How could we build a liveable space habitat?

In the not-too-distant future, humanity will be faced with the challenge of building permanent homes in space. For this to happen, space habitats will need to closely replicate Earth’s gravity, while dealing with the threat of radiation and meteorites from outer space. Through his research, Werner Grandl at Space Renaissance International in Italy considers how these challenges could be overcome. Through a series of recent studies, he conceives a feasible design for a rotating space habitat, shielded from outer space by a mined‑out asteroid.

The idea of human settlers establishing permanent homes in space is a staple of our favourite sci-fi. Over the past century, countless films, books, TV shows, and video games have found creative, often elaborate ways to convey the threats and motivations which would force humanity to leave Earth behind and explain how they might survive in the harsh environment of space.

Yet today, many of these fictional threats look all too familiar in the real world. Werner Grandl at Space Renaissance International explains, ‘Besides man-made disasters like global warming or nuclear war, there are a number of serious natural threats to planet Earth such as asteroid impacts, super-volcanoes, and ice ages.’

For Grandl, the ever-looming presence of these threats creates a pressing need for us to think about what realistic extra-terrestrial habitats could look like and consider how they could be constructed in the not-too-distant future. ‘The construction of self-sustaining colonies in space using lunar and asteroid resources will be the next step of human evolution,’ he says.

Accommodating the human body

Beyond the staggering feats of engineering required to build these habitats, some of the most important challenges to consider in their design are related to the limitations of our own bodies. Having evolved on Earth, the physical attributes of our muscles, bones, and many other vital biological systems are finely tuned to functioning in the gravitational field of our home planet. If we leave this familiar environment for extended periods, medical problems will inevitably start to emerge before long. ‘A lack of gravity can cause danger for human health such as bone demineralisation, muscle atrophy, and orthostatic intolerance,’ Grandl explains.

Just like generations of sci-fi writers – although with far higher stakes – this challenge will be one of the first things we will need to consider when conceiving future space colonies. To provide a suitable home for the human body, habitats will need to generate their own artificial gravity, which matches Earth’s field as closely as possible.

A familiar grounding force

To simulate gravity, future space habitats will need to spin. ’Rotating space habitats can provide simulated gravity and a comfortable environment for astronauts and space settlers,’ says Grandl. The effect is achieved through the effect of centrifugal forces – you have probably experienced this effect yourself when driving a car around a tight curve or riding the loop-the-loop on a rollercoaster.

Here, the idea is that the manned part of a space habitat will constantly circle around the centre of the station. In this way, a person standing on the inner rim of the circle would feel like they are being pulled downwards by gravity, when in fact the floor is pushing them upwards, towards the centre of the habitat’s rotation.

Designing a rotating station

In one recent study, Grandl took this concept a step further. In his paper, he envisages a habitat built from interconnected cylindrical modules, which spin around the axis of a central cylinder – powered by a non-rotating framework of solar panels.

Grandl then shows how such a habitat could be enlarged in stages: eventually reaching a diameter of 102 metres, incorporating some 32 living quarter modules, which could comfortably house up to 180 people long term. He also considers how an agricultural sphere could be attached, providing food for these inhabitants.

A home inside an asteroid

Low-gravity environments aren’t the only challenge. In the harsh environment of space, without any atmosphere to protect them, future space habitats would face a constant threat of bombarded with radiation from the Sun, as well as tiny meteorites hurtling through space. Building further on his earlier concept, Grandl next considered how rotating habitats could be made safer by housing them inside hollowed-out asteroids – shielding them from outer space.

‘Near-Earth asteroids can be mined and the remaining cave would be a natural shelter against cosmic rays, solar flares, micrometeorites,’ he describes. ‘Inside excavated asteroids we can build self-sustaining human outposts in space providing artificial gravity.’

To reach this point, Grandl has conceived a multi-step process. It starts with a pair of unmanned space tugs, docked to either side of a near-Earth asteroid using anchors drilled firmly into the rock. Using advanced propulsion systems, the tugs could then pull the asteroid into a stable orbit around Earth, beyond the Moon.

From here, mining can begin along the axis of the asteroid’s rotation. At this point, the asteroid is connected to a manned space station – with the space and equipment required for digging, as well as carrying, processing, and storing mined materials.

After boring a straight tunnel into the centre of the asteroid, a larger spherical cave could then be excavated, taking up around half of the asteroid’s total volume. While mass is being removed from the asteroid, its orbit would be continuously stabilised by the two space tugs, still docked to either side. Finally, once mining has finished, a rotating habitat could be constructed inside the cave.

The future path to space

While our technology is still a long way off from being able to build these habitats, Grandl is confident that with the current pace of advancement, they will one day be perfectly feasible. Before we get there, he envisages a step-by-step improvement in our understanding of survival in space. ‘As a first step, we should build a rotating space station in Earth’s orbit to study the influence of different gravity-levels on human health,’ he describes.

From here, we could build on this understanding to modify designs of manned space habitats to ensure the highest possible standards of safety and comfort for their inhabitants. Ultimately, by starting to tackle these challenges now, Grandl hopes that the possibility of permanently manned space habitats will begin to look far more feasible in the coming decades. In turn, his ideas may one day help to accelerate humanity’s exploration of the solar system, and to ensure our future in the face of whatever disasters we may one day face.