Housing

            The considerations of where the crew was to live involved many factors.  It was not possible for them to remain in the ships.  Confinement in those close quarters for two years would be psychologically disastrous.  It would also be detrimental to the scientific work to be preformed.  The equipment could not be fully utilized or isolated from human contamination.  The space in the module just would not allow for this; therefore, housing was a requirement.  Several possible concepts of the type of housing that would work in Martian conditions were brought up.  Only three of these had any semblance of feasibility.  The considerations that went into choosing the housing are seen below.

 

Underground Housing

PRO                                                                             CON

1.      Most efficient radiation shielding                                1.  Very labor intensive considerations

      per thickness                                                                -reinforcement

2.      Can handle greater internal pressurization                       -equipment

      to external pressure                                                      -lining of walls and room separation

3.      Has low heat transmissibility                                     2.  Location to dig into or have to

4.      no wind profile for it to be a design factor                         reinforce

5.      stability in strength of housing due to                         3.  Climate controlling

      being in rock and reinforced.                                     4.  Pressurization hatch on carrying

                                                                                         equipment up to surface and locking  

                                                                                         mechanism to ground and seal

5.   transport space for thereinforcement and the equipment

6.      conducive to claustrophobia

7.      separation of laboratory from living quarters

8.      location of electrical and plumbing

9.      stability in case of collapse, less likely to get out

10.  vehicle location if need shelter from sand storms

11.  weight of the material needed

12.  acoustical problems of the cavern

 

 

Pop Up Dome

PRO                                                                             CON

1.      easier to assemble than cave                                    1.  Computability less than for cave but

2.      climate control can be built into the walls                       still bulky compared to full assembly

     -air circulation                                                           2.  Uncertainty of how will react to

3.      pressurization hatch is easier to work with                      higher internal pressurization

4.      connected expansions to other dome possible            3.  Location, need level ground

5.      hydroponics growth, access to sunlight                           -anchoring to ground

6.      psychological implications can see outside                4.  Effective radiation shielding

7.      electrical wiring, plumbing hidden in walls                       concerns

8.      separation of lab for controlled conditions                       -additives, foam, plastic

9.      stability if falls will be outward and lighter                   5.  Heat transmissibility, energy

10.  shield vehicles from the sand storms as                         requirements

      a break                                                                   6.  Collapse due to stresses on structure

7.      rigidity inherent to structure

8.      total weight

 

 

 

 

Constructed Dome

PRO                                                                             CON

1.      climate control location                                             1.  Need some skill to assemble

     -air circulation                                                                sections and joints

2.      electrical wiring location in the dome siding                     -same labor intensity as other dome

     -plumbing as well                                                           after frame made

3.      pressurization hatch easy entrance and                     2.  Adequate radiation shielding

     inclusion                                                                  3.  Heat transmissibility of material

4.      hydroponics possibility with access to sun                 4.  Location for building

5.      more compatible than others                              -anchoring

6.      psychological problems of claustrophobia                        -ground being level for building

7.      expandability in linking with other dome                     5.  Will withstand positive pressurization

8.      separation of laboratory from living                             6.  Collapse from weight?

9.      stability will not fold inward, lighter                             7.  Weight for transport

10.  shield vehicles from sand storms

11.  rigidity when well constructed in linkages

From this it was decided that the geodesic dome was the best design concept available for the housing.  The design for the beams were considered based upon the pressurization that would cause tension, or compression that the beams might be subjected to due to weight.  The pressurization and the total weigh were analyzed to determine if that would create the greatest stresses upon the structure.  The stress caused by the pressurization was found by equation 1.  The pressure came from the chosen value based upon the physiological needs found in the Life support section.

 

                                                                                                                      equation 1

 

            Where   s is the stress caused by the loading,

                        p is the pressure in the structure,

                        r is the radius of the structure, and

                        t is the thickness.

 

The pressure (p) is 7.35 lb/in2, r is 17.5 feet, the thickness (t) is 5 feet for the maximum amounts.  The maximum stress that this would place upon the structure is 21.4 lb/in2.  The weight that would be applied to the structure was found by calculating the weight of the foam.  This was obtained by equation 2.

 

                                          equation 2

 

            Where   W is the maximum weight,

                        w is the weight per unit cubed of material,

                        V is the volume of the material occupies,

                        T is thickness, and

                        R is the radius of the surface.

 

The maximum weight was found to be 57726 pounds from this formula.  The maximum weight to any one section of the dome was found to be 420 or 225 pounds depending on if the length of the beams were 5 or 7 feet long.  From this the material from the beams could be chosen.  The material had to be light and strong and cost efficient enough to suit the criteria for housing.  Aluminum 7075 was the material that best met these needs.  From this the radius of the beams could be determined.  The safety factor that was placed upon the structure to ensure failure would not occur was 3.  The formula for finding the radius is shown in equation 3.

 

                                                        equation 3

 

            Where   r is the radius of the beam,

                        x is the safety factor,

                        P is the maximum load applied to the beam, and

                        s is the maximum allowable stress to be placed upon the beam.

 

The weight of the beams could then be found by multiplying the density of the material by the volume of the material.  The diameter was calculated for the different parameters found by the calculations.  The volume and weight for the accompanying radii are listed in Table 1.  These are for the varying dimensions of radius and lengths of beams used.  The weight of the material was found from a book (Dowling, pg.90), which when converted is .0974 pounds per inch cubed.

 

 

r=.0768 in

r=.902 in

r=1.06 in

5 ft (in3)

1.334

184

254.15

7 ft (in3)

1.779

245.38

338.9

w5 (lb)

0.13

17.92

24.75

w7 (lb)

0.173

23.9

33

W5 (lb)

13

1792

2475

W7 (lb)

17.3

2390

3300

  Table 1 – The calculation of the material and weights of the beams.

 

The joints were estimated at around 45 for a dome that was not upon risers.  The weight was estimated to be around 11.25 pounds for all of these. If more are required the weight will be greater than this.  This is only an idea to work with; however, so rough approximations are all that are required.  The theory behind the equations and the factors taken are more complex, but these are the results from them.  The material that would be laid down on top of the dome is a Kevlar or silicone fabric to spray the foam onto and support the weight of the foam between the beams.  These were chosen for their strength and durability, cost and weight will be the deciding factor.  When erected on the Martian surface the foam will have layers of sand interspersed within it to serve as a radiation blockage.