2021 年 19 巻 1 号 p. 116-122
Functionally graded ablative materials with density gradient were newly developed for the thermal protection system of future space exploration missions. The ablating surface was densified to reduce the amount of surface recession, while the density inside the ablator was reduced with expectation of weight reduction and high heat insulation. Typical Bulk specific gravity was found to be about 0.8. Basic thermal characteristics of the developed ablative material were obtained by conducting heating tests. The heating tests were carried out in the arcjet wind tunnel facility in the Chofu Aerospace Center in JAXA for heat flux of 0.9~4.5 MW/m2 and impact pressure of 8.6~31 kPa, and in the Sagamihara campus in JAXA for heat flux of 3.6~14.3 MW/m2 and impact pressure of 12~54.3 kPa. The amount of surface recession of ablator was successfully obtained during the heating tests. According to X-ray CT inspection conducted after the heating tests, delamination between layers was not observed inside the test piece. In addition, the present study showed the developed ablative material has a potential to reduce the TPS weight by 33.3 % compared with the Hayabusa ablator, although the recession rate of the present ablator is almost same level as the Hayabusa ablator. From a different point of view, the developed ablative material showed a potential to reduce the recession rate in a relatively wide heating environment compared with a medium density ablator, which has the same specific gravity.
