GP-B Post-Flight Analysis—Final Report - Gravity Probe B - Stanford ...

6.3.1 Incremental PrototypingThe period from 1985-1995 yielded significant advances in GP-B hardware development, due in large part toBradford Parkinson's decision to use a methodology called “incremental prototyping.” Incremental prototypinginvolved the rapid development and testing of increasingly more prototypical hardware. Developing GP-B'sunique and cutting-edge technology required an approach that would maximize the capability of the hardwareand software, while minimizing costs and development time. In the classical, aerospace hardware developmentapproach, a number of years would first be spent defining a requirements specification, and then an aerospacecontractor, such as Ball Aerospace, Lockheed Missiles and Space, Fairchild Aerospace, or General ElectricAerospace would spend more years designing and building hardware to meet the specifications. This would be atime-consuming and expensive process. Furthermore, this process would not necessarily yield the desiredresults, and more iterations would often be required.During the flight hardware development years, GP-B required technology development consistent with asuitable flight readiness level. Thus, rather than adhering to the classical development model, one of ProfessorParkinson's major contributions was to use incremental prototyping for developing the novel and complextechnology required by the experiment. Hardware was rapidly prototyped and tested in order to determine howclose it would come to meeting specified requirements and also to determine how difficult it would be tomanufacture and test. Incremental prototyping allowed the team to develop new technologies by building actualhardware, while learning valuable lessons in the process. When the time was right, the team knew what theycould build and how to build and test it. Eventually these “lessons learned” were applied to the development ofactual flight hardware, allowing the team to build flight hardware more efficiently, in less time, and moreaccurately than would have been possible using the classical “build-to-requirements” approach.Incremental prototyping was used to develop the technologies described in each of the five subsections below.6.3.1.1 Probes A, B, and CFigure 6-4. Probe C: testing in clean room (left), ready for integration with dewar (center) and connectionsinside the top hat interface (right).The cryogenic Vacuum Probe, when inserted into the dewar, includes the science experiment. The Probe mustmaintain an internal temperature of 2.0K, while interfacing to external systems at ambient temperature. TheProbe contains a sequence of four windows that enable the telescope to view the guide star. The Probe also hadto minimize heat leakage, while providing an interface for ~600 cables to the external ambient temperatureenvironment. Figure 6-4 shows various views of Probe C, the final flight probe.150 March 2007 Chapter 6 — The GP-B Management Experiment