Overview of H-II Transfer Vehicle (HTV) and HTV-X safety design considering common-cause software failure

Abstract

The Japan Aerospace Exploration Agency (JAXA) is now developing the HTV-X, the successor to the H-II Transfer Vehicle (HTV). The HTV, also known as the Kounotori, was an unmanned cargo vehicle that transferred supplies to the International Space Station (ISS) with the largest spacefaring cargo capacity in the world. The HTV-X has improved transport capability and operability based on the expertise and technologies gained through the R and D and mission operation of earlier HTVs.During HTV-X development, JAXA encountered several challenges regarding ISS safety, but JAXA overcame them and enhanced the safety design. One example of the design enhancement is the countermeasure against Common-Cause Software Failure (CCSF).Hence this paper presents an overview of the HTV and HTV-X safety design, the trend of the discussion on the safety panels of the HTV through the HTV-X, and the feedback from the technical coordination incorporated into ongoing HTV-X safety design, taking countermeasure to manage CCSFs for example.