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Schedule and Activity Generator / Estimator Model (SAGE)

Disclaimer: This material is being kept online for historical purposes. The model, simulation or tool described is no longer maintained. It is no longer available on request, and/or may not function on current computer systems.


A screen shot of the Schedule and Activity Generator / Estimator (SAGE) assessment tool.
A screen shot of the Schedule and Activity Generator / Estimator (SAGE) assessment tool.

The SAGE model is a Visual Basic application with a relatively simple graphic user interface for an operations analyst to define the design of each stage of a reusable launch system. The SAGE model works ideally for reusable booster definition at a conceptual level. Results are best used comparatively, such as relative to Shuttle or relative to other concepts assessed with the tool. However, absolute values may be used as rough-order-of-magnitude (ROM) estimates in the analysis of recurring ground systems turnaround effort.


The SAGE model inputs required for a new concept are best defined relative to the baseline Shuttle file. Example Input Types:

  • Ascent propulsion, number of engines, etc.
  • On-orbit propulsion, number of thrusters, etc.
  • Fluids required, distinct type, quantity, etc.


  • Schedules and timelines for the turnaround of the defined hardware.


In using any model to contribute significantly or even partially to an important decision, users should be aware of the limitations of the model. Users should be aware that the SAGE model:

  • Emphasizes reusable vehicle design complexity and it's relation to operational complexity and effectiveness.
  • Captures design features that favor operational, recurring launch, "-ilities".
  • Does not address organizational design, as inputs or drivers (efficiency, process, practices, acquisition approach, supply chain management, best practices or business approaches).

Papers and Presentations: