2.1 Design Rationale

One of the primary requirements of the Ranger NBV design was that the robotics package was to have roughly the same force and reach capability as an astronaut in a space suit. This requirement was set so that Ranger NBV would be capable of performing real tasks that were previously only planned for EVA. Another requirement was that it should be capable of full 6 DOF free flight. This allowed a much larger set of tasks to be considered, including large scale assembly tasks, and multi-stage repairs where many of the task elements could not be stored in the same locations in which they needed to be used. Additionally, the free flight system was to have precise position and attitude estimation and control. This capability would allow the neutral buoyancy simulation to be much more accurate because the advanced flight control system would enable the vehicle to mimic space flight dynamics. This would allow realistic training for proximity operations, along with final phase rendezvous and docking. This total system was designed to be a test bed and trainer for all aspects of large scale free flight and attached robotic space operations. It could also be used to demonstrate how operations performance capability is related to vehicle configuration. Operators could compare performance on the same task with various levels of vehicle capability. For example one task could be attempted using two arms, and then compared with the same task with the operator using only one arm. This same concept could be repeated with many different tasks, and vehicle systems, which would help to determine the value of each of them to a particular task element.
In addition to providing valuable insight into robotic operations, Ranger NBV was also to serve as a proving ground for the space robotic mechanical and electronic hardware. Complex drive trains often do not perform as originally intended. Only repeated operations reveal unexpected anomalies that are caused by component wear, and unexpected mechanical loads. Additionally, electronic power systems occasionally do not stand up to repeated high stress operations. Ranger NBV was to be used to help find and enhance any weak elements of the original design of these systems.