Space development programs especially requires tighter international cooperation for its success because of special nature of space equipment manufacturing industry. To make clear this view point, authors introduce a concept of “Industrialization Threshold Level” defined by conjunction of unit price, Technology level, and investment with sales amount. It classifies the industry into matured industries and gevernment-supported industries. Plots of each country on the square of population and the square root of country dimensions show another aspect of the space industry. These two analysis emphasize the need of international cooperation on Space Programs.

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A concept of space nuclear power system is proposed. Safety at the launching is solved by launching separately the reactor without fuel and the fuel cartridge. As an example of such separable system, a coated fuel particle bed reactor is studied. Total power generating system, consisting of nuclear reactor, thermoelectric converter, heat radiator and heat transport system, is described. The applicability of advanced technology of alkali metal thermoelectric converter and liquid droplet radiator is also studied.

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We have studied electrostatic charging and discharging characteristics of dielectric materials for spacecraft, irradiating electron beam. Surface materials such as Teflon and Kapton negatively charge up and reach high surface potentials. Under the simulated irradiation condition of the geomagnetic substorm, discharges occur on the surface and/or through the bulk of the materials. The surface charging phenomenon is also observed by a potential monitor installed on Engineering Test Satellite V of Japan in space environment. These experimental results suggest us the necessity to suppress surface charging. We have studied two suppression methods. One method is to coat a conductive layer on the insulating film. The other is to cancel out the surface charging by ejecting Xe plasma from the neutralizer of an ion engine. We confirmed that these two methods are effective for eliminating the surface charging on the spacecraft which is considered to be encountered in space.

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As a sub-program for the Venus spacecraft exploration project planning in Japan (the PLANET-B mission), ballooning from an orbiter to the deep atmosphere of Venus has been proposed. The principal objective of this sub-program is focused on elucidation of the origin of a super-rotation (the four-day circulation) of the Venusian atmosphere. An instrumented, metal-skinned, water-vapor-filled and super-pressurized balloon of diameter ≈ 1 m and weight ≈ 10 kg is feasible for Lagrangian wind and temperature observations at the (angular) momentum maximum altitude (≈ 20 km).

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