LE

TECHNICAL REPORT M-71-10

PERFORMANCE OF THE BOEING LRV WHEELS IN A LUNAR SOIL SIMULANT

Report 2

EFFECTS OF SPEED, WHEEL LOAD, AND SOIL bY

K.-J. Melzer

December 1971

Prepared for George C. Marshall Space Flight Center

National Aeronautics and Space Administration, Huntsville, Alabama

Conducted by Mobility and Environmental Division

U. S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi

APPROVED FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED

TECHNICAL REPORT M-71-10

PERFORMANCE OF THE BOEING LRV WHEELS IN A LUNAR SOIL SIMULANT

Report 2

EFFECTS OF SPEED, WHEEL LOAD, AND SOIL

bY

K.-J. Melzer

December 1971

Prepared for George C. Marshall Space Flight Center

National Aeronautics and Space Administration, Huntsville, Alabama

Conducted by Mobility and Environmental Division

U. S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi

4RMY-MRC VICKSBURO. MISS

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

THE CONTENTS OF THIS REPORT ARE NOT TO BE USED FOR ADVERTISING, PUBLICATION, OR

PROMOTIONAL PURPOSES. CITATION OF TRADE

NAMES DOES NOT CONSTITUTE AN OFFICIAL EN-

DORSEMENT OR APPROVAL OF THE USE OF SUCH

,

COMMERCIAL PRODUCTS.

iii

The s tudy repor ted h e r e i n w a s conducted by personnel of the

Mobi l i ty Research Branch (MRB), Mobil i ty and Environmental (M&E) D i v i -

s i o n , U. S. Army Engineer Waterways Experiment S t a t i o n (WES). The

s tudy w a s sponsored by t h e Apollo Program Off ice , Nat iona l Aeronaut ics

and Space Adminis t ra t ion (NASA), Washington, D. C. , and w a s under the

t e c h n i c a l cognizance of D r . N. C . C o s t e s of t h e Space Sciences Labora-

t o r y and M r . E. B. George of t he As t r ion ic s Laboratory of the George

C. Marshal l Space F l i g h t Center , Huntsv i l le , Alabama. The work was

performed under NASA - Defense Purchase Request No. H-79205, da t ed

12 October 1970.

The tests w e r e conducted under t h e gene ra l supe rv i s ion of Messrs.

W. G. Shockley and S. J. Knight, Chief and A s s i s t a n t Chief , r e s p e c t i v e l y ,

of the M&E Divis ion , and under the d i r e c t superv is ion of M r . A. J. Green,

D r . K.-J . Melzer, and MAJ G. D. Swanson of t h e Research P r o j e c t s Group,

MRB. This r e p o r t w a s prepared by D r . Melzer.

Acknowledgment is made t o D r . D. R. F r e i t a g , A s s i s t a n t Technical

Director, WES, and M r . J. L. Smith, MRB, f o r t h e i r advice and a s s i s t a n c e

dur ing t h i s s tudy.

COL Ernest D. Pe ixo t to , CE, was Di rec to r of WES dur ing the conduct

of t h i s s tudy and p repa ra t ion of t h i s r e p o r t . M r . F. R. Brown w a s

Technica l Di rec tor .

V

CONTENTS

FOREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . NOTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . CONVERSION FACTORS. METRIC TO BRITISH UNITS OF MEASUREMENT . . SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . PART I: INTRODUCTION . . . . . . . . . . . . . . . . . . . .

Background . . . . . . . . . . . . . . . . . . . . . . . Purpose . . . . . . . . . . . . . . . . . . . . . . . . . Scope . . . . . . . . . . . . . . . . . . . . . . . . . .

PART 11: TEST PROGRAM . . . . . . . . . . . . . . . . . . . . Soil . . . . . . . . . . . . . . . . . . . . . . . . . . Test Equipment . . . . . . . . . . . . . . . . . . . . . Test Procedures . . . . . . . . . . . . . . . . . . . . . Data Presentation . . . . . . . . . . . . . . . . . . . .

PART 111: ANALYSIS AND DISCUSSION OF RESULTS . . . . . . . . Phase I (GM XIII): Effect of Wheel Speed. Wheel

Phase I1 (GM XV): Effect of Fender. Wheel Load. Acceleration. and Soil Type . . . . . . . . . . . . . . Wheel Speed. Direction of Chevron. and Soil Strength .

PART IV: CONCLUSIONS AND RECOMMENDATIONS . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . Recommendations . . . . . . . . . . . . . . . . . . . . .

LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . TABLES 1-8

Page V

ix

xi xiii

1 1 1 1 3

3 8 10 14 19

19

29 52

52 53 54

vii

NOTATION

C tr C

U

d

d50

D'

r

e

m a x

min G

h

h'

M

e M/Wr

M / W r x e P

PN

SP

PN 50

D

e

e

PN

pN20

PT/W

P/W

P /w r

r e r r r '

X

Cohesion determined from t renching tests, kN/m 2 ( p s i )

Coef f i c i en t of uniformity of t h e s o i l = d

Unloaded wheel diameter, CE (in.>

Grain diameter a t 50 percent f i n e r by weight , nxm ( i n . )

/d 60 10

e - e - max min

min Compac t i b ili t y , e

Relative d e n s i t y , % = 100 max min

I n i t i a l void r a t i o

Maximum void r a t i o

Minimum void r a t i o Pene t r a t ion r e s i s t a n c e g rad ien t , MN/m 3 (pc i )*

Unloaded wheel s e c t i o n height , cm ( i n . )

Loaded wheel s e c t i o n he ight , cm ( i n . )

Wheel to rque , m-N ( f t - l b )

Torque c o e f f i c i e n t , dimensionless

Value of M / W r a t a given s l i p x (e.g. 20 and 5 a )

P u l l (drawbar p u l l ) , N ( lb )

Power number Mw/Wva , dimensionless

Value of PN a t se l f -propel led p o i n t (P/W = 0)

Value of PN a t 20 percent s l i p

Value of PN a t 50 percent s l i p

P u l l c o e f f i c i e n t , dimensionless

Value of P/W when torque = 0

Value of P/W a t a given s l i p x (e.g. 20 o r 50%)

Unloaded wheel r a d i u s , cm ( i n . )

E f f e c t i v e wheel r a d i u s , cm ( i n . )

Ro l l ing r a d i u s of t h e wheel, cm ( i n . )

C o r r e l a t i o n c o e f f i c i e n t

e

*pc i = l b / i n . 3

i x

S Y * X

V

V a

W W

W

z

z SP z

X

a

Y

'd

yS 6

n

@S w

Standard e r r o r of estimate (s tandard dev ia t ion )

T r a n s l a t i o n a l ( ca r r i age ) speed, m/sec ( f t / s e c )

T r a n s l a t i o n a l (wheel) speed, m / s e c ( f t / s e c )

Moisture con ten t , % (percent of dry dens i ty )

Wheel load; weight , N ( l b )

Sinkage, c m ( i n .

Sinkage a t se l f -p rope l l ed p o i n t , cm ( i n . )

Sinkage a t a given s l i p x (e .g . 20 o r 50%), c m ( i n . )

Slope angle , deg

Wet dens i ty , g/cm ( p c i )

Dry dens i ty , g/cm (pc i )

S p e c i f i c g r a v i t y

Wheel d e f l e c t i o n , %

Eff ic iency Pva/Mw , dimensionless

Normal stress, kN/m ( p s i )

Angle of i n t e r n a l f r i c t i o n determined from i n s i t u p l a t e tests, deg

Secant f r i c t i o n angle determined from t r i a x i a l tests, deg

Ro ta t iona l v e l o c i t y of t h e wheel, r ad ians / sec

3

3

2

X

CONVERSION FACTORS

METRIC TO BRITISH UNITS OF MEASUREMENT

Metric u n i t s (S.1.) are used i n t h i s r e p o r t according t o NASA and

t h e Corps of Engineers r egu la t ions . However, i n the text and f i g u r e s

B r i t i s h u n i t s a l s o are given. Metric u n i t s used i n t h e t a b l e s contain-

i ng test r e s u l t s can be converted t o B r i t i s h u n i t s as fo l lows:

Mult iply By To Obtain

cen t ime te r s 0.3937 i nches

meters 3.2808 f e e t

newtons 0.2248 pounds ( fo rce )

kilonewtons per square meter 0.1450 pounds pe r square inch

meganewtons per cubic m e t e r 3.684 pounds per cubic inch

meter-newtons 0.7375 foot-pounds

grams pe r cubic cent imeter 62.43 pounds per cubic f o o t

x i

SUMMARY

Two n e a r l y i d e n t i c a l Boeing-GM w i r e - m e s h Lunar Roving Vehicle (LRY)

wheels w e r e l abo ra to ry t e s t e d i n a lunar s o i l simulant t o determine

t h e in f luence of wheel speed and acce le ra t ion , wheel load , presence

of a fender , t ravel d i r e c t i o n , and s o i l s t r e n g t h on the wheel performance.

Cons tan t -s l ip and t h r e e types of programmed-slip tests w e r e conducted

wi th the U . S . Army Engineer Waterways Experiment S t a t i o n single-wheel

dynamometer system.

T e s t r e s u l t s i nd ica t ed that performance of s i n g l e LRV wheels i n

terms of p u l l c o e f f i c i e n t , power number, and e f f i c i e n c y w e r e n o t

in f luenced by wheel speed and acce le ra t ion , travel d i r e c t i o n , t he presence

of a fender ,or wheel load.

s inkage , which increased w i t h increas ing load.

p u l l c o e f f i c i e n t and power number increased wi th inc reas ing s o i l s t r e n g t h .

However, f o r a given p u l l c o e f f i c i e n t o r s lope , s l i p w a s less i n f i rmer

s o i l ; t hus , t h e power number decreased and e f f i c i e n c y inc reased wi th

inc reas ing s o i l s t r e n g t h .

Of these v a r i a b l e s , only load inf luenced

For a given s l i p , t h e

x i i i

PERFORMANCE OF THE BOEING LRY WHEELS

I N A LUNAR SOIL SIMUTANT

EFFECT OF SPEED, WHEEL LOAD, AND SOIL

PART I: INTRODUCTION

Background

1. Following the award of a cont rac t t o the Boeing Company f o r

t he cons t ruc t ion of the manned Lunar Roving Vehicle (LRY), t he U. S .

Army Engineer Waterways Experiment S t a t i o n (WES), a t reques t of t he

George C. Marshall Space F l i g h t Center (MSFC), eva lua ted t h e r e l a t i v e

performance of s e v e r a l vers ions of t he b a s i c 81-cm (32-in.)-diam w i r e -

mesh wheels, which were f a b r i c a t e d by General Motors Corporation (GMC)

under c o n t r a c t w i th t h e Boeing Company. These tests were performed on

s o f t s o i l s ( f i n e sand, lunar s o i l simulant) (Green and Melzer, 1971a

and 1971b). Af t e r t h e f l i g h t wheel (50 percent chevron-covered) w a s

s e l e c t e d , t he MSFC requested the WES t o eva lua te i t s performance i n

terms of parameters not previously t e s t ed . The r e s u l t s of t hese inves-

t i g a t i o n s are repor ted here in .

Purpose

2. The purpose of t h i s test program w a s t o i n v e s t i g a t e the e f f e c t

of t h e fol lowing f a c t o r s on the performance of t he LRY wheel:

- a. - b . Presence of a wheel fender

- c. Wheel load

- d. S o i l

- e.

Wheel speed and acce le ra t ion

Forward and backward t r a v e l

Scope

3.

20 two-pass, single-wheel tests were conducted wi th a 50 percent

The test program was divided i n t o two phases. During phase I,

chevron-covered wheel (GM X I I I * ) wi thout a f ende r , which had been t e s t e d

during an e a r l i e r s tudy (Green and Melzer, 1971b).

s l i p , combined wi th cons t an t - s l ip , techniques w e r e used. Wheel speeds

ranged between 0.75 m/sec (2.5 ft/sec) and 3.14 m / s e c (10.3 f t / s e c ) , and

wheel acce le ra t ion between 0 and 0.78 m/sec2 (2.6 f t / s ec ).

load w a s 253 N (57 l b ) . The tests were conducted on a luna r soil simu-

l a n t (LSS) a t a consis tency des igna ted as LSS which, based on t h e

s o i l samples from t h e Apollo 11 and 12 f l i g h t s , w a s be l ieved t o be pre-

dominant on t h e luna r su r face . I n a d d i t i o n , a s m a l l amount of d a t a w a s

c o l l e c t e d during tests i n a dune sand t h a t exh ib i t ed a s l i g h t l y h ighe r

s t r e n g t h than LSS

Various programmed-

2 The wheel

4'

4 ' 4. During phase I1 of t h e program, 37 two-pass, single-wheel,

classical' ' programmed-slip tests w e r e conducted, a l s o wi th a 50 pe rcen t 1 1

chevron-covered wheel (GM XV*), which had b a s i c a l l y the same o v e r a l l

dimensions as t h e GM X I 1 1 wheel, bu t w a s s l i g h t l y s t i f f e r . Wheel speeds

ranged from 0.44 m/sec (1.4 f t / s e c ) t o 3.12 m/sec (10.2 f t / s e c ) w i t h no

wheel acce le ra t ion . Wheel loads ranged from 1 7 8 N (40 l b ) t o 377 N

(85 l b ) . Tests wi th and without a fender were conducted on LSS a t two

cons i s t enc ie s designated as LSS

l a t te r represent ing a h igh s o i l s t r e n g t h level t h a t could be expected on

t h e luna r sur face . I n a d d i t i o n , seven four-pass tests on LSS were

conducted with reversed chevron d i r e c t i o n t o s imula t e a wheel t r a v e l i n g

backward.

(21 tests) and LSS5 (16 t e s t s ) , t h e 4

4

* Numbers i n d i c a t e the number and sequence of t h e Boeing-GM wheels test- ed during the last 2-1/2 y e a r s a t t h e WES. The GM X I 1 1 had been used i n an e a r l i e r program, b u t w a s rep laced by t h e GM XV dur ing th i s program a t the request of NASA.

2

PART 11: TEST PROGRAM

Descr ip t ion

5. The LSS w a s t he same material as that used i n previous s t u d i e s

(Green and Melzer, 1971b). The dune sand used i n some of t h e phase I

tests w a s a f i n e sand from t h e deser t near Yuma, Arizona; it a l s o had

been used i n earlier programs (Fre i tag , Green, and Melzer, 1970a and

1970b; Green and Melzer, 1971a). Extensive tests were performed t o

determine t h e shear s t r e n g t h c h a r a c t e r i s t i c s and cone p e n e t r a t i o n

r e s i s t a n c e of bo th s o i l s . Gradation and c l a s s i f i c a t i o n d a t a , a long wi th

d e n s i t y and void r a t i o va lues , are given i n f i g . 1.

6. Based on the r e s u l t s of the s o i l mechanics tests fol lowing t h e

Apollo 11 and 12 missions (Costes , e t a l . , 1970; S c o t t , et a l . , 19711,

LSS appeared t o have the predominant s t r e n g t h cond i t ion of t he luna r

s o i l . Some i n d i c a t i o n s from t h e r e s u l t s of t h e Apollo 12 and 14 missions

( S c o t t , e t a l . , 1971; Mi tche l l , e t a l . , 1971) , however, made i t d e s i r a 6 l e

t o extend the range of s t r e n g t h l eve l s t e s t e d (LSS1, LSS2, LSS3, and

LSS4; very loose t o medium dense*) t o an even h ighe r s t r e n g t h level

des igna ted as LSS

cohesion) .

4

(medium dense t o dense, wi th e s s e n t i a l l y h igher 5

Prepa ra t ion

7. Both s o i l cond i t ions , LSS4 and LSS were prepared wi th w e t LSS 5’ a t average moisture con ten t s of 1.8 percent (k0 .2 percent ) and 1.9 per-

cen t ( 9 . 3 p e r c e n t ) , r e spec t ive ly .

test b i n s wi th water t o produce a s o i l w i th a nea r ly uniform d i s t r i b u t i o n

of mois ture . The mois ture conten t w a s he ld cons t an t by covering t h e test

b i n s when no t i n use and occas iona l ly spraying t h e s u r f a c e s l i g h t l y wi th

water t o compensate f o r evaporation.

The s o i l w a s thoroughly mixed i n t h e

The s o i l w a s processed i n p l ace

* For more d e t a i l e d d e s c r i p t i o n of t h e s o i l p r o p e r t i e s f o r t h e s e con- d i t i o n s , see Green and Melzer, 1971b.

3

3 N O

U N

c d c d a a a, aLl d L l 0 0 M u

befo re each test by plowing it with a seed f o r k t o a depth of 30 cm (12 in.) and applying compaction with a s u r f a c e v i b r a t o r u n t i l t he de-

s i r e d dens i ty w a s reached. During the t e s t i n g cyc le s , the uniformity

of t h e s o i l condi t ions w a s ensured by f requent de te rmina t ion of moisture

conten t and dens i ty and by measurements wi th t h e WES cone penetrometer.

The ranges of L S S 4 and LSS

are given i n t a b l e 1.

s o i l p rope r t i e s of i n t e r e s t i n t h i s s tudy 5

8 . A s o i l b i n wi th a i r -dry , dense Yuma sand (moisture conten t =

0.5 percent ) w a s used as an approach t o the test b i n of LSS.

c e r t a i n tests i n phase I of this program, a t h i r d s o i l b i n conta in ing

Yuma sand w a s placed a t t h e o t h e r end of t he L S S 4 bin .

tests,* the wheel encountered t h e following sequence of s o i l s :

sand--LSS --Yuma sand. It w a s no t intended t o create exac t ly the same

s t r e n g t h l e v e l f o r t he sand as f o r LSS

and v i b r a t i n g it twice wi th a sur face v i b r a t o r , it w a s p o s s i b l e t o

a t t a i n a sand s t r e n g t h l e v e l ( i n terms of pene t r a t ion r e s i s t a n c e ) t h a t

came c l o s e t o t h a t of L S S 4 . The uniformity of t he sand w a s ensured by

measurements with the .WES cone penetrometer. The ranges of s o i l prop-

erties of i n t e r e s t are given i n t a b l e 1.

S o i l tests

During

During these

Yuma

4 however, by screeding the sand 4 ;

9. Cone pene t r a t ion r e s i s t ance . The s tandard WES mechanical cone

penetrometer w a s used throughout t h i s s tudy t o measure the pene t r a t ion

r e s i s t a n c e gradien t G (Fre i tag , Green, and Melzer, 1970a). During the

single-wheel tests in phase I, G was usua l ly determined a t three po in t s

along the cen te r l i n e of an LSS test s e c t i o n (length:’7 m; e 2 2 f t ) p r i o r

t o t e s t i n g ( t a b l e s 1 and 2) . Three a d d i t i o n a l pene t r a t ions were made

25 cm (10 i n . ) t o t he l e f t and 2 5 cm t o t h e r i g h t of t he c e n t e r l i n e .

Three cen te r - l i ne pene t r a t ions a l s o were made a f t e r completion of t he

f i r s t pass and a f t e r t h e last pass of a test.

of t h e above-mentioned pene t r a t ions was increased from t h r e e t o f ive.

However, i n t he las t 12 tests of the program (No. 71-094-6 t o 71-105-6),

* These tests served t o check whether c e r t a i n in f luences observed i n

I n phase 11, the number

tests on LSS were a l s o p re sen t i n t e s t s on sand (paragraph 33) .

5

penet ra t ions were no t conducted after completion of the f i r s t pass .

Maximum, minimum, and average

i n t a b l e 2 .

G va lues f o r each test are summarized

10. During the tests i n phase I i n which Yuma sand w a s placed

about 3.0 m (10 f t ) be fo re and a f te r t h e LSS l ane , f o u r p e n e t r a t i o n s

were conducted i n the sand be fo re t r a f f i c ( t a b l e s 1 and 3), a f t e r com-

p l e t i o n of t h e f i r s t pass , and a f t e r traffic.

average

M a x i m u m , minimum, and

G va lues f o r each test are l i s t e d i n t a b l e 3.

11. A s has been poin ted out i n t h e r e fe rences a l r eady c i t e d , rela-

t i o n s between g rad ien t G and dry d e n s i t y Yd were e s t a b l i s h e d and

used as c a l i b r a t i o n diagrams t o determine t h e dry d e n s i t y and t h e rela-

t i v e dens i ty of t h e t e s t lanes . The r e l a t i o n between G and Y d f o r

LSS a t a moisture conten t of 0 .8 percent ( f i g . 2) had a l r eady been de te r -

mined; whereas the r e l a t i o n f o r a mois ture conten t of 1.8 pe rcen t , which

o r i g i n a l l y covered only a dens i ty range of 1 .48 g/cm

1.57 g/cm (98.0 l b / f t ), w a s extended t o 1 .78 g/cm

( f i g . 2 ) .

dens i ty of t h e Yuma sand test lanes . Minimum, maximum, and average

va lues of dry d e n s i t y and relative d e n s i t y be fo re t r a f f i c f o r t he var-

ious s o i l condi t ions t e s t e d are l i s t e d i n t a b l e 1.

3 3

3 3 3 3 (92.5 l b / f t ) t o

(111.0 l b / f t )

Exis t ing r e l a t i o n s w e r e used t o determine d e n s i t y and re la t ive

12. Moisture conten t and d e n s i t y de te rmina t ions . The s u r f a c e

moisture content of t h e LSS w a s determined i n a l l tests be fo re and af ter

t r a f f i c , except i n a few cases. I n a d d i t i o n , d e n s i t y and bulk mois ture

conten t were occas iona l ly determined by means of a d e n s i t y box.

one o r two measurements w e r e made be fo re and a f t e r t r a f f i c . Minimum,

maximum, and average va lues of s u r f a c e mois ture conten t and d e n s i t y are

given i n t ab le s 1 and 2.

Usual ly ,

13. Shear s t r e n g t h parameter. Angles of i n t e r n a l f r i c t i o n based

on vacuum t r i a x i a l and i n s i t u p l a t e shear tests were determined f o r LSS

and Yuma sand cond i t ions from r e s u l t s of the earlier s t u d i e s .

va lues f o r the va r ious s o i l cond i t ions are g iven i n t a b l e 1.

Average

14. Cohesion, based on t renching tests, w a s determined as i n t h e

previous test programs. A few t renching tests were conducted f o r s o i l

6

r( t) a

300

--- 7 nn

100 80

60

40

20

10 8

6

4

3

2

1.0

0.8

0.6

0.4

0.3

a Rela t ive Density Dr , % z- . .

10 20 30 40 50 60 70 8( I I 1 I I I I

--

yd i n g/cm3; G i n p s i f i n . 5 0 . ( 1 y d = 1,380 + 0,237 log G

4 -IC' = 0.991

I M o i s t u r e ConteI

I I

I - ! 1 _~____ + 0.152 log G

90 100 I z

'd Dry Density,

F ig . 2. Re la t ions among cone pene t r a t ion r e s i s t a n c e g r a d i e n t , d ry d e n s i t y , r e l a t i v e dens i ty , and mois ture conten t f o r

t h e lunar s o i l simulant (from mold t e s t s ) . 7

cond i t ion LSS which had not been t e s t e d before . Average cohesion

va lues f o r t h e va r ious s o i l cond i t ions are given i n t a b l e 1. 5 '

T e s t Equipment

Dynamometer

15. The dynamometer system used i n these tests ( f i g . 3) can

accommodate loads from approximately 67 N (15 l b ) t o 900 N (200 l b ) ,

and wheels ranging from about 45 c m (18 i n . ) t o 1 1 4 cm (45 i n . ) i n

diameter . The system is equipped wi th ins t rumenta t ion f o r continuous

mea'surements of wheel load , p u l l , to rque , s inkage (hub movement),

c a r r i a g e speed, and wheel speed. For more d e t a i l e d d e s c r i p t i o n see

Report 1 i n this series (Green and Melzer, 1971b).

Recording systems

16. The primary d a t a record ing system w a s an on-l ine d i g i t a l

computer. With t h i s system t h e e lec t r ica l (analog) s i g n a l s reach t h e

computer i n a r a w form wi th no s i g n a l condi t ion ing . The s i g n a l s are

converted to d i g i t a l form by t h e computer and s t o r e d on magnetic t ape

f o r subsequent d a t a processing. A l t e r n a t i v e l y , t h e analog s i g n a l s can

be recorded on t ape and d i g i t i z e d la ter . This a l t e r n a t i v e w a s used

i n phase I1 of t h e program. The es t imated accuracy of t he system is

3 t o 4 percent .

1 7 . A secondary record ing system w a s a 36-channel, d i r ec t -wr i t i ng

osc i l lograph , which r e q u i r e s s i g n a l condi t ion ing . This secondary system

a f f o r d s the test engineer an oppor tuni ty t o t ake a quick look a t t h e

d a t a as required t o assist i n planning subsequent tests and t o r a p i d l y

determine whether a l l c i r c u i t s are func t ion ing proper ly f o r a g iven

test.

used and the e x p e r t i s e of t h e reader . Resu l t s ob ta ined wi th t h i s system

are est imated t o be accu ra t e w i t h i n 6 t o 8 percent . Only r e s u l t s

ob ta ined from t h e primary record ing system were used i n the a n a l y s i s .

For more de t a i l ed d e s c r i p t i o n of t h e two systems see Report 1 of t h i s

series (Green and Melzer, 1971b).

The accuracy of t he osc i l l og raph readings depends on t h e scale

8

T e s t wheels

18. Two nea r ly i d e n t i c a l wire-mesh wheels w e r e t e s t e d : t h e 82.2-

cm (32.4-in.)-diam GM XI11 during phase I, and the 81.5-cm (32.1-in.l-

diam GM XV during phase 11. Both wheels had a 50 percent chevron-tread

cover.

t h e same s t a t i c loading cond i t ions on a hard su r face . Wheel d a t a are

given i n t a b l e 4.

The GM XI11 w a s s l i g h t l y more f l e x i b l e than t h e GM XV under

T e s t Procedures

Phase I (GM XIII)

19. Three d i f f e r e n t test techniques were used dur ing t h i s phase

of t h e program:

- a. C l a s s i c a l programmed-slip (CPS), i d e n t i c a l t o t h e

- b . Ramped-slip (RS)

- c , Modified programmed-slip ( M P S )

programmed-slip technique used i n t h e earlier s t u d i e s

These t h r e e test techniques, which are descr ibed i n the fo l lowing para-

graphs, w e r e used t o i n v e s t i g a t e p r imar i ly whether t h e wheel accelera-

t i o n inf luenced t h e wheel performance. A secondary purpose w a s t o check

whether using d i f f e r e n t test techniques would g e n e r a l l y in f luence t h e

outcome of the tests. The test cond i t ion s imula t ing t h e re la t ive motion

of an a c t u a l v e h i c l e wheel would be between the CPS and t h e M P S modes.

20. CPS test. The CPS test technique w a s used i n f i v e tests

during phase I. The test w a s s t a r t e d wi th t h e wheel i n t h e nega t ive

s l i p range ( f i g . 4a) , i .e . t h e t r a n s l a t i o n a l speed of t h e c a r r i a g e (va>

w a s g r e a t e r than t h a t (v ) of t h e wheel. The c a r r i a g e w a s slowed a t

a programmed, uniform rate (wheel speed w a s approximately cons t an t during

t h e test) t o cause the wheel t o pass through t h e towed cond i t ion ( to rque

M = 0 ) , t h e zero percent s l i p cond i t ion ( c a r r i a g e speed = wheel speed) ,

t h e se l f -propel led condi t ion ( p u l l P = 0 ) , e tc . , as s l i p p rogres s ive ly

increased up t o 90 pe rcen t , and i n some i n s t a n c e s t o 100 percent (car-

r i a g e speed = 0) . Wheel speeds w e r e changed from test t o test , covering

a range from 1.5 m/sec (4.9 f t / s e c ) t o 3.0 m / s e c (9.9 f t / sec) . Wheel

W

10

a 9) Q) c cn

'. Wheel Speed \ \

Car r i age Speed \

a. CPS test -

Wieel Speed i I--.-.-- - ....---.-- a

a Car r i age Speed

b. RS test

T i m e

- -Bm- -- __ - I - .____

\Theel Speed

- --lc- T S S +!-f+k Sand -bi

- _. - - -- - -_ --- - _ _

Trans 1 t ion Transd t ion

C. MPS test - Fig . 4 . Speed-time r e l a t i o n s f o r d i f f e r e n t test techniques

11

acce le ra t ion was zero (w w a s c o n s t a n t ) , and c a r r i a g e a c c e l e r a t i o n v a r i e d 2 2 2

from test t o test between -0.07 m / s e c (0.23 f t /sec ) and -1.14 m / s e c 2 (3.74 f t / s e c )* ( t a b l e 5). Wheel load w a s cons tan t (253 N; 57 l b ) in

a l l tests during phase I.

d a t a from th ree CPS tests conducted i n a n earlier program (Green and

Melzer, 1971b) on LSS4 a t wheel speeds of 0.75 m / s e c (2.5 f t / s e c )

( t a b l e 5).

Also included i n the a n a l y s i s w e r e t h e average

21. RS test. The RS test technique w a s used in seven tests dur ing

phase I.

speed held cons tan t ( f i r s t cons t an t - s l ip po r t ion of t h e test, f i g . 4b).

A f t e r t h e wheel had en te red t h e LSS test l ane and had t r a v e l e d f o r 1 m

(3.3 f t ) o r more, t h e wheel speed w a s increased a t a r e l a t i v e l y s m a l l

rate ("ramped s l i p " ) , which l e d t o a s l i g h t i nc rease i n s l i p (about 7 t o

9 percent ) . Af t e r t h i s , t h e wheel speed w a s kept cons t an t , w i th t h e

wheel t r ave l ing on LSS and subsequent ly on sand (second cons t an t - s l ip

p o r t i o n of t h e test) . S l i p during t h e RS tests ranged from -17 t o

+15 percent. The c a r r i a g e speed, which w a s he ld cons t an t during a spe-

c i f i c test, w a s changed from test t o test wi th in a range from 1.50 m/sec

(4.9 f t / s e c ) t o 3.45 m/sec (11.3 f t / s e c ) ( t a b l e s 5 and 6). The wheel

speed w a s var ied over a t o t a l range from 1.56 m/sec (5.1 f t /sec) t o 2 3.14 m/sec (10.3 f t / s e c ) , w i th a c c e l e r a t i o n s between 0.19 m/sec

(0.62 ft /sec ) and 0.36 m/sec (1.18 f t /sec ).**

A test w a s s t a r t e d i n t h e sand test l a n e w i t h wheel and c a r r i a g e

2 2 2

22. MPS test. The MPS test technique w a s used i n e i g h t tests

during phase I. Whereas t h e emphasis i n t h e RS tests w a s on the constant-

s l i p por t ions , which w e r e connected by t h e ramped-slip p o r t i o n , t h e

emphasis i n t h e MPS tests ( f i g . 4c) w a s on t h e a c c e l e r a t i o n of t h e wheel

over a l a r g e r range of s l i p . A s i n the case of t h e RS tests, a test w a s

s t a r t e d at cons tan t s l i p i n t h e sand test lane . Constant s l i p w a s main-

ta ined t h e r e a f t e r u n t i l t h e wheel had t r ave led f o r 1 m (3.3 f t ) o r more

* The test l a n e w a s r e l a t i v e l y s h o r t , e s p e c i a l l y f o r the tests a t h igh speeds, which r e s u l t e d i n the r e l a t i v e l y l a r g e range of d e c e l e r a t i o n .

** This was t h e l a r g e s t a c c e l e r a t i o n t h a t could b e recorded i n t h i s spe- c i f i c t e s t series because of t ime-se t t ing limits of t h e speed c o n t r o l s ys t em.

12

on t h e LSS (first cons t an t - s l ip po r t ion of t he test) . The rea f t e r , t h e

wheel speed w a s increased ( ca r r i age speed w a s h e l d cons tan t ) i n a f a sh ion

t h a t r e s u l t e d i n a cons iderable inc rease i n s l i p (minimum a b s o l u t e in-

crease of s l i p w a s 20 percent ; maximum abso lu te i n c r e a s e w a s 88 pe rcen t ) .

A f t e r t h e maximum wheel s l i p was a t t a i n e d f o r a given test, the wheel

$peed w a s kept cons t an t , w i t h the wheel t r a v e l i n g on LSS and subsequent ly

on sand (second cons t an t - s l ip por t ion of the test) .

s t r i c t e d l eng th of t he LSS l ane , cons tan t -s l ip d a t a on LSS could be

recorded f o r only t h e f i r s t cons tan t -s l ip po r t ion of t h r e e tests and f o r

t h e second cons t an t - s l ip po r t ion of two tests ( t a b l e 5).

Because of t h e re-

23. The t o t a l s l i p range covered i n the MPS tests w a s from -24 t o

+69 percent . The c a r r i a g e speed, which w a s he ld cons t an t dur ing a

s p e c i f i c test , w a s changed from test t o test wi th in a range from

0.89 m / s e c (2.9 f t / s e c ) t o 3.14 m/sec (10.3 f t / s e c ) ( t a b l e 5). Wheel

speeds ranged from 0.76 m/sec (2.5 f t / s e c ) t o 3.14 m/sec (10.3 f t / s e c ) , 2 2 wi th a c c e l e r a t i o n s between 0.25 m/sec2 (0.82 f t l sec ) and 0.78 m / s e c

(2.56 f t / s e c ).

Phase I1 (GM XV)

2

24. The CPS technique (paragraph 20) w a s used dur ing 44 tes ts of

t h i s phase of t h e program. Thirty-seven of t hese tests w e r e conducted

as two-pass tests (21 tests on LSS4, t a b l e 7 ; 16 tests on LSS5,

t a b l e 8). The speed ranged from 0.44 m / s e c (1.4 f t / s e c ) t o 3.12 m/sec

(10.2 ft/sec),* wi th wheel a c c e l e r a t i o n zero and c a r r i a g e a c c e l e r a t i o n 2 2 2 2 ranging from -0.06 m / s e c (0.20 ft/sec ) t o -1.60 m/sec (5.25 f t / s e c ).

Wheel loads ranged from 178 N (40 l b ) t o 377 N (85 l b ) , embracing t h e

minimum and m a x i m u m LRV wheel load t o be a n t i c i p a t e d on t h e luna r sur-

face due t o load t r a n s f e r , including t h e f i n a l nominal load of 289 N

(65 lb) .** Seven (six on LSS4 and one on LSS of t h e s e 37 tests w e r e 5

* This range covered the speeds a t which the LRV w a s t o travel during t h e Apollo 1 5 mission.

** The nominal l oad had t o b e changed dur ing t h e program from 253 N (57 l b ) t o 271 N (63 l b ) , and f i n a l l y t o 289 N (65 l b ) because of changes i n the payload of the LRV.

13

conducted without t h e fender . During the f i r s t pas ses of t he o t h e r

30 tests, the r i g h t - f r o n t fender w a s a t t ached t o t h e wheel, and dur ing

t h e second passes , t h e r igh t - r ea r fender w a s a t t ached t o t h e wheel, t hus

s imula t ing the r igh t -pa th performance of the LRV.

25. I n seven a d d i t i o n a l four-pass tests on LSS t h e wheel w i th 4’ fender w a s t e s t e d w i t h reversed chevron d i r e c t i o n t o s imula te backing-

o f f and c ra t e r - ex t r i ca t ion maneuvers. I n t h e s e tests the fender

sequence was as fol lows:

a. Pass 1: Rear fender

- b. Pass 2: Front fender

c. Pass 3: Rear fender

- d. Pass 4 : Front fender

Thus, t h e average parameters of passes 1 and 2 represented the perform-

ance of t he LRV backing i n t o undis turbed s o i l , and the average parameters

of passes 3 and 4 represented t h e performance of t h e LRV backing in i t s

own r u t s . Wheel loads during these tests w e r e 178 N (40 l b ) , 253 N

(57 l b ) , and 377 N (85 l b ) . The average wheel speed during t h e s e tests

w a s 0.75 m/sec (2.5 f t / s e c ) .

-

-

Data P resen ta t ion

CPS tests

26. The r e l a t i o n s of p u l l and torque t o s l i p can be shown by two

p l o t s , such as those i n f i g . 5 , which r ep resen t t h e average r e l a t i o n s *

of t h e phase I tests. The p u l l c o e f f i c i e n t P/W and the torque c o e f f i -

c i e n t M / W r increased a t a decreased rate a f t e r a s l i p of about 20 per-

cen t had been reached. General ly , t hese r e l a t i o n s ag ree wi th t h e

r e l a t i o n s found f o r a l l Boeing-GM wheels t e s t e d on LSS. The average

- Ja r i a t ion of t h e power number PN (Mw/Wva) ve r sus p u l l c o e f f i c i e n t

e

* I n t h e framework of t h i s s tudy , t h e s e r e l a t i o n s w i l l not be presented s e p a r a t e l y f o r each tes t , as w a s done i n earlier s t u d i e s . each test have been furn ished t o MSFC cont inuous ly dur ing t h e time t h e tes ts were conducted. I n a d d i t i o n , complete copies of t h e computer pr in t -outs .bf a l l tests w e r e s e n t t o MSFC on 19 February 1971 (phase I) and on 28 June 1971 (phase 11).

P l o t s f o r

14

P/W and s l o p e angle

(e.g. f i g . 6 f o r phase I ) , under the assumption t h a t t h e p u l l c o e f f i c i e n t

measured a t a given s l i p on a level surface wi th a s i n g l e wheel is

roughly equiva len t t o t h e tangent of t h e ang le of t h e s lope t h a t a four-

wheeled v e h i c l e equipped w i t h s imi l a r wheels can climb. The PN ve r sus

P/W r e l a t i o n is e s p e c i a l l y important, because i t expresses the energy

consumed pe r u n i t of d i s t a n c e of t r a v e l pe r u n i t wheel load o r v e h i c l e

weight i n r e l a t i o n t o p u l l o r slope-climbing a b i l i t y ,

conforming t o a c e r t a i n P/W , o r s lope , t h e corresponding PN is read

and m u l t i p l i e d by t h e wheel load o r v e h i c l e weight i n newtons and t h e

f r a c t i o n 1000/3600.

~1 , f o r a large number of tests is a l s o presented

To o b t a i n whr/km

27. For each test t h e r e l a t i v e performance of t h e wheels t e s t e d

w a s a s ses sed from d a t a ( i n parentheses below) obta ined under t h e follow-

ing cond i t ions ( f i g s . 5 and 6 ; t ab l e s 5, 7, and 8):

- a. b. Self-propel led condi t ion (PN ; s l i p )

Towed cond i t ion (PT ; s l i p )

SD - - c. 20 percent s l i p (P20/W ; M20/Wre ; PNZ0)

d. 50 percent s l i p (P /W ; M50/Wre ; PN50) 50 -

I n a d d i t i o n t o t h e s e parameters, the wheel hub movement, which is a

measure of t h e wheel s inkage i n t o t h e s o i l , w a s recorded.

28. I f a more d e t a i l e d assessment of t h e in f luence of a c e r t a i n

v a r i a b l e (e.g. wheel speed) w a s necessary, t h e a n a l y s i s w a s based on a

comparison of t h e fol lowing performance parameters: power number PN

and s inkage z a t t h e se l f -propel led cond i t ion ( p u l l = 0) ; and p u l l

, power number PN20 , and s inkage z f o r t h e c o e f f i c i e n t P20/W

20 pe rcen t s l i p condi t ion . These two cond i t ions were s e l e c t e d because

(a) t h e se l f -p rope l l ed condi t ion corresponds t o the LRV t r a v e l i n g on

level ground, and (b) t h e 20 percent s l i p condi t ion corresponds approxi-

mately t o t h e maximum s l o p e the LRV can climb i n a s t eady- s t a t e cond i t ion

b e f o r e power consumption rates become excessive. The same procedure w a s

a l s o used whenever d a t a from RS or MPS tests were included i n a s p e c i f i c

a n a l y s i s .

SP

SP 20

15

-/o

I

I I

- 18

(I] u (I] a! U

(A PI U

u W

d .rl U

!

- -

0 0 0 o m

0 d I

rn rl I

2uar3r33

3 n

7 0

3

n . ?

n 9

3 9

trl Ln

0 ln

M n : .2

rl

o m U

n TI

0 m

VI r 4

0 N

.ln d

.O d

in

16

Slope Angle a , deg 0 5 10 15 20 25 30 35

Average from CPS Tes t s - I

V a r i a t i o n

0.2 0.4 0.6 TP P u l l C o e f f i c i e n t P/W

-0.2 \ 0

LEGEND

Q- RS Tests 0- MPS T e s t s Open symbols: cons tan t -s l ip

p a r t of test Closed symbols : programed-

s l i p p a r t of test

F ig . 6. Relations of power number t o p u l l c o e f f i c i e n t and

wheel under 253-N (57-lb) load on LSS4 (1st and 2d passes)

s l o p e a n g l e from three tes t techniques; GM XI11

1 7

RS and M P S tests

29. Average va lues of p u l l and torque c o e f f i c i e n t s , t oge the r wi th

power numbers and va lues of s inkage and s l i p , w e r e recorded f o r both

cons tan t -s l ip po r t ions of t h e tests (see paragraphs 21 and 22) whenever

they were included ( t a b l e s 5 and 6 ) . Each of t hese averages w a s calcu-

l a t e d from at least 20 d a t a p o i n t s , one f o r each 5-cm (2-in.) l eng th of

test lane . S igna ls c o l l e c t e d w i t h i n the t r a n s i t i o n zones from sand t o

LSS ( f i g s . 4b and 4c) w e r e n o t included i n t h e averages.

cons tan t -s l ip po r t ions w a s no t included, which w a s the case i n most of

t h e M P S tests (paragraph 2 2 ) , the performance parameters f o r t he lowest

and h ighes t s l i p s during t h e test w e r e recorded. I n a d d i t i o n , perform-

ance parameters f o r t he towed and t h e se l f -p rope l l ed cond i t ions and f o r

20 and 50 percent s l i p s w e r e included ( t a b l e 5) whenever t h e wheel

passed through one o r more of t h e s e p o i n t s .

If one of t h e

18

PART 111: ANALYSIS AND DISCUSSION OF RESULTS

Phase I (GM XIII): Effect of Wheel Speed, Wheel Accelera t ion , and S o i l Type

Wheel speed

30. P l o t s of t h e t h r e e b a s i c r e l a t i o n s , P/W ve r sus s l i p , M / W r e

ve r sus s l i p , and PN ve r sus P/W , obta ined from the CPS tests, ind i -

ca t ed no observable e f f e c t of wheel speed on the test r e s u l t s . The three

average r e l a t i o n s wi th t h e i r maximum v a r i a t i o n s a t f o u r characteristic

points--towed (TP), s e l f -p rope l l ed poin t (SP), 20 percent s l i p , and

50 percent s l ip - -a re shown i n f i g s . 5a , 5b, and 6. These f i g u r e s con ta in

a l s o r e s u l t s from t h e cons t an t - s l ip p o r t i o n s of t h e RS and MPS tests, f o r

d i f f e r e n t wheel speeds. The d a t a po in t s f a l l w e l l w i th in the dev ia t ions

of t h e r e l a t i o n s obta ined from t h e CPS tests. From these t r ends , i t w a s

concluded t h a t t h e mob i l i t y performance c h a r a c t e r i s t i c s of t h e wheels

t e s t e d w e r e no t a f f e c t e d by e i t h e r t he mode of t e s t i n g (CPS, RS, o r M P S ) ,

o r t h e wheel speed.

31. To examine the e f f e c t of wheel speed more c l o s e l y , t h e perform-

ance parameters f o r t h e se l f -propel led cond i t ion PN and z (open

circles i n f i g . 7), and f o r 20 percent s l i p

(open c i r c l e s i n f i g s . 7 through 9) from the CPS tests w e r e p l o t t e d

ve r sus wheel speed. Within the range of speeds t e s t e d , t h e performance

parameters w e r e p r a c t i c a l l y cons tan t , i .e . independent of wheel speed.

Wheel a c c e l e r a t i o n

SP SP p20/w , 220 Y and PN20

32. The e f f e c t of wheel acce le ra t ion on the mob i l i t y performance

c h a r a c t e r i s t i c s of t h e wheels t e s t ed w a s assessed i n t h e same manner

as t h e in f luence of wheel speed. Performance parameters a t 20 percent

and 50 percent s l i p from t h e MPS t e s t s (programmed-slip po r t ion of t h e

tests) were compared wi th the th ree average b a s i c performance r e l a t i o n s

( f i g s . 5a, 5b, and 5c) from the CPS tests; t h e M P S test r e s u l t s f a l l

w i t h i n the range of t h e CPS test r e s u l t s . Fu r the r , the performance

parameters of t h e M P S tests f o r the se l f -propel led condi t ion and f o r

20 pe rcen t s l i p w e r e p l o t t e d ( together w i th t h e CPS tests performance

19

0 rl

0

al M 2

U aJ m \ u w 0

-I d' 0

- c o ! I

I 0"

;NO I

N " O

d s 0 0

Nd

n n n k h l h l h l o O O u w a J a J a J m m m m \ \ \ u u u u m w w w a J u O Q " . . . w

d aJ c) c) (d

0

u (d

cn Pi u

r(

m

I 6-l d I e

I

I I

I ;

p b d I

I 2

I I I I ? l o I 1

I

a a, aJ a m " aJ a, c 3

: m k P) 3

c C

N a J d G a l 3 a J s H 3 0

H a J H O H

3 % 28 w H C

h

M .d Fr

.

20

rl

rl bo

NO

4 rl U

I ml

9 I I I I I

h

U N 0

V

m \ e

0

m

In

N , .

0

N . .

Ul

4 ..

0

4 - .

v, .O

0

a a, a, a m rl al c B

0; t

I 7hrl I

u a, m \ U w

0 rl

a

W

01 N

! I

0 1 In 0

V a, m \ e

9 m

In

N

0

N

a al a

I n m A ;

i

9 "

In

0

0

'cl a, al a m " a, GI

42 3

Y m Ll a, ? 0 N

N

i t

i rl In 0 4

N

0

I

I I 4 1 I

I I I I I I I

rlrl

7 ’

rl m - a m a r l c 3 E

.L rl a 9-l .rl 0 r l v ) m

.L

s u o a

G O H

al M

= ( d m & I

a, Mrd *rl I%

22

parameters) versus the corresponding wheel speeds (closed symbols i n

f i g s . 7 through 9 ) , f o r t h r e e acce le ra t ion l e v e l s . The r e s u l t s of t h i s

a n a l y s i s show ( f i g s . 7 through 9) no in f luence of wheel a c c e l e r a t i o n

on t h e performance parameters under cons idera t ion . I n a d d i t i o n , t h e

data f r o m the Ei?S tests confirm Ehe conciusion drawn above (paragraph 3wj,

t h a t , w i t h i n t h e range of wheel speeds t e s t e d , t h e performance parameters

considered w e r e p r a c t i c a l l y independent of wheel speed.

S o i l type

33. P u l l and torque c o e f f i c i e n t s r e s u l t i n g from t h e cons t an t - s l ip

p o r t i o n s of t h e RS and MPS tests on Yuma sand ( t a b l e 6) w e r e p l o t t e d

versus s l i p f o r t h r e e d i f f e r e n t wheel speeds ( ind ica t ed by d i f f e r e n t

symbols i n f i g s . 10a and lob ) . I n the p o s i t i v e s l i p range, only d a t a

from t h e two h igher speed levels were a v a i l a b l e ; t h e r e s u l t s at bo th

speeds can be represented by one r e l a t i o n , because t h e l i m i t e d amount

of d a t a d id no t i n d i c a t e any considerable sepa ra t ion by wheel speed.

I n a d d i t i o n , t he P/W and M/Wre r e l a t i o n s are shown i n f i g s . 10a and

10b f o r a CPS test from an earlier program conducted wi th a s imilar wheel

(GM VII I ) under nea r ly the same load on Yuma sand a t approximately t h e

same s o i l s t r e n g t h , b u t a t a wheel speed of 0.9 m/sec (2 f t / s e c ) . These

d a t a allowed the fol lowing, a t least q u a l i t a t i v e , comparison between t h e

performance of t he wheels on sand and on LSS:

LSS4* 1.0 0.75-3.00 0.10 0.35 0.41 0.45 0.55

Sand 1.3 0.90 0.12 0.34 0.47 0.42 0.63 Sand 1.3 1.40-3.00 0.06 0.43 0.47 0.59 0.65

*Performance parameters f o r LSS a r e independent of speed. 4

34. This comparison shows t h a t t h e wheel on sand a t a speed of

0.9 m/sec (3.0 f t / s e c ) performed approximately t h e same as the wheel on

LSS a t a l l speeds under cons idera t ion ( inc luding 0.9 m/sec; 3 f t / s e c ) ,

a l though t h e e f f i c i e n c y i n LSS seemed t o be s l i g h t l y h igher than i n

sand (less inpu t a t t h e same output ) . However, i t can be concluded t h a t ,

f o r n e a r l y t h e same s t r e n g t h l e v e l , t he wheels hehaved more-or-less t h e

4

4

2 3

[I) U rn al H

a .d rl (/3

U

h

03

0

. . . . orlhl

\ \ \ \ \

u I

I I I

I

I

\ '

u3 e hl

0 0 0

0 Q

0 v',

0 'cu

0 4

Q

m

w i d W C n

3 .e a a cd

G O 0 4

2 0 w H c

cd 0 rl

bo .d Frr

n

$ m

\ \

a3 \o

0 0

d

0

cv 0

3 N

3 --I

I

.L

d al 2 5 H H H x

. . .L .

n 0 rl

25

Same i n the two d i f f e r e n t s o i l s when t h e wheel speed w a s 0.9 m/sec

( 3 f t / s e c ) . On t h e o t h e r hand, when t h e wheel speed i n sand exceeded

1.4 m/sec (4.6 f t / s e c ) , the power requirements f o r t h e se l f -p rope l l ed

condi t ion decreased, and the system output increased a t the same inpu t

as f o r 0.9 m / s e c (3.0 f t / s e c ) . Thus, t h e o v e r a l l e f f i c i e n c y i n sand

increased wi th inc reas ing wheel speed, which is con t r a ry t o t h e per-

formance in LSS4, where t h e performance parameters w e r e found t o be

independent of wheel speed.

i n t h e following paragraphs. * A q u a l i t a t i v e explana t ion f o r t h i s is given

35. Recent i n v e s t i g a t i o n s wi th pneumatic tires i n sand (Turnage,

1972) showed an inc rease i n p u l l a t a given s l i p wi th an inc rease i n

wheel speed.

f o r higher s l i p s than f o r lower. A q u a l i t a t i v e t h e o r e t i c a l explana t ion

f o r t h i s phenomenon w a s given earlier by Leflaive and Wiendieck (19651,

who found t h a t t h e angle of i n t e r n a l f r i c t i o n (o r t h e "shear po ten t i a l " )

of t h e cohesionless s o i l w a s independent of speed, which i s a w e l l -

known f a c t from classical s o i l mechanics. Therefore , a t h e o r e t i c a l

explanation of t h e observed speed dependence of p u l l w a s not sought i n

a poss ib l e v a r i a t i o n of t h e p e r t i n e n t s o i l parameters. However, con-

t r a r y t o most convent ional s o i l t e s t i n g dev ices , a moving wheel is

cons tan t ly i n touch wi th f r e s h s o i l masses t o which a c e r t a i n momentum

is communicated by t h e wheel ac t ion . The s o i l momentum pe r u n i t of

time w a s then considered t o r ep resen t an a d d i t i o n a l dynamic f o r c e a c t i n g

on t h e wheel-soil system. This f o r c e can be reso lved i n t o a h o r i z o n t a l

component, which acts i n t h e same d i r e c t i o n as p u l l does, and i n t o a

ver t ical component, which acts i n an upward d i r e c t i o n . Thus, t he ho r i -

zon ta l dynamic component adds d i r e c t l y t o the p u l l ( r e s u l t i n g from t h e

shear p o t e n t i a l of t h e s o i l ) , and the ver t ica l dynamic component, to-

ge ther with the s o i l p o t e n t i a l , suppor ts t h e wheel load. This r e s u l t s

i n smaller s inkages than those experienced a t s lower speed, t hus lead ing

* This explanat ion i s equa l ly v a l i d f o r a l l test modes descr ibed ear l ie r (paragraphs 20-23), because i t had been shown t h a t t e s t modes (wheel a t cons tan t speed o r wheel acce le ra t ed during test, etc.) d id not i n f luence t h e performance parameters (paragraphs 30 and 32).

It a l s o w a s found t h a t t h i s i nc rease i n p u l l w a s l a r g e r

26

again t o a h ighe r e f f ic iency .*

assumed t h a t t h e r e l a t i o n between P/W a t a given s l i p , e.g. 20 per-

c e n t , and'wheel speed has the shape of l i n e A i n f i g . 11.

For f u r t h e r development, i t might be

3 6 . I n comparing LSS with sand from a s o i l mechanics viewpoint ,

it appears i o g i c a i t o c l a s s i f y LSS as " f r i c t i o n a l s o i l , " based on the

knowledge of t h e s o i l mechanics p r o p e r t i e s of t h e LSS.

similar e f f e c t s of speed on tests in t h e two s o i l s should have been

expected. This w a s , i n f a c t , no t t r u e , as mentioned above (para-

graphs 31 and 3 4 ) .

however, one cannot exclude the poss ib l e ex i s t ence of a i r -pore p re s su re

i n t h i s b a s i c a l l y f r i c t i o n a l s o i l , because of t h e low permeabi l i ty of

t h e s i l t - to - f ine-sand lunar s o i l simulant. Air-pore p re s su re , t h e

magnitude of which depends on t h e shear v e l o c i t y , would i n gene ra l have

a degrading e f f e c t on the shear p o t e n t i a l of t h e s o i l , and, thus , would

l ead t o a decrease i n p u l l . I f the dynamic speed effects o u t l i n e d i n

paragraph 35 were d is regarded , the gene ra l shape** of t he P/W ve r sus

wheel speed r e l a t i o n , due t o air-pore p re s su re e f f e c t s , can q u a l i t a -

t i v e l y be depic ted by the l i n e B i n f i g . 11. From a comparison of t h e

gene ra l tendencies of t h e two r e l a t i o n s (dynamic speed e f f e c t s and air-

pore p re s su re e f f e c t s ) , i t can be q u a l i t a t i v e l y concluded t h a t t h e two

effects could compensate each o the r , which indeed would l ead t o P/W

being independent of wheel speed. From t h i s d i scuss ion , t h e very

cau t ious conclusion might be drawn t h a t t h e LRV wheels could be more

e f f i c i e n t a t h igher speeds under lunar cond i t ions (no a i r -pore pressure)

than under terrestrial condi t ions on t h e same s o i l .

_ _ ..

Therefore ,

I n a reexamination of t h e s o i l mechanics p r o p e r t i e s ,

* The in f luence of ver t ical component on s inkage is d is regarded i n f u r t h e r cons ide ra t ions , s i n c e sinkage i s not a very important perform- ance parameter because of t h e l i g h t loads used during t h i s s tudy.

s i d e r e d cons tan t and similar t o the " t o t a l stress condi t ion" of a s o i l i f i n e r t i a e f f e c t s d id not t ake place. Because t h i s speed i n unknown, t h i s f a c t w a s n o t considered i n the assumption about t h e shape of t h e r e l a t i o n B .

** The e f f e c t of speed on P/W , beyond a c e r t a i n speed, could be con-

27

01 5 a, a, a m s M -rl X

?

\ \

4\ \ m

Ll u O h o u a l a , G a , k w n p ~ W 3 0

-!--- I

m 5 a, a, a v)

\

\

I I I i I I

I I

28

a a, a, a m rl a,

;

a, Ll

k a a, Ll 0 a I

.? .% 5 G u ( d e

a, m u a , L l v a , h a 0 ruo

N

Phase I1 (GM X Y ) : Effect of Fender, Wheel Load, Wheel Speed, D i rec t ion of Chevron, and S o i l S t r eng th

S o i l cond i t ion LSS4

37. The approach used t o anaiyze the r e s u l t s o f the 21 two-pass

CPS tests* of this series was the same as that used i n the a n a l y s i s of

the phase I d a t a (paragraph 30). The p l o t s of P/W ve r sus s l i p , M / W r e

ve r sus s l i p , and PN ve r sus P/W ind ica t ed that these parameters w e r e

independent of wheel speed, wheel load, o r presence o r absence of t h e

fender . Therefore , t h e r e s u l t s were averaged. The average r e l a t i o n s

wi th t h e i r maximum and minimum dev ia t ions a t t h e characteristic condi-

t i o n s (towed cond i t ion , e tc . , see paragraph 30) are d isp layed i n

f i g s . 12 and 13. For f u r t h e r eva lua t ion , the performance parameters f o r

t h e se l f -p rope l l ed condi t ion and f o r 20 pe rcen t s l i p were p l o t t e d v e r s u s

wheel speed i n f i g s . 14-16; t h e var ious test cond i t ions (with and with-

out f ende r , e t c . ) are ind ica t ed by d i f f e r e n t symbols.

38. E f f e c t of fender . A comparison of t h e r e s u l t s of the tests

wi th t h e fender (open symbols i n f i g s . 14-16) and without the fender

(c losed symbols i n f i g s . 14-16) a t a g iven load and a t a given speed

shows t h a t t h e performance parameters f o r t he se l f -propel led ( f i g . 14)

and the 20 pe rcen t s l i p condi t ions ( f i g s . 15 and 16) w e r e p r a c t i c a l l y

uninf luenced by t h e presence of the fender .

39. E f f e c t of wheel load. According t o the r e s u l t s i n f i g s . 14-

16 f o r t h e se l f -propel led and the 20 percent s l i p cond i t ions , wheel

load a t a given speed level wi th in the range t e s t e d (178 N o r 40 l b

t o 377 N o r 85 l b ) d id not in f luence t h e performance parameters under

cons ide ra t ion , except s inkage ( f i g s . 14 and 15) f o r which a s l i g h t , b u t

no t very pronounced, dependency exists i n s o f a r as s inkage increased

wi th load. However, a t t h i s po in t i t should be emphasized t h a t t h e

a b s o l u t e power requirements increased l i n e a r l y wi th the wheel load .

* Because of t h e r e s u l t s of phase I, i .e . the test technique d i d n o t in- f l u e n c e the performance characteristics (paragraph 30), only the CPS test technique w a s used during phase 11.

29

PI Lo'

-I 1 I 1

c o \ D . j N 0 0 0 0

0 cn

0 a2

0 r.

0 W

0 In

w

0 * .? 4 Lo

0 m

0 N

0 rl

N e e E?

0 4 I

co w - 3 N

0 0 0 0 . .

P F

C cn

0 03

0 r.

0 UY

0 lP

w

.o a u 4 4 Lo

n

0 'm

Q N

0 -4

N U

0 0 . .

\ I 1

.o -4

I

2.8

2.4

2.0

al 2 \

1.6

Slope Angle a , deg 0 5 10 15 20 25 30 35 --L--L--L--_s_--.L~--

Average of / 2 1 T e s t s

P u l l Coe f f i c i en t P/W

Fig. 13. Re la t ion of power number t o p u l l c o e f f i c i e n t and s l o p e a n g l e f o r GM XV wheel on L S S 4 (1st and 2d passes )

31

d

a a, a, a m d a, a, r: 3 m s cn w a, ?

a cn N

a, M (d &I a,

$ 1 O3 - a% IT

I Q I

N 0

0

Q a, a, a

7tn -Id

a,

-I

n 5

3

w a, a

e m a cn ad s u II II II II a, o a a,

3 s s 3 o u z

hl

I 4.

d

d

0 I .d

u a, cn \ U w

0 d

co

Q

hl

D

d

do I

u a, v) 1 e 3

r)

n N

3

N , .

a a, a, a

m m r l d

a, , .

P 0 .. +

-m 0

0 b

32

U a) m 1 U W

0 l-l

co

\o

U

N

'UT I I

kj A4 tu3 .

0 0

u a) m \ B

I

.9 m

v)

N ..

.9 N

I a N

a :I 111 9

0

I 0 d b 0 m3

N rl

0% a%.eyurg

33

cu

L -c_

I I I I o w \D 4. N 0

I+ 0 0 0 0

I

V a, m \ fi

P m

LA

N -.

0

N -.

a aJ aJ a VI

4 aJ

m a , A S

0

-4

LA

-0

0

34

Only t h e dimensionless performance parameters, such as P20/W o r PN

= Mw/Wva , w e r e independent of wheel load . SP

40. E f fec t of wheel speed. Because t h e performance parameters

w e r e no t inf luenced by the presence of t h e fender (paragraph 38) and by

changes i n wheel load (paragraph SYj, a i i data were included i n t h e

a n a l y s i s of t h e e f f e c t of wheel speed. A s has been observed i n t h e

a n a l y s i s of t h e GM XIII test r e s u l t s (paragraph 31), none of t he per-

formance parameters a t t h e se l f -propel led ( f i g . 14) and 20 percent s l i p

cond i t ions ( f i g s . 15 and 16) were c l e a r l y inf luenced by wheel speed.

Therefore , i t appears t o be j u s t i f i a b l e t o r ep resen t t h e corresponding

parameters f o r t h i s given wheel (GM X V ) and the s o i l cond i t ion LSS as average va lues t h a t are independent of fender e f f e c t s , wheel load , and

wheel speed ( f i g s . 14-16).

4

41. Comparison of GM XI11 and GM XV performance. The average

performance parameters f o r t he se l f -p rope l l ed and 20 pe rcen t s l i p con-

d i t i o n s f o r t h e GM XIII ( f i g s . 7-9) and t h e GM XV ( f i g s . 14-16) wheels

are summarized i n t h e fol lowing t abu la t ion .

Self-Propel led Condition 20 Percent S l i p Condit ion

Wheel PN sp z s p , cm Pz0/w J ? N ~ ~ z2() Y cm

GM XI11 0.10 1.3 0.35 0.51 1.8 G M X V 0.10 1.5 0.35 0.49 2.0

It is concluded t h a t bo th wheels performed e s s e n t i a l l y t h e same on t h e

g iven s o i l condi t ion LSS Fur ther , t h e s t a t i s t i c a l va lue of t h e in fo r - 4' mation on t h e performance of t he LRV wheels on LSS

combining the da t a from at least the CPS tests with the d a t a from t h e

tests w i t h the GM XI11 and t h e GM XV wheels (29 tests) .

can be increased by 4

42. E f fec t of chevron d i r ec t ion . The r e s u l t s of t h e seven four-

pass tests wi th reversed d i r e c t i o n of t h e chevron cover of t h e wheel

are shown as performance parameters ve r sus wheel load r e l a t i o n s i n

figs. 17 and 18. Each d a t a p o i n t a t a given load r e p r e s e n t s t h e average

35

a mO. 4

z PI

2.0-

1.0-

0

Ll al 3 0 !&

0

0

I I 0 I

I

--e-- - -4 - - -- -- - - -

-0 .5

1 I

40 I 80 l b

0 100 200 300 400 500 N Load W

a . Power number ve r sus load - LEGEND

Open symbols: Average of 1st and 2d passes

Closed symbols: Average of 3rd and 4 t h passes

- - - t Average f o r normal chevron a t 253 N (57 lb)

a rn

N

b. Sinkage ve r sus load -

Fig . 1 7 . I n f luence of wheel load on performance parameters a t se l f -propel led condi t ion ; GM XV wheel w i t h fender and

reversed h e v r o n ; wheel speed 0.75 m / s e c (2 .5 f t / s e c ) ;

4 s o i l cond i t ion LSS

36

0 hl

PI

u

i i

W w al 2 0 . 2

PI ' 0.1 rl rl

I

0 -i-

!

! 40

6

0

80 lb I I 0 L- -

0 Id0 200 360 do0 N Load W

a . P /W v e r s u s W - 20 LEGEND

Open symbols: Average of 1st and 2d p a s s e s

Closed symbols : Average of 3rd and 4 t h p a s s e s

. ._ _ I Average f o r normal chevron a t 253 N (57 lb)

8

I

80 lb

0 100 200 300 400 N Load W

b. z20 versus W -

0 " 3.0

M 2.0 9 cn 1.0

al

C *r(

0 N z

PI

c 8 0 - - __ . . . . .

40 80 lb

100 200 300 400 N O L ----v--r---

Load W

c . PN20 v e r s u s W -

Fig . 18.. In f luence of wheel load on performance parameters a t 20% s l i p ; GM XV wheel w i t h fender and reversed chevron; wheel speed

0 . 7 5 m/sec ( 2 . 5 f t / s e c ) ; s o i l cond i t ion LSS 4

37

value f o r the f i r s t and second passes* (open symbols), o r f o r t h e t h i r d

and fou r th passes** (closed symbols) from t h r e e tes ts 1253-N (57-1b)-

wheel load] o r two tests [178-N (40-lb) and 377-N (85-lb) wheel l o a d s ] .

43. The power number a t t h e se l f -propel led cond i t ion appears t o

be independent of wheel load ( f i g . 17a ) , which is a confirmation of t h e

f ind ings s t a t e d i n paragraph 39; whereas

lower f o r the t h i r d and f o u r t h passes than f o r first and second passes .

The reason f o r t h i s l ies i n t h e f a c t t h a t t he s o i l w a s compacted dur ing

t h e f i r s t and second passes ; thus , less power w a s r equ i r ed t o p rope l t h e

wheel during t h i r d and f o u r t h passes . This is a l s o ind ica t ed by t h e

s inkage (hub movement) ve r sus wheel load r e l a t i o n f o r t h e same cond i t ion

( f i g . 17b). The d i f f e r e n c e i n z between t h i r d and f o u r t h passes SP

(c losed symbols) and f i r s t and second passes (open symbols) r e p r e s e n t s

t h e a d d i t i o n a l s inkage t h e wheel experienced during t h e t h i r d and f o u r t h

passes . This sinkage is smaller a t a given load f o r t h e l a t te r than f o r

f i r s t and second passes , thus fol lowing the tendency of t h e power requi re -

ments. Generally, t h e s inkage increased wi th inc reas ing load f o r a

given pass (paragraph 39).

PN seems t o be s l i g h t l y SP

44. Bas ica l ly , t h e same observa t ions as f o r t h e se l f -p rope l l ed

cond i t ion were made f o r t he 20 percent s l i p cond i t ion ( f i g . 1 8 ) . S l i g h t l y

more p u l l w a s generated f o r t h e given s i i p of 20 percent dur ing t h e t h i r d

and f o u r t h passes than during t h e f i r s t and second passes ( f i g . 18a ) ,

because sinkage w a s smaller i n t h e former than i n t h e l a t te r ( f i g . 18b).

Accordingly, t he power requirements increased wi th inc reas ing number of

passes ( f i g . 18c) . Fu r the r , s inkage increased wi th inc reas ing wheel

load; whereas P /W and PN20 w e r e e s s e n t i a l l y independent of wheel

load. 20

45. Generally, t h e same tendencies concerning t h e e f f e c t of wheel

load as found f o r t he forward-travel ing wheel (normal chevron, para-

graph 39) were observed f o r t h e backward-traveling ( reversed chevron

d i r e c t i o n ) wheel (paragraphs 43 and 44). I n a d d i t i o n , a d i r e c t comparison ~~ ~~

*Representing t h e LRV backing i n t o undis turbed s o i l . **Representing t h e LRV backing i n i t s own r u t s .

38

of t h e performance parameters f o r the f o m a r d - and the backward-traveling

wheel under the same loading condi t ion (253 N; 57 l b ) and f o r average

f i r s t - and second-pass d a t a shows no s i g n i f i c a n t d i f f e r e n c e ( f ig s . 17 and

18 ) . Thus, f o r a l l p r a c t i c a l purposes, the performances of t h e forward-

and t h e backward-traveling wheel appear t o b e the same. Furthermore,

t he only s l i g h t l y supe r io r performance of the wheel when backing i n i t s

own r u t ( reversed chevron, t h i r d and f o u r t h passes) w i l l most probably

be diminished by t h e power requi red to steer t h e wheel so that it main-

t a i n s i ts travel i n t h e r u t . Thus, i t seems t o be more p r a c t i c a b l e t o

back t h e v e h i c l e i n t o undisturbed s o i l than i n i t s own r u t .

S o i l cond i t ion LSS 5

4 6 . Following the same l i n e of thought as i n t h e a n a l y s i s of t h e

GM XV test r e s u l t s (paragraphs 30 and 37), t h e P/W ve r sus s l i p , M/Wr

ve r sus s l i p , and PN ve r sus P/W r e l a t i o n s f o r t h e 16 CPS tests con-

ducted on LSS5 i n d i c a t e no dependence of t h e s e parameters on wheel speed,

wheel load , o r t h e presence o r absence of t h e fender . The average re-

l a t i o n s , wi th t h e i r maximum and minimum dev ia t ions a t t h e c h a r a c t e r i s t i c

cond i t ions (paragraph 3 0 ) , are shown i n f i g s . 19 and 20. For a more

d e t a i l e d a n a l y s i s t h e performance parameters f o r t he se l f -p rope l l ed and

t h e 20 percent s l i p condi t ions w e r e p l o t t e d ve r sus wheel speed, and t h e

va r ious test condi t ions were indica ted by d i f f e r e n t symbols ( f i g s . 21-23).

47. E f f e c t of fender . Because i t w a s found t h a t t he presence of

t h e fender d i d no t i n f luence t h e performance of t h e wheel on s o i l con-

d i t i o n LSS4 (paragraph 38) , only one of t h e 16 tests on s o i l cond i t ion

LSS5 w a s conducted without t he fender t o check t h i s conclusion.

r e s u l t s of t h i s test (c losed symbol in f i g s . 21-23) confirm the above

f i n d i n g s f o r LSS4 .

PN , P20/W , and PN20 a t a given speed ( f i g s . 21-23) l e a d s , as i n

t h e case of s o i l condi t ion LSS (paragraph 391, t o the conclusion t h a t

t h e s e parameters were independent of wheel load . Only s inkage ( z

f i g . 21b;

e

The

4 8 . E f f e c t of wheel load. Comparison of t h e performance parameters

SP

4

SP ’ z20 , f i g . 22b) showed a tendency t o inc rease wi th inc reas ing

39

w o m u a m M U

i , I I

m m . 3 c Y 0 0 0 0

vi P I 0

W I I

0 ” I

-, I I I m w . 3 N (

0 0 0 0

2.8

2.4

2 .o

1 .6

1 .2

0.8

0.4

Slope Angle a , deg 0 5 10 15 20 25 30 35

/Average of 16 Tests

-- Var ia t ion f o r 20% S l i p

T

e

--o! 2 ' 0 0.9 0 ! 4 0'. 6 P u l l Coef f ic ien t P/w

Fig . 20. Rela t ion of power number t o p u l l c o e f f i c i e n t and s l o p e ang le f o r GM XV wheel on LSS5

( 1 s t and 2d passes)

41

I ‘ w

pL a a, a, P 4 (I)

d a, 01 c ? cn

&I z $! a cn

N

I i

0 0

a al a, 2 d al a, c 3 (I)

Ll 2 $

P

z PI

; I

I 1 i I I ‘UT

L) al VI \ U w

0 rl

no

I

I Q I

““I-: I

I I I . - 0 0 0 m3 . (v d

dsz a%eyurg

J U n i

> 7

9

v

2 u

a a, al

. m rl a,

n a 4

0

rl . .

In

0 ’ .

0

42

I %I 4 0 d l S

I w

a a, a, a m rl Q

P ffl 9 (0 U $ 5 \

P.l

0 N

P I

4 3

N

0 rl.

5. 4

u

I N

0 i

3; I

4

1 I

In

0

rl D

d D

-0 al a, a m d a, a, s 3 m 1 0 U d 0 hl

N

;I

m u u h i m

5 w I - r w a 0 4Ja 3cI-r O a J a J

I

rl

pd" I I

I I 1 I I

! i I I '<

I 1

I ! I I I I I I I I I

V aJ m 1 u w

0 rl

03

U a, m \ El

vr m

0

m

m hl

a a, aJ a m rl oa,

A ;

m rl

0

rl

In

0 , .

0

44

wheel load.

49. E f fec t of wheel speed. The same observa t ion as f o r s o i l

cond i t ion LSS4 (paragraph 40) w a s made f o r s o i l cond i t ion LSS

r e l a t i o n between t h e performance parameters f o r the se l f -p rope l l ed

cond i t ion and f o r 20 percent s l i p and t h e wheel speed ( f i g s . 21-23) d id

not show any in f luence of wheel speed. Therefore , t h e performance

parameters were averaged r e g a r d l e s s of wheel speed, etc. ( f i g s . 21-23).

I n f luence of s o i l s t r e n g t h

The 5'

50. I n a d d i t i o n t o the average performance parameters f o r s o i l

cond i t ion LSS5, t h e average va lues f o r s o i l condi t ion LSS

are d isp layed i n f i g s . 21-23. The power requirements ( represented by

t h e power number) f o r t h e se l f -propel led condi t ion were h ighe r f o r LSS4

than f o r LSS5 ( f i g . 21a). On t h e o the r hand, a t a given s l i p of 20 per-

cen t , more p u l l w a s developed on LSS than on LSS ( f i g . 22a) and,

consequent ly , t h e power requirements ( f i g . 23) increased from s o i l

cond i t ion LSS4 t o LSS

(GM XV wheel) 4

5 4'

5' 51. To c l a r i f y t h e in f luence of s o i l s t r e n g t h on performance, t he

average p u l l and torque c o e f f i c i e n t ve r sus s l i p r e l a t i o n s from t h e tests

wi th t h e GM XV wheel on s o i l condi t ion LSS4 (from f i g . 12) and on s o i l

cond i t ion LSS5 (from f i g . 19) were p l o t t e d toge the r ( f i g . 24).

t h i s comparison, i t fo l lows t h a t , i n gene ra l ,

than f o r LSS a t a given wheel s l i p . This tendency may be a t t r i b u t e d

t o t h e f a c t t h a t t h e a v a i l a b l e shear p o t e n t i a l of t h e s o i l w a s g r e a t e r

f o r LSS5 than f o r LSS4. Corresponding t o t h i s i nc rease i n P/W w a s

t h e i n c r e a s e i n t h e torque (M/Wre) requi red t o u t i l i z e t h e shear

p o t e n t i a l of t h i s s t ronge r material (LSS5) .

to rque c o e f f i c i e n t a t the se l f -propel led condi t ion (paragraph 50) were

smaller f o r LSS5, and less s l ippage occurred.

expected, because the wheel experienced less sinkage i n s t r o n g e r s o i l ;

t hus , t h e r e w a s less energy l o s s due t o s inkage and bul ldozing.

which is most important , f o r a given P/W (or s l o p e the LRV cl imbed) ,

e.g.

(8 percent ) than i n L S S 4 (11.5 percent) .

From

P/W w a s l a r g e r f o r LSS5

4

The towed f o r c e and t h e

This behavior w a s as

F i n a l l y ,

P/W = 0.25 ( f ig . 241, the s l i p developed i n LSS5 w a s sma l l e r

As a consequence, t h e necessary

45

a m * m N 4

0 0 o v l o 0 . c , .

c c o b 0 0 0

0 U

II

3 PI 1

0 m

0 N

.I= *rl k ld a 2

rl N *

0 rl

- 1

to rque requirement (M/Wr ) w a s s l i g h t l y less f o r LSS (0.28) than f o r .

L S S 4 (0.29).

52.

f o r a c e r t a i n p u l l f o r t h e two s o i l condi t ions becomes even more obvious

in the ~ i ~ i i p ~ i r i ~ ~ n of the r e l a t i o n s between power number ( torque r equ i r ed

p e r un i t weight per u n i t d i s t a n c e of t r a v e l ) and p u l l c o e f f i c i e n t and/or

s l o p e ang le , r e s p e c t i v e l y ( f i g . 25) .* From these r e l a t i o n s , i t can be

concluded t h a t t h e power requirements f o r t h e LRV are l a r g e r f o r t h e

s o f t e r s o i l (LSS4) on any given s lope (any given P/W) than f o r t h e

s t r o n g e r s o i l (LSS5).

wi thout using excess ive power w a s about 19 k6 deg i n LSS and about

23 k 5 deg i n LSS

e 5

The i n t e r r e l a t i o n between torque requi red and s l i p developed

Fur the r , t h e maximum s l o p e t h e v e h i c l e could climb

4

5'

The s p e c i f i c e f f i c i e n c y term (Pva/Mw) used h e r e i n is

53. Another po in t of i n t e r e s t is t h e in f luence of s o i l s t r e n g t h

on e f f i c i e n c y .

de f ined as t h e r a t i o of recoverable energy t o t o t a l energy i n p u t ; t hus ,

t h i s term r e f l e c t s t h e r a t i o of t h e n e t p u l l t h a t is developed over add

above t h e p u l l t h a t a l lows t h e wheel o r v e h i c l e t o p rope l i t s e l f , t o t h e

t o t a l energy inpu t . A s a consequence, t he e f f i c i e n c y w a s zero f o r t h e

se l f -p rope l l ed cond i t ion (P/W = 0) and f o r 100 pe rcen t s l i p ( c a r r i a g e ,

o r v e h i c l e speed v = 0) . For any given P/W (except P/W = 0) o r

s l o p e a n g l e a , t h e maximum e f f i c i e n c y occurred a t P/W = 0.31 +0.15,

o r ct = 17 +8 deg, i n LSS and a t P/W = 0.33 k0.14, o r Q = 18 27 deg,

i n LSS The corresponding torque c o e f f i c i e n t s and power numbers f o r

maximum e f f i c i e n c i e s were M / W r

LSS4 and M/Wre = 0.32 10.10 and PN = 0.36 k0.12 f o r LSS

f o r any given torque requirement (M/Wr ) o r power requirement (PN),

e f f i c i e n c y w a s h igher on LSS

a

4

5' = 0.35 t O . l l and PN = 0.42 k0.13 f o r e

Furthermore, 5'

e than on LSS4 ( f i g . 26). 5

54. For an o v e r a l l p i c t u r e of t he in f luence of s o i l s t r e n g t h on

t h e performance of t h e Boeing-GM wheels, d a t a from an earlier s tudy , i n

which t h e GM X and GM X I 1 1 wheels (both 50 percent chevron covered) were

* The power number and e f f i c i e n c y versus p u l l c o e f f i c i e n t r e l a t i o n s r e p r e s e n t , as i n f i g s . 24 and 26, the average r e s u l t s of 21 tests on LSS4 and 16 tests on LSS5.

47

M a, e

2 5 M a,

Pi

3

Slope Angle a , deg 0 5 1 0 15 20 25 30

I I

1.

Fig. 25. Comparison of r e l a t i o n s of average power number and . e f f i c i e n c y t o p u l l c o e f f i c i e n t and s l o p e a n g l e

f o r GM XV wheel on L S S 4 and LSS5

48

I I I ! 1 ' I

\3

I+ . .

d

.n

ob b 4 N 0 1

J o

4 0 0 0 0

49

t e s t e d on var ious LSS condi t ions (Green and Melzer, 1971b), and

corresponding da ta from the i n v e s t i g a t i o n s repor ted he re in w e r e used t o

show t h e inf luence of the cone p e n e t r a t i o n r e s i s t a n c e g rad ien t G

( represent ing " s o i l s t rength") on p u l l c o e f f i c i e n t , power number, and

e f f i c i e n c y a t 20 percent s l i p ( f i g . 27). The inc rease of performance

i n terms of P /W w a s approximately 50 percent over the whole range

of G t e s t ed . Since t h i s range covers G va lues from 0 . 2 2 MN/m

(0.8 p s i / i n . ) * t o 6 . 3 9 MN/m (23 .6 ps i / in . )** , t he inc rease i n G is

not r e f l e c t e d very c l e a r l y i n t h e inc rease i n performance. However,

t h i s range of

of t h e s o i l from 30 t o 60 percent . This s m a l l change i n relative

dens i ty , together wi th t h e f a c t t h a t f o r l i g h t l y loaded wire-mesh wheels

a change i n s o i l s t r e n g t h does not c o n t r i b u t e too much t o the performance,

exp la ins the inc rease of only 50 percent i n

re la t ive dens i ty , cohesion a l s o inc reased , from zero f o r LSS t o

2 . 9 kN/m (0 .42 p s i ) f o r LSS a f a c t t h a t i s p a r t i a l l y r e f l e c t e d i n t h e

high v a r i a t i o n of G . However, i t w a s found earlier t h a t such

re la t ively s m a l l amounts of cohesion do n o t have a very pronounced e f f e c t

on t h e performance of l i g h t l y loaded wire-mesh wheels.

3 20

3

G corresponds only t o a change i n t h e r e l a t i v e d e n s i t y

P20/W . I n a d d i t i o n t o

1 2 5'

*Average G f o r s o i l cond i t ion LSS ( f i g . 2 7 ) .

**Average G f o r s o i l cond i t ion LSS5 ( f i g . 2 7 ) . 4

50

eg

I I I I

0 1 7

I I

N

I

0 N 2 PI

l

\ I

\o \

m- N - cn"

VI 4

H u L H r l

I l l

0 4JQ 0 4

m -: 4

m

-- - 1 1 - I I m 0

3 N

0 0 0

0

&? 0 N

U a v) k aJ J J

rl

51

PART I V : CONCLUSIONS AND RECOMMENDATIONS

Conclusions

55. Based on t h e f ind ings of t h i s s tudy , i t w a s concluded t h a t :

a. -

b. -

C. -

d. -

e.

f .

-

-

h. -

The performance parameters f o r t h e GM X I 1 1 and GM XV wheels on lunar s o i l s imulant w e r e independent of wheel speed (paragraphs 30, 40, and 49) ; b u t performance increased with speed i n t h e tes ts wi th t h e GM X I 1 1 on sand (para- graph 33). This discrepancy might have been caused by occurrence of a i r -pore p re s su re i n the LSS (paragraph 36). This w a s t h e only comparison p o s s i b l e between performances on LSS and on sand.

The performance parameters w e r e independent of wheel a c c e l e r a t i o n (paragraph 32).

Classical programmed-slip, ramped-slip, and modified programmed-slip test techniques gave the same r e s u l t s f o r given tes t cond i t ions (paragraphs 30 and 3 2 ) .

Except f o r s inkage (hub movement), which increased wi th wheel load , performance parameters w e r e n o t in f luenced by changes i n wheel load (paragraphs 39 and 48).

The presence of a fender d i d no t i n f luence the wheel performance (paragraphs 38 and 4 7 ) .

The GM X I 1 1 and GM XV wheels showed p r a c t i c a l l y t h e same performance on t h e same s o i l condi t ion (LSS4) (para- graph 41).

S o i l s t r e n g t h i n terms of pene t r a t ion r e s i s t a n c e g rad ien t G inf luenced wheel performance (paragraphs 50-54); f o r a given s l i p , p u l l c o e f f i c i e n t and power requirements increased wi th inc reas ing s o i l s t r e n g t h . However, f o r a given p u l l c o e f f i c i e n t o r s lope , s l i p w a s less i n f i rmer s o i l ; thus , power requirements decreased and e f f i c i e n c y increased wi th inc reas ing s o i l s t r e n g t h . Torque c o e f f i - c i e n t s and power numbers a t which m a x i m u m e f f i c i e n c y occurred w e r e 0.35 20.11 and 0.42 k0.13, r e s p e c t i v e l y , f o r the LSS4; and 0.32 kO.10 and 0.36 t0 .12, r e s p e c t i v e l y , f o r the LSS (paragraph 53) .

The maximum s lope t h e LRV could climb without using excessive power would be about 19 deg, t 6 deg, i n LSS and about 23 deg, t 5 deg, i n LSS5 (paragraph 52) .

5

4

52

i. The performance of the wheel w a s the same if i t t r a v e l e d forward o r backward i n t o undis turbed s o i l . The perform- ance w a s s l i g h t l y better i f i t backed in i t s own r u t . However, t h i s advantage might be l o s t by t h e power r equ i r e - ments due t o s t e e r i n g t o keep t h e wheel (o r veh ic l e ) i n t h e r u t (paragraphs 42-45).

-

Recomendat i o n s

56. It is recommended t h a t :

a . S e r i e s of t r iaxial tes ts b e conductek t o check t h e in- f luence of p o s s i b l e a i r - p o r e p re s su re on t h e shea r c h a r a c t e r i s t i c s of the lunar s o i l s imulant .

- b . S e r i e s of single-wheel t e s t s be conducted wi th a i r -po re p re s su re measured (e.g. with p iezometers ) , o r scale-model tests b e conducted under vacuum cond i t ions , t o i n v e s t i g a t e the in f luence of a i r -pore p re s su re on t h e wheel performance.

A l l p o s s i b l e information about t he performance of t h e LRV c o l l e c t e d during t h e Apollo 15 mission be c a r e f u l l y eval- uated wi th regard t o t h e performance p r e d i c t i o n p o t e n t i a l of t h e information assembled i n t h i s s tudy.

-

- c.

53

LITERATURE CITED

Costes , N. C. , Carrier, W. D . , Mi t che l l , J. K . , and S c o t t , R. F. (1970), "Apollo 11: Socie ty of C i v i l Engineers, S o i l Mechanics and Foundation Engineer ing Div i s ion , Vol 96, SM6, p 2045.

S o i l Mechanics Resul t s , " Proceedings of The American

11 F r e i t a g , D. R. , Green, A. J . , and Melzer, K. - J . (1970a), Performance Evaluat ion of Wheels f o r Lunar Vehicles," Technical Report No. M-70-2, U. S . Army Engineer Waterways Experiment S t a t i o n , CE, Vicksburg, M i s s .

(19 70b) , "Performance Evaluat ion of Wheels f o r Lunar Vehicles (Summary Report) ," Miscel laneous Paper No. M-70-4, U. S. Army Engineer Waterways Experiment S t a t i o n , C E , Vicksburg, M i s s .

Green, A. J. and Melzer K.-J . (1971a), "The Performance of Two Boeing- GM Wheels (GM V I 1 and GM VII I ) f o r t he Manned Lunar Rover Vehicle ," Miscellaneous Paper No. M-71-3, U. S. Army Engineer Waterways Experi- ment S ta t ion , CE , Vicksburg , Miss.

(1971b), "Performance of t h e Boeing LRV Wheels i n a Lunar S o i l Simulant; E f fec t of Wheel Design and So i l , " Technical Report No. M-71-10,Report 1, U. S. Army Engineer Waterways Experiment S t a t i o n , CE, Vicksburg, M i s s .

Le f l a ive , E. and Wiendieck, K. W. (1965), "Theore t ica l Evaluat ion of t he Speed Ef fec t on Drawbar P u l l of Powered Wheels on Dry Sand," Memorandum f o r Record (unpubl ished) , U . S. Army Engineer Waterways Experiment S t a t i o n , CE, Vicksburg, M i s s .

Melzer, K . - J . and Green, A. J. (1971), "Performance Evaluat ion of a Firs t -Generat ion Elast ic Loop Mobi l i ty System," Technical Report No. M-71-1, U. S. Army Engineer Waterways Experiment S t a t i o n , CE, Vicksburg, M i s s .

Mi t che l l , J. K. Bromwell, L. G . , Carrier, W. D . , Costes , N. C. and Sco t t , R. F. (1971), "Apollo 14 - Pre l iminary Science Report; S o i l Mechanics Experiment," NASA Spec ia l Report SP-272, Sec t ion 4 , Nat iona l Aeronautics and Space Adminis t ra t ion , George C . Marsha l l Space F l i g h t Center , A l a .

S c o t t , R. F. , Carrier, W. D . , Costes , N. C . , and Mi tche l l , J. K. (19711, "Apollo 12 S o i l Mechanics I n v e s t i g a t i o n s , " Geotechnique, Vol 21, p 1.

Turnage, G. W. (1972), "Performance of S o i l s Under T i r e Loads; Appli- c a t i o n of T e s t Resul t s t o T i r e S e l e c t i o n f o r Off-Road Vehicles," Technical Report No. 3-666, Report 8 ( i n p r e p a r a t i o n ) , U. S. Army Engineer Waterways Experiment S t a t i o n , CE, Vicksburg, M i s s .

54

h

rn u aJ aJ 4 rl 0

N I I I I h ; l b I I I I I I I I I I I I

rl rl

w 0

4 m N N 0

l l l l m l l \ o I I I I 1 1 1 1 I l l 1

rl rl

rl N

I I I I m I I I 1 1 1 1 1 1 1 1 1 1 1 1 . m N N 0

1 1 1 1 m l l a 1 1 1 1 1 1 1 1 I I I I

\ o u \ o o c c ) Nu074 rlrlrlrl . . . .

-x O O r l N

-x O O d N

-x O O r l N

* O O r l N

u cn cn I4

4- .* U m cn I4

\o I VI

cn- cn I 4

m - I4 cn k

aJ U d

\o \o I

N I rl 0 0 0 0

I rl

I rl

h 2 4

\o I m

hi CI u aJ rn rcl rcl 0 -x

u rn aJ El

rl h 4

I I I I

1 1 1 1

I I I I

1 1 1 1

I I I I

I l l 1

I I I I

1 1 1 1

I 1 1 1

1 1 1 1

rl rl

I I I I I I I I 1 1 1 1 1 1 1 1 I l l 1

I I I I 1 1 1 1 I I I I I I I I I I I I I I I I 4 I I I I I I I I I I I I I I I I I I I I I I I I

h a PI

rl u e 0 u

rJ PI rl P a r+

2

W

I I I I I I I I I I I I I I I I I I I I I I I f

co I * rl

h

rl * I

ul I '

rl

co rl * I

co I * rl

h

rl * I

co I * rl

co rl ' I

co I * rl

h c . rl

h

rl - 1

9

rl ' I

h I * rl

h

rl * I

h I ' rl

h I '

rl

h

rl * I

h I * rl

h I . rl

h

rl * I

h I . 4

m rl

0 1 co

I . rl

ul I * rl

m I ' rl

co rl * I

m I * rl

03 L ' rl

-x Y -x Y Y rbz O O r l r J 0 0 r l N 0 0 r l r J O O r l r J 0 0 r l w o o r l r J P,

U U U U 6

=I $1 3 I4 I4 d 4 I4

r l u *4 m m v3 cn m m

VJ cn m m m

9 I h

9 I

a a I rl rl 0

I rl h 4

0 0

rl h 4 4

m vr m 0 m l l \ o I I I I I I I I I 1 1 1 I 1 1 1 1 1 1 1

1 1 1 1 I l l 1 C I I I I l l 1 I l l 1 1 1 1 1

rl rl a)

. . . . . . . . . . . . . . . . . . . . . . . . g a l $Irlrlrlrl orlrlrl r lddrl drlrlrl orlr lr l rlrlrlrl *I4 o u m

\ o \ o N h \ o \ o m v r NNr l \o m m m o h R m O \ o c o U c o oorll- l c o c o o c o d c o w N r n * ooocy cocomN* m.mrll-l* rlrlrlr; o o r l o rl0r;rl r l r l r l r l o0o l - i o o r l r l

r l c o m v r m O O N N o * m 0rlhl.e 0 h . r l m O c o N U A r l r l r l O N r l r l r lNF l r l r l c y r l r l rlrlrlrl rlrlrlrl

. . . . . . . . . . . . . . . . . C m &

p l p r l h o l - l m N U v r r l v r N \ D c n R O h N N r l U r l v r U v r \ o . . . . . . . . . . . . . 0 . . . . . . .

9-r 0

\o L a \o \o \o \o I

R I

\o I 4

I I rl

cy m rl rl rl rl rl

0 0 0 0 I rl

I I l-l rl

I 0 0

rl I I

rl R h R R h

Q 4 4 4 4 4

I vr

i?

cn u h h a,

I 12 I I I I Q)

t2 h co rl rl rl

I I I I I l l 1 - 1 1 . I l l 1 4

a3 co rl m 0 0 rn 0

!+I I I l I \ q I I \ q I l l 1 " 1 l ' h . 1 1 1 1 4

rl rl rl rl

rl \D r n l I I I I I I

a a,

G .rl u C 0 U

a

W

a3 0 W I

rl U r n I

m 0

l h . d rl rl rl

. . . . . . . . . . . . . . . . . . . . . . . . l $ l l O r l r l d r l P 4 r l 4 r l w r l r l r l N r l r l rlrlrlrl orlr lr l

cn .I v l o u c .K * * * (dzloor lh l oorlC-4 O O d h l O O r l N oor lh l oorlhl

I 03

I m rl

I m U

0 I

0 I rl h 4

h 4

n m a 0 0 m m c,

1 1 1 1 A l l I I I I I I I I * I I I l l 1 a N rl rl

0

N - 1

0 I -

N

m rl ' I

m I .

rl

0 I '

N

00

rl * I

00 I -

rl

h h 0 rl h h h N

I I I I m l l m I l l 1 1 1 1 1 m l l r o 1 1 1 1 4 rl rl rl rl

rl h I n 1 rl

h ro m I rl

rl 0

I r o I I I I I I I I I I I I I I I I rl

n a a N 00 I n n

rl

U 00

I n rl

m h m I rl

rl U

I r o I I I I I I I I I I I 1 I 1 I ! rl

n a a V U h

I - rl

h

rl * I

h 1 . rl

ro rl * I

m rl

' I a0

I - rl

h

rl * I

h I .

rl I I I I

hl

al rl P (d r+

00

rl * I

h I - rl

ro d * I

h

rl - 1

Io I ' rl

ro I '

rl

In

rl * I I I I I I I I I

00 I .

rl

ro I .

rl

m rl ' I

o\ I . rl

00

l i ' I

h I .

rl

m rl

* I h

rl * I

h I .

rl I I I I

W I m In 0 I rl h 4

ro I U In 0 I rl

ro I In In

ro I ro In 0 I rl h 4

ro * I O N z m 0

W I m r l $ 2

0 I rl h 4

I- 4

h

2 2 .rl u

U W

" al rl P (d Fl

ul 0 m rl rl CJ

I I I I * I l l " 0 . 1 1 1 * l l i 1 1 1 1

'I rl rl rl rl

h 0 0 0

I I I I I I I I I I I I I I I I h l I h I l l I

h m 0 m UI U rn h

1 1 1 1 1 1 1 1 Q 1 1 1 - 1 1 1 711'9 I I I I

d rl rl d n a

* * U * * (dz O O r l " O O r l " O O r l " 0 0 4 " O O r l N O O r l " a *

h 4

I d h 4

a I

h 4

a I m a 0 I rl h 4

n rn L) L Q)

n TI a)

\o \o \o \o \o \o I h

I m I hl I h h h

m * I I o m co 0

a \o 0 0 0 0 0

z \ o I rl

I d

I d

I h h h

rl I d

U I v ) d

4 e 4 h h $ 2 c c

0 m hl

N 1 1 1 1 , ; I l l A l l I I I I 1 1 1 1

I

d hl

I I

0

hl * I

I

m hl

I

I

m m \o

d

I I

co 0 \ o I d

I I

\o rl

I \ o

d

In In m e

I

I I I I I I I I 1 1 1 1 1 1 1 1 I l l 1 4

.. a *

-K c * 3: ( d o oorlhl O O r l C J oorlcv oorlhl O O d U Ptz $ * I *

h

4J

V W

N

a, d P cd I3

I I I I

I I I I I I I I

3 tu 0 m

1 1 1 1 1 1 1 1 1 1 1 1 I I I I

W

I I I I I I I I I I I I 1 1 1 1

h

1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 I l l 1 I l l 1

I l l 1 I I I I I I I I I I I I I I I I I I I I

h 4

\o I N

\o 1 m

d h 4

r.7, I l l . .

N r n

V i 04

I l l . . r l d

9 7 I I I m a

u n

mm,? m c . . . . . 444 C d

4I?N nn ln o o c - . . I 1

D V N V U uu-- 4 i

C G O cc. I I

. . . . . 3-4 L T U -3%--3 N N

c c c c c I 1

. . . . .

9 2 9 9 7 0 0 3 0 a N N N r l i

I 1

G h r . c o o 0 3 0 . . .

o o c N u O I l l

. . . rnxr. c = = . . . - _ - --I

4" n n r n -44 1 . .

h

u1 U

m

5 w-

u.4 0

V v

h h ' I - 0 0

N C V N N N N , . . . . . . . 000 I l l

o m 0 m N m 000 I I I

. . . u u m. . . m a w I l l

N N N m m m drlrl . . .

M r l W 3 4 2

m m m 000 . . .

n , a Q)

-4 4-l

u "

g

a

m m m N C V N . . .

\D I

U rl 0

I rl h 4

m bo .rl w a, a m 3:

m m u u u u 000 . . . I - m o

m u u 000 . . . m m

u r l I l l I l l I l l . . 0 0

c o o m m u m 000 . . . N m

u r l I l l I l l I l l . . . 000

. . . 000

. . 0 0

m \ D d m N m 000 . . . a m

m o 1 1 1 I l l I l l

0 0 . . h a h

m m m 000 . . . m m u

m h \ D 000

m m m c o h h \ D a m

. . .

. . . c o c o a l m m m . . . m w m

or lo rlrlrl

. . . 0 m - J m m m u u u . . .

m u m 000 . . . m m

- 1 0 0

u m m 000 . . . m h m h \ D m c o h c o m m

0 0 000 0 0 0 0 0 0 . . . . . . . . . . . m w u

000 . . .

u u m r l N d

000 . . . O N r l

m m m h N I I l l I l l I l l 0

I l l . . . 000

c o o m N m N 000 . . . m rl u m m ha03 coaN

N O 000 rl*rlrl* rl" . . . . . . . . u m m

000

rl N* rl o m 0 N d N

000 1 1 1 0 0 000 000 000 I I l l I l l I l l

N R O m w m . . . c o h m

N r l C V

000 . . . co m u c o r l c o m m m a m

4 0 r l o r l NCJN N m m m w c o r l N d

000 . . . . - - . . . . . . . . . . .

0 0 000 000 000 I I l l I l l 1 1 1

000 I l l

c o h m N m m . . . m \ D c o

m m m . . . 00 m N m r l m w r l m h * m . . . . . . . . .

\D u mCVm a m m m u u I I I rlrlrlrlrlrl

I l l I l l

000 m m m d m mace h o e h m r l m N r l dd m m m m u u rl N N N N m m m m m m . . . . . . . . . . . d0r-I m m m

rlrlrl . . . m o o c o m m . . .

000 . . .

rlrlrl

M r l N 3

4 M

r lN 3 a! M

d N 3 4

b) L,l

2 2 2 cn &

cn w 2 a w m h 0 arl W H

\D I m rl 0

I rl h

\D I

\D I

a I 0

a I rl c5

0 0 I rl r- 4

ui 0 0 I rl

0 0 0 0 0 0 I l l

rl 0

I d h 4

rl 0 I 4 4 h h

4 4

n a al V 7 d U

V v

a al rl P (d H

E

$ J 5 E

J < . . . . . . . s I y m m m w h b

E l 000 0 0 0 0

m a w b W h c v . . . . . . d 000 0 000

0 u a r l o w m o m c v

u u e 4- a w a . . . . . . . yI +I a m m m m h m

0aDCo- T I 1 ’ . . . ’ 400

I l l

I l l

I I I

I l l

ddr l m m m rlrlrl . . .

d c v bo

%

ii a I h rl 0 I

I 1 1 1

m c o m r l dd

I 0 . .

000 I l l

m u e N N N I . . . 000 I l l

m u d . . . I m m m

I l l

m N r l c v m m m m d 000 . . . .

bo rl r l c v 3

4

a a I I c o m d d 0 0 I I

P-

a, 4 P H

U m m cl C

rl B

2 & F 5 5

al

d 3 m U m a, H u 0 w

m $4

U a, s

2

rn PI a,

8

m B

w $4

pc

w 0

h

o m v)

V I -!1?999

o m N

$4 0 v(

u u m r l d ~ . . . . . . 0 0 0 0 0 0

r l o w h o m

a

m

r -cow m . . . . N N N N

a J N O P-

O d d 0 o ' ? ? o'

S ? ? s m r l o m

0 0 0 0

m P - W N u u u u 0 0 0 0

0 0 0 0 m m m m

. . . .

N u m N

N N N N

m m m rl m m m m 0 0 0 0

u u u rl u u u u 0 0 0 0

. . . .

. . . .

. . . . ~ m r l m $15 1 0 0 0 0

0 0 0 0 N N N N

om03 W N d r l r l

m c o -

. . . .

L O G G

9 9 9 9 l-ua m

0 0 0 c

0 0 . . l r l r l -

I I I

m m r

0 0 c

m m m (c m m m LT N N N n

' 9 9 -

o m m o ci?? 0 0 0 c I l l I

m c o N r

0 0 0 c bar. r . . .

W I D I I m m uP- 0 0 I I dr l P-l- 4 4

W W I I

ul- 0 0 I I 4 4 P-l- 4 4

m m

l u m N r l u O P - N u c o w a J m 1r l r lHr l r loFloor loor l r l : 9 ?I?? 910. 9 ?lo'? 410. "i ci

) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 l m m m m u l m m m m m m m m m I I I I

I N P - u m W d U m r l m m o u N

) 0 0 0 0 0 0 0 0 0 0 0 0 0 0

7 u m m m m m 0 11 m, m, m. ? me . . . j . . . j . . 1 1 ~ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 I N N N N N N N N N N N N N N H l l r. W m u In W u m 0 y m m. . . .I . . .I . . .( . .I

4 r l r l d r l d r l r l r l r l r l r l r l O 4

1 ". 9 ? 9 9 ? ? ? ? ?

9 9 0. F! 4. rl*

' ."?-f.'9"1??".??"0.?0.

4 0 0 0 r l 0 0 N r l 0 r l 0 N U ~

~ m o c o r l o u ~ m ~ ~ w c o ~ u .I rl N 0 rl 4 rl rl 4

1 0 0 0 0 0 0 0 0 0 0 0 0 0 0

rl

. . . . . . . . .

~ r l r l 7 l d 4 N r l N 0 0 0 0 0 0

> 0 03 0 m m 0 0

4 u N o m P - O m P - W u m d 4 d 1 1 1 r l 1 1 d 1 1 1 1 1 1 1 1

3 d r l m m u ~ m r l l - o m m ~ w

3 0 0 0 0 0 0 0 0 0 0 0 0 0 0

m y 9 0.99 9 . . . . . . . . .

1?- i???".?r l?".?-!??

- i m o ~ - c o m ~ m r l r l o w ~ ~ ~ 4 0 rl N N N W l- P- m u u > o o o o o o o o r l r l 7 l o o o 1 1 1 1 1 1 1 1 1 1 1 1 1 I I

. . . . . . . . . . . . . N. N N.

0 0 00 m m 0 0 0

0 0 co u u m 0 0 0

. . $

. . . \OW m m m m 0 0 0

0 0 0 N N N

. . .

9 9 9 l r l d rl

I 1 I

W W N

' 9 9 0 0 rl 0

. . . . 0 0 0 0 I l l I

corlo m ? ? ? ? r l r ld rl

W I 4 m 0

rl P- 4

W I N

m 0

rl P- 4

W I m VI 0

4 r. 4

l W W W W I I I 1

N N N N

1 1 I 1

I m o 0 4 coo or l

N. a u

m o u d m o

. . ddr l

. . . 4 0 4

m m N q -2 In

o o a u w m m m u 0 0 0

a 0 3 m m m

. . .

. . .

m N m 4 d d

m m u

2 0 0

a u m m o m 0 0 3

U G N m m m 0 0 2

0 0 0 "N

. . . ?5'5

. . .

. . .

e a - 1

0 0

9 1 9

9 1 9

u u

a c n

O G

I l l

I l l

I l l

a m m -I-- d d d

m u 0

O G O I l l

w m m . . .

m m \ D N N N

N N N . . .

M d 4 ?

4

* * m m & P I v u

rld

c 4

0 1 0 0 0 ~ 0 0 0 0 0 0 0 0 m m m m m m m m m l n m m m I I I I

3 o ~ ~ C F - O ~ N N ~ ~ U c u m m u m u u u m m m m . I . . . . . . . . . . . .

3 c 3 0 0 0 0 0 0 0 0 0 0

0 1 0 3 0 0 0 0 3 0 0 0 0 0 N N N N N N N N N N W N N

m m 0 0 . I

0 1 0

N N d d . I . 0 3

N1OU h r - b . . . o o c I l l

r.mm "hl

N N N . . .

to N N >

4

o o c o ~ 0 0 0 0 0 0 - N N N N " N N N N N Z I P I

m a . . d N

o m \ou

m u

0 0

. . ? ?

m m . . rld

a m m N I I

\om d d

c o

I-- I-- m m

. .

. .

-a N N

0 0 I I

. .

lnr. m m . . d d

D5 d >

4

\o I U m 0

-I I- C

911 N N N

d r ld

N N N . . .

??9? ddr l I l l c 3 c ddr l

0 0 0 . . . --I- h r - r . n m m

G b h

o c c I l l

N N. N . .

c N N >

4

h v) U 0)

s cn U

w 0 N v

h 3 m

E .I4 U c ij v

* u m m " N N . . . .

O O Q U

d 0 d d ?"9

P - N O hU-4 o w o m u u u uv) m m u w w m m P I m m u m m u m m m m m 2:: ?IY ? ? ? m m m m m .I.. . . 0 0 0 d d d dlddd 0 0 0 0 0 0 0 0 0 o o o o c . . . 3 m m ~ m u m m

a o o o . . . .

m m

o(* q2

N w r l m O N ~ U N u.2: m m u m m .I.. . . 0 0 0 0 0 0 0 0 0 0 0 0 0

d u m u m u . I . .

0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 m m m m m m m m m m m m m m

m m v ) mv)- mimmm I I 0 0 0 0 m m m v )

w m u c ;

m u ? ? ?

. . . d N 4 d

m c o u P -

3 0 0 3 . . m c : c o ~ W P - h e d m m m m

u u u u u u u m m m m m m 0 0 0 o c a 0 0 0 0 0 0 0 . . . . . . .I.. . . . .

P - o m v ) u u u u 0 0 0 0 . . . . . . . . . . .

u c m ? ? I ? 0 0 0

N r - m o d0dr -u u m u u 0 0 3 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 N "N N N N N N

. . . . . . u u f ? m - m .

0 0 0 0 N N N N ooc 0 0 0 0 0 0 0 0 0 0

N" N" N N N N N N N I 3 N

0

rl

U

(7

rl 4

0

U

d

h

0

N d

C

m L-l N

m

3 3.

N h

C

:: c

?I9 9 ? ? ? ?9??c . m m m m r l N m m u u - N u U r n l * N d d N U U U U 9 9 9 ? ? ? m . ? ? ? 9 9 9 I I Y??".

d U "

m d m m . O d O C

0 3 3 0 . . . .

m a a m d d d d . . . .

N I I

m m C . . N d I 1

. 0 0 0 4 0 0 0 1: I

hl

0 I ?

o m 0 . .

4 0 I 1

m m 0 9 d I

m N drl

0 0 . . m d r l o d

0 0 0 3 0 9???1 I m m m m

0 0 0 0

d d d d _ I . . . w m ~ ? ? ? 0 0 0

W P - C O

0 0 0 9 9 9

m m o m d d d d

a o o o

r l r l m r l m m m m F I N "

. . . . u * d d 0 ' I j

m o m

0 0 0 ".?

c ~ o m m o d o y . . . 0 0 0 3 1 1 1 1

u u m 3 m m c o c ~ m m o ~ ~ o o o w ~ m m u o m m m m

I l l I l l I I I I I I I I I I I l l 1 1 1 1 1

. . . . . . ? ? 9 9 ? ? " . ? ? 9 9 9 ? ? ?".??9 0 0 0 0 0 0 0 0 0 0 007 0 0 0 0 000 0 0 0 0 0

d e w o r l a P I m m u u u e u m u m u m u U m m N m N d d N d r ( dP-P-P- P - b P - P I P - P - P - P - P - I - P-hP-P-h . . . . . . . . . . . . . . . . . . . . . . . . N-" N" N O 0 0 d o 0 0 0 0 0 0 0 0 0 0 0 0 0

m 4 a r - i P - P - P - P -

0 0 0 3 . . . .

* c V I w pipi u u

* * u * * * m m m L C P . u o u

\ o w I I

PIU P-c O d I I d d

P-P- 4 4

w w w w w a w e I l l I l l

P I O N P I O N w m m w m m 0 0 0 3 0 0 I l l I l l 44-4 d d d

2 2 2 2 2 2

w w \ o w I 1 I I w d w r ( m m m m 0 0 0 0 I I I I d d d d PIP- P-P- 4.4 u u

w w I I

m d m m 0 0 I I d d

PIP- 4 u

- 0 O d I I d d P - h 4 U

r-alna N N N N

o u w 4 N O 0 4

4 4 4 d

O N U l n

--us r - - 0 4

0 0 0 0

. . . .

. . . . am;?

? 9 ? ?

. . - - -

0 0 m l n

rlrl

m m

0 0 0 0 l n m l n l n 0 c c o m l n l n r n

W N N N

N m m m . . . . . . m 0 w w

4 N 4 4 . . . .

0

t:

m s m m Y ; . D m m o o c o

N c O N h m u u u o s 0 0

. . . .

. . . . a o c m c m u m . . . . 0 o c 0

0rlo.D alnuu 000s . . . .

c ~ r l a m c u m m . . . . 0 0 0 0

m m u h u m m m 0 0 0 0 . . . . 0330 "NN

o = F - l m u 4"N

r-clnx N m u m

c L o 0 c 3 4 0 4 0

0 3 0 0

. . . .

. . . .

. . . . ~ m - 4 4 d N N

m m .o . 0 0

. . . .

m h d m 9 9 2 9 c o o c

m h h b U7hr-r- N m m m

n x m w

a 3 0 0 I I I I

5 9 9 9

N o m m r-hr-r-

c o o 0 . . . .

Cd $ 4 4 3

o o o c NN"

0 0 N N

a\o

N N

c.9 c u

r - o m r - 4 N d - l

o c o c u m m m

r - 4 m 4 4 4 c 4 c c o o

. . . .

. . . .

. . . .

0 3 0 0 " N N

a 0 4 4 N m m m

. . . . . . m o l n m . . . . m 4 l n m

o c c c

0 0

a\D m N N N e -

m o f f i o 4 4 c 4 O O C O . . . .

m m r c . m m l n m m N N N N

0 0 2 0

- 1 1 1

U 4 O N h r - W P -

0 0 0 0 . . . .

m m 199

0 0 I I

4 4 PIPI

I . . 0 0

c: m m m >

U

c o m w m 9 9 9 9 0 0 3 0 I l l 1

mr-uUY r - r - r - r -

o o s o . . . .

m w m I . . .

N N N

I 0 0 0 l n m m

c o o \oaa

I . . . 0 3 0

w c O m u G u I . . .

C O O

bar- u u u I . . .

0 0 0

100s N N N

I 1 3 t

m m

0 0 1193,

m m m m m m m m N N "

m N N N r - r - h r . 0003 . . . .

cc u u c > <

a a a I l l

h O N w m m

r - u w \ o N m m m

u u a l n

r lddr l

h N m m m l n l n m

. . . . ? ? 9 9

. . . . ^ ^ ^ ^ V V V "

m d O 4

3 3 0 0

m m l n m _ I . . .

*u l n W O h . . .I.. . m m m m u m

r-r- r ( w x m u*u u u u u . .I.. . c o 0 0 0 0

m m m m x r - u u m u u u 0 0 0 0 0 0 . . .I_. .

0 0 " 1 1 I I 0

\3\o IQ \o

m m . . m m

0 0

4 4

m m m m e e u u m m 0 0

0 0 l n m

?".

. .

. .

moo . . N N

m m \Do 0 0

0 0

0 0

. . ? ?

3: m m

0 0

0 0 m N

caw N N

l n m c c

u u

0 0

. .

. . 9 9

mc, N N

m m 0 0 I I

m l n

0 0

hhr- hhr- m m m

. .

. . I 9 9

m m 199 c o I I

4 4 r-h

I . . 0 0

oc u u >

4

L o a I I m m

m n 0 0

a F

2 r

U U

C P U

C

C

r

P

r U

C

a 7

C r

C 4:

C

C P

P

r

U C C

c @

U

C

U C C

r r P

c

C

7 r r

!

w o o l 0 4 0 . . .

u o r .

r l 4 4

- 3 3 L 1 \o m 3 0 0

4 N 4. . . . . .

N rl ra m m m 0 0 0 . . .

c o o m m m

bar. o o c . . . m a n i s m m 3 0 2 . . . c u r . m u u 3 c c

\- N m u u u a = =

. . .

. . . c o o N N N

L7 L 1 m

c o o . . .

c.?? C I 4 rl

r. L 1 s

D o c c 0. 5

m m l r 0 3 c

. . I

m v

s c I 1

c lr. G 3 c c 2 = =

0 .

. . m x a r.r.,- 4 4 -

m c u C l . 4

c 0 c I l l

. .

m o u N N P

N N P . .

1 r l N :

z z c c)

c P’

3 4

I 4 h

-t

P - l 3

A N N . . .

u u u

4 4 - 0 9 9 9

N N N m m m 000 . . .

m r - w rf u u 0 0 3 . . .

c c 0 m m m

3 N - l

5 4 4 . . .

h m 4 m o o c = o . . .

h C 0 u m u 0 c o

u m m

. . . 5:“. ^ C ^ V I I

000 N N N

G. r? 0

E?:

. . c c o

m N m

F-Uo

0 3 c 9 9 9

- m u u - c . . I

^ ^

= c c

c m - r 4 - l -

c = c

d 4 - PIPIP

. . I

N rd P\

P I U C c 4 r 3 c c 1 1 1

. .

F - m u r.r.r

3 o c . .

< -IN;

* U e

9 I 0 o 0

rl r. <

mom. o u r . m . . . . . . 4 4 4 N r l 4 4

S U N O N 0 u 4-44 r l N 4 rl

4 4 - l 444 4 . . . . . . .

mr.m r n 4 P r. m m m m o m m d d d d d d d u m m m o m W . D N u m m . N m . . . . . . c o o 0 0 3 0

3 0 0 o c 0 c m m m m m m m

4 m x u - 4 3 4 c o 4s- i 0 . . . . . . . m m N r D W N N m * \ D m o o o o c a C O G c . . . . . . . r.Nc m u c c

0 c c c c 0 0

unr. C N U o

u m n m u m m * m . . . . . . 5:: 030 7 : : C O G 5 0

o o c 0 0 0 N N N N N N

m m t n m m q m . . . . . . 44-4 m c m N

a 4 m 0 4 o m = c 3 400 c . . . . . . . 0 0 3 0 . . m a ‘3

r l c c I I I

N O S m m m t: c0r.r. j3r.r. r

000 0 0 0 c . . . . . .

o o .Do I I I 1 u o u\D .Do a m 0 0 0 0 I I I I rl r. <

-4NrsI.N r. i f 4 -4 I n A L n U I n L " -3 rclm m . . . . . . I ) . . . c c c c c c = a c

m r l u 4 . i ti C I N 4 . . . . . . ) I . . . c r l r l r l i d rlti 4

c m m c I . . . .

m m c m

In r lcc

c c c c 1 ?- !?c.?

r.r. r.

c - I I I I .-. -.

m m c h m m . I . . . . .

rl rl N d r l -4

m m m h a r. m m m m m m

. I . . . . . c 0 3 0 0 0

c c c o 3 c 0 m m I n m m m m

r l = o m m m r. m m I n In

C O O c c c 0 . . . .

C C I n r.r.r. a u u u u u u C 3 O 0 2 0 c m m r J c m m 0

e c c C S C =

. . . . . . s 4 m. if. u if .4 u . . . . C S D o c c 0 "N N N N N

O C I b o u r . r. r l O C c c o 0 . . . . . . .

U C I U mmr. L?

c c = o = c O . . . . . . .

V I 0 4 . C . c c = . c o 0 I I

m m i o r.r.2 P-

93.9 9 3 . Y 3. 3 C 0 C C C 0

3 3 m = a m m "N N N N N x m x m m n P

c c m m m r . a - m a c o o a c c o c o o 0 I l l I l l I

. . . . . . .

= m u N O 0 m ms-lr4 m-4.m N

N N C J N N N N . . . . . . .

$ 4 K. V:

C C u u

u m u 40- (1 . . . . . . . N N N N N N N

m -: PI 5. p' z L,., u m m m m m m 0 0 0 0 3 0 0 . . . . . . .

c o o l n m m 0 3 3 m m m 3 m

m u 0 m m m m m o a m m l n m 0 c c c o o 0 . . . . . . .

u r l m r.r.r. m u m u . . . . . . uuu. u

m . . u u. m. u. us u-

D C O c c o c

m I n N m a r l 4

o 3 c c 3 o 0

c o c 0 0 0 0 N N N N" N

r l m m c u r l c . . . . . . . -4co a 4 4 4

m m l n 4 r l 4 0 0 3 . . . o??? c:

u m . 4 4 3 4 rlrlrl 4 , . . 953 . ?

o ln o m m \D . C . . . . . I- m l n N m m

I I I I I I

m m m s ~ m m m m m m c j x m m N N N N N N N

m ~ m o x r l u . . . . . . . m r t m m -4-494 44-4 4 I l l I l l I

m c u h r l m N n m m m m m 0: . . . . . N N N N" N

i o - \Do I 1 1 1 m u m u o m o m a 0 0 0 I I I I

Unclassified

I . O R I G I N A T I N G A C T I V I T V (Colporale author) 2.. R E P O R T S E C U R I T Y C L A S S I F I C A T I O N

U. S. Army Engineer Waterways Experiment Station Unclassified V i cksburg , Mississippi Zb. G R O U P

I 7.. T O T A L N O . O F P A G E S 7b. N O . OF R E F S 6. R E P O R T D A T E

December 1971 89 10 ea. C O N T R A C T OR G R A N T NO. 0.. O R I G I N A T O R ' S R E P O R T N U M E R I S )

PERFOFMANCE OF THE BOEING LRV WHEELS I N A LUNAR SOIL SIMULANT; Report 2 , EFFECTS OF SPEED, WHEEL LOAD, AND SOIL

4. D E S C R I P T I V E N O T E S ('IYpa o f r e v 1 end Inslumlva date.)

5. A U T H O R I S ) (Firat nmm. middle lnlllal, laat nmm) Report 2 of a s e r i e s

Klaus-Jurgen Melzer

C .

d.

Ob. O T H E R R E P O R T NOIS) (Any oth*tnMb.ra Phalo.Y bo aaa1m.d lhla Npot?)

Technic 61 Report M-71-10 I b. P R O J E C T N O . I

1 1 . S U P P L E M E N T A R Y N O T E S ~

11. SPONSORING M I L I T A R V A C T I V I T Y

George C . Marshall Space Fl ight Center National Aeronautics and Space Administra-

t ion , €iuntsville, Alabama

Approved fo r public re lease; d i s t r ibu t ion unlimited I

Security Classification

~- L I N K A

O L E - 3

W T - -

L I N K C