Having astronauts living and working on the Moon or a planet such as Mars is a compelling idea. It would provide a new base for space exploration, and could help answer many questions that trouble Earth-based scientists today, such as, “Is there (or has there ever been) water or life outside of Earth?” To survive for an extended time on such stark surfaces, astronauts would need a safe and secure habitat, one able to withstand the different atmospheres, wide-ranging temperatures, high-level radiation, and space debris that characterize these environments.

Humans evolved in an atmosphere—a blanket of gases that gravity holds in place around Earth. The weight of that blanket is called air pressure. The human body has adapted to life in our atmosphere by maintaining an internal pressure pushing outward that balances air pressure pushing in (measured as one atmosphere at sea level). With sufficient oxygen to breathe, we can exist comfortably in pressures down to one-third of an atmosphere. However, at pressures lower than this, gases start to boil and bubble out of the body's cells and tissues, starving the body of oxygen. For all practical purposes, the moon has no atmosphere, and while Mars has an atmosphere, it is extremely thin. For astronauts to live outside of Earth's atmosphere, a structure would need to support an artificial atmosphere.

A Moon or Mars habitat would also need to shield astronauts from harsh temperatures and radiation. Because there is practically no atmosphere on the Moon to help moderate surface temperature, it ranges from extremely hot during daylight—up to 253°F (123°C)—to extremely cold at night—down to -387°F (-233°C). Mars, which is farther from the Sun than Earth, can warm to about 70°F (20°C) during a summer day, but it can drop to -225°F (-153°C) in winter. These landscapes are also directly exposed to the Sun’s cosmic rays and solar wind as well as radiation from other stars. Finally, space is full of small rocks and other debris; most zoom faster than speeding bullets and often will strike the surfaces of the Moon and Mars. These micrometeoroids represent a real threat to any structure and its inhabitants.

NASA is testing a design for a two-layer inflatable habitat that would address each of these challenges. The habitat features lightweight and flexible materials with durable and protective properties. The inner layer, or bladder, is coated in a rubberlike plastic polymer. When the structure is inflated, this layer is forced against the outer layer and becomes part of a matrix that seals in air and creates the artificial atmosphere humans need. To protect against external hazards, especially temperature and micrometeoroids, the outer layer is made of a weave that includes Kevlar, a textile composite often used in bulletproof vests, and Vectran, which is used like webbing to reinforce ropes, cables, and sailcloth. NASA has yet to determine how best to shield its inflatable habitat from radiation. Ideas include creating a “force field” around the habitat. This powerful electric field would have the same charge as the incoming radiation and thus repel it.

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