Expert Voices

If We're Serious About Going to Mars, We Need Artificial Gravity (Op-Ed)

Andy Weir, author of "The Martian."
Andy Weir, author of "The Martian." (Image credit: Crown Publishers.)

Andy Weir is the New York Times bestselling author of "The Martian." First hired as a programmer for a national laboratory at age 15, he has been working as a software engineer ever since. Weir is a lifelong space nerd and a devoted hobbyist in subjects like relativistic physics, orbital mechanics and the history of manned spaceflight. "The Martian"is his first novel. Weir contributed this article to's Expert Voices: Op-Ed & Insights.

Research into manned spaceflight is shifting from low-Earth orbit to destinations much further away, like Mars and the asteroid belt. But society will have to invent many new technologies before it can plausibly send people to those distances.

Such exploration calls for more-efficient fuels, or much more efficient ion engines. If future missions can create fuel from resources outside Earth's gravity well (from lunar material or asteroids), these efforts won't have to waste so much energy just to get fuel into space in the first place. Missions will also need lightweight materials that can shield astronauts from radiation as their ship leaves Earth's protective magnetic field. Space missions will require major advances in 3D printing, too, so astronauts can create replacements for equipment that breaks down during their long flights.

But more than all of these things, missions beyond low-Earth orbit require artificial gravity. Research into this technology is not only critical for long-distance missions, it would also provide an immediate benefit to manned spaceflight — even before humans venture out of Earth's orbit.

The reason space missions need artificial gravity is clear: humans simply did not evolve to live in zero gravity. For starters, about half of the planet's astronauts already suffer from Space Adaptation Syndrome (SAS), a condition that includes severe nausea and disorientation. Gravity is integral to how the brain works out spatial orientation. The brain gets really confused if it can't find "down."

At least astronauts can overcome SAS in time. The physical effects of long-term weightlessness , however, are much more serious — notably including skeletal deterioration, muscle atrophy, weakened cardiovascular systems and severe vision problems. Artificial gravity could solve all of these problems.

Cover for the novel "The Martian" (Image credit: Crown Publishers)

The physics are simple: Make a ship that can withstand one g of force (equivalent to the force of gravity on Earth's surface), then start the ship spinning such that the centripetal force is one g at the edge. That's it. No fancy "Star Trek" technology needs to be invented. The ship just needs to spin. And once it's spinning in the vacuum of space, it requires no additional energy or maintenance to continue.

I put this concept into my novel "The Martian" by making the astronauts' transfer ship spin. This was no mere luxury for the crew. In the novel, they spend 124 days in an Earth-Mars transfer before landing on the Red Planet. If they had spent that time in zero-g, muscle atrophy and weakness would have prevented them from even standing up, let alone doing surface operations. The mission plan would have had to schedule a week of recovery time — an unacceptable sacrifice of surface time during such a mission. [First Look at 'The Martian': Book Preview]

Artificial gravity is easily within reach right now. It would not require a giant wheel-in-space that looks like the cover of a 1950's sci-fi novel. A viable design could be something as simple as a crew compartment attached to a counterweight compartment by a long cable that is initially coiled in a spindle. Attitude thrusters on the compartments could start the ship spinning while the cable uncoiled to its desired length. The centripetal force would keep the cable straight as it lengthened. The compartments would have to withstand one g of force, but humanity has 5,000 years of experience building things that withstand one g of force.

Artificial gravity can play a big role in missions that launch much earlier than humanity's first long-distance voyages. The International Space Station (ISS) is only slated to last until 2024 (and many question whether it can really last beyond 2020). If the next space station were built with artificial gravity in mind, it would be monumentally more efficient.

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Imagine a central zero-g compartment with two equally weighted compartments attached to it by long cables. The cables hold the force, and everything is connected through pressurized tunnels. Set the whole station spinning, and the outer compartments can have one g of gravity while the central component remains weightless. This would enable zero-g experimentation (the primary benefit of a space station) while allowing the crew to spend most of their time in gravity.

The crew of ISS has to exercise for two hours every day, one-eighth of their waking lives, just to stave off the harmful effects of weightlessness. The station cost $150 billion to build, which means the world has spent almost $19 billion worth of station time on astronaut exercise regimens.

Put another way, accounting for varying crew sizes over time, ISS has had about 21,000 man-days of astronaut time since its creation. That means the station has lost 42,000 hours of potential space research to this problem. The next space station should deal with it.

Designing a station with artificial gravity would undoubtedly be a daunting task. Space agencies would have to re-examine many reliable technologies under the light of the new forces these tools would have to endure. Space flight would have to take several steps back before moving forward again. But the cost of not having artificial gravity is proving to be massive, and it is an absolute requirement for manned exploration of our solar system to develop this technology. Either space agencies work on it, or they will simply stop advancing.

The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on

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