Space Colonies & Why Build Colonies? Lunar Bases ! It isn’t so expensive – US military is many 100’s of billions $ a year ! Fewer casualties than war – 17 astronauts in 45 years of space Karen J. Meech, flight were lost Astronomer ! Humans have an “expansionist” spirit – Much more real estate! ! Valuable resources could be brought to Earth. Institute for Astronomy ! Enough solar energy to rid the world of oil dependency could be brought to Earth for less than the cost of the Iraq war ! Profitable: e.g. 1 Metallic NEO $20 trillion, 3He as a fuel . ! Maybe the time has not yet come, but someday we will need what space can provide Space Habitat Design Shielding – Radiation Protection Considerations ! Shielding characterization ! Aereal density, d [gm/cm2] ! Physiological Needs ! Total amount of material matters ! Shielding ! Type of material: secondary ! Ionizing radiation & particles 3 2 ! Meteoritic impact ! 1 Earth Atmosphere: 10 gm/cm ! Atmospheric containment ! ! = mass / volume ! What pressure needed? ! ! = mass / (area ! thickness) ! Psychological Needs ! What mix of gasses? ! ! = m/(ax) = d / x ! Environment stress ! Gravitational acceleration ! x = thickness = d / ! ! Isolation ! Why it is needed 3 ! Personal space ! How to do it Substance ! [gm/cm ] d / !" x [cm] x [m] ! Illumination / Energy 3 ! Entertainment Lead 8 10 /8 125 1.25 ! ! Aesthetics Food / Water Styrofoam 0.01 103/10-2 105 103 ! Space Requirements Water 1 103/1 103 10 Shielding Types – Active Shielding Types – Passive ! Enough matter between us & radiation ! Examples ! 8/72 flare " ! d = 280 gm/cm2 (0.35m Pb) ! 2/23/56 flare " ! d = 500 gm/cm2 (0.63m Pb) ! Magnetic shielding ! Plasma shielding ! GCRs ! HZE, p+, e-, #: charged ! Like charges repel ! Requires the most shielding (~1 m Pb) ! B field deflects charges ! 15 billion eV “well” " repels ! Depends on person category (Child-bearing HZE (radiation < 0.5 rem / yr) age, Pregnant, etc.) ! E threshold depends on B field ! Problems ! Aesthetics / practicalities ! Problems ! Shield generator: massive ! Need to shield s/c on ! How to enter shield? Get light in? approach (electronics) ! “cheaper” to have bulk shielding ! Chevron Shielding ! Plasma Instabilities ! Technology infancy What about micrometeoroids? Atmospheric – Constraints Station Atmosphere ! Carbon monoxide (CO) ! Pressure: 1 atm Composition ! 14.7 psi (~15 psi) ! Attaches to blood more readily ! Nitrogen (N2) than O " suffocation ! Earth Composition (sea level) – Partial pressures 2 ! Present in our atm ! Careful monitoring is required ! 20% O : 3 psi 2 ! Decompression susceptibility ! Carbon dioxide (CO ) ! 80% N2: 12 psi (dissolves in blood) 2 ! Breathing trigger ! Pressure constraints ! $P > 0.5 " “the bends” ! Low pressure easier to maintain ! Shuttle EVA – suits at 5 psi ! Serious environment hazards ! Requires less mass ($) ! Many organisms require N2 ! Incomplete combustion ! Speed of sound (poor at low P) ! Many bacteria make (“fix”) ! Cigarettes ! Skylab astronauts P ~ 0.33 atm N2 " present anyway ! Electronics ! Hard to hear beyond 5 m ! Helium (He) ! 1-2 < PO2 [psi] < 10-15 ! Too low " anoxia ! Does not dissolve in blood ! Use “Air” ! Too high " oxygen toxicity ! Heliox (deep diving) at 15 psi ! Pure O2 atmosphere " flammable ! Psychological issues ! Composition Constraints Gravity Essentials Artificial or Simulated Gravity ! Force exerted on Earth ! Rotational forces ! Coriolis forces 2 ! F = GMm/r = m ! acceleration F = m r %2 ! Higher rotation speed at ! Acceleration = 9.8 m/s2 (at surface) ! m = mass [human] equator (more travel dist.) ! Human requirements ! r = radius of rotation ! Moving pole ward " zones ! Loss of muscle tone of lower velocity ! Exercise not completely effective " electric stimulation ! % = angular velocity ! Effects ! Bone decalcification (1.6-2.7%/month) ! Results in fractures ! Motion sickness ! Circulation inhibited ! Limit speeds to 1-2 rpm ! Loss of red blood cell mass ! Earth-gravity " lg radius ! Hormone imbalances ! Plants & Geotropism ! Problems returning to normal gravity “We can adapt to zero-g. The problem is NOT doing so.” Satellite Rotation Psychological [rpm] – g-forces Requirements R [ft] 1.0g 0.5g 0.25g 0.1g ! Mass / size of colony 5 24.17 17.09 12.06 7.64 ! highly constrained 15 13.95 9.87 6.96 4.41 ! Personal space 25 10.81 7.64 5.40 3.42 ! Limit line of site view 50 7.64 5.40 3.82 2.42 ! Large overhead clearance 80 6.04 4.27 3.02 1.91 ! Space vistas 140 4.57 3.23 2.28 1.44 ! Easy Access to space 300 3.12 2.21 1.56 0.99 ! Sufficient Surface area 400 2.70 1.91 1.35 0.85 ! 40 m2 projected area 1000 1.71 1.18 0.85 0.54 Psychological Requirements Psychological Requirements ! Aesthetics ! Live plants ! Non-predictability (e.g. weather) ! Overcoming Isolation ! Natural lighting ! Transportation slow / expensive ! Day/night cycles ! Good telecommunication ! Diversity ! Entertainment diversity Single Torus Cylinder Sphere Dumbbell Habitat Design Habitat Parameters R = 0.9 km R = 0.9 km R = 0.9 km R = 0.9 km Mass [k ton] 150 42,300 3,545 380 Constraint Size Material Shape Surface area [106 m2] 2.1 60.3 10.1 2.5 Earth normal gravity – > 1 km radius N/A Any (rotationally Shielding mass [M ton] 9.9 23.3 46.7 33.5 low rpm symmetric) Low Mass Large if low ! & Low ! , high strength torus Atm mass [k ton] 44 14,612 1,930 85 high strength [Al, Ti] Vistas CR shielding N/A Plasma? Magnetic? any ! line sight [m] 640 10,740 1,790 732 Passive (high !) ! Fraction hidden 0.7 0 0 0.5 Earth Atm pressure N/A High strength Less mass (thick) Communication – longest 2.6 11.8 2.8 1.8 ! Fire hazard for small distance surface travel [km] curvature radius ! Comm ease torus, dumbbell Interior ! Health ! Openness Good Good Good Good Psychology Big Glass " vistas ! Population (67 m2/person) 10,000 820,000 75,000 10,000 ! view restriction [active shielding] Dumbbell, torus ! vista ! live things Any ! natural light ! lg surface area Cylinder, sphere Cylindrical Habitat Spherical Colony ! No direct outside vistas " passive shielding ok ! Day / night cycles – rotating mirror panels ! Natural illumination " strategically placed mirrors ! Large living area; line of sight not restricted ! No line of sight restriction ! This design requires active shielding Toroidal Habitats Torus / Banded Torus ! Passive / active shielding ! Detail showing sub-levels in ! Restricted line of sight banded torus structure ! Smaller surface area ! Less atmosphere needed Colony Locations Colony Location Comparisons Location Pros Cons ! Lagrange points LEO / GEO ! accessibility ! Deep in Earth’s gravity well ! Places where gravity forces be- ! radiation protection LEO ! atmopsheric drag (LEO) tween Earth, Moon & Sun balance ! no radiation protection GEO ! L , L , L " Quasi stable 1 2 3 ! Crowding ! Only stable in plane perpendicular to line between Earth-Moon L4 / L5 ! access • Not much closer to ! Moderate fuel needed for station- ! outside Earth’s gravity well resources keeping ! Out of near Earth Environ ! L4, L5 are stable ! Colony remains fixed to perturba- tions Moon ! resource access ! gravity well ! gravity for health ! Disadvantage of L2 ! Moon shields Earth from Mars ! gravity for health (better) ! distance transmissions – so need a relay ! resource access ! gravity well (bigger) ! some atm – minimal shield Earth # A Lunar Observatory – Lunar Base Construction Economics & Science ! First bases – concepts ! Astronomy ! Will not be like “Space 1999” ! Moon provides a stable platform ! Large vistas (glass) ! Site 100x darker than for LEO ! More like military bunker ! Pointing stability ! Much underground ! Excellent for radio / microwave (quiet) ! Take advantage of regolith ! Useful for long baseline interferometry ! Stages of development ! Manufacturing ! Transportation of basic materials via ! Site for hard vacuum experiments & OTV (orbit transfer vehicle) industrial processes ! Shielding first order of business ! Manufacture of space structures ! Exploration needs to remain near habitat in case of flares ! Lunar Resource extraction ! Or have “way station” shelters ! Role for Mars Exploration (base) ! Set up power production (solar?) ! Set up oxygen production Setting up Radiation Shielding Alternate Radiation Shielding ! Support for shielding could be an arch of heat fused regolith ! Supported during construction by inflatable structure ! Can have microwave sintered regolith ! Alternate scenarios ! make use of natural topography (lava tubes, mounds) ! Pre-fabricated structure ! Al girders brought up in OTV ! Load regolith onto floor panels & raise with pneumatic lift ! Place supporters underneath ! Regolith to a thickness of a few m ! Entrances to lunar surface via overlapping radiation barrier walls ! Construct pressure structures underneath (pre-fab inflatable domes) Space Station modules? ! Standard ISS modules will not support over burden of 2 m regolith ! Even in 1/6 gravity ! Need re-design ! Need regolith for radiation shelter Mars Colonies Mars – Earth Comparison ! Why go to Mars ! Search for Life Condition Earth Mars Comment ! Most likely place for terraforming Gravity 1 g 0.4 g ! Stepping stone for asteroid resources Land Area 1.5 x 108 km2 Same as Earth No Oceans ! Stages Rotation period 23h56m 24h35m ! Space station & HLLV development ! Lunar resources Obliquity 23.5o 25o Seasons similar ! “Practice” on the Moon? Atm composition N2 [80%], O2 CO2 [95%], N2 ! Mars geochemical reconnaissance Atm pressure 1 atm 0.006 atm Varies seasonally ! Transport to Mars Atm protection Yes Almost none UV, CR unhindered ! 8-9 mo duration ! Can’t