The environmental conditions of the Moon require mitigation if a long-term human presence is to be achieved for extended periods of time. Radiation, micrometeoroid impacts, high-velocity debris, and thermal cycling represent threats to crew, equipment, and facilities. For decades, local regolith has been suggested as a candidate material to use in the construction of protective barriers. A thickness of roughly 3 m is sufficient protection from both direct and secondary radiation from cosmic rays and solar protons; this thickness is sufficient to reduce radiation exposure even during solar flares. NASA has previously identified a need for innovations that will support lunar habitats using lightweight structures because the reduction of structural mass translates directly into additional up and down mass capability that would facilitate additional logistics capacity and increased science return for all mission phases. The development of non-pressurized primary structures that have synergy with the development of pressurized structures is also of interest. The use of indigenous or in situ materials is also a well-known and active area of research that could drastically improve the practicality of human exploration beyond low-Earth orbit.

Views of ARMOR Construction. The temporary inflatable (A) deploys (i). Then the jacket (B) is deployed (ii). Regolith (C) is then poured into the jacket and initially supported by the inflatable (iii). When the jacket is filled, the regolith inside the arch of the jacket is self-supporting, and the inflatable is no longer necessary (iv). Habitat modules and equipment (D) can be moved into the ARMOR (v). The jacket is shown in cutaway in steps (ii), (iii), and (iv) to illustrate regolith filling.
The Archway for Radiation and Micrometeorite Occurrence Resistance (ARMOR) concept is a new, multifunctional structure that acts as radiation shielding and micrometeorite impact shielding for long-duration lunar surface protection of humans and equipment. ARMOR uses a combination of native regolith and a deployed membrane “jacket” to yield a multifunctional structure. ARMOR is a robust and modular system that can be autonomously assembled onsite prior to the first human surface arrival.

The system provides protection by holding a sufficiently thick (3 m) archshaped shell of local regolith around a central cavity. The regolith is held in shape by an arch-shaped jacket made of strong but deployable material. No regolith processing is required. During the regolith filling process, an inflatable structure under the arch supports the mass of the regolith, but once regolith filling is complete the catenary arch formed by the regolith and the jacket becomes self-supporting and the inflatable can be deflated and removed. When complete, habitat modules and equipment can be moved into the protected cavity under the arch. ARMOR is a near-term system that would provide a reliable and robust lightweight structure technology to support large lunar habitats, drastically lower launch mass, and improve efficient volume use, reducing launch costs.

ARMOR also protects from micrometeorites. The kinetic energy of micrometeorites and other debris will be absorbed first by an external, high-strength blanket held over and slightly away from the ARMOR jacket. The projectile penetrates this outer blanket, but becomes fragmented and loses energy in the process. The remnants of the projectile then impact the exterior of the jacket, and the jacket and regolith absorb the remaining kinetic energy. Facilities placed inside the ARMOR will be protected from direct sunlight, reducing the extreme temperature variations. Infrared radiation from the facility will be reflected by the interior of the ARMOR back onto the facility, reducing heat loss.

This work was done by Dr. Louis R. Giersch of Caltech for NASA’s Jet Propulsion Laboratory. NPO-47686

This Brief includes a Technical Support Package (TSP).
Archway for Radiation and Micrometeorite Occurrence Resistance

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This article first appeared in the December, 2012 issue of NASA Tech Briefs Magazine.

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