Reel Science

The worst Tom Cruise sci-fi movie on Netflix reveals a possible path to nuclear fusion, physicists say

Turning seawater into energy might actually be a good idea.

Originally Published: 
Male and female lead from Oblivion sitting in sci-fi transport vehicle
Universal Pictures

Last week’s breakthrough in nuclear fusion technology dazzled the world. Now, the world is looking for ways we could actually use fusion to power our basic needs — and they may want to turn to Hollywood for inspiration. Yes, really.

Many movies and shows from Back to the Future to Star Trek have featured fusion technology, but only in the vaguest outlines. Yet there’s one underrated Hollywood blockbuster with a bizarre fusion technology that might actually work.

Released in 2013, Oblivion is a confusing hodgepodge of science fiction ideas from aliens to memory loss, but its clearest one comes in the movie’s opening scene when the main character Jack Harper (Tom Cruise) explains how he is trying to make the post-apocalyptic Earth livable for humans again following a nuclear war with aliens.

“We protect the hydro rigs, which convert Earth’s seawater into fusion energy for the new colony. The survival of humanity depends on it,” Harper says in the film.

But can we really convert seawater to fusion energy? Surprisingly, it’s not out of the question, fusion experts say — and it might even be plausible.

“This is scientifically realistic,” Troy Carter, a plasma physicist at the University of California, Los Angeles, tells Inverse.

Reel Science is an Inverse series that reveals the real (and fake) science behind your favorite movies and TV.

What is fusion technology?

A lot of weird stuff goes down in Oblivion, starring Tom Cruise and Olga Kurylenko, but its fusion premise is actually pretty realistic.

Universal Pictures

Before we can explain Oblivion’s kind-of wacky (but also sort of realistic) sci-fi premise, we need to understand how fusion works. Fusion energy involves turning hydrogen into helium, replicating the process that makes the Sun shine.

In last week’s fusion energy breakthrough, scientists at the Lawrence Livermore National Laboratory effectively created a fusion reaction similar to the one found in the center of the Sun. Using a giant laser, scientists shot 192 beams of energy onto a frozen pellet containing the hydrogen isotopes deuterium and tritium, heating them up to more than 3 million degrees Celsius. (An isotope is another form of the same atom with a different number of neutrons).

With this much energy, the capsule exploded, causing the hydrogen atoms to fuse into helium in less than a nanosecond.

But what was exciting about this fusion breakthrough was the end result: for the first time, scientists were able to generate more energy than they put into the fusion reactor — a breakthrough that was decades in the making. Scientists are hoping fusion will become a source of clean energy in the future, but its hefty cost makes it hard to scale up to the level needed to power our daily lives. The recent breakthrough only generated enough energy to boil 60 kettles of water.

How can seawater be used in fusion?

In Oblivion, Jack (Tom Cruise) guards a hydrothermal rig that extracts fusion energy from seawater.

Universal Pictures

Now, let’s explain how Oblivion re-imagines fusion in this futuristic sci-fi setting. Our main characters, Jack and Victoria are responsible for guarding massive hydrothermal rigs. These rigs are suspended in the air above the ocean, likely extracting seawater. It’s implied that some type of fusion reactor inside these hulking hubs turns the seawater into fusion energy that will enable humanity to return to Earth.

To the untrained eye, this premise might seem like Hollywood simply making things up so they look cool on the big screen, but fusion experts are actually tossing around the idea of converting seawater to energy in real life.

Carter explains that the easiest fusion reaction occurs between heavy hydrogen — deuterium, an isotope of hydrogen with a proton, a neutron, and an electron — and even heavier hydrogen — tritium, which consists of a proton, an electron, and two neutrons. This is also how the scientists at the Lawrence Livermore National Laboratory achieved their fusion breakthrough.

Hydrogen is necessary for fusion, and seawater contains an abundance of hydrogen in the form of H2O. Some of the water molecules used in nuclear fusion can also come from heavy water, which swaps hydrogen for deuterium.

“Deuterium is naturally abundant in water — fresh and seawater,” Carter says.

Another potential source of fusion is a rare — and radioactive — hydrogen isotope known as tritium. But there’s just one problem. “Tritium is not naturally available,” Carter says. “So it has to be manufactured.”

Seawater doesn’t have tritium, but it does contain the element lithium — and lots of it. According to Science, the world’s oceans contain 180 billion tons of lithium. Lithium is commonly found in batteries and electric devices, but Carter explains lithium can also be used to “capture” neutrons from fusion reactions and therefore “breed” tritium.

“Specifically if [lithium] absorbs a neutron, it will decay into tritium and a helium nucleus,” Carter adds.

This brings us to our next question...

Can we really turn seawater into energy?

A trailer for the 2013 sci-fi movie Oblivion.

Yes — but not right now. In a movie filled with otherwise wacky and implausible sci-fi devices, Oblivion manages to get one thing right: fusion energy. Just as Jack promises in the movie, there’s definitely enough energy in that seawater to enable humanity’s return to Earth.

“We don't currently ‘mine’ seawater for lithium, but if we were to do it — and extract the deuterium in heavy water — there would be many hundreds of thousands of years of fuel available,” Carter explains.

Oblivion is light on details, but here’s how Carter imagines you could churn seawater into fusion energy. The main obstacle: you need to get the deuterium and lithium out of the seawater. We already know how to remove deuterium from seawater, and scientists have proposed using electrodes to extract lithium.

“You would have to come up with some scheme to extract heavy water — and then separate out deuterium gas— and to extract lithium from the water,” Carter says.

Afterward, you’d put the lithium into a “blanket” that surrounds the plasma in a fusion reaction, enabling the lithium to capture neutrons from the reaction and breed tritium.

Nearly 10 years after Oblivion’s release, we are closer than ever to achieving its premise of converting seawater to energy. The Biden administration is banking on commercial fusion energy to power the clean energy sector and is now working toward developing a viable fusion plant. Carter also says private investors have dedicated $5 billion to fusion startups in recent years.

“We hope it is not far off,” Carter says. “There have been several important scientific and technological breakthroughs in fusion research in the last few years.”

So, we may not have to wait long to get the futuristic fusion that Oblivion promises, but hopefully, it’ll come without nuclear armageddon this time.

Oblivion is streaming now on Netflix.

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