the spacecraft interface at 120-degree intervals. Each CST has four truss links and four tendon-actuated  hinge joints with the base of each CST mounted to a simple turntable (to provide a [fifth] rotary degree of  freedom). The enclosure bag (EB) is attached to the circular interface structure at its base and folded in  the center portion of the space between the stowed CSTs. The EB has a simple inflatable ring integrated  at its open end that is inflated to provide a large circular opening for acquiring an asteroid. The system is redundant since the mission can be successfully completed even if one of the CSTs completely fails to  operate. Design and performance specifications for the CST are given in Table 3.  TALISMAN Structural Sizing Analysis One of the key advantages of the TALISMAN architecture is its structural simplicity and efficiency. These  attributes are achieved by using a modular, periodic tension-compression design that lends itself well to analytical modeling. Closed-form, parametric equations were derived to calculate the member loads and tip deflection and allow systematic optimization of the key structural components of TALISMAN, including the core truss links, the spreaders and the tension elements. The analytical equations were derived using the following assumptions; spreaders and truss links have small axial deformations, all tension elements are always under load (achieved in practice using either active actuator control or passive springs) andmaterial behavior is linear elastic. Typical requirements that must be specified are for in-plane (refers to  those aligned with the plane of the spreaders; the stiffest plane), out-of-plane and torsional tip loads, and the required tip stiffness. The derived equations can be used to determine the optimum sizing, pretension  level and mass of the system while taking into account constraints on the minimum gauge of thin-walled  members, and local strength and buckling. A spreadsheet-based TALISMAN design tool was generated  using these equations to enable rapid design studies and to investigate the sensitivities of various parameters including: number, length and cross-section of primary arm links; spreader height and  geometry; cross-section of tension elements; material properties; safety factors on strength and buckling;lacing pattern of truss diagonals and; in-plane, out-of-plane and torsional tip loads and tip deflection.  Figure 10 illustrates the geometry used in the model as well as load and displacement variables. The TALISMAN design tool requires the user to input the basic geometry, tip loading and material  properties and it outputs the internal loads, sizing and masses of all members. The geometric parameters  include the length, number and cross-section of the arm links and the height of the spreaders. These  parameters are not included in the optimization since they are typically dictated by the requirements for a specific application, such as component packaging volume, or spreader impingement into the operational  work space. The links and spreaders are optimized by iterating on and requiring the value of a sizing  parameter (either area or thickness) be equivalent when both strength and buckling constraints are satisfied. The tendons are sized for axial stiffness and strength, as they provide the primary in-plane  stiffness. Separate safety factors are specified for the compressive and tension members, due to the typically higher factor on strength for tendons. The TALISMAN is designed for high structural efficiency in  the plane of articulation. However, off-nominal loads, such as out-of-plane or torsion, are accounted for in  the design process. Some examples of these off-nominal loads include push-off lateral loads induced by  an attached Extra Vehicular Astronaut (EVA) astronaut, or torsional loads induced by lateral loads when the arm links are at different angles. For the CST, the worst-case torsional load was used for sizing. This torsional load occurs when all of the arm links ahead of the root link are perpendicular to the root and alateral tip load is applied, thus creating a large moment that is reacted by the truss diagonals in the first  bay of the link closest to the root or base.   The current design tool is intended to produce optimized TALISMAN architectures that are conservative  by using reasonable and current material properties and worst-case loading scenarios. The structural  members are sized for a tip load applied to a fully extended (straight-out) manipulator pose (i.e. the longest moment arm), with any lateral loads inducing compression in the truss longerons (through  bending and torsion). The sizing is based on the maximum loads induced in the structural members, usually those that are at or near the root; this allows equivalent cross-sections to be used for each set of  members, resulting in easy and inexpensive manufacture or purchase of off-the-shelf components. For  example, extruded beam sections with standard rectangular cross-sections were inexpensively  purchased and cut on a water-jet machine to obtain the optimal truss lacing pattern determined by this  411