Destination: Alpha Centauri – a triple system of stars located some 4.37 light years away from the Sun and our closest stellar neighbours. This system could have at least one planet, an Earth-sized world called Alpha Centauri Bb and perhaps there could be more. If we want to learn about and explore other stars and exoplanets, Alpha Centauri is our best bet but, even though it might be relatively close, getting there will be a feat in itself.
That’s what Project Icarus is all about. A joint project between the British Interplanetary Society and Icarus Interstellar, its goal is to design a starship using current or near future technology. As part of its development, Project Icarus members were encouraged to form teams to design possible propulsion schemes using nuclear fusion that could feature in the final Icarus design. The winning starship was the Ghost Ship, led by Andreas Hein of the Technical University of Munich. While the Ghost Ship is still only a concept, the sophistication of its ignition system could be the way forward when it comes to interstellar travel.
Nuclear fusion is a popular means of generating energy when scientists consider how to reach the stars. Fusion, which involves two atoms, such as deuterium, tritium or helium-3, fusing into one, releasing energy in the process, is far more efficient than nuclear fission, which splits atoms and is what runs our nuclear power stations today. In the 1970s Icarus’ ancestor, a British Interplanetary Society project called Daedalus, showed that a fusion-powered starship could reach about ten percent of the speed of light meaning it would take 43.7 years to reach Alpha Centauri.
Ghost Ship would be a little slower, accelerating for a 15.5 years up to six percent of the speed of light, after which the 153,800-ton craft cruises through interstellar space for 54 years. It does this using a method known as Inertial Confinement Fusion fast ignition. Here, 150 tiny pellets of deuterium are heated by powerful lasers every second, until they grow so hot and dense that the atoms inside the pellets begin to fuse, expelling large amounts of energy and lots of high energy neutrons. This neutron radiation can be extremely dangerous, so the engine is separated from the rest of the starship on a long boom. However, the neutrons can also be gathered and recycled to provide the additional energy to power the lasers that ignite the fusion and create more of these neutral subatomic particles.
Once the ship begins to get close to Alpha Centauri, it will deploy a magnetic sail that would drag on the hydrogen gas that lurks in deep space, slowing Ghost Ship down to one percent of the speed of light before firing its fusion engine in reverse to complete the deceleration. Probes with some carrying rovers, desperate to uncover the secrets of our nearest star system, are then launched to explore the stars and planets of Alpha Centauri.
Image Credit: Adrian Mann