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Space Robotics

Gearing and Actuators

Speed reducers and complete actuators selected by flown and qualified planetary and orbital robotics programs.

An actuator on a planetary surface has to deliver torque through a gear train that cannot be serviced, at temperatures that thicken wet lubricant, in a gas that is either near vacuum or a few torr of CO2 or N2. The Mars surface requirement set for the Sojourner and Polar Lander actuators was 1.0 kPa CO2, operation from -80 to -10 C and survival to -125 C, with vacuum during cruise [15]. The Moon removes the gas and drops the cold end to cryogenic temperatures: the COLDArm program set a goal of operation below -173 C with no heaters [16]. Each environment moves the limiting element. At Mars temperatures it is lubricant viscosity and brush life; at lunar night temperatures it is whether any wet lubricant remains usable.

Design space

Section titled “Design space”

Four families of drive appear in the corpus. Each is described here with its flight status.

Strain wave (harmonic) gearsets. Single-stage ratios of 50:1 to 161:1 are used on the flown parts below [2][4], and negligible backlash and a small envelope make them the default final stage of flown arms, gimbals and wheel drives. MER used 19 harmonic drive actuators in the antenna gimbal, wheel and steering drives, mast and instrument arm, and the development tests measured no-load running torque and efficiency from +25 to -70 C on non-flight engineering units [14]. The gimbal reduction was 5425:1, built from a 3-stage 81.37:1 planetary, a 1.333:1 spur stage and a 50:1 harmonic drive [14]. A strain wave drive flew in each Apollo LRV wheel [5]. Ratchet torque for the size 14 gimbal drive in its less stiff flight housing was estimated by finite element analysis at 77.4 N m, not measured [14]. The limits are in the next section.

Planetary and spur gear trains. These are the heritage choice where ratio, ruggedness and tolerance of shock matter more than zero backlash. The Shuttle arm used a planetary low speed stage and a spur high speed stage per joint [1]. The Mars mobility actuators use multistage planetary gearboxes, and a thermal vacuum characterization of the MSL and Mars 2020 wheel and steering actuator instrumented all four planetary stages; it was static and unpowered, so it constrains heat flow through the gear train and not friction or efficiency [18]. A 3 times multiplier on gear and bearing conductance in 6 torr gas relative to vacuum was the conservative lower bound the correlation supported [18]. Research gear trains are optimized for mass and efficiency: a JPL three-stage compound planetary for the EELS snake robot reached a computed worst-case forward efficiency of 78 percent and a best case of 87 percent at an assumed mesh friction coefficient of 0.16, with no measured efficiency [26]. Not flown in this form.

Brush and brushless motors with direct reduction. Brush DC motors flew on Sojourner because they need no commutation electronics. The Sojourner wheel motors ran 30 to 40 million revolutions to failure under load, while 29 of the same motor type retested at 30 V for the Mars Polar Lander arm averaged under 10 million revolutions, failing mostly by rotor shorting from commutator debris [15]. Brushless motors are the choice where life is counted in hundreds of millions of revolutions, and the Mars 2020 percussion drive uses a conventional brushless gearmotor so that ordinary avionics could run it across a range of speeds [13]. The Apollo LRV studies compared series, permanent magnet brushless and homopolar inductor motors, a choice made when the electronics parts count was the deciding factor [5].

Alternative materials and thermal actuators. Bulk metallic glass gears and paraffin actuators address the cold and the no-lubricant cases. The bulk metallic glass planetary gearmotor ran 10 million motor revolutions at ambient and 1.5 million at under 100 K to stall, both in vacuum at 1 N m, one article per condition [10]. The qualified COLDArm flight gearmotor demonstrated about 5.27 million motor revolutions of flight-like usage, 3 times COLDArm life, and its Hall sensors had to be changed because the original parts lost function below -130 C [10]. Ground testing only; the arm as tested used heritage commercial harmonic gears, and one of four actuators never warmed past -121 C and was not driven, attributed to harmonic gear lubricant [16]. A mission-program status deck reports the same arm at TRL 6 [17].

Lubrication, margins and qualification

Section titled “Lubrication, margins and qualification”

Lubricant choice sets cold performance more than gear geometry does. The Mars 2020 percussion bearings lost cold start capability at -70 C with a 10 to 15 percent grease fill [13], and the harmonic drive tests on MER ran Braycote 601EF down to -70 C with a caveat that the coldest torque trend may be biased low by self-heating [14]. Solid film data are specific to the test condition: a resin-bonded MoS2 film measured a friction coefficient of 0.045 in ultrahigh vacuum and 0.14 in humid air at about 20 percent relative humidity against 440C, on a pin-on-disk and not a gear [23]. Tribology test guidance notes that uncontrolled laboratory air can reverse the ranking of a graphite and an MoS2 film across seasons [22].

NASA-STD-5017B sets torque margin factors by evidence level: 3.00 on variable resisting torque from analysis, 2.50 from development or lot acceptance test at environmental extremes, and 2.00 from acceptance test of the flight article at expected extremes [21]. The superseded revision A used 3.0 for analysis and 2.0 for flight-like test, with no distinction by test temperature [20]. Neither revision reports measured hardware data.

Section titled “Related methods without flight use”

Several current papers are about gearing for ground or terrestrial robots and bear on design method and not on flight selection. Single-stage planetary actuators for legged robots were optimized for mass and efficiency over ratios 5 to 15, with the internal ring design lighter for ratios 5 to 7 and infeasible above 7; the model values were never tested on hardware [24]. A companion framework tested two 3D-printed actuators and measured efficiency of 60 to 80 percent against a modeled 96 percent [25]. A 3-DOF hopping leg used a 20:1 3K compound planetary knee with 320 N m peak torque, built for a laboratory and not qualified [28]. The EELS snake robot shape actuator pairs an outer-rotor brushless motor with a strain wave gear to reach 400 N m peak and 300 N m continuous in a 115 mm ball, with the peak rating tied to the gearset’s momentary peak torque [27]. A current-based torque estimate for a 160:1 harmonic drive joint exploited the direction dependence of efficiency and reached error standard deviations of about 1.6 to 1.9 N m unfiltered on the Ice Worm arm [29]. The Venus rover concept at 465 C and 92 atm replaces the electric drive with a purely mechanical one, as a pre-decisional study with no test result supporting a performance number [30]. The Mars Sample Return development arm testbed matches the flight arm joint gear ratios, 156:1 for the size 40 and 32 gearmotors and about 51:1 for size 17, and measured joint angular stiffness below the rated bearing pair stiffness, with no value reported [19].

The tradeoff that governs the class was measured for the Shuttle arm program and has not changed. A harmonic drive gives a high single-stage ratio, negligible backlash, arc-second accuracy and negligible tooth wear, with transmission life set by surface fatigue of the bearing inner race. Against that, it needs additional torque to overcome static friction, exhibits substantial wind-up with a nonlinear torsional spring rate at low torque, tends to cog at low speed, and carries a wave generator whose inertia may be too high for a fast servo. Efficiency falls from the usual 80 to 90 percent with a wet lubricant to as low as 50 percent with none [1]. The same program also found the internal ring gear output to be twice as stiff as an external ring and pinion with better static and dynamic friction, and recommends keeping output shaft power below half the rated motor peak power [1].

Gearsets and actuators selected and flown

Section titled “Gearsets and actuators selected and flown”
PartManufacturerUsed bySource
CSF 14-80LWHarmonic Driveipex (wheel actuators)[2][3]
CSF 20-160LWHarmonic Driveipex (bucket drum and arm actuators)[2]
SHG 32-160Harmonic Driverassor (shoulder actuator)[4]
80:1 harmonic drive transmissionUnited Shoe Machineryapollo-lrv[5]
Carousel drive, 2500:1Not namedcuriosity (SAM)[6]
Elevator drive, leadscrewNot namedcuriosity (SAM)[6]
FHAC-mini motor-gearbox unitHarmonic Drivejustin (Rollin’ Justin mobile base)[7]

Ratings and qualification results

Section titled “Ratings and qualification results”
  • CSF 14-80LW, Harmonic Drive: a strain wave gearset, 80:1, cup type [2]. Ratings: Sizing load cases run to 7.45 N m at the gearbox output. Output bearings sized to fit over the flex cup, input bearings stacked close together and preloaded with a wave spring sized so the wave generator axial force could not overcome it [2][3]. Qualification: Ran 6,547,036 input revolutions in the 3-sigma accelerated life test against a mission requirement of 5.7 million, then failed. Root cause was the wave generator moving axially into the flex cup despite the wave spring, breaking the motor rotor bearing springs. The future work identified is a change to the grease application on the harmonic drive to improve lubrication between the flex cup and the wave generator band [2].
  • CSF 20-160LW, Harmonic Drive: a strain wave gearset, 160:1, cup type [2]. Ratings: Driven by a ThinGap LSI 75-30 motor. The arm actuator adds a power-off brake to stop back-driving with power removed; the bucket drum actuator adds an internal shaft carrying torque through to a second drum [2]. Qualification: Same four-stage KSC qualification campaign as the wheel actuator, run at 2-sigma rather than 3-sigma load. Results not published [2].
  • SHG 32-160, Harmonic Drive: a strain wave gearset, 161:1 [4]. Ratings: Direct-driven by a Parker Bayside K089050 frameless motor, with a THK cross roller bearing carrying radial, axial and moment loads in one element [4]. Qualification: Selected against the requirement to lift and lower the arm with a bucket drum full of regolith at the required output speed. The paper reports the sizing basis and the fabrication lessons, not a test result [4].
  • 80:1 harmonic drive transmission, United Shoe Machinery: a strain wave gearset in a hermetically sealed wheel drive unit [5]. Ratings: One per wheel. Motor and wave generator sealed together in dry nitrogen at about 5.17 N/cm2 and lubricated with Krytox 143AZ oil [5]. Qualification: Flown on Apollo 15, 16 and 17. Selected as baseline over an open-to-vacuum 80:1 planetary spur alternate from General Electric, which the contract required be carried in parallel until the sealed unit was shown to work under simulated lunar conditions [5].
  • Carousel drive, 2500:1, vendor not named, built for the SAM Sample Manipulation System: a 25:1 planetary gearbox and a 100:1 harmonic drive behind a Hall-commutated brushless DC motor [6]. Ratings: Overall 2500:1 with 30,000 encoder counts per revolution. Positions both the sample carousel and the sample cup elevator from one actuator, the carousel being locked to ground by a spring-energized latch while the elevator is moved. Qualification: The whole Sample Manipulation System draws under 5 W continuous and 10 W peak and recovers from unexpected power loss through its feedback devices and control architecture [6]. In flight, Teflon and molybdenum disulfide lubricant particles from the sample chain were found to pass the 150 micron sieve [6].
  • Elevator drive, leadscrew, vendor not named, built for the SAM Sample Manipulation System: a compliant linear actuator with a resettable launch lock, driven through an 80:1 planetary gearbox, a 2.4:1 spur pair and 5/16-12 leadscrews [6]. Ratings: Raises and lowers sample cups, supplies the force to seal cups into the pyrolysis ovens, and provides the launch restraint for the elevator mechanism. Qualification: Flown since August 2012 as part of the mechanism above [6].
  • FHAC-mini motor-gearbox unit, Harmonic Drive: an integrated brushless DC motor with 100:1 harmonic drive [7]. Ratings: Used as the steering drive of the wheeled base [7]. Qualification: Ground system. The paper documents the selection and the 100:1 reduction; no space qualification is claimed [7].

Where strain wave gearsets fail

Section titled “Where strain wave gearsets fail”

A wave spring sized against the wave generator axial force did not hold it. The IPEx wheel actuator input bearings were stacked close together and preloaded with a wave spring whose force was calculated so that the axial force generated by the Harmonic Drive CSF 14-80LW wave generator could not overcome it, keeping the motor rotor and wave generator axially positioned [3]. In the 3-sigma accelerated life test the wave generator moved axially into the flex cup regardless, breaking the springs on the motor rotor bearings and repeatedly tripping the motor current limit [2]. The actuator still reached 6,547,036 input revolutions against a mission requirement of 5,700,000 before the test was stopped, over multiple inspections and disassemblies. The future work identified is not a stiffer spring but a change to the grease application on the harmonic drive, to improve lubrication between the flex cup and the wave generator band [2].

Both harmonic drive life limits recorded above sit at the wave generator, not the gear teeth. The Shuttle arm characterization independently places transmission life at the surface fatigue life of the bearing inner race rather than at tooth wear, and records that wave generator inertia may be too high for a fast servo [1]. Sizing a strain wave gearset against output torque alone addresses neither the IPEx failure nor the life limit the earlier program measured.

Gearsets, springs and actuators with a published test result

Section titled “Gearsets, springs and actuators with a published test result”

Seven further mechanisms carry a measured result and no flight heritage on a planetary robot. Two of them are cases where the article measured far from what the design calculation predicted [8][11].

PartManufacturerUsed bySource
Size 40 S-tooth harmonic driveHarmonic DriveMars rover actuator study[8]
EH-3525 paraffin actuatorSierra Nevadadsoc docking mechanism[9]
DM105 docking mechanismNot nameddsoc engineering model[9]
Cu43Zr43Al7Be7 spur gearsNot namedKSC dynamometer article[10]
L-PBF Ti-6Al-4V spiral springNot namedJPL torsion stand[11]
Suspension actuator, 360 mm strokeNot namedviper[12]
Percussion mechanismNot namedperseverance (coring drill)[13]

Ratings and qualification results

Section titled “Ratings and qualification results”
  • Size 40 S-tooth harmonic drive, Harmonic Drive [8]. An alternative tooth form in the standard size 40 envelope. Ratings: 3.0 kg unlightened, the same as the standard size 40 and half the size 50 [8]. Qualification: ratchet torque limit measured on a dynamometer at 1580 N m, against 745 N m for the standard size 40 tooth form and 1410 N m for a standard size 50, with a momentary peak limit of 1370 N m [8]. The tooth form more than doubles the ratchet limit at constant mass, which is a gain the standard catalog reaches only by going up a frame size and doubling the mass.
  • EH-3525 paraffin actuator, Sierra Nevada. High-output thermal actuator in the Deep Space Optical Communications docking mechanism. Ratings: paraffin melting range 86 to 89 C, a vendor property not measured in the work that uses it [9]. Qualification: the vendor’s stated temperature limit before seal rupture is 130 C, corresponding to a 70 lbf cut-off load at the actuator shaft, and was adopted as the design limit. A thermal model run peaked at 145 C with no damage found afterwards [9], so the limit was exceeded in analysis and not in test.
  • DM105 docking mechanism, vendor not named, built for the same instrument. Ratings: one engineering unit, primary heater carrying 95 percent of the cycles at 27.4 to 33.6 V [9]. Qualification: 420 dock and undock cycles accumulated in thermal vacuum against a requirement of more than 100, of which 41 were 2 to 8 hour holds and the rest 25 minute holds, split 47 percent at room temperature and 26.5 percent each at the hot and cold protoflight cases [9]. Undocked hold time reached 335 hours against a 76 to 304 hour requirement, with no dithering in any hold and no reported performance degradation.
  • Cu43Zr43Al7Be7 spur gears, vendor not named. Bulk metallic glass gearing. Ratings: compared against C300 maraging steel [10]. Qualification: 65 percent less unlubricated wear than the steel, reported as heritage from earlier alloy development with the conditions and test duration not given [10]. The comparison is by mass loss between materials of different density.
  • L-PBF Ti-6Al-4V spiral spring, vendor not named. Laser powder bed fusion printed spiral spring for a camera cover hinge, three designs at four specimens each on an EOS M290 with vendor stress relief only and an as-printed surface [11]. Ratings: design target 4.00 N mm/deg on design 17186799-1, against 4.60 to 4.69 calculated from the as-printed dimensions. Qualification: measured torsional stiffness averaged 0.606 N mm/deg on that design, 0.13 of the stiffness calculated from as-printed dimensions and about 0.155 of the design target, with quoted errors of 81 to 91 percent [11]. Stiffness was also direction dependent, higher winding inward than opening at p at or below 0.002, attributed to inter-winding contact and friction, and out-of-plane twisting of the cross-section was seen in most tests. Multi-jet fusion PA12 nylon springs of the same geometry measured within 9.8 to 12.9 percent of the spring-equation prediction, on one specimen per design read by hand with a protractor [11].
  • Suspension actuator, 360 mm stroke, vendor not named, in the VIPER wheel module [12]. Ratings: a four-bar linkage giving quasilinear output from a rotary actuator over a 360 mm stroke [12]. Qualification: no life or environmental result is published. The torque transducer in the same module is on Sensors and IMUs.
  • Percussion mechanism, vendor not named, in the Perseverance coring drill. Ratings: crank pin plain bearing designed to keep contact pressure below 3.45 MPa at the highest percussion output, reached by growing the shaft from 3.175 to 4.7625 mm and the 440C Grade 10 roller ball from 6.35 to 9.525 mm [13]. The shaft was nitrided to a 75 micrometer case at 65 to 68 HRC against a 58 HRC minimum ball, with 7.6 micrometer diametral clearance and 0.2 micrometer surface finishes, after early prototypes wore out roller bores and broke crank pins. Qualification: grease fill was cut from 10 to 15 percent of free volume to about 3 percent because at the higher fill the mechanism could not reliably start at the -70 C qualification minimum and the actuator stalled at its 10 A current limit, equal to 0.75 N m at the output shaft [13]. Braycote 600EF viscosity rises very nonlinearly between -50 and -70 C, so the cold start and not the running load set the fill.

Two of the seven entries above are a measured stiffness or torque that the design calculation did not predict, in opposite directions: the printed spring came out at an eighth of its calculated stiffness [11] and the S-tooth gearset at over twice the ratchet torque of the catalog form it replaces [8].

What is not established

Section titled “What is not established”

No source here reports gear or actuator performance measured on a planetary surface; the MER, Mars 2020 and COLDArm life and efficiency data are ground tests, mostly one article per condition [14][10][16]. The Shuttle harmonic drive and ring gear figures come from unpublished testing cited by reference number, without conditions or sample counts [1]. No cryogenic result covers a full strain wave drive built from bulk metallic glass flown on a lander. Efficiency of the research planetary gearboxes is modeled, and where tested it fell below the model [25]. Lubricant life models are not validated to mission duration: the Mars 2020 grease reduction is supported by life test duration only [13].

References

  1. Chun, W. and Brunson, P. (1987). Actuators for a Space Manipulator . NASA, 19890000730. Source
    BibTeX
    @techreport{chun1987actuators,
  title = {Actuators for a Space Manipulator},
  author = {Chun, W. and Brunson, P.},
  number = {19890000730},
  institution = {NASA},
  year = {1987},
  url = {https://ntrs.nasa.gov/citations/19890000730},
  abstract = {The robotic manipulator can be decomposed into distinct subsytems. One particular area of interest of mechanical subsystems is electromechanical actuators (or drives). A drive is defined as a motor with an appropriate transmission. An overview is given of existing, as well as state-of-the-art drive systems. The scope is limited to space applications. A design philosophy and adequate requirements are the initial steps in designing a space-qualified actuator. The focus is on the d-c motor in conjunction with several types of transmissions (harmonic, tendon, traction, and gear systems). The various transmissions will be evaluated and key performance parameters will be addressed in detail. Included in the assessment is a shuttle RMS joint and a MSFC drive of the Prototype Manipulator Arm. Compound joints are also investigated. Space imposes a set of requirements for designing a high-performance drive assembly. Its inaccessibility and cryogenic conditions warrant special considerations. Some guidelines concerning these conditions are present. The goal is to gain a better understanding in designing a space actuator.}
}
  2. Schuler, J. M., Smith, J. D., Nick, A. J., Buckles, B. C., Dyas, J. E., Ortega, V. V., Cloud, J. M., Dokos, A. G., Zhang, E. L., Wang, J. J., Baron, M. A., Muller, T. J., Clark, C. J. and Howe, M. W. (2024). ISRU Pilot Excavator (IPEx) Technology Readiness Level 5 Design Overview . AIAA AVIATION Forum and ASCEND, 20240008162. Source
    BibTeX
    @inproceedings{schuler2024isru,
  title = {ISRU Pilot Excavator (IPEx) Technology Readiness Level 5 Design Overview},
  author = {Schuler, Jason M. and Smith, Jonathan D. and Nick, Andrew J. and Buckles, Bradley C. and Dyas, Jeffrey E. and Ortega, Victoria V. and Cloud, Joseph M. and Dokos, Adam G. and Zhang, Elizabeth L. and Wang, Jerry J. and Baron, Michael A. and Muller, Thomas J. and Clark, Casey J. and Howe, Musashi W.},
  booktitle = {AIAA AVIATION Forum and ASCEND},
  number = {20240008162},
  institution = {NASA},
  year = {2024},
  doi = {10.2514/6.2024-4890},
  abstract = {This paper details the mechanical and mechatronic design of the Technology Readiness Level (TRL)-5 In-Situ Resource Utilization (ISRU) Pilot Excavator (IPEx). IPEx is a robotic excavator designed for a technology demonstration of regolith mining in the lunar south pole region. The novel design uses pairs of counter-acting excavation tools called bucket drums, that dig at the same time in opposing directions to reduce the reaction force needed, thereby enabling mining with a small, low-mass, robotic system. IPEx builds on the prior work of the Regolith Advanced Surface Systems Operations Robot (RASSOR), which is the TRL-4 implementation of this concept. The TRL-5 IPEx subsystems that are discussed in this paper include: Regolith Delivery Subsystem (RDS), Mobility Subsystem (MS), Cameras and Dust Mitigation Subsystem (CDMS), and Thermal Control Subsystem (TCS). Each subsystem is described in detail with rationale for design selections. Dust tolerance is a key feature for IPEx, and this paper details a thermal control system with an actuated radiator cover and phase change material as well as camera modules with removable electrodynamic dust shields (EDS). Additional components such as actuators, wheels, and bucket drums are discussed in detail. Due to their complexity, the avionics and software subsystems will be discussed in a separate publication.}
}
  3. Clark, C. J., Smith, J. D., Nick, A. J., Ortega, V. V., Schuler, J. M., Dyas, J. E. and Lahl, J. (2025). Design and Testing of TRL5 IPEx Actuators . IEEE Aerospace Conference, 20250000003. Source
    BibTeX
    @inproceedings{clark2025design,
  title = {Design and Testing of TRL5 IPEx Actuators},
  author = {Clark, Casey J. and Smith, Jonathan Drew and Nick, Andrew J. and Ortega, Victoria V. and Schuler, Jason M. and Dyas, Jeffrey E. and Lahl, John},
  booktitle = {IEEE Aerospace Conference},
  number = {20250000003},
  institution = {NASA},
  address = {Big Sky, MT},
  year = {2025},
  url = {https://ntrs.nasa.gov/citations/20250000003},
  abstract = {NASA is advancing In-Situ Resource Utilization (ISRU) by focusing on missions aimed at establishing sustainable infrastructure on the Moon and Mars. On the Moon, regolith serves as the most abundant resource. To support ISRU objectives, a 30-kg-class robot called ISRU Pilot Excavator (IPEx) is being developed to excavate 10,000 kg of lunar regolith during a future technology demonstration mission. IPEx uses novel excavation tools, called bucket drums, which are hollow cylinders with scoops staggered around the outside. Regolith is collected with the scoops and flows into the drum where it is captured by an internal baffle system. The excavator can then transport the regolith in the drum and reverse the direction of the drum rotation to dispense the regolith out. IPEx uses two sets of bucket drums that dig simultaneously in opposing directions and results in counteracting excavation forces. This combination of bucket drum excavation tools and counteracting excavation forces enables low mass robotic excavators to effectively dig in reduced gravity environments. This is a significant departure from terrestrial excavators that rely on high mass to produce tractive forces to counteract the forces of excavation.

IPEx is made up of several custom actuators that all need to be verified for their intended application. This paper focuses on the initial design, testing and modifications of three actuators: the mobility actuator, the shoulder actuator, and the excavation actuator.

Each actuator was tested under four separate test profiles: ambient motor characterization, hot and cold motor characterization, accelerated life test (ALT), and concept of operations (ConOps) test. The motor characterization tests enabled derivation of torque equations for each actuator to estimate output torque without implementing sensors. The accelerated life tests were successful for each actuator and verified the motors’ ability to survive the mission. For the ConOps test, only the bucket drum actuator performed a complete ConOps without the need to restart the test. Overall, the first series of testing resulted in various failure modes and minor design alterations for each actuator. The test results, failure modes, and design alterations are highlighted within this paper. This paper focuses on discussing the mobility, excavation, and shoulder actuator design, testing principles, and results that qualified it as a TRL 5 system.}
}
  4. Mueller, R. P., Smith, J. D., Schuler, J. M., Nick, A. J., Gelino, N. J., Leucht, K. W., Townsend, I. I. and Dokos, A. G. (2016). Design of an Excavation Robot: Regolith Advanced Surface Systems Operations Robot (RASSOR) 2.0 . ASCE Earth and Space Conference, 20210011366. Source
    BibTeX
    @inproceedings{mueller2016design,
  title = {Design of an Excavation Robot: Regolith Advanced Surface Systems Operations Robot (RASSOR) 2.0},
  author = {Mueller, Robert P. and Smith, Jonathan D. and Schuler, Jason M. and Nick, Andrew J. and Gelino, Nathan J. and Leucht, Kurt W. and Townsend, Ivan I. and Dokos, Adam G.},
  booktitle = {ASCE Earth and Space Conference},
  number = {20210011366},
  pages = {163-174},
  institution = {NASA},
  year = {2016},
  doi = {10.1061/9780784479971.018},
  abstract = {To continue on a sustainable and flexible path, NASA needs to address the challenge of collecting and moving large amounts of regolith at the destination. Acquiring the water resources on Mars will require mining significant quantities of regolith, and this is not possible with the state-of-the-art low mass excavation systems. Low gravity environments (Mars = 3/8G) and launch mass restrictions limit the traction and the resulting reaction force of the vehicle, making current terrestrial techniques impractical. This project addressed this challenge by developing a completely new technology that can mine large quantities of regolith on Mars. Recent measurements by the “Curiosity” rover on Mars have found that the regolith contains ~2% water by weight globally, ~4% in Jezero Crater (Human Architecture Team’s reference landing site), and much more at the poles. RASSOR 2.0 is a planetary excavator, which has a mass of 66 kg, with a 0.38 kg vehicle mass per kilogram, per hour of excavation rate and power usage of 4 W per kg of regolith excavation rate. A single RASSOR 2.0 can excavate a minimum of 2.7 metric tons of regolith per day. This is accomplished by using counteracting excavation forces on two opposing digging implements called bucket drums and an autonomous mining control system. This work has addressed several major research areas outlined in the NASA Technology Area (TA) 04 Robotics and Autonomous Systems and TA 07 Human Destination Systems roadmaps. This project started at Technology Readiness Level (TRL) 4 as a low fidelity “proof of concept” prototype which has successfully demonstrated basic regolith simulant excavation functionality in a lab-scale gravity off load test. The foundational technology described here was awarded US patent number: US 9027265 for a “Zero horizontal reaction force excavator” on May 12, 2015.}
}
  5. Jones, C. S. J. and Nola, F. J. (1971). Mobility systems activity for lunar rovers at MSFC . NASA, NASA-TM-. Source
    BibTeX
    @techreport{jones1971mobility,
  title = {Mobility systems activity for lunar rovers at MSFC},
  author = {Jones, C. S., Jr. and Nola, F. J.},
  number = {NASA-TM-},
  institution = {NASA},
  year = {1971},
  url = {https://ntrs.nasa.gov/citations/19720004516},
  abstract = {The Apollo Lunar Roving Vehicle (LRV) mobility system is described. Special emphasis is given to the redundancy aspects and to the selection of the drive motors. A summary chart of the performance on the lunar surface during the Apollo 15 flight is included. An appendix gives details on some development work on high efficiency drive systems and compares these systems to the selected system.}
}
  6. Mahaffy, P. R., Webster, C. R., Cabane, M., Conrad, P. G., Coll, P., Atreya, S. K., Arvey, R., Barciniak, M., Benna, M., Bleacher, L., Brinckerhoff, W. B., Eigenbrode, J. L., Carignan, D., Cascia, M., Chalmers, R. A., Dworkin, J. P., Errigo, T., Everson, P., Franz, H., Farley, R., Feng, S., Frazier, G., Freissinet, C., Glavin, D. P., Harpold, D. N., Hawk, D., Holmes, V., Johnson, C. S., Jones, A., Jordan, P., Kellogg, J., Lewis, J., Lyness, E., Malespin, C. A., Martin, D. K., Maurer, J., McAdam, A. C., McLennan, D., Nolan, T. J., Noriega, M., Pavlov, A. A., Prats, B., Raaen, E., Sheinman, O., Sheppard, D., Smith, J., Stern, J. C., Tan, F., Trainer, M., Ming, D. W., Morris, R. V., Jones, J., Gundersen, C., Steele, A., Wray, J., Botta, O., Leshin, L. A., Owen, T., Battel, S., Jakosky, B. M., Manning, H., Squyres, S., Navarro-González, R., McKay, C. P., Raulin, F., Sternberg, R., Buch, A., Sorensen, P., Kline-Schoder, R., Coscia, D., Szopa, C., Teinturier, S., Baffes, C., Feldman, J., Flesch, G., Forouhar, S., Garcia, R., Keymeulen, D., Woodward, S., Block, B. P., Arnett, K., Miller, R., Edmonson, C., Gorevan, S. and Mumm, E. (2012). The Sample Analysis at Mars Investigation and Instrument Suite . Space Science Reviews. Source
    BibTeX
    @article{mahaffy2012sample,
  title = {The Sample Analysis at Mars Investigation and Instrument Suite},
  author = {Mahaffy, Paul R. and Webster, Christopher R. and Cabane, Michel and Conrad, Pamela G. and Coll, Patrice and Atreya, Sushil K. and Arvey, Robert and Barciniak, Michael and Benna, Mehdi and Bleacher, Lora and Brinckerhoff, William B. and Eigenbrode, Jennifer L. and Carignan, Daniel and Cascia, Mark and Chalmers, Robert A. and Dworkin, Jason P. and Errigo, Therese and Everson, Paula and Franz, Heather and Farley, Rodger and Feng, Steven and Frazier, Gregory and Freissinet, Caroline and Glavin, Daniel P. and Harpold, Daniel N. and Hawk, Douglas and Holmes, Vincent and Johnson, Christopher S. and Jones, Andrea and Jordan, Patrick and Kellogg, James and Lewis, Jesse and Lyness, Eric and Malespin, Charles A. and Martin, David K. and Maurer, John and McAdam, Amy C. and McLennan, Douglas and Nolan, Thomas J. and Noriega, Marvin and Pavlov, Alexander A. and Prats, Benito and Raaen, Eric and Sheinman, Oren and Sheppard, David and Smith, James and Stern, Jennifer C. and Tan, Florence and Trainer, Melissa and Ming, Douglas W. and Morris, Richard V. and Jones, John and Gundersen, Cindy and Steele, Andrew and Wray, James and Botta, Oliver and Leshin, Laurie A. and Owen, Tobias and Battel, Steve and Jakosky, Bruce M. and Manning, Heidi and Squyres, Steven and Navarro-González, Rafael and McKay, Christopher P. and Raulin, Francois and Sternberg, Robert and Buch, Arnaud and Sorensen, Paul and Kline-Schoder, Robert and Coscia, David and Szopa, Cyril and Teinturier, Samuel and Baffes, Curt and Feldman, Jason and Flesch, Greg and Forouhar, Siamak and Garcia, Ray and Keymeulen, Didier and Woodward, Steve and Block, Bruce P. and Arnett, Ken and Miller, Ryan and Edmonson, Charles and Gorevan, Stephen and Mumm, Erik},
  journal = {Space Science Reviews},
  volume = {170},
  pages = {401--478},
  year = {2012},
  doi = {10.1007/978-1-4614-6339-9_13},
  abstract = {The Sample Analysis at Mars (SAM) investigation of the Mars Science Laboratory (MSL) addresses the chemical and isotopic composition of the atmosphere and volatiles extracted from solid samples. The SAM investigation is designed to contribute substantially to the mission goal of quantitatively assessing the habitability of Mars as an essential step in the search for past or present life on Mars. SAM is a 40 kg instrument suite located in the interior of MSL’s Curiosity rover. The SAM instruments are a quadrupole mass spectrometer, a tunable laser spectrometer, and a 6-column gas chromatograph all coupled through solid and gas processing systems to provide complementary information on the same samples. The SAM suite is able to measure a suite of light isotopes and to analyze volatiles directly from the atmosphere or thermally released from solid samples. In addition to measurements of simple inorganic compounds and noble gases SAM will conduct a sensitive search for organic compounds with either thermal or chemical extraction from sieved samples delivered by the sample processing system on the Curiosity rover’s robotic arm.}
}
  7. Fuchs, M., Borst, C., Robuffo Giordano, P., Baumann, A., Kraemer, E., Langwald, J., Gruber, R., Seitz, N., Plank, G., Kunze, K., Burger, R., Schmidt, F., Wimboeck, T. and Hirzinger, G. (2009). Rollin' Justin: Design Considerations and Realization of a Mobile Platform for a Humanoid Upper Body . IEEE International Conference on Robotics and Automation. Source
    BibTeX
    @inproceedings{fuchs2009rollin,
  title = {Rollin' Justin: Design Considerations and Realization of a Mobile Platform for a Humanoid Upper Body},
  author = {Fuchs, M. and Borst, Ch. and Robuffo Giordano, P. and Baumann, A. and Kraemer, E. and Langwald, J. and Gruber, Robin and Seitz, Nikolaus and Plank, Georg and Kunze, K. and Burger, R. and Schmidt, F. and Wimboeck, T. and Hirzinger, G.},
  booktitle = {IEEE International Conference on Robotics and Automation},
  pages = {4131-4137},
  year = {2009},
  doi = {10.1109/robot.2009.5152464},
  abstract = {Research on humanoid robots for use in servicing tasks, e.g. fetching and delivery, attracts steadily more interest. With Rollin' Justin a mobile robotic system and research platform is presented that allows the implementation and demonstration of sophisticated control algorithms and dexterous manipulation. Important problems of service robotics such as mobile manipulation and strategies for using the increased workspace and redundancy in manipulation task can be studied in detail. This paper gives an overview of the design considerations for a mobile platform and their realizations to transform the formerly table-mounted humanoid upper body system Justin into Rollin' Justin, a fully self-sustaining mobile research platform.}
}
  8. Gillis-Smith, G. R. (1996). Mars Pathfinder Lander Deployment Mechanisms . JPL Open Repository. Source
    BibTeX
    @inproceedings{gillissmith1996mars,
  title = {Mars Pathfinder Lander Deployment Mechanisms},
  author = {Gillis-Smith, Greg R.},
  publisher = {JPL Open Repository},
  year = {1996},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/24167}
}
  9. Rosas, R., MacNeal, K., Wilkerson, M., Agnes, G., Johnson, J., Na-Nakornpanom, A. and Hernandez, B. (2023). Thermal Control Design for Deep Space Optical Communication (DSOC) Docking Mechanism High-Output Paraffin Actuator . International Conference on Environmental Systems. Source
    BibTeX
    @inproceedings{rosas2023thermal,
  title = {Thermal Control Design for Deep Space Optical Communication (DSOC) Docking Mechanism High-Output Paraffin Actuator},
  author = {Rosas, Rogelio and MacNeal, Kristen and Wilkerson, Marcus and Agnes, Gregory and Johnson, Joel and Na-Nakornpanom, Arthur and Hernandez, Brenda},
  booktitle = {International Conference on Environmental Systems},
  publisher = {JPL Open Repository},
  year = {2023},
  doi = {10.48577/jpl.wqapop},
  abstract = {Deep Space Optical Communication (DSOC) is a technology demonstration laser communication payload riding on the Psyche spacecraft that will demonstrate data transmission via laser up to 2.76 AU (probe to sun). The payload achieves fine acquisition and tracking control by utilizing Lorentz force actuators to perform dual functions: mechanical isolation from the bus to provide a stable floating platform for the optical assembly, and to perform fine-grain pointing and tracking of the optical uplink receiver. To satisfy a Psyche requirement, during DSOC off periods, the floating platform is mechanically docked to the stationary side through the use of a pair of Docking Mechanisms (DMs). During an optical pass the optical platform has to be undocked by the DMs which each utilize a High-Output Paraffin (HOP) actuator to perform the undocking function. The DMs need to be in the undocked phase for up to 8 hours without any interruption or dithering of the HOP pin. Dithering has to be prevented because this could cause disruptions to the pointing of the optical assembly. Spacecraft bus voltage is also static so there inability of changing the power output to the HOP heater, which is critical due to strict paraffin temperature limits, thus, a pulse-width modulation (PWM) heating scheme was developed to achieve the desired power output. This PWM was then adapted and implemented in Psyche Flight Software (FSW). The flight unit DMs were tested successfully meeting all Verification & Validation requirements using this method for all temperature and voltage ranges. The DMs have been proven to work for 8+ hours in thermal vacuum, which is required for compliance of DSOC Project Level 1 requirements. This paper describes the development of the algorithm from inception to the final Psyche flight software implementation.}
}
  10. Kennett, A. and Dillon, R. `. (2024). Development of a Bulk Metallic Glass Planetary Gearmotor for Unheated Actuation in Cryogenic Environments . International Conference on Advanced Robotics. Source
    BibTeX
    @inproceedings{kennett2024development,
  title = {Development of a Bulk Metallic Glass Planetary Gearmotor for Unheated Actuation in Cryogenic Environments},
  author = {Kennett, Andrew and Dillon, Robert ``Peter''},
  booktitle = {International Conference on Advanced Robotics},
  publisher = {JPL Open Repository},
  year = {2024},
  doi = {10.48577/jpl.bhhjka},
  abstract = {Bulk metallic glasses (BMGs), a class of amorphous metal alloys, were selected for development of gears for unheated actuators that can be used in cryogenic environments such as Mars, the Moon, and outer planetary icy bodies (e.g., Enceladus and Europa). Specifically, an alloy of Cu43Zr43Al7Be7 was used to successfully develop a BMG planetary gearbox and prototype and flight gearmotors for operation at ≤-180 C. In additional to lessons learned from all phases of development, components and configurations, testing (including shock and vibration), and qualification for use in the Cold Operable Lunar Deployable (robotic) Arm (COLDArm) system are presented.}
}
  11. Roman, M., Cheng, A. and Gebara, C. (2024). ADDITIVE MANUFACTURING OF A DEPLOYABLE MONOLITHIC CAMERA COVER FOR PLANETARY EXPLORATION . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{roman2024additive,
  title = {ADDITIVE MANUFACTURING OF A DEPLOYABLE MONOLITHIC CAMERA COVER FOR PLANETARY EXPLORATION},
  author = {Roman, Maya and Cheng, Adrian and Gebara, Christine},
  booktitle = {IEEE Aerospace Conference},
  publisher = {JPL Open Repository},
  year = {2024},
  doi = {10.48577/jpl.72856g},
  abstract = {Camera covers are mechanisms commonly used to protect optical instruments during the launch and landing of a spacecraft. The mechanisms have two basic functions: protect optics from foreign objects and debris while stowed and move out of the camera’s field of view when deployed. Mechanisms of this sort are easily over engineered, with the final assembly consisting of dozens of piece-parts. This project presents a design that takes advantage of additive manufacturing to combine components, including flexures that deploy the cover. The proposed design would decrease part count and cost while maintaining the function and reliability of traditional camera cover mechanisms. As part of the development of the design, the performance of printed nylon and Ti-6Al-4V springs were tested and compared to analytical values.}
}
  12. Rezich, E., Bickel, V. T., Francis, P. L., Rogg, A., Tardy, A., Creager, C., Oravec, H. A., Schepelmann, A., Ennico-Smith, K., Deutsch, A. and Hirabayashi, M. (2025). Investigating the Geotechnical Properties of the Lunar South Pole with NASA VIPER's Mobility System . The Planetary Science Journal, 7. Source
    BibTeX
    @article{rezich2025investigating,
  title = {Investigating the Geotechnical Properties of the Lunar South Pole with NASA VIPER's Mobility System},
  author = {Rezich, Erin and Bickel, Valentin T. and Francis, Parker L. and Rogg, Arno and Tardy, Antoine and Creager, Colin and Oravec, Heather A. and Schepelmann, Alexander and Ennico-Smith, Kimberly and Deutsch, Ariel and Hirabayashi, Masatoshi},
  journal = {The Planetary Science Journal},
  volume = {6},
  number = {7},
  pages = {169},
  year = {2025},
  doi = {10.3847/psj/add13f},
  abstract = {Abstract The NASA Volatiles Investigating Polar Exploration Rover (VIPER) is capable of assessing the geotechnical properties of the lunar south pole’s terrain, specifically as they pertain to terramechanics or the wheel–terrain interaction, combining the rover’s mobility system and science payloads. This paper focuses on one key aspect of VIPER’s mission: the quantitative evaluation of geotechnical parameters via tractive performance by analyzing wheel and wheel–regolith interaction dynamics. As VIPER navigates the largely uncharted terrain of the Moon’s south pole, sophisticated onboard instrumentation will monitor and record detailed interactions between the rover’s wheels, chassis, and the lunar surface. These measurements will capture critical data such as wheel slip and sinkage, offering insights into the mechanical behavior of the soil under actual lunar conditions. The findings from VIPER are expected to provide a foundational understanding of the lunar south pole’s regolith mechanics, directly informing the design and navigation strategies of future lunar missions, including the deployment of more advanced rovers and crewed vehicles. By integrating lunar surface observations with the rover’s kinematic model and understood terrestrial mobility performance, the study aims to enhance predictive accuracy regarding rover tractive performance over sloped, level, and potentially volatile-rich terrain. Ground truth geotechnical assessments and proceeding mobility characterization work will serve as a cornerstone for verifying and improving both terrestrial test approaches and simulation models that underpin mission planning and risk management for subsequent explorations.}
}
  13. Chrystal, K. (2020). Percussion Mechanism for the Mars2020 Coring Drill . Aerospace Mechanisms Symposium. Source
    BibTeX
    @inproceedings{chrystal2020percussion,
  title = {Percussion Mechanism for the Mars2020 Coring Drill},
  author = {Chrystal, Kyle},
  booktitle = {Aerospace Mechanisms Symposium},
  publisher = {JPL Open Repository},
  year = {2020},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/52361}
}
  14. Krishnan, S. and Voorhees, C. (2001). The use of harmonic drives on NASA's Mars Exploration Rover . Harmonic Drive International Symposium. Source
    BibTeX
    @inproceedings{krishnan2001use,
  title = {The use of harmonic drives on NASA's Mars Exploration Rover},
  author = {Krishnan, S. and Voorhees, C.},
  booktitle = {Harmonic Drive International Symposium},
  year = {2001},
  url = {https://ntrs.nasa.gov/citations/20060031884},
  abstract = {The Mars Exploration Rover (MER) mission will send two 185 kg rovers to Mars in 2003 to continue the scientific community's search for evidence of past water on Mars.  These twin  robotic vehicles will carry harmonic drives and their performance will be characterized at various temperatures, speeds and loads.}
}
  15. Reid, L. K., Braun, D. F. and Noon, D. E. (1999). Robotic Arm and Rover Actuator Systems for Mars Exploration . Aerospace Mechanisms Symposium. Source
    BibTeX
    @inproceedings{reid1999robotic,
  title = {Robotic Arm and Rover Actuator Systems for Mars Exploration},
  author = {Reid, Lisa K. and Braun, David F. and Noon, Don E.},
  booktitle = {Aerospace Mechanisms Symposium},
  organization = {Jet Propulsion Laboratory, California Institute of Technology},
  year = {1999},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/18020}
}
  16. Newill-Smith, D., Shatts, J., Dillon, R. `., Karras, J., Brinkman, A., Backus, S., Umali, A., McCormick, R., Fradet, L., Laramee, J., Levanas, G. and Fleischner, R. (2023). Cold Operable Lunar Deployable Arm (COLDArm) System Development and Test . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{newillsmith2023cold,
  title = {Cold Operable Lunar Deployable Arm (COLDArm) System Development and Test},
  author = {Newill-Smith, David and Shatts, Jennifer and Dillon, Robert ``Peter'' and Karras, Jaakko and Brinkman, Alex and Backus, Spencer and Umali, Allen and McCormick, Ryan and Fradet, Lacie and Laramee, Jacques and Levanas, Greg and Fleischner, Richard},
  booktitle = {IEEE Aerospace Conference},
  publisher = {JPL Open Repository},
  year = {2023},
  doi = {10.48577/jpl.sgdhsw},
  abstract = {Future surface missions will require accessing new extreme environments which reach cryogenic temperatures. The Cold Operable Lunar Deployable Arm (COLDArm) system and component technologies can enable future missions in these extreme environments, including lunar night and Ocean Worlds. Here we report on the design, fabrication, and initial testing of the COLDArm system. The project is funded through the Lunar Surface Innovation Initiative (LSII) and managed by the NASA Space Technology Mission Directorate (STMD) Game Changing Development (GCD) program. The COLDArm system is developed with industrial partner, Motiv Space Systems, Inc (Pasadena, CA).The robotic arm leverages a design similar to the Mars Phoenix and Mars InSight robotic arms. The arm is four degrees of freedom (DOF), approximately two meters in length, and has a tip force greater than 40 newtons in the primary workspace. The significant innovation of the robotic arm is the ability to work in cryogenic environments without heaters. Eliminating heaters provides the benefits of reducing system energy needs and removing heaters from mechanisms located near volatile sample collection locations. The robotic joints include a planetary gearmotor and strainwave gear which utilize bulk metallic glass (BMG) gears to eliminate the need for heaters. Both the BMG planetary gearmotor and BMG strainwave gear have been successfully demonstrated at cryogenic temperatures. Additionally, the Dual-Axis Controller for Extreme Environments (DACEE) motor controller also eliminates the reliance on a warm electronics box (WEB). The DACEE motor controllers have also been successfully demonstrated at cryogenic temperatures.A Robotic Avionics and Sensor Kit (RASK) is located on the baseplate in a WEB. The RASK leverages the avionics design used on the Ingenuity Mars Helicopter which has been successfully demonstrated on Mars. COLDArm specific functionality has been added, including a 4-k resolution stereo camera pair and a force torque sensor (FTS) interface. Flight software (FSW) was also developed which leverages the Ingenuity FSW utilizing the Fprime framework.An end effector was designed in collaboration with Kennedy Space Center (KSC) and Glen Research Center (GRC) to collect geotechnical properties from the lunar regolith. End effector features include a scoop and geotechnical tool geometries to enable collection of regolith properties such as bearing capacity, angle of repose, shear strength, and pressure-sinkage parameters. The geotechnical scoop tool was designed for Titanium additive manufacturing in collaboration with Marshall Space Flight Center (MSFC) following NASA-STD-6030. A cryogenic capable FTS is located at the end effector to collect six-axis load information during the ground interactions. This FTS leverages the design from Mars 2020 and has been demonstrated at cryogenic temperatures.After fabrication and integration of the system, check-outs in the lab environment confirmed basic functionality of the system. Advanced functional testing was completed in the JPL Lunar Advanced Robotics (LunAR) Lab, including ground interaction demonstrations with GRC-3b lunar regolith simulant. These ground interactions demonstrations included large}
}
  17. Mccormick, R. (2024). COLDArm: A Cryogenic Capable Robotic Arm System for the Moon . Root. doi.org/10.48577/jpl.oyxw4y
    BibTeX
    @misc{mccormick2024coldarm,
  title = {COLDArm: A Cryogenic Capable Robotic Arm System for the Moon},
  author = {Mccormick, Ryan},
  journal = {Root},
  year = {2024},
  doi = {10.48577/jpl.oyxw4y},
  abstract = {No abstract available.}
}
  18. Redmond, M., Kempenaar, J. and Novak, K. (2017). Mars 2020 Mobility Actuator Thermal Testing and Model Correlation . International Conference on Environmental Systems. Source
    BibTeX
    @inproceedings{redmond2017mars,
  title = {Mars 2020 Mobility Actuator Thermal Testing and Model Correlation},
  author = {Redmond, Matthew and Kempenaar, Jason and Novak, Keith},
  booktitle = {International Conference on Environmental Systems},
  publisher = {JPL Open Repository},
  year = {2017},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:2014/47695}
}
  19. Schoelen, D., Arnold, R., Dolci, M. and Wehage, K. (2024). Development Robotic Arm System Testbed for the Mars Sample Return Campaign . IEEE Aerospace Conference. Source
    BibTeX
    @inproceedings{schoelen2024development,
  title = {Development Robotic Arm System Testbed for the Mars Sample Return Campaign},
  author = {Schoelen, Dane and Arnold, Richard and Dolci, Marco and Wehage, Kristopher},
  booktitle = {IEEE Aerospace Conference},
  publisher = {JPL Open Repository},
  year = {2024},
  doi = {10.48577/jpl.sz5uf4},
  abstract = {The NASA-ESA led Mars Sample Return campaign will be the first to deliver samples from another planet to thousands of scientists worldwide who will rewrite textbooks with their discoveries. A critical step in the campaign is the transfer of sample tubes from the surface of Mars to the ascent vehicle which will require a highly dexterous robotic arm and advanced control strategies. Development and testing of the control algorithms is being carried out at NASA’s Jet Propulsion Laboratory on R&D testbeds while the flight robotic arm is under development by the ESA. The algorithm testing requires a seven degree of freedom robotic arm testbed closely resembling the kinematic configuration of the flight design which utilizes comparable mechanical components and avionics. The actuators of the testbed were designed around off the shelf drivetrain and sensor components which resemble the operation and performance of their flight counterparts, without the added complexity and expense of extreme radiation, vibration and thermal robustness. The cable harnessing is largely off the shelf and is integrated into a cable management system commonly used on industrial robots which is cheaper, easier to install and modify than a custom ribbon cable solution. Each actuator was tested on the benchtop for performance characterization and qualification of load capability. The integrated robotic arm was kinematically calibrated using vision-based metrology and applied load test cases. This paper describes the design, construction, and commissioning of this testbed, dubbed Bradbury, which meets the needs of the sample handling algorithm testing campaign while remaining relatively inexpensive and efficient to construct and reconfigure.}
}
  20. NASA. (2015). NASA-STD-5017A: Design and Development Requirements for Mechanisms . NASA Office of the Chief Engineer. Source
    BibTeX
    @techreport{nasa2015mechanisms,
  title = {NASA-STD-5017A: Design and Development Requirements for Mechanisms},
  author = {{NASA}},
  institution = {NASA Office of the Chief Engineer},
  year = {2015},
  url = {https://standards.nasa.gov/standard/nasa/nasa-std-5017}
}
  21. NASA. (2022). NASA-STD-5017B: Design and Development Requirements for Mechanisms . NASA Office of the Chief Engineer. Source
    BibTeX
    @techreport{nasa2022mechanisms,
  title = {NASA-STD-5017B: Design and Development Requirements for Mechanisms},
  author = {{NASA}},
  institution = {NASA Office of the Chief Engineer},
  year = {2022},
  url = {https://standards.nasa.gov/standard/nasa/nasa-std-5017}
}
  22. Fusaro, R. L. (2001). Preventing Spacecraft Failures Due to Tribological Problems . NASA Glenn Research Center, NASA/TM-2001-210806. Source
    BibTeX
    @techreport{fusaro2001preventing,
  title = {Preventing Spacecraft Failures Due to Tribological Problems},
  author = {Fusaro, Robert L.},
  number = {NASA/TM-2001-210806},
  institution = {NASA Glenn Research Center},
  year = {2001},
  url = {https://ntrs.nasa.gov/citations/20010049424},
  abstract = {Many mechanical failures that occur on spacecraft are caused by tribological problems. This publication presents a study that was conducted by the author on various preventatives, analyses, controls and tests (PACTs) that could be used to prevent spacecraft mechanical system failure. A matrix is presented in the paper that plots tribology failure modes versus various PACTs that should be performed before a spacecraft is launched in order to insure success. A strawman matrix was constructed by the author and then was sent out to industry and government spacecraft designers, scientists and builders of spacecraft for their input. The final matrix is the result of their input. In addition to the matrix, this publication describes the various PACTs that can be performed and some fundamental knowledge on the correct usage of lubricants for spacecraft applications. Even though the work was done specifically to prevent spacecraft failures the basic methodology can be applied to other mechanical system areas.}
}
  23. Miyoshi, K. (2000). Solid Lubrication Fundamentals and Applications, Chapter 6: Friction and Wear Properties of Selected Solid Lubricating Films . NASA Glenn Research Center, NASA/TM-2000-107249, Chapter 6. Source
    BibTeX
    @techreport{miyoshi2000solid,
  title = {Solid Lubrication Fundamentals and Applications, Chapter 6: Friction and Wear Properties of Selected Solid Lubricating Films},
  author = {Miyoshi, Kazuhisa},
  number = {NASA/TM-2000-107249, Chapter 6},
  institution = {NASA Glenn Research Center},
  year = {2000},
  url = {https://ntrs.nasa.gov/citations/20010017158},
  abstract = {This chapter focuses attention on the friction and wear properties of selected solid lubricating films to aid users in choosing the best lubricant, deposition conditions, and operational variables. For simplicity, discussion of the tribological properties of concern is separated into two parts. The first part of the chapter discusses the different solid lubricating films selected for study including commercially developed solid film lubricants: (1) bonded molybdenum disulfide (MoS2), (2) magnetron-sputtered MoS2, (3) ion-plated silver, (4) ion-plated lead, (5) magnetron-sputtered diamondlike carbon (MS DLC), and (6) plasma-assisted, chemical-vapor-deposited diamondlike carbon (PACVD DEC) films. Marked differences in the friction and wear properties of the different films resulted from the different environmental conditions (ultrahigh vacuum, humid air, and dry nitrogen) and the solid film lubricant materials. The second part of the chapter discusses the physical and chemical characteristics, friction behavior, and endurance life of the magnetron-sputtered MoS2 films. The role of interface species and the effects of applied load, film thickness, oxygen pressure, environment, and temperature on the friction and wear properties are considered.}
}
  24. Singh, A., Kapa, D., Chedda, P. and Kolathaya, S. N. Y. (2025). Comparison between External and Internal Single Stage Planetary gearbox actuators for legged robots . International Conference on Advances in Robotics. Source
    BibTeX
    @inproceedings{singh2025comparison,
  title = {Comparison between External and Internal Single Stage Planetary gearbox actuators for legged robots},
  author = {Singh, Aman and Kapa, Deepak and Chedda, Prasham and Kolathaya, Shishir N. Y.},
  booktitle = {International Conference on Advances in Robotics},
  pages = {1-6},
  year = {2025},
  doi = {10.1145/3787370.3787403},
  abstract = {Legged robots, such as quadrupeds and humanoids, require high-performance actuators for efficient locomotion. Quasi-Direct-Drive (QDD) actuators with single-stage planetary gearboxes offer low inertia, high efficiency, and transparency. Among planetary gearbox architectures, Internal (ISSPG) and External Single-Stage Planetary Gearbox (ESSPG) are the two predominant designs. While ISSPG is often preferred for its compactness and high torque density at certain gear ratios, no objective comparison between the two architectures exists. Additionally, existing designs rely on heuristics rather than systematic optimization. This paper presents a design framework for optimally selecting actuator parameters based on given performance requirements and motor specifications. Using this framework, we generate and analyze various optimized gearbox designs for both architectures. Our results demonstrate that for the T-motor U12, ISSPG is the superior choice within the lower gear ratio range of 5:1 to 7:1, offering a lighter design. However, for gear ratios exceeding 7:1, ISSPG becomes infeasible, making ESSPG the better option in the 7:1 to 11:1 range. To validate our approach, we designed and optimized two actuators for manufacturing: an ISSPG with a 6.0:1 gear ratio and an ESSPG with a 7.2:1 gear ratio. Their respective masses closely align with our optimization model predictions, confirming the effectiveness of our methodology.}
}
  25. Singh, A., Kapa, D., Joshi, S. and Kolathaya, S. (2025). COMPAct: Computational Optimization and Automated Modular design of Planetary Actuators . IEEE International Conference on Robotics and Automation. Source
    BibTeX
    @inproceedings{singh2025compact,
  title = {COMPAct: Computational Optimization and Automated Modular design of Planetary Actuators},
  author = {Singh, Aman and Kapa, Deepak and Joshi, Suryank and Kolathaya, Shishir},
  booktitle = {IEEE International Conference on Robotics and Automation},
  pages = {9527-9534},
  year = {2025},
  doi = {10.1109/icra57385.2026.11697513}
}
  26. Georgiev, N. (2023). Efficiency Estimation and Optimization of Multistage Compound Planetary Gearboxes and Application to the Design of the Active Skin Propulsion of EELS . ["SAIRAS '99, International Symposium on Artificial Intelligence, Robotics and Automation in Space. Source
    BibTeX
    @inproceedings{georgiev2023efficiency,
  title = {Efficiency Estimation and Optimization of Multistage Compound Planetary Gearboxes and Application to the Design of the Active Skin Propulsion of EELS},
  author = {Georgiev, Nikola},
  booktitle = {["SAIRAS '99, International Symposium on Artificial Intelligence, Robotics and Automation in Space},
  publisher = {JPL Open Repository},
  year = {2023},
  doi = {10.48577/jpl.xhdulz}
}
  27. Georgiev, N., Gildner, M., Ambrose, E., Pailevanian, T., Archanian, A., Melikyan, H., Tosi, L. P., Loret de Mola Lemu, D., Paton, M., Thakker, R. and Ono, M. (2024). To Boldly Go Where No Robots Have Gone Before - Part 2: The Versatile Mobility of the EELS Robot for Robustly Exploring Unknown Environments . AIAA SciTech. Source
    BibTeX
    @inproceedings{georgiev2024boldly,
  title = {To Boldly Go Where No Robots Have Gone Before - Part 2: The Versatile Mobility of the EELS Robot for Robustly Exploring Unknown Environments},
  author = {Georgiev, Nikola and Gildner, Matthew and Ambrose, Eric and Pailevanian, Torkom and Archanian, Avak and Melikyan, Hovhannes and Tosi, Luis Phillipe and Loret de Mola Lemu, Daniel and Paton, Michael and Thakker, Rohan and Ono, Masahiro},
  booktitle = {AIAA SciTech},
  publisher = {JPL Open Repository},
  year = {2024},
  doi = {10.2514/6.2024-1965},
  abstract = {JPL has developed a snake-like robot concept called Exobiology Extant Life Surveyor (EELS) that applies a highly versatile mobility architecture and intelligent risk-aware autonomy towards exploration of unknown and uncertain environments in the solar system, such as the vents of Enceladus. The first instantiation of the EELS robot concept is called EELS 1.0, a modular snake-like robot with shape control through high degree of freedom articulation and screw-based active skin propulsion. This paper outlines the design of the EELS system and provides preliminary results of surface mobility experiments using the hardware system and autonomy software in laboratory and field settings. Through these experiments aspects of the hardware design's versatility were demonstrated through successful short traverses through terrains with varied topography and material properties. Implementation challenges related to the unique hardware architecture and their resolutions are outlined. Limitations of the EELS hardware system and avenues for further development are also discussed.}
}
  28. Choe, J., Kim, G., Kim, H., Kang, D., Kim, M.-S. and Park, H.-W. (2025). Design of a 3-DOF Hopping Robot with an Optimized Gearbox: An Intermediate Platform Toward Bipedal Robots . IEEE-RAS International Conference on Humanoid Robots. Source
    BibTeX
    @inproceedings{choe2025design,
  title = {Design of a 3-DOF Hopping Robot with an Optimized Gearbox: An Intermediate Platform Toward Bipedal Robots},
  author = {Choe, JongHun and Kim, Gijeong and Kim, Hajun and Kang, Dongyun and Kim, Min-Su and Park, Hae-Won},
  booktitle = {IEEE-RAS International Conference on Humanoid Robots},
  pages = {653-660},
  year = {2025},
  doi = {10.1109/humanoids65713.2025.11203011},
  abstract = {This paper presents a 3-DOF hopping robot with a human-like lower-limb joint configuration and a flat foot, capable of performing dynamic and repetitive jumping motions. To achieve both high torque output and a large hollow shaft diameter for efficient cable routing, a compact 3K compound planetary gearbox was designed using mixed-integer nonlinear programming for gear tooth optimization. To meet performance requirements within the constrained joint geometry, all major components—including the actuator, motor driver, and communication interface—were custom-designed. The robot weighs 12.45 kg, including a dummy mass, and measures 840 mm in length when the knee joint is fully extended. A reinforcement learning-based controller was employed, and the robot's performance was validated through hardware experiments, demonstrating stable and repetitive hopping motions in response to user inputs. These experimental results indicate that the platform serves as a solid foundation for future bipedal robot development.}
}
  29. Iacoponi, S., Bocchicchio, A., Ferrini, L., Thakker, R., Buscicchio, A., Georgiev, N. Z. and Carpenter, K. (2020). Improving Current-based Torque Sensing for Harmonic Drives Leveraging Asymmetry in Directional Efficiency . IEEE Robotics and Automation Letters. Source
    BibTeX
    @article{iacoponi2020improving,
  title = {Improving Current-based Torque Sensing for Harmonic Drives Leveraging Asymmetry in Directional Efficiency},
  author = {Iacoponi, Saverio and Bocchicchio, Alfredo and Ferrini, Lorenzo and Thakker, Rohan and Buscicchio, Alessandro and Georgiev, Nikola Zlatkov and Carpenter, Kalind},
  journal = {IEEE Robotics and Automation Letters},
  publisher = {JPL Open Repository},
  year = {2020},
  doi = {10.48577/jpl.kbmeba},
  abstract = {Torque estimation is a critical requirement for several manipulation and mobility tasks such as closed-loop force control, gravity compensation, contact detection, etc. This can be achieved by direct sensing with torque sensors which are heavy and significantly increase the load requirements of the system. An alternative approach is to using indirect sensing which estimates torques by measuring current consumption of the actuator. Unfortunately, this indirect approach suffers from low accuracy. We propose an estimation algorithm to improve this accuracy for the popular harmonic drive-based actuators. This is achieved by exploiting the asymmetry in efficiency which depends on the direction of torque transmission i.e. the efficiency of torque transmission is significantly lower in the output to input direction compared to input to output. This direction can be identified from the motor current and encoder data when the actuator has non-zero angular velocity but is not observable when the actuator is not moving. Our proposed solution significantly improves the accuracy for the former case and provides upper and lower bounds of torque estimates for the latter case. This is validated through experiments on hardware and comparison with ground truth from direct torque sensing.}
}
  30. Sauder, J., Hilgemann, E., Kawata, J., Stack, K., Parness, A., Johnson, M., Dunphy, S., Shahinian, A. and Beatty, T. (2021). Steampunk Meets Spacecraft: Hybrid Automaton Rover - Venus (HAR-V). dataverse.jpl.nasa.gov/dataset.xhtml
    BibTeX
    @misc{sauder2021steampunk,
  title = {Steampunk Meets Spacecraft: Hybrid Automaton Rover - Venus (HAR-V)},
  author = {Sauder, Jonathan and Hilgemann, Evan and Kawata, Jessie and Stack, Katie and Parness, Aaron and Johnson, Michael and Dunphy, Sean and Shahinian, Andre and Beatty, Tonya},
  year = {2021},
  url = {https://dataverse.jpl.nasa.gov/dataset.xhtml?persistentId=hdl:hdl:2014/54515}
}