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European Space Agency plans simulated lunar test site

By Robert L. Reid

During the first quarter of 2021, the European Space Agency plans to break ground on a test site that will simulate conditions on the moon. Called Luna, the facility will be constructed at the ESA’s European Astronaut Center in Cologne, Germany, and feature a roughly 600 sq m area covered in simulated lunar soil, a module that represents a lunar habitat, and an experimental energy system to power the habitat, explains Aidan Cowley, Ph.D., a system engineer at the Astronaut Center.

The design team for the project includes Hirschmuellerschmidt Architektur GmbH and CSZ Ingenieurconsult GmbH. When completed in 2022, Luna will be used by the ESA and made available to other space agencies and scientific organizations around the world for astronaut training, experiments, and research. There will be no charge to use the facility for scientific purposes, Cowley says, unless an experiment involves any alterations to the site or its systems; such changes would have to be paid for by the testing organization.

The main Luna facility, housing the simulated lunar surface, will be in a stand-alone building roughly 52 m long, 20 m wide, and 13 m tall, located on an open piece of land adjacent to other Astronaut Center buildings, Cowley says. Although details of the design are still being finalized, the main structure will most likely feature steel framing atop a poured concrete foundation, Cowley notes. 

Measuring approximately 30 by 20 m, the test bed portion will be a large, open hall within the main building, its floor covered by a roughly 1 m deep layer of simulated lunar soil, or regolith. There will also be designated sections of the regolith that are as deep as 3 m to be used for drilling experiments. 

The simulated lunar soil will essentially be a fine basalt sand acquired from the nearby and historically volcanic Eifel region. Local quarries will grind the material to the proper size distribution to represent lunar regolith; some or all of the simulated soil might be ground finely enough to represent the ever-
present and troublesome lunar dust that the Apollo astronauts had to contend with. The dust might be restricted to a smaller enclosed space within the main hall, or it might ultimately be used throughout the facility, more accurately reflecting conditions on the moon. 

An overhead crane system will be installed within the roof of the test bed hall and could potentially be used to help simulate the moon’s lower gravity, Cowley says. The dynamic lighting system within the hall will be used to simulate both equatorial and polar lunar lighting. Many of the Apollo missions landed near the moon’s equator, where the position of the sun produced relatively small shadowed areas, Cowley explains. But future lunar exploration, especially by robots, is expected to concentrate on the polar regions, where the cameras on mechanical rovers will encounter “really distinct light and dark areas that make it difficult to navigate,” Cowley says.

Although the astronauts using the test bed are welcome to wear spacesuits, the hall will not attempt to re-create the airless conditions on the moon nor will it be used to simulate the extreme temperature swings experienced on the lunar surface. Temperature and humidity will be maintained within the test bed hall to keep the approximately 600 metric tons of simulated regolith in good condition, Cowley explains. 

In addition to the somewhat cavernous open space of the test bed hall, the main building will also include three-level portions with offices, storage space, technical breakout rooms, experiment preparation rooms, and a visitor gallery. “We appreciate that (Luna) will be quite a visual spectacle,” Cowley says, adding that the Astronaut Center already hosts numerous guests each year.

The simulated habitat, known as the Flex Hab, will be a smaller steel structure, akin to a trailer, measuring roughly 10 m long by 3 m wide and 2 m tall. Although it will be connected to a side wall of the test bed hall, the Flex Hab will be designed so that it can be removed from the main facility and transported for testing at other scientific sites throughout Europe, Cowley says. 

The habitat will feature three sections: a simulated air lock to enable people to move from the module to the simulated lunar surface as they would do on the moon, a small engineering section with controls for the habitat’s energy and battery systems, and a larger experimental section for the modular test racks that will be used during the research and experiments. The Flex Hab will be designed with traditional building materials — not anything that would actually be used on the moon, Cowley says. There will be no radiation shielding or other actual space hardware involved. It will be used solely as an operational simulation, and not as a demonstration of the actual lunar technology, he explains.

The energy simulation will feature systems and certain processes that will be used “in a representative way of what you’d actually do in the lunar environment,” Cowley says. For example, to help astronauts survive the lunar night — which creates total darkness for up to two weeks — the habitat would require considerable energy storage. During the lunar day phase, photovoltaics will charge battery systems and “excess power will drive an electrolyzer to split water into hydrogen and oxygen,” Cowley explains. Astronauts would likely use water from ice on the moon in such a system, he explains. “Then as you enter the lunar night, you’ll recombine the hydrogen and oxygen in a fuel cell to generate electricity.” 

The energy infrastructure will not be configured at Luna as it would actually be arranged at a moon base. For legal, technical, and safety reasons, the energy systems will be kept separate from the habitat — in a standard shipping container parked beside the Flex Hab module, with the photovoltaic cells located atop the main test bed building. But “once we get (the energy system) working, it’ll be a nice demonstration of a partially closed-loop hydrogen system,” Cowley says.

This article first appeared in the November 2020 issue of Civil Engineering.

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