Compressive strength | 39–75.7 N/mm2 (MPa) |
---|---|
Young's modulus | 21.4 kN/mm2 |
Density | 2.6 g/cm3 |
Temperature coefficient | 5.4 × 10−6 K−1 |
Lunarcrete, also known as "mooncrete", an idea first proposed by Larry A. Beyer of the University of Pittsburgh in 1985, is a hypothetical construction aggregate, similar to concrete, formed from lunar regolith, that would reduce the construction costs of building on the Moon. [3] AstroCrete is a more general concept also applicable for Mars.
Only comparatively small amounts of Moon rock have been transported to Earth, so in 1988 researchers at the University of North Dakota proposed simulating the construction of such a material by using lignite coal ash. [3] Other researchers have used the subsequently developed lunar regolith simulant materials, such as JSC-1 (developed in 1994 and as used by Toutanji et al.) and LHS-1 (developed and produced by Exolith Lab). [4] [5] Some small-scale testing, with actual regolith, has been performed in laboratories, however. [2]
The basic ingredients for lunarcrete would be the same as those for terrestrial concrete: aggregate, water, and cement. In the case of lunarcrete, the aggregate would be lunar regolith. The cement would be manufactured by beneficiating lunar rock that had a high calcium content. Water would either be supplied from off the Moon, or by combining oxygen with hydrogen produced from lunar soil. [2]
Lin et al. used 40g of the lunar regolith samples obtained by Apollo 16 to produce lunarcrete in 1986. [6] The lunarcrete was cured by using steam on a dry aggregate/cement mixture. Lin proposed that the water for such steam could be produced by mixing hydrogen with lunar ilmenite at 800 °C, to produce titanium oxide, iron, and water. It was capable of withstanding compressive pressures of 75 MPa, and lost only 20% of that strength after repeated exposure to vacuum. [7]
In 2008, Houssam Toutanji, of the University of Alabama in Huntsville, and Richard Grugel, of the Marshall Space Flight Center, used a lunar soil simulant to determine whether lunarcrete could be made without water, using sulfur (obtainable from lunar dust) as the binding agent. The process to create this sulfur concrete required heating the sulfur to 130–140 °C. After exposure to 50 cycles of temperature changes, from -27 °C to room temperature, the simulant lunarcrete was found to be capable of withstanding compressive pressures of 17MPa, which Toutanji and Grugel believed could be raised to 20MPa if the material were reinforced with silica (also obtainable from lunar dust). [8]
There would need to be significant infrastructure in place before industrial scale production of lunarcrete could be possible. [2]
The casting of lunarcrete would require a pressurized environment, because attempting to cast in a vacuum would simply result in the water sublimating, and the lunarcrete failing to harden. Two solutions to this problem have been proposed: premixing the aggregate and the cement and then using a steam injection process to add the water, or the use of a pressurized concrete fabrication plant that produces pre-cast concrete blocks. [2] [9]
Lunarcrete shares the same lack of tensile strength as terrestrial concrete. One suggested lunar equivalent tensioning material for creating pre-stressed concrete is lunar glass, also formed from regolith, much as fibreglass is already sometimes used as a terrestrial concrete reinforcement material. [2] Another tensioning material, suggested by David Bennett, is Kevlar, imported from Earth (which would be cheaper, in terms of mass, to import from Earth than conventional steel). [9]
This proposal is based on the observation that water is likely to be a precious commodity on the Moon. Also sulfur gains strength in a very short time and doesn't need any period of cooling, unlike hydraulic cement. This would reduce the time that human astronauts would need to be exposed to the surface lunar environment. [10] [11]
Sulfur is present on the Moon in the form of the mineral troilite, (FeS) [12] and could be reduced to obtain sulfur. It also doesn't require the ultra high temperatures needed for extraction of cementitious components (e.g. anorthosites).
Sulfur concrete is an established construction material. Strictly speaking it isn't a concrete as there is little by way of chemical reaction. Instead the sulfur acts as a thermoplastic material binding with a non reactive substrate. Cement and water are not required. The concrete doesn't have to be cured, instead it is simply heated to above the melting point of sulfur, 140 °C, and after cooling it reaches high strength immediately.
The best mixture for tensile and compressive strength is 65% JSC-1 lunar regolith simulant and 35% sulfur, with an average compressive strength of 33.8 MPa and tensile strength of 3.7 MPa. Addition of 2% metal fiber increase the compressive strength to 43.0 MPa [13] Addition of silica also increases the strength of the concrete. [14]
This sulfur concrete could be of especial value for dust minimization, for instance to create a launching pad for rockets leaving the Moon. [12]
It provides less protection from cosmic radiation, so walls would need to be thicker than Portland-cement-based concrete walls (the water in concrete is an especially good absorber of cosmic radiation).
Sulfur melts at 115.2 °C, and lunar temperatures in high latitudes can reach 123 °C at midday. In addition, the temperature changes could change the volume of the sulfur concrete due to polymorphic transitions in the sulfur. [12] (see Allotropes of sulfur). [14]
So unprotected sulfur concrete on the Moon, if directly exposed to the surface temperatures, would need to be limited to higher latitudes or shaded locations with maximum temperatures less than 96 °C and monthly variations not exceeding 114 °C.
The material would degrade through repeated temperature cycles, but the effects are likely to be less extreme on the Moon due to the slowness of the monthly temperature cycle. The outer few millimeters may be damaged through sputtering from impact of high energy particles from the solar wind and solar flares. This may however be easy to repair, by reheating or recoating the surface layers in order to sinter away cracks and heal the damage.
AstroCrete is a concrete-like material proposed to be used on Moon or Mars made from regolith and human serum albumin (HSA), a protein from human blood. Scientists demonstrated that such material had compressive strengths as high as 25 MPa, while ordinary concrete had 20–32 MPa. By adding urea (byproduct in urine, sweat, and tears), the resultant material became substantially stronger than ordinary concrete, with 40 MPa of compressive strength. [15] [16] [17]
As noted by the authors: [16]
In essence, human serum albumin produced by astronauts in vivo could be extracted on a semi-continuous basis and combined with lunar or Martian regolith to ‘get stone from blood’, to rephrase the proverb. We believe that human serum albumin extraterrestrial regolith biocomposites could potentially have a significant role in a nascent Martian colony.
Researchers also experimented with synthetic spider silk and bovine serum albumin as regolith binders, noting that these materials could also be produced on Mars after advancements in biomanufacturing technology. [16]
The idea behind AstroCrete is not new, that is acknowledged by authors: "adhesives and binders of biological origin were widely utilized by humanity for millennia before the development of synthetic petroleum-derived adhesives. Tree resins, collagen from hooves, casein from cheese, and animal blood were all used as binders and additives for various applications". [16]
Researchers calculated that a crew of 6 astronauts could produce over 500 kg of AstroCrete over the course of a two-year mission on the surface of Mars. [15] Each astronaut "could produce enough additional habitat space to support another astronaut, potentially allowing the steady expansion of an early Martian colony". [17]
In 2023, A.D. Roberts, wrote a story on the use of 'AstroCrete' being tested in the creation of a building material on Mars in order to overcome the challenge of obtaining bulk material for construction on the planet. [18]
David Bennett, of the British Cement Association, argues that lunarcrete has the following advantages as a construction material for lunar bases: [9]
He observes, however, that lunarcrete is not an airtight material, and to make it airtight would require the application of an epoxy coating to the interior of any lunarcrete structure. [9]
Bennett suggests that hypothetical lunar buildings made of lunarcrete would most likely use a low-grade concrete block for interior compartments and rooms, and a high-grade dense silica particle cement-based concrete for exterior skins. [9]
Phobos is the innermost and larger of the two natural satellites of Mars, the other being Deimos. The two moons were discovered in 1877 by American astronomer Asaph Hall. It is named after Phobos, the Greek god of fear and panic, who is the son of Ares (Mars) and twin brother of Deimos.
Regolith is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestrial planets and moons.
Accelerants, or accelerators, are substances that increase the rate of a natural or artificial chemical process. They play a major role in chemistry, as most chemical reactions can be hastened with an accelerant. Understanding accelerants is crucial in forensic science, engineering, and other fields where controlled chemical reactions are essential. Accelerants function by either altering a chemical bond, speeding up a chemical process, or changing the reaction conditions. Unlike catalysts, accelerants may be consumed during the process.
Space manufacturing or In-space manufacturing is the fabrication, assembly or integration of tangible goods beyond Earth's atmosphere, involving the transformation of raw or recycled materials into components, products, or infrastructure in space, where the manufacturing process is executed either by humans or automated systems by taking advantage of the unique characteristics of space. Synonyms of Space/In-space manufacturing are In-orbit manufacturing, Off-Earth manufacturing, Space-based manufacturing, Orbital manufacturing, In-situ manufacturing, In-space fabrication, In-space production, etc.
In space exploration, in situ resource utilization (ISRU) is the practice of collection, processing, storing and use of materials found or manufactured on other astronomical objects that replace materials that would otherwise be brought from Earth.
Lunar regolith is the unconsolidated material found on the surface of the Moon and in the Moon's tenuous atmosphere. Sometimes referred to as Lunar soil, Lunar soil specifically refers to the component of regolith smaller than 1 cm. It differs substantially in properties from terrestrial soil.
David Stewart McKay was chief scientist for astrobiology at the Johnson Space Center. During the Apollo program, McKay provided geology training to the first men to walk on the Moon in the late 1960s. McKay was the first author of a scientific paper postulating past life on Mars on the basis of evidence in Martian meteorite ALH 84001, which had been found in Antarctica. This paper has become one of the most heavily cited papers in planetary science. The NASA Astrobiology Institute was founded partially as a result of community interest in this paper and related topics. He was a native of Titusville, Pennsylvania.
Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: aeronautical engineering and astronautical engineering. Avionics engineering is similar, but deals with the electronics side of aerospace engineering.
A lunar regolith simulant is a terrestrial material synthesized in order to approximate the chemical, mechanical, engineering, mineralogical, or particle-size distribution properties of lunar regolith. Lunar regolith simulants are used by researchers who wish to research the materials handling, excavation, transportation, and uses of lunar regolith. Samples of actual lunar regolith are too scarce, and too small, for such research, and have been contaminated by exposure to Earth's atmosphere.
Space architecture is the theory and practice of designing and building inhabited environments in outer space. This mission statement for space architecture was developed in 2002 by participants in the 1st Space Architecture Symposium, organized at the World Space Congress in Houston, by the Aerospace Architecture Subcommittee, Design Engineering Technical Committee (DETC), American Institute of Aeronautics and Astronautics (AIAA).
Concrete is produced in a variety of compositions, finishes and performance characteristics to meet a wide range of needs.
Concrete has relatively high compressive strength, but significantly lower tensile strength. The compressive strength is typically controlled with the ratio of water to cement when forming the concrete, and tensile strength is increased by additives, typically steel, to create reinforced concrete. In other words we can say concrete is made up of sand, ballast, cement and water.
Sulfur concrete, sometimes named thioconcrete or sulfurcrete, is a composite construction material, composed mainly of sulfur and aggregate. Cement and water, important compounds in normal concrete, are not part of sulfur concrete. The concrete is heated above the melting point of elemental sulfur at ca. 140 °C (284 °F) in a ratio of between 12% and 25% sulfur, the rest being aggregate.
Terrestrial analogue sites are places on Earth with assumed past or present geological, environmental or biological conditions of a celestial body such as the Moon or Mars. Analogue sites are used in the frame of space exploration to either study geological or biological processes observed on other planets, or to prepare astronauts for surface extra-vehicular activity.
Martian regolith simulant is a terrestrial material that is used to simulate the chemical and mechanical properties of Martian regolith for research, experiments and prototype testing of activities related to Martian regolith such as dust mitigation of transportation equipment, advanced life support systems and in-situ resource utilization.
NASA's Lunabotics Challenge
The Swamp Works is a lean-development, rapid innovation environment at NASA's Kennedy Space Center. It was founded in 2012, when four laboratories in the Surface Systems Office were merged into an enlarged facility with a modified philosophy for rapid technology development. Those laboratories are the Granular Mechanics and Regolith Operations Lab, the Electrostatics and Surface Physics Lab, the Applied Chemistry Lab, and the Life Support and Habitation Systems (LSHS) team. The first two of these are located inside the main Swamp Works building, while the other two use the facility although their primary work is located elsewhere. The team developed the Swamp Works operating philosophy from Kelly Johnson's Skunk Works, including the "14 Rules of Management", from the NASA development shops of Wernher von Braun, and from the innovation culture of Silicon Valley. The team prototypes space technologies rapidly to learn early in the process how to write better requirements, enabling them to build better products, rapidly, and at reduced cost. It was named the Swamp Works for similarity with the Skunk Works and the Phantom Works, but branded by the widespread marshes (swamps) on the Cape Canaveral and Merritt Island property of the Kennedy Space Center. The Swamp Works was co-founded by NASA engineers and scientists Jack Fox, Rob Mueller, and Philip Metzger. The logo, a robotic alligator, was designed by Rosie Mueller, a professional designer and the spouse of Rob Mueller.
The World Is Not Enough (WINE) is a US project developing a refuelable steam engine system for spacecraft propulsion. WINE developed a method of extracting volatiles from ice, ice-rich regolith, and hydrated soils and uses it as steam propulsion which allows the spacecraft to refuel multiple times and have an extraordinary long service lifetime. This would allow a single spacecraft to visit multiple asteroids, comets or several landing locations at an icy world such as the Moon, Mars, Pluto, Enceladus, Ganymede, Europa, etc.
Astropedology is the study of very ancient paleosols and meteorites relevant to the origin of life and different planetary soil systems. It is a branch of soil science (pedology) concerned with soils of the distant geologic past and of other planetary bodies to understand our place in the universe. A geologic definition of soil is “a material at the surface of a planetary body modified in place by physical, chemical or biological processes”. Soils are sometimes defined by biological activity but can also be defined as planetary surfaces altered in place by biologic, chemical, or physical processes. By this definition, the question for Martian soils and paleosols becomes, were they alive? Astropedology symposia are a new focus for scientific meetings on soil science. Advancements in understanding the chemical and physical mechanisms of pedogenesis on other planetary bodies in part led the Soil Science Society of America (SSSA) in 2017 to update the definition of soil to: "The layer(s) of generally loose mineral and/or organic material that are affected by physical, chemical, and/or biological processes at or near the planetary surface and usually hold liquids, gases, and biota and support plants". Despite our meager understanding of extraterrestrial soils, their diversity may raise the question of how we might classify them, or formally compare them with our Earth-based soils. One option is to simply use our present soil classification schemes, in which case many extraterrestrial soils would be Entisols in the United States Soil Taxonomy (ST) or Regosols in the World Reference Base for Soil Resources (WRB). However, applying an Earth-based system to such dissimilar settings is debatable. Another option is to distinguish the (largely) biotic Earth from the abiotic Solar System, and include all non-Earth soils in a new Order or Reference Group, which might be tentatively called Astrosols.
The Moon bears substantial natural resources which could be exploited in the future. Potential lunar resources may encompass processable materials such as volatiles and minerals, along with geologic structures such as lava tubes that, together, might enable lunar habitation. The use of resources on the Moon may provide a means of reducing the cost and risk of lunar exploration and beyond.