Specific rigidity, specific strength, low heat expansion, thermal conductivity, moisture absorption...
We can't talk about space development without mentioning carbon fiber composite materials.

Launch a rocket or shuttle carrying a satellite, etc., into space requires an enormous amount of energy and money, and there is a need to reduce the weight, even by 1 g. In addition, rockets and shuttles are exposed to strong cosmic rays/UV rays in high vacuum, and must use materials having excellent dimensional stability in an environment subject to extremely large temperature shifts. Carbon fiber composite materials offering excellent specific strength/specific modulus of elasticity and allowing for weight reduction through anisotropy-based optimal design, are most suited for this weight reduction, and since their coefficient of thermal expansion is approx. one-tenth that of metals, carbon fiber composite materials are extremely stable dimensionally under temperature shifts; in all aspects, they are best material for space applications.
Currently CFRP is used for the top satellite-carrying section, spaces in between, fixed rocket booster case, etc., of the rocket as well as for many parts of artificial satellites such as hull frame, solar cell paddle, antenna support and arm. Space shuttles also use carbon fiber composite materials offering excellent heat resistance, for the black panels at the bottom in order to withstand the high heat they receive when entering the earth's atmosphere again.

Some areas require super-high elastic yarns with a modulus of elasticity of over 70 tf/mm2 in space, and pitch carbon fiber is used in these areas; however, PAN carbon fiber must be used in areas requiring compressive strength and tensile strength, and PAN fiber contributes to the size increase of artificial satellites, rockets, etc. As more communication satellites, etc., are scheduled to be launched, spacecraft is expected to grow as an important market for PAN carbon fiber.