Lunar bases

Why the Moon?

  • Extend human presence to the moon to enable eventual settlement.
  • Pursue scientific activities – history of Earth, the solar system and the universe.
  • Testing technologies, systems, flight operations and exploration techniques for future missions to Mars and beyond.
  • Mining on the moon – rare earth elements (Eg : europium and tantalum)
  • Space tourism.

Hazards & Challenges:

Site Selection:

Advantages

  • Half the sky is continuously visible for astronomy
  • Cryogenic instruments can readily be operated

Disadvantages

  • Outside workspace in extreme contrast (light)
  • Practical problems regarding solar power

Environment:

Vaccum

  • Outgassing of oil, vapors, and lubricants from pneumatic      systems.
  • Detrimental to:
    – Astronomical mirrors
    – Solar panels
  • Increase in dynamic friction – fusing of drill bit to lunar rocks.
  • Blasting ( to loosen regolith for excavation) –  blast particles can travel large distances.

Severe temperature variations

  • Structural & Material Fatigue.
  • Structural sensitivity to temperature differentials between different sections of the same component.
  • Brittleness at very low temperatures.

Meteorite Impacts

No atmospheric pressure.

  • Habitats have to be pressurized (15 psi)
  • Raises concerns for decompression caused by accidental & natural impacts

Solar/Cosmic radiation

  • long-term, sustained low-level radiation.
  • As damaging as a nuclear weapon detonation upon extended exposure.
  • Exposed Lunar surface – 30 rem (annual) & allowable – 5 rem

1/6 g

  • Benefit – build less gravity-restricted structures.
  • Disturbing ground causes dust suspension – dust takes long time to settle and clings to surfaces.
  • Conventional equipments not suitable for low gravity.

Difficulty in construction

  • Importing building supplies from earth – costly.
  • Modular construction and minimum local fabrication for initial term.
  • Use of local materials – long term.

Possible Concepts:

Inflatable designs

  • Double  Membrane Inflatable
  •  Shaping the ground.
  •  Laying out the deflated str.
  •  Pressurize outer ring.
  •  Install airlocks /other.
  •  Spray structural foam in between double membrane.
  •  Pressurize inside.
  •  Lay floor over bags of compacted soil.

Erectables

  • Based on Modular  construction and expansion.
  • 2 parts
    -Building Blocks
    – Platform/Expansion
  • Components are sent into low -earth orbit – ease of assembly
  • Fitted with – living quarters, instrumentation, air locks, life-support systems, and environmental control systems.
  • Then shipped to moon.

Concrete and Lunar materials:

  • Water is scarce.
  • Sulphur  Concrete
    – Requires no water.
    – Sulphur readily available in Moon.
  • Use of Lunar regolith for shielding.
  • “Geotextiles” may also be made creating filmy materials to seal habitat interiors.

 Lava tubes:

  • Formed after lava flow from volcanoes.
  • Surface of Lava stream solidifies & molten rock inside drains away.

Advantages

  • Minimal construction would be required.
  • Lunar Lava Tubes are huge on the Moon.
  • They can be easily sealed and pressurized.
  • Natural protection from
    o Micrometeorite impact
    o High velocity blast debris
    o Radiation
    o Extreme temperatures ( – 180 Celsius to 130 Celsius)

Lava tubes- recent news:

  • Discovered by Chandrayaan I
  • 1.2 km long
  • Uncolasped
  • Near horizontal

Lunar Bases:: Structural Design

Structures in mind

  • inflatable structures
  • underground burrows inside ancient lava vents

Considerations:

  • žMicrometeorites
  • žsustaining terrestrial pressures
  • žusing locally mined materials
  • žoptimizes space

The key factors influencing structural designs of habitats on the Moon :

  • One-sixth terrestrial gravity.
  • High internal air pressure
  • Radiation shielding
  • Micrometeorite shielding.
  • Hard vacuum effects on building materials
  • Lunar dust contamination.
  • Severe temperature gradients.
  • easy  maintenance
  • inexpensive, easy to construct
  • compatible with other lunar habitats/modules/vehicles
Inexpensive construction :
  • Using lunar regolith
  • lunar concrete- structures may be formed from cast regolith
  • similar to terrestrial cast basalt
  • highly compressive and moderately tensile building components

Benefits of Regolith

  • very tough and resistant to erosion by lunar dust.
  • ideal material to pave lunar rocket launch sites
  • ideal shielding against micrometeorites and radiation.

Design Requirements:

  • Space for habitants
  • habitat height
  • Optimize functionality
  • space for equipment, life support and storage
  • Arches – major component for habitat design as structural stresses can be evenly distributed.
  • stability of the underlying material and slope angle would have to be made whilst building the habitat foundations.
  • The biggest stress on the “hangar” design will come from internal pressure acting outward, and not from gravity acting downward.
  • As the habitat interior will need to be held at terrestrial pressures, the pressure gradient from interior to the vacuum of the exterior would exert a massive strain on the construction. This is where the arch of the hangar becomes essential, there are no corners, and therefore no weak spots can degrade integrity.

Further structural Details:

  • By constructing a rigid habitat from cast regolith, the building blocks for a stable construction can be built.
  • For added protection from solar radiation and micrometeorites, these arched habitats could be built side-by-side, interconnecting.
  • Once a series of chambers have been built, loose regolith could be laid on top.
  • The thickness of the cast regolith will also be optimized so the density of the fabricated material can provide extra protection.
  • Perhaps large slabs of cast regolith could be layered on top.

Lunar Bases :: Infrastructure and Transportation:

Problems:

  • Reduced traction:1/6 gravity and the lunar soil make traction a problem just like [the Mars Exploration Rovers] Spirit and Opportunity on Mars one can get stuck easily or need to much power to get around.
  • Dust: Apollo experience shows that a lot of dust is levitated by wheeled vehicles. This dust is hazardous to machines and humans when breathed in.

Mechanical and health problems of lunar dust:

  • Vision impairment
  • Incorrect instrument readings
  • Dust coating
  • Loss of traction
  • Clogging of mechanisms
  • Abrasion
  • Thermal control problems
  • Seal failures
  • Inhalation
Transportation solutions:
  • Road
  • The vertical take-off and landing method
  • a lunar cable car
Roads:
  • Roads above the lunar surface using fused lunar regolith
  • They provide much needed traction
  • significantly reduce the amount of dust suspension

Drawbacks of the roads

  • They are enormously costly
  • may be very difficult to build.
  • requires enormous energies, which cannot be provided by solar power alone.
  • So an alternate form of energy would be required to perform such a construction.

The vertical take-off and landing method:

  • Rocket-powered take-off and landing produces vast amounts of dust.
  • But should there be multiple bases on the Moon, this might be a possibility

lunar cable car:

  • Totally avoiding contact with the surface, thus cutting down on dust and avoiding obstacles

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