Spacecraft reaction wheel maneuvers are limited by the maximum torque and/or angular momentum which the wheels can provide. For an n-wheel configuration, the torque or momentum envelope can be obtained by projecting the ndimensional hypercube, representing the domain boundary of individual wheel torques or momenta, into three dimensional space via the 3xn matrix of wheel axes. In this paper, the properties of the projected hypercube are discussed, and algorithms are proposed for determining this maximal torque or momentum envelope for general wheel configurations. Practical implementation strategies for specific wheel configurations are also considered.

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A simple observer and controller has been formulated for a low bandwidth yaw attitude control loop on a synchronous orbit momentum bias spacecraft. Operation of the system is entirely autonomous, with the only external reference required being a measurement of the spacecraft roll attitude. Low-level torque actuation is provided by a single magnetic coil that is mounted in the spacecraft body at an arbitrary orientation in the roll/yaw plane. This control system design provides much better pointing accuracy and rate stability for a given bias momentum than previous techniques. Simulated performance during a magnetic storm is presented for a Vee-Wheel momentum bias configuration. The properties of the geomagnetic field at synchronous altitude that are pertinent to spacecraft attitude control system design are described in the Appendix.

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Within the broad aerospace community the importance of identifying, documenting and widely sharing lessons learned during system development, flight test, operational or research programs/projects is broadly acknowledged. Documenting and sharing lessons learned helps managers and engineers to minimize project risk and improve performance of their systems. Often significant lessons learned on a project fail to get captured even though they are well known 'tribal knowledge" amongst the project team members. The physical act of actually writing down and documenting these lessons learned for the next generation of NASA GN&C engineers fails to happen on some projects for various reasons. In this paper we will first review the importance of capturing lessons learned and then wlll discuss reasons why some lessons are not documented. A simple proven approach called 'Pause and Learn' will be highlighted as a proven low-impact method of organizational learning that could foster the timely capture of critical lessons learned. Lastly some examples of "lost"GN&C lessons learned from the aeronautics, spacecraft and launch vehicle domains are briefly highlighted. In the context of this paper "lost" refers to lessons that have not achieved broad visibility within the NASA-wide GN&C CoP because they are either