Fusion energy is an often misunderstood concept. A few common ideas, such as that fusion is dangerous, and that fusion does not produce as much energy as is required to spark a reaction, are simply not true. Nuclear fusion is a safer, cleaner alternative to fission, and due to its extremely high potential fuel efficiency, could represent the next step in powering interplanetary and even interstellar spacecraft.
Nuclear fusion works in almost exactly the opposite way to fission. Where fission splits atoms to release a portion of the energy contained in their mass, fusion fuses two or more atoms, releasing energy determined by the difference in mass. This is the process by which the sun is fueled – fusing hydrogen atoms into helium.
The first time nuclear fusion was achieved by human beings was, as ever, destructive. The 1951 Greenhouse Item nuclear fission bomb produced enough heat at the core of the detonation to induce fusion, this ‘success’ led to the 1952 Ivy Mike bomb, the first nuclear device to directly use nuclear fusion to contribute to it’s yield. These were in no way the stable fusion reactions we study as the future of energy today, but they proved that it was indeed possible for humans to harness the power of fusion.
Research into harnessing fusion for energy development began in the same decade with concepts such as the ‘tokamak’ magnetic containment device and the brilliantly named ‘perhapsatron’. The first evidence of controlled nuclear fusion was produced by the ZETA project at Harwell in the UK, using the ‘Z-pinch’ method to confine the plasma. In 1968 a Russian team successfully tested a tokamak device and the tokamak concept remains at the forefront of nuclear research today.
The current largest fusion experiment is the ITER project, run by a co-operation of thirty five nations. Construction of a tokamak reactor in France – this time with the theoretical capability to produce ten times the power required to sustain the reaction – began in 2006 and will be completed in 2019. Further advancements in tokamak nuclear fusion were made by the German W7-X reactor at the Max Planck Institute, where a small fusion reaction was successfully contained in a magnetic field.
So why is fusion so important to the future of space travel? Many of the propulsion methods we anticipate using in the future require huge amounts of power, be it the increasingly less controversial Em Drive, or laser guided solar sails. Not only is fusion safe, it produces no radioactive waste and if the containment field failed the reaction would simply collapse, it can produce huge amounts of energy from very small reactions. A deuterium-tritium fusion can produce 17MeV from just two hydrogen atoms. With this kind of energy available to us, a lot of presently hypothetical space exploration methods become possible.
The helium by-product of hydrogen fusion may also make high altitude ballooning a shade cheaper, who knows?