As member of the ISS international partnership program, Japan makes essential contributions to space experiments and enables human space activities through the use of HTVs. JAXA has initiated technical research into cargo return from orbit as a next step toward on-orbit services. The HTV has been used in research as a service module, and a return vehicle called HRV (HTV Return Vehicle) was added to enhance its performance. The combined vehicle is called HTV-R and it will enable JAXA to recover various samples from experiments conducted on the ISS.

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HTV-R aims to return payloads from the ISS to the Earth in the near future mission. This system contains new technologies for reentry, especially a thermal protection system with low-density ablator. This paper describes technical issues and basic research of the thermal protection system for HTV-R to realize Japanese return missions from the ISS.

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For the design of a manned or cargo space capsule, it is important to precisely estimate the Earth landing loads to the crew or cargo, and to limit the loads to within a permissible range. Water landing simulations and scale-model water landing tests with varying conditions for descending velocity, pitch angle, and horizontal velocity during splashdown were conducted to estimate the magnitude of water impact on the recovery space capsule. This paper describes the results of the simulation and water landing tests.

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Previously-realized Japanese capsule spacecraft, OREX (Orbital Re-entry EXperiment), USERS capsule, and HAYABUSA reentry capsule, were all ballistic reentry capsules, which flew without any guidance during reentry and had large splashdown areas. To establish practical recovery systems from the International Space Station (ISS), JAXA has been studying reentry capsules using guided reentry flight, which enable capsules to narrow their splashdown area within 5 km and reduce aerodynamic acceleration less than 4 G. To improve reentry guidance accuracy, we use accurate real-time prediction guidance using numerical integration for reentry spacecraft and IMU-GPS-ST integration navigation. This paper describes the characteristics of guided reentry flight and technical challenges on guided reentry flight for capsule spacecraft and presents guidance and control methods of guided reentry flight for the technical challenges.

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A series of aerodynamic tests have been conducted for the preliminary design of large scale recovery capsule HTV-R . Wind tunnel tests from low to hypersonic speeds and numerical analysis were conducted to establish the HRV aerodynamic database for the HTV-R’s design. Experiments to improve testing and estimation capability of transonic dynamic stability characteristics, parachute characteristics at low speeds, and hypersonic RCS jet interaction were conducted for the development of the HTV-R program. This paper provides a summary of the objectives and scope of the aerodynamic tests.

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A series of free-flight test campaigns with HTV-R re-entry capsules were conducted in JAXA Kakuda Space Center. These tests were conducted in the air driven two-stage light gas gun HEK-G with newly built 120 mm-diameter gun barrel, which can launch up to 110 mm diameter projectiles. The main purpose of this test was to obtain benchmarks for transonic instability of the HTV-R reentry capsule to compare with wind tunnel results or CFD calculations. Aerodynamic characteristics measurement of the projectiles was conducted with a miniature data-recorder and piezoelectric accelerometers on-board the projectiles. The JAXA in-housed miniature data recorder specially designed for the present test was small enough to be instrumented in free-flying projectiles with a maximum high-G resistance of 1000 G. The specifications of the recorders were (1) sampling rate of 100 kHz, (2) piezoelectric sensors (or piezoresistive sensors) with 8-channels, (3) sensitivity of 16 bit, and (4) recording duration of 1300 ms. The size of the recorder was 58 mm diameter x 50 mm height including batteries. A high-speed video camera was also used to observe the attitude of capsule shaped projectiles during free-flight. The projectiles were launched into open air at a flying speed of approximately 200 m/s, and captured on the soft-landing recovery cushion after a 30 m free-flight. All the projectiles used in this test campaign were recovered without any serious damage to the onboard instruments. Acceleration histories of pitching motion were successfully recorded with the onboard data-logger and high-speed video images that showed instable movement of projectiles.

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A preliminary study for developing a manned space crew vehicle was conducted by JAXA. A capsule type space crew vehicle was well-defined through multiple design cycles, and showed clear development feasibility. JAXA will continue research on key technologies for manned transportation including a lightweight heat shield, precise control algorithm, low toxic thruster, launch abort system, and high efficiency heat rejection system.

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This paper describes research activities on human spaceship control and safety by crew intervention. A human spaceship must be capable of supporting human intervention at various levels so that crew members can perform their required duties. Design feasibility and control solutions are currently being investigated for this purpose. Dynamic simulators with human spaceship mission scenarios were developed, and methodologies and technologies were evaluated by experienced astronauts.

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