Pioneer Road Building

By IonMars

Last edited July 24, 2014

How will we build the first Martian roads?  Back in Earth, building a road could involve huge earthmovers, giant excavators and oversized dump trucks. We would carve out mountainsides and fill in valleys. Even a 2-lane rural road would require substantial engineering and construction.  However, a Mars pioneer won't be expecting a six-lane freeway anytime soon. 

What are the minimal roads needed by a Mars pioneer?  Assume that he/she is a citizen of a small community, one of the first Martian settlements.  In this village there will be a cluster of habitats, a nearby landing site for transporters from Earth, a water mining site, a stone mining quarry, a stone block cutting area, and possibly a heavy metals mine.  These are the immediate destinations that require at least a primitive roadway to allow commuting on a regular basis. Also remember that Mars daily temperature fluctuations are extreme, from above freezing during a summer day and -50 degrees C or lower at night.  It could be dangerous a colonist to remain outside a protected habitat after dark, so we should plan to return all personnel and most equipment before sundown every evening.  If surface vehicles can attain an average of 10 km/h then 5 km is a reasonable maximum radius for daily round-trip commuting.  Beyond this perimeter looms the rugged exploration area that extends to the horizon. Later, as vehicles and roads improve, then a wider commuting zone could be established; Earth-like road networks will come later.Curiosity in Gale Crater

Every piece of road-building equipment on Mars must be shipped 150+ days from the home world1. Given the extravagant price of importing equipment, what types of roads will make the biggest improvement with the least investment in equipment?  The robotic Mars Science Laboratory (MSL) Curiosity showed one answer to us on its sojourn through Gale Crater in 2013.   Curiositys maximum rated speed was only 144 meters per hour (m/h).  Even this sluggish pace was achievable only in low-slope terrain with no obstacles.  In more rugged countryside with obstacles and scarps the rated speed slows to 45 m/h.  In high slope terrain where the soil lacks cohesion the speed drops again to 29 m/h and when the vehicle encounters highly sloped, very rugged terrain it could only manage 20 m/h2. 

The relationship between terrain and surface speed of the MSL suggests that if we merely develop a path wide enough for a vehicle to pass through, we could expect substantial improvement.  If we removed rocks and boulders from the path, detoured around large outcroppings, and avoided steep slopes by routing the path around hillsides, we might expect to increase speed by 2 to 5 times and perhaps realize theCompact Track Loader vehicles rated capacity.  Careful route planning will be the first step in developing a usable road.  Removing obstacles from the planned path will be the second step, consisting of picking up and moving aside rocks and boulders to clear the way as much as feasible. 

Clearing rocks from a planned roadway will require a front-end loader as suggested in the adjacent figure.  It will be desirable to employ a small size machine that is adapted for use on Mars, small enough to be transported from Earth and still be effective.  In the experience of the author, the Bobcat T550 could be that machine.  At 3475 kg it is light enough for transport and its rated operating capacity of 905 kg (2283 kg Mars) is more than powerful enough3.  It features an enclosed cab that could be converted to an airtight shell.  With added insulation, galactic cosmic radiation (GCR) protection and an environmental control and life support system (ECLSS), it could be used on Mars.  If it is equipped with a NASA-compatible hatch as suggested for the Mars stone house (See the article Pioneer House Building on this website), the operator could drive in shirtsleeves and work for a full day at a time.Damage to Curiosity's wheels  The treaded version would be preferred over a wheeled vehicle for road building because it will operate in undeveloped terrain.  The treads would provide more resistance to damage from sharp basaltic rock.  Once the basic road system is established, the wheeled version will be needed for greater speed, as long as it stays on roads.  A Mars pioneer would like to see NASA develop a prototype of a Mars front-end loader before colonization planning begins.  

Meanwhile, after a time of passage along its journey, the MSL encountered a problem that was unexpected.  On the 177th Martian day after the landing (Sol 177) Images taken by an MSL camera documented a worrisome number of rips, tears and holes up to several centimeters wide in the six aluminum wheels4.  While MSL designers were originally concerned about deep sand drifts and engineered the wheels accordingly, what was actually encountered was hard, craggy basalt thinly covered by fine-grained regolith.  Sharp glassy rock edges protruding rocky points were continuously chipping away at the soft metal treads and threatened to shorten the lifetime of Curiositys ability to meander.  This discovery implies to a Mars pioneer that even minimal road building must mitigate the potential destruction of vehicle treads. 

Small pieces of rock left on a crude roadway would usually be useful.  They help to even out the road surface by filling in the gaps between ridges in an uneven surface.  As discovered by the MSL, however, even small debris on Mars can be troublesome because of their sharp edges.  This is the result of several billion years of bombardment by galactic cosmic radiation and micrometeorites.  When the bombardment strikes the regolith with high energy it causes a microscopic melting and binding together of particles.  The result is an Hydraulic breaker on a backhoeagglomeration of rocky material with glassy sharp edges5. We may call them glassicles.

A simple way to reduce damage to wheel treads is to further prepare the road bed by breaking down the more prominent jagged edges sticking out above the regolith.  This is especially important where the protruding rock is part of a basaltic mass and not merely an individual stone that can be tossed aside.  One method of breaking rock outcrops and stones is to employ a hydraulic rock breaker mounted on a backhoe arm, such as that shown in the adjacent picture.  On Earth, this equipment is used in surface mining operations when it is necessary to break larger rocks into smaller pieces so a loader can pick them up.  Such a large machine would be infeasible to ship the entire way to Mars for initial road building, so a smaller device is needed to do the same job. 

On Earth a hand-operated hydraulic breaker is commonly used to break up old cement on a construction site.  The cylinder bounces up and down rapidly, directing a heavy force through the point of a metal pin and onto to the cement or rock that is being split.  It emits the familiar rat-a-tat-tat-tat sound that causes passers-by to hold their ears.  This breaker is about the right size for a small-scale road/path building operation on Mars. 

The problem with applying this handheld equipment on Mars is that the work would have to be done in a spacesuit.  Control of a powerful rapidly vibrating machine is a demanding job for a human being, much less a human in a spacesuit.  While the technology of spacesuits has advanced so that they are more reliable, they must be designed for flexibility, which automatically limits how durable they can be.  A spacesuit must be composed of many layers of material and must necessarily represent a compromise in ruggedness compared to a rigid capsule.   The road-building job will not be an occasional EVA for repairs but a continuous daily operation.  The spacesuit should be held in reserve for occasions where equipment within a rigid cabin having interior controls for exterior manipulators is not sufficiently dexterous for a delicate job. Breaker Attachment

A good compromise between large and small equipment is to employ a hydraulic breaker that is a component of a machine already equipped with a control cabin designed for Mars.  In the case of the Bobcat front-end loader, there are about 40 attachments that can be used in place of the scoop, including a hydraulic breaker. The breaker attachment shown in the adjacent photo delivers 60 to 1000 ft.-lb. of force, which should be very adequate for basic Mars road-building.  According to Bobcat Company, it can be quickly attached to the loader.  Note that the attachment lacks the auxiliary motor that provides hydraulic pressure as in the handheld model.  This is because the breaker attachment utilizes the hydraulic system of the loader to provide hydraulic pressure for the breaker. 

Once the rock breaker has pulverized the rock outcrop into smaller pieces, the loader will push the larger chunks off the path and leave the smaller ones to fill in small cracks and gullies.  This can be achieved by changing appurtenances on the same machine or by running two loaders in tandem, one with a rock beaker and one with a bucket.Footprint on the Moon

Preparing the rock bed will be followed by tamping the surface to drive any small pieces into the regolith and to compress the ground into a compact mass more suitable for the passage of vehicles.  A first order of tamping can be accomplished by simply running over the ground with the treads of the loader.  This is common practice on Earth.  How do we know that the regolith will be compressed in this manner?  The famous photograph of an astronauts footprint on the moon demonstrates how easily it can be accomplished.  Mars regolith is little different from that of the moon except it is more evenly distributed across the planet by windstorms. 

An effective method of ameliorating the hazard of ragged rocks is to lay down a layer of gravel over them, especially in the roughest terrain.  However, producing the gravel to create this refinement of the road is no mean task because it entails mining rocks or boulders, breaking them into smaller sizes, and screening out the rocks that are too large or too jagged.  Mining and screening this material usually requires a fully equipped rock quarry operation involving a number of large machines.  For this reason it may be a road improvement that must occur later in the development of the Martian settlement. As an intermediate solution, fine-grained regolith will be scooped from an area of dunes and carried to the rocky road locations to apply a solid covering, then tamped. 

 

Screening the Regolith

When a colonist searches for fine-grained regolith to cover a roadway, there is no guarantee he will find material free of rocks and glassicles.  Some debris can be screened out by a tine rake attachment or a rock bucket attachment to the front-end loader. (See the article Mars Village Vehicles.) But to eliminate almost all the undesirable pieces, a special screening machine will be needed. Such a device may be the EZ-Screen 550 at work in the photo below.  The screener is receiving compost for processing in Earth conditions, but it could just as well be regolith mixed with rock and

Rock Screener

glassicles. The material is dumped slowly at the upper end of a sloped vibrating screen and the small size particles pass through to the ground below, while the larger pieces pass over the screen to the opposite side, as shown. At 1960 lbs. weight at launch from Earth this mini-screener will do the job for road building on Mars. The model 550 employs one screen and will accommodate a loader bucket up to one yard in size, which matches the size of the bucket on the Bobcat T550.  The screening box is 5 ft. by 4 ft. and holds screening cloth of various sizes that can be specified. The screening box is mounted on four jacks so that the angle of the screen can be adjusted. One drawback is the use of a 5.5 HP gasoline engine, which must be traded out for a methane-fueled motor. The machine is portable, being mounted on a 13 foot-10 inch long frame carried on two wheels with B78X13 tires. It will be towed by a ½-ton pickup. 

While road building could conceivable be carried out by one colonist, a team will be safer and more effective. A Mars road-building crew will typically consist of three colonists; two persons in front-end loaders and one in in a spacesuit to manipulate outdoor dials and levers. One front-end loader will be equipped with a standard bucket; the other will carry a rock-breaker and other attachments to switch out as needed. The spacesuit could be traded for a Mars Utility Vehicle (MUV) if it proves to be more effective. (See the article Mars Village Vehicles.) The two loaders will move out to the days work site accompanied by an MEV pickup with a man in a spacesuit carried in the truck bed and towing the dirt-screening machine. Once all equipment is set up, the truck driver will return to the village. At the end of the day he will travel back to the work site and reverse the procedure. 

If road building were coordinated with the cutting of stone blocks, say for building a stone house, then the collection of rocks from road building could feed directly into the stone cutting process. For efficiency, MEVs returning to the village from road building could bring suitable rocks for cutting into blocks or for dry-stacked stonewalls.  

 

Summary

Pioneer road building on Mars can be accomplished with a compact front loader, a bock-breaking attachment, and a regolith-screening machine.  A cleared path will be prepared by removing boulders, breaking up jutting rocks, applying fine-grained regolith over it, and tamping the surface to provide a rudimentary road.

 

References

 

(1) Cain, Fraser (2013) How long does it take to get to Mars? Universe Today, May 9, 2013.

(2) Golombec, et. al Selection of the Mars Science Laboratory Landing Site," Space Science Review September 2012, Vol. 170, Issue 1-4, Table 12.

(3) Bobcat Company (Undated) Compact Tract Loaders Specifications and Features, Pamphlet.

(4) Kremer, K., Rough Red Planet Rips Rover Curiosity Wheels, Universe Today Sept 26, 2013.

(5) EZ-Screen Portable Topsoil Screeners (undated) Retrieved July 117, 22014 from http://www.ez-screen.com/ez-screen-550.