This invention is used as fuel tank sealant. It is composed of a polyimide. This sealant exhibits excellent thermal, oxidative and hydrolytic stability; high tensile strength and elongation during extreme temperature exposures; improved fuel resistance; and lowered glass transition temperature. This invention is used as a fuel tank sealant. It is composed of tetracarboxylic acid and dianhydride. This sealant exhibits excellent thermal, oxidative, and hydrolytic stability; high tensile strength and elongation during extreme temperature exposures; improved fuel resistance; and lowered glass transition temperature. A PANEL FOR SELECTIVELY ABSORBING SOLAR THERMAL ENERGY AND THE METHOD OF PRODUCING SAID PANEL NASA Case No. MFS-22562 Australia, Canada, France, Address inquiries to: Marshall Space Flight Center Attn: Patent Counsel Huntsville, AL 35812 [Corresponding U.S. Patent-Application Pending] Metal bodies having requisite absorptance to emittance ratios can be fabricated so that the heat absorbed is transferred to tubes carried in the metal body for subsequent use in heating and cooling operations. This invention is a panel for selectively absorbing solar thermal energy comprising a metallic substrate, and a solar thermal energy absorbing coating carried on the bright metallic material. A layer of zinc is interposed between the metal substrate and the layer of bright material or the metallic substrate can be anodized for receiving the layer of bright metallic material. Also disclosed is the method for producing the coating which selectively absorbs solar thermal energy. 4 2 3 2 SOLAR ENERGY ALUMINUM OXIDE ALUMINUM The invention consists of two spheres, one sphere having the capability of resting on top of the other sphere without falling off, even when either of the spheres is jiggled. The spheres are not fastened together in any way. The center of gravity of the top sphere is displaced from its geometrical center by a certain distance. The top sphere can rest on the bottom sphere with its center of gravity on the vertical line segment joining the geometrical centers of the spheres. Also, the top sphere can rest on the bottom sphere such that the line joining the centers of the two spheres is inclined to the vertical. In both positions, the top sphere can be rolled up and down on the surface of the bottom sphere to a predetermined maximum angle and, when released, will return to its original position atop the bottom sphere. |