Smaaatav task - statement of work (SOW) task title: design and manufacture of structurally efficient composite struts 1.0 background: NASA evaluates the structural efficiency of concepts for…

Smaaatav task - statement of work (SOW) task title: design and manufacture of structurally efficient composite struts 1.0 background: NASA evaluates the structural efficiency of concepts for aircraft and spacecraft components with the goal of designing lightweight parts. The use of composites such as graphite-epoxy in place of metallic structure creates the potential for weight savings in many constellation vehicles. One candidate for this weight savings is the altair lunar-lander. The current altair lunar-lander point-of-departure design consists of a truss-based descent module composed of a large number of truss members. The lander truss serves as the support structure for the massive liquid oxygen and liquid hydrogen propellant tanks, and for up to eighteen metric tons of payload mass. The current lunar lander is significantly larger and more massive than the lunar excursion module (LEM) of the apollo program, and hence presents significantly new and different design challenges. Because of the extreme need to reduce mass, IT is essential that the lander truss elements be designed to operate at peak efficiency. Because the lander struts are highly loaded in compression during launch, there are a variety of critical design parameters affecting the optimum design. Analytical trade studies are typically performed to determine an optimum design, but manufacturing considerations must be included to make optimal design practical for real-world applications. The work described here addresses analysis and manufacturing. For purposes of this study, the altair mission is divided into two phases (1) fabrication through launch to low earth orbit (LEO) and (2) loiter in LEO through trans-lunar insertion (TLI) and then landing on the lunar surface. This division is a simplification of the mission profile to separate the times of high mechanical loading from the times of high thermal loading since requiring the structure to withstand both simultaneously may over-constrain the design, leading to a larger mass than is needed. The most severe mechanical loading occurs in the first few minutes of flight until the vehicle reaches LEO. The thermal loading environment during that time should be considered the same as the range for the unprotected structure on the launch pad for purposes of this study. However, the current mission for altair assumes a loiter in LEO which could subject the lander to temperature extremes and micrometeoroid and orbital debris (MMOD) but no significant mechanical loads. The phases of the mission after loiter, such as TLI and landing on the lunar surface will inflict mechanical loads but at significantly lower magnitudes than in the launch phase. A more detailed thermal profile of phase II will be provided prior to the kickoff meeting. 2.0 scope: this effort is aimed at developing technology applicable to composite struts for the altair lunar lander. 3.0 description of task requirements: the contractor shall perform the following tasks: 3.1 trade study the contractor shall conduct a trade study that shall consist of a parametric study examining a range of parameters encompassing the full assortment of altair struts (see attached appendix listing strut geometry and loads in the current altair design). The government will provide proe and/or nastran model of lunar lander showing current strut lengths, nodes, and geometry as defined in the government furnished information (GFI) chart under SOW section 6.0. The parametric analytical trade study of struts representative of altair is needed to determine the influence of each design parameter on strut behavior. Design curves showing the mass efficiency of the various strut design concepts is needed to determine the most structurally efficient design for the large number of dissimilar struts in the current 2008 point of departure design for altair. A comparison between the optimum composite design and an aluminum LI