“There’s helium 3 in the gas giants like Jupiter, absolutely loads of it,” says Long. Apart from the enormous thrust such a system could generate – well in excess of conventional rockets – as you travel around the cosmos you could tap into a ready supply of suitable fuel, such as helium 3. One, funded by Nasa, involves a contained atomic reaction that generates a focused beam of charged particles to push the starship along. Undeterred, various concepts for fusion engines have been proposed. There is an in-joke among fusion engineers (and their journalist followers) that a viable fusion power plant is always 30 years away. However, as anyone who has followed the field knows, despite the multi-billion-dollar global effort that has gone into fusion research over the past half century, no one has yet built a fusion reactor that produces more energy then you put in. If you can do it you can produce a power generation system which will move you outside the Solar System and you don’t have to come back for more rocket fuel.” “Fusion produces much more energy, in terms of bang for your buck, compared to fission-based systems,” says Long, explaining why his group’s starship designers favour fusion propulsion. It is what powers the Sun, and the hydrogen bomb. In the fusion process, on the other hand, the nuclei of atoms are forced together to release energy. It is a well established, but not incident-free, science. Conventional nuclear power stations and the generating plants on nuclear submarines and ships use the technique to make electricity. “You can get much more efficient power generation from nuclear systems, such as fission or fusion.”įission involves splitting atomic nuclei in a controlled chain reaction to produce energy. “It’s all about generating enormous amounts of energy,” says Long. To achieve this goal, the ships will need much more powerful propulsion systems than conventional chemical rockets or solar-powered probes. There are several other programmes underway, including the 100 Year Starship project backed by the US military research agency, Darpa. A starship travelling at thousands of kilometres per second could reach Mars in weeks, the outer solar system in months and other star systems in years. Long’s immediate future involves helping to design a starship – a robotic craft that could travel at high speed beyond our Solar System to other nearby stars. “People who are excited about this stuff don’t live in the present, we live in the future.” “Orion was a visionary project,” says Kelvin Long, physicist, engineer and head of the Initiative for Interstellar Studies. But as ambitions for missions deeper into our solar system grow, much larger spaceships propelled by more powerful nuclear generators are back on the agenda. With no moving parts, RTGs are not nuclear reactors and can only generate a few hundred watts of power (the equivalent of a bright lightbulb). These Radioisotope Thermoelectric Generators (RTGs) rely on the natural decay of plutonium to generate heat, which is then converted into electricity. The Voyager space probes, currently heading beyond the bounds of the Solar System, and the Cassini spacecraft in orbit around Saturn are fitted with nuclear power plants. In fact there are several in the cold depths of space right now. In the early 1960s, common sense prevailed and the project was abandoned, but the idea of nuclear-powered spaceships has never gone away. Project Orion was conceived when atmospheric nuclear tests were commonplace and the power of the atom promised us all a bright new tomorrow. But the plan was, nevertheless, given serious consideration.
There were obvious challenges – from irradiating the crew and the launch site, to the disruption caused by the electromagnetic pulse, plus the dangers of a catastrophic nuclear accident taking out a sizable portion of the US. The quickest flight using conventional rockets and the right planetary alignment is 18 months. Plans suggested the spacecraft could take off from Earth and travel to Mars and back in just three months. The Orion’s engine would generate enormous amounts of energy – and with it lethal doses of radiation. This 1950s design involved exploding nuclear bombs behind a spacecraft the size of the Empire State Building to propel it through space. Project Orion has to be the most audacious, dangerous and downright absurd space programme ever funded by the US taxpayer.