i c a l l y low va lue f o r dens i ty . I n a l l cases t h e
estimates involved a number of approximations and assumptions.
Whatever t h e methods u l t i m a t e l y s e l e c t e d f o r boulder t r a c k a n a l y s i s ,
i t w i l l be impera t ive t h a t t he s a m e method be appl ied i n t h e same manner
t o a l l t r a c k s i f meaningful comparative r e s u l t s are t o be obtained. It
i s recommended t h a t a r a t i o n a l theory f o r d e s c r i p t i o n of t h e mechanics of
11
boulder t r a c k formation be developed f o r t h i s purpose. It should b e noted
t h a t only r e g u l a r , continuous t r a c k s have been cons idered thus f a r . Tracks
formed by bouncing, sk ipping , and sk idd ing boulders must be analyzed
s e p a r a t e l y .
12
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13
IMPACT RECORDS AS A SOURCE OF LUNAR SURFACE MATERIAL
PROPERTY DATA
Lunar O r b i t e r photographs show many secondary impact craters formed
by ejecta b locks thrown ou t dur ing the formation of primary craters on
the moon. I n an a t tempt t o s tudy t h e l u n a r s u r f a c e homogeneity from
these photographic records , D r . H. J. Moore of the Astrogeology Branch,
U. S. Geological Survey, developed the fol lowing equat ion semi-empirically
f o r p e n e t r a t i o n of a p r o j e c t i l e i n t o t h e ground,
1
where P = depth of pene t r a t ion , L = l eng th of p r o j e c t i l e , c = cons tan t ,
= m a s s dens i ty of t h e p r o j e c t i I e , pt = m a s s dens i ty of t h e t a r g e t pP material, g = a c c e l e r a t i o n of g r a v i t y , and V = ver t ica l component of
t he impact v e l o c i t y of t h e p r o j e c t i l e . From an a n a l y s i s of secondary
impact crater d a t a from O r b i t e r photographs us ing t h i s equat ion Moore
concluded t h a t t h e l u n a r s u r f a c e i s inhomogeneous over the areas i n v e s t i -
gated.,
0
Because t h i s conclusion i s a t va r i ance wi th the f i n d i n g s a t the f i v e
Surveyor landing sites, f u r t h e r s tudy w a s made of r e l a t i o n s h i p s t h a t might
be used f o r s tudy of secondary impact craters. The Moore equat ion can be
modified t o t h e form
where K i s a s o i l cons tan t and Q i s t h e weight of t he p e n e t r a t o r d iv ided
by t h e c ros s s e c t i o n a l area.
(<200 fps ) p r o j e c t i l e p e n e t r a t i o n i n t o t h e ground were examined us ing
several equat ions . The d a t a examined inc luded p e n e t r a t i o n records f o r
several s o i l types. It w a s found t h a t t he modified form of t h e Moore
equat ion provides t h e b e s t r e l a t i o n s h i p between s o i l type and p r o j e c t i l e
p e n e t r a t i o n on e a r t h . Because of t h i s and because of i t s s imple form,
i t s use f o r f u r t h e r a n a l y s i s of secondary impact craters i s recommended
i n preference t o the o t h e r equat ions t h a t were examined.
Avai lab le d a t a on low impact v e l o c i t y
14
'However, examination of t h e assumptions r equ i r ed f o r t h e a n a l y s i s of
l u n a r secondary impact craters i n d i c a t e t h a t t h e r e exist g r e a t p o s s i b i l i -
t ies f o r e r r o r which can completely nega te the purpose of t he a n a l y s i s i f
it i s app l i ed i n t h e hope of determining abso lu te s o i l p roper ty values. It appears t h a t a t t h e p re sen t t i m e conclusions can only be drawn concern-
i n g l u n a r s o i l v a r i a b i l i t y on t h e b a s i s of l u n a r secondary impact crater
da ta .
Information on secondary impact c r a t e r s has proved beyond any doubt
t h a t l a r g e areas of the moon's s u r f a c e are covered by s o i l t o a depth of
a t least one t o two meters. Because the boulders bounced out of t he
secondary craters, i t would appear t h a t t h e l u n a r s o i l ( o r underlying
rock) o f f e r s a s i g n i f i c a n t r e s i s t a n c e t o pene t r a t ion .
It i s t o be hoped t h a t cont inued s tudy of secondary c r a t e r i n g
phenomena w i l l l e a d t o a reduct ion of t he u n d e r t a i n t i e s i n t h e ana lyses ,
and t h a t more s p e c i f i c q u a n t i t a t i v e estimates of s o i l p r o p e r t i e s can be
ob ta ined .
15
LUNAR STRATIGRAPHY AS REVEALED BY CRATER MORPHOLOGY
The e x t e n t and th ickness of t h e l u n a r s u r f i c i a l l a y e r w i l l p l ay a
major r o l e i n
1. Traf f i c a b i l i t y a n a l y s i s of planned traverses
2. Optimizat ion of bor ings f o r sampling purpose
3. Analysis of foundat ions f o r major s t r u c t u r e s
4 . Const ruc t ion of excavat ions and embankments.
A c r i t i c a l review w a s conducted of t he techniques used s o f a r t o
determine l u n a r s t r a t i g r a p h y from crater morphology. They are:
1. Comparative s t u d i e s of Ranger photographs--and l abora to ry s imula t ion of over lay depos i t i on ( J a f f e , 1965,1966)
2. Direct s t u d i e s of O r b i t e r and Surveyor photographs--Analysis of b lock f i e l d s , terraces and outcrops
3. Comparative s t u d i e s of O r b i t e r photographs--Considerations of impact crater morphology (Quaide and Oberbeck, 1967,1968)
4 , U s e of a mathematical model f o r time-dependent l u n a r crater r i m - e ros ion and f l o o r depos i t i on (Roos, 1968)
The r e s u l t s of a l l s t u d i e s are summarized i n t h e Deta i led Technical
Report (Vol. I , Chapter 5 ) i n t e r m s of technique used, l o c a t i o n of
area s tud ied on t h e moon, crater diameter range, probable o r i g i n of
crater, and e s t ima ted depth of s u r f i c i a l l una r l a y e r .
S tud ie s based upon v i s u a l observa t ion of l u n a r craters and cornpari-
son wi th exper imenta l r e s u l t s o r a n a l y t i c a l models have apprec iab ly
narrowed the range of conclusions regarding t h e luna r s u r f a c e s t r a t i g r a p h y .
Most maria s u r f a c e s are be l i eved t o be o v e r l a i n by a l a y e r of f i n e gra ined ,
cohes ionless t o weakly cohesive fragmented rock whose th ickness varies
from a few meters t o a few t e n s of meters ( see Table 5.1, Ch. 5, Vol. I ) .
Compress ib i l i ty decreases and average g r a i n s i z e inc reases from t h e
s u r f a c e down. Rubble i s probably present . This f ragmental b l anke t can
probably be excavated and handled wi thout t h e use of explos ives except i n
t h e v i c i n i t y of l a r g e c r a t e r s where very l a r g e blocks may be found.
For f i n a l mission planning a t s p e c i f i c sites, ex tens ive high resolu-
t i o n photographic coverage is requ i r ed , and the i n t e r p r e t a t i o n should r e l y
upon v i s u a l observa t ion (Lunar O r b i t e r Photo Data Screening Group 1967,1968).
Other procedures are s t i l l t o o open t o va r i ed i n t e r p r e t a t i o n s a t t h e p re sen t
t i m e .
16
GEOCHEMICAL STUDIES
Study w a s made of t h e probable c h a r a c t e r i s t i c s of l u n a r lava and
the imp l i ca t ions of t h e s e c h a r a c t e r i s t i c s i n t h e i n t e r p r e t a t i ~ n of l u n a r
composition and h i s t o r y . It w a s concluded t h a t because t h e a v a i l a b i l i t y
of oxygen i n t h e lunar and terrestrial environments is d i f f e r e n t t he
p r o p e r t i e s of l u n a r and terrestrial b a s a l t may d i f f e r , e s p e c i a l l y wi th
r e s p e c t t o t h e magnetic minera ls .
It is suggested t h a t i n t e r p r e t a t i o n and c o l l e c t i o n of remnant
magni t iza t ion in re turned l u n a r samples may be cons t ra ined by the
p o s s i b i l i t y t h a t t h e carriers of magnet izat ion, t he Fe-Ti ox ides , could
have Curie temperatures in te rmedia te between t h e d iurna l temperature
l i m i t s
17
THE APPLICATION OF GEOPHYSICAL METHODS
TO LUNAR SITE STUDIES
Geophysical methods can be d iv ided i n t o two ca tegor ies : those which
measure n a t u r a l l y e x i s t i n g f i e l d s , and those which measure a r t i f i c i a l l y
c rea t ed f i e l d s . Measurements of n a t u r a l l y e x i s t i n g f i e l d s , such as
g r a v i t a t i o n a l and magnetic, r e f l e c t average condi t ions over l a r g e volumes.
On t h e o t h e r hand, seismic, electrical r e s i s t i v i t y , o r conductive
e lec t romagnet ic methods which make use of a r t i f i c i a l l y c r e a t e d f i e l d s can
usua l ly be s o designed as t o r e so lve t h e e f f e c t of l o c a l s t r u c t u r a l
f e a t u r e s . A l l geophysical methods however are dependent f o r t h e i r success
upon an apprec i ab le c o n t r a s t i n phys i ca l p r o p e r t i e s between t h e body t o be
s t u d i e d and the material surrounding it.
Lunar engineer ing problems which can be i n v e s t i g a t e d us ing geo-
phys i ca l methods inc lude those which concern: l o c a t i o n and d e l i n e a t i o n
of s o i l depos i t s ; foundat ions; excavat ions; l o c a t i o n and d e l i n e a t i o n of
n a t u r a l c a v i t i e s ; determina t ion of engineer ing p r o p e r t i e s of s o i l s and
rocks; and c h a r a c t e r i z a t i o n of l u n a r resources .
The a p p l i c a b i l i t y of s p e c i f i c techniques t o s p e c i f i c problems i s
summarized i n Table 4 .
18
TABLE 4
APPLICABILITY OF GEOPHYSICAL TECHNIQUES
TO THE SOLUTION OF LUNAR SOIL/ROCK ENGINEERING PROBLEMS
__ ~-
Soil o r Rock Attribute Application Geophysical Method*
Deformability o f Soi l s
Shear Strength
Dens i t y
Porosity
Soil Prof i le and Depth t o Rock
Underground Cavities
Ease of Removal
Dynamic Response Spectrum
Foundations Seismic ( M )
Slope S t a b i l i t y None
Excavations; Gravity (M) Shielding; Seismic (M) Founda t i ons
Storage Underground Res i s t i v i ty** ( M )
Excavations ; Seismic ( I ) Foundations Gravity ( I )
Traff i cabi 1 i t y 5 Seismic ( I ) Storage Underground Gravity ( I )
Excavations seismic ( I )
Foundations of Seismic (M) Rotating Towers
*M = property closely related t o d i r e c t l y measured quant i t ies .
I = property inferred through correlat ions or from comparison of measured response w i t h idealized te r ra in models.
**Probably inappl i cab1 e t o 1 unar exploration because of the expected t o t a l absence of pore f luids .
19
INVESTIGATION OF ROCK BEHAVIOR AND STRENGTH
Whereas, u n t i l a few years ago, design of s t r u c t u r e s i n rock w a s
s t i l l approached on t h e b a s i s of experience and rule-of-thumb, r ecen t
developments i n Rock Mechanics are provid ing more and more dependable
and real is t ic t o o l s of i n v e s t i g a t i o n , t he use of which appears v i t a l
f o r sound engineer ing p r a c t i c e , be i t e a r t h l y o r l una r .
Four s t e p s are involved i n t h e design of any rock s t r u c t u r e (Deere,
19671 :
1, Determination of boundary condi t ions
2. Determination of the engineer ing p r o p e r t i e s of materials
3 . Pred ic t ion of s t r u c t u r e behavior
4 . Assessment of a c t u a l performance
The second s t e p i s considered here . A summary l i s t i n g and r a t i n g of
through i n s i t u and l abora to ry t e s t i n g programs
rock t e s t i n g techniques f o r behavior and s t r e n g t h , i n the l abora to ry and
i n s i t u , are presented i n Tables 5 and 6.*
I n the p re sen t s ta te -of - the-ar t design i s most ly based on i n s i t u
behavior and l abora to ry s t r e n g t h ana lyses , owing t o t h e bulk iness of
f i e l d equipment., However ins t ruments can be designed t o ope ra t e i n bore-
ho le s on t h e moon, (Goodman, Van and Heuz6, 1968), and meaningful
l abora to ry tests can be performed on a l i m i t e d q u a n t i t y of r e tu rned
samples, t o y i e l d , d i r e c t l y o r through c o r r e l a t i o n techniques, r e l i a b l e
d a t a on luna r rock s t r e n g t h and behavior t h a t are needed f o r a sound
planning of l u n a r exp lo ra to ry missions
*For b ib l iography, t he r eade r i s r e f e r r e d t o the Vole 11, Chapter 2 of t he Deta i led F i n a l Technical Report ,
20
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22
THE MEASUREMENT OF STRESSES I N ROCK
Rock d i f f e r s from many o t h e r engineer ing materials i n t h a t i t o f t e n
exists under s i g n i f i c a n t i n i t i a l stresses. Excavation a t t h e s u r f a c e o r
underground d i s t u r b s t h i s stress f i e l d and induces a new one. The f i n a l
stress state i s thus d i r e c t l y dependent upon t h e i n i t i a l one which must
t h e r e f o r e be determined f o r any r a t i o n a l ana lyses of a rock s t r u c t u r e .
An ex tens ive review of techniques used f o r t h e de te rmina t ion of
stresses i n a rock mass on the e a r t h is sumnarized i n Table 7.
A l i s t i n g and r a t i n g of probes be ing used f o r t h e purpose of stress
measurements are given i n Table 8.*
cr i ter ia which are p e r t i n e n t f o r l u n a r a p p l i c a t i o n s .
The r a t i n g values are ass igned using
One of t h e most promising gages f o r e a r t h use has been designed by
the U. S. Bureau of Mines and is shown i n Fig. 1.
*Def in i t ions of probe numbers and r e fe rence numbers are contained i n t h e De ta i l ed F i n a l Technical Report , Vole 11, Chapter 3.
23
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x 0 0 rn
a 0 0 v)
26
THE MEASURFXENT OF ROCK DEFORMABILITY I N BOREHOLES
Mapping and d e s c r i p t i o n of var ious rock members w i t h i n an e a r t h s i t e
may r e q u i r e many f e e t of d r i l l ho les . However q u a n t i t a t i v e charac te r iza-
t i o n of the rock l i m i t s on t h e s o l e b a s i s of re turned samples is a p t t o
be misleading; t h e s o f t e r and weaker components tend t o be l o s t and the
f a b r i c of t he rock b lock-f rac ture system i n s i t u i s not sampled. The
w a l l s of bor ings form more complete samples of the rock m a s s ,
Accordingly w i t h i n t h e p a s t few yea r s a number of devices ( d i l a t o -
meters, borehole j a c k s , borehole penetrometers) have been developed which
can be i n s e r t e d i n t o a borehole t o apply a load and measure t h e response
d i r e c t l y on i t s w a l l s . They combine the advantages of reduced s i z e and
deeper i n v e s t i g a t i o n .
A l i s t i n g and r a t i n g of t hese probes i s summarized i n t h e fol lowing
t ab le s . " E f f o r t s should be d i r e c t e d towards t h e l u n a r i z a t i o n of a borehole
j a c k us ing LVDT'S as monitoring u n i t s .
u se o f narrow angle j acks be i n v e s t i g a t e d f o r t e s t i n g of i n s i t u s t r e n g t h
c h a r a c t e r i s t i c s of s o i l s o r rocks
It i s a l s o recommended t h a t the
*A l i s t of r e fe rences i s given i n Vol, 11, Chapter 4 of t h e Deta i led F i n a l Technical Report,
27
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29
TRAFFI CABILITY
Because of t h e severe c o n s t r a i n t s on weight , power supply, and t i m e
t h a t w i l l be a s soc ia t ed wi th any lunar mission, as w e l l as t h e need t o
i n s u r e s a f e t y t o as g r e a t an e x t e n t as p o s s i b l e , a p r e c i s i o n of design
and e s t ima t ion of r e l evan t mob i l i t y f a c t o r s w i l l be needed f o r l una r
v e h i c l e s t h a t exceeds by f a r any requirements imposed on t h e design and
performance p r e d i c t i o n of terrestr ia l veh ic l e s . Both the topographic
c h a r a c t e r i s t i c s of the t e r r a i n and t h e p h y s i c a l p r o p e r t i e s of t h e s u r f a c e
materials wi th which t h e v e h i c l e i n t e r a c t s are important. Emphasis during
t h i s p r o j e c t has been on t h e s u r f a c e material r e l a t e d f a c t o r s wi th the
o b j e c t i v e s of (1) reviewing methods f o r s o l u t i o n of v e h i c l e mob i l i t y
problems, (2) recommending methods f o r use i n i n t e g r a t i o n of s o i l d a t a
i n t o v e h i c l e design and mission planning, and ( 3 ) recommending methods
f o r determinat ion of t h e needed s o i l da ta .
The conclusions r e s u l t i n g from t h e s e s t u d i e s are as fol lows.
(1) While complete monoscopic photographic coverage of t h e moon has been
provided by Orb i t e r , t he s m a l l scale and l i m i t e d q u a l i t y and q u a n t i t y
of s t e r e o coverage makes topographic a n a l y s i s on t h e scale needed f o r
t r a f f i c a b i l i t y s t u d i e s d i f f i c u l t .
(2) Both t h e s o i l va lue (U. S. Army Ordnance Tank-Automotive Command Land
Locomotion Research Laboratory Method) and t h e cone index (Army
Mobil i ty Branch, Corps of Engineers, Waterways Experiment S t a t i o n )
systems of t r a f f i c a b i l i t y a n a l y s i s have been reviewed. These two
systems are used most ex tens ive ly f o r off-the-road locomotion s t u d i e s
a t t h e p re sen t t i m e , The major advantage of t he s o i l va lue system is
t h a t i t y i e l d s q u a n t i t a t i v e va lues of performance parameters , e ,g .
t o t a l t h r u s t , drawbar p u l l , power requirements, f u e l consumption,
which can be used f o r v e h i c l e design and mission planning. Its
major disadvantages are t h a t p a r t s of t h e t h e o r e t i c a l b a s i s of t he
method are ques t ionable , t h e t e s t i n g r equ i r ed f o r de te rmina t ion of
t he needed s o i l d a t a i s complex and n o t r e a d i l y adaptab le t o luna r
s u r f a c e opera t ions , and i t i s d i r e c t l y app l i cab le only t o level
ground condi t ions .
30
The cone index method, on t h e o t h e r hand, involves very simple
p e n e t r a t i o n t e s t i n g which could be e a s i l y adapted f o r l una r opera-
t i o n s . The disadvantage of t h i s method, however, is t h a t t h e
information obta ined i s only s u i t a b l e f o r determinat ion of whether
a given v e h i c l e w i l l o r w i l l n o t s a t i s f a c t o r i l y n e g o t i a t e a given
t e r r a i n . This may poss ib ly be overcome i n t h e f u t u r e through
f u r t h e r development of s i m i l i t u d e a n a l y s i s techniques.
A review of r ecen t t r a f f i c a b i l i t y and mobi l i ty l i t e r a t u r e has i n d i -
ca ted t h e fol lowing:
a.
b.
C.
de
e.
f .
The s o i l va lue system appears t o be widely used as a b a s i s
f o r l u n a r roving v e h i c l e ana lyses .
It would be d e s i r a b l e t o cont inue s t u d i e s f o r development of
methods of conver t ing c, $I, and p t o k k and n.
A means f o r conversion of cone index d a t a t o s o i l value
system parameters would be very u s e f u l .
Fu r the r a n a l y s i s of bea r ing capac i ty approaches t o v e h i c l e
mob i l i t y would appear des i r ab le .
An analog computer technique s i m i l a r t o t h a t r epor t ed by
VanDuesen (Chrysler Gorp., Contract NASW-1287, May 1966) f o r
modeling the dynamics of so i l -veh ic l e i n t e r a c t i o n appears
promising and is deserving of f u r t h e r s tudy.
A number of r e p o r t s were reviewed which are concerned mainly
wi th the design and t e s t i n g of proposed luna r roving veh ic l e s
of va r ious types. Many of these s t u d i e s were done on simu-
l a t e d lunar -sur face materials t h a t were prepared without t h e
d e t a i l e d knowledge of s o i l condi t ions t h a t has been provided
by Surveyor. Some r e a n a l y s i s and f u r t h e r t e s t i n g us ing
"Surveyor Soi l" would appear i n order .
c' $Iy
The Engineer ing Lunar Model Surface (ELMS) has been reviewed and
found inappropr i a t e f o r q u a n t i t a t i v e r ep resen ta t ion of l u n a r s u r f a c e
p r o p e r t i e s f o r t r a f f i c a b i l i t y ana lyses , Te r ra in c h a r a c t e r i z a t i o n
techniques now being developed by t h e U.S.G.S. are promising.
A s i m i l i t u d e approach t o t h e s o l u t i o n of l u n a r t r a f f i c a b i l i t y
problems i s very appeal ing, s i n c e q u a n t i t a t i v e measures of v e h i c l e
performance could conceivably be obta ined us ing model tests and t h e
31
r e s u l t s of s imple s o i l tests; e.g. cone index. Unfortunately the
s i m i l i t u d e c o r r e l a t i o n s developed by t h e Waterways Experiment
S t a t i o n f o r pneumatic tires do n o t appear s u i t a b l e f o r d e s c r i p t i o n
of t he behavior of proposed l u n a r v e h i c l e wheels; e.g. metal-elastic
wheel, w i r e wheel. It is d e s i r a b l e t h a t acce le ra t ed tes t programs
be i n i t i a t e d wi th t h e o b j e c t i v e s of (1) p o s s i b l e ex tens ion of t h e
method f o r u se wi th proposed l u n a r v e h i c l e wheel types and
(2) eva lua t ion of key t r a f f i c a b i l i t y f a c t o r s such as t h e in f luence
of s lopes , l i g h t wheel loads and con tac t p re s su res .
(6) A l i m i t e d s tudy of a v a i l a b l e d a t a on t h e performance c h a r a c t e r i s -
t i c s of t he metal-elastic and w i r e wheels sugges ts t h a t t hese
designs may be over ly conserva t ive f o r a p p l i c a t i o n t o the l u n a r
su r face . Some recons ide ra t ion of t hese designs appears i n order .
32
FRICTION AND ADHESION I N ULTRA HIGH VACUUM AS
E L A T E D TO LUNAR SURFACE EXPLORATIONS
Since a h igh vacuum environment may produce c l ean s u r f a c e s , f r i c t i o n
and adhesion between con tac t ing s o l i d s may be s i g n i f i c a n t l y increased
re la t ive t o t h e i r magnitudes i n t h e normal terrestrial atmosphere. The
consequences of t hese e f f e c t s may be important i n t h e design and ope ra t ion
of roving v e h i c l e s o r o t h e r equipment on the lunar sur face .
A s a p a r t of t h i s p r o j e c t a review of s t u d i e s on f r i c t i o n and
adhesion w a s made, followed by a design f o r r o l l i n g f r i c t i o n tests
u t i l i z i n g a modified form of equipment a l r eady a v a i l a b l e i n our labora-
t o r i e s . Included i n t h i s design are p rov i s ions f o r ion bombardment of
rock specimens t o s imula t e s o l a r wind condi t ions . The r e s u l t s of f o u r
pre l iminary tests of adhesion i n vacuum between copper and obs id i an and
between aluminum and obs id ian are presented. The purposes of t hese
tests w e r e t o determine t h e c a p a b i l i t y of an e x i s t i n g f o r c e dynamometer,
t o determine the magnitude of rock outgass ing and adhesion, and t o
determine t h e t i m e needed f o r pump down t o p re s su re i n t h e range of
IO-” t o IO-’’ t o r r .
An experimental conf igu ra t ion has been designed f o r t h e de te rmina t ion
of c o e f f i c i e n t s of r o l l i n g f r i c t i o n between a wheel and a rock s u r f a c e
relative t o the app l i ed load , temperature , wheel s i z e and wheel ve loc i ty .
A schematic diagram of t h e experimental arrangement i s shown i n Fig. 2 .
Detail drawings and d e s c r i p t i o n s of t h e design and ope ra t ion of t h i s
appara tus are presented i n Chapter 2 , Vol. I11 of t h e Deta i led Technical
Report ,
33
P
34
UTILIZATION OF LUNAR SOILS FOR SHIELDING AGAINST
RADIATIONS, METEOROID BOMBARDMENT AND TEMPERATURE GRADIENTS
P r o t e c t i o n has t o be provided f o r a s t r o n a u t s on t h e moon a g a i n s t
t h r e e environmental f a c t o r s : r a d i a t i o n s meteoroid bombardment, and
excess ive temperature g rad ien t s e Extended s t a y times and payload
c o n s t r a i n t s w i l l r e q u i r e t h a t some of t he s h i e l d i n g materials be ind i -
geneous t o t h e l u n a r su r face . Lunar s o i l s may be s u i t a b l e f o r t h i s
purpose.
P resen t knowledge regard ing each of t he mentioned hazards has been
reviewed and a model s e l ec t ed . Lunar s u r f a c e material p r o p e r t i e s used
can be those s e l e c t e d i n t h i s r e p o r t (Ch. 2, Vol. I ) . F i r s t estimates
of s h i e l d i n g th icknesses are then e s t a b l i s h e d corresponding t o a given
set of assumptions whose v a l i d i t y i s d iscussed . Fur ther research needed
is a l s o o u t l i n e d where i t i s f e l t t h a t major u n c e r t a i n t i e s s t i l l e x i s t
f o r t h e es tab l i shment of f i n a l s h i e l d i n g s p e c i f i c a t i o n s a g a i n s t a given
hazard,
Shie ld ing a g a i n s t r a d i a t i o n s
Lunar r a d i a t i o n s h i e l d i n g w i l l have t o be designed a g a i n s t e n e r g e t i c
s o l a r r a d i a t i o n f o r missions longer than one week,
a b i l i s t i c
The hazard is prob-
A procedure i s presented (Ch. 5, Vol. 111) f o r determining conserva-
t ive design s p e c i f i c a t i o n s based upon mission dura t ion , a l lowable t o t a l
r a d i a t i o n dose, d e s i r e d p r o b a b i l i t y of no overexposure, equ iva len t
aluminum s h i e l d th i cknesses , and average l u n a r s o i l dens i ty .
Shie ld ing a g a i n s t meteoroids
The meteoroid hazard i s p r o b a b i l i s t i c i n na ture . A model i s s e l e c t e d
f o r t he m a s s f l u x r e l a t i o n s h i p of meteoroid i n f a l l .
A procedure i s presented which completely determines the s h i e l d
s p e c i f i c a t i o n s a g a i n s t e ros ion and p e r f o r a t i o n given t h e mission l eng th ,
t h e s h i e l d area, t h e des i r ed p r o b a b i l i t y of no s h i e l d f a i l u r e and the
maximum meteoroid m a s s a g a i n s t which the s h i e l d w i l l be designed.
Addi t iona l parameters e n t e r i n g t h e computations are t h e impact c h a r a c t e r i s -
t i c s ( e j e c t a and crater d iameter ) , and t h e l u n a r s o i l dens i ty . A s i n t he
case of r a d i a t i o n s h i e l d i n g the procedure i s expanded i n t o t y p i c a l computa-
t i o n s f o r d i f f e r e n t s p e c i f i c a t i o n s and parameter values .
35
Shie ld ing a g a i n s t temperature g rad ien t s
The o b j e c t i v e i s t o determine under which th ickness of l una r s o i l s ,
d i u r n a l temperature v a r i a t i o n s w i l l be l i m i t e d t o a p r e s p e c i f i e d amount
(chosen he re as 1 'K) .
(T> 14 days) and of s h i e l d area.
The problem i s independent of mission l eng th
A review of p o s s i b l e thermal models of t h e luna r s u r f a c e l a y e r l eads
t o s e l e c t i o n of a l i k e l y b racke t f o r d i f f u s i o n t i m e s , and corresponding
computations of s o i l s h i e l d th icknesses .
Deta i led conclusions have been drawn f o r each of t h e hazards
considered i n t h i s work (Ch. 3 , Vol. 111). Recurr ing parameters v i t a l
t o s o i l s h i e l d design have been assigned s p e c i f i c va lues o r va lue
b racke t s t ak ing i n t o account t h e most up-to-date knowledge of l u n a r
s u r f a c e p r o p e r t i e s , p rocesses and environment. Overall r e s u l t s are
summarized i n Table 11.
36
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c, S a, -a S a, Q a, -0 S
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V c, v)
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5 a, L 5
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P
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c, S a,
W S a, Q a, -0 S H
37
THE NX-BOREHOLE JACK FOR ROCK DEFORMAB ILITY MEASUREMENTS
A s descr ibed i n t h e Deta i led Technical Report (Ch. 4 , Vole 11) a
number of ins t ruments have been b u i l t t o measure rock and s o i l deform-
a b i l i t y i n boreholes , whose purpose is t o guide a r a t i o n a l design of
foundat ions o r underground openings. '
P a r t i c u l a r a t t e n t i o n i s given t o t h e borehole jack developed by
Goodman e t , a l . , 1968,as i t seems w e l l s u i t e d f o r t h e purposes and con-
s t r a i n t s of t he l u n a r program. This instrument i s presented i n Figures 3,
4 and 5,
The r e s u l t of deformabi l i ty t e s t i n g i n a borehole of diameter , d, i s
a curve of app l i ed pressure, Q,versus d i ame t ra l deformation. Data i n t e r -
p r e t a t i o n has been i n v e s t i g a t e d i n depth wi th r e spec t t o t h e fol lowing
parameters: p l a t e width, rock ' s Poisson ' s r a t i o , non l inear rock
p r o p e r t i e s , p l a t e r i g i d i t y , c rack formation, w a l l roughness and round-
ness .
The s i z e of t h e test i s l a r g e enough s o as t o be s i g n i f i c a n t wi th
r e spec t t o geologic d i s c o n t i n u i t i e s , a n d i t s r e s u l t s compare very
favorably w i t h o t h e r i n s i t u tests f o r deformabi l i ty which are much more
expensive and cumbersome. (See Table 12 ) .
38
FIGURE 3. NX Borehole Plate Bearing Test Device
FIGURE 4. Device Disassembled
39
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40
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4 1
PERMEABILITY AND THERMAL CONDUCTIVITY
STUDIES FOR LUNAR SURFACE PROBES
Among the o b j e c t i v e s of man's s tudy of t he moon i s an understanding
of t h e flow of h e a t and f l u i d s through lunar materials. This knowledge i s
n o t only of s c i e n t i f i c va lue , b u t i t i s e s s e n t i a l t o t he s o l u t i o n of
engineer ing problems i n exp lo r ing t h e moon, I n approaching these problems,
two parameters of g r e a t importance are the t r a n s p o r t c o e f f i c i e n t s :
thermal conduct iv i ty and f l u i d permeabi l i ty .
A s a f i r s t approach t o the measurement of t hese parameters , i t is
proposed t h a t cons ide ra t ion be given t o a s u r f a c e probe, i .e. a device
t h a t w i l l rest d i r e c t l y on t h e s u r f a c e of t he material t o be measured.
I n determining thermal conduct iv i ty , h e a t i s t r a n s f e r r e d i n t o t h e material,
and appropr i a t e temperature and h e a t f low measurements are made. I n
determining permeabi l i ty , a gas i s i n j e c t e d i n t o the material and
appropr i a t e p re s su re and flow rate measurements are made.
Since both t h e s e t r a n s p o r t processes are non l inea r from a s t r ic t
mathematical s t andpo in t , cons ide ra t ion is f i r s t given t o t h e corresponding
l i n e a r problems. For the flow of h e a t , t h i s amounts t o assuming a
temperature independent thermal conduct iv i ty . For t h e flow of gases , t h e
problem i s more complicated i n t h a t t h e fundamental n a t u r e of t h e flow
process changes as p res su re varies over several o rde r s of magnitude. Such
a pres su re range is a n t i c i p a t e d , due t o t h e low abso lu te p re s su re on the
moon and t h e r e l a t i v e l y h igh p res su re i n f lows of i n t e r e s t . I n under-
s t and ing t h i s complex t r a n s p o r t p rocess , t he h igh p res su re ( o r continuum)
range cannot be neglec ted . The low p res su re ( o r r a r e f i e d ) regimes may n o t
p l ay a s i g n i f i c a n t r o l e i n t h e o v e r a l l flow process , Consequently, t he
continuum range is i n v e s t i g a t e d f i r s t , and f o r s teady s ta te flow, the
process i s l i n e a r .
Solu t ions f o r one p o s s i b l e probe conf igu ra t ion are obta ined f o r bo th
of t hese l i n e a r problems. The a p p l i c a b i l i t y of these s o l u t i o n s i s
inves t iga t ed . This c o n s i s t s , i n p a r t , of a pre l iminary examination of
t h e e f f e c t s on gas flow of r a r e f a c t i o n .
This s tudy is c l e a r l y only a f i r s t s t e p and f u r t h e r i n v e s t i g a t i o n s ,
i nc lud ing experimental work, are recommended. For t h e experiments t o be
meaningful, they must inc lude i n v e s t i g a t i o n s on porous media i n vacuo.
RECOMMENDATIONS
42
RECOMMENDATIONS
The fo l lowing recommendations are made relative t o f u r t h e r s t u d i e s
of l u n a r s u r f a c e materials and t h e i r r e l a t i o n s h i p s t o l u n a r s u r f a c e
exp lo ra t ion . They are l i s t e d i n t h e same sequence as the summary of
s t u d i e s i n t h e preceding s e c t i o n .
1. In t ens ive e f f o r t s are needed t o determine t h e e x t e n t t o which d a t a
such as those provided by LM landing records , photographic coverage
of landing pad s inkage and a s t r o n a u t f o o t p r i n t s , and s imple tests
(e. g. , p e n e t r a t i o n , t r ench ing , s l i d i n g ) us ing t h e Apollo hand t o o l s
can be used t o determine q u a n t i t a t i v e va lues of t he p r o p e r t i e s
of t he l u n a r s o i l i n s i t u . Useful information w i l l be provided by
examination of re turned l u n a r samples from e a r l y Apollo missions.
Because these samples w i l l be d i s tu rbed , however, it is n o t l i k e l y
t h a t q u a n t i t a t i v e measurement of mechanical p r o p e r t i e s w i l l y i e l d
r e s u l t s app l i cab le t o t h e l u n a r s o i l i n s i t u . These i n v e s t i g a t i o n s
should be supplemented by f u r t h e r s tudy of Lunar O r b i t e r photographs
and Surveyor da t a .
2 . A r a t i o n a l theory should b e developed f o r d e s c r i p t i o n of t h e
mechanics of boulder t r a c k formation, and boulder t r a c k s on the
luna r s u r f a c e should be analyzed i n a c o n s i s t e n t manner.
w i l l t h e development of such a theory be u s e f u l f o r deduct ion of
s u r f a c e material p r o p e r t i e s , b u t i t w i l l a l s o b e u s e f u l i n considera-
t i o n of t r a f f i c a b i l i t y problems
Not only
3 . Addi t iona l s tudy of t h e problem of dynamic p e n e t r a t i o n of bodies i n t o
the s u r f a c e of the e a r t h and moon, t o enable b e t t e r i n t e r p r e t a t i o n of
secondary impact craters and a l s o the p o s s i b l e development of s ens ing
techniques f o r s o i l eva lua t ion us ing p e n e t r a t o r s i s reconmended,
4 . High r e s o l u t i o n photographic coverage ( r e s o l u t i o n t o a t least 0.5 m)
is d e s i r a b l e f o r mission p lanning a t s p e c i f i c si tes on t h e moon.
This photography is needed f o r i n fe rence of l una r s t r a t i g r a p h y ,
d e f i n i t i o n of s u r f a c e topography on a scale appropr i a t e f o r s t u d i e s
of a s t r o n a u t and v e h i c l e mobi l i ty , and d e f i n i t i o n of p o s s i b l e
hazards .
43
5. Re l i ab le d a t a on luna r rock s t r e n g t h and behavior can be used f o r
s c i e n t i f i c i n t e r p r e t a t i o n of l una r h i s t o r y and w i l l be needed f o r
proper design and cons t ruc t ion of f a c i l i t i e s on and under the
luna r s u r f a c e , Instruments should be designed t o provide t h i s
information.
6 . S tudies are needed t o d e f i n e more p r e c i s e l y t h e r e l a t i o n s h i p s
between s o i l d a t a obta ined us ing penetrometers and p r e d i c t i o n of
t r a f f i c a b i l i t y parameters
7. Since t h e s o l u t i o n of t h e t o t a l t r a f f i c a b i l i t y problem requ i r e s
cons ide ra t ion of bo th topographic and material c h a r a c t e r i s t i c s , terrestrial s imula t ions of proposed luna r veh ic l e s o r v e h i c l e
components should be c a r r i e d out on c a r e f u l l y s e l e c t e d sites.
8. Abandonment of the Engineering Lunar Model Surface (ELMS) i s recom-
mended i n favor of power s p e c t r a l dens i ty techniques be ing developed
by the U.S.G.S, f o r t e r r a i n c h a r a c t e r i z a t i o n .
9. Although i t appears t h a t ou r knowledge of t he mechanical p r o p e r t i e s
of l u n a r s u r f a c e s o i l s exceeds our p r e s e n t a b i l i t y t o use t h a t know-
ledge i n a q u a n t i t a t i v e manner f o r t h e design of l una r roving v e h i c l e s
and p r e d i c t i o n of t h e i r performance, i t i s imperat ive t h a t t h e ten ta-
t i v e conclusion from Surveyor r e s u l t s t h a t s u r f a c e s o i l s are reason-
ab ly similar i n p r o p e r t i e s a t d i f f e r e n t p o i n t s on t h e moon be
confirmed, Of p a r t i c u l a r importance a l s o i s t h e need f o r pressure-
s inkage da ta ,
Earth-based s imula t ions may provide one p o s s i b l e source f o r t h i s
needed information. Simulated l u n a r s o i l s having the proper grada-
t i o n , dens i ty , cohesion, and angle of i n t e r n a l f r i c t i o n can be
prepared and t e s t e d under conf in ing p res su res r e p r e s e n t a t i v e of those
on the moon. The r e s u l t s of such tests would provide i n s i g h t i n t o
t h e deformation behavior of a c t u a l l u n a r s o i l s . Simple tests; e .g . ,
penetrometers , a n a l y s i s of s p a c e c r a f t - s o i l and a s t r o n a u t - s o i l i n t e r -
a c t i o n s during e a r l y Apollo miss ions , w i l l provide inva luab le d a t a
concerning l u n a r s o i l v a r i a b i l i t y and, t o some e x t e n t , t h e stress-
s t ra in behavior .
44
10. It i s recommended t h a t research be i n t e n s i f i e d on t h e problem of
wheel-soil i n t e r a c t i o n wi th s t u d i e s proceeding on two f r o n t s ,,
a. For t h e s h o r t range it may be p o s s i b l e t o extend t h e WES
s i m i l i t u d e method t o performance p r e d i c t i o n s f o r l una r
roving v e h i c l e wheels. Tests should be conducted us ing
appropr i a t e wheel types and loadings and s imula ted l u n a r
s o i l s . I n v e s t i g a t i o n s should be made of the in f luence of
wheel load , wheel s i z e , wheel s l i p , s o i l cond i t ions , and t e r r a i n
i n c l i n a t i o n as r e l a t e d t o wheel performance parameters
(s inkage, motion r e s i s t a n c e , drawbar p u l l , to rque) . Empir ical
c o r r e l a t i o n s thus e s t a b l i s h e d would probably provide as
reasonable a b a s i s as any a t p re sen t f o r p r e d i c t i o n of
performance, I f p o s s i b l e , s o i l p r o p e r t i e s should be i n t r o -
duced i n t o these c o r r e l a t i o n s by means of cone penetrometer
t e s t r e s u l t s . The tes t is s imple, t h e apparatus i s s imple,
and cone penetrometer measurements could e a s i l y be made i n
e a r l y Apollo missions a
b. For t h e long range, i n t e n s i f i e d e f f o r t s should begin now t o
develop an improved understanding of t h e mechanics of wheel-
s o i l i n t e r a c t i o n w i t h the u l t i m a t e o b j e c t i v e of t he formula-
t i o n of a r a t i o n a l theory f o r performance p r e d i c t i o n , Such
a theory should relate wheel c h a r a c t e r i s t i c s , loading condi t ions ,
s o i l p r o p e r t i e s and performance i n a c o n s i s t e n t manner. The
t a s k i s formidable and t h e r e s u l t may be i n a form so complex
t h a t it cannot be app l i ed i n a p r a c t i c a l manner. Nonetheless
t h e r e s u l t s would s t i l l serve t o focus a t t e n t i o n on (1) t h e
relative importance of va r ious v e h i c l e system f a c t o r s and
(2) t h e s o i l p r o p e r t i e s p e r t i n e n t t o s o l u t i o n of t he problem.
Such a s tudy should begin wi th an a n a l y s i s of the interdepen-
dent c h a r a c t e r of t h e stresses and deformations i n t h e wheel
and s o i l , Modern computation methods o f t e n make such ana lyses
p o s s i b l e using numerical techniques.
11. Somewhat conserva t ive design procedures i n d i c a t e t h a t 3 f e e t of l u n a r
s u r f a c e materials w i l l be a s u f f i c i e n t p r o t e c t i o n a g a i n s t r a d i a t i o n s ,
meteoroid bombardment, and temperature g rad ien t s f o r extended missions
on the l u n a r su r face , A reduct ion i n t h e above th ickness might r e s u l t
45
12.
13
from t h e u s e of much more s o p h i s t i c a t e d computational techniques
s t i l l t o be developed. Fu r the r experimental research would then
be d e s i r a b l e mainly i n t h e f i e l d of r a d i a t i o n s h i e l d i n g w i t h
s o i l s , and hyperve loc i ty impacts i n s o i l t o v e r i f y t h a t such
reduced th i cknesses are indeed adequate. It i s n o t f e l t however
t h a t such i n v e s t i g a t i o n s are w i t h i n t h e c a p a b i l i t i e s of t h i s
working group
Pos t Apollo development of t he moon w i l l r e q u i r e cons ide ra t ion of
s u r f a c e and subsur face s t r u c t u r e s i n rock (shal low and deep bore-
ho le s , s c i e n t i f i c s t a t i o n s , underground chambers f o r s t o r a g e and
waste d i sposa l , e t c . ) . Sound engineer ing w i l l achieve t h e optimum
r e s u l t s only i f based on in t ima te knowledge of t he modes of
mechanical behavior of t he materials involved. This must be
t r u e on the moon as i t i s on e a r t h . Hence, t h e r e i s a need f o r
de te rmina t ion of moon rock load-deformation c h a r a c t e r i s t i c s e A
borehole test appara tus should be developed f o r ope ra t ion on t h e
moon, It should be operable t o y i e l d both deformabi l i ty and
s t r e n g t h d a t a i f poss ib l e . Experimental and t h e o r e t i c a l work i s
needed t o provide t h e b a s i s f o r i n t e r p r e t a t i o n of s o i l and rock
f a i l u r e c h a r a c t e r i s t i c s from borehole tests , s i n c e t h i s c a p a b i l i t y
has no t y e t been developed on e a r t h . The most s u i t a b l e configura-
t i o n s of a test appara tus f o r l una r boreholes can be decided only
upon t h e b a s i s of the r e s u l t s of such work.
Continued i n v e s t i g a t i o n of t h e theory f o r f l u i d flow through porous
media i n vacuo is recommended, as w e l l as experimental work l ead ing
t o the design of a s u r f a c e probe f o r i n s i t u de te rmina t ion of t h e
permeabi l i ty of l u n a r s o i l s .
