Artist's illustration of a futuristic spaceship orbiting Earth. China's proposal is to investigate the possibility of mega spaceships measuring more than half a mile in length.
China is looking at ways to create ultra-large spacecraft up to 0.6 miles (1 kilometer) in length. How feasible is this idea? And what would the purpose of such a large spacecraft?
This project is part of an overall call for proposals from China's National Natural Science Foundation of China. It is a funding agency that is managed by China's Ministry of Science and Technology. The foundation posted a research outline on its website that described these enormous spaceships in terms of "major strategic space equipment for future use of resources, exploration of mysteries of the universe and long-term living within orbit."
The foundation is seeking scientists to investigate lightweight design options that can reduce the amount of material required to lift into orbit and how to safely assemble large structures in space. The feasibility study, if funded, would last five years with a budget of 15,000,000 yuan ($2.3million).
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Although the project may sound like science fiction, Mason Peck, former NASA chief technology officer, said that the idea is not completely out of reach and that the challenge is more engineering-based than fundamental science.
Live Science was told by Peck, a Cornell University professor of aerospace engineering. "The problems here are not insurmountable obstacles, but problems of scale," Peck said.
Peck noted that the cost of sending materials and objects into space is the greatest challenge. Peck stated that the International Space Station (ISS) is just 361 feet (110 m) in width at its widest point, according to NASA. It cost approximately $100 billion to construct. To build something 10 times bigger would be a strain on even the most generous national space budget.
It all depends on the type of structure that China plans to build. The ISS is loaded with equipment and designed to hold humans, which dramatically increases its mass. Peck stated, "If you're talking just about something long and not too heavy, it's a completely different story."
The cost of sending a massive spaceship into orbit could be reduced by using building techniques. Peck stated that the conventional method would have been to build parts on Earth, then assemble them in orbit like Legos. However, 3D printing technology could transform compact raw materials into space-worthy structural components.
Peck suggests that it is even better to source raw materials from moon, as its gravity is lower than Earth's. This would make it easier to launch materials from the surface of the moon into space. However, this first requires launch infrastructure on Moon and therefore is not feasible in the short-term.
Big spaceship, big problems
The unique challenges that a structure of this size will face is not only the cost but also the difficulty of maintaining it. Peck explained that spacecrafts are subject to forces when they maneuver in orbit. These vibrations can take a while to subdue because of the large structure. Therefore, shock absorbers or active control will likely be required to stop them.
Peck stated that designers will have to make compromises when deciding at what altitude the spacecraft should orbit. Lower altitudes are where vehicles are impacted by the drag of the outer atmosphere. This causes them to slow down and must be constantly boosted back into a stable orbit. Peck pointed out that this is an issue already for the ISS. However, for a larger structure with more drag and requiring more fuel to propel back into place, it could be a serious concern.
However, higher altitudes are more costly and radiation levels rise quickly as objects move further away from Earth's atmosphere. This can be problematic if the spacecraft contains humans.
However, while such a structure may technically be possible, it is not practical, according to Michael Lembeck, an Illinois University professor of aerospace engineering who has worked on both commercial and government space programs.
He said that it was akin to us discussing the Starship Enterprise. He said that it was impossible, not possible, and fun to imagine, but not realistic for our technology level.
Lembeck stated that the budget for the research project is very small and it was likely to be an academic study to identify gaps in technology and map the early contours of the project. The budget for building a capsule that would carry astronauts to the ISS cost $3 billion. He said that the effort required to achieve the desired outcomes is very low.
It is also unclear what this large spacecraft could be used for. Lembeck suggested that space manufacturing facilities could be built to take advantage of microgravity, abundant solar power and build high-value products such as semiconductors and optical equipment. Or long-term habitats for offworld living. Both would require huge maintenance costs.
Lembeck said, "The space station costs $3 billion per year." Multiply this for larger facilities, and it quickly becomes an expensive and large enterprise to manage.
China is also interested in large-scale solar power arrays that are placed in orbit. The power can then be beam back to Earth using microwave beams. However, Peck stated that the economics of such an endeavor don't make sense. Peck did some calculations back-of the envelope and estimated that it would cost approximately $1,000 per watt compared to just $2 per per watt for solar energy produced on Earth.
Peck stated that science is the most promising use for such a large structure in space. An enormous space telescope could possibly see features on other planets' surfaces. He said, "That could transform our understanding of extrasolar solar planets and possibly life in the universe."
Original article at Live Science
