Vivake Asnani, Damon Delap, and Colin Creager

Glenn Research Center, Cleveland, Ohio

The Development of Wheels for

the Lunar Roving Vehicle

NASA/TM—2009-215798

December 2009
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Vivake Asnani, Damon Delap, and Colin Creager

Glenn Research Center, Cleveland, Ohio

The Development of Wheels for

the Lunar Roving Vehicle

NASA/TM—2009-215798

December 2009

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135
Acknowledgments

The authors would like to thank Professor Jo Wong, Dr. I. Robert Ehrlich, Dave Glemming, Jack Brown, Ron Creel, and 

Anthony Young for reviewing this manuscript. Special thanks to Ferenc Pavlics, Sam Romano, Don Friedman, and

Nick Di Napoli for telling us this story and then fi elding the barrage of questions.

Available from

NASA Center for Aerospace Information

7115 Standard Drive

Hanover, MD 21076–1320

National Technical Information Service

5285 Port Royal Road

Springfi eld, VA 22161

Available electronically at http://gltrs.grc.nasa.gov

Trade names and trademarks are used in this report for identifi cation 

only. Their usage does not constitute an offi cial endorsement, 

either expressed or implied, by the National Aeronautics and 

Space Administration.

Level of Review: This material has been technically reviewed by technical management. 
NASA/TM—2009-215798 1

The Development of Wheels for the Lunar Roving Vehicle 

Vivake Asnani, Damon Delap, and Colin Creager 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Abstract 

The Lunar Roving Vehicle (LRV) was developed for NASA’s Apollo program so astronauts could 

cover a greater range on the lunar surface, carry more science instruments, and return more soil and rock 

samples than by foot. Because of the unique lunar environment, the creation of flexible wheels was the 

most challenging and time consuming aspect of the LRV development. Wheels developed for previous 

lunar systems were not sufficient for use with this manned vehicle; therefore, several new designs were 

created and tested. Based on criteria set by NASA, the choices were narrowed down to two, the wire 

mesh wheel developed by General Motors (GM), and the hoop spring wheel developed by the Bendix 

Corporation. Each of these underwent intensive mechanical, material, and terramechanical analyses, and 

in the end, the wire mesh wheel was chosen for the LRV. Though the wire mesh wheel was determined to 

be the best choice for its particular application, it may be insufficient towards achieving the objectives of 

future lunar missions that could require higher tractive capability, increased weight capacity, or extended 

life. Therefore lessons learned from the original LRV wheel development and suggestions for future 

Moon wheel projects are offered. 

1.0 Introduction: Wheels on the Moon 

In the early 1970s, three types of wheeled vehicles were used on the lunar surface. The missions for 

these vehicles were completely different, and accordingly they had dissimilar wheel designs. For 

comparison, Figure 1 lists the characteristics of these vehicles (Fig. 1(a)) and their wheels (Fig. 1(b)). The 

first was the Russian made robotic rover called Lunokhod (‘Moon Walker’ in English). This was an 

800 kg remotely controlled vehicle that traveled at a maximum speed of 2 km/hr. Lunokhod had eight 

rigid-rim wire mesh wheels, with bicycle-type spokes. The second vehicle, which was American made, 

was the Modularized Equipment Transporter (MET), a two-wheeled unpowered cart used to carry 

equipment and samples collected by the astronauts on Apollo 14. The MET was about 75 kg when 

loaded, and was pulled at speeds up to 4 km/hr. Its wheels were made of smooth rubber, and were 

supported by nitrogen filled inner-tubes. To make it easier to pull the cart through soft lunar soil and over 

rocks, the MET wheels were designed to be fairly compliant. The last vehicle to visit the Moon was the 

Lunar Roving Vehicle (LRV). This was a manned vehicle that could sustain a maximum speed of about 

16 km/hr and had a total mass of approximately 700 kg when fully loaded (unloaded mass was 210 kg). 

The LRV had a 44 configuration (4 wheels, all driven) using large flexible wire mesh wheels with stiff 

inner frames to prevent over-deflection. Thin tread strips were attached to the carcass to enhance 

floatation in soft lunar soil yet still allow the carcass to deflect. Although each of these wheel designs 

were distinctly different, they all adequately served their respective functions. 

Unfortunately, very little of the lunar wheel technology was transferred to the private sector. This is 

because there are no Earth applications with similar mission and environmental constraints. Some of the 

special considerations for lunar wheel development are: 

 Restricted transport mass and volume. 

 Potential variation in temperature from approximately 40 to 400 K (–230 to 130 °C). 

 Exposure to solar radiation without atmospheric protection. 

 Rolling and sliding contact with un-weathered regolith and dust particles. 
NASA/TM—2009-215798 2

 Operation in a hard vacuum. 

 Operation in a low gravity field (1/6th Earth’s gravity). 

With the new initiative to inhabit the Moon, wheels will be needed for exploration, construction, and 

other surface operations. The designers will need to learn how to satisfy the unique environmental 

constraints and meet the transportation requirements of a given mission. To facilitate this effort, the 

development process of the LRV wheel was studied and is reported in this article. From this account, 

lessons learned are documented and suggestions for future work are offered. 

2.0 Development of the LRV Wheel 

The contract to develop the LRV was awarded to The Boeing Company in October of 1969 and the 

first flight vehicle was delivered to NASA in March of 1971. General Motors (GM) was the major 

subcontractor for this project. Throughout the 1960s GM’s Defense Research Laboratories (GM DRL) 

invested time and resources to develop a wheel that would work for such a mission. Based on a detailed 

review of the literature, as well as interviews with several original GM DRL team members (Pavlics 

2007a/b), a retrospective account of this development is conveyed below. 

2.1 Genesis of the Design Concept 

SLRV (1963 to 1964): In 1963, GM DRL teamed with Goodyear Tire & Rubber Company 

(Goodyear) to develop several prototype wheels for the Surveyor Lunar Roving Vehicle (SLRV). This 

was a small teleoperated rover that was intended to scout the lunar surface before the Apollo program. A 

few of these wheel concepts are shown in Figure 2. The commonality between designs was the carcass 

configuration, which was formed with wire and resembled the cord structure of a bias tire. At the 

intersections, the wires were looped to maintain their spacing and still allow for pantographing (pivoting 

action that occurs between tire-cords when the carcass is deformed). The wire frame wheels were well 

suited for the lunar application in several ways. Primarily, they were compatible with the lunar 

environment. The compliance of these wheels could be tuned by varying wire thickness, bias angle, and 

number of wires. They could be designed to deform significantly, thus providing high tractive capability, 

even under the relatively low weight of lunar vehicles in 1/6th gravity. In addition, the wire frame wheels 

could be made very light by only partially covering the carcass (e.g., Fig. 2(a) to (c)). As such, several 

coverage schemes were tried to balance the weight reduction and tractive performance. The partially 

covered configuration also prevented clogging between tread pieces, since soil was free to flow in and out 

of the carcass. These wheels solved several of the fundamental problems associated with lunar wheel 

design; however, they had low fatigue life due to stress concentrations at the looped intersections. The 

SLRV program was eventually cancelled because of concern that it might interfere with the Apollo 

missions. 

MOLAB (1964 to 1965): NASA next sponsored the study of a Mobile Lunar Laboratory (MOLAB). 

This was a large pressurized vehicle to be used for long range exploration after the Apollo program. GM 

DRL and Goodyear again worked together and made a larger wire frame wheel with higher load capacity. 

However, they found that the wheel design could not easily be scaled to accommodate a higher load. For 

example, increasing the wire diameter elevated the stresses at the looped intersections, while increasing 

the number of wires made the wheels difficult to manufacture by hand. Working within these limitations, 

the prototype shown in Figure 3 was made; however, the wheel carcass was unable to support the vehicle 

weight. To fix this problem, a method to weave the carcass was developed at GM DRL using the process 

illustrated by Figure 4. As shown, the wires were precrimped at fixed intervals. In this fashion, they held 

their position in the carcass without excessive stress. Additionally, the manufacturing process enabled a 

much tighter spacing between wires. 

MTA (1966 to 1967): NASA sponsored GM DRL to build a Mobility Test Article (MTA) as a way to 

simulate the mobility performance of the MOLAB rover. This was essentially a 66 chassis that had the 
NASA/TM—2009-215798 3

same weight on Earth as MOLAB would in lunar gravity. The vehicle had large (~152 cm) wire mesh 

wheels and was tested on hard surfaces at the Army’s Aberdeen Proving Ground, and then on desert 

terrain at their Yuma Proving Ground (Smith 1967, Northon 1967). The mesh wheels worked fine at 

Aberdeen but did not survive testing over the rocky terrain at Yuma. High speed impacts broke wires, and 

the mesh carcass was permanently dented while crawling through a boulder field. After this, rubber inner 

tubes were used to prevent overdeflection of the carcass during testing. In later versions of the wheels, the 

rubber inner-tube was replaced by a titanium inner-frame, as shown in Figure 5. Tread strips were also 

added to the carcass for protection. The tread pieces were arranged in a chevron pattern, which helped 

provide side-traction and prevent the wheel from drifting. 

To enhance the forward thrust capacity, large spaces were used between the tread. The inspiration for 

this came from the so-called ‘spaced link track’ that was investigated in the early 1960s by Dr. M.G. 

Bekker (Bekker 1960). At the time, there were several conflicting hypotheses about the trafficability of 

the lunar surface. It wasn’t clear if the terrain was strong enough to support a wheeled vehicle; therefore 

alternate running gear types such as screws and tracks were investigated (Bekker 1962, Bekker 1963). 

Figure 6 shows three small scale prototype lunar vehicles that were studied. The spaced link track is 

shown at the right of the picture. In principle, the spacing between its cleats created a longer shearing 

surface that extended deeper into the terrain and thus developed more traction than a continuous footing. 

The phenomenon is illustrated in Figure 7. Here cleats 1 and 2 were loaded and translated in sand, while 

filmed from behind a glass wall. The camera was moved alongside so the sand grains that traveled along 

with the cleats stayed in focus while the stationary ground underneath was distorted. Soil was sheared off 

and carried between cleats 1 and 2, causing shear displacement to occur, and thus shear strength to 

develop along surface a to b. In the open space behind cleat 2, a much longer shearing surface, b to c, was 

produced, yielding greater thrust development. 

The wire mesh wheel concept that incorporated all of the technology developed at GM DRL up to 

1967 is shown in Figure 5. This wheel was the subject of extensive evaluation and testing before finally 

being configured for the LRV. 

2.2 Comparative Evaluation 

LSSM (1966 to 1967): After MOLAB and GM DRL was subcontracted by Boeing to investigate the 

Lunar Scientific Surveyor Module (LSSM) for NASA. This was a two-astronaut unpressurized rover 

concept. To determine the relative merit of the wire mesh design, it was analyzed along with other 

candidate lunar wheels. 

2.2.1 Concept Selection 

In all, eight wheels were selected for the preliminary analysis, as shown by the matrix in Figure 8. 

Most of the wheels evaluated were those considered seriously for lunar exploration by major companies. 

Rigid rim and pneumatic wheels were also included in the analysis, because they were commonly used on 

Earth. 

To build and test all eight wheels was impractical, so a combination of analytical techniques, simple 

experiments, and engineering judgment was used. For example, soft ground performance was estimated 

by assessing the terrain contact geometry and then calculating thrust and motion resistance using the 

Bekker method (Bekker 1969). Results showed that large ground contact length was key to lowering 

motion resistance and increasing thrust. The spacecraft volume limited running gear dimensions, so a 

flexible wheel carcass was considered paramount to achieving the long footprint. 

In each of the categories, a score between 0 and 10 was assigned. Additionally, each criterion was 

designated an importance weighting factor, according to a manned mission scenario. The total score was 

calculated for each wheel, using a weighted average of the category scores. Though pneumatic wheels are 

most commonly used on Earth, they were disregarded after receiving a null score in the environmental 

compatibility category. This was because of the risk associated with deflation in the airless lunar 

environment, as well as potential rubber degradation due to solar radiation (Bekker 1985). The other 
NASA/TM—2009-215798 4

design with terrestrial heritage, the rigid rim wheel, was also disregarded because of its null score in ride 

comfort. Overall, the wire mesh wheel was rated highest, while having no prohibitive low scores. It was 

also rated best in weight, ride comfort, and obstacle performance. Second best was the hoop spring wheel, 

which was tied for the highest soft ground performance rating with the spiral spring wheel and hubless 

design. These two designs, the wire mesh and the hoop spring, were selected for further development and 

experimental analysis. 

2.2.2 Developmental Program 

To characterize and further develop the wire mesh and hoop spring wheel concepts, GM DRL used a 

design-test-redesign-retest approach. The developmental program is outlined in Table 1 (GM 1967). 

Initial versions of both wheels were built according to the LSSM mission requirements shown in Table 2. 

These wheels were put through mobility and mechanical tests to determine their limitations. 

Concurrently, tensile strength, fatigue, and vacuum welding tests were done on several candidate 

materials. From the wheel performance and material evaluation data, design changes were made. The 

improved wheels were reevaluated in the mobility and mechanical test rigs to determine their relative 

performance. Finally, a mission simulation was performed under lunar thermal-vacuum conditions using a 

wheel dynamometer. At the end of both phases of testing, final recommendations were made for further 

improvements to both wheels designs and technical drawings were produced. The methods and results 

from this program are summarized below. 

2.2.2.1 Initial Wheel Designs 

The initial wire mesh (MESH-1) and hoop spring (HOOP-1) designs were scaled versions of the 

MOLAB wheels developed by GM DRL and the Bendix Corporation, respectively (Boeing 1965, Bendix 

1965). The prototypes were built in-house to gain an understanding of the manufacturing processes. 

Figure 9 shows pictures of these wheels. 

The MESH-1 wheel had a woven spring-steel wire mesh carcass with tread strips, a titanium inner 

frame, and an aluminum hub and wheel disc. Its carcass was designed to support the load of the vehicle 

under nominal conditions, and the inner frame served as a secondary spring and deflection boundary for 

the mesh during impact loading. The mesh structure distributed the load throughout much of the carcass 

by globally deforming. The tread pieces provided additional contact area for floatation, and were indented 

to developed traction through general shear failure (e.g., Fig. 7, surface b to c). 

The HOOP-1 wheel consisted of a titanium outer band, hoop spring elements, and a rigid aluminum 

hub with spokes. Under nominal loading, the outer band and hoop springs carried the load locally. Other 

than the rigid aluminum hub, no deflection limiting devices were incorporated. The contact patch of the 

wheel was relatively large and uniform, which facilitated floatation. No tread was used and so the traction 

depended on friction at the metal to soil interface. If the friction was high enough to mobilize the soil, 

then traction would develop through local shear failure (e.g., Fig. 7, surface a to b). 

Mobility Testing: Initial testing was done to benchmark soft soil performance. Each wheel was 

subjected to drawbar pull, rolling resistance, and steering resistance testing. All of these tests were done at 

100, 150, and 200 percent of the nominal design load. Two types of soil were used; the first was a course, 

dry sand, and the second was a very soft, fluffy material called Perlite. These materials were used to cover 

the range of surface conditions estimated by NASA in their lunar surface model (Mason 1964), which 

was based on the Ranger mission photographical data. 

The resistance in sand for both wheels was very close at the design load. However, with increasing 

load, the rolling resistance of MESH-1 grew faster than for the HOOP-1. This trend was more apparent in 

the softer Perlite. There were no significant differences in steering resistance between the two wheels at 

nominal loading. Finally, under all conditions, MESH-1 developed more drawbar pull than HOOP-1. 

Because of the fact that there was no significant difference in the rolling resistance of the wheels, the 

higher drawbar pull developed by MESH-1 was attributed to greater thrust development. It was postulated 

that HOOP-1 could not develop as much thrust as MESH-1, because the friction between the metal and 

soil was too low, and the wheel slipped at the interface. Similarities in the steering resistance results were 
NASA/TM—2009-215798 5

explained by examining the geometric characteristics of the wheels. The sharp edges of HOOP-1 cut 

through the soil, while MESH-1 had a rounded contour that helped mitigate soil buildup in the travel path. 

Mechanical Testing: Several tests were done to characterize the mechanics of the wheels and find 

their structural limitations. Load-deflection tests were performed in the vertical, lateral, and longitudinal 

directions, while recording the contact geometry of the wheels. Following this, a dynamic checkout was 

done to observe the wheel response at operational speeds and torques. Impact endurance testing was then 

performed with single and random obstacles. Finally, the wheels were endurance tested on a smooth 

surface for up to 75,000 revolutions. 

Several limitations of the hoop spring wheel were revealed during this testing phase. While 

dynamically testing HOOP-1, significant vibration, or “flutter”, was observed in the outer rim at critical 

speeds. Additionally, it was unable to develop high torque on the treadmill surface. During the single 

obstacle tests, the hoop springs became overstressed and failed. As such, an identical hoop spring wheel 

(HOOP-2) was fabricated to continue the mechanical testing. In the endurance tests, the hoop springs in 

HOOP-2 began to fail at about 18,000 cycles and the test was terminated at 28,000 cycles when more 

than half of the hoops had failed. As such, no further mechanical testing on the initial hoop spring design 

was performed. It was observed that the wheel failures seemed to initiate at the hoop spring attachment 

points. At these locations, a slight reverse bending occurred and stress concentrations formed around the 

riveting holes. 

Wheel MESH-1 was relatively stable during the dynamic checkout test. However, during the 

endurance test the wires in MESH-1 began to break at 19,000 cycles, and more than 10 percent had 

broken by 27,000 cycles. At this time, it was observed that most of the wires broke in line with the ends 

of the tread strips. It became clear that the tread strips did not allow the tread and the mesh to move 

independently during the deflection of the wheel; thus, the wires were being overstressed. To continue the 

testing, a refurbished mesh wheel (MESH-2) was built. The tread strips were segmented at the riveting 

points to allow them to pivot, and as a result, alleviate the added stress to the wires. The new wire mesh 

wheel successfully completed the endurance test and the random obstacle test without any failures. 

2.2.2.2 Materials 

Material level testing was done concurrently with the initial mobility and mechanical evaluation. The 

purpose was to assess eight candidate materials for the wire mesh wheel carcass and to verify the 

adequacy of the titanium alloy used for the spring elements and outer band in the hoop spring wheel. 

Three samples of each material were subjected to tensile strength, fatigue, and vacuum welding tests. 

Results from the tensile tests verified the published values for yield and ultimate strength. Five of the 

eight wire materials endured representative bending stresses for over 300,000 cycles, or three times the 

required wheel life. However, of all the wire types tested, standard music spring wire was the least prone 

to vacuum welding. It was also observed that the effects of vacuum welding did not degrade the 

performance or fatigue life of the music spring wire. The titanium material being evaluated for the hoop 

spring wheel also lasted 300,000+ stress cycles, and there were no significant vacuum welding effects. 

2.2.2.3 Improved Wheel Designs 

Improved hoop spring (HOOP-3) and wire mesh (MESH-3) wheels were built according to 

recommended changes from initial testing, and had the following features: 

HOOP-3 

1. The titanium alloy continued to be used for the hoop springs and the outer band. 

2. To lower operating stresses, the hoop springs were made thinner, they were elliptically preformed, and twice as many were used. 

3. The outer surfaces of the hoop springs were shot peened to improve fatigue life. 

4. A bump stop was added to limit the deflection of the hoop springs. 

5. To increase the thrust development, two alternate tread configurations were tried, a sand paperlike grit and 0.6 cm high aluminum grousers. 
NASA/TM—2009-215798 6

MESH-3 

1. Standard music spring wire was used for construction of the mesh carcass. 

2. Segmented tread pieces continued to be used with additional tread pieces 

added to help with floatation. 

Mobility Testing: The mobility test procedures were repeated on HOOP-3 and MESH-3, except they 

were not tested in the Perlite material. At this point, additional observations from the Surveyor missions 

(e.g., see Vaughan 1967) indicated that only a thin layer of the soft, fluffy material covered the lunar 

surface. It was decided that this layer would not affect vehicle mobility. 

For the most part, rolling resistance tests for both wheel types showed no significant differences from 

the initial testing. However, with the addition of the grit to the tread, the drawbar performance of 

HOOP-3 was significantly improved over HOOP-2. The addition of grousers yielded no further benefit, 

except at high loads and high wheel slip. With the additional tread pieces, the drawbar pull developed by 

MESH-3 was slightly higher than MESH-2, but shy of that produced by either improved hoop spring 

wheel design. 

Since the motion resistance of the MESH-3 and HOOP-3 did not change, their improved drawbar 

performances were attributed to increases in thrust. The increase in thrust for MESH-3 was credited to the 

larger tread surface taking advantage of a small amount of cohesion in the sand. This cohesion was 

assumed to be a result of the ambient moisture conditions and could not be relied on for propulsion in the 

lunar environment. The significant increase in thrust for HOOP-3 implied that the wheel was no longer 

slipping at the wheel/soil interface. Finally, it was postulated that HOOP-3 generated more drawbar pull 

than MESH-3 because it had a larger contact patch and could take greater advantage of the cohesive 

terrain strength. 

Mechanical Testing: The mechanical testing done during the initial testing phase was repeated on 

HOOP-3 and MESH-3. HOOP-3 reached 55,000 cycles with 10 percent of the spring elements breaking. 

Again, most of these breaks initiated where the hoop springs were fastened. MESH-3 reached 85,000 

cycles with 10 percent of the wire breaking. However, the wire breaks occurred where the single-obstacle 

repeatedly struck the wheel. This round of testing indicated that wheel lives were extended by the design 

changes, although the endurance of HOOP-3 was still limited by stress concentrations at the loop 

attachment points. 

Simulation: Final tests were performed to evaluate how the wheels would operate under simulated 

lunar environmental conditions. For this purpose, two new wheels (HOOP-4 and MESH-4) were 

constructed, which were identical to HOOP-3 and MESH-3. A special wheel dynamometer, shown in 

Figure 10, was constructed to be used inside a thermal-vacuum chamber. The wheels were operated under 

nominal loading on a smooth surface (steady-state mode) and over obstacles (dynamic mode) with the 

duty cycles of wheel torque and speed controlled to simulate the LSSM mission profile. 

The cycles accumulated in the various modes of testing are outlined in Table 3. Although the testing 

cycles were not equivalent, both wheels were run until failure in the dynamic thermal-vacuum mode. The 

failure modes were the same as in previous tests; the wires in the mesh wheel failed in-line with an 

obstacle, while the hoop spring wheel failure originated at the spring hoop attachment points. As in the 

previous tests, the wire mesh wheel lasted quite a bit longer. 

Conclusions of Testing: From the test program with the improved wheel designs, the following 

conclusions were drawn: 

Hoop Spring Wheel 

1. This design suffered from excessive vibration, or flutter, at critical speeds. 

2. The addition of grit effectively increased the wheel-terrain friction and enhanced 

the thrust capability. 

3. The bump stop successfully prevented overdeflection. 
NASA/TM—2009-215798 7

4. The modified hoop springs resulted in sufficient fatigue life for smooth surfaces. 

5. Reverse bending of the hoop springs still occurred when rolling over sharp obstacles. As a result, 

fatigue was inadequate for the LSSM specifications. 

Wire Mesh Wheel 

1. Soft soil performance of the improved wire mesh wheel was slightly inferior to the improved 

hoop spring wheel. However, the difference was attributed to cohesion in the sand from the ambient 

moisture, which could not be relied on to aid propulsion on the Moon. Thus, soft soil performance was 

deemed equivalent to the hoop spring wheel. 

2. Obstacle course endurance testing revealed that this wheel would not quite satisfy the 100,000 

cycle LSSM requirement for life. This was attributed to repeated striking of the same locations on the 

wheel. The life during an actual mission would be greater due to the randomness of natural obstacles. 

3. The wheel life could be extended significantly by lowering the wire stresses. It was recommended 

that smaller diameter wires be used in future wheel designs. Additionally, it was suggested that the tread 

strips be made wider to protect the sidewalls from impact damage. 

2.3 Configuration for the LRV Missions 

LRV (1969 to 1971): In July of 1969, NASA released the request for proposals (RFP) to develop the 

LRV. This document specified the operational requirements, as well as the mass and volume limitations 

imposed by the landing spacecraft. As the mobility system subcontractor to Boeing, GM DRL assessed 

the vehicle specifications and translated them into wheel requirements. Results from the experimental 

development program indicated that the wire mesh wheel design was better suited for this mission than 

the hoop spring wheel. Most notably, the wire mesh wheel would offer superior stability, ride comfort, 

and had a better chance of meeting the life requirements than the hoop spring wheel. As such, the wire 

mesh design was selected and configured for the LRV mission. The configuration process is not exactly 

known, but has been inferred from the literature (GM 1970a/b, GM 1971) and technical discussion with 

former LRV team members (Pavlics 2007a/b). The presumed configuration process based on NASA 

mobility requirements for the LRV is outlined in Table 4. The terramechanics aspect of the wheel design 

and testing is described in detail below. After the LRV wheel design was finalized (Fig. 11), it was 

handed over to NASA for mobility subsystem space qualification. More information on the LRV 

subsystems can be found in (Young 2007). 

2.4 Terramechanics Configuration 

The most challenging factor in the wheel configuration was the vehicle requirement to climb a 25

slope for a 0.5 km distance. The wheel needed to generate enough thrust to overcome its internal 

resistance, the gravitation resistance, and the resistance due to terrain compaction. As mentioned 

previously, Bekker’s method of analysis (Bekker 1969) showed that the most influential design parameter 

was the ground contact length. However, since the LRV wheel geometry was maximized for the given 

spacecraft volume, the contact could only be lengthened by increasing the carcass deflection. The 

equations reported in (Pavlics 1966) were used to relate the nominal wheel deformation to climbing 

performance. The primary assumption was that the ground contact was rectangular, with uniform pressure 

distribution. Clearly, this was not the case for the complex geometry of the LRV wheel; nevertheless, the 

method provided an approximate solution for studying tractive performance parametrically. 

Figure 12 is an example design plot generated retrospectively using the lunar terrain parameters 

recommended in the LRV RFP (Table 5), in conjunction with the wheel geometry (GM 1971) and 

empirically determined internal loss characteristics (Pavlics 1966). Here, the 25 climbing condition is 

used and mobility forces are shown for 20 percent wheel slip. As expected, the thrust is increased and 

motion resistance lowered with increased nominal deflection. The plot indicates that thrust equals motion 

resistance, and thus the vehicle should be capable of traversing the 25 slope if the wheel carcass deflects 
NASA/TM—2009-215798 8

3 cm nominally. Additional deflection would then provide a margin of safety to account for stochastic 

variation in terrain strength. On the other hand, additional deflection would amplify the nominal wire 

stresses and cause the bump-stop to engage more often. Considering these tradeoffs, GM DRL designed 

the wheel carcass to deflect about 4.5 cm under the nominal load. 

Early studies at GM DRL showed that tread spacing had a significant influence on the terrain failure 

pattern, and thus tractive performance (Fig. 7). The phenomenon was not well understood and so several 

wire mesh wheels with different tread spacing, and hence different total tread coverage (ranging from 0 to 

100 percent coverage), were built for comparative evaluation at the U.S. Army Waterways Experiment 

Station (WES) (Freitag 1972, Green 1971a,b/Melzer 1971). Wheel dynamometer testing was done on a 

lunar soil simulant (LSS), which emulated the mineralogy and particle distribution of lunar soil samples 

collected on the Apollo 11 and 12 missions. This simulant was prepared to low, medium, and high density 

terrain conditions (LSS1, LSS2, LSS3, respectively), and a low density condition with a small amount of 

water added (LSS4). These preparations covered the range of frictional and cohesive terrain strength 

specified by NASA in the RFP (Costes 1972). Based on a thorough analysis of single wheel drawbar pull 

and associated power consumption data, the wheel with 50 percent tread coverage was determined to be 

the optimum design. As an example, data from LSS1, the loosest terrain condition, is summarized in 

Table 6. The data shows that the 50 percent covered wheel consumes the minimum power at the self 

propelled point (without external resistance) and also has the highest drawbar pull capability at 20 percent 

slip. Note that the 20 percent slip condition was empirically determined to be the point where the wheel 

generated the maximum drawbar pull without excessive power consumption.

The slope climbing ability of the LRV was also determined on the basis of the single-wheel drawbar 

pull results, using an empirical equation that correlated these data with measured vehicle climbing 

performance (Freitag 1970/1972). Like in the drawbar pull evaluation, the 20 percent slip point was used 

as the maximum value in assessing gradeability. A curve fit of about 500 slope versus slip data points 

encompassing all terrain conditions (LSS1 through LSS4) was generated retrospectively and plotted in 

Figure 13. Data ranges corresponding to one, two, and three standard deviations from the mean slope 

climbing performance are also shown. The slip required to achieve the 25 slope climbing requirement for 

each range are summarized in Table 7. On average 59.5 percent slip is required; however, 72.0, 79.5, and 

84.5 percent slip are associated with one, two, and three standard deviations of the data, respectively. This 

implies that the wheel travel while traversing 0.5 km on a 25° slope could actually be up to 3.2 km, or so. 

GM DRL personnel performed a similar analysis of the data and were aware that the LRV would operate 

at high slip if a similar slope was encountered. They performed a thermal analysis and verified that the 

drive motors could sustain the required torque for the extra cycles needed. Additionally, the energy 

consumption associated with this traverse was calculated to be only a small fraction of the vehicle’s 

reserve. Thus, it was considered acceptable to operate the vehicle at high slip in order to meet the 

climbing requirement. A detailed review of the LRV performance on the Moon, including the postmission report by the Apollo 15 crew, is provided in (Costes 1972). Slopes of no more than 12 were 

encountered during the mission, and the crew indicated that tractive performance of the wire mesh wheels 

was excellent. 

3.0 Summary, Lessons Learned, and Suggestions for Future Work 

3.1 Summary 

Lunar wheel design poses a different challenge than terrestrial wheel design because of the unique 

environmental conditions and stringent mass/volume limitations. Each of the three wheel types used on 

the Moon were distinctly different, but appropriate for their respective missions. The development of the 

wire mesh wheel for the LRV was studied in detail to understand the most challenging factors and 

provide guidance for future designers. 

The basic wire mesh wheel technology was developed during the years 1963 to 1967. This wheel had 

a solid hub with a woven wire carcass, and a skeleton-like inner frame that prevented the carcass from 
NASA/TM—2009-215798 9

over deflecting. The carcass was partially covered by thin tread strips that enabled floatation over soft 

soil, and, in theory, developed propulsive force through generalized shear failure. All of the fundamental 

design features (e.g., mesh carcass, inner frame, tread strips, etc.) emerged as solutions to failures 

sustained while testing various prototypes. 

From 1966 to 1967 the wire mesh wheel was compared to other candidate designs with regard to a 

manned lunar mission scenario. For the given criteria, the wire mesh and the ‘hoop spring’ wheels were 

judged to be the most suitable designs and were further developed. The hoop spring wheel had a spoked 

hub and a one-piece metal rim supported by flexible metal hoops. Both wheel types were subjected to a 

design-test-redesign-retest program, in order to compare their performances and make improvements. 

This program included material, mechanical, and in-soil mobility tests. The improved wheel designs were 

then endurance tested under simulated lunar environmental conditions. 

The wire mesh wheel was determined to be most appropriate for the LRV mission because it offered 

superior stability, ride comfort, and longer life. Configuration and verification of the wheel to meet the 

LRV mission requirements was mostly done in 17 months, from October 1969 to March 1971. Since the 

procedure was not explicitly documented, the process was estimated with some assistance from former 

GM DRL employees. The most notable aspect was the selection of the wheel geometry and stiffness to 

climb a 25 slope on the Moon for 0.5 km. The Bekker method of terramechanical analysis, along with 

estimates of the lunar terrain strength properties, was used to relate the wheel’s ground contact geometry 

to its propulsive capacity. This method was used to select the nominal carcass deflection with regard to 

the climbing capability. Subsequently, the tread spacing was optimized using single wheel tests in lunar 

soil simulant. The test results indicated that the analysis overestimated the wheel’s performance, and that 

the wheel would need to slip significantly in order to generate enough traction to traverse the required 

slope; however, the power reserves were sufficient enough to allow this. 

3.2 Lessons Learned 

This article has revealed several lessons pertaining to lunar wheel design. 

Lesson 1: Lunar Wheel Designs are Mission Dependant 

The three wheel designs used on the Moon were entirely different and were developed specifically to 

meet their respective mission requirements. The rubber-pneumatic tire does not have the same utility on 

the Moon, because the material and air-spring properties change in that environment. Furthermore, the 

possibility of a ‘flat tire’ is not acceptable for a manned vehicle. A ‘flat tire’ would be a form of singlepoint failure and would immediately render the vehicle immobile. This would not only be costly to a 

mission, but could be very dangerous for astronauts if the puncture were to cause a tire explosion in zero 

atmospheric pressure. Various configurations of airless, metal wheels have been proposed (Fig. 8), which 

tend to trade-off performance and reliability. As such, it is important to clearly understand the application 

and associated requirements when selecting a lunar wheel concept. 

Lesson 2: Considerable Lead Time is Required to Develop a New Lunar Wheel Concept 

The development of a wheel that operates in the unique environment of the Moon could take most of 

a decade, as in the case of the LRV wheel. The majority of that time was spent updating the design 

concept through iterative building and testing. Once the basic design was established, it was then 

reconfigured for the LRV mission in a relatively short time. 

Lesson 3: Field Testing is Paramount to Understanding Lunar Wheel Performance 

From 1960 to 1967, prototype lunar wheels were built and tested by GM DRL for NASA mission 

feasibility studies (SLRV, MOLAB, MTA, and LSSM). All of the critical features in the final LRV wheel 

design (e.g., wire mesh carcass, inner frame, tread strips, etc.) emerged as solutions to failures observed 

while testing these prototypes. Because it is very difficult to simulate the complex interaction between a 
NASA/TM—2009-215798 10

wheel and its environment, field testing under realistic terrain conditions is essential to understanding the 

strengths and weaknesses of a design. 

Lesson 4: The Most Critical and Most Difficult Aspect of Lunar Wheel Design is the 

Flexible Carcass 

The lunar wheel carcass is critical, because its ground contact geometry and pressure distribution 

control the tractive performance of the vehicle. Results from a simple analysis using the Bekker method

are shown in Figure 12, which indicate that wheel deformation significantly benefits slope climbing 

ability. However, the range of temperatures on the Moon makes typical elastomeric materials unusable. 

The alternative is to create a metal mechanism (such as the wire mesh) that deforms and/or repositions 

under load. Such a mechanism must endure repeated cycling, persistent impacts, and be capable of 

withstanding sliding contact with unweathered regolith. The wire mesh structure served this purpose on 

the LRV wheel, but was the most formidable challenge in the design. 

3.3 Suggestions for Future Work 

The following recommendations are intended to help focus subsequent lunar wheel technology 

development. 

Recommendation 1: Establish the Wheel Requirements for New Missions 

Any technology development effort should start by establishing the wheel requirements associated 

with the target missions. This is very important, given the specificity of lunar wheel designs. The basic 

information needed is as follows: 

1. Level of redundancy 

2. Thermal and radiation exposure 

3. Number of wheel cycles 

4. Work requirements versus the terrain conditions 

5. Timeline for development 

With these data, lunar wheel concepts may be evaluated and compared to determine their applicability 

to each mission scenario. 

Recommendation 2: Benchmark Terramechanics Models for Lunar Wheel Evaluation 

The work that a wheel can perform is dependent on its interaction with the terrain. During the Apollo 

program, the Bekker method was used to predict the terramechanics of candidate designs. However, soil 

bin experiments performed at WES with the final LRV wheel showed that the Bekker method over 

predicted performance. This technology was very young at the time, and since then many advancements 

have been made. However, most modern terramechanics models are empirical and have not been 

evaluated for the lunar case. The main discrepancy is that lunar wheels apply relatively low ground 

pressure in 1/6th gravity. Modern methods in terramechanics should therefore be benchmarked against the 

data available from the WES soil bin experiments in order to determine their applicability. 

Recommendation 3: Develop Lunar-Specific Wheel-Terrain Testing Procedures 

Several different wheel performance and endurance tests were performed during the development 

process of the LRV wheel. Some tests, such as drawbar pull, provided in-situ performance information. 

Other tests, such as the treadmill obstacle endurance, enabled comparative evaluation of wheel concepts, but 

did not provide a reliable estimate of life, for example. The suite of lunar wheel tests should therefore be 

examined in order to understand their utility and relationship to performance on the Moon. Eventually, lunar 

wheel testing procedures should be established for both comparative evaluation and mission planning. 
NASA/TM—2009-215798 11

Recommendation 4: Determine the Limitations and Reconfigureability of the Wire Mesh Wheel 

Assuming wheel requirements and evaluation methods are established, the analysis of candidate lunar 

wheel types should proceed in order of technology readiness level (TRL). Clearly the wire-mesh LRV 

wheel should be examined first. Quite a few of the LRV wheel limitations are already known from past 

testing. For example, its slope climbing capabilities on lunar soil simulant has already been studied and is 

summarized by Figure 13. Additionally, the design has been qualified for a manned mission of up to 

120 km, with a maximum speed of 16 km/hr. The power requirements and pull capabilities of the LRV 

wheel have also been thoroughly characterized for a range of lunar terrain strength. Most of the remaining 

questions pertain to the extension of this design to alternative mission scenarios. Example in its current 

configuration, how much further than 120 km can the LRV wheel be used? How can the wire mesh 

design be scaled to different geometries and for various loads? How is the soft-soil performance affected 

by parametric changes? 

To establish its endurance limit, replicate LRV wheels should be made and tested. However, since it’s 

important to understand the scaling and performance relationships, a wheel-terrain model must also be 

developed. From the design point of view, the following two relationships would need to be simulated. 

(1) the carcass deformation, as a function of the wire diameter and number of wires; and (2) the terrain 

deformation pattern, as a function of the ground pressure distribution. With such a model, the wire-mesh 

carcass and tread pattern could be reconfigured for alternative load, geometry, or work requirements. If 

the LRV wheel design cannot be reconfigured to meet specific needs, then design modifications should be 

considered. 

Recommendation 5: Evaluate Other Wheel Designs in Order of TRL 

In the case that the wire mesh wheel concept does not cover the needs for future lunar exploration, 

then other high TRL designs should be examined. The Lunokhod and MET wheels are options, but 

according to the assessment by GM DRL, they would not be usable for manned missions, because of poor 

ride quality and lack of redundancy, respectively. New, as well as current, designs should be considered 

and evaluated. The results of the trade study at GM DRL (Fig. 8) should be used as a reference to 

determine which concepts to examine, with regard to the new criteria set forth. 

References 

Bekker M.G. Off-the-road Locomotion: Research and development in terramechanics. University of 

Michigan Press; March 1960. 

Bekker M.G. Land locomotion on the surface of planets, ARS Journal; 1962. 

Bekker M.G. Mechanics of locomotion and lunar surface vehicle concepts, Defense Research 

Laboratories at General Motors Corp., paper no. 632K. In: Automotive Engineering Congress; 

January 1963. 

Bekker M.G. Introduction to terrain-vehicle systems, The University of Michigan Press; 1969. 

Bekker M.G. The development of a Moon rover. Journal of the British Interplanetary Society, 38: 

537–543; 1985. 

Bendix. ALSS payloads (MOLAB), final report, volume III, Local Scientific Survey Module conceptual 

design, document no. BSR–1119; June 1965. 

Boeing. ALSS payloads (MOLAB), detailed technical report, mobility systems—vehicular, document no. 

D2–83203–1; June 1965. 

Coleman H.W., et al. Experimentation and Uncertainty Analysis for Engineers. John Wiley & Sons, Inc., 

pgs. 40–52; 1989. 

Costes, N.C. et al. Mobility performance of the Lunar Roving Vehicle: Terrestrial studies: Apollo 15 

results. NASA TR–R–401; 1972. 

Freitag D.R., et al. Performance evaluation of wheels for lunar vehicles. U.S. Army Waterways 

Experiment Station technical report no. M–70–2; 1970. 
NASA/TM—2009-215798 12

Freitag D.R., et al. Wheels for lunar vehicles, Journal of Terramechanics, 8(3): 89–105; 1972. 

Green A.J., et al. The performance of two Boeing-GM wheels (GM VII and GMVIII) for the manned 

lunar rover vehicle. U.S. Army Waterways Experiment Station miscellaneous paper no. M–71–3; 

1971 (a). 

Green A.J., et al. Performance of Boeing LRV wheels in a lunar soil simulant. Report I, Effect of wheel 

design and soil. U.S. Army Waterways Experiment Station technical report no. M–71–10; 1971 (b). 

GM. Lunar wheel and drive experimental test program, volume 1—summary technical report, NASA 

TR67–18; June 1967. 

GM. Design and manufacture of wheels for a dual-mode (manned—automatic) Lunar Surface Roving 

Vehicle. TR70–30 Vol. I; May 1970 (a). 

GM. LRV mobility subsystem, critical design review presentation; May 1970 (b). 

GM. LRV wheel assembly, technical drawings (#7552941, 7553028, 7553529, 7553521, 7552939, 

7552938, 7552940, 7553027, 7553199); 1971. 

Gromov V.V., et al. Lunokhod 2—A retrospective glance after 30 years. Presented at the EGS—AGS —

EUG Joint Assembly, held in Nice, France, April 6–11; 2003. 

Grumman. Design and fabrication of wheels for a lunar surface vehicle, final report. NASA CR102755; 

June 1970. 

Kemurdjian A.L., et al. Planetary rover as an object of the engineering design work. Proceedings of the 

IEEE International Conference on Robotics & Automation, Leuven, Belgium; May 1998. 

Lockheed. Design, fabrication and delivery of an improved single elastic loop mobility system, volume II, 

technical report; July 1972. Prepared for NASA under contract no. NAS8–27737. 

Mason, et al. Engineering Lunar Model Surface (ELMS), NASA TR–83–D; September 1964. 

Markow E.G. Predicted behavior of lunar vehicles with metalastic wheels. SAE paper no. 632J, presented 

at the Automotive Engineering Congress & Exposition; January 1963. 

Melzer K.J. Performance of Boeing LRV wheels in a lunar soil simulant. Report II, Effect of speed, wheel 

load and soil. U.S. Army Waterways Experiment Station technical report no. M–71–10; 1971. 

NASA. Apollo 14 press kit, release #71-3K; January 21, 1971. 

Northon F.E. Engineer design test of Mobility Test Article model GM–1. U.S. Army Test & Evaluation 

Command. NASA CR–102477; Nov 1967. 

Pavlics F. Locomotion energy requirements for lunar surface vehicles. Presented at the SAE Automotive 

Engineering Congress in Detroit, Michigan; January 1966. 

Pavlics F., et al. Interview with Ferenc Pavlics, Sam Romano, Don Freidman and Nick DiNapoli, Santa 

Barbara, CA; January 29, 2007 (a). 

Pavlics F., et al. Consultation session with Ferenc Pavlics and Sam Romano, Cleveland, OH; 

April 3–4, 2007 (b). 

Smith, Jr., D.W. Engineer design test of Mobility Test Article, 66, block I of NASA lunar surface 

vehicle studies (hard surface phase). U.S. Army Test & Evaluation Command. NASA CR–102513; 

Jan 1967 (revised April 1967). 

Vaughan Jr. O.H. Lunar Environment Design Criteria Models for Use in Lunar Surface Mobility Studies, 

NASA TM–X–53661; September 1967. 

Wong J.Y. Terramechanics and off-road vehicles, Elsevier; 1989. 

Wong J.Y. Theory of ground vehicles, third edition, John Wiley & Sons, Inc.; 2001. 

Young A. Lunar and Planeter Rovers: The Wheels of Apollo and the Quest for Mars, Praxis Publishing 

Ltd.; 2007. 

 
NASA/TM—2009-215798 13

TABLE 1.—OUTLINE OF WIRE MESH AND HOOP SPRING WHEEL DEVELOPMENT PROGRAM (GM 1967) 

Test articles Initial wheel designs Materials Improved wheel designs 

Test type Mobility Mechanical Screening Vacuum 

welding Mobility Mechanical Simulation 

Description 

 Drawbar-pull 

 Wheel 

towing 

 Steering 

resistance 

 Loaddeflection 

 Dynamic 

checkout 

 Single 

obstacle 

 Impact 

 Endurance 

 Tensile 

 Fatigue 

 Spring 

element 

cycling 

 Drawbar-pull 

 -Wheel 

towing 

 Loaddeflection 

 Dynamic 

Checkout 

 Single 

Obstacle 

 Impact 

 Endurance 

Thermalvacuum 

Performance 

Evaluation 

TABLE 2.—WHEEL REQUIREMENTS TO MEET THE 

LSSM MISSION ARCHITECTURE (GM 1967) 

Wheel size 

Diameter 101.6 cm 

Width 25.4 cm 

Wheel load 

Nominal radial 445 N 

Limit radial 5338 N 

Limit lateral 890 N 

Life 100,000 rev 

TABLE 3.—SUMMARY OF DYNAMOMETER TESTING (GM 1967) 

Wheel Test mode Cycles 

HOOP-4 Checkout and calibration 5,610 

Dynamic ambient 26,345 

Dynamic thermal-vacuum 24,504 

Total 56,459 

MESH-4 Checkout and calibration 1,279 

Steady state ambient 29,685 

Steady state thermal-vacuum 7,825 

Dynamic thermal-vacuum 55,376 

Total 94,165 
TABLE 4.—LRV WHEEL CONFIGURATION PROCESS OUTLINE, CREATED RETROSPECTIVELY USING INFORMATION FROM 

(GM 1970a/b, GM 1971, Pavlics 2007a/b) 

LRV requirements Wheel requirements Configuration specifications 

Mass 

 181 kg mass budget  64.4 kg allocated for the mobility 

subsystem 

 5.62 kg allocated for each wheel 

 5.48 kg per wheel 

o ~1.75 kg inner frame 

o ~0.953 kg wheel rim and disc and hub 

o ~0.200 kg hardware 

o ~2.58 kg outer frame 

Size 

 44 configuration 

 Stowed in wedge shaped LM bay 

175193102 cm 

 Cross 70 cm wide crevasse 

 Climb 30 cm height step 

 Largest wheels possible, while 

fitting into the LM bay 

 81.3 cm diameter  22.9 cm wide  Carcass depressed down to inner frame during transport 

Operational 

forces 

 Total mass of vehicle + payload ~621 kg  Maximum speed of 16 km/hr over lunar 

maria 

 254 N nominal load 

 600 to 700 N impact load  2669 N critical impact load 

 Bump-stop engagement at 600 N radial load, 8.26 cm 

deflection 

 4000 N ultimate load, carried by bump-stop  Safety factor of 1.5 

Life 

 120 km range 

 No single point failure to abort the mission  No secondary failure to endanger the crew 

 Infinite life at nominal carcass 

deflection 

 75, 000 rev fatigue life  Wheel operates with up to 10 

percent wire breakage 

 Inner frame can be used as a runflat device 

 800 strands of 0.838 mm, zinc coated piano wire  64.8 cm diameter inner frame to prevent overstressing 

wires, and for run-flat 

Terra-mechanics 

 Fully loaded, climb 25° slope for 0.5 km 

 Minimize energy consumption, to lower 

battery mass 

 Ground pressure of 4.14 kPa under 

nominal load 

 Optimize tread spacing to maximize 

gradeability 

 4.450.635 cm radial deflection 

 50 percent coverage with tread strips 

NASA/TM—2009-215798 14
NASA/TM—2009-215798 15

TABLE 5.—RECOMMENDED TERRAIN PARAMETERS 

FROM THE LRV RFP (Costes 1972) 

Cohesion cb = 0 to 0.035 N/cm2

Internal friction angle φb = 354° 

Slip coefficient K = 1.780.76 cm 

Exponent of deformation n = 1 (dimensionless) 

Cohesive modulus of deformation kc = 0 to 0.28 N/cmn+1

Frictional modulus of deformation kφ = 0.82 N/cmn+2

TABLE 6.—VISUALLY ESTIMATED AVERAGE WHEEL PERFORMANCE DATA ORIGINALLY 

USED TO SELECT THE LRV WHEEL TREAD COVERAGE (Freitag 1972). TERRAIN CONDITION 

LSS1 IS SHOWN, BUT DATA FOR ALL TERRAIN CONDITIONS ARE REPORTED IN (Green 1971b) 

Terrain Wheel coverage No. tests Power no.a

 Pull coeff.b

 (at zero pull) (at 20 percent slip) 

 

LSS1 None 4 0.12 0.22 

50 percent with chevron tread-strips 6 0.08 0.33 

75 percent with chevron tread-strips 4 0.19 0.21 

100 percent with rubber 2 0.18 0.02 

100 percent with rubber and aggressive grousers 4 0.18 0.11 

 

a

Power number is defined as the energy consumed per unit of distance, per unit of weight b

Pull coefficient is defined as the drawbar pull normalized to the weight 

TABLE 7.—STATISTICAL SUMMARY OF THE EXPERIMENTAL WHEEL SLIP (PERCENT) 

REQUIRED TO CLIMB A 25 SLOPE ON LSS1—LSS4. 

[This information was extracted from the data shown in Figure 13.] 

Average case 

percent 

Average σa

percent 

Average 2σa

percent 

Average 3σa 

percent 

59.5 72.0 79.5 84.5 a

σ (sigma) refers to the standard deviation of the wheel performance data for slip versus slope-climbing 

capability. 
Vehicle: 

Missions: 

LunokhodLuna 17, Nov 1970 Luna 21, Jan 1973 

MET Apollo 14, Feb 1971 

LRVApollo 15, July 1971 Apollo 16, April 1972 Apollo 17, Dec 1972 

Control: Teleoperated Towed by astronauts Onboard joystick Max speed: 2 km/hr ~4 km/hr 16 km/hr Loaded mass: ~800 kg ~75 kg ~700 kg Configuration: 8 traction wheels 2 free wheels 4 traction wheels Max distance: 37 km ~3 km 36 km 

Figure 1(a).—Vehicles used on the lunar surface. 

NASA/TM—2009-215798 16
Vehicle: Lunokhod MET LRV 

Mass: 2.7 kg 1.86 kg 5.48 kg Diameter: 51.0 cm 40.6 cm 81.8 cm Width: 20.0 cm 10.2 cm 22.9 cm Deflection: none ~2.54 cm ~4.45 cm Load path: Rigid, wire carcass 

connected by spokes 

Rubber carcass supported by nitrogen filled innertube (10.3 kPa)

Flexible, wire mesh carcass and stiff inner frame 

Tread: 2.0 cm high, negligible 

coverage 

None 0.279 mm high, 50 percent 

coverage 

References: (Gromov 2003) 

(Kemurdjian 1998) Photo by Serguei Matrossov 

(NASA 1971) Photo courtesy of Dave Glemming 

(GM 1970b) (GM 1971) 

Figure 1(b).—Wheels used on lunar vehicle.

NASA/TM—2009-215798 17
NASA/TM—2009-215798 18

Figure 2.—Prototype wheels made by GM, DRL, and Goodyear for SLRV. Courtesy of 

Dave Glemming. 

(a) Wire frame wheel (b) With traction pads 

(c) With partial mesh cover (d) With full fabric cover 
NASA/TM—2009-215798 19

Figure 3.—Prototype wheel developed for MOLAB by GM, DRL, 

and Goodyear. Courtesy of Dave Glemming. 

Figure 4.—Cartoon showing wire mesh carcass manufacturing processes. Courtesy of Don Freidman. 
NASA/TM—2009-215798 20

Figure 5.—Prototype wire mesh wheel by GM DRL. 

Figure 6.—Various small scale lunar vehicles with articulated frames and unconventional 

running gear (Bekker 1962, Bekker 1963). The vehicle on the left has high width to 

diameter wheel ratio, the middle vehicle uses screw propulsion, and the right vehicle 

has spaced link tracks. Courtesy of Don Freidman. 

 
NASA/TM—2009-215798 21

Figure 7.—Extended exposure photograph showing the action of soil underneath adjacent and spaced cleats. 

Local failure occurred along surface a to b and general failure occurred along surface b to c. Original work 

performed by Dr. M.G. Bekker (Bekker 1960). Courtesy of Ferenc Pavlics. 

1 2

a b

c
Key : C = Calculation, E = Experiment, J = Engineering judgment 

Figure 8.—Wheel concept matrix. 

[After Dr. M.G. Bekker (Bekker 1985). High scores are shown in red.] 

NASA/TM—2009-215798 22
NASA/TM—2009-215798 23

 MESH-1 HOOP-1 

Figure 9.—Initial 101.6 cm diameter wire mesh (left side) and hoop spring (right side) wheels (GM 1967). 

Figure 10.—Wheel dynamometer for mission simulation inside of a thermalvacuum chamber (GM 1967). 
NASA/TM—2009-215798 24

Figure 11.—Final LRV wheel. 

Figure 12.—Calculated LRV mobility forces at 20 percent slip on a 25 slope. Mobility is 

achieved when thrust exceeds motion resistance (terrain resistance + internal loss + 

gravitational resistance). 
NASA/TM—2009-215798 25

Figure 13.—LRV climbing performance in loose, air-dry lunar soil simulant (LSS1, LSS2, LSS3, and 

LSS4). Climbing performance was predicted based on single-wheel tests using the correlation 

method proposed by Freitag (Freitag 1970/1972). The mean trend was generated by curve-fitting 

the first and second pass data (simulating front and rear tires) separately using 3rd degree 

polynomials, then taking the average of the two curves. The upper and lower ranges are 

represented as various multiples of the standard deviation (sigma), which was determined using 

General Uncertainty Analysis (Coleman 1989). 

-30

-20

-10

0

10

20

30

40

50

-20 0 20 40 60 80 100

Slip, %

Slope, deg

Average

1 sigma

2 sigma

3 sigma

3 sigma extrapolation

25 deg slope 

59.5% slip 

for average 

72.0% slip 

for 1 sigma

79.5% slip 

for 2 sigma

84.5% slip for 

3 sigma 

(extrapolated)
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The Development of Wheels for the Lunar Roving Vehicle 

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Asnani, Vivake; Delap, Damon; Creager, Colin 

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WBS 140765.04.02.01.02.03 

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John H. Glenn Research Center at Lewis Field 

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13. SUPPLEMENTARY NOTES

14. ABSTRACT

The Lunar Roving Vehicle (LRV) was developed for NASA’s Apollo program so astronauts could cover a greater range on the lunar 

surface, carry more science instruments, and return more soil and rock samples than by foot. Because of the unique lunar environment, the 

creation of flexible wheels was the most challenging and time consuming aspect of the LRV development. Wheels developed for previous 

lunar systems were not sufficient for use with this manned vehicle; therefore, several new designs were created and tested. Based on criteria 

set by NASA, the choices were narrowed down to two: the wire mesh wheel developed by General Motors (GM), and the hoop spring wheel 

developed by the Bendix Corporation. Each of these underwent intensive mechanical, material, and terramechanical analyses, and in the 

end, the wire mesh wheel was chosen for the LRV. Though the wire mesh wheel was determined to be the best choice for its particular 

application, it may be insufficient towards achieving the objectives of future lunar missions that could require higher tractive capability, 

increased weight capacity, or extended life. Therefore lessons learned from the original LRV wheel development and suggestions for future 

Moon wheel projects are offered. 

15. SUBJECT TERMS

Lunar roving vehicles; Wheels; Moon; Lunar exploration; Lunar surface; Manned lunar surface vehicles; General Motors 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

 ABSTRACT

UU 

18. NUMBER

 OF 

 PAGES

31 

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email:help@sti.nasa.gov) 

a. REPORT

U 

b. ABSTRACT

U 

c. THIS 

PAGE

U 

19b. TELEPHONE NUMBER (include area code)

443-757-5802 

Standard Form 298 (Rev. 8-98)

Prescribed by ANSI Std. Z39-18