All Subsystems Are Not Created EqualAlternative Scheduling Approaches for Spacecraft Subsystem Development Dewey E. Barlow corina c. k. battista February 2012 Orlando, FL
All Subsystems Are Not Created EqualContents • Current NASA Environment • Technology Readiness Level (TRL) Considerations • Technology Race Analogy • AO Process Implications • Potential Solutions • Staggered Starts • MIN TRL6 First • Staggered Finishes • Recommendations • Conclusion
All Subsystems Are Not Created EqualCurrent NASA Environment Used by permission.
All Subsystems Are Not Created EqualCurrent NASA Environment (7120.5) Figure 3.1 – NASA Project Lifecycle
All Subsystems Are Not Created EqualTRL Considerations When many subsystems are involved, the fact that the completion of an entire spacecraft is more likely to be delayed due to the slippage in the development of one immature subsystem is supported by historical evidence
All Subsystems Are Not Created EqualTRL Considerations It is difficult at best to predict the timeframes required for new and emerging technology because: • We have limited relevant historical data • Even when relevant historical data exists, past performance may not be an accurate indicator of future performance since new independent variables are constantly being introduced • Technology development is often an iterative process - We find out what works often by eliminating what does not (Thomas Edison and the light bulb) • Resource units are not highly correlated with duration
All Subsystems Are Not Created EqualTRL Considerations Since schedule requirements for technology development activities are subject to variation and difficult to predict, how do we expect low TRL hardware to stay on pace with proven technologies?
All Subsystems Are Not Created EqualTRL Considerations Forcing low TRL subsystems to keep pace with proven technologies can induce inefficiency in execution, create schedule risk, and contribute to cost and schedule overruns
All Subsystems Are Not Created EqualAO Process Implications Compressing an already critical subsystem or instrument’s critical path may provide an overly optimistic and ultimately unachievable timeframe for development. Subsystems that have the most schedule risk have the least amount of available schedule reserve
All Subsystems Are Not Created EqualAO Process Implications NASA projects are expected to comply with generally-accepted schedule reserve guidelines so development timeframes for these already compressed low TRL subsystems are reduced even further
All Subsystems Are Not Created EqualPotential Solution 1 – Staggered Starts (SS) What if we started with an unconstrained environment and allowed the subsystems and instrument teams to define their schedule requirements given known resource constraints and using adequate calculated schedule reserve commensurate with the level of technical and execution risk?
All Subsystems Are Not Created EqualPotential Solution 1 – Staggered Starts (SS) Staggered Starts allows each subsystem to develop on their own schedule and achieve compliance with 7120.5 through delta mission level reviews and waivers
All Subsystems Are Not Created EqualPotential Solution 2 – MIN TRL First The subsystems and instruments that are not at TRL 6 would be required to engage in technology development and demonstration activities to achieve TRL 6 prior to engaging all subsystems
All Subsystems Are Not Created EqualPotential Solution 3 – Staggered Finishes Staggered Finishes allows each subsystem to develop on their own schedule/deliver early and achieve compliance with 7120.5 through delta mission level reviews and waivers
All Subsystems Are Not Created EqualPotential Solutions – Summary All solutions involve some level of decoupling and decompression of subsystem schedules
All Subsystems Are Not Created EqualRecommendations 1 – Perform schedule risk assessments at the subsystem level to predict probable range of deliveries
All Subsystems Are Not Created EqualRecommendations 2 – Analyze data from schedule risk assessments to detect groupings or patterns
All Subsystems Are Not Created EqualConclusion 3 – Select the appropriate schedule approach
All Subsystems Are Not Created Equal ExampleLowTRL M T O PHighTRL MO – Optimistic TM – Most LikelyP – Pessimistic O PT – Target (say 70%) The Initial TRL Estimate Influences the Parameters of Probability Distribution on Delivery
All Subsystems Are Not Created EqualExample OPL FSW PDU PSE RF NMS Late Start Common Start Early Start The Aggregate Probability Distribution Targets May Offer Patterns to Help Plan Subsystem Schedule Development Approaches