Mars Village Vehicles

By IonMars

Last update July 20, 2014


As of 2014, the principal vehicle that NASA has developed for Mars is the multi-mission Space Exploration Vehicle (SEV).  It consists of a pressurized cabin to serve as a mobile habitation module with large windows for observation.  It will be used for missions in space, on the Moon and on Mars1.   The in-space version sports manipulator arms and is mated to a flying platform whereas the surface (Mars) version is mounted on a 12-wheel chassis that can travel through rough terrain up to 10 km/hr.  The module is connected to a “suitport” that allows two explorers to step directly into their EVA spacesuits in only 10 minutes.  It also has a door (a docking hatch) that allows the explorers to pass from the SEV through a flexible passageway into the NASA Habitat Demonstration Unit (HDU) in their shirtsleeves with no depressurization2.  The rear view and some of the specifications of the SEV are shown in the figure below3: SEV

The SEV is designed to allow two explorers to conduct extensive forays for up to two weeks before returning to the habitation base at the Mars landing site.  It contains enough supplies and ECLSS for such a trip.  In other words, its purpose is to explore the Martian landscape beyond the vicinity of a Martian village.  Within the village, colonizing will be under way and houses and rudimentary roads will be under construction.  Exploration and colonization can proceed separately or concurrently from the same base location. The Mars EVA vehicles (MEVs), or “village vehicles” addressed in this article will be quite different from the SEV and will serve different purposes.  These transporters will be more compact, the cabins will be smaller, the range of the vehicles will be shorter, and they will be designed for more specialized operations.

In the first stage of colonization all MEVs will be construction equipment. The first three  vehicles to be unloaded from the Mars Lander will be a front-end loader with varied attachments, a truck, and a utility vehicle.   These three will deliver a very high capability in the Mars environment without costing an excessive amount in haulage. They epitomize the nature of all Mars equipment, i.e. “highly effective and low mass.” These are the minimum equipment required to build houses, develop roads and construct storage tanks. Then, if weight allocations on the colonial transporter allow further equipment to be imported, then a dump truck, a small crane, and possibly a well driller could be included on the cargo list.  A backhoe is not included on this list because of the likelihood of encountering hard basaltic rock near the surface that will nullify its practical usage; however, a small backhoe attachment is included for digging in deep regolith pockets.  The Mars village vehicles will be based on analogues that are well known on Earth but are adapted for use on Mars.  Other more varied vehicles can be introduced at a later time.

Front-End Loader

One of the Earth analogues for an MEV is a front-end loader such as the one shown in the figure below.  The Bobcat T550 was already chosen as a possible equipment item for constructing rudimentary roads around a Mars colony.  (See the article “Pioneer Road Building”.)  To convert the Bobcat into a Mars-capable vehicle five steps are required, as follows: 

  1.  The cab must become completely airtight.  The Bobcat cab is already BobCatdust-tight so one component of this conversion is partially completed.  The controls are electronic so that no mechanical devices have to protrude through the floor (4).  (One sales option is remote control of the vehicle!)  The interior of the cab is shown in the adjacent figure.  The two side windows with protective screens have gaskets that must be tested for air-tightness or removed and the windows sealed or welded tightly to the cabin.  The large window in front is also a door that opens on a side hinge for ingress and egress in Earth conditions; this will have to be welded shut.  The cab is a separate compartment that can be removed from the engine and chassis by unscrewing two bolts.  The cabin underside will have to be inspected and any openings completely sealed.
  2.  The cabin roof must be rebuilt to install an EVA hatch.  Top entry into the cab will be necessary for all MEVs because side or front hatch entries would interfere with visibility and with the functioning of the vehicle.  The method of entry from a Mars house into a top-entry MEV is illustrated in the article “Pioneer House Building”.
  3. The engine must be converted to use methane fuel and 100 percent O2 oxidizer from pressurized tanks.  Methane will be used on Mars because NASA is planning to produce methane using the Sabatier process and store it to refuel rockets that will be returning to Earth.  This fuel conversion will not be difficult because most diesel engines can already utilize a wide variety of fuels and some have natural gas (NG) conversion kits.  NG is 95 percent methane (5).  Finding a location for two pressurized tanks may be more difficult.  The engine compartment is already tightly fitted with engine components and the old fuel Inside of Bobcattank is not conveniently located.  If all else fails the tanks may be strapped to the exterior of the cab inside a metal cage for protection from rocks.
  4. Equipment for Environmental Control and Life Support Systems (ECLSS) must be installed.   Fortunately the ECLSS requirements of an MEV cab are like a spacesuit where a minimum of equipment may be deployed.  A Mars village EVA will be limited to 6 to 8 hours during daylight because after sundown the surface temperature plunges and staying outdoors may be dangerous.  Such a day trip will require a supply of O2, a CO2 removal unit, temperature control, and collection of urine and body wastes.  Pressurized O2 is already required for methane combustion so the container needs to be larger to include ECLSS.  A CO2 removal unit similar to one built into an astronaut’s backpack will be needed.  Space for this unit is scarce; it may have to occupy the vacancy left by the previous fuel tank.  For temperature control, the HVAC unit already installed in the Bobcat loader will likely suffice, except that no outside air may be allowed and the system must be airtight. Urine and body waste will be collected in a carefully designed container.  In fact, end-of-day chores may include cleaning and ventilating the MEV and (ugh) emptying the “thunder mug” unto the house waste disposal system.
  5. Extra protection will be needed to guard against exposure to ultraviolet (UV) light and galactic cosmic rays (GCR).  UV is surprisingly strong on Mars despite the long distance to the sun because there is little atmosphere to intercept UV.  For driver protection a darkened windshield with a color tone designed to block such rays will be necessary.  To protect against GCR a roof extension, like a sun visor on the exterior of the cabin, will be needed to shield the driver from cosmic rays raining down on nearly airless Mars.  This will limit the horizontal line of sight to the level of the Mars horizon.  A side effect of the visor may be to obscure the driver’s vision when the loader bucket is lifted higher than the visor and the driver cannot see it.  For this reason it will be necessary to design the visor to be lifted temporarily when the bucket is lifted. 

 

The Bobcat T550 was chosen partly because of its 93 possible attachments.  The standard loader bucket is itself an attachment that comes with the vehicle but it can be replaced with others.  Using attachments rather than importing additional vehicles for specialized applications is a weight and money saving strategy.  The following are the attachments that have highest potential value for early construction work on Mars:Ripper Attachment

 

 Ripper Attachment:  Use this device to tear up extra-hard ground where stones are buried under the regolith.  The ripper will bring rocks to the surface where they can be collected.  This is the first step of ground preparation for houses, roads and storage tanks.

 

 

Scarifer Attachment

 

 

Scarifier Attachment:  Use this to tear up moderately hard ground where rocks are at or near the surface of the regolith.

 

 

 

 

Tine Rake Arrachment

 

 

Tine Rake Attachment:  Use this in softened ground to collect rocks that are at or above the surface.

 

 

 

 

Hydraulic Rock Breaker

 

Hydraulic Rock Breaker: Use this to demolish a rock outcropping that protrudes above the surface in a location that must be utilized for construction. Its purpose is to break up the exposed rock to below-surface level and produce smaller rocks and shards that can be collected.  On Earth such a breaker would be hand-held by a worker that breaks up cement at a construction site (rat-a-tat-tat-tat).  On Mars this attachment will allow a colonist to perform the job from inside of an enclosed cab rather than inside a spacesuit.  A cab is more effective for this job.

 

Rock Bucket

 

Rock Bucket:  Similar to the tine rake, but the tines on this bucket are stronger and can penetrate the ground a little further.  It will also pick up larger rocks

 

 

 

Backhoe Attachment

 

Backhoe Attachment:  This will be used in relatively soft ground where hard rock outcrops will not be encountered.  It will be useful for excavating holes e.g. to construct a house or storage tank below ground level.  Also can dig trenches where water lines and pipe heater cable need to be buried.

 

 

 

 

 Industrial Grapple

 

Industrial Grapple:  This will be used to pick up a large rock or a number of rocks and carry them off the construction site.

 

 

 

  Pallet Forks

 

 

Pallet forks:  When building a stone structure, use this attachment to pick up a cut stone block and place it into position.  It will be useful for stacking and un-stacking building blocks at a quarry or at a construction site.  Small blocks will be placed between layers so that the forks can slide between the layers.

 

 

 

U.S. Truck ClassesDespite the weight advantage gained by using multiple devices on the same loader, there is also a disadvantage in lost efficiency.  Many tasks need to proceed simultaneously at a construction site and this can only occur when multiple vehicles and drivers are employed at the same time.  In addition, there is time lost in changing out the attachments when a different job is to be done.  Engineers assigned to planning the colonizing expedition will have to analyze the vehicles and attachments required for each construction job versus the weight of cargo to be shipped from Earth and its cost.  An optimum balance will need to be found.

Truck

After a front-end loader, the next vehicle to consider is a truck.  A small pickup truck will perform many useful jobs in a Mars village, such as transporting up to two people, delivering cut stones from quarry to construction site, or delivering equipment.  These items can be loaded and unloaded with a forklift attachment.  Note that the truck bed can be stacked much higher on Mars than on Earth because the bigger loads will weigh much less. 

For example, if the Gross Vehicle Weight Rating (GVWR) for a class one truck is 6000 lb. on Earth then it will be 15,800 Earth lb. when used on Mars.  We can (actually) install high side rails on a small truck and overload the truck bed hillbilly style. 

In the first few weeks after landing there will be no roads appropriate for a soft-tire vehicle and so a tractor-loader will carry material via the front-end bucket.  But soon roads will be long enough and cleared enough so that trucks can be employed.  The classes of commercial trucks that are employed in the US are shown in the table above.  The medium and large truck classes 4 through 8 will be too large to be transported to Mars in the first settlements, will have no highways to drive on, and will have no large loads to justify their use.  For these reasons the light duty trucks will be the most appropriate for Mars duty.  In the US today, however, there is declining demand for small trucks and many have dropped out of production. For example, the Ford Ranger listed in the table is no longer produced in the US.   The trucks employed on Mars will need to be converted to methane and a diesel engine is easiest to convert.  However, many of the smaller trucks that are readily available, such as the F-150, no longer offer a diesel engine option.   

Dodge Ram 1500At the present time, the smallest truck readily available with a diesel engine is the 2014 Dodge Ram1500 (7).   With the 3.0 liter EcoBoost diesel engine, the truck weighs just under 6000 lb., which keeps it in the Class 1 light duty category.  The 6-cylinder diesel optional engine is smaller than the well-known 5.7 l V-8 HEMI engine, but in the lower gravity of Mars it should have more than enough power. The Lone Star model can be acquired with a regular cab and a long (8 foot) box.  The payload capacity comes in at 1800 lb., which converts to 4700 Earth lb. when used on Mars.  

Converting a pickup truck for use on Mars will follow the same path as converting a front-end loader.  First, the cab will be made airtight by inspecting all 8 sides for protruding parts and holes.  It may be necessary to convert controls from mechanical to an electronic control unit (8) so as to help minimize the potential holes through the shell of the cab. The doors and windows must be sealed and the cabin tested for air leaks.   

The next step is to rebuild the roof to install a rooftop EVA hatch, same as the front end loader.  A hatch may be placed over the passenger side of the truck rather than the driver side so as to avoid hitting controls when entering through the roof.  Next, the engine will be adjusted to use methane fuel rather than diesel.  More space is available in a truck for methane and oxygen cylinders as they can be placed behind the seat or in a steel box on the truck bed, if necessary.  More space is also needed for the ECLSS equipment, but more space is also available than in a loader. 

A truck driver will need the same UV and GCR protection as a loader operator, so the same tinted windows and exterior visor will be required.  No loader bucket will be operating, so no movement is required of the visor and it can be made rigid. 

Some hauling jobs on Mars, such as carrying rocks and regolith, cannot be easily accomplished by a pickup truck.  Loading loose material into the truck with a front end loader is easy enough as long as the side rails are no higher than the reach of the loader bucket, but unloading efficiently requires a dump bed.Ram 3500 Tradesman

Among the small trucks that can be equipped with a dump bed, it is still the Ram line of trucks that offers a diesel engine as an option for easy convertibility to methane.  According to a local Dodge dealer representative (9) the smallest Ram truck that could accept a dump bed is the Ram 2500, but dual rear wheels should be used for the extra loading.  For a chassis cab with an 8-foot dump bed the Ram 3500 is recommended.  The Ram 3500 has a GVWR of 14,000 lb. so it is still considered a category 3 light duty truck, but the Dodge Company considers it a heavy-duty pickup.  The Chassis cab Ram 3500 Tradesman with the 6.7 l turbo diesel has a payload capacity of 6700 lb. except that the dump bed of unknown weight will be subtracted from this payload.  With the optional wheelbase of 140 inches it has a gross weight of 6600 lb. and a curb weight of 4849 lb., which does not include the dump bed and box. (10).  Conversion of this truck for Mars operations will proceed in the same manner as for the pickup truck, but with even more space for pressurized oxygen tanks, methane tanks and ECLSS equipment.  The dump truck will be useful for carrying raw materials but it is also large enough to carry the from end loader and other equip meant to more distant work sites. 

Crane

The method for building houses and storage tanks that are addressed on this website will allow construction projects to proceed with just a Mars-adapted front-end loader and a colonist in a space suit.  This strategic design minimizes the weight of equipment to be imported from Earth at high cost.  But for enhanced speed and efficiency in construction, employing a small crane will expedite the rapid expansion of the colonists’ village.  The crane should be of efficient design and minimal size yet large enough to perform the job.  The highest structures that are contemplated at this early stage of colonization are the peak of the Mars house and the tallest storage tank.  Without the regolith cover the peak of the Mars house arched ceiling will be 4.1 meters interior height and 4.4 meters exterior height (adding the depth of the building blocks) from ground level.  A crane’s reach must be high enough to lift a building block over this peak and lay it in place.  For storage tanks the height of the arched roof over the square tank will be 8.5 meters so the Spydercranecrane must operate at a height above this level.  However, the proper technique for wall construction is to place regolith next to the walls as they are built up. If raised solid ground is built up next to the walls as they are constructed, then the crane can operate from these higher levels as a new ground level.  In this case the length of the boom required will be much shorter.  If the base of the crane can operate from a level that is at the height of the walls then the minimum reach needed is only 2.5 meters at a distance of about 3 meters from the center of the structure.

One piece of equipment that meets these requirements is the Spydercrane, built by the Japanese firm Furukawa Unic.  Five models of the crane are offered, the smallest being the URW 295 Mini Crawler.  The Mini Crawler boom and four outriggers (legs) fold up into a compact rectangular unit just 2 feet wide by 9 feet long.  This unit rides on a set of tractor treads and can be moved through a standard (Earth) house door. The compactness of the unit could be useful tp minimize the space required on the Colonial Transporter importing equipment from Earth.   However, it still weighs 4425 lb. on takeoff. (11)

 Fifth Stage Extended

The URW 295 has a maximum reach of 29 feet when all five of the boom extensions are employed. When operating at this boom length and at 4.6 feet from the base of the boom, it has a rated capacity of 6250 lb.  The actual working capacity is less and depends on the working radius, the boom swing from the center to the left or right, and the number of extensions of the boom that are employed.  The chart above spells out the working load capacity with all five stages of the boom extended.  Under the poorest conditions of working radius and angle the minimum load capacity is still 135 Earth lb., which corresponds to 355 lb. on Mars.  The house arch building blocks are 62 lb. Mars weight, which lies easily within the capacity of the crane; therefore the Spydercrane can handle all the construction requirements of the first stage of colonization. 

The Mini Crawler Crane Model URW295C1URS is powered by an optional diesel motor, which means it would be relatively easy to convert to methane.  It also can be operated remotely which means that a colonist inside an MEV can operate it, thus reducing the time spent in a spacesuit.  One problem in the design of this crane is that it is built close to the ground.  The tractor treads could not negotiate a sudden change in slope without a portion of the body dragging the ground.  To ameliorate this problem, the ramps leading up to the crane’s operating position will be built with gradually changing slopes so as to mitigate this limitation.  On the other hand, each of the outriggers can be independently adjusted so that the machine can accommodate ground that is not perfectly flat i.e. it can operate from a moderately sloping ramp. 

MUV

An MEV that is a utility vehicle must inevitably be called an MUV. The Mars Utility Vehicle will be an extra-lightweight personal transporter with the capability to carry out small jobs using manipulators on the exterior of the cab.  It will also sport a small exterior cargo space like a mini-pickup. It will be the “errand-boy” of the MEVs.  It is a vehicle that has no direct analogue on Earth but draws upon R&D work of NASA, especially the SEV shown at the beginning of this article and FlexCraft. (11)(12).

FlexCraft Flexcraft was designed as an alternative to a space suit for EVAs in outer space to make repairs on the exterior of a spacecraft such as the ISS.  FlexCraft is self-contained like a spacesuit, having its own ECLSS equipment.  The driver/astronaut controls manipulator arms on the exterior of the vehicle to conduct his work, only much easier than manipulating the arms of a spacesuit.  The biggest advantage of the craft is that it uses the same atmospheric pressure and O2 level as the habitat where the driver is based, so he can enter directly into the craft.   This saves a considerable amount of time that could be misspent in pre breathing exercises.  This concept was adapted for the use of colonists in the Mars village vehicles where colonists will enter directly into the vehicles through top-hatches.  Originally, the plan was to have one FlexCraft to drop into any if the MEVs, but further investigation revealed that each vehicle will be quite different in configuration and will need different adaptations to work on Mars.  The top entry hatch, however, will be common to all vehicles.

 

 

Golf CartTo develop an MUV, start with the shape and size of an enclosed golf cart.  One appropriately shaped cart is the two-person Eagle electric vehicle built by Suzhou Manufacturing Co. in Jiang Su, China.  Note the large, nearly vertical front window, which will provide a good view of the manipulator arms and any object in the gripper hand.  These will be mounted on the front engine cover just above the headlights.  Controllers for the manipulators will be placed on the passenger side of the cab because this is where space is available on the dashboard.  The Suzhou Eagle does not provide an appropriate body structure but one can be built in this general shape.  Rather than converting an existing Earth vehicle, one can be built from scratch.  The window area could be designed to be even larger, like the SEV shown at the beginning of this article.  Like the other village vehicles, it must have an airtight insulated cab; it must have a top-hatch for entry; it must be self-contained with its own ECLSS equipment for short EVAs; and it must provide the same UV and GCR  (visor) protection as the other MEVs.  The engine will be powered by methane and it should carry a small trunk attached to the rear for tools and small equipment items.  A trailer of modest size could enhance its usefulness even further.  While the MUV will be very desirable within the village, the road network will expand and construction sites will be located further from the base.  In outlying areas the larger vehicles will be in greater demand than the MUV.  

Garage

On Earth, an attached garage is a convenience and a luxury.  On Mars it will be a necessity for the proper operation of MEVs and MUVs and for the safety of colonists who will operate them.  Operating a methane fuel combustion engine will be analogous to operating a diesel engine in Alaska, or worse.  The motor must be kept warm enough at night to allow the engine to start up in the morning; this is accomplished by placing an electric blanket or heater over the engine or over particular components during the night.  Grease-bearing or oil-bearing parts and various seals and gaskets must also be kept reasonably warm.  At minus 50 to –minus 80 degrees C the nighttime temperatures on Mars will not be reasonable. A garage will be required to moderate these extreme sub-zero temperatures.

Another function of a Mars garage will be to provide easy access to a vehicle from a house.  Going outside to a vehicle without a spacesuit is not an option, since any exposure to outside temperature and pressure leads to extremely unpleasant results.  The solution will be a garage that provides passage from a climate-controlled house to a climate-controlled cab with no intermediate step. Suitable garages will be built from stone blocks using the same techniques employed in building a 4-way house intersection, as described in the article “Pioneer House Building.” 

The sketch below shows a side view of an intersection room attached to a Mars house at a right angle.  (An end view would show the same arched ceiling over the structure.) The intersection room us attached to a row of four garages with four MEV entrances facing the viewer. Each garage structure is subdivided into a garage proper and an attic above it. Each garage and attic will be 4 m width by 4 m depth, the same as an intersection room. The garage, however, will have another structure built within it that is the same shape but slightly smaller.  In fact it will be exactly 360 cm wide to allow two 30 cm thick inner sidewalls to be placed next to the outer sidewalls. The inner walls will support another arched ceiling that is high enough to accommodate the MEV to be parked beneath it.  

 MEV Garage

The attic space will be constructed over the garage by first filling the space above the inner ceiling with rock and regolith. This fill dirt will be thoroughly tamped to establish a flat floor of compressed regolith. Then the floor will then be covered by stone tiles. Openings for passageways will be left in the walls between the intersection room and the first attic and between each attic compartment.  An opening will also be left in the floor of each attic where the MEV access tube will be installed. Sintering the floor tiles may not be necessary because the surrounding wall will provide an airtight enclosure.  The tiles around the access tube may be sintered or mortared just to add strength to the floor where traffic will be heavy.

Each garage entrance will entail a wall with a Roman arch opening that is smaller than the interior of the garage. (Thus requiring an additional scaffold of smaller dimension just for this wall opening.) This will provide a flat wall surface around the entrance but still plenty of space for an MEV to drive into the garage. A roll-up/roll-down door will be mounted on the outside face of the garage entrance and it will be operated by remote control, just like a garage door on Earth. 

Note that each MEV access tube must be designed with a foolproof closure so that it is airtight when not in use. When the MEV enters the garage, a special procedure will be required to connect to the access tube. The approach and attachment will be analogous to a spacecraft approaching the ISS and connecting to a port. The MEV will require a computer program to drive it accurately and to make the connection.  A colonist inside the cab or inside the attic will have his vision obstructed and will not be able to do it.

Also note that the intersection room and four attics will comprise an airtight space that is shared with the attached house.  The daily traffic of colonists coming and going from vehicles represents a higher accident potential in this airspace because of frequent connecting and disconnecting to MEVs. A good safety measure will be to employ an airtight portal between the house and this intersection room, rather than the passageway shown in the sketch.

The four garages shown in the sketch will accommodate two front-end loaders, a truck and an MUV. This could be a reasonable load for the first shipment of equipment from Earth. As the colony expands, additional garages will be constructed as attachments to the existing row of garages. A long series of garage attics will be joined together with just one access passageway from a house, thus minimizing the number of airtight portals required.

Summary

Upon landing, colonists will unload the vehicles and equipment they require to begin building a Mars village.  Highest priority will be given to a front-end loader and selected attachments.  After that, a truck will be needed as well as a utility vehicle to use within the village.  A small crane will speed construction and a dump truck will expand the types of construction that can be accomplished. An MEV garage will be built to protect vehicles against excessively low nighttime temperatures and to provide an airtight passageway from a house to an MEV.

 

References

 

(1) “NASA’s SEV:  Spacecraft for Asteroid Missions Revealed”, Space.com Nov 12, 2012, Retrieved 4-14-2014 from http://www.space.com/18440-nasa-space-exploration-vehicle-photos.html.

(2) “Deep Space Habitat News and Features’” NASA.gov, Retrieved 4-14-2912 from http://www.nasa.gov/explorat”Deep space habitat ion/technology/deep_space_habitat/.

(3) “Space Exploration Vehicle,” Wikipedia, Retrieved 4-14-2014 from http://en.wikipedia.org/wiki/Space_Exploration_Vehicle.

(4) Bobcat Company (Undated), “Compact Tract Loaders Specifications and Features”

(5) Enbridge Gas Corporation (Undated), “Components of Natural Gas” Retrieved 4-14-2014 from https://www.enbridgegas.com/gas-safety/about-natural-gas/components-natural-gas.aspx

(6) “ISS ECLSS” from Wikipedia, Accessed 4-22-14

(7) “2014 Dodge Ram 1500 EcoDiesel V-6,” Cara and Driver (2014) Retrieved 4-22-2014 from http://www.caranddriver.com/reviews/2014-ram-1500-ecodiesel-v-6-first-drive-review

(8) “Electronic Control Unit,” Wikipedia, Retrieved 4-24-2014 from http://en.wikipedia.org/wiki/Electronic_control_unit

(9) Nichols Dodge Chrysler Jeep, Burlington, N.C.  4-24-2014.

(10) “Spydercrane URS 294 Mini-Crawler Crane Technical Specifications,” www.spydercrane.com”, Accessed 4-25-2014.

(11) Brand Griffin, “Benefits of a Single-Person Spacecraft for Weightless Operations,” 43rd International Conference on Environmental Controls, AIAA, 2012.

(12) Brand Griffin, Charles Dischinger, “Low Cost Space Demonstration for a Single Person Spacecraft.” 41st International Conference on Environmental Controls, AIAA, 2011.

(13) http://golf_cart.china-direct-buy.com; Accessed 4-28-2014.