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Space Robotics

US Army Engineer Waterways Experiment Station

This is a historical facility. Waterways Experiment Station was a named Army organization from 1 March 1937 to 30 September 1999, when the Corps of Engineers consolidated seven of its laboratories into the Engineer Research and Development Center [8]. The Vicksburg site and its soils work continued: vehicle mobility and terramechanics are run there today by the Mobility Systems Branch of the ERDC Geotechnical and Structures Laboratory, which is the organizational descendant of the Mobility and Environmental Division and still names the Lunar Roving Vehicle among the work its site supported [9]. What did not survive is the specific arrangement described below: the single-wheel dynamometer, the prepared soil bins and the four shear apparatus of the lunar wheel campaigns are documented only in reports from 1968 to 1978, and nothing published establishes that any of that hardware still stands. Contact ERDC for current capability. The parameters below are the conditions the Apollo-era results were measured under.

The Waterways Experiment Station at Vicksburg had already built the method the lunar program would use before the program existed: a 1965 synthesis of the published wheel-on-soft-soil literature indexed tire performance to cone penetration resistance rather than to fitted soil constants, and found that tread pattern and lug shape mattered little on frictional soil, a result the lunar wheel screening later reproduced [10]. It is the laboratory where the Apollo lunar wheel was chosen. Under NASA sponsorship its Mobility and Environmental Division ran the five candidate wheels of the Lunar Roving Vehicle program on one single-wheel dynamometer in one prepared sand, then swept the selected Boeing/GM wire-mesh wheel over speed, load and soil strength in a crushed basalt simulant [1][2][3]. The drawbar pull against slip method that NASA GRC’s SLOPE laboratory still publishes as a procedure descends from the mobility work done here [6].

Its second output is less well known and more transferable: the division characterized its own soils by four independent shear apparatus at once, and published the disagreement between them [2]. That is the reason a friction angle quoted for a simulant is a property of the apparatus as much as of the soil.

Everything below is the historical record from the test reports themselves. No published source describes a user program, a fee schedule or a lead time under either name, and the test reports all predate the 1999 reorganization [8].

Laboratory data

Section titled “Laboratory data”
ParameterValue
OperatorUS Army Corps of Engineers, Mobility and Environmental Division [1][2]
LocationVicksburg, Mississippi, United States [4]
CommissionedNot published. Lunar wheel reports span 1968 to 1971 [1][2][4]
TypeTerramechanics laboratory: soil bins, single-wheel dynamometer, test vehicles
Floor areaNot published
CapabilitiesDynamometer, soil bins, vehicles
Simulant or terrainYuma sand at five consistencies; crushed Napa basalt at five consistencies [1][2][3]
InstrumentationDynamometer carriage with independent wheel drive; WES cone penetrometer
Ground truthSoil characterized before every traffic run; 170 penetrometer tests behind one condition
Fidelity limits1 g, in air, on moist terrestrial soil. No vacuum and no offload [1][2][3]
AccessNot published. The lunar program was contract work, not an open user program
Cited byApollo LRV, lunar environment

Capabilities

Section titled “Capabilities”

Single-wheel dynamometer

Section titled “Single-wheel dynamometer”
ParameterValue
Working volumePrepared soil bin traversed by a carriage; bin dimensions not published
Test article limitsWheels 47.75 to 107.95 cm diameter run to date; loads 67 to 667 N
VacuumNone. Tests were run in air at ambient pressure [1][2][3]
TemperatureNot controlled and not reported
IlluminationNot applicable
Simulant or terrainYuma sand or crushed Napa basalt, prepared to a target consistency
SlopeNot applicable. Slope capability is inferred from level-ground pull data
Gravity offloadNone. Wheel load is commanded instead
InstrumentationPull, torque, sinkage and slip; contact-length sensor in the wheel surface [4]

The rig drives carriage and wheel independently, so slip is programmed rather than observed. Freitag’s comparative program used five discrete wheel loads, 67, 133, 311, 489 and 667 N, at about 0.5 m/s translational speed, and read performance at 20 and 60 percent slip [1]. The later Boeing/GM program held a single 254 N wheel load, ran the full programmed slip sweep to 100 percent, and read performance at 20 and 50 percent slip because torque and pull rise only slowly above 20 percent [2]. Both constant-slip and programmed-slip modes were used, in classical, ramped and modified variants [3].

Wheel diameters run in the candidate screening were 101.60 cm for the Bendix I petal elastic wheel, 102.87 cm for the Boeing/GM I wire mesh, 107.95 cm for the Grumman I, 97.4 cm for the pneumatic reference wheel and 47.75 cm for the Surveyor Lunar Roving Vehicle wheel, all at 25.4 cm contact width except the SLRV [1]. The six Boeing/GM development wheels GM IX to GM XIV measured 77.3 to 82.2 cm unloaded, and the GM X baseline with 50 percent chevron cover sat at 6.3 kPa contact pressure at 254 N on an 11.00 by 6.85 in tire print [2].

For the rigid-wheel stress work the bench carried a 71 cm smooth rigid wheel in two widths, 7.6 and 30.5 cm, at loads from 178 to 7108 N and constant slips of 3, 14 and 33 percent, with contact length measured directly by a sensor in the wheel surface rather than inferred [4].

Prepared soil bins

Section titled “Prepared soil bins”
ParameterValue
Working volumeNot published
Test article limitsSingle wheels and 4x4 and 6x6 vehicles on matched soil preparations
Simulant or terrainAir-dry Yuma sand, and crushed Napa basalt from Basalt Rock Company [1][2]
InstrumentationWES cone penetrometer reporting cone index gradient G
Ground truthDensity, cone index gradient, cohesion and friction angle before traffic [1][2]

Soil is prepared to a target consistency and characterized before it is driven on, and the characterization is what makes the results reusable. The measured conditions:

ConditionMaterialCone index gradientDry densityRelative densityStrength
S1air-dry Yuma sand, loose0.54 MN/m3, average of 170 tests1.484 g/cm3, average of 7539 pctzero cohesion
S2 [1]Yuma sand, denseNot published1.62 g/cm387 pct43.5 deg, zero cohesion
C3 [1]Yuma sand, 1.8 pct moistureNot published1.51 g/cm348 pct38.1 deg, cohesion 1.75 kN/m2
LSS1 [2]crushed basalt, 0.9 pct moisture0.22 MN/m3 (0.8 pci)1.518 g/cm331 pctsee below
LSS3 [2]crushed basalt, 0.9 pct moisture6.5 pci1.655 g/cm352 pct40.0 deg by triaxial
LSS4 [3]crushed basalt, 1.8 to 1.9 pct moisture0.22 MN/m3Not publishedabout 30 pctcohesion 0 to 2.9 kN/m2
LSS5 [3]crushed basalt, firm6.39 MN/m3Not publishedabout 60 pctcohesion 2.9 kN/m2

The S1 range across those 170 penetrometer tests was 0.48 to 0.81 MN/m3 and the S1 density range across 75 gravimetric tests 1.446 to 1.527 g/cm3, so the spread of a nominally single condition is about a factor of 1.7 in strength [1]. Relative density is itself uncertain: for the basalt simulant the value derived from the cone index gradient and the value from the density box disagree badly, 32 against 17 percent for LSS4 and 31 against 54 percent for LSS1, and the report prefers the gradient-derived figure because volumetric readings were erratic in loose soil [2].

Every cohesion figure in the table is apparent cohesion produced by moisture and interlock at 0.5 to 1.9 percent water content [1][2][3]. It has no lunar counterpart, and the sources say so [1][2][3].

Test vehicles

Section titled “Test vehicles”
ParameterValue
Working volumePrepared soil lanes and constructed slopes; dimensions not published
Test article limits4x4 and 6x6 test vehicles, built light so wheel loads match lunar weight
SlopeSlope-climbing runs performed; maximum constructed angle not published
Gravity offloadNone. Vehicle mass was reduced instead of offloaded
InstrumentationDrawbar pull through a hitch; axle scales for load transfer [6]

The division ran vehicle-level pull-slip and slope-climbing tests alongside the single-wheel work, on soil prepared to matching consistency, which is what allowed the single-wheel to vehicle transfer to be checked rather than assumed [1]. Hitch geometry was measured rather than ignored: on the WES 4x4 test vehicle with the hitch at one seventh of the wheelbase, applied drawbar pull transferred about 9 percent of the pull force from the front axle to the rear, load transfer being pull force times twice the ratio of hitch height to wheelbase when the center of gravity sits between the axles [6].

Soil strength apparatus

Section titled “Soil strength apparatus”
ParameterValue
Working volumeBench and in-situ instruments used inside the soil bins
Test article limitsSoil specimens; sample sizes 1 to 4 tests per apparatus per condition [2]
InstrumentationVacuum triaxial, in-situ plate shear, bevameter plate and ring shear, Cohron sheargraph, trenching

The bevameter supplies the Bekker pressure-sinkage parameters and the ring shear supplies the Coulomb parameters, both fitted rather than measured directly. On crushed basalt the frictional modulus of sinkage k-phi came out at 4.32 lb/in^(2+n) for LSS1 over four tests with individual fits 3.50 to 5.25, and 8.83 for LSS3 over three tests, with sinkage exponent n of 0.90, 1.15, 1.48 and 1.18 across the four conditions, not monotonic in density [2].

What it does not reproduce

Section titled “What it does not reproduce”

Gravity. Every result is 1 g. The workaround used here, and still used at every terramechanics bench since, was to build the test vehicles light enough that wheel loads matched lunar weight [1]. That reproduces the contact load and leaves the gravitational body force in the soil column at its terrestrial value.

Vacuum, and therefore lunar cohesion. The soils are terrestrial, in air, at 0.5 to 1.9 percent moisture [1]. Freitag’s headline negative result, that adding cohesion did not markedly improve wheel performance, is a result about moist sand, not necessarily about regolith, because the cohesion was imposed by water rather than by the interparticle and electrostatic mechanisms that produce it on the Moon [1]. Melzer’s report goes further and flags unquantified air-pore pressure as a possible artifact of testing in air: the one sand against simulant comparison showed a speed effect on sand that did not appear in the simulant, and the authors recommended vacuum scale-model tests to settle it, which were not run [3].

Agreement between its own instruments. Four apparatus on one soil in one campaign gave friction angles spanning 19 degrees and apparent cohesions spanning a factor of ten [2]. The numbers and the reasoning are on the regolith simulants page; what belongs here is that the disagreement is a property of this laboratory’s method set and not of the sample [2].

A physically meaningful cohesive modulus of sinkage. The Bekker parameter k-c fitted negative on all three LSS3 plate penetration tests, range -2.44 to -0.94 lb/in^(1+n), and on some LSS1 tests, range -0.76 to +1.28 [2]. A negative cohesive modulus has no physical meaning, and this is the measured counterpart to the analytical objection raised from inside the same program, that k-c, k-phi, n and the shear modulus K are curve fits to a particular plate or shear ring rather than soil properties [4].

Statistical weight. Slope-climb figures are single-vehicle observations, not qualification runs, and the 1 to 2 degree penalty for steering while climbing is stated by the authors as an estimate from observation rather than a measured sweep [1]. LSS2 and LSS4 rest on a single bevameter test each [2].

Grouser geometry. The angle-iron grousers that produced the largest pull gains measured here are given a height and a width but never a count or a circumferential spacing, in either report, so the gain cannot be placed on a grouser spacing curve [1][2].

Place in the wider method

Section titled “Place in the wider method”

The Vicksburg work sits between two bodies of literature. Upstream is the stress-distribution theory of rigid wheels on soil, which located the point on a towed wheel where tangential stress reverses and tied it to the junction of the two soil failure zones, and whose authors said it needed more experimental support [11]. Alongside it ran the geotechnical characterization of the lunar surface: a Berkeley simulant matched to Surveyor-derived friction angle, cohesion and density, whose properties were all strong functions of placement density [14], and a penetration-resistance extrapolation to lunar gravity through a bearing-capacity equation [15]. Both are terrestrial simulants with lunar values inferred, not measured [14][15].

Other Apollo-era programs covered what a bench in air at terrestrial gravity could not [12][13]. MSFC ran cone penetration tests on Napa basalt simulant and Yuma sand at one-sixth, 1 and 2 g aboard a KC-135, and found cone resistance linear in the gravity ratio [13]. A full-scale wire-mesh wheel and fender were flown in a vacuum chamber on a C-135A at one-sixth g for the dust profile program, which found the original fender inadequate; its quantitative instrumentation failed, so the result is film interpretation [20]. Design-side documents framed the requirements the wheel tests served: the traction drive sizing study was analysis and vendor survey, not measurement [18], and the contractor developmental test plan for the earlier dual-mode vehicle wheels is a plan with no results [19]. The prediction program for Apollo 15 combined WES wheel tests, 1/6 g aircraft wheel tests and a Bekker-type vehicle model, and was checked against console readouts, with a median deviation of 30 percent; no direct measurement of slip, drawbar pull or sinkage exists from the Moon [12]. The Apollo soil mechanics experiment then supplied the lunar soil model that the simulant work was meant to approximate, with bulk density increasing logarithmically with depth [16][17].

Later work asked the same questions with different tools, in four families.

Reduced-gravity testing. Parabolic flight provides the gravity this laboratory lacked, in short parabolic windows. Single-wheel drawbar tests on FJS-1 simulant and Toyoura sand compared gravity levels from one-sixth to 2 g against equivalent wheel-load variation at 1 g [21]. A Concordia apparatus added rapid pneumatic soil preparation, validated by cone penetrometer, which addresses the repeatability problem the S1 spread above illustrates [28]. A thesis on two Falcon 20 campaigns concluded that reduced-weight testing, which matches only wheel load as the WES vehicles did, overstates mobility [29]. These are laboratory and aircraft results, not flight on another body.

Soil bins with metrology. The DLR facility pairs a 5.5 by 10 by 0.5 m bin with camera-based elevation mapping and optical tracking; its identified cohesive modulus came out negative for all three soils, the same pathology the WES reports show [22][2]. The NASA Glenn procedure for full-vehicle drawbar pull and the SLOPE laboratory results descend from the WES method [6][27]. An inching gait there reached 0.37 normalized drawbar pull against 0.28 for rolling compliant tires, a 32 percent gain [27].

Analytical and semi-empirical models. A steering model added an explicit side-force term, validated on FJS-1 at 1 g with parameters assumed independent of gravity [23]. A slip-sinkage formula was checked against decades-old published shear-plate and tractor data [24]. A dynamic model added an oscillation term for grouser effects, tuned to one test case in a single sand [31]. JPL’s ROAMS contact model was compared with MER slope-slip data on terrain whose properties were not characterized [30]. A NASA survey compares semi-empirical, numerical and empirical approaches and states its comparison is not an accuracy ranking [26].

Numerical and learned models. A two-dimensional discrete element model selected lug geometry for a lunar micro rover on a JAXA sloped bed [25]. A parallel-particles variant was validated against parabolic flight and did not reach quantitative agreement [32]. A neural network surrogate of the Soil Contact Model is differentiable for predictive control, but its ground truth is model output, not soil [33]. None of these has flown as a design tool with a published on-surface validation of the kind the LRV supplied only indirectly [12].

Work since 2015 on the same questions

Section titled “Work since 2015 on the same questions”

None of the families below has flown a wheel designed with it on the Moon; each is a ground, aircraft or simulation result, and the page says which.

Test practice. NASA’s current consolidation of mobility test practice, written around the Lunar Terrain Vehicle, sets out full-vehicle and single-wheel drawbar pull, slope and endurance methods and lessons from the VIPER and Apollo LRV campaigns [40]. It is a set of recommendations with sample plots and no new measurements, and it lists missing standards for lunar simulants [40]. Automated single-wheel testing is the DLR TROLL robot, which loosens, levels and compacts the soil bed before each run, so preparation spread of the kind the S1 condition shows is controlled by procedure [37]. A rover-level counterpart is the Lunar Rover Optimization Platform, a 20.4 kg four-wheeled testbed for sweeping wheel geometry and load, whose prove-out results are scored pass or fail by observation [43]. JPL’s Scarecrow campaign on Curiosity wheels found rimmed configurations cost almost nothing in slip on 18 degree slopes, with sand results highly variable [44].

Gravity and the mass-reduction workaround. The WES vehicles matched lunar wheel load by building light [1]. A physics-based simulation validated on SLOPE data argues that this makes the terrain too strong, giving overoptimistic trafficability: a 30 degree climb at about 42 percent slip for a 73 kg rover on Earth becomes about 85 percent slip for the 440 kg VIPER on the Moon [45][46]. These lunar numbers are model output; every validating measurement is at 1 g [45][46]. Parabolic-flight tests compared cone penetrometer response and single-wheel drawbar pull of GRC-1 in one-sixth g and 1 g, at one density in reduced gravity [41]. A magnetic levitation rig held steady one-sixth g for static cone penetration in a magnetite-bearing simulant, not lunar composition [39]. A Shear and Compression Cell built for drop towers reports only 1 g example curves [42]. A reduced-gravity single-wheel rig with an annular rotating soil trench was designed for aircraft use and reports no wheel-soil data [36]. The DLR and CNES MMX rover plans the first wheeled driving in milli-gravity, about 1/2000 of Earth, with pre-flight expectations only [38].

Wheel-terrain models and simulation. A grouser-aware model for the UAE Rashid rover missed its single-wheel rig measurements with measured soil parameters (10.2 N measured drawbar pull against 6.2 N simulated), so its agreement comes from calibration [34]. Granular resistive force theory and a continuum material point method were benchmarked against a Bekker-type model for rigid wheels in three media, as alternatives to classical terramechanics [35]. A discrete element model calibrated only on angle of repose reproduced Rashid-1 style wheel traction in Toyoura sand and FJS-1, and predicts traction coefficient essentially unchanged at lunar load, with no reduced-gravity experiment [47]. A rover simulator added deformable terrain from offline discrete element wheel runs, as an appearance model rather than a terramechanics model [48]. A thermal model of Lunar Terrain Vehicle wheels at the south pole has no thermal measurement behind it [49].

Campaigns run there

Section titled “Campaigns run there”

Lunar wheel down-select, reported 1970. Five candidate wheels on one dynamometer in one soil, at 220 N wheel load in loose air-dry sand [1]:

WheelDiameterPull coefficient at 20 pct slip, S1Max climbable slopeSpecific energy
Bendix I, petal elastic101.60 cm0.45228 to 30 deg4 W-h/km
Boeing/GM I, wire mesh102.87 cm0.27415 to 20 deg6 W-h/km
Grumman I107.95 cm0.28115 to 20 deg10 W-h/km
SLRV47.75 cm0.426Not reportedNot reported
Pneumatic reference97.4 cm0.448Not reportedNot reported

None of the original wheels could be relied on to climb the 35 degree slope the program asked for [1]. Adding cohesion helped less than expected: the Bendix wheel went from 0.452 in zero-cohesion S1 to 0.505 in C2 at 1.08 kN/m2 cohesion, and the Boeing/GM wheel from 0.274 to 0.343. Adding grousers helped much more: 3.2 cm angle-iron grousers took the Grumman wheel from 0.580 to 1.010 pull coefficient at 60 percent slip at 310 N in S1, a 74 percent gain, at a cost in power [1].

Two findings from that campaign generalize past the LRV. Below about 220 N wheel load the pull coefficient stops depending on load, and over 0.7 to 3.5 kN/m2 it stops depending on average contact pressure, both in fine sand [1]. A lightly loaded wheel therefore operates in a regime where the classical pressure-sinkage terms do not order the result. And level-ground pull data predicted vehicle slope-climbing ability conservatively by 1 to 2 degrees, with a further 1 to 2 degrees lost to steering while climbing [1].

Boeing LRV wheel design and soil, reported 1971. Six wire-mesh configurations differing in chevron tread cover from 0 to 100 percent and in rim stiffness, at a fixed 254 N wheel load in four simulant consistencies [2]. For the 50 percent chevron wheel that flew, power number relates to pull coefficient exponentially, and the slope of the initial linear portion fell from 1.478 at G = 0.8 pci to 1.314 at G = 6.5 pci: the cost of pull drops as the soil firms [2]. This report is also the source of the soil table above.

Boeing LRV wheel speed and load sweep, reported 1971. Fifty-seven single-wheel tests on the flight-configuration wheel established that pull coefficient, power number and efficiency are insensitive to wheel speed from 0.44 to 3.14 m/s, to wheel acceleration, to the presence of a fender, to travel direction and to wheel load from 178 to 377 N. Only sinkage varied with load [3]. Soil strength is the variable that matters: pull coefficient at 20 percent slip rose 50 percent as G went from 0.22 to 6.39 MN/m3. The slope limits used in Apollo mission planning come from here, 19 +/- 6 degrees in the nominal soil condition and 23 +/- 5 degrees in the firm one, at torque coefficients at maximum efficiency of 0.35 +/- 0.11 and 0.32 +/- 0.10 [3].

Tractor dozer field trials for the Bureau of Mines, reported 1978. Six tractor and blade combinations reclaiming coal-mine spoil banks, measured for blade capacity, production rate, cone index and drawbar pull against slip [7]. Maximum drawbar pull coefficients were 0.88 for a Caterpillar D8H and 0.86 for a D9H, both in first gear at about 20 percent track slip on spoil with a 0 to 6 in cone index above 200 [7]. Measured earthmoving production reached 49.0 to 70.6 percent of the traction-optimum production at the measured speed, averaging 55.9 percent, and every blade tested operated below 67 percent of its measured maximum capacity. The material is wet terrestrial spoil at a cone index where soil strength stops mattering, so nothing in it constrains behavior in weak regolith, but the roughly half-of-optimum gap is the number an excavation sizing argument from blade force alone leaves out.

Retrospective re-analysis, 2009. A curve fit over about 500 slope against slip points drawn from this laboratory’s archived data puts the mean slip required for the LRV wire-mesh wheel to climb its 25 degree requirement slope at 59.5 percent, rising to 72.0, 79.5 and 84.5 percent at one, two and three standard deviations, and identifies 50 percent tread coverage as the optimum from the comparative dynamometer runs, minimum power at the self-propelled point and highest drawbar pull at 20 percent slip in LSS1 [5]. Both figures are analyses performed in 2009 by authors working from the archive, not period results, and the 59.5 percent slip figure is the one that shows the Bekker-method design analysis overpredicted the wheel [5].

What is not established

Section titled “What is not established”

No source in the corpus gives the dimensions of the WES soil bins, the commissioning date of the dynamometer, or whether any of the 1968 to 1978 hardware survives [8][9]. No lunar measurement of LRV slip, drawbar pull or sinkage exists to confirm the pre-flight predictions [12]. Whether the cohesion imposed by moisture in these tests bounds regolith behavior is unresolved, and the vacuum scale-model tests recommended in 1971 were not run [3]. The reduced-gravity and numerical work above has been validated against 20 to 40 second transients and laboratory soils, not against surface operations [21][29][32].

References

  1. Freitag, D. R., Green, A. J. and Melzer, K.-J. (1970). Performance Evaluation of Wheels for Lunar Vehicles (Summary Report) . U.S. Army Engineer Waterways Experiment Station, Technical Report M-70-2. Source
    BibTeX
    @techreport{freitag1970performance,
  title = {Performance Evaluation of Wheels for Lunar Vehicles (Summary Report)},
  author = {Freitag, Dean R. and Green, Andrew J. and Melzer, Klaus-Jurgen},
  number = {Technical Report M-70-2},
  institution = {U.S. Army Engineer Waterways Experiment Station},
  year = {1970},
  url = {https://ntrs.nasa.gov/citations/19700027358},
  abstract = {Performance evaluation of lunar surface vehicle wheels in fine sand}
}
  2. Green, A. J. and Melzer, K.-J. (1971). Performance of Boeing LRV wheels in a lunar soil simulant. Report 1: Effect of wheel design and soil . U.S. Army Engineer Waterways Experiment Station, Technical Report M-71-10, Report 1. Source
    BibTeX
    @techreport{green1971performance,
  title = {Performance of Boeing LRV wheels in a lunar soil simulant. Report 1: Effect of wheel design and soil},
  author = {Green, Andrew J. and Melzer, Klaus-Jurgen},
  number = {Technical Report M-71-10, Report 1},
  institution = {U.S. Army Engineer Waterways Experiment Station},
  year = {1971},
  url = {https://erdc-library.erdc.dren.mil/handle/11681/29961}
}
  3. Melzer, K.-J. (1971). Performance of the Boeing LRV wheels in a lunar soil simulant. Report 2: Effects of speed, Wheel load, and soil . U.S. Army Engineer Waterways Experiment Station, NASA-CR-129612. Source
    BibTeX
    @techreport{melzer1971performance,
  title = {Performance of the Boeing LRV wheels in a lunar soil simulant. Report 2: Effects of speed, Wheel load, and soil},
  author = {Melzer, Klaus-Jurgen},
  number = {NASA-CR-129612},
  institution = {U.S. Army Engineer Waterways Experiment Station},
  year = {1971},
  url = {https://ntrs.nasa.gov/citations/19730004536},
  abstract = {Two nearly identical Boeing-GM wire-mesh Lunar Roving Vehicle (LRV) wheels were laboratory tested in a lunar soil simulant to determine the influence of wheel speed and acceleration, wheel load, presence of a fender, travel direction, and soil strength on the wheel performance. Constant-slip and three types of programmed-slip tests were conducted with a single-wheel dynamometer system. Test results indicated that performance of single LRV wheels in terms of pull coefficient, power number, and efficiency were not influenced by wheel speed and acceleration, travel direction, the presence of a fender, or wheel load. Of these variables, only load influenced sinkage, which increased with increasing load. For a given slip, the pull coefficient and power number increased with increasing soil strength. However, for a given pull coefficient or slope, slip was less in firmer soil; thus, the power number decreased and efficiency increased with increasing soil strength.}
}
  4. Wiendieck, K. W. (1968). Stress-displacement relations and terrain-vehicle mechanics: a critical discussion . Journal of Terramechanics. Source
    BibTeX
    @article{wiendieck1968stress,
  title = {Stress-displacement relations and terrain-vehicle mechanics: a critical discussion},
  author = {Wiendieck, Klaus W.},
  journal = {Journal of Terramechanics},
  volume = {5},
  pages = {67-85},
  year = {1968},
  doi = {10.1016/0022-4898(68)90081-5}
}
  5. Asnani, V., Delap, D. and Creager, C. (2009). The Development of Wheels for the Lunar Roving Vehicle . Journal of Terramechanics, NASA/TM-2009-215798, 20100000019. Source
    BibTeX
    @article{asnani2009development,
  title = {The Development of Wheels for the Lunar Roving Vehicle},
  author = {Asnani, Vivake and Delap, Damon and Creager, Colin},
  journal = {Journal of Terramechanics},
  volume = {46},
  number = {NASA/TM-2009-215798, 20100000019},
  pages = {89-103},
  institution = {NASA Glenn Research Center},
  year = {2009},
  doi = {10.1016/j.jterra.2009.02.005},
  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.}
}
  6. Creager, C., Asnani, V., Oravec, H. and Woodward, A. (2017). Drawbar Pull (DP) Procedures for Off-Road Vehicle Testing . NASA Glenn Research Center, NASA/TP-2017-219384. Source
    BibTeX
    @techreport{creager2017drawbar,
  title = {Drawbar Pull (DP) Procedures for Off-Road Vehicle Testing},
  author = {Creager, Colin and Asnani, Vivake and Oravec, Heather and Woodward, Adam},
  number = {NASA/TP-2017-219384},
  institution = {NASA Glenn Research Center},
  year = {2017},
  url = {https://ntrs.nasa.gov/citations/20170010706},
  abstract = {As NASA strives to explore the surface of the Moon and Mars, there is a continued need for improved tire and vehicle development. When tires or vehicles are being designed for off-road conditions where significant thrust generation is required, such as climbing out of craters on the Moon, it is important to use a standard test method for evaluating their tractive performance. The drawbar pull (DP) test is a way of measuring the net thrust generated by tires or a vehicle with respect to performance metrics such as travel reduction, sinkage, or power efficiency. DP testing may be done using a single tire on a traction rig, or with a set of tires on a vehicle; this report focuses on vehicle DP tests. Though vehicle DP tests have been used for decades, there are no standard procedures that apply to exploration vehicles. This report summarizes previous methods employed, shows the sensitivity of certain test parameters, and provides a body of knowledge for developing standard testing procedures. The focus of this work is on lunar applications, but these test methods can be applied to terrestrial and planetary conditions as well. Section 1.0 of this report discusses the utility of DP testing for off-road vehicle evaluation and the metrics used. Section 2.0 focuses on test-terrain preparation, using the example case of lunar terrain. There is a review of lunar terrain analogs implemented in the past and a discussion on the lunar terrain conditions created at the NASA Glenn Research Center, including methods of evaluating the terrain strength variation and consistency from test to test. Section 3.0 provides details of the vehicle test procedures. These consist of a review of past methods, a comprehensive study on the sensitivity of test parameters, and a summary of the procedures used for DP testing at Glenn.}
}
  7. Rush, E. S., Schreiner, B. G. and Willoughby, W. E. (1978). Limited Evaluation of Experimental and Standard Tractor Dozer Blades . U.S. Army Engineer Waterways Experiment Station, Miscellaneous Paper M-78-5. Source
    BibTeX
    @techreport{rush1978limited,
  title = {Limited Evaluation of Experimental and Standard Tractor Dozer Blades},
  author = {Rush, Edgar S. and Schreiner, Barton G. and Willoughby, William E.},
  number = {Miscellaneous Paper M-78-5},
  institution = {U.S. Army Engineer Waterways Experiment Station},
  year = {1978},
  url = {https://erdc-library.erdc.dren.mil/handle/11681/48785}
}
  8. US Army Engineer Research and Development Center. (1999). Waterways Experiment Station (WES), 1 March 1937 to 30 September 1999. erdc-library.erdc.dren.mil/jspui/handle/11681/22942
    BibTeX
    @misc{erdc1999wes,
  title = {Waterways Experiment Station (WES), 1 March 1937 to 30 September 1999},
  author = {{US Army Engineer Research} and {Development Center}},
  organization = {erdc-library.erdc.dren.mil},
  year = {1999},
  url = {https://erdc-library.erdc.dren.mil/jspui/handle/11681/22942}
}
  9. International Society for Terrain-Vehicle Systems. (2026). ISTVS Mississippi State University Student Chapter Visits U.S. Army ERDC Mobility Systems Branch. istvs.org/newswire/msu-student-chapter-visits-erdc-msb
    BibTeX
    @misc{istvs2026erdc,
  title = {ISTVS Mississippi State University Student Chapter Visits U.S. Army ERDC Mobility Systems Branch},
  author = {{International Society for Terrain-Vehicle Systems}},
  organization = {istvs.org},
  year = {2026},
  url = {https://www.istvs.org/newswire/msu-student-chapter-visits-erdc-msb}
}
  10. Freitag, D. R. (1965). Wheels on soft soils: an analysis of existing data . U.S. Army Engineer Waterways Experiment Station, Technical Report No. 3-670. Source
    BibTeX
    @techreport{freitag1965wheels,
  title = {Wheels on soft soils: an analysis of existing data},
  author = {Freitag, Dean R.},
  number = {Technical Report No. 3-670},
  institution = {U.S. Army Engineer Waterways Experiment Station},
  year = {1965},
  url = {https://erdc-library.erdc.dren.mil/handle/11681/4716}
}
  11. Wong, J. Y. and Reece, A. R. (1967). Prediction of Rigid Wheel Performance Based on the Analysis of Soil-Wheel Stresses . Journal of Terramechanics, 2. Source
    BibTeX
    @article{wong1967prediction,
  title = {Prediction of Rigid Wheel Performance Based on the Analysis of Soil-Wheel Stresses},
  author = {Wong, J. Y. and Reece, A. R.},
  journal = {Journal of Terramechanics},
  volume = {4},
  number = {2},
  pages = {7--25},
  year = {1967},
  doi = {10.1016/0022-4898(67)90047-x}
}
  12. Costes, N. C., Farmer, J. E. and George, E. B. (1972). Mobility Performance of the Lunar Roving Vehicle: Terrestrial Studies --- Apollo 15 Results . Conference of the International, NASA TR R-401, 19730008090. Source
    BibTeX
    @inproceedings{costes1972mobility,
  title = {Mobility Performance of the Lunar Roving Vehicle: Terrestrial Studies --- Apollo 15 Results},
  author = {Costes, Nicholas C. and Farmer, John E. and George, Edwin B.},
  booktitle = {Conference of the International},
  number = {NASA TR R-401, 19730008090},
  institution = {NASA Marshall Space Flight Center},
  address = {Stockholm and Kiruna},
  month = {12},
  year = {1972},
  url = {https://ntrs.nasa.gov/citations/19730008090},
  abstract = {The constriants of the Apollo 15 mission dictated that the average and limiting performance capabilities of the first manned lunar roving vehicle be known or estimated within narrow margins. Extensive studies were conducted and are compared with the actual performance of the lunar roving vehicle during the Apollo 15 mission. From this comparison, conclusions are drawn relating to the capabilities and limitation of current terrestrial methodology in predicting the mobility performance of lunar roving vehicles under in-situ environmental conditions, and recommendations are offered concerning the performance of surface vehicles on future missions related to lunar or planetary exploration.}
}
  13. Costes, N. C., Cohron, G. T. and Moss, D. C. (1971). Cone Penetration Resistance Test---An Approach to Evaluating In-Place Strength and Packing Characteristics of Lunar Soils . Lunar Science Conference. Source
    BibTeX
    @inproceedings{costes1971cone,
  title = {Cone Penetration Resistance Test---An Approach to Evaluating In-Place Strength and Packing Characteristics of Lunar Soils},
  author = {Costes, Nicholas C. and Cohron, G. T. and Moss, D. C.},
  booktitle = {Lunar Science Conference},
  volume = {3},
  pages = {1973-1987},
  publisher = {The M.I.T. Press},
  year = {1971},
  url = {https://articles.adsabs.harvard.edu/pdf/1971LPSC....2.1973C}
}
  14. Houston, W. N. and Mitchell, J. K. (1970). Lunar Surface Engineering Properties Experiment Definition. Volume 1: Mechanics and Stabilization of Lunar Soils . University of California, Berkeley, for NASA Marshall Space Flight Center, NASA-CR-102963. Source
    BibTeX
    @techreport{houston1970lunar,
  title = {Lunar Surface Engineering Properties Experiment Definition. Volume 1: Mechanics and Stabilization of Lunar Soils},
  author = {Houston, William N. and Mitchell, James K.},
  number = {NASA-CR-102963},
  institution = {University of California, Berkeley, for NASA Marshall Space Flight Center},
  year = {1970},
  url = {https://ntrs.nasa.gov/citations/19710005729},
  abstract = {Studying simulated lunar soil for determining feasibility of proposed geotechnical tests for Apollo missions}
}
  15. Houston, W. N. and Namiq, L. (1971). Penetration resistance of lunar soils . Journal of Terramechanics, 1. Source
    BibTeX
    @article{houston1971penetration,
  title = {Penetration resistance of lunar soils},
  author = {Houston, William N. and Namiq, L.I.},
  journal = {Journal of Terramechanics},
  volume = {8},
  number = {1},
  pages = {59-69},
  publisher = {Elsevier BV},
  year = {1971},
  doi = {10.1016/0022-4898(71)90071-1}
}
  16. Mitchell, J. K., Carrier, W. D. I., Costes, N. C., Houston, W. N., Scott, R. F. and Hovland, H. J. (1974). Apollo soil mechanics experiment S-200 . NASA, NASA-CR-134306. Source
    BibTeX
    @techreport{mitchell1974apollo,
  title = {Apollo soil mechanics experiment S-200},
  author = {Mitchell, James K. and Carrier, W. D., III and Costes, Nicholas C. and Houston, William N. and Scott, Ronald F. and Hovland, H. John},
  number = {NASA-CR-134306},
  institution = {NASA},
  year = {1974},
  url = {https://ntrs.nasa.gov/citations/19740019219},
  abstract = {The physical and mechanical properties of the unconsolidated lunar surface material samples that were obtained during the Apollo missions were studied. Sources of data useful for deduction of soil information, and methods used to obtained the data are indicated. A model for lunar soil behavior is described which considers soil characteristics, density and porosity, strength, compressibility, and trafficability parameters. Lunar history and processes are considered, and a comparison is made of lunar and terrestrial soil behavior. The impact of the findings on future exploration and development of the moon are discussed, and publications resulting from lunar research by the soil mechanics team members are listed.}
}
  17. Scott, R. F. (1975). Apollo Program Soil Mechanics Experiment: Final Report . California Institute of Technology, NASA Contract NAS 9-11454. Source
    BibTeX
    @techreport{scott1975apollo,
  title = {Apollo Program Soil Mechanics Experiment: Final Report},
  author = {Scott, Ronald F.},
  number = {NASA Contract NAS 9-11454},
  institution = {California Institute of Technology},
  year = {1975},
  url = {https://ntrs.nasa.gov/citations/19750023910},
  abstract = {The soil mechanics investigation was conducted to obtain information relating to the landing interaction of the lunar module (LM) with the lunar surface, and lunar soil erosion caused by the spacecraft engine exhaust. Results obtained by study of LM landing performance on each Apollo mission are summarized.}
}
  18. Jones, C. S. J., Nola, F. J. and Doran, B. J. (1969). Traction drive system design considerations for a lunar roving vehicle . SAE Technical Paper Series, NASA-TM-. Source
    BibTeX
    @inproceedings{jones1969traction,
  title = {Traction drive system design considerations for a lunar roving vehicle},
  author = {Jones, C. S., Jr. and Nola, F. J. and Doran, B. J.},
  booktitle = {SAE Technical Paper Series},
  volume = {1},
  number = {NASA-TM-},
  institution = {NASA},
  year = {1969},
  doi = {10.4271/700023},
  abstract = {<div class="htmlview paragraph">For an optimum design, the weight, energy consumption, and operational flexibility of the traction drive system for a lunar roving vehicle must be considered along with the power supply, motor, and power train.</div> <div class="htmlview paragraph">Other problems considered in this paper include: environment and motor dissipation; motor type (a-c or d-c) and commutation if d-c; motor controller (switching of large currents); delivery of torque at varying speeds; the power train; use of regenerative braking and conservation of energy; and power supply voltage variation. These problems are studied in the light of certain general system specifications, which fall into weight, performance, and environment categories. Tradeoff studies are considered for purposes of optimization in each of these areas.</div> <div class="htmlview paragraph">Special consideration is given to the controller and system design as it pertains to regenerative braking and the conservation of energy. Some aspects of changing the modes of motor operation to satisfy extreme performance requirements of speed and torque are discussed.</div>}
}
  19. NASA. (1970). Design and Manufacture of Wheels for A Dual-Mode (Manned - Automatic) Lunar Surface Roving Vehicle. Volume 2: Proposed Test Plan . NASA, NASA-CR-163200. Source
    BibTeX
    @techreport{nasa1970design,
  title = {Design and Manufacture of Wheels for A Dual-Mode (Manned - Automatic) Lunar Surface Roving Vehicle. Volume 2: Proposed Test Plan},
  author = {{NASA}},
  number = {NASA-CR-163200},
  institution = {NASA},
  year = {1970},
  url = {https://ntrs.nasa.gov/citations/19800016718},
  abstract = {A developmental test plan for the wheel and wheel drive assembly of the dual-mode (manned/automated) lunar surface roving vehicle is presented. The tests cover performance, as well as critical environmental characteristics. Insofar as practical, the environmental conditions imposed will be in the sequence expected during the hardware's life from storage through the lunar mission. Test procedures are described for static load deflection and endurance tests. Soft soil tests to determine mobility characteristics including drawbar-pull and thrust vs slip, and motion resistance for various wheel loads are also discussed. Test designs for both ambient and thermal vacuum conditions are described. Facility, transducer, and instrumentation requirements are outlined.}
}
  20. Mullis, C. H. (1971). A Study and Analysis of the MSFC Lunar Roving Vehicle Dust Profile Test Program . Northrop Services, Inc., for NASA Marshall Space Flight Center, Contract NAS8-26175. Source
    BibTeX
    @techreport{mullis1971study,
  title = {A Study and Analysis of the {MSFC} Lunar Roving Vehicle Dust Profile Test Program},
  author = {Mullis, C. H.},
  number = {Contract NAS8-26175},
  institution = {Northrop Services, Inc., for NASA Marshall Space Flight Center},
  year = {1971},
  url = {https://ntrs.nasa.gov/citations/19720007590},
  abstract = {The dust problem and fender design for the LRV were studied under reduced gravity with a lunar soil simulant. The test equipment, soil characteristics of the lunar soil simulant, and the test procedures are described.  It is concluded: (1) The fender plus flap design is adequate. (2) Vacuum conditions tend to eliminate or reduce suspended dust clouds. (3) Reduced gravity conditions tend to increase the dust problems. (4) Slow starting speeds are necessary to minimize slip and reduce initial dust generation.}
}
  21. Kobayashi, T., Fujiwara, Y., Yamakawa, J., Yasufuku, N. and Omine, K. (2010). Mobility performance of a rigid wheel in low gravity environments . Journal of Terramechanics, 4. Source
    BibTeX
    @article{kobayashi2010mobility,
  title = {Mobility performance of a rigid wheel in low gravity environments},
  author = {Kobayashi, Taizo and Fujiwara, Yoichiro and Yamakawa, Junya and Yasufuku, Noriyuki and Omine, Kiyoshi},
  journal = {Journal of Terramechanics},
  volume = {47},
  number = {4},
  pages = {261-274},
  publisher = {Elsevier BV},
  year = {2010},
  doi = {10.1016/j.jterra.2009.12.001}
}
  22. Apfelbeck, M., Kuß, S., Wedler, A., Gibbesch, A., Rebele, B. and Schäfer, B. (2009). A Novel Terramechanics Testbed Setup for Planetary Rover Wheel-Soil Interaction . European Regional Conference of the International Society for Terrain-Vehicle Systems. Source
    BibTeX
    @inproceedings{apfelbeck2009novel,
  title = {A Novel Terramechanics Testbed Setup for Planetary Rover Wheel-Soil Interaction},
  author = {Apfelbeck, Maximilian and Kuß, Sebastian and Wedler, Armin and Gibbesch, Andreas and Rebele, Bernhard and Schäfer, Bernd},
  booktitle = {European Regional Conference of the International Society for Terrain-Vehicle Systems},
  address = {Bremen},
  year = {2009},
  url = {https://elib.dlr.de/62703/}
}
  23. Ishigami, G., Miwa, A., Nagatani, K. and Yoshida, K. (2007). Terramechanics-based model for steering maneuver of planetary exploration rovers on loose soil . Journal of Field Robotics, 3. Source
    BibTeX
    @article{ishigami2007terramechanics,
  title = {Terramechanics-based model for steering maneuver of planetary exploration rovers on loose soil},
  author = {Ishigami, Genya and Miwa, Akiko and Nagatani, Keiji and Yoshida, Kazuya},
  journal = {Journal of Field Robotics},
  volume = {24},
  number = {3},
  pages = {233-250},
  publisher = {Wiley},
  year = {2007},
  doi = {10.1002/rob.20187},
  abstract = {Abstract This paper presents analytical models to investigate the steering maneuvers of planetary exploration rovers on loose soil. The models are based on wheel‐soil interaction mechanics, or terramechanics, with which the traction and disturbance forces of a wheel are evaluated for various slip conditions. These traction forces are decomposed into the longitudinal and lateral directions of the wheel. The latter component, termed the side force has a major influence in characterizing the steering maneuvers of the rover. In this paper, the wheel‐soil mechanics models are developed with particular attention to the side force and the validity of the model is confirmed by using a single‐wheel test bed. The motion profile of the entire rover is numerically evaluated by incorporating the wheel‐soil models into an articulated multibody model that describes the motion dynamics of the vehicle's body and chassis. Steering maneuvers are investigated under different steering angles by using a four‐wheel rover test bed on simulated lunar soil regolith simulant. The experimental results are compared with the simulation results using the corresponding model parameters. The proposed wheel‐and‐vehicle model demonstrates better accuracy in predicting steering maneuvers as compared to the conventional kinematics‐based model. © 2006 Wiley Periodicals, Inc.}
}
  24. Lyasko, M. (2009). Slip sinkage effect in soil–vehicle mechanics . Journal of Terramechanics. Source
    BibTeX
    @article{lyasko2009slip,
  title = {Slip sinkage effect in soil–vehicle mechanics},
  author = {Lyasko, Modest},
  journal = {Journal of Terramechanics},
  volume = {47},
  pages = {21-31},
  year = {2009},
  doi = {10.1016/j.jterra.2009.08.005}
}
  25. Nakashima, H., Fujii, H., Oida, A., Momozu, M., Kanamori, H., Aoki, S., Yokoyama, T., Shimizu, H., Miyasaka, J. and Ohdoi, K. (2010). Discrete Element Method Analysis of Single Wheel Performance for a Small Lunar Rover on Sloped Terrain . Journal of Terramechanics, 5. Source
    BibTeX
    @article{nakashima2010discrete,
  title = {Discrete Element Method Analysis of Single Wheel Performance for a Small Lunar Rover on Sloped Terrain},
  author = {Nakashima, H. and Fujii, H. and Oida, A. and Momozu, M. and Kanamori, H. and Aoki, S. and Yokoyama, T. and Shimizu, H. and Miyasaka, J. and Ohdoi, K.},
  journal = {Journal of Terramechanics},
  volume = {47},
  number = {5},
  pages = {307--321},
  year = {2010},
  doi = {10.1016/j.jterra.2010.04.001}
}
  26. Schepelmann, A., Creager, C. M., Proctor, M. P., Johnson, K. A., Breckenridge, J. R., Elmland, A., Naghipour Ghezeljeh, P. and Oravec, H. A. (2025). An Overview of Tire-Ground Contact Modeling Approaches for Surface Mobility Applications . NASA Glenn Research Center, NASA/TM-20250006958. Source
    BibTeX
    @techreport{schepelmann2025overview,
  title = {An Overview of Tire-Ground Contact Modeling Approaches for Surface Mobility Applications},
  author = {Schepelmann, Alexander and Creager, Colin M. and Proctor, Margaret P. and Johnson, Kyle A. and Breckenridge, John R. and Elmland, Asher and Naghipour Ghezeljeh, Paria and Oravec, Heather A.},
  number = {NASA/TM-20250006958},
  institution = {NASA Glenn Research Center},
  year = {2025},
  url = {https://ntrs.nasa.gov/citations/20250006958},
  abstract = {Wheels and tires serve as the critical interface between vehicles and the ground, enabling traction, force transmission, and ultimately mobility. As planetary exploration systems adopt increasingly complex wheel and tire designs, look to explore increasingly extreme terrains, and adopt increasingly aggressive performance requirements, physics-based modeling has become essential for both designing these mechanisms and predicting performance under conditions that are difficult or impractical to replicate experimentally, such as reduced gravity. This paper provides a high-level overview of commonly used modeling approaches for simulating tireground interaction, including those currently employed or under development at NASA Glenn Research Center, NASA Johnson Space Center, and the Jet Propulsion Laboratory. The paper first categorizes modeling techniques based on their fidelity and underlying assumptions. It then discusses the applications, benefits, and limitations of each approach, highlighting current knowledge gaps and modeling challenges. Finally, the paper outlines ongoing and future work aimed at addressing these limitations, including initial results from automated soil preparation experiments that support the generation of consistent physical test data and the development of terramechanics simulations for evaluating and comparing model fidelity.}
}
  27. Creager, C., Moreland, S., Skonieczny, K., Johnson, K., Asnani, V. and Gilligan, R. (2012). Benefit of Push-pull Locomotion for Planetary Rover Mobility . ASCE Earth and Space Conference. Source
    BibTeX
    @inproceedings{creager2012benefit,
  title = {Benefit of Push-pull Locomotion for Planetary Rover Mobility},
  author = {Creager, Colin and Moreland, Scott and Skonieczny, Krzysztof and Johnson, Kyle and Asnani, Vivake and Gilligan, Ryan},
  booktitle = {ASCE Earth and Space Conference},
  pages = {11-20},
  publisher = {American Society of Civil Engineers},
  year = {2012},
  doi = {10.1061/9780784412190.002},
  abstract = {As NASA's exploration missions on planetary terrains become more aggressive, a focus on alternative modes of locomotion for rovers is necessary. In addition to climbing steep slopes, the terrain in these extreme environments is often unknown and can be extremely hard to traverse, increasing the likelihood of a vehicle or robot becoming damaged or immobilized. The conventional driving mode in which all wheels are either driven or free-rolling is very efficient on flat hard ground, but does not always provide enough traction to propel the vehicle through soft or steep terrain. This paper presents an alternative mode of travel and investigates the fundamental differences between these locomotion modes. The methods of "push-pull" locomotion discussed can be used with articulated wheeled vehicles and are identified as "walking" or "inching/inch-worming". In both cases, the braked non-rolling wheels provide increased thrust. An in-depth study of how soil reacts under a rolling wheel vs. a braked wheel was performed by visually observing the motion of particles beneath the surface. This novel technique consists of driving or dragging a wheel in a soil bin against a transparent wall while high resolution, high-rate photographs are taken. Optical flow software was then used to determine shearing patterns in the soil. Different failure modes were observed for the rolling and braked wheel cases. A quantitative comparison of inching vs. conventional driving was also performed on a full-scale vehicle through a series of drawbar pull tests in the Lunar terrain strength simulant, GRC-1. The effect of tire stiffness was also compared; typically compliant tires provide better traction when driving in soft soil, however it's been observed that rigid wheels may provide better thrust when non-rolling. Initial tests indicate up to a possible 40% increase in pull force capability at high slip when inching vs. rolling.}
}
  28. Skonieczny, K., Niksirat, P. and Nassiraei, A. A. F. (2019). Rapid automated soil preparation for testing planetary rover-soil interactions aboard reduced-gravity aircraft . Journal of Terramechanics. Source
    BibTeX
    @article{skonieczny2019rapid,
  title = {Rapid automated soil preparation for testing planetary rover-soil interactions aboard reduced-gravity aircraft},
  author = {Skonieczny, Krzysztof and Niksirat, Parna and Nassiraei, Amir Ali Forough},
  journal = {Journal of Terramechanics},
  volume = {83},
  pages = {35-44},
  publisher = {Elsevier BV},
  year = {2019},
  doi = {10.1016/j.jterra.2019.03.001}
}
  29. Daca, A. (2023). Predicting Planetary Rover Mobility in Reduced Gravity Using 1-g Experiments . Unpublished. Source
    BibTeX
    @phdthesis{daca2023predicting,
  title = {Predicting Planetary Rover Mobility in Reduced Gravity Using 1-g Experiments},
  author = {Daca, Adriana},
  journal = {Unpublished},
  school = {Concordia University},
  address = {Montreal, Quebec, Canada},
  type = {PhD thesis},
  month = {February},
  year = {2023},
  doi = {10.13140/rg.2.2.12718.28485},
  abstract = {Traversing granular regolith, especially in reduced gravity environments, remains a potential challenge for wheeled rovers. Mitigating hazards for planetary rovers requires testing in representative environments, but direct Earth-based testing fails to account for the effect of reduced gravity on the soil itself. Here, experimental apparatus and techniques for reduced-gravity flight testing are used to systematically evaluate three existing Earth-based testing methods and develop guidelines for their use and interpretation: (i) reduced-weight testing, (ii) matching soil testing instrument response through soil simulant design, and (iii) granular scaling laws (GSL). \nExperimentation campaigns flying reduced-gravity parabolas, with soil and wheel both in lunar-g, have shown reductions in net traction of 20% or more and increases in sinkage of up to 40% compared to Earth-based testing methods (i) and (ii). Scaled-wheel testing, according to GSL (method iii) has shown better agreement with reduced-g tests (less than 10% error) and also tends to err on the side of conservative predictions. \nLimitations of GSL are investigated including a recently proposed cohesion constraint (that the wheel radius ratio must be the inverse of the gravity ratio) and the effects of wheel size and aspect ratio on GSL’s accuracy. It was found that the cohesion constraint can most likely be ignored for mildly cohesive soils such as lunar regolith. Limits on wheel sizes and aspect ratio variation are also proposed. \nThe application of GSL to planetary rover testing is demonstrated through two studies undertaken in collaboration with NASA’s Jet Propulsion Laboratory. One study compares wheel designs for a skid-steer lunar rover in single-wheel tests scaled by GSL, demonstrating that diagonal grousers improve turning performance without requiring larger wheels. The second study involves application of GSL to the design of two reconfigurable test platforms for evaluating steep-terrain mobility performance. \nAnother aspect of rover mobility testing—normal force control in single-wheel testbeds—is also investigated. An improved method for single-wheel testing, using a 4-bar mechanism, essentially eliminates normal force oscillations from frictional vertical sliders. \nFinally, guidelines for conducting and interpreting 1-g mobility tests for lunar rovers are presented, and potential avenues for future research are outlined.}
}
  30. Sohl, G. and Jain, A. (2005). Wheel-terrain contact modeling in the ROAMS planetary rover simulation . International Conference on Multibody Systems, Nonlinear Dynamics, and Control, Parts A, B, and C. Source
    BibTeX
    @inproceedings{sohl2005wheel,
  title = {Wheel-terrain contact modeling in the ROAMS planetary rover simulation},
  author = {Sohl, Garett and Jain, Abhinandan},
  booktitle = {International Conference on Multibody Systems, Nonlinear Dynamics, and Control, Parts A, B, and C},
  pages = {89-97},
  publisher = {ASMEDC},
  year = {2005},
  doi = {10.1115/detc2005-85620},
  abstract = {This paper describes wheel-terrain contact modeling in the ROAMS physics-based simulator for planetary surface exploration rover vehicles. ROAMS models a wide range of rover systems and provides a user interface to a simulated rover. The wheel-terrain interaction is of primary interest during rover motion over rough terrain. The wheel-terrain contact model must provide physically realistic behavior without being too computationally intensive for real-time simulation. Physically realistic behavior may be defined using empirical data and ROAMS provides mechanisms for tuning the contact model parameters to match this data. In cases where empirical data is non-existent or there are large amounts of uncertainty, ROAMS can be used to extrapolate a range of behaviors based on physical parameters. The ROAMS simulator can be used in stand-alone mode, for closed-loop simulation with on-board software or for operator-in-the-loop simulations.}
}
  31. Irani, R., Bauer, R. and Warkentin, A. (2011). A dynamic terramechanic model for small lightweight vehicles with rigid wheels and grousers operating in sandy soil . Acta Astronautica, 4. Source
    BibTeX
    @article{irani2011dynamic,
  title = {A dynamic terramechanic model for small lightweight vehicles with rigid wheels and grousers operating in sandy soil},
  author = {Irani, R.A. and Bauer, R.J. and Warkentin, A.},
  journal = {Acta Astronautica},
  volume = {48},
  number = {4},
  pages = {307-318},
  publisher = {Elsevier BV},
  year = {2011},
  doi = {10.1016/j.jterra.2011.05.001}
}
  32. Karpman, E. (2019). Discrete Element Modelling for Wheel-Soil Interaction and the Analysis of the Effect of Gravity . Journal of Terramechanics. Source
    BibTeX
    @article{karpman2019discrete,
  title = {Discrete Element Modelling for Wheel-Soil Interaction and the Analysis of the Effect of Gravity},
  author = {Karpman, Eric},
  journal = {Journal of Terramechanics},
  volume = {91},
  pages = {139-153},
  publisher = {Elsevier BV},
  school = {McGill University},
  address = {Montreal},
  year = {2019},
  doi = {10.1016/j.jterra.2020.06.002}
}
  33. Dallas, J., Cole, M. P., Jayakumar, P. and Ersal, T. (2020). Neural network based terramechanics modeling and estimation for deformable terrains . arXiv preprint. Source
    BibTeX
    @article{dallas2020neural,
  title = {Neural network based terramechanics modeling and estimation for deformable terrains},
  author = {Dallas, James and Cole, Michael P. and Jayakumar, Paramsothy and Ersal, Tulga},
  journal = {arXiv preprint},
  year = {2020},
  doi = {10.48550/arxiv.2003.02635},
  abstract = {In this work, a neural network based terramechanics model and terrain estimator are presented with an outlook for optimal control applications such as model predictive control. Recognizing the limitations of the state-of-the-art terramechanics models in terms of operating conditions, computational cost, and continuous differentiability for gradient-based optimization, an efficient and twice continuously differentiable terramechanics model is developed using neural networks for dynamic operations on deformable terrains. It is demonstrated that the neural network terramechanics model is able to predict the lateral tire forces accurately and efficiently compared to the Soil Contact Model as a state-of-the-art model. Furthermore, the neural network terramechanics model is implemented within a terrain estimator and it is shown that using this model the estimator converges within around 2% of the true terrain parameter. Finally, with model predictive control applications in mind, which typically rely on bicycle models for their predictions, it is demonstrated that utilizing the estimated terrain parameter can reduce prediction errors of a bicycle model by orders of magnitude. The result is an efficient, dynamic, twice continuously differentiable terramechanics model and estimator that has inherent advantages for implementation in model predictive control as compared to previously established models.}
}
  34. Abubakar, A., Alhammadi, R., Zweiri, Y. and Seneviratne, L. (2023). Advance Simulation Method for Wheel-Terrain Interactions of Space Rovers: A Case Study on the UAE Rashid Rover . arXiv preprint arXiv:2308.12431. Source
    BibTeX
    @article{abubakar2023advance,
  title = {Advance Simulation Method for Wheel-Terrain Interactions of Space Rovers: A Case Study on the UAE Rashid Rover},
  author = {Abubakar, Ahmad and Alhammadi, Ruqqayya and Zweiri, Yahya and Seneviratne, Lakmal},
  journal = {arXiv preprint arXiv:2308.12431},
  pages = {526-532},
  year = {2023},
  doi = {10.1109/icar58858.2023.10406669},
  abstract = {A thorough analysis of wheel-terrain interaction is crucial to ensure the safe and efficient operation of space rovers on extraterrestrial surfaces like the Moon or Mars. This paper presents an approach for developing and experimentally validating a novel virtual simulation method for the wheel-terrain interaction of the UAE Rashid rover's wheel. Specifically, the method is developed based on the modified Reece tire model in conjunction with the Grouser effect as an additional factor. The proposed method aims to improve the fidelity and capability of current simulation methods for space rovers. It considers various factors, such as wheel properties, wheel slippage, loose soil properties, and interaction mechanics. Moreover, the developed simulation method was validated through sets of experiments on a Test-rig that simulated lunar soil conditions. These experiments were carried out with different slip ratios of 0.00, 0.25, 0.50, and 0.75, to test the behaviors acted on the rover's wheel by the lunar soil. The obtained results demonstrate that the proposed simulation method provides an accurate and realistic simulation of the wheel-terrain interaction behavior, achieving an overall prediction accuracy of 95.57%.}
}
  35. Agarwal, S., Senatore, C., Zhang, T., Kingsbury, M., Iagnemma, K., Goldman, D. I. and Kamrin, K. (2019). Modeling of the Interaction of Rigid Wheels with Dry Granular Media . Journal of Terramechanics. Source
    BibTeX
    @article{agarwal2019modeling,
  title = {Modeling of the Interaction of Rigid Wheels with Dry Granular Media},
  author = {Agarwal, Shashank and Senatore, Carmine and Zhang, Tingnan and Kingsbury, Mark and Iagnemma, Karl and Goldman, Daniel I. and Kamrin, Ken},
  journal = {Journal of Terramechanics},
  volume = {85},
  pages = {1--14},
  year = {2019},
  doi = {10.1016/j.jterra.2019.06.001}
}
  36. Barrett, L., Durivage, T., McAuliffe, L., Potasiewicz, A., Simpson, C. and Yang, B. (2023). Reduced Gravity Airborne Mobility Testbed . Kennedy Space Center, 20230009749. Source
    BibTeX
    @techreport{barrett2023reduced,
  title = {Reduced Gravity Airborne Mobility Testbed},
  author = {Barrett, Liz and Durivage, Thomas and McAuliffe, Liam and Potasiewicz, Adam and Simpson, Catherine and Yang, Boxiong},
  number = {20230009749},
  institution = {Kennedy Space Center},
  year = {2023},
  url = {https://ntrs.nasa.gov/citations/20230009749},
  abstract = {Working in conjunction with the NASA Ames research center the goal of this senior design project was to develop a mobile test apparatus to enable wheel-soil interaction in a reduced gravity environment. In addition to collecting accurate wheel-soil interfacing data, a method of maintaining the density of the soil being used during the testing was developed to allow for repeatable testing conditions In order to meet these goals an annular testbed was design and built, providing an alternative to NASA’s linear rover wheel design. The circular design allowed for a smaller footprint and lighter device. The team found it was possible to set the desired slip ratio by rotating the both the annular testbed and wheel at different speeds. The Drawbar Pull force on the wheel was then measured with a torque sensor. Future work to be done includes improving the timing belt system, more robust control system, and more secure testbed base.}
}
  37. Buse, F. (2019). Fully Automated Single Wheel Testing with the DLR Terramechanics Robotics Locomotion Lab (TROLL) . Symposium on Advanced Space Technologies in Robotics and Automation. Source
    BibTeX
    @inproceedings{buse2019fully,
  title = {Fully Automated Single Wheel Testing with the {DLR} Terramechanics Robotics Locomotion Lab ({TROLL})},
  author = {Buse, Fabian},
  booktitle = {Symposium on Advanced Space Technologies in Robotics and Automation},
  organization = {European Space Agency},
  address = {Noordwijk, The Netherlands},
  year = {2019},
  url = {https://elib.dlr.de/128404/}
}
  38. Buse, F., Barthelmes, S., Chalon, M., Langofer, V., Bertleff, W., Lichtenheldt, R., Skibbe, J., Bihler, M., Holderried, R., Reill, J., Vodermayer, B., Stubbig, L., Bertrand, J., Tardivel, S., Vernazza, P., Murdoch, N., Ulamec, S. and Michel, P. (2021). Wheeled Locomotion in Milli-Gravity: A Technology Experiment for the MMX Rover . International Astronautical Congress, IAC-21,A3,4A,8,x64275. Source
    BibTeX
    @inproceedings{buse2021wheeled,
  title = {Wheeled Locomotion in Milli-Gravity: A Technology Experiment for the {MMX} Rover},
  author = {Buse, Fabian and Barthelmes, Stefan and Chalon, Maxime and Langofer, Viktor and Bertleff, Wieland and Lichtenheldt, Roy and Skibbe, Juliane and Bihler, Markus and Holderried, Roman and Reill, Josef and Vodermayer, Bernhard and Stubbig, Leon and Bertrand, Jean and Tardivel, Simon and Vernazza, Pierre and Murdoch, Naomi and Ulamec, Stephan and Michel, Patrick},
  booktitle = {International Astronautical Congress},
  number = {IAC-21,A3,4A,8,x64275},
  address = {Dubai, United Arab Emirates},
  year = {2021},
  url = {https://elib.dlr.de/144876/}
}
  39. Chen, J., Li, R. and Fu, S. (2026). Influence of Low Gravity on the Penetration Resistance of Lunar Regolith . npj Microgravity. Source
    BibTeX
    @article{chen2026influence,
  title = {Influence of Low Gravity on the Penetration Resistance of Lunar Regolith},
  author = {Chen, Jun and Li, Ruilin and Fu, Shigen},
  journal = {npj Microgravity},
  volume = {12},
  pages = {7},
  year = {2026},
  doi = {10.1038/s41526-026-00562-8},
  abstract = {Abstract Lunar surface operations conducted by the United States and the Soviet Union confirmed that penetration resistance is a key indicator for evaluating the engineering properties of lunar regolith. To quantitatively assess the influence of reduced gravity on penetration resistance, this study employed a newly developed Geotechnical Magnetic-gravity Modeling Test (GMMT) system to perform cone penetration tests under controlled gravitational acceleration levels of 1/6 g, 1 g, and 2 g. The results indicated that the normalized penetration resistance increased as gravity decreased, and this effect was amplified at higher relative densities. To investigate the underlying mechanisms, discrete element method (DEM) simulations were conducted. The findings revealed that, in addition to gravity, in situ factors such as high relative density and irregular particle morphology also significantly enhanced penetration resistance by strengthening interparticle contact and friction. These non-gravitational effects partially offset the expected reduction in resistance under lower gravity, leading to a smaller-than-anticipated decline. This study provides new insights into the gravity-dependent penetration behavior of lunar regolith.}
}
  40. Creager, C., Breckenridge, J., Johnson, K., Oravec, H., Moreland, S., Sobey, A. and McBryan, E. (2025). Best Practices for the Testing of Planetary Roving Vehicle Mobility Systems and Tires . NASA, 20250003470. Source
    BibTeX
    @techreport{creager2025best,
  title = {Best Practices for the Testing of Planetary Roving Vehicle Mobility Systems and Tires},
  author = {Creager, Colin and Breckenridge, John and Johnson, Kyle and Oravec, Heather and Moreland, Scott and Sobey, Alexander and McBryan, Emily},
  number = {20250003470},
  institution = {NASA},
  year = {2025},
  url = {https://ntrs.nasa.gov/citations/20250003470},
  abstract = {NASA has an extensive history of conducting mobility testing on planetary tires, rovers, and mobility subsystems.  This paper contains a summary of the best practices and lessons learned from past test approaches, as well as from relevant test methodologies external to NASA, with a focus on tires and mobility systems.  It is intended to be a resource for future planetary rover developments. This document, which will be released in two phases, serves two objectives:  1) compile the existing knowledge of mobility related testing within NASA; and 2) identify major gaps in mobility related test needs and suggest potential paths forward.  This first release of the document (early 2025) captures information based on the authors’ existing knowledge and an abbreviated literature review.  A more thorough version will be released in late 2025 and will include more information on test methods external to NASA, as well as additional lessons learned through further investigations.  The Lunar Terrain Vehicle (LTV) is used as case study to help identify major test needs; however, this document is intended to be applicable to a wide range of potential missions.  Though no current mobility standards exist for the testing of planetary tires and mobility subsystems, future motive is to utilize the information from this whitepaper to guide the development of NASA mobility test standards.}
}
  41. Daca, A., Tremblay, D. and Skonieczny, K. (2021). The Relationship between Cone Penetration Resistance and Wheel-Soil Interactions in Lunar Gravity . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{daca2021relationship,
  title = {The Relationship between Cone Penetration Resistance and Wheel-Soil Interactions in Lunar Gravity},
  author = {Daca, Adriana and Tremblay, Dominique and Skonieczny, Krzysztof},
  booktitle = {IEEE Aerospace Conference},
  pages = {1-11},
  publisher = {IEEE},
  year = {2021},
  doi = {10.1109/aero50100.2021.9438503},
  abstract = {One of the major challenges faced by planetary exploration rovers today is the negotiation of difficult terrain, such as fine granular regolith commonly found on the Moon and Mars. Typical Earth-based testing methods cannot accurately predict rover mobility in reduced gravity environments (i.e. the Moon and Mars) as they fail to account for the effect of reduced gravity on the soil itself. Preliminary efforts have been made to account for effects of gravity on granular materials, at least indirectly, through simulant design. The soil simulant GRC-1 is designed to produce cone penetrometer readings comparable to those collected on the Moon (i.e. in lunar gravity) during Apollo. The assumption is that replicating the mechanical properties of lunar soil in terms of cone penetration resistance will also replicate the response to vehicle loading in terms of traction. The present research was designed to thoroughly characterize this assumption by exploring the relationship between rover mobility and cone penetration resistance experimentally in lunar gravity (1/6-g) and terrestrial gravity (1-g). The cone penetrometer response of GRC-1 was measured at relative densities (DR'S) of 46%,63%, and 69 % in both 1-g and 1/6-g aboard parabolic flights producing effective lunar gravitational accelerations. Cone index gradient (G) values measured in 1/6-g were 4 x lower on average than those measured in 1-g, indicating a significant decrease in shear strength in lunar-g. Wheel-soil interactions between a smooth rigid wheel and G R C-1 were also characterized at 69% DR in 1/6-g. The wheel experiments measured wheel-soil interaction data at controlled slip values of 20 % and 70 %. Wheel-soil interaction data collected include subsurface soil imaging, force/torque sensor data, wheel sinkage, and motor current, with drawbar pull (DP) and sinkage data reported here. Average DP/W values observed at 20% slip and 70% slip were 0.11 ± 0.02 and 0.32 ± 0.03, respectively, and maximum observed sinkage was 9.0 ± 1.9 mm and 16.2 ± 2.1 mm at 20% and 70 % slip, respectively. These results will be compared to 1-g experiments in a lower-density soil that produces an equivalent cone penetrometer response in order to test the hypothesis that equivalent wheel performance will be observed in soil with equal G values across differing gravity levels.}
}
  42. Duffey, C., Lea, M. and Brisset, J. (2025). Measuring regolith strength in reduced gravity environments in the laboratory . Review of Scientific Instruments. Source
    BibTeX
    @article{duffey2025measuring,
  title = {Measuring regolith strength in reduced gravity environments in the laboratory},
  author = {Duffey, C. and Lea, M. and Brisset, Julie},
  journal = {Review of Scientific Instruments},
  volume = {96},
  year = {2025},
  doi = {10.1063/5.0249495},
  abstract = {This paper presents the design and development of a Shear and Compression Cell (SCC) for measuring the mechanical properties of granular materials in low-gravity environments. This research is motivated by the increasing interest in planetary exploration missions that involve surface interactions, such as those to asteroids and moons. The SCC is designed to measure key mechanical properties, including Young’s modulus, angle of internal friction, bulk cohesion, and tensile strength, under both reduced gravity and microgravity conditions. Using a drop tower with interchangeable configurations, we can simulate the gravitational environments of celestial bodies such as the Moon and Titan. The SCC, coupled with the drop tower, provides a valuable tool for understanding the behavior of regolith materials and their implications for future space exploration missions.}
}
  43. Gerdts, S., Breckenridge, J. and Johnson, K. (2022). Lunar Rover Optimization Platform for Wheel Traction Studies . NASA Glenn Research Center, 20200003006. Source
    BibTeX
    @techreport{gerdts2022lunar,
  title = {Lunar Rover Optimization Platform for Wheel Traction Studies},
  author = {Gerdts, Stephen and Breckenridge, John and Johnson, Kyle},
  number = {20200003006},
  institution = {NASA Glenn Research Center},
  year = {2022},
  doi = {10.26226/m.632b0aa4f30377bc3bafa246},
  abstract = {Robotic mobility systems expand the reach of future scientific and exploration missions to celestial bodies. Understanding the traction performance of these systems is necessary knowledge that informs mission-level requirements, such as power budgets and navigation envelopes. This paper covers the design, development, and verification of the four wheeled Lunar Rover Optimization Platform (LROP). This mass optimized platform is targeted to emulate future medium class rovers weighing up to 90 kg. The LROP has the ability to conduct various wheel design experiments such as obstacle traversal, slope ascent, and drawbar pull over a wheel loading range of 4.5 to 22.7 kg. The platform also has the ability to shift its center of gravity (CG) laterally and longitudinally to explore the CG shift effects on mobility performance. This knowledge is valuable for future rover designers exploring different payload packaging solutions. In this paper results from obstacle traversal test with varying angle of attack (AOA) and longitudinal CG position are reported along with results from slope ascent testing which proved-out the LROPs capabilities.}
}
  44. Graser, E., McGill, S. M., Rankin, A. and Bielawiec, A. (2020). Rimmed Wheel Performance on the Mars Science Laboratory Scarecrow Rover . IEEE Aerospace Conference, 20220000759. Source
    BibTeX
    @inproceedings{graser2020rimmed,
  title = {Rimmed Wheel Performance on the Mars Science Laboratory Scarecrow Rover},
  author = {Graser, Evan and McGill, Sean M. and Rankin, Arturo and Bielawiec, Alex},
  booktitle = {IEEE Aerospace Conference},
  number = {20220000759},
  pages = {1-12},
  institution = {NASA},
  year = {2020},
  doi = {10.1109/aero47225.2020.9172666},
  abstract = {The Mars Science Laboratory (MSL) Curiosity rover experienced increasing wheel damage beginning in October 2013. While the wheels were designed to operate with considerable damage, the rate at which damage was occurring was unexpected and raised concerns regarding wheel life expectancy. As of Sol 2555 (10-14-19), there are two broken grousers on the left middle wheel, and one broken grouser on the right middle wheel. One possible scenario, albeit remote, is that enough grousers break on a wheel such that unconstrained portions of the wheel could contact the cable running from the rover motor controller assembly to the wheel's drive actuator. If the cable to a drive actuator is damaged, that wheel may no longer respond to commands. To make progress towards a navigation goal position, that wheel would need to be dragged. To mitigate the risk of damaging a cable running to a wheels drive actuator, the unconstrained portion of a wheel could be strategically shed by performing driving maneuvers on an immovable rock. What would remain after wheel shedding is a rimmed wheel (the outer 1/3 of the wheel). We studied the feasibility of remotely commanding the rover to perform the shed maneuver on one of its front wheels. To inform whether or not to shed the wheels, we tested the performance of driving on one or more rimmed wheels in flight. This led to a two-month test campaign in the Jet Propulsion Laboratory (JPL) Mars Yard using the Scarecrow testbed rover. Driving and steering performance was characterized on a variety of terrain types and slopes in a worst-case rimmed wheeled configuration. Test results indicate that if wheel shedding could be successfully executed in flight, Curiosity could continue to drive indefinitely on rimmed wheels.}
}
  45. Hu, W., Li, P., Rogg, A., Schepelmann, A., Creager, C., Chandler, S., Kamrin, K. and Negrut, D. (2024). Using physics-based simulation towards eliminating empiricism in extraterrestrial terramechanics applications . arXiv preprint. Source
    BibTeX
    @article{hu2024physics,
  title = {Using physics-based simulation towards eliminating empiricism in extraterrestrial terramechanics applications},
  author = {Hu, Wei and Li, Pei and Rogg, Arno and Schepelmann, Alexander and Creager, Colin and Chandler, Samuel and Kamrin, Ken and Negrut, Dan},
  journal = {arXiv preprint},
  year = {2024},
  doi = {10.13140/rg.2.2.33352.94728}
}
  46. Hu, W., Li, P., Rogg, A., Schepelmann, A., Chandler, S., Kamrin, K. and Negrut, D. (2025). A Study Demonstrating that Using Gravitational Offset to Prepare Extraterrestrial Mobility Missions is Misleading . NASA, 20250001809. Source
    BibTeX
    @techreport{hu2025study,
  title = {A Study Demonstrating that Using Gravitational Offset to Prepare Extraterrestrial Mobility Missions is Misleading},
  author = {Hu, Wei and Li, Pei and Rogg, Arno and Schepelmann, Alexander and Chandler, Samuel and Kamrin, Ken and Negrut, Dan},
  number = {20250001809},
  institution = {NASA},
  year = {2025},
  doi = {10.1002/rob.22597},
  abstract = {Recently, there has been a surge of international interest in extraterrestrial exploration targeting the Moon, Mars, the moons of Mars, and various asteroids. This contribution discusses how current state-of-the-art Earth-based testing for designing rovers and landers for these missions currently leads to overly optimistic conclusions about the behavior of these devices upon deployment on the targeted celestial bodies. The key misconception is that gravitational offset is necessary during the terramechanics testing of rover and lander prototypes on Earth. The body of evidence supporting our argument is tied to a small number of studies conducted during parabolic flights and insights derived from newly revised scaling laws. We argue that what has prevented the community from fully diagnosing the problem at hand is the absence of effective physics-based models capable of simulating terramechanics under low gravity conditions. We developed such a physics-based simulator and utilized it to gauge the mobility of early prototypes of the Volatiles Investigating Polar Exploration Rover (VIPER). This contribution discusses the results generated by this simulator, how they correlate with physical test results from the NASA-Glenn SLOPE lab, and the fallacy of the gravitational offset in rover and lander testing. The simulator, which is open-sourced and publicly available, supports trafficability analysis and facilitates principled studies into in-situ resource utilization activities like digging, bulldozing, and berming in low gravity environments.}
}
  47. Hurrell, J., Takehana, K., Tanaka, T., Uno, K., Busoud, A. K. and Yoshida, K. (2025). Traction Performance Evaluation for a Rashid-1 Rover Wheel . Space Science Reviews, 3. Source
    BibTeX
    @article{hurrell2025traction,
  title = {Traction Performance Evaluation for a Rashid-1 Rover Wheel},
  author = {Hurrell, James and Takehana, Keisuke and Tanaka, Tomomi and Uno, Kentaro and Busoud, Amna Khalifa and Yoshida, Kazuya},
  journal = {Space Science Reviews},
  volume = {221},
  number = {3},
  pages = {37},
  year = {2025},
  doi = {10.1007/s11214-025-01164-8},
  abstract = {Abstract Single-wheel experiments and discrete element method simulations of a micro-rover wheel modelled on the Rashid-1 rover designed for the Emirates lunar mission. The interaction of the wheel with Toyoura sand and FJS-1 lunar regolith simulant is studied. Slip conditions, traction coefficient and grouser pitch for single-wheel experiments are measured for a range of fixed slip values at the expected rover load of 24.5 N. The angle of repose is used to calibrate the simulation parameters with measured soil parameters. Single-wheel simulations are verified by comparison to experimental results. Lunar simulations can predict lunar gravity performance. Toyoura and FJS-1 results for traction coefficient and dynamic sinkage at 24.5 N in the 0–50% slip range show good agreement between experiment and simulation. 4.1 N lunar gravity matches the 24.5 N Earth gravity results for traction coefficient and tractive efficiency. There is a 1–2 mm difference in total sinkage. Tractive force and resistive torque reduce by 1/6 from Earth to lunar gravity for the same mass. The grouser pitch is unchanged with gravity variation. The angle of repose can independently determine parameters for use in single-wheel simulations. Experimental results validate the models for Toyoura sand and FJS-1. Wheel performance regarding traction coefficient and tractive efficiency under lunar gravity matches that under Earth gravity. Traction performance in tractive force and resistive torque is reduced by the ratio of Earth to lunar gravity, 1/6, for the same mass.}
}
  48. Kamohara, J., Ares, V., Hurrell, J., Takehana, K., Richard, A., Santra, S., Uno, K., Rohmer, E. and Yoshida, K. (2024). Modeling of Terrain Deformation by a Grouser Wheel for Lunar Rover Simulation . arXiv preprint. Source
    BibTeX
    @article{kamohara2024modeling,
  title = {Modeling of Terrain Deformation by a Grouser Wheel for Lunar Rover Simulation},
  author = {Kamohara, Junnosuke and Ares, Vinicius and Hurrell, James and Takehana, Keisuke and Richard, Antoine and Santra, Shreya and Uno, Kentaro and Rohmer, Eric and Yoshida, Kazuya},
  journal = {arXiv preprint},
  year = {2024},
  doi = {10.56884/fryx2uhe}
}
  49. Birmingham, W. (2024). Thermal Sensitivity Study of Lunar Terrain Vehicle Wheels . Thermal and Fluids Analysis Workshop. Source
    BibTeX
    @inproceedings{birmingham2024thermal,
  title = {Thermal Sensitivity Study of Lunar Terrain Vehicle Wheels},
  author = {Birmingham, William},
  booktitle = {Thermal and Fluids Analysis Workshop},
  organization = {Jacobs Space Exploration Group / NASA Marshall Space Flight Center},
  year = {2024},
  url = {https://ntrs.nasa.gov/citations/20240006096},
  abstract = {Since the early development of lunar vehicles for the Apollo program, designing a wheel capable of functioning in the harsh equatorial lunar environment was identified as a uniquely difficult engineering challenge. The Lunar Terrain Vehicle (LTV) must contend with many of the same challenges encountered during the Apollo missions, but with the addition of colder, more complex thermal environments at the lunar south pole and longer Artemis mission timelines. A full thermal assessment of LTV wheels should capture these and other details to assess heat leak through the wheels and extreme hot and cold temperatures. The goals of this study are to provide bounding lunar south pole thermal environments; to define sensitivity to interactions between the wheel and the lunar surface in different operation modes, such as parked and traversing; and to identify thermal performance concerns related to the use of shape memory alloys.}
}