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 the National Natural Science Foundation of China. It is a funding agency run by the Ministry of Science and Technology. The foundations website posted a research outline that described these enormous spaceships in terms of major strategic aerospace equipment, long-term living in orbit, and exploration of the mysteries.
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).
Although the project may sound like science fiction, Mason Peck, former chief technologist at NASA, said that the idea isn't completely out of reach and that the challenge is more engineering-based than fundamental science.
It is possible, Peck, a Cornell University professor of aerospace engineering, said to Live Science. These problems are not insurmountable obstacles, but problems of scale.
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. This significantly increases its weight. Peck stated that if you are talking about something long and not too heavy, it is a 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. Moon gravity is lower than Earth's, making it easier to launch materials into space from its surface. 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 be very strong and will not subside quickly due to the large structure of the spacecraft. 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 altitude launches 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 a lot like us discussing building the Starship Enterprise. He said that it was impossible, unrealistic, and entertaining to consider, but not realistic at our current level of technology due to the cost.
Lembeck stated that due to the small budget of the research project, it is unlikely to be an academic study. It will map out the earliest contours and identify technological gaps. To put that in perspective, $3 billion was spent to build a capsule capable of carrying astronauts to orbit. 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 that the space station costs $3 billion per year. It quickly becomes an expensive, large-scale enterprise that is difficult 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 stack up. Peck did some calculations back-of the envelope and estimated that it would cost approximately $1,000 per watt compared to just $2 per 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 this could help us understand extrasolar planets, and possibly life in the universe.
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