The activity in our laboratory mainly consists of the following four pillars.
Research (research on flexible mutibody dynamics and large space structure)
Space demonstration of research by using nano-satellites
Domestic and international collaboration for realization of cutting-edge space system in near future
We emphasized human resource development and outreach of space engineering science on the basis of nano-satellite development in the past (Please refer the web page on past activities).
Recently, the space activities get lots of visibility and there have been getting icreased more and more players of space activities such as venture companies of space business and university laboratories developing nano-satelliets.
Under such circumstances, we think cutting-edge research and its social implementation for our society to move on to the next stage, and to produce young people (students) who play a key role of such social improvement/innovation.
Therefore, our laboratory has changed our policy to aim for such cutting-edge research;
Our research interest involves multi-body dynamics of rigid bodies combined with large gossamer structures consisting of membranes and cables. We call such dynamics Gossamer Multi-body Dynamics, GMD. Deployable space structure is one of the best application of GMD, so that we participate in the solar power sail project by JAXA and other research and development on space structure, especially deployable space structure.
We have been researching on nano-satellite and developed nano-satellites since 2001. This is also a part of the research on GMD. We started the development of a CubeSat because we want to verify our research of GMD in space. We launched CubeSat "SEEDS" to get the skill of developing satellite bus system, and SPROUT for space demonstration of our research on a gossamer structure, named combined membrane structure. Unfortunately, the demonstration failed, so we estimated the reason. Based on its knowledge, we started the research on a new gossamer structure concept, i.e. self-deployable membrane truss structure. We aim for the space demonstration of the self-deployable membrane truss structure now.
The best part of gossamaer structure is being suitable for large space structure. The bottleneck for constructing large structure in space is the launch vehicle. The payload capacity of the rocket is limited in weight and size, and the launch cost is still quite expencive. Therefore, it is the most likely candidate for the method to construct a structure larger than 100m in space to deploy gossamer structures followed by connetcing them with each other on orbit because the gossamer structures are quite lightweight and easy to stow and deploy. That is the reason why we have been researching the feasibility of large space structures consisting of gossamer structure.
Of course the construction of large structure in space does not bean anything by itself. The most important is "what the structure is used for after it is constructed". Our research target is the large space structures applicable for solar sail for exploring the solar system, star shade for observing exoplanets, solar reflector, space solar power system, and so on.
The objective of developing the nano-satellite SPROUT was the space demonstration of the research on combined membrane structure which is a kind of gossamer structure. We think a small, user-friendly (easy to customize), and high-performance camera system for nano/pico satellite and a high-speed transmitter for downlink of the image data are necessary for the space demonstration of such deployable structures. So, we are in progress to develop a CubeSat "NEXUS" for the space demonstration of such components.
We think it is the shortest way for realizing large space structure to demonstrate the concept of the structure in space by using nano-satellites. However, we must be careful for easy demonstration of research findings by using nano-satellites because we must take care of the space debris issue that has been getting great attention in recent bulk launch of CubeSats. The nano-satellites in low earth orbit (higher than 650km) should have any "de-orbit" device that enables the satellite not to stay in the orbit for long time after the end of the mission.
"De-orbit" means that the satellite with mission completed burns out by re-entrying into the atomosphere. There are several methods to have the satellite de-orbit. Among them, we focus on the de-orbit device that deploys a thin large membrane on orbit to increase the atomospheric drag so that the satellite decreases its altitude. Such a device is available for nano-satellites orbiting under 700km altitude where there exists (rarefied) atmosphere. We apply our research on gossamer structure to an affordable lightweight de-orbit device with high storability and for CubeSat that employs self-deployment structure (left figure). We hope we can transfer such technology to any company to put it into practical use.
Thus the deployable membrane structure, one of gossamer structure, has the capability of de-orbit device, so that its space demonstration helps the prevention of th eincrease of space debris. We have been studying on the space demonstration of the deployable membrane structure that is stored around the interface cylinder between a nano-satellite less than 100kg and the launch vehicle, and considering to make such space demonstration be recognized as a standard mission (right figure).
Our final goal is to realize cutting-Edge Space Systems, CESS (not only structure, but whole system) that is guaranteed by academic research. We need collaboration with academia, engineers, and industries in our country and other countries.
We have already participated in Research group on Advanced Lightweight Structure Systems(ALSS) and research and development project of ISAS/JAXA to enhance the collaboration with other researchers. We also participated in ORIGAMI project (FY2014-FY2016) that aims to "demonstrate our research on space engineering in real space instead of limitting the research on the ground", to organize the core of research and development of advanced deployable structure in Japan.
We have been discussing with domestic and foreign companies of deployable structures, too.
Now, we will establish a research group "Cutting-Edge Space Systems (CESS)" that aims to "master" the technology required for future spacecraft structure that is represented by the keywords "deploy", "store", "measure", "move (drive)", "rest (immobilize, suppress)", "connect (fix)", "sseparate", "heat", "refrigerate&, and so on, which leads our research advanced and deepened.
Our laboratory holds the seminars who are not satisfied with the class in our department. Any students in our department can join each seminar. We hold the following seminars in FY2016:
Gossamer Multi-body Dynamics (GMD)
Nonlinear finite element dynamic analysis of membrane structure
Application of linear algebra to engineering
Combined membrane structure
We will continue the seminars on GMD and membrane structure in FY2017, and is consiering new seminars upon request from students. In addition, we hope we can hold more practical seminar in which the students can fabricate conceptual models of deployable structure by using 3D printors, laser cutting machines, 3D protopying machines, and other machines, conduct the experiments, investigate the deployable structure through the experiment, and design a nano-satellite to demonstrate the deployable structure in space.