China is researching how to build ultra-large spacecraft up to 0.6 mile (1 kilometer) in length. But is the concept feasible, and what would be the purpose of such a massive spacecraft?
The project is part of a larger call for research proposals from the National Natural Science Foundation of China, a funding agency overseen by the Ministry of Science and Technology in China. According to a research outline posted on the foundation’s website, such massive spaceships would be “major strategic aerospace equipment for the future use of space resources, exploration of the mysteries of the universe, and long-term living in orbit.”
The foundation wants scientists to investigate new, lightweight design methods that could reduce the amount of construction material that must be lofted into orbit, as well as new techniques for safely assembling such massive structures in space. The feasibility study, if funded, would last five years and cost 15 million yuan ($2.3 million).
The project may sound like science fiction, but former NASA chief technologist Mason Peck says it’s not completely out of the realm of possibility, and the challenge is more one of engineering than fundamental science.
“I think it’s entirely feasible,” said Peck, who is now a professor of aerospace engineering at Cornell University. “I would describe the problems here as scale problems rather than insurmountable impediments.”
The cost of launching objects and materials into space would be by far the most difficult challenge, according to Peck. According to NASA, the International Space Station (ISS), which is only 361 feet (110 meters) wide at its widest point, cost around $100 billion to build, so building something ten times larger would strain even the most generous national space budget.
However, much depends on the type of structure the Chinese intend to construct. The ISS is loaded with equipment and designed to accommodate humans, which adds significantly to its mass. “It’s a different story if we’re talking about something that’s just long and not also heavy,” Peck explained.
Building techniques could also lower the cost of launching a massive spaceship into orbit. According to Peck, the conventional approach would be to build components on Earth and then assemble them in space like Legos, but 3D-printing technology has the potential to transform compact raw materials into structural components of much larger dimensions in space.
According to Peck, an even more appealing option would be to source raw materials from the moon, which has low gravity compared to Earth, making launching materials from its surface into space much easier. However, this would necessitate the construction of launch infrastructure on the moon, which is not feasible in the short term.
Big spaceship, big issues
A structure of such monumental proportions will also face unique challenges. When a spacecraft is subjected to forces, whether from orbital maneuvering or docking with another vehicle, the motion imparts energy to the spaceship’s structure, causing it to vibrate and bend, according to Peck. Because these vibrations will take a long time to dissipate in such a large structure, he believes the spacecraft will need shock absorbers or active control to counteract them.
Designers will also have to make careful trade-offs when determining the altitude at which the spacecraft will orbit, according to Peck. Drag from the outer atmosphere slows vehicles down at lower altitudes, requiring them to constantly boost themselves back into a stable orbit. This is already an issue for the ISS, according to Peck, but it would be a major concern for a much larger structure, which would have more drag acting on it and would require more fuel to boost back into place.
On the other hand, launching to higher altitudes is much more expensive, and radiation levels rapidly increase the further an object gets from Earth’s atmosphere, which will be a problem if the spacecraft houses humans.
However, while such a structure is technically feasible, it is not practical, according to Michael Lembeck, a professor of aerospace engineering at the University of Illinois at Urbana-Champaign who has worked on both government and commercial space programs.
“It’s like we’re talking about building the Starship Enterprise,” he explained to Live Science. “It’s fantastical, not feasible, and fun to think about,” he said, “but not very realistic for our level of technology.”
Given the research project’s small budget, Lembeck believes it is only intended to be a small, academic study to map out the very first contours of such a project and identify technological gaps. In comparison, the cost of developing a capsule to transport astronauts to the International Space Station (ISS) was $3 billion. “So the level of effort here is extremely low in comparison to the desired outcomes,” he added.
There are also concerns about the purpose of such a large spacecraft. According to Lembeck, possibilities include space manufacturing facilities that use microgravity and abundant solar power to create high-value products like semiconductors and optical equipment, as well as long-term habitats for off-world living. However, both would incur exorbitant maintenance costs.