Methods for Determining Initial Feasibility: Identifying the Accessible Trade Space

Abstract

The purpose of the NASA Pre-Phase A project life cycle phase is, “To produce a broad spectrum of ideas and alternatives for missions from which new programs/projects can be selected, and to determine the feasibility of [the] desired system, develop mission concepts, draft system-level requirements, assess performance, cost, and schedule feasibility; identify potential technology needs, and scope.” There are, however, limited resources (time, money, workforce) with which to conduct this trade space exploration. The question therefore is how to conduct this trade space exploration most efficiently, and how to produce a broad spectrum of ideas and alternatives for missions from which new programs/projects can be selected. Trade space exploration efficiency is defined as the number of selectable concepts explored multiplied by the work spent to explore them, divided by the sum of the number of selectable concepts explored multiplied by the work spent to explore them and the number of non-selectable concepts explored multiplied by the work spent to explore the non-selectable concepts. Increases in efficiency then dictate that both the number of non-selectable concepts explored, and the work spent exploring them, be minimized. Top down, fundamental physics based, analogy based, and parametric based techniques require less work to explore concepts than traditional “grass-roots”, “bottoms-up”, first principles estimation techniques, increasing trade space exploration efficiency. Top down, fundamental physics based, analogy based, and parametric based techniques can also be used to create relationships between key performance, technical, and cost parameters. These relationships can then be used with the cost cap, performance floor, and technical wall boundary conditions to identify the accessible trade space. This alone can drastically reduce the number of non-selectable concepts explored, dramatically increasing trade space exploration efficiency. The approaches to derive and use the top down, fundamental physics based, analogy based, and parametric based relationships for identifying the accessible trade space has been pioneered in initial feasibility studies of space mission concepts in the A-Team at the Jet Propulsion Laboratory.