Project Columbus Equipment and Schedule
Project Columbus is named for the explorer of the Americas and is conceived as an international effort to land people on Mars in order to set up an outpost from which the Red Planet can be explored and studied. The plan assumes (1) the use of expendable commercial rockets capable of launching about 24 tonnes to low earth orbit such as the Ariane 5, Delta IV Large, and the Angara (this is the capacity of the Space Shuttle as well); (2) solar powered ion-propulsion vehicles capable of lifting cargo to (3) Gateway, an occasionally staffed space station located at the Lagrange Point (L1) between the Earth and the Moon; (4) chemical propulsion from Gateway to the lunar surface and Mars; and (5) use of hydrogen and oxygen propellant derived from the permanently shaded regolith at the lunar south pole. It assumes that the moon will be visited first, Mars second. Its ideas from various authors, but especially from Michael Duke’s “A Lunar Reference Strategy,” which can be seen at http://members.aol.com/dsportree/MM22.htm, and from Robert Zubrin’s “Mars Direct” proposal. It also utilizes technology from (Patrick J. G. Steinnon and David M. Hoerr, The Rocket Company, http://www.hobbyspace.com/ AAdmin/archive/SpecialTopics/RocketCom/chap01.html) and from a recent proposal from NASA’s NeXT Task Force proposing a station at L1 called Gateway (http://www.space.com/news/beyond_iss_020926-1.html). It assumes technology available near term (i.e., extrapolations of existing technology). One feature is the reusability of the principal transportation elements. Another is use of solar power instead of nuclear power.
1. SOLAR-ELECTRIC VEHICLE
(SEV), mass 8 or 9 tonnes
High-efficiency (30%) solar panels (1,200 square meters, 400 kw), ion engine (Isp, 3,000 seconds), avionics, etc. 3.5 tonnes
Tank 1 tonne
Propellant (xenon) 3.5 to 4.5 tonnes
Note: Deep Space 1 had a 2.1 kilowatt solar array and generated 4.5 km/sec of delta-vee by expelling 81.5 kg of xenon over 20 months. The spacecraft had a total mass of 486 kg and the ion engine a specific impulse of 3,000 seconds. Scaling up the solar array 200 times, 29 tonnes could be pushed to 3.2 km/sec in 5.8 months using a 400 kilowatt array. The ion engine would consume possibly as much as 4 tonnes of propellant. If 4.5 tonnes of propellant were available, 0.5 tonnes would remain to return the ion engine to low earth orbit for reuse.
I have no way to verify the mass of the engines and solar arrays except to note that Michael Duke said an 8-tonne solar-electric vehicle could push 16 tonnes of cargo to the Lagrange point, and one can verify the mass of propellant necessary, assuming a specific impulse of 3,000 seconds (the Isp of Deep Space 1) and assuming 50% gravitational losses. I have scaled up Duke’s vehicle about 20% because they described 24-tonne launches that always included a reusable solar electric vehicle, and did not discuss subsequent launches when the vehicle was already in orbit.
The SEV panels, ion engine, and avionics are launched first. Subsequently, the 24-tonne booster launches 4.5 tonnes of propellant and tanks and 0.5 tonnes of solar panels (to replace panels on the SEV that have degraded), and 19 tonnes of payload (half of which can be landed on Mars). If lunar-derived fuel is available at Lagrange 1, the payload could include as much as 14 or 15 tonnes destined for the Martian surface.
2. AUTOMATED CARGO VEHICLE (ACV), mass 19 tonnes (launched from Earth with 5 tonnes of ion engine propellant to push it to Gateway)
Fuel Tanks (cap., 4.0 tonnes LOX/methane) 0.3 tonnes
Engines (2, 20 tonnes thrust each) 0.8 tonnes
Parachute 1.0 tonnes
Heat shield/ACV base 3.0 tonnes
Legs 0.2 tonnes
Avionics 0.1 tonnes
Reaction Control 0.3 tonnes
Landing methane 0.8 tonnes (delta-vee, 800 m/sec)
[Landing oxygen from moon 2.8 tonnes]
Cargo (Martian surface): 12.5 tonnes
Cargo (Mars orbit): 15.5 tonnes
Cargo (Phobos/Deimos): 14.0 tonnes
Trans-Mars injection (TMI) is supplied by a Lifter. Methane for landing comes from the Earth; liquid oxygen from the moon or Phobos and is supplied to the ACL at Gateway. ACLs follow a Hohmann trajectory to Mars.
Delta-vee, Lagrange 1 to Hohmann transfer orbit, plus course corrections: 0.8 km/sec (mass ratio, 0.25:1 for methane)
Delta-vee, Mars landing: 0.8 km/sec (mass ratio, 0.25:1 for methane)
Note: NASA is currently developing a standard “platform” for landing scientific packages of up to about 1 tonne on Mars called the “smart lander.” The ACL could be a twelve-fold expansion of that vehicle.
Once an Outpost is well established on Mars the lander version is phased out, because the Mars Shuttle can deorbit cargo.
3. INTERPLANETARY HAB (Ihab), mass 16 tonnes
Cabin structure 4.0 (1 tonne more than ERV cabin)
Life support system 2.0 (1 tonne more than ERV cabin)
Consumables 3.4* (for six months only)
Electrical Power (10 kw) 1.0* (assumes more powerful solar arrays)
Reaction control system 0.5*
Computers 0.1*
Furniture and Interior 0.5*
EVA suits 0.4*
Spares and Margin 2.3 (0.1 tonnes more than the Mars Direct
ERV, to make the total 16 tonnes)
Aeroshell 2.4 (0.6 tonnes heavier than Mars Direct)
(* = numbers from ERV in Robert Zubrin, The Case for Mars, p. 92)
The Ihab is about half way between the Mars Direct’s Hab and its ERV cabin in mass and volume. It is a cone with a 6-meter basal diameter and a height of 13 meters. It has five floors with 28, 23, 16, 9, and 3 square meters respectively (total, 79 square meters). Its interior volume is about 183 cubic meters. The base is covered by a heat shield ten meters in diameter. Its long, thin shape is ideal for rotation to produce artificial gravity when docked to a counterweight (if docked to a Mars shuttle or another Ihab, 5 rpm will produce slightly less than Mars normal gravity [0.36] on the bottom floor)(4 rpm gives 0.23 gravities).
The Ihab can be launched into low earth orbit with an 8-tonne SEV that pushes it to Lagrange 1 over six months, or it can be launched with 3 tonnes of extra consumables (for the surface) and 5 tonnes of SEV propellant if an SEV is already in orbit. A Lunar-Based “Lifter” or a Mars shuttle pushes it to Mars. The shuttle and Ihab remain docked and serve as a counterweight to each other for the generation of artificial gravity. The IHab aerobrakes into a high Mars elliptical orbit and remains there untended 18 months. The crew returns from Mars and heads back to Earth using fuel manufactured on the Martian surface. The Ihab aerobrakes into Earth orbit, is refurbished and resupplied (it needs perhaps 5 tonnes of new stuff for each flight), and is flown back to Mars two years later.
Delta vee from Gateway to fast trajectory to Mars: 1.2 km/sec (mass ratio 0.33:1 for LOX/LH2, 0.4:1 for LOX/ methane)
Delta vee from high Mars orbit to fast trajectory back to Earth: 1.5 km/sec (mass ratio 0.5:1 for LOX/methane)
Some Ihabs are accompanied by a Docking Cube, an inflatable cubical structure two meters in diameter with a docking port on each of its six faces. Its total mass is one tonne and it allows up to six vehicles to dock together. The cube allows large complexes to be flown to Mars including up to four Ihabs and two shuttles.
Note: Various stripped down versions of the Ihab are possible since the structure is only 4 tonnes, life support 3 tonnes, and other essential features 1 tonne. Thus two stripped down Ihabs could be flown to Mars to provide additional housing on the flight out and could be left on the moons to provide emergency shelter. Later they could be refurbished and flown back to Earth if needed. A version of the Ihab could be used as a passenger vehicle between the Earth and moon.
4. MARS SHUTTLE (MS), a reusable piloted or automated passenger or cargo spacecraft
Crew Module 4.0
Structure 10.0 (plus 2 tonnes parachutes)
Aerobrake variable (typically 6 tonnes)
The Mars shuttle has a 6-meter basal diameter and is 16 meters high (three meters longer than the Ihab). Its aerobrake is sized to place 40 tonnes into high Mars orbit from interplanetary space (15-tonne vehicle including crew module, 12 tonnes cargo, 13 tonnes landing fuel without parachute; 15-tonne vehicle, 2 tonnes parachutes, 15 tonnes of cargo, 8 tonnes of landing fuel with parachute).
The Mars Direct ERV’s structure weighs 4.5 tonnes (Case for Mars, p. 92) and contains about 110 cubic meters of fuel storage volume. The ERV mass includes a heat shield and parachute for landing the crew cabin on Earth, but not for landing the entire vehicle on Mars. It includes engines for two stages, a cargo hold (probably about 10 cubic meters), and extra tanks for water (10 cubic meters). Thus the vehicle has a mass of 4.5 tonnes/140 cubic meters = 0.0321 tonnes per cubic meter.
A proposal for a two-stage reusable shuttle to low Earth orbit (Patrick J. G. Steinnon and David M. Hoerr, The Rocket Company, http://www.hobbyspace.com/ AAdmin/archive/SpecialTopics/RocketCom/chap07page2.html) has a structural mass for the second stage of 5.9 tonnes, including heat shield, parachute (7% of the total, with a redundant duplicate also massing 7%), landing wheels (1.5% of total), and more powerful engines than the Mars Shuttle needs. It uses 39 tonnes of liquid hydrogen and oxygen, which require a volume of 103 cubic meters, and has a cargo hold with a volume of 31 cubic meters. The two vehicles thus appear to be almost identical in size. They also appear to be about the same diameter and length. If one subtracts the parachute mass and the gear for a runway landing from the terrestrial shuttle, the remainder is 5.0 tonnes, in excellent agreement with Mars Direct’s vehicle (this totals 5 tonnes /134 cubic meters = 0.373 tonnes per cubic meter). It is assumed no additional heat shield is needed for Mars landing, but that additional mass is needed for aerobraking into orbit around the Earth or Mars because of the higher velocities involved.
The Mars shuttle’s fuel occupies 181 cubic meters. The vehicle also includes a 70 cubic meter cargo compartment (6 meters in diameter; 2.5 meters high; 28 square meters of floor space) in its base, above the engines and below the fuel tanks. The door folds down to provide a ramp to the ground. The top of the vehicle features a docking mechanism and a “capsule” 2 meters high and 1.5 meters in diameter (4 cubic meters) with a docking mechanism on top (which can be used as emergency astronaut accommodation); an inflatable tunnel can be attached to the outside of the vehicle to give access to the cargo hold from the capsule during interplanetary cruise. The total of 255 cubic meters at 0.0373 tonnes per cubic meter gives a mass of 9.5 tonnes (here rounded to 10 tonnes, to provide margin). If parachutes are employed in landing, one must increase this by about 2 tonnes.
The crew module is placed in the cargo compartment if the vehicle is to be flown with crew. For details, see crew module below. The crew module includes space for cargo.
Landing delta-vee with parachute system: 0.7 km/sec (mass ratio 0.25:1 methane)
Cargo capacity (down): 16 tonnes
Landing delta vee without parachute: 1.5 km/sec (mass ratio 0:5:1 for methane)
Cargo capacity (down): 15 tonnes
Delta-vee to Ihab: 5.4 km/sec (mass ratio 3.5:1 for methane)
Cargo capacity up: 20 tonnes (fuel needed by Mars shuttle and Ihab for trans-Earth injection)
Fuel consumption, up: 130 tonnes
Cargo capacity up (using 150 tonnes of fuel): 25 tonnes (with crew compartment); 30 tonnes (no crew)
Delta-vee to low Mars orbit: 4.2 km/sec (mass ratio 2.1:1 for methane)
Note: delta-vee to Phobos and to the Ihab are about the same, which means a fully fueled Mars shuttle could fly to Phobos with 3 tonnes of cargo, conduct exploration or maintain equipment, then return to the surface with 2 tonnes of cargo.
Note: The Mars Shuttle always lands with a parachute the first time. If the parachute cannot be repacked and reused (which is probably the case), subsequent flights require landing delta-vee of 1.5 km/sec. Subsequent flights are dependent on use of Martian water to make fuel.
To make 155 tonnes of LOX/methane on Mars (130 for the flight to the Ihab and 20 to push the shuttle and Ihab back to Earth) requires 7.75 tonnes of liquid hydrogen and about 50 kilowatts of power over two years (about 75 kilowatts over 18 months).
Once large quantities of water become available on the Martian surface (30 tonnes per year or more) the 10 tonnes of feedstock hydrogen flown up from Earth is replaced by cargo.
The Mars Shuttle carries the crew from the Ihab in high Mars orbit to the surface and returns them to the Ihab eighteen months later. The Shuttle brings up the 20 tonnes of fuel necessary to push both back to Earth. The Mars Shuttle remains at Mars through two oppositions, then returns to Earth to be refurbished. It is capable of up to five or six round trips.
The novel Mars Frontier assumes that two shuttles and two Ihabs are flown to Mars each time and one is left as backup at each planet. This increases the crew flown (which makes the plot more interesting) and makes the mission safer.
5. MARS SHUTTLE CREW MODULE (CM), mass 4 tonnes
The crew module is an inflatable structure that fits in the Mars shuttle’s cargo compartment (28 square meters; ¼ the size of the Mars Direct’s hab, half the size of the ERV cabin). It has one side where all its equipment (electronics, stove, toilet, airlock) is located. The rest of the structure can be deflated and pressed against that side, so that it can be removed from the cargo compartment (furniture and possessions must be removed first). Some cargo can be stuffed into the deployed CM as well.
The CM is normally meant for 2-4 weeks of use, but in an emergency, with the proper supplies, can be used for six months.
6. LIFTER, A-CLASS.
Dry mass 2.1 tonnes (excluding aeroshield)
Maximum LH2/LOX capacity 16 tonnes
Maximum methane/LOX capacity 36 tonnes
Lifters are any automated vehicle that lifts mass from an airless world to orbit or returns mass to that airless world (such as the moon, Phobos, and Deimos). Their propellant area is 4 meters in diameter and 4 meters long. The cargo hold is below the tanks and above the engines, is 3 meters high and 6 meters in diameter, and includes a ramp for easy offloading. They can fly from the lunar surface to Gateway, pick up a maximum of 12 tonnes of cargo, and bring it to back to the moon. All are designed to use methane and oxygen propellant as well as hydrogen and oxygen. The later Lifter-B model (dry mass 4.3 tonnes) has a fuel capacity of 34 tonnes (methane/LOX, 76 tonnes). Lifters are designed for ten round trips from the lunar surface before they must be replaced. They are named for lunar maria (Serenitatis, Tranquillitatis, etc.).
NOTE: The Centaur upper stage has a total mass of 22.8 tonnes and a dry mass of 2.0 tonnes (8.8% of total); the Delta IV Large second stage has a total mass of 30.7 tonnes and a dry mass of 3.5 tonnes (11.4% of total). The Lifter-A dry mass is 10% of the total plus 0.3 tonnes for cargo accommodation and landing gear. The Lifter-B is 212% larger.
Delta-vee, lunar surface to Lagrange 1 Gateway (or back): 2.3 km/sec (mass ratio 0.64:1)
Launch capacity to Mars (10 tonnes LH2/LOX, Hohmann): 50 tonnes including itself; 46 tonnes with return of the Lifter to Gateway.
Launch capacity between Gateway and lunar surface (16 tonnes fuel): 12 tonnes
Launch capacity from low Earth orbit to Lagrange with 12.9 tonnes of LOX/LH2: 9 tonnes (plus 2.1 tonne vehicle)
Launch capacity: 24.6 hr elliptical to earth via Hohmann with aerobraking: delta-v, 1.2 km/sec (mass ratio 0.4:1), so: Lifter-B takes off from Phobos with 35.4 tonnes methane and 13.6 tonnes LOX (49.0 tonnes total, plus 5 tonnes vehicle and 5 tonnes aerobrake), tops off tanks at the 24.6 hr orbit, then heads for Earth, arriving (after aerobraking) with 31 tonnes of methane. This requires 108.5 tonnes of oxygen, making 139.5 tonnes propellant at Gateway. Vehicle arrives with 0.4 tonnes spare oxygen as well.
Lifters are designed to be good for ten round trips between the lunar surface and Gateway (delta-vee, 4.6 km/sec per round trip). They remain at Mars three oppositions, then return to Earth for refurbishing.
7. INFLATABLE SURFACE HABITATS, diameter 12 meters, height 7 meters. The habitat is shaped like a flying saucer; the central section is a cylinder 12 meters in diameter and 2.2 meters high with hemispherical top and bottom caps up to 2.4 meters high each. Floor area of the main level: 113 square meters. The basement and attic levels have about 55 square meters each with headroom. Their crawl spaces (another 58 square meters each) are excellent storage areas.
Structure 8 tonnes
Life support 3 tonnes
Equipment, furniture 1.5 tonne
TOTAL 12.5 tonnes
The Mars Direct’s hab has a mass of 9.5 tonnes (structure, 5.0 tonnes; life support, 3.0; lab equipment, 0.5; furniture and interior, 1.0) and a floor area of 100 square meters. The Mars Direct’s ERV cabin has a mass of 4.5 tonnes (for the same items) and probably has a floor area of about 50 square meters, but has life support equipment for only six months. The Habitat is about twice the size of the Mars Direct Hab, but it is inflatable and does not have micrometeoroid protection, so its mass is 160% more. Its life support equipment can accommodate four persons; if more are housed, more mass is needed.
The Habitat houses 6, 8 in an emergency. If the upper and lower levels are used, it can house 10-12.
Note: Michael Duke assumes an 8-tonne habitat for his lunar transportation system.
8. GREENHOUSE, mass 4 tonnes
A greenhouse is an inflatable transparent structure of tough, transparent plastic (Kevlar, Nomex, Tefzel, etc.), six meters wide and 22 meters long, 132 square meters in surface area. They can be docked to inflatable structures (habs, for example) at either end. The structure itself masses 2 tonnes; the other 2 tonnes consist of air circulation and purification equipment, insulation/reflection blanket, motors to raise and lower the blanket, hoses, agricultural testing equipment, and a small quantity of fertilizer. The floor of the greenhouse is covered with recovered parachute material; walls of rocks are used to make raised beds for agriculture. The beds are filled with treated Martian soil in order to raise crops. It has airlocks at each end. At night a thermal blanket covers the inside of the arched transparent surface to hold in heat. At dawn the thermal blanket on the eastern side is lower to admit sunlight; the thermal blanket on the western side has a silvered inner surface to reflect horizontal solar rays downward onto the crops. During midday the thermal blankets are removed from both sides. In late afternoon the thermal blanket on the eastern side is raised and its silvered inner surface reflects the western rays downward onto the crops. By capturing solar energy that the plants would have otherwise missed, total solar insolation is raised to levels similar to those found on the Earth’s surface.
Each greenhouse should be able to treat the wastes and feed 1.5 to 2 people.
9. SOLAR POWER ARRAY
Each automated cargo lander is accompanied by two rolled up solar power arrays 4 meters wide and 32 meters long, having a mass of 500 kilograms, and capable of generating an average of 6 kilowatts of continuous power. After landing, a remotely controlled rover clears boulders from the path of the array; a ramp is lowered to provide the array a way to the ground; then a pump inflates a hose in the array with Martian air, causing the hose to stiffen and unroll the array. Every lander comes with a 1,000 meter, 200-kilogram power cable that the remotely controlled rover can pull to the nearest lander, thereby plugging them together. The rover can also blow eolian dust off the arrays periodically to keep them clean.
10. SOLAR POWER UNIT
The solar power unit is a transparent plastic cylinder 32 meters long and 30 meters in diameter. Half of the diameter of the cylinder is silvered; the cylinder rolls on the ground to keep the silvered side opposite the sun so that the reflected sunlight falls on high-efficiency (32%) solar arrays on the opposite side of the cylinder. The arrays are 3 meters wide and receive 10 times the usual Martian level of insolation on them, which heats them to as much as 100 centigrade. The solar panels have a network of tubes running across their backs through which compressed Martian air is blown to extract the heat. The 960 square meters of surface area intercept 480 kilowatts of solar energy, producing 150 kilowatts of electricity and 150 kilowatts of thermal energy. Total mass, 1 tonne.
11. MOONLET FUELING PLANT
The Moonlet Fueling Plant (MFP) is designed to extract volatiles from the chondritic bedrock of Phobos and Deimos, process them into hydrogen/oxygen and methane/oxygen fuels, liquefy them, and store them. The initial system includes a 1-tonne docking pad (in the center of the landing vehicle), two 1-tonne drills (deployed on opposite sides of the pad, and able to swing outward a meter from the pad), a 0.5-tonne volatile processing plant (built into the base of the pad, including a sabatier reactor, electrolysis unit, cryogenic refrigeration unit, and a fractionation tower), 2.5 tonnes of solar arrays, and two 0.5-tonne rovers. The plants are accompanied to Mars by the Lifters that propelled them from Gateway.
The system lands on the moon near the equator on the side facing away from Mars (the poles do not receive perpetual sunlight; the side toward Mars suffers from regular solar eclipses). The lander sinks harpoons into the regolith, using bursts from the reaction control system to keep the lander against the surface. The arrays are like the ones deployed on the Martian surface, but are longer; they unroll and are able to generate 30 kilowatts of power. The two drills deploy and drill up to 100 meters into Phobos. A microwave generator is lowered down the shafts to heat the chondrite, causing it to break down and release water vapor and possibly carbon gasses. The water vapor is captured, electrolyzed, and stored; later some of it is injected into the shafts to heat the chondrite further. Excess oxygen injected into the shaft will react with the carbon-rich rock to make carbon dioxide; excess hydrogen will react with it to make methane. The super-cold temperatures inside Phobos (way below the freezing point of water) will cause water to freeze cracks in the regolith closed. The fuel production complex should be able to generate as much as 60 tonnes of fuel per year (less, if there are leaks from the shaft or other inefficiencies). The two rovers can explore Phobos as well.
Once the Lifter is full, it can take off (gently, so as not to damage the unit) and fly to the Ihab or anywhere else it is directed to. Full deployment of the fueling system may require astronauts.
12. SUNWING
Solar-Powered Flying Wing, 700 kg (180 square meters of wing surface covered by solar panels [average mass, 3.5 kg/sq m, so wing mass is 630 kg, average electrical output 9 kw], propellers, fuel cells, 70 kg). Cargo mass: 350 kg. Typical speed; 30 km/hr. Based on the already-flying Helios (and now crashed!), which has the same size and mass and has flown to 100,000 feet on Earth. The Sunwing has to be assembled by astronauts on the surface from sections because of the length of the wings. Future Sunwing-B and Sunwing-C models are twice and four times as large, respectively, with multiple sets of wings. Sunwing-D is a Sunwing-C with silane engines added.
Sunwing-D: Central pod two meters high, 1.5 meters wide, fifteen meters long, can accommodate 1,200 kg cargo or equivalent people (9). Has a bathroom; galley and ten seats; and cockpit (each airtight). The three sets of wings are thirty meters long from the central pod; first pair is at intermediate height and has three propellers each; second set of wings is low and has three landing gears each; third set is high. Wings are 4 meters wide on average. Total wing surface: 720 square meters. With 40% efficient solar cells on the top and bottom, wings can make a maximum of 180 kilowatts of power. Mass of Sunwing-D: 3 tonnes. Comes equipped with four silane engines able to double its power supply, allowing it to fly at 400 km/hr, allowing 6,000 km flights in 15 hours.
13. PRESSURIZED ROVER (VAN)
Mass, 2.5 tonnes. Extras: bulldozer blade (0.2), manipulator arm (0.1), rooftop crane (0.4) provisions (150 kg per person per month), internal fuel storage (0.5); dimensions: 4.5 meters long, 2 meters wide, 1.8 meters high (interior), 0.8 meter ground clearance. Solar cells on top and side can make 1 to 1.5 kilowatts (average of 1 kw during the day). Rovers utilize methane/oxygen fuel cells built into the chassis. They have six wheels, each with its own electric motor and regenerative braking system. The system requires 0.25 to 0.5 kg of LOX/methane per kilometer per tonne of vehicle.
Vans have a bathroom, airlock in the back. The bathroom and airlock share a common 1 meter by 2 meter space. The galley is built against the bathroom wall and has a microwave/toaster oven, two-burner stove, compact refrigerator, a tiny sink, and a water recycling system. There are two sets of bunk beds (with storage beneath the bottom bed and above the top bed). The top bed can be folded down to convert the bottom bed into a couch. Each bunk bed can be closed off, and a curtain can be drawn between the two sides to allow some privacy dressing. Each bunk bed has a porthole window as well. The front section has three forward facing seats that can be reversed to face backwards: driver’s controls on the left, a navigation station in the middle, and a science area on the right. Vans usually accommodate two crew, but can handle four in an emergency.
14. DOCKING CABIN
The Docking Cabin is an inflatable structure 3 meters wide, 3 meters long, and 2.5 meters high usually including an airlock (1 by 2 meters) in front and airlock doors on the back and the two sides. The docking unit can be mounted on an open rover that can be driven by a person, controlled remotely, towed as a trailer, or can drive itself slowly. The docking unit allows up to three vans to dock together to form a temporary “base.” It has its own life support system and can be used for emergency accommodation or as a day-expedition base of operations. Docking units can also be attached to the Outpost, allowing vans to dock to it. Other docking units serve as large airlocks to allow parties to enter or leave; they can serve as a spacesuit donning facility or as industrial units with chemical or metallurgical units docked to them. Mass, 1.5 tonnes without equipment. Life support typically adds 100 kg.