堀 恵一

The third Epsilon launch vehicle, which was the Enhanced Epsilon launch vehicle optional configuration, was successfully launched with the payload of ASNARO-2 in January 2018. The post flight analysis was conducted. The chamber pressure and thrust include residual thrust of three main motors and chamber pressure of SMSJ and SPM were analysed to confirm the effectiveness of design and production methodologies. All solid propulsion systems for the third Epsilon launch vehicle showed a very good behaviour during the flight.

Since 2000, Japan Aerospace Exploration Agency (JAXA) is involved in the research and development (R&D) of hydroxYlammonium nitrate (HAN)-based liquid monopropellant, SHP163 which is composed of HAN, ammonium nitrate (AN), methanol and water for its possible utilization as an alternative of hydrazine toxic component. The freezing point of SHP163 is much lower, the density and the density-Isp are higher than those of hydrazine. The toxicity of SHP163 is also lower than hydrazine, therefore easy handling. Moreover, SHP163 monopropellant showed stable burning rate measured by strand burner and its thermal decomposition of HAN-based occurred in two steps. However, the catalytic process showed a violent exothermic reaction of HAN-based in one step at low temperature onset around 65 C. The application of SHP163 on thruster firing tests showed that pressure slopes have been increased in the case of honeycomb catalysts and burning reactions have been improved by new synthesized Ir-CuO honeycomb catalyst. The obtained results on thruster 20 N type demonstrate that SHP163 is a good candidate as green propellant and proved the reason why it has been selected to be used as hydrazine alternative monopropellant for "Innovative Satellite Technology" project launched in 2016 by JAXA, Japan. (C) 2016 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

The development of Enhanced Epsilon is mainly the renewal of the second stage, and also includes each subsystem's improvement. The second-stage motor M-35 was newly designed and manufactured. In order to verify the design, the static firing test of the M-35 under the condition of vacuum ambient was conducted in 2015. The Epsilon's second flight, which was the first Enhanced Epsilon launch vehicle, was successfully conducted with the payload of Exploration of energization and Radiation in Geo-space (ERG) in Dec., 2016. After the flight, chamber pressure and thrust include residual thrust were analysed to confirm the effectiveness of design and production methodologies. All solid propulsion systems for the Enhanced Epsilon launch vehicle showed a very good behaviour during the flight.