Yasuhiro Morita

© 2020, Univelt Inc. All rights reserved. ISAS/JAXA has successfully launched the micro-satellite “TRICOM-1R” by the world’s smallest orbit rocket “SS-520 No.5” from Uchinoura Space Center on February 3rd in 2018. ISAS modified the existing sounding rocket SS-520 adding a small 3rd-stage solid-motor and the attitude control system. It flies spinning for the attitude stabilization in the flight. Therefore, we devised the rhumb-line control system with a new scheme. This rhumb-line system has the high-performance functions; the high-preciseness, the high-maneuver rate and the suppression of the unnecessary nutation angle generated at the RCS injection. This paper reports the development of the G&C system and the flight results.

The first Epsilon rocket was launched successfully with a small payload 'HISAKI' on September 14th, 2013 in Japan. Epsilon has a new absorber structure in Payload Attach Fitting to reduce the vibration condition for payload. We designed the robust control logic to satisfy the compatibility of robust stability and response against various disturbances. The 3rd Stage under spinning has a Rhumb-line Control function which reduces the pointing error at separation and ignition of solid motor. We could insert the payload into the orbit precisely by 'LVIC' guidance, suitable for low thrust propulsion in Post Boost Stage. We will present the flight results of the Guidance & Control (G&C) system and dynamics of Epsilon rocket.

The Epsilon launch vehicle, the newest version of Japan's solid propulsion rocket, has successfully had its maiden flight in this September carrying the extreme ultra-violet planetary telescope satellite SPRINT- A. It should be emphasized that the JAXA appreciates the advantages of combined power of the standardized small satellites and the Epsilon's highly efficient launch system, both developed by JAXA, to increase the level of space activities. Although the launch site of the Epsilon rocket, the Uchinoura Space Center (USC), was originally considered a highly compact launch complex, some modifications were made to become more efficient. The efficient launch vehicle and the compact USC established one of the most powerful tools that contribute to small missions (tentatively, maximum 1.2 ton into LEO and 450kg into SSO, as of the first flight). The purpose of the Epsilon rocket is to provide small satellites with a responsive launching, which means in this study we focus on a low cost, user friendly and ultimately efficient launch system. To realize this, the design concept of the Epsilon involves various innovative next generation technologies such as the highly intelligent autonomous checkout system and the mobile launch control. Owing to these endeavors, it was proved that the lift-off can be executed in less than 6 days after the first stage motor stand-on although the first flight took longer for extra tests and operations to complete the entire development. Another aspect that small satellites will most welcome is more user-friendly character involving: A reduction in the acoustic vibration level by refined ground facilities an attenuation of the sinusoidal vibration environment by a special vibration attenuator and a highly accurate orbit injection by a liquid propelled upper stage. Their effectiveness was well demonstrated. Now that the first flight was finished, the most important is what the next step will be in the future. JAXA has been conducting intensive researches on a next generation Epsilon to launch a more powerful and lower cost version Epsilon (El) in 2017 (TBD). In order to minimize the level of technical risks, JAXA plans to take a step by step approach to improve the cost and performance of the launch system toward El. According to this strategy, the second flight will be conducted in 2015 with an enhanced launch capacity of more than 500kg into SSO. This paper provides the results of the first flight of the Epsilon and reveals its evolution plan. Copyright© (2013) by the International Astronautical Federation.