Battista barlowpmc conference 2012 rev. 2

All Subsystems Are Not Created EqualAlternative Scheduling Approaches for Spacecraft Subsystem Development

Dewey E. Barlowcorina c. k. battista

February 2012 Orlando, FL

All Subsystems Are Not Created Equal

Contents

• 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


Current NASA Environment

Used by permission.


Current NASA Environment (7120.5)

Figure 3.1 – NASA Project Lifecycle

TRL 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

TRL 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


TRL 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?


TRL 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


AO 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

AO 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

Potential 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?

Potential 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

Potential 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

Potential 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

Potential Solutions – Summary


All solutions involve some level of decoupling and decompression of subsystem schedules

Recommendations


1 – Perform schedule risk assessments at the subsystem level to predict probable range of deliveries

Recommendations


2 – Analyze data from schedule risk assessments to detect groupings or patterns

Conclusion


3 – Select the appropriate schedule approach


ExampleLow TRL

The Initial TRL Estimate Influences the Parameters of Probability Distribution on Delivery

M

O – OptimisticM – Most LikelyP – PessimisticT – Target (say 70%)

O P

T

High TRL

M

O P

T


OPLExample

The Aggregate Probability Distribution Targets May Offer Patterns to Help Plan Subsystem Schedule Development Approaches

PDU

FSW

PSE NMSRF

Late Start Common Start Early Start