Autumn 2013 science news included a relatively subdued report from the BBC, noting that, “Researchers at a US lab have passed a crucial milestone on the way to their ultimate goal of achieving self-sustaining nuclear fusion.” Scientists at the National Ignition Facility (NIF), California, had focused laser beams to heat and compress a small pellet of hydrogen fuel and achieved a world first: more energy was released through the fusion reaction than was absorbed by the fuel.
Perhaps this brings us a step closer to harnessing the power of stars, where extreme temperatures and pressures cause atomic nuclei to combine forming larger elements and with slight mass loss accompanied by intense energy release. These fusion processes can start with hydrogen, helium and lithium that formed in the Big Bang, and evolve elements as heavy as iron – after which, you need a supernova to unleash the forces needed to combine nuclei and supply energy to create heavy elements.
Here on earth, there is potential for deriving virtually unlimited clean energy from fusion power, without the severe downsides of nuclear power based on splitting atoms apart, like radioactive waste and chance of meltdowns. But the lower gravity makes even combining hydrogen nuclei extremely challenging. Hydrogen bombs developed in the early 1950s involved regular nuclear explosions to initiate fusion: hardly suitable for your neighbourhood power station!
Several projects are underway in the quest to discover ways to harness fusion power, which is akin to a holy grail of nuclear physics. “Fusion is a nearly ideal energy source – essentially inexhaustible, clean, safe, and likely available to all nations. When proven practical, it will transform our energy future,”
Stewart C. Prager, director of the US Department of Energy’s Princeton Plasma Physics Laboratory, wrote in a commentary on the New York Times website last year.
Culham Centre for Fusion Energy, the UK’s national laboratory for fusion research announces careers in fusion with the slogan, “Come to work to change the world.” Work there focuses on initiating fusion within plasmas – extremely hot mixes of atomic nuclei stripped of their electrons – contained within magnetic fields. The devices used are tokamaks, devices shaped like giant doughnuts that were invented by Soviet scientists in the 1950s.
While Culham currently hosts the world’s largest tokamak, an even grander one is being built in the south of France. Dubbed Iter – after Latin for “the way” – this is the largest scientific collaboration in the world. The reactor is 30 metres tall and, according to the Independent, the plasma will be contained by, “Giant electromagnets powerful enough to trap an aircraft carrier.” By heating hydrogen atoms to over 150 million °C – ten times the temperature required for fusion in the sun – researchers anticipate that they will achieve a net gain in energy,.
Even so, Iter will be an experiment rather than a power station. And you should not get too excited just yet, as actual trials with plasma may be a decade away.
While tokamaks are receiving the most funding and attention, there may be other ways of generating fusion power. The National Ignition Facility’s project is among these, with super cooled hydrogen fuel that is suddenly heated by converging 192 beams from the world’s most powerful laser, which arrive within 30 trillionths of a second of each other.
If fusion power proves viable, it could help space travel. Last month, Time reported on a US company, Princeton Satellite Systems, which is small but has big ambitions, with ideas including a fusion rocket for Mars that would be smaller than a minivan.
This seems far-fetched given the size of facilities like Iter and the National Ignition Facility. Yet the science does indicate the potential, given that weight for weight, fusion of hydrogen could generate up to 10 million times the energy of burning coal.
Steve Cowley, director of the Culham Centre for Fusion Energy, told Popular Mechanics that the main barrier to fusion power on earth is getting government funding. “For $20 billion in cash,” he said, “I could build you a working reactor.”
As another indicator of stumbling blocks arising from human failings rather than pure science, Iter has encountered hold ups including a giant magnet that had to be scrapped after a worker left a towel that became compressed within a coil. And you have perhaps heard little of the milestone at the National Ignition Facility because researchers haven’t been around to speak of it this month: they were laid off as the US government shut down.
NASA website includes info on this:
The Direct Fusion Drive (DFD) concept provides game-changing propulsion and power capabilities that would revolutionize interplanetary travel. DFD is based on the Princeton Field-Reversed Configuration (PFRC) fusion reactor under development at the Princeton Plasma Physics Laboratory. The mission context we are proposing is delivery of a Pluto orbiter with a lander.