How to build a large spacecraft
Need to retrieve a few tonnes of cargo from Mars? Send some seriously heavy gear into deep space? Fly out sufficient mass to deflect an asteroid? Current spacecraft would not be nearly big or powerful enough, say EU-funded researchers who have looked into a possible next-generation design based on nuclear electric propulsion.
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The DEMOCRITOS project has brought us a step closer to the large, fast craft of science fiction. Building on work carried out in earlier projects, it has identified suitable technologies, developed preliminary designs and boosted international cooperation in support of the required research.
From a technical point of view, the craft envisaged by DEMOCRITOS could be ready to take off within 20 or 30 years, says project coordinator Emmanouil Detsis of the European Science Foundation. It would be about 70 metres long, which is similar to the length of the International Space Station. Unlike the ISS, however, it would be equipped with a very powerful propulsion system that would open up entirely new possibilities, Detsis explains.
Lots of heavy lifting
The craft would be able to travel through the solar system delivering several tonnes of cargo to a robotic village on the Moon, for example. It could head out into deep space with far more scientific equipment and commensurately broader capabilities than earlier exploration missions, which involved much smaller craft.
And, in the event of an asteroid heading straight for Earth, it could be used to avert a disaster. A heavy spacecraft parked in orbit around such an object, Detsis explains, would produce a small, but significant gravitational force that, over time, would affect the asteroids trajectory.
The propulsion system would involve a nuclear reactor that produces heat to power a turbine that then produces electricity for the rest of the spacecraft, including the electric propulsion system. Known as nuclear electric propulsion, this system which has yet to be developed for space is the enabling technology that underpins the entire design.
Experts around the globe are conducting research relevant to this advance. Detsis says that DEMOCRITOS has boosted the dialogue between these groups across borders and disciplines. One particular objective, he notes, is to strengthen the interaction between the space engineering community and the world of nuclear engineering.
The project delivered initial technical designs of the craft with its various subsystems, and of a demonstrator that would serve to test and refine this system on the ground (using a different type of power source). It also looked into the practicalities of assembling the craft in space.
Into the unknown
Much more research, development and testing will be needed to turn the vision into reality. However, technology is not the only challenge. The legal issues surrounding the proposed nuclear core are daunting, Detsis observes, as the international framework relating to the use of a nuclear core in space would have to be adjusted.
It is uncharted territory, and he expects the process to take every bit as long as the remaining R&D. The bottom line, he notes, is that if you want to build in 2030, youd better start the legal process now.
You need to win several lotteries, too. Investments in the order of several billion euros, albeit commensurate with other large-scale space projects, would be needed to finalise the development, solve the various legal issues, assemble the required construction infrastructure in space and build a first craft.
Additional craft would, of course, be cheaper, Detsis explains, and the innovations involved are likely to benefit other industries. Aviation, for instance, would find many uses for the highly heat-resistant materials that need to be developed, he says, and the advanced robotics required to build the craft could be of interest to various sectors.
This is how the adventure will continue, since DEMOCRITOS ended in February 2017, by pursuing opportunities to advance the required technologies through developing applications for use in other sectors.
But ultimately, says Detsis, such a massive endeavour cannot succeed without the endorsement and active support of all space-faring nations, in the interest of humanity as a whole. It would involve an undertaking of the same magnitude as the ISS, requiring a similar level of international participation, he concludes.