this uncertainty must be eliminated, i.e., a detailed study of the transient thermal performance of the structure must be performed. 4.3.2.1 Background Twice each year the MPTS will be shadowed from the Sun by the Earth. While in the Earth’s shadow there will be no waste heat. The only source of heat to the MPTS will be 5-6 w/m2 from the Earth’s infrared emission and albedo. The structure will drop to approximately 75° K (-335° F) during the 72 minute occult period. Stresses will be induced as a result of components with low thermal inertia cooling and shrinking more rapidly than the "heavier" ones. The counterpart of this problem with the MPTS coming out of the shade and into the sunlight will also have to be investigated since the members will be stressed differently in the two situations. Identification and modelling of the critical support structure elements will be required. A thermal model of the antenna waveguide/ radiator surface will be necessary to provide the thermal inputs to the structure as the entire MPTS moves in and out of the Earth's shadow. 4.3.2.2 Desired Output • Transient temperature responses of critical structural members during cool-down and heat-up as the MPTS goes in and out of Earth’s shadow • The stresses induced in the structural members as a result of differential contractions/expansions caused by the different temperature responses. 4.4 ASSEMBLY 4.4.1 Assembly Cost The greatest uncertainty in establishing accurate cost estimates for the MPTS is the estimate of assembly cost. In the development of assembly cost estimates, the amount of resources (manpower, facilities and materials) required to produce the end product must be known. Manpower costs are of two types: recurring and non-recurring. Recurring is the effort associated with the fabrication, assembly, integration and test of flight hardware. Non-recurring cost is the effort associated with manufacturing and testing prototype or test hardware. This effort also includes the cost of tooling and peculiar support equipment. 4.4.1.1 Background Three basic methods of developing manufacturing cost estimates are used: grass roots, analogous and parametric. Grass roots estimates are based on building up from detailed estimates and require good definition of the parts to be fabricated, the methods
RkJQdWJsaXNoZXIy MTU5NjU0Mg==