Before his novel The Martian became a bestseller and inspired a Ridley Scott blockbuster, Andy Weir was a computer programmer who read lots of science fiction and researched the intricacies of human space travel in his spare time. He’s been able to quit his day job, but he’s still more than happy to give detailed explanations of the science behind interplanetary space travel. We chatted recently about his book, the movie, and the challenges of reaching and surviving on a hostile, distant planet.
The Daily Beast: How did you get the idea for this novel?
Andy Weir: I was sitting around thinking about how a manned mission to Mars could work. Because I’m that kind of dork. We’d need to get people there, get them to and from the surface, then get them home. Most importantly: what do we do when things break? The crew and the ship can’t be Earth-dependent. I realized that the science of all that makes a pretty interesting story.
What did you think of the movie?
Matt Damon totally nailed the character. I think they did a fantastic job. Drew Goddard, who wrote the screenplay, called me almost every day for a while. He had a bunch of technical questions. In cases where something would cause scientific inaccuracies, I would say there was a problem. I got a question filtered down to me from Ridley Scott on whether we could have Mark’s character pouring hydrazine from one container to another on the surface of Mars. The atmosphere is so thin that it would immediately boil off and turn into vapor. So in the movie he hooks up a hose to transfer it. Little stuff like that.
Are there any glaring scientific inaccuracies in the book or movie?
The biggest one is the sandstorm at the beginning. It’s not realistic at all. Mars does get 150 km/h winds, but the atmosphere is so thin that the inertia behind the wind is super gentle: it would feel like a slight breeze. It couldn’t knock anything over or cause damage. I knew this when I wrote it but I decided, screw it—this is more exciting. It’s a man-versus-nature story, and I wanted to make sure nature got the first punch in.
There are some things we now know are inaccurate which we didn’t know when I wrote the book. In the last six years we’ve actually learned a lot about Mars. There’s a lot more water in the soil than we suspected. Every cubic meter of soil contains about 35 litres of water as ice. So all Mark would’ve had to do was take the sand and heat it up to boil the water out. No need to do the dangerous hydrazine reduction.
Another issue that I kind of skirted is the radiation in space. On earth we’re protected by the magnetosphere and the thick atmosphere. But on the surface of Mars there’s a thin atmosphere and no magnetosphere. It would be a very serious dose of radiation for him to be on Mars for 500 days. The kind of dose where you definitely get cancer. I have two paragraphs in the book where I was just like, everything is shielded somehow. Turns out there’s no such thing as thin light flexible radiation shielding. It takes a centimeter of lead or 10 cm of water or a full meter of rock to protect you from galactic radiation. So I made up a fake material that doesn’t really exist.
I actually calculated the orbital trajectories that they needed to take to get from Earth to Mars. That’s a real thing that would work. But the movie changed how long the crew spent on the planet for a funny reason. In the book they left after sol six, but in the movie they leave after sol 18. Ridley wanted Mark to stir a nice big bucket of shit when he was creating the fertilizer for the crops. Ridley said, after only six days of six people shitting that’s 36 packets. He wanted them to stay longer, so that the bucket of shit could be full.
How far away do you think we are from human travel to Mars?
NASA says the 2030s. I don’t doubt that they could achieve that if they had enough funding. But I don’t think they’ll be given enough funding. 2050 seems more plausible.
What do you think of initiatives like Mars One?
I don’t take it seriously at all. People just don’t understand how expensive it is to go to Mars. We are talking tens of billions of dollars—it’s a thing that governments the size of the United States balk at. Mars One doesn’t have enough money to colonize Nebraska, let alone Mars. Their plan for generating revenue is a reality TV show. But just think about the numbers. They estimate that the trip will cost $36 billion. It’s simply not possible to make that much from TV. The program with the highest television revenue ever is the Summer Olympics. It’s broadcast every four years for 16 days and makes about 4 billion in revenue worldwide. Their little reality TV show would have to make nine times as much as the summer games.
Imagine you had a 10-year-old son and you come home one day and he’s in the living room with some friends taping cardboard together. If he says he’s building a rocket to go to Mars, you would not take his plans seriously and subject them to analysis by MIT or write articles about them for The New York Times. I don’t understand why anyone takes Mars One seriously.
Is Elon Musk worth taking seriously?
SpaceX is very different. They put things in space for pay. They are a real company. I think things like SpaceX are the way to drive down the price of getting people and materials to low Earth orbit. If that price drops low enough, there will be a market for commercial space industry. Imagine if for 50,000 bucks you could get in a spaceship and spend a week in a hotel in orbit around Earth. Maybe have some zero-gravity fun, and it’s all just as safe as commercial aircraft. $50,000 is something that a lot of people worldwide would pay.
What is the main obstacle preventing human travel to Mars?
Everything is about putting mass in low Earth orbit. It’s all about escaping Earth’s gravity. So as commercial space flight drives the LEO cost down, the cost of getting to Mars will also drop dramatically. The vast majority of money that would be spent on a manned mission to Mars would be spent on getting stuff into low Earth orbit.
Despite the intentional nostalgia for the Apollo-era in the book, I think the first effort to Mars will be an international collaboration between Russia, India, Europe, America, Japan, and possibly China.
What are some other major challenges?
A huge problem is the lack of Earth-dependence. Even on the international space station, where people stay for six months or even a full year, they have the option to depart at a moment’s notice. They can get into a capsule that is basically a lifeboat and return to Earth. The whole station could go to hell—it could spring a leak, all systems could fail, and the astronauts would likely return to Earth and be fine.
When you’re going to Mars, that’s not an option. Anything that is mission-critical needs to be 100 percent reliable or have multiple backups or be fixable.
Another huge challenge is dealing with the long-term effects of weightlessness. I honestly believe there is no cure for zero gravity. There’s bone density loss, vision and immune problems—in short the human body just did not evolve to live without gravity. We will have to work on centripetal gravity. In the film, there’s the gravity wheel, which is functionally equivalent to the gravity on earth. The science is pretty simple, but the design and engineering would be difficult.
Another problem is radiation from galactic cosmic rays. These are actually particles that stars spew out at incredibly high speeds. They hit your body and destroy DNA. To guard against them you need lead, water, or rock, all of which are heavy. Water is very good at soaking up radiation, so maybe you store the water supply in a 10 cm baffle surrounding the entire ship, and as you deplete the water supply you replace it with sewage. That’s one possible solution, but it costs you a bunch of mass.
Yet another problem is staying on Mars and surviving for a long time. Oxygen and water are not very difficult to solve, but you can’t pull food from the Martian atmosphere, and it takes a ridiculous amount of land to grow food for just one person. You would not want the astronauts to be at risk of the crop failure either. Which means you have to send a year-and-a-half worth of food with them.
Do you think humans need to be a multi-planet species in order to survive?
Our chances of extinction drop exponentially if we can colonize another planet or planetoid, but I don’t delude myself into thinking that this would be easy. Mars is particularly challenging, it would be far easier to colonize the ocean floor, the Sahara, Antarctica, or even the moon than Mars. Anyone who thinks that we can destroy our own planet and go find another is not really thinking.