Naoji Yamamoto is a young rocket scientist leading Japan’s aerospace engineering R&D to launch next-generation rocket engines far into the future. A native of the Kansai region, Professor Yamamoto has a warm, gentle smile that belies a relentless curiosity and drive that fuels his every endeavor. Professor Yamamoto’s motto is inspired by the words of his college mentor: “Study in engineering department is meaningless unless it is put to practical use."
Born in Osaka, Professor Yamamoto spent his childhood playing baseball and soccer and for a time dreamed of becoming a pilot. His curiosity led him to study all kinds of subjects at junior high and high school, from space science to biology and archaeology. For university, his desire to learn aerospace engineering and live on his own led him to apply to the University of Tokyo, where he was admitted to the Natural Sciences I junior division. Before graduating from the Department of Aeronautics and Astronautics at the Faculty of Engineering in 1999, he had already begun his research on Electric propulsion (EP), simply because he was curious to see them in outer space someday. He went on to the Graduate School of Engineering at the University of Tokyo and completed his Ph.D. in Aeronautics and Astronautics in 2004. The same year, he was appointed as a research associate at the Faculty of Engineering Sciences at Kyushu University. From 2007 to 2009, he went abroad as a visiting scholar to the Department of Mechanical Engineering at Colorado State University and has held his current position of full professor at Kyushu University since 2017. He received the 19th Japan Society for Aeronautical and Space Sciences Encouragement Award in 2009 and the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Young Scientists' Prize in 2011. Professor Yamamoto has also garnered significant attention for a joint venture bridging academia and industry, launched in May 2019, to sell miniature EP to universities and private corporations.
Professor Yamamoto looks young for his age, especially when he gets visibly excited about ion engines.
The experimental device that sits in the center of his laboratory are made by technicians from the Department of Energy Science and Engineering (officially the Department of Applied Quantum Physics and Nuclear Engineering) at Kyushu University. Welding and polishing are all done by hand on the order of micrometers, a testament to the high precision equipment Professor Yamamoto requires.
Professor Yamamoto points to an object roughly 30 square centimeters in size. It, too, is a rocket, he says. As rockets become smaller and less expensive, the age of the personal rocket may not be far off.
Professor Yamamoto looks young for his age, especially when he gets visibly excited about ion engines.
Until now, conventional chemical rocket engines on satellites and space probes have used chemical reaction to generate thrust. My interests lie in the research and development of next-generation rocket engines for satellites and probes, namely electric propulsion that use plasma for thrust, which have become known for the prominent role they played in the Japanese Hayabusa mission.
The experimental device that sits in the center of his laboratory are made by technicians from the Department of Energy Science and Engineering (officially the Department of Applied Quantum Physics and Nuclear Engineering) at Kyushu University. Welding and polishing are all done by hand on the order of micrometers, a testament to the high precision equipment Professor Yamamoto requires.
Electric propulsion technology research began in the 1960s and was successfully implemented in the 1970s. As recent as twenty years ago, however, they were deemed too risky for general use and were only used for projects at the national level, used as prototypes or on the occasional military satellite. In just the last ten years, these engines have seen dramatic progress in terms of research and application, and electric propulsion systems can now be found in over 200 satellites and probes worldwide.
Professor Yamamoto points to an object roughly 30 square centimeters in size. It, too, is a rocket, he says. As rockets become smaller and less expensive, the age of the personal rocket may not be far off.
Electric propulsion uses plasma, the fourth fundamental state of matter, which is typically generated by heating a gas to searing temperatures. The heat separates electrons from their atoms and renders them free to move, which creates ions in the process. Plasma can be controlled using electrostatic and electromagnetic force, which means that we can easily transfer energy to ions and electrons. EP uses this electric power to expel very high speed plasma (approximately 20,000 m/s), which results in better fuel consumption. For example, a two-ton satellite currently needs one ton of fuel for orbit transfer, but EPs could deliver the same satellite using just one hundred kilograms of fuel, and less fuel means more room for spacecraft instruments and a reduction in satellite size. As smaller satellites become available, we will be able to share a single launcher, which will have a major impact on cost reduction.
In May 2019, SpaceX successfully launched 60 high-speed broadband satellites equipped with EPs, which were used to adjust, maintain, and raise the satellites’ orbits to 550km, similar to how you would maneuver a drone. These engines are also responsible for the thrust that helps satellites maintain their altitude. Until now, 400 kilometers above the earth was as low as a satellite could maintain its orbit, the inner edge of what is called low earth orbit. With EPs, however, satellites can compensate for atmospheric drag and keep their altitude as low as 200 kilometers above the earth. This makes is more affordable to provide reliable Internet access to remote places in developing nations like those in Africa.
My current research on EPs is geared toward their use on satellites that detect gravitational waves. Using laser measurements and numerical simulations, I investigate the physics behind EP and incorporate any new insights back into engine development. I’m hoping that through countless iterations, I can create even better next-generation engines that will eventually have a positive impact on the world. My mission is to research and develop EPs that meet the current demands of satellites and probes, but as research and innovation speed up across the globe, I am always looking ahead to try to anticipate future needs.
Today, as private corporations and start-ups are launching small rockets and satellites, even universities getting in on the action. I’m drawn to this field because I get to be involved in the most advanced research being done today, standing on the shoulders of giants. It's a big responsibility, but it arouses a curiosity and excitement that outweigh any pressure I might feel.
Research is an endless cycle of failures and triumphs. On average, I probably have two failures for every success. But every failure is an instant opportunity for analysis and feedback that will then lead to an answer. That's one of the attractions of my research. It takes five or six years and dozens of experiments before an engine goes into use, which can be an arduous process, but this research is interesting every step of the way—from taking an idea from zero to one, to testing it, and then going back to the drawing board if it fails. To elaborate, I believe that the joys of a field trip are twofold. The first is the sleepless anticipation the night before as you imagine the next day’s trip. The other is the enjoyment of the field trip itself, where you get to enjoy seeing new things and sharing them with your friends. Research is a lot like a field trip in this regard—with feelings of anticipation before an experiment and the surprise and shared excitement you feel during and after it, only to repeat in an endless cycle. [laughs] That excitement is what keeps me going day after day and is a real joy of manufacturing, be it engines or otherwise.
For me, the strength of the bonds between people is what makes Kyushu University so special. This is especially true with Chikushi Campus, where many advanced research institutes call home. Talking with other professors and students here, even in fields that seem unrelated to my own, I have new realizations and find ways to relate them to my future research. Kyushu University is also focused on training the next generation of leaders through initiatives like its Campus Asia program, which is operated in close partnership with Shanghai Jiao Tong University in China and Pusan National University in South Korea. These types of programs are important because they encourage communication with people from different backgrounds, which can help us see who we are and what we study. It is also useful to come up with new and creative ideas. Chikushi Campus is focused solely on the sciences, so I would like to see more opportunities for cross-campus interaction with humanities students.
Professor Yamamoto uses this to fine-tune the optics and machines used in his experiments. The brand name on the sizes he uses most has slowly worn away over the years.
A large backpack that Professor Yamamoto uses for everything from commuting and business trips to walk with his daughter. This bag has unrivaled functionality: it’s waterproof and has a laptop compartment plus back-side vents that keep things cool even in the summer. But after three years of constant use, Professor Yamamoto says that it might be time to think about getting a new one.
Professor Yamamoto’s notebooks are used for jotting down notes and ideas. He prefers unruled notebooks because they can accommodate his drawings and diagrams. His calculator is for the occasional computation, and his marker is mainly for playing with while he is thinking. This cute, flower marker is from Malaysia, left to Professor Yamamoto by his father-in-law. He says that he’ll spin it around on his desk while he is deep in thought.
Every person has their own best — so you best do yours.
When you get to university or graduate school, you step into a completely different world from the one you knew in high school. You meet all kinds of new people and it can all be very stimulating. University life is full of potential, full of possibilities for you to pursue your curiosity and imagination. But I feel like many students at this age think that they don’t have anything that makes them stand out—that they’re just another ‘ordinary’ person. But “ordinary” people do not exist. I also get the impression that many students just go with the flow, doing the same thing as those around them. That is to say, everyone has their own unique personality. University is a time when you can learn about yourself, meet all kinds of people, and have free rein over how you spend your time. While you’re in school, I suggest you find out what makes you. And once you figure out what it is, I want you to nurture it as best you can. Because everyone has their own way of doing things. There’s nothing more rewarding than believing in yourself, going at your own pace, and carving out your own path.
This interview was conducted in July 2019.
