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Curiosity rover -- "go" configuration
This working 1:12 scale model of the Mars Science Laboratory rover captures Curiosity's main visual features and delivers scaled rough terrain performance comparable to that of the real thing.
About this creation

Please feel free to look over the images and skip the verbiage.

This page presents the more functionally realistic "go" configuration (GC) of an MOC I consider one of my best -- a 1:12 remote control model of the Mars Science Laboratory (MSL) rover "Curiosity".

The video below shows the GC doing what it does best -- traversing rugged terrain in my personal "Mars Yard".1



Curiosity is the ultimate off-road vehicle, albeit a very slow one. Its sophisticated 6x6x4 mobility system keeps all six wheels firmly planted and pulling in soft soil and rugged topography alike. The independently steerable corner wheels allow it to turn in place.

The 6x6x0 GC has only limited skid steering due to size and cosmetic constraints, but it can overcome step-like obstacles 50% taller than its wheels, just like the real thing.





The original GC actually predated the more visually realistic "show" configuration (SC) below, but the SC got its MOCpage first, and no GC photos or videos of the GC in action were included.





Relative to the SC, the GC (i) relocates some deck features to make room for the necessary IR receivers, (ii) replaces the fake PF rechargeable battery aft with a real one, (iii) hooks up all the electricals, and (iv) adds rubber bands running beneath the hull to reduce lateral spreading of the wheelsets in motion. The 2 configurations are otherwise nearly identical.

Curiosity sends back selfies constantly. Some are for PR purposes, but most are engineering self-inspections. It took this true-color MAHLI mosaic on October 6, 2015 (its 1,126th sol on Mars) while standing over a freshly drilled hole in cross-bedded sandstone at the "Big Sky" study site.



Gray tailings mark the hole at far left. The rover's proud as a dog that just dug up a bone.



On this page:


General modeling goals and solutions

This MOC was almost complete when TLG released the much smaller "NASA Mars Science Laboratory Curiosity Rover" set (21104) designed by MSL engineer Stephen Pakbaz. Modeling at 1:12 instead allowed much more visual and functional realism -- including comparable scaled rough terrain performance under PF remote control.



Below are the visual and mechanical features I modeled with some success. Functional features central to the MSL mission got top priority. The new outdoor photos are of the GC.

∨ Scaling: Within 5% of 1:12 scale on all major features except wheel width (too narrow) and the many small but functionally important details on the instrument turret, which ended up closer to 1:10. In retrospect, 1:8 scale would have been a smarter choice.



∨ Mobility system: Six-wheel drive with fully functional rocker-bogie suspension (RBS) 2 and limited skid steering (see below). The GC's rough terrain capability comes from its perfectly scaled RBS geometry and ground clearance.







∨ Robotic arm (RA): Manual operation of all 5 degrees of freedom (DOFs) with good positional stability. All joint actuators and flex spools represented.







∨ Instrument turret at end of RA: Main external features represented, including the percussion drill with guards, CHIMRA soil scoop and sample processor, Dirt Removal Tool (DRT), Alpha Particle X-ray Spectrometer (APXS), and Mars Hand Lens Imager (MAHLI).







∨ Instrument mast: Motorized head rotation with manual tilt. All external features represented, including the remote warm electronics box (RWEB), ChemCam telescope lens, paired MastCams, stereo NavCams, twin REMS booms, and tilt actuator.





∨ Nuclear power supply and internal thermal control system: All external features represented, including Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) core and 8-fold cooling fins flanked by C-shaped heat exchange panels.







∨ Antennas: From left to right, LBG high-gain with manual azimuth-elevation gimbal, gold-tipped low gain, and black can-like UHF.





∨ Forward and port deck: From left to right, RA cable guide, CheMin and SAM sample inlets, SkyCrane cable attachment, RAD aperture, differential arm and link, and high-gain antenna in current colors.



∨ Starboard deck: From left to right, UHF antenna on pylon, black sundial on pyrotechnic control box, working black differential arm and link to the rocker pivot arm, and black SkyCrane cable attachment.



∨ Forward and aft hull panels: Gray observation tray and sample playground, black spare drill bit boxes, colorful organic check material (OCM) cannisters, black RA mount, and white front and rear HazCams.





∨ Drilling at Mount Sharp: It's just a saying, right?



The SC MOCpage contains a wealth of info on Curiosity, the MSL mission, and the MOC.

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The "go" configuration (GC)



The MOC ended up with a 6x6x0 platform rather than Curiosity's 6x6x4 because I couldn't find a visually acceptable way to steer the corner wheels at 1:12.



However, I could get limited skid steering by putting all 3 starboard motors on one IR receiver terminal and all 3 port motors on another. Since I also had an instrument mast micromotor to control, the GC needed 2 receivers in all, and both would have to be mounted on deck, as the hull was already full (another consequence of the 1:12 scaling).3



But as I discovered the hard way, V2 receivers shut down automatically when a terminal sees more than 2 motors, even at low current loads. Hence both receivers had to be V1s because (i) V1 receivers don't mind having 3 motors on a single terminal, and (ii) powering all 6 wheel motors with the same receiver made no sense from a current supply and thermal protection standpont.

The MOC's RBS is remarkably resilient for its weight and construction, but the rockers and bogies aren't quite strong enough in torsion, and the bending moments on the rocker pivot axles are substantial. As a result, the wheels tend to spread laterally when the MOC travels, especially forward. The resulting negative camber reduces both ground clearance and RBS range of motion.



If my RBS were made of the exotic alloys NASA uses, I wouldn't have had to resort to pulling the rockers together with stout rubber bands (not shown) crossed under the hull. (The rubber bands attach to the LBG towballs hanging beneath the rockers here.) Additional rubber bands reinforce the bogie pivots. There are no other non-LEGO® parts.

The red lever on the simple 3-state PF handset below controls the port wheelset; the green, the starboard wheelset; and the orange, mast rotation. The motor cables block the IR beams all too frequently, but I had nowhere to tuck them away at 1:12.



The SC MOCpage contains a wealth of info on Curiosity, the MSL mission, and the MOC.

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About Curiosity, the MSL mission, and Mars

For my money, Curiosity and its astonishing entry, descent, and landing (EDL) scheme are together the greatest and most daring engineering feat in history. This pre-flight NASA animation gives a good feel for the mission, while this one (a must-see) highlights the EDL. Both are remarkably close to what's actually gone down.

"Curiosity" is the official nickname of the revolutionary Mars rover flown by NASA's ongoing "Mars Science Laboratory" (MSL) mission. Another nickname is "MSL".

Curiosity was designed to function as a largely autonomous robotic field geologist, advanced imaging and remote sensing platform, sophisticated chemical and mineralogical laboratory, weather station, and advanced telecommunications station on wheels. Since landing in the NW sector of Gale Crater on August 6, 2012, it's performed all these duties flawlessly.

The over-arching question Curiosity was sent to answer -- whether Mars has ever been habitable by life as we know it -- has already been answered in the affirmative. In the process, Curiosity also confirmed what had long been suspected from previous missions: Before Mars lost its atmosphere and dried up some 4 billion years ago, sizeable streams and lakes of liquid surface water clearly existed in Gale Crater. It follows that water also flowed and collected in many other places with similar landforms and stratified rocks.

As of this writing (December, 2015), we still have no conclusive evidence that life ever existed on Mars, but we know now that microbes could have eeked out a living in the muds deposited in the "Yellowknife Bay" fossil lake bed that Curiosity drilled in March, 2013. Back then, ca. 4.2 billion years ago, the Martian climate was warm and wet, and water flowed into Gale Crater from the surrounding uplands.

Now, three and a half years on Mars and still going strong, Curiosity stands poised to address the next big mission question: Why, and exactly when, did Mars dry up? Just ahead, on the lower slopes of Mount Sharp, Gale Crater's somewhat enigmatic central mound, are alternating beds of clay- and sulfate-rich sedimentary rocks that by all indications record the transition.

These strata were Curiosity's ultimate drilling targets at launch, but the nuclear power supply has many years of service left, and the wheels are holding up well enough to allow mission planners to consider a long list of additional science targets. With luck, Curiosity will still be sending back valuable data for many years to come, just as its predecessor Opportunity has done.



Topographically, and rather enigmatically, Mars is divided into 2 distinct hemispheres. This low-angle orbiter image of the Martian surface shows a section of the transition between the rugged rocky southern highlands to the right and the northern plains to the left. Gale Crater lies just south of this transition, but not at this longitude.

Above the horizon is the Martian atmosphere, reddened by the ultra-fine iron oxide-rich dust covering nearly all of the planet's surface. Dust storms, sometimes global in extent and weeks in duration, are frequent on Mars. Dust-covered solar panels nearly killed Spirit and Opportunity several times, but Curiosity's nuclear power supply eliminates that risk.

The SC MOCpage contains a wealth of info on Curiosity, the MSL mission, and the MOC. One of the best ways to follow the mission is through Emily Lakdawalla's blog at The Planetary Society.

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Specifications (GC only)

Subject:Mars Science Laboratory rover Curiosity
Scale:1:12 except for instrument turret (~1:10)
Construction:Studded hull with studded and studless appendages
Overall dimensions:280 x 256 x 188 mm (LxWxH) with RA and turret stowed
Overall weight:1.09 kg
Mobility system:6x6x0 (as opposed to Curiosity's 6x6x4)
Suspension:Fully functional rocker-bogie
Propulsion:M motor on each wheel
Steering:Limited skid via independent control of right and left wheelsets
Wheels:43.2x28 small ballon wheels and 30x13 Model Team wheels stuffed back-to-back into 43.2x28 small balloon tires
Motors:6 Ms for propulsion, 1 micro for instrument mast head rotation
IR receivers:2 V1s to allow 3 M motors per receiver terminal
Electrical power supply:7.4V Li polymer rechargeable battery
Modified LEGO® parts:Many -- mostly parts of small bar-bearing parts in the instrument mast head and turret
Non-LEGO® parts:Rubber bands to reduce wheel spread and reinforce rear bogie pivots
Credits:Entirely original MOC, including diorama

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Footnotes

1 Curiosity was designed and built by NASA's Jet Propulsion Laboratory (JPL) in Pasadena, CA. Much of the pre-launch testing of its mobility system took place in JPL's "Mars Yard" -- basically an outdoor "test track" that simulates surface conditions likely to be encountered on Mars. Reseach on how to minimize future wheel damage continues there today.

2 To date, every Mars rover has gotten around on a 6x6x4 mobility system with all 6 wheels driven, all 4 corner wheels steered, and NASA's patented "rocker-bogie suspension" (RBS). The "bogie" on a given side carries the rear and middle wheels at its ends, while the "rocker" carries the front wheel and the bogie. The bogie pivots freely on the rocker, but the hull doesn't.

Instead, the hull's attitude WRT the rockers is constrained by (i) an internal differential gearbox connecting the right and left rocker pivots, and (ii) an external differential arm linked to lever arms keyed to both rocker pivots. The hull is to the internal differential as the differential case on a car is to the gearing inside.

The net effect is to fix hull pitch at the average pitch of the rockers relative to the horizontal. This beneficial geometry increases traction by equalizing wheel ground pressures and reduces the risk of roll-over and high-centering as well.

The MOC incorporates working versions of all major mobility system features other than the corner wheel steering. For a discussion of RBS-related wheel damage on Curiosity, click here. For a LEGO demonstration of the differential system, click here. And for the best job ever, click here.

3 The highly stressed hull has a good bit of internal structure. It also contains the instrument mast micromotor and gearbox, the battery, and the differential gearbox linking the rocker to the hull.

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Comments

 I made it 
  January 7, 2017
Quoting Seaman SPb Fantastic work! Go to Mars! :)
Thanks, Seaman! See you there!
 I like it 
  January 7, 2017
Fantastic work! Go to Mars! :)
 I made it 
  March 8, 2016
Quoting Zachary Baker Wow! Awesome! That's a lot of motors! I don't even have one! ;) keep on clickin' ;) er brickin' ;) witch ever you prefer!
Thanks, Zachary! Not much choice WRT the motors here, as the rocker-bogie suspension used on Mars rovers works only when all six wheels are driven.
 I like it 
  March 7, 2016
Wow! Awesome! That's a lot of motors! I don't even have one! ;) keep on clickin' ;) er brickin' ;) witch ever you prefer!
 I made it 
  December 21, 2015
Quoting Vibor Cavor This works really good.
Thanks, Vibor!
 I like it 
  December 21, 2015
This works really good.
 I made it 
  December 15, 2015
Quoting matt rowntRee Holy cow, so much brilliance in a single moc! I can't believe the detail and mobility you packed in here. Looks like the real skateboard on Mars. XD Now to chase after the cat. ;) Awesome!
Many thanks, Matt! Of all my MOCs, I'm proudest of this one.
 I like it 
  December 15, 2015
Holy cow, so much brilliance in a single moc! I can't believe the detail and mobility you packed in here. Looks like the real skateboard on Mars. XD Now to chase after the cat. ;) Awesome!
 I made it 
  December 14, 2015
Quoting Gabor Horvath Wow! Amazing job! A very realistic and detailed model and it works very well! It looks cool in the video!
Thank you very much, Gabor!
 I like it 
  December 14, 2015
Wow! Amazing job! A very realistic and detailed model and it works very well! It looks cool in the video!
 I made it 
  December 10, 2015
Quoting Didier B Oups ! I guess you lost a piece at 6'03"... Nice build Jeremy. I like the brown landescape too. It highlights your creation well. Didier
Thanks, Didier! Yes, that was the UHF antenna. Having no need for streamlining, Curiosity's deck is bristling with appendages for my motor cables to snag on. Unfortunately, I'm stuck with that. Restraining the cables in any way to prevent it would limit the suspension's range of motion, which was the top modeling priority here.
 I like it 
  December 10, 2015
Oups ! I guess you lost a piece at 6'03"... Nice build Jeremy. I like the brown landescape too. It highlights your creation well. Didier
 I made it 
  December 9, 2015
Quoting Topsy Creatori Oh, that rock makes me want to call it schist, am I correct or completely clueless?
You're close. It's a rather dark, coarse feldspar-rich Colorado sandstone with reddish iron oxides cementing the grains together. The grains, though, could easily have been eroded out of the dark gray and pinkish schists and gneisses found all up and down Front Range here. After weathering, the colors aren't far from what you'd see in Central Park schist, NYC. You'd have recognized it as a sandstone if I'd whacked off a corner with a rock hammer and shown you a fresh surface.
 I made it 
  December 9, 2015
Quoting Topsy Creatori Oh yah, a very cool build of a very cool vehicle! Its SAM has some nifty chem analytical instrumentation like a quadrupole MS AND a GC! :)
Thanks, Topsy! Coolest vehicle in the solar system, if you ask me. As you know, JPL shrank the SAM instrument suite from room-size to briefcase-size to get it inside the hull and space-hardened it to boot. Then they turned around and did the same for CheMin, the X-ray diffractometer. Anyone who's been around that kind of equipment understands the miracles involved, and it's all working perfectly! On Mars!
 I like it 
  December 9, 2015
Oh, that rock makes me want to call it schist, am I correct or completely clueless?
 I like it 
  December 9, 2015
Oh yah, a very cool build of a very cool vehicle! Its SAM has some nifty chem analytical instrumentation like a quadrupole MS AND a GC! :)
 I made it 
  December 8, 2015
Quoting The Royal Brick That's just awesome! When will you be sending it to Mars?
Thanks, TRB! I was hoping to hitch a ride on the Mars2020 mission, but JPL said I'd have to ditch the PF remote control for something with a little more range.
 I like it 
  December 8, 2015
That's just awesome! When will you be sending it to Mars?
Jeremy McCreary
 I like it 
Kain .
  December 7, 2015
Very nice work here
 I made it 
  December 7, 2015
Quoting Kain . Very nice work here
Thank you very much, Kain!
 I made it 
  December 7, 2015
Quoting Desert752 Kirill Very interesting model!
Thanks, DK! I can see you building something like this. I'm considering a "Bride of Curiosity".
 I like it 
  December 7, 2015
Very interesting model!
 I made it 
  December 7, 2015
Quoting Michiel Norp Brilliant, out of this world
Many thanks, Michiel!
 I like it 
  December 7, 2015
Brilliant, out of this world
 I made it 
  December 7, 2015
Quoting Oliver Becker Outstanding MOC, Jeremy! I hope, Curiosity does'nt kill the cat... ;) (What a pic- content: LOL Love it!)
Thanks, Oliver! Don't worry, the cat's safe. The rover and its various appendages move so slowly that it would only have a chance with a cat that's already dead. Not much road-kill on Mars yet.
 I like it 
  December 7, 2015
Outstanding MOC, Jeremy! I hope, Curiosity does'nt kill the cat... ;) (What a pic- content: LOL Love it!)
 I made it 
  December 7, 2015
Quoting Gabor Pauler Ahh, skid steering with rocker beam! Nice incorporation of PF XL motors. One good thing in being retired that you have tons of time to do such a things...
Thanks, Gabor! Yes, and time is what it takes -- lots of time for study of the real thing and trial and error, especially the last two. The suspension alone went through many iterations, and detailing the turret was a nightmare.
 I like it 
  December 7, 2015
Ahh, skid steering with rocker beam! Nice incorporation of PF XL motors. One good thing in being retired that you have tons of time to do such a things...
 I made it 
  December 7, 2015
Quoting Nils O. Very cool, I absolutely love it! The look is perfect and the PF are as good as they get in this scale. Great job! :-)) P.S.: I still have a skid steered 6x6 Rover/Buggy with rocker/bogie suspension in mind. I hope I'll find the time during winter holidays to finish a PF rolling chassis...
Many thanks, Nils! I'm sure you'll have a lot of fun with your rover. The suspension is fascinating to watch in action.
 I like it 
  December 7, 2015
Very cool, I absolutely love it! The look is perfect and the PF are as good as they get in this scale. Great job! :-)) P.S.: I still have a skid steered 6x6 Rover/Buggy with rocker/bogie suspension in mind. I hope I'll find the time during winter holidays to finish a PF rolling chassis...
 
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