In his famous novel The moon is a cruel mistressRobert A. Heinlein describes a future lunar settlement in which future lunar residents (“loonies”) send loads of wheat and water ice to Earth using an electromagnetic catapult. In this story, a group of loonies conspire to take control of this catapult and threaten to “throw rocks at the Earth” unless they recognize the Moon as an independent world. Interestingly, scientists have explored this concept for decades as a means of transferring lunar resources to Earth someday.
As space agencies are planning to send missions to the Moon to create permanent infrastructure, there is renewed interest in this concept. In a recent paper, a team of scientists from the University of Science and Technology of China Shanghai Institute of Satellite Engineering (SAST) detailed how a magnetic launcher on the lunar surface could provide a cost-effective means of sending resources back to Earth. This proposal could become part of China's long-term vision for a lunar settlement known as International Lunar Research Station (ILRS), a joint project they are carrying out with the Russian space agency (Roscosmos).
According to a recent article published in the The South China Morning PostThe catapult would use magnetic levitation (maglev) technology and would operate on the same principle as the hammer throw in athletics, “but rotating at increasing speeds before launching the launch capsule towards Earth.” On the lunar surface, the near-vacuum environment and low gravity (about 16.5% of Earth’s gravity) gram) – would facilitate the ejection of payloads. According to the SAST team, the proposed system could carry out two launches per day at a cost ten times lower than that of existing transport methods.
As noted, the concept of a magnetic catapult on the Moon is an ancient idea. Earlier versions of the concept include the Hondatron Proposed in 1998 by the well-known physicist Derek A. Tidmanwhich envisaged a circular magnetic accelerator instead of a rotating arm. Similarly, the launch system proposed by the Chinese research team would consist of a 50-meter (165 ft) rotating arm and a high-temperature superconducting motor. It would be powered by solar panels and a nuclear reactor and is designed to convert kinetic energy into electricity during the deceleration phase. This would allow it to recover more than 70% of the energy consumed after each launch.
After accelerating for ten minutes, the arm would reach the Moon’s escape velocity of 2.4 km/second (1.5 mps) and release the payload on a trajectory toward Earth. The team also emphasizes that the primary payload would be helium-3 mined from lunar soil, which could be used to fuel fusion reactors on Earth. “The technical readiness of the system is relatively high,” they wrote. “Since it consumes only electricity and does not require any propellant, it will be relatively small in scale and easy to deploy. The primary goal is to extract and return helium-3 to help address Earth’s energy crisis. The project will also boost the development of space mining technologies, heavy launch vehicles, and artificial intelligence.”
Although only 0.5 metric tons (0.55 US tons) of the element is found on Earth, the Moon's regolith is estimated to contain 1 million metric tons (1.1 US tons). According to the team's paper, 20 metric tons (22 US tons) would be enough to meet China's annual electricity needs, while 1 million metric tons would be enough to meet the world's energy needs for more than a thousand years. They also estimate that the system will weigh about 80 metric tons (88 US tons) and could remain in operation for at least 20 years.
However, the construction of this system will have to wait until China has finished developing its Long March 9 (CZ-9) and Long March 10 (CZ-10) Super-heavy launch vehicles. These rockets are vital to creating the ILRS, which is expected to be completed by 2035 with the help of other national space agencies. As such, the proposed launch system could become part of China’s long-term plans for lunar development during the late 2030s or 2040s. The team’s proposed timelines are consistent with this: they hope to complete development of key components of the system by 2030 and anticipate full-scale deployment by 2045.
Of course, as with all other proposals for lunar construction and development, there is the issue of cost. According to the research team, the cost of building the launch system would be about $130 billion, equivalent to $18.25 billion. However, at last year's meeting of the China Association for Science and Technology (CAST), team member Chu Yingzhi claimed that extracting three to five tons of helium-3 per year could generate revenue of 100 billion yuan. There are also many technical and logistical challenges that need to be addressed before such a system can be built.
For starters, the research team’s paper doesn’t address how helium-3 will be extracted from the local regolith. As Chu noted, there’s also the challenge of installing it on the rugged lunar surface, ensuring the rotating arm remains stable at high speeds, and ensuring it can operate in the lunar environment, which is subject to extreme temperature variations, cosmic rays, and increased levels of solar radiation. But as a long-term vision, a magnetic launch system is an elegant proposition and a relatively cost-effective alternative to launching spacecraft from the surface.
Further reading: The South China Morning Post
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