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6 November 2014updated 26 Sep 2015 7:31am

Forever 20 years away: will we ever have a working nuclear fusion reactor?

Lockheed Martin has announced that it already has a small-scale fusion energy generator. In ten years’ time, it says, it will have developed a reactor large enough to power a city and small enough to sit on the back of a truck.

By Michael Brooks

There is an old joke that physicists like to wheel out every now and then. It goes like this: fusion power is just 20 years away and it always will be. The gag has been doing the rounds again, because the US defence research contractor Lockheed Martin has spoiled the punchline. It announced that it already has a small-scale fusion energy generator. In ten years’ time, it says, it will have developed a reactor large enough to power a city and small enough to sit on the back of a truck.

Make of this claim what you will; there is little evidence to support it. Most experts dismiss it as improbable – after all, we’ve been trying to achieve this since the 1920s; why would Lockheed Martin suddenly have the answer? (Cynics respond by muttering about share prices.) Common sense suggests we should just shrug our shoulders and wait and see. In a decade, we’ll know whether the claim was valid. Common sense, though, can be a dangerous guide: a decade is far too long to keep such a disaster-prone dream alive.

Nuclear fusion reactors subject hydrogen atoms to extremely high temperatures and pressures, fusing them together into one particle. This releases enormous amounts of energy. It’s not beyond us to do this – we achieved such “ignition” decades ago. The problem is that the energy release is not easy to control and it is even harder to sustain.

Fusion creates a hot, writhing cloud of electrically charged gas called a plasma. This is, in effect, corrosive to the reactor that created it and has to be kept away from the walls of its container using magnetic fields. Any contact with the walls also dissipates the plasma’s power and ends the fusion reaction. Even if the plasma is successfully confined, the bursts of high-energy neutrons released during the fusion process eat into the container walls, weakening them significantly. Many experts say overcoming such technical difficulties is still decades, if not centuries, beyond our capabilities. Some say it will never be possible, hence the joke and the scepticism about Lockheed Martin’s announcement.

Some who have scrutinised the company’s recent patents say notions of future success seem all the more far-fetched on close examination: the design is similar to ones that were abandoned in the 1950s. But it seems no one is quite ready to dismiss the claims fully. As Steven Cowley, the director of the Culham Centre for Fusion Energy in Abingdon, Oxfordshire, told the journal Science: “If it wasn’t Lockheed Martin, you’d say it was probably a bunch of crazies.”

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But it is Lockheed Martin, a company with enough credibility to make the experts waver. And that’s the problem. A fusion reactor would wean us off fossil fuels and make most problems of climate change go away. This makes the announcement that one is coming in 2025 a perfect defence for inaction. In the nightmare scenario, a congressman or two argues that there’s no point in introducing unpopular climate change measures as carbon dioxide generation is about to become a thing of the past.

Two years ago, a team of 18 researchers published a study in the journal Nature showing that, with current trends, 2025 will be the tipping point for the planet’s biological systems. That’s the year when ecosystems and resources will have become too damaged to recover, triggering an extreme disruption of human civilisation.

At best, Lockheed Martin’s announcement heralds a reactor that is likely to be too little, too late, if nothing is done to ease environmental pressures in the intervening years. At worst, it could tip us into a decade of complacency that ensures our nightmares become reality. No boast is worth that.