Imagine a habitable colony connected Mars oregon the Moon and the kinds of structures that travel to caput are astir apt gleaming domes oregon shiny metallic tubes snaking implicit the surface. But with nary Earth-like ambiance oregon magnetic tract to repel star radiation and micrometeorites, abstraction colonists would astir apt request to heap metres-thick rocks and geological rubble onto the roofs of specified off-world settlements. More similar a hobbit spread than Moonbase Alpha.
There could beryllium different solution, however, that would connection aboriginal colonists safer and acold much expansive surviving abstraction than immoderate cramped basal built connected the surface. Writing successful Acta Astronautica, Raymond Martin, an technologist astatine Blue Origin, a rocket company, and Haym Benaroya, an aerospace technologist astatine Rutgers University, research the benefits of mounting up a Moon basal wrong elephantine geological tunnels that prevarication conscionable beneath the lunar surface.
First discovered during the Apollo programme, these lunar lava tubes are a bequest of erstwhile Earth’s nearest celestial neighbour was geologically hyperactive, with streams of boiling basaltic magma bursting from the interior to travel crossed the Moon’s aboveground arsenic lava. Found connected Earth (see picture), and identified connected Mars, lava tubes signifier erstwhile the sluggish apical furniture of a lava watercourse slows and cools, forming a heavy and rocky lid that is near down erstwhile the remainder of the lava underneath yet drains away.
Lava tubes connected Earth are usually up to 15 metres wide and tin tally for respective kilometres. But the reduced gravity connected the Moon makes them hundreds of times bigger, creating colossal cave systems that are up to a kilometre crossed and hundreds of kilometres long.
Space scientists person agelong identified these lava caves arsenic a apt tract for quality habitation connected the Moon, due to the fact that the heavy walls and ceiling connection extortion from the harsh radiation striking the Moon’s surface. But Mr Martin and Dr Benaroya went a measurement further. Rather than simply situating a Moon basal wrong a lava tube—domes and shiny buildings and all—they suggested that a conception of specified a conduit could beryllium pressurised with breathable air. Residents could live, enactment and slumber wrong the pressurised tubes with nary request for abstraction suits and with plentifulness of spare existent property for immoderate low-gravity recreation. And though the costs and details request much planning, it could extremity up cheaper than having to nonstop from Earth everything needed to past connected the lunar surface.
In their latest study, the 2 scientists crunched immoderate numbers connected what mightiness beryllium possible. “One of the archetypal large hurdles determination is proving that they [the lava tubes] are structurally sound,” says Mr Martin. To find out, helium and Dr Benaroya built a machine exemplary to simulate the integrity of a comparatively tiny lava conduit successful the Moon’s Oceanus Procellarum (Ocean of Storms), which was photographed by the Indian Chandrayaan-1 lunar probe 15 years ago.
After checking respective combinations of interior unit and extortion thickness, and whether the resulting operation was stable, the survey suggested a lava conduit with a extortion thickness of 10 metres could beryllium safely pressurised to astir the aforesaid conditions recovered astatine oversea level connected Earth. The scientists besides showed that the wide unit (and truthful the hazard of extortion failure) could beryllium reduced by expanding the proportionality of oxygen successful the artificial aerial utilized to capable the caverns. And fixed the awkwardness of moving astir successful a abstraction suit, the survey looked astatine however astronauts could get themselves and their instrumentality safely successful and retired of the tubes. The champion option, it concluded, would beryllium to physique the entranceway wherever a partition of the lava conduit had already collapsed open.
Knowing that the extortion volition not autumn successful should springiness engineers the assurance to enactment connected different aspects of the idea, specified arsenic however to usage inflatable structures to headdress the ends of a pressurised conception of the tube. Such membranes are already utilized for flood prevention successful tunnels connected Earth, wherever they tin beryllium rapidly deployed to artifact incoming floodwater. Another contented is whether the lava tube’s ceiling would beryllium afloat airtight, and if not, however to seal it to forestall leaks. And, of course, however to hole humanity for a instrumentality to beingness successful caves. ■