Quasi-steady non-charring ablation in a semi-infinite solid with linearly temperature-dependent thermal properties is solved by two kinds of perturbation methods, where the surface temperature and recession rate are constants. One is the conventional perturbation method (CPM) and the other is the modified perturbation method (MPM), where the perturbation parameters are α (thermal conductivity parameter) and γ (specific heat parameter). The solutions by the CPM, MPM, and the finite difference method (FDM) are compared. The effects of α and γ upon the dimensionless temperature are investigated. It is found that the MPM solution is more accurate than the CPM solution and the MPM extends the applicable range of the perturbation parameters, α and γ, compared with the CPM. The solutions by three kinds of calculation methods (FDM, CPM and MPM) are compared with the measured results. Application of these solutions to Teflon material is discussed.

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A lightweight membrane has the potential to be a useful platform for a variety of on-orbit uses. Boom-supported multifunctional membranes have recently attracted attention because they can be attached to a satellite body and have solar arrays or antennas mounted on their surface. Although reliable deployment is crucial for their successful operation, the potential for interference between the boom and the membrane presents a significant risk. Thus, this paper provides a framework for performing a safety analysis of the membrane deployment. We define a potentially dangerous region where interference from membranes and booms may occur and evaluate the level of deployment safety by employing a multi-particle approach to simulate membrane deployment. This study focuses on the boom-supported membrane component of the HELIOS (Harvesting Energy with Lightweight Integrated Origami Structure) mission, and investigate strategies to mitigate the risks related to membrane and boom interference. The results show that for safe and reliable membrane deployment, the deployment speed and bending forces of the membrane must be considered.

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Hayabusa2 deployed an artificial marker called Target Marker to conduct an autonomous touchdown on an asteroid. Due to the microgravity environment of an asteroid, the rebound of the payload tends to become large, resulting in difficulty in settling it in the desired area. To solve this problem, a TM is composed of a shell and a lot of inner balls, which dissipate the TM's energy by colliding with each other. Also, the TM has spikes attached to the shell to prevent horizontal motion on an asteroid's surface. Although past studies showed the effect of rebound mitigation, the effects of mass ratio and spike length, which are essential for designing a new TM, are not known. Therefore, this study investigates those aspects and proposes threshold mass ratio and spike length that can be used as design criteria. The results of this study can be used for the design of artificial payloads for future asteroid missions.

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A numerical analysis method is presented for evaluating the resistivity of in-flight shaped charge jets from magnetic flux signals obtained with a magnetic flux loop, which is installed coaxially with a ring-shaped permanent magnet in the same plane. The amplitude and the ratio of the positive and negative peaks of the loop voltage are used as calibration parameters. By fitting these to numerically estimated calibration curves computed from the jet shape and velocity measured using other techniques, the jet resistivity can be uniquely derived. The resistivity derived by applying this method to a signal obtained from an experiment with a Cu jet was ρ ∼ 1.39 × 10^-7 Ωm and suggested that the jet temperature was around the melting point of the Cu liner (1358 K). This temperature was confirmed by a smoothed-particle-hydrodynamics simulation that reproduced the jet shape and velocity. Since the jet shape is required to generate calibration curves, imaging measurements are essential to the present analysis.

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After experiencing a series of mission failures from the late 1990s to the early 2000s, the Japan Aerospace Exploration Agency (JAXA) implemented a reform strengthening and promoting systems engineering and project management (SE/PM) in 2005. Since then, the occurrence rate of mission failures decreased significantly. After a while, following the in-orbit failure of Japan’s flagship X-ray observatory occurred in 2016, another reform on PM was implemented in 2017 to ensure development and create value. Six years after that, in 2023, the new issues related to development risks became apparent. In parallel, a Japanese flagship asteroid sample return spacecraft “Hayabusa2” was developed in an extremely short period of 3.5 years and launched in December 2014. Overcoming the unexpected rough terrain of its target asteroid 162173 Ryugu, the spacecraft successfully sampled the asteroid’s surface/underground soil in 2019 and accomplished its entire mission by returning its reentry capsule safely to Earth in December 2020. This paper aims to detail the issues in current JAXA projects and identify clues to solve them by reviewing JAXA’s past two reforms in SE/PM and best practices of Hayabusa2, a representative successful project in recent years that both achieved sure development and creating values.

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