Netflix’s Stowaway nails the science of space survival

A group of astronauts accidentally carry an extra passenger with them on a long space mission. But does the science stack up?

Stowaway was born from a single image. Cowriter and director Joe Penna imagined a beautiful shot of Earth from a space shuttle. It was instantly accompanied by dialog—Penna knew that he wanted the crew onboard to be discussing whether or not they had to kill someone.

After much to-ing and fro-ing with his cowriter Ryan Morrison, the pair decided that the plot for Stowaway, which is released on Netflix this week and stars Toni Colette and Anna Kendrick, would revolve around a trio of astronauts on a mission to Mars who discover an accidental stowaway shortly after takeoff. Unable to turn around, they continue on to the planet. But when their resources start to dwindle they soon have to contemplate the unthinkable.

The hook, tension, and drama of Stowaway was immediately obvious to Penna, whose directorial debut Arctic was also a survival thriller set thousands of miles away from civilisation. But one question consumed him before he could begin to work on the script. Could someone actually stowaway on a space flight?

Penna immediately set out on an extensive research mission to find out. “We just started cold calling a bunch of astronauts,” he says. They were wary—several had been “burned by various Hollywood productions.” He managed to squash their concerns by insisting that they wanted to make a real space movie, one where the colour of the buttons, the width of the halls, and the height of the ceilings were all right.

As for the vital question, Penna made sure to highlight that the individual had to have stowed away by accident, otherwise the dynamics of the film wouldn’t work. NASA told them it could “absolutely” happen, Penna says—although the US space agency was quick to argue that it wouldn’t be their fault if it did. “They said, ‘Well, absolutely. Look at all these new space companies. They get a little cavalier with their launches. Once they start doing manned missions, you know, maybe they'll do something wrong,’” Penna says. When Penna and Morrison started to talk to some of these other companies, though, they agreed that the inciting incident of Stowaway could take place, but they said NASA were just as likely to be the ones that committed it. They told Penna that NASA had “bundled things a bunch of times. They’ll do it. Not us.”

But what would actually happen if there was an unintended extra passenger on an interplanetary mission? And how would it impact the delicate systems that astronauts rely on to survive? Alex Ellery, a professor of mechanical and aerospace engineering at Carleton University in Ottawa, says they’d be discovered quite quickly, as the oxygen consumption onboard would increase dramatically, and that is monitored constantly.

If the mission to Mars continued, Ellery believes that the four person crew would be able to survive on the amount of food for three, as they could partake in the starvation mode diet. This is the idea that, if you reduce your calorie intake by around either 25 per cent or 30 per cent, you can actually extend your life. When it comes to water and oxygen, as long as the shuttle’s recycler machines can “take the capacity,” then there shouldn’t be too much of an issue, he says.

In Stowaway, though, the astronauts are put into substantial peril because the ship’s carbon dioxide removal assembly is destroyed. Ellery still thinks there’s a way around this, as a real crew would be able to build a new carbon dioxide recycler. Since they’re on a two-year mission, the crew would have manufacturing capabilities onboard, most likely in the shape of a 3D printer, as well as a milling station.

This means they could build pretty much thing they need, including a Sabatier reactor. This is where either a nickel or aluminium catalyst interacts with hydrogen and carbon dioxide at a certain temperature to create water and methane. The water is then used (and can be used to make oxygen), while the methane is vented outside into space.

“Once that’s going it’s self-sustaining,” says Ellery. “So effectively you’ve created your own recycling device to convert your carbon dioxide into oxygen. I don’t think it would be that difficult to do that.”

So that’s biology sorted, but what about the psychological impact on the crew? Lawrence Palinkas of the University of Southern California has spent many years discussing the behavioural and psychological aspects of long term isolation, confinement, and extreme environments, and believes that the stowaway would struggle to become an integral member of the crew, as the others will have spent a long time together already, particularly in the build up to the launch.

“All the training that occurs gives them an opportunity to bond with one another and to identify what each other's personality quirks, strengths and weaknesses and so forth are,” he says. “When you throw someone into that mix at the last minute, that person often ends up being ostracised from the rest of the crew. So the psychological ramifications would be significantly higher for that person.”

The other questions that audiences might have about the film is a simple one. Wouldn’t the crew of a space mission, once they’d discovered they’d accidentally taken someone else along for the ride, just turn around? “There's no friction in space,” explains Penna, whose film highlights the fine margins involved in space travel. “A lot of people think that space travel is like car travel, where if you're not accelerating you can just stop, turn around, and start accelerating the other way. You only bring enough fuel for adjustments in space. Because if you bring one pound of rocket fuel, you need two pounds of rocket fuel underneath that to just get it up into space. Every single gram counts and your margins are tiny, tiny, tiny.”

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This article was originally published by WIRED UK