Lunar Architecture

Introduction

The architecture used on Luna will be quite different from that used in terrestrial applications. Lower gravity, high vacuum, radiation, meteorites, moonquakes, and dust control will all play large parts in the design of lunar structures. Due to this, a large number of architectural designs have been put forward for human rated habitats on Luna.

Major Design Criteria

Atmosphere

Any lunar habitat designed for human use must provide a breathable atmosphere and maintain proper carbon dioxide, temperature, and humidity levels. There are a number of methods proposed for achieving this, as well as number of proposals for suitable gas mixtures and pressures, as well as designs for containing a pressurized environment in the lunar vacuum.

Thermal Protection

The lack of an atmosphere on the moon, together with the extreme duration of the lunar day/night cycle, leads to large temperature extremes. A lunar habitat would need to provide a reasonably constant temperature inside.

The most commonly proposed solution to this problem is a blanket of lunar regolith piled over the habitat. Lunar regolith has extremely low thermal conductivity, and as little as a few inches would protect the habitat from any temperature swings that would be experienced outside^[1]. This solution has an advantage in that lunar regolith is readily available anywhere on the moons surface. The downside is that moving a sufficient amount of regolith to cover a lunar structure would require construction equipment on site, which may not be available for an initial lunar base attempt.

More conventional insulation could be used in this case as well. Due to the vacuum conditions on the moons surface, a reflective coating applied to the surface of the habitat would provide reasonably good thermal protection, functioning in a similar manner to a thermos. This coating would reflect solar radiation during the day, and preventing radiation of internal heat at night. Multiple reflective baffles installed at the surface would increase the effect. To date, this approach has been utilized on all lunar missions, all of which took place during the lunar day and near the equator.

Even if the insulation was sufficient to block out the temperature variations, some additional cooling would be required, as energy would be continuously be generated within the habitat from electrical equipment and the metabolic processes of the inhabitants. Insulation sufficient to block out heat from outside would, on the same token, keep heat inside. A series of external radiators, suitably placed so as to be out of the sun during the day, could provide the necessary cooling.

Meteorites

A lunar habitat would need to be protected from meteorite impacts. This requirement is similar to the requirements already in place on orbital structures such as the ISS. One significant difference is that orbital structures have a certain amount of maneuvering capability to dodge incoming debris, while a lunar habitat does not. As such lunar structures have more stringent requirements than orbital structures for impact protection.

The solution to this problem most commonly suggested is the same as for thermal protection, namely, a blanket of lunar regolith. This blanket would need to be thicker than what is required for thermal protection, though a thickness of less than half a meter is considered to be sufficient^[1]. This again carries the requirement of having construction equipment on site.

Other shielding technologies could be utilized to provide sufficient meteorite protection. Inflatable spacecraft designs in particular show promise in this regard. Bigelow aerospace is developing a line of these structures, a derivative of the cancelled NASA TransHab project. Bigelow has already flown two prototypes of this technology, and intends to construct a privately owned space station with them, as well as an eventual moonbase. The company claims that the meteorite shielding material built into its modules is sufficient for this purpose.

Radiation

One of the more difficult problems facing design of a lunar habitat is protection from solar and cosmic radiation. The moon, being outside the earths magnetic field, receives this radiation directly. Of particular importance is the effect of solar storms, a single one of which would provide sufficient radiation to kill an unprotected person.

The regolith blanket proposed as protection from thermal and meteorite hazards could also serve the third function of radiation protection, given sufficient thickness. How thick this shield would need to be is a matter of some debate, as the exact level of safe radiation is not entirely agreed upon. To reduce the radiation levels received to current NASA standards for its astronauts, a thickness of 1-2 meters appears to be sufficient^[1]. If earth-like levels are desired, then 3-5 meters would likely be needed. The exact thickness is not precisely known, due to the differences between cosmic radiation and the nuclear radiation most shielding science is designed to protect against, and most likely will remain an educated guess until a more in-depth field study is made.

If equipment for moving a sufficient amount of lunar regolith is not available on site (an early base construction attempt for example), providing sufficient shielding is difficult matter. One option is to site the base in of the permanently shaded polar craters, where solar storms would not reach. Another is to provide a "storm cellar" of sorts, a small room in the habitat which is heavily shielded against radiation, which the crew could retreat into in case of a solar storm. As this room would only need to be big enough to hold the crew until the radiation levels dropped back to normal, its construction and shipping to the base site would be much simpler than shielding the entire habitat, which could make it a viable solution for an early base attempt.

Moonquakes

(see main article: Moonquake)

Moonquakes are moderately powerful (by earth standards) seismic events which can last for over ten minutes. Habitats placed in areas where moonquakes occur will need to be sufficiently strong/flexible to withstand the shaking without buckling or leaking atmosphere.

Proposed Designs

Architecture as Mole Hills: The living space could be inflated structures buried in trenches.

Architecture as Tent City: We could use tents to protect inflated living space.

Architecture in Field Stone: The loose rocks of the Moon could provide the needed thermal and radiation protection.

References

↑ ^1.0 ^1.1 ^1.2 Lindsey, Nancy J. Lunar Station Protection: Lunar Regolith Shielding. International Lunar Conference 2003 Cite error: Invalid <ref> tag; name "Lindsey" defined multiple times with different content Cite error: Invalid <ref> tag; name "Lindsey" defined multiple times with different content