JETRO Global Connection -Accelerate Innovation with Japan-

Creating Sustainable Engines for Spacecraft

December 6, 2022

Our next interview features Toku Sakai, the COO of Pale Blue, a Japanese aerospace company that develops next-generation spacecraft engines. He was born in the US and has worked at the Department of Defense. Afterwards, he worked as a consultant in the space sector and then joined Pale Blue.

Toku Sakai,COO of Pale Blue (Photographed by JETRO)

What kind of products does Pale Blue produce?

Pale BlueExternal site: a new window will open. is a Japanese company that was founded in 2020. We develop next-generation spacecraft engines. The engine is inside a satellite or spacecraft that goes into space, and you need it to stay in orbit. Our innovation is that our engines work entirely on regular water, making them incredibly affordable, easy to handle and reusable.

How does the technology work?

Historically, when companies have tried to develop water-based engines, they will take water heated up and turn it into steam. We found a way to turn that steam into plasma using minimal power. Once you create plasma, you can charge the ions into the plus and minus ions. Then you can accelerate those ions at incredibly fast levels, up to 300,000 miles per hour. That acceleration gives you much more fuel-efficient thrust.

Hybrid type thruster (provided by Pale Blue)

What's the main problem you're trying to solve compared to existing solutions?

It's how sustainably we can use space. When we send something up into space, you go with one fuel tank. That is all the fuel you get for the entire duration of whatever it is you want to do. When satellites go into space, they might be designed for five years. But the biggest problem is, once they run out of fuel, satellites come back down to earth, or they're pushed out into graveyard orbit, where they are never used again.

A lot of the components on satellites, like the camera sensors and batteries, can be used for years longer, but we throw it all away because we run out of fuel. Today, the most commonly used fuel is highly dangerous and explosive. Hydrazine is quite toxic, and another common one is a gas called xenon, that's very pressurized. Both of these are very difficult to refuel in space.

Our vision is to reuse all kinds of infrastructure that goes into space. Since we have developed an engine that runs on water, you don't have to worry about high pressurization. If you can refuel it, you can bring down the cost of driving and operating in space by multiple folds. One thing that's exciting for us is the idea of mining resources in space. Water is quite abundant on asteroids or the moon. Companies are working on extracting that water in space to refuel and run independently of the earth's resources.

The propulsion by Pale Blue thruster (provided by Pale Blue)

Is there anything special about the water that's used in this technology?

Our philosophy is not to use any special water, so we use water which is distilled. It's available online, and you can buy it on Amazon. Laboratories and research labs around the world buy this at less than $1 per kilogram. It's treated in a standard way that's uniform across the globe.

What challenges have you faced as a startup?

We run into the same issues that a regular startup faces in fundraising and recruiting. One unique thing is because we work in the space sector, the business timeline for a space startup is much longer than the timeline of a few months for a software company. Because we develop the actual hardware, developing an engine can take as long as 12 months. Right now, many of the engines are bespoke or customized.

The other thing is our customers want to know if our engines work in space, so they will ask if we have space data, like space heritage or flight heritage. They look at whether there is a long history of performing in space. There can be considerable time before you get that first set of data for customers. Even after you build the engine, which can take 6 to 12 months, we have to put it on a rocket, which can take another 6 to 12 months. So the iteration process for space hardware is longer, which can impose unique financial challenges.

Pale Blue laboratory, researchers simulate how their engine works in space-like environment (provided by Pale Blue)

How do you see the Japanese space industry?

Japan is an interesting case. In a lot of ways, it has a lot of unique advantages. Japan is typically quite strong on technology, especially robotics and very small kinds of technology, where you're trying to miniaturize existing technology. There are a lot of research laboratories and a lot of institutions in this area.

The government has recognized many of these technological hubs and is now trying to commercialize them. We're an excellent example of that. Our founders* are all propulsion engineers who have researched at the University of Tokyo. They found out that there was a strong demand for the technology, so we launched Pale Blue in 2020. A lot of the funding that we got from the government side allows us to continue our work now.

*Founders of Pale Blue: Jun Asakawa, Ph.D., Kazuya Yaginuma, Ph.D., Yuichi Nakagawa, Ph.D., and Hiroyuki Koizumi Ph.D.

Interview image (photographed by JETRO)

How can the Japanese government support the growth of startups in the space industry?

The Japan Aerospace Exploration Agency (JAXA) is well-known in the space community and works extensively with NASA, ESA and international space agencies. It's held in high regard globally. Using JAXA's recognition has been a way of building up trust among global customers.

What feedback have you received from customers?

Engineers are dealing with many different factors. The last thing they want to do is work on something dangerous or difficult to use. They love anything that runs on water because you don't need to apply for any special licenses or put on any special equipment, which you need for today's commonly used fuel sources. They love the idea of how easy and how affordable it is. We're selling engines to customers even before we present that data because the ground test data was quite robust, and the performance levels are really good.

Profile of Toku Sakai
Toku Sakai works at Pale Blue as Chief Operating Officer (COO). Toku is currently based in Japan but born and educated in the US. He used to work as a consultant in the US for government-driven markets as well as space industry and joined Pale Blue since 2021. He won the Japan challenge pitch contest sponsored by Hello Tomorrow as a speaker of Pale Blue in 2022.

Report by:
KAGA Yusuke, Innovation Promotion Division, JETRO

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