A pre-research paper published in Scientia Sinica Technologica by a group of space veterans outlines the spacecraft‘s design, scientific goals and, crucially, plans for its nuclear fission reactor to generate electricity.
The power source will provide game-changing power for scientific payloads, data downlink capabilities and high-capacity electric propulsion systems.
This would represent a major technological leap in the nation’s space exploration capabilities, producing much more energy than battery-like radioisotope thermal generators (RTGs), opening up new possibilities.
This new spacecraft power source will make it easier to enter the outer solar system, where human space exploration missions rarely set foot. So far, only one mission, Voyager 2, launched in 1977 and flew past the icy giant in 1989. Its flyby visit with a limited set of instruments is significant, but there’s still a lot to discover about our solar system’s eighth planet.
Meanwhile, China launched its first interplanetary mission, Tianwen-1, in July 2020, placing a spacecraft in orbit around Mars and placing a solar-powered rover on the Martian surface car.
Expeditions into alien systems are rare, and there’s a reason the two ice giants, Uranus and Neptune, haven’t visited other than by passing by. The challenges come from the supply of electricity — Neptune’s average distance from the sun is 4.495 billion kilometers, and the acceptable sunlight is only 1/900 that of Earth — as well as communicating over vast expanses of land, as well as the need to reach the far corners of the system. time. Getting into orbit around the planet also requires massive amounts of decelerating fuel and a spacecraft capable of operating in extreme environments for at least 15 years.
Overview of the Neptune Orbiter
The proposed mission outline identifies a 2030 launch window for the probe to be launched on a Long March 5 rocket. It will fly by Jupiter to a distance of about 30AU to Neptune in 2040 and enter a polar orbit around the ice giant.
The purpose of the mission is to provide new insights into the outer solar system, the origin and evolution of the solar system and the potential origin of life, the researchers said.
To help address the aforementioned engineering and technical challenges and answer some of Neptune’s scientific mysteries, the Chinese team proposes a 10kWe nuclear fission reactor.
The reactor will generate the electricity needed to power the spacecraft’s payload in deep space and the propulsion system of its four electric thrusters. The spacecraft will have a mass of up to 3,000 kilograms and a dumbbell-shaped structure to keep the reactor as far away from the scientific payload as possible, reducing the need for heat and radiation shielding. The proposal also details international standards for the use of nuclear power in space.
Science objectives include global remote sensing and the study of Neptune’s internal structure, atmospheric composition and motion characteristics, magnetic field, solar wind, and the planet’s moons and ring systems.
The main spacecraft will also carry four microsatellites with a combined weight of 100kg. Two will be used as penetrators — targeting Neptune’s atmosphere and Triton, respectively. The other two can be released on the way to Neptune to visit the primordial celestial body.
Professor Leigh Fletcher from the School of Physics and Astronomy at the University of Leicester, UK, pointed out that with the U.S. decadal survey recommending the Uranus mission as the top priority for the next decade, a thorough exploration of the Neptune system is a future goal to look forward to.
“I think our understanding of the formation and environment of the solar system is still incomplete until we have a proper comparison of Uranus and Neptune,” Fletcher said. “You need a complex orbiter with a payload that can explore the planet itself and various Moons and rings. For that, you’re going to need a full orbital trip, and that requires fuel and a long lifetime.”
In addition, he added, Triton, with its astonishing geophysical activity and plumes, is a particularly enticing target. Triton, the largest of Neptune’s 13 known moons, has a retrograde orbit, an ice cap of frozen nitrogen and methane, and may be an ocean world.
China’s interest in space nuclear power
Wu Weiren, a leader in China’s space exploration and director of the newly established Tiandu Deep Space Exploration Laboratory, called for breakthroughs in space nuclear power to reach 10, 100 and 1000kWe in stages according to development trends and the requirements of future missions. It is clear, however, that Chinese researchers are evaluating international advances and possibilities in this field.
More practically, there are already proposals for reactors in Chinese space missions — including uranium-powered ACMIR. Further indications that nuclear power is part of China’s future space exploration plans can also be seen in the fact that China is considering adding a third spacecraft to its planned mission to study the head and tail of the heliosphere. If selected, this additional probe will drive away from the sun perpendicular to the ecliptic plane and be powered by a nuclear reactor.
Commenting on the use of nuclear fission in space, Tom Colvin, a researcher at the IDA Institute for Science and Technology Policy, noted that nuclear fission reactors are uniquely suited to power and propulsion for robotic missions to exoplanets, as well as to Manned missions to the surface of Mars. Developing fission reactors for these missions will involve countless technical challenges, though he noted that there are no barriers, “it just takes time and money”.
According to the World Nuclear Association, Russia has used more than 30 fission reactors in space, while the United States has flown just one. The SNAP-10A (Nuclear Auxiliary Power System) in 1965. However, NASA is currently working on a fission system to power lunar surface missions under the Artemis umbrella.
Will the Neptune Orbiter fly?
There is no indication yet of the status of this pre-research publication funded by the China National Space Administration. However, the proposal strongly indicates and reflects the direction of Chinese aerospace industry officials in terms of exploration capabilities and destinations.
It is reported that the institutions behind the research include the China National Space Administration, the two major satellite manufacturers (CAST and SAST) under China’s major aerospace contractors, the School of Nuclear Science and Technology of Lanzhou University, the China Atomic Energy Agency, and the China Institute of Atomic Energy. , affiliated institutions of the Chinese Academy of Sciences and Beihang University and Peking University.
On the engineering side, it will require breakthroughs in key technologies, including powering space reactors and ultra-long-range deep space tracking and control. While presenting challenges, they will also help achieve China’s stated national goal of becoming a major space power.
With these advances, Neptune could become part of China’s exploration roadmap, which already includes Mars sample returns, near-Earth asteroid sample returns and studies of main-belt comets, as well as a Jupiter mission with a potential flyby of the ice giant. The chances of a Neptune mission may depend on engineering progress and funding in the coming years.
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