The Digital Twin Paradigm for Future NASA and U.S. Air Force Vehicles

May combine two claims.

Compounding of factors-of-safety is pervasive and may lead to unnecessarily heavy structures and reduced performance without necessarily improving the actual safety of the vehicle or the probability of mission success.

“Additionally, compounding of factors-of-safety is pervasive and may lead to unnecessarily heavy structures and reduced performance without necessarily improving the actual safety of the vehicle or the probability of mission success.”

Probably not a substantial claim: may not pass S4 (based).

Inspection schedules for fleet management and sustainment are typically determined from experience with similar vehicles that have performed similar missions.

“Inspection schedules are typically determined from experience with similar vehicles that have performed similar missions.”

Probably not a substantial claim: may not pass S4 (based).

Inspection is often performed based on experience with the fleet leader, the vehicle in the fleet that experienced the most flights or the worst degradation.

“Often, inspection is performed based on experience with the fleet leader, the vehicle in the fleet that experienced the most flights or the worst degradation.”

Probably not a substantial claim: may not pass S2 (checkable).

The ability to fully understand degradation and anomalous events and foresee previously unknown unknowns may represent the difference between mission success and mission failure.

“Thus, the ability to fully understand degradation and anomalous events and foresee previously unknown unknowns may represent the difference between mission success and mission failure.”

Probably not a substantial claim: may not pass S3 (load-bearing).

If unacceptable degradation of a component is found during inspection of the fleet leader, it may be decided that all vehicles of that class be inspected immediately regardless of the specific history of each vehicle.

“If, for example, unacceptable degradation of a component was found during an inspection of the fleet leader, it may be decided that all vehicles of that class be inspected immediately regardless of the specific history of each vehicle.”

Probably not a substantial claim: may not pass S3 (load-bearing).

NASA-HDBK-5010 discusses separate conservatisms for crack size, applied loads, material properties, and analysis for known cracks in fracture critical hardware.

“An extreme case of codified conservatism is discussed in NASA-HDBK-5010 10 , where separate conservatisms for crack size, applied loads, material properties, and analysis are discussed for”

• cites NASA-HDBK-5010Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S4 (based).

The Digital Twin will decrease system weight by reducing reliance on statistical distributions of material properties, heuristic design philosophies, physical testing and assumed similitude between testing and operational conditions.

“It will also decrease system weight by reducing reliance on statistical distributions of material properties, heuristic design philosophies, physical testing and assumed similitude between testing and operational conditions.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

According to NASA-STD-5001A, a service life factor of 4.0 is applied to spaceflight structures made of well-characterized materials with sufficient load cycle data, while structures made of not well-characterized materials or complex failure modes may require an additional factor and testing.

“According to NASA-STD-5001A 1 , a service life factor of 4.0 is applied to”

• cites NASA-STD-5001ANot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing).

Known cracks in fracture critical hardware require special treatment wherein upper bounds for crack size estimate accounting for any possible nondetected adjacent cracks and/or crack tip extensions are required.

“Known cracks in fracture critical hardware require special treatment wherein upper bounds for crack size estimate accounting for”

• cites NASA-HDBK-5010Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Analyses of known flaws must show that the component has a service life factor of four and a safety factor of 1.5 against fracture.

“Finally, analyses of known flaws must show that the component has a service life factor of four and a safety factor of 1.5 against fracture.”

• cites NASA-HDBK-5010Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing).

AFRL Digital Twin: Spiral 1 is a plan to integrate existing state-of-the-art technologies, benchmark current capabilities and identify gaps using components from an existing U.S. Air Force vehicle, specifically the F-15, as a testbed.

“Among these steps is the Air Force Research Laboratory (AFRL) Digital Twin: Spiral 1 17 , a plan to integrate existing state-of-the-art technologies, benchmark current capabilities and identify gaps using components from an existing U.S. Air Force vehicle, specifically, the F-15, as a testbed.”

• cites [17]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S2 (checkable), S4 (based).

Complex missions, particularly those where external support is difficult or impossible, will necessitate complete real-time management of complex materials, structures and systems that will ultimately lead to self-aware vehicles.

“Complex missions, particularly those where external support is difficult or impossible, will necessitate complete real-time management of complex materials, structures and systems that will ultimately lead to”

• AssumptionRests on an assumption: The consequences of failure during a long-duration space mission, where the vehicle is far from home, will almost certainly be catastrophic.

Probably not a substantial claim: may not pass S4 (based). May combine two claims.

The Digital Twin continuously forecasts the health of the vehicle or system, the remaining useful life and the probability of mission success.

“By combining all of this information, the Digital Twin continuously forecasts the health of the vehicle or system, the remaining useful life and the probability of mission success.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The vision for the Digital Twin integrates the broad range of technologies with a singular focus.

“Unlike those individual visions, the vision for the Digital Twin integrates the broad range of technologies with a singular focus.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Verification depends on the ability to perform laboratory tests on a dedicated test structure identical to the flight structure, and loading, boundary conditions, and environment must be representative of flight conditions.

“In all of these cases,”

• cites NASA-STD-5001ANot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S2 (checkable), S4 (based).

If various best-physics models can be integrated with one another and with on-board sensor suites, they will form a basis for certification of vehicles by simulation and for real-time, continuous, health management of those vehicles during their missions.

“If various best-physics (i.e., the most accurate, physically realistic and robust) models can be integrated with one another and with on-board sensor suites, they will form a basis for certification of vehicles by simulation and for real-time, continuous, health management of those vehicles during their missions.”

Classified as probably not a substantial claim. May combine two claims.

As a result of future vehicle requirements, demands on structural materials will be greatly increased and structural margins will necessarily be decreased.

“As a result, demands on structural materials will be greatly increased and structural margins will necessarily be decreased.”

• AssumptionRests on an assumption: Future generations of NASA and U.S. Air Force vehicles will require lighter mass while being subjected to higher loads and more extreme service conditions over longer time periods than the present generation.

Probably not a substantial claim: may not pass S4 (based).

As a virtual instantiation of a flying vehicle, the Digital Twin is expected to be able to experience every event that its flying twin experiences.

“As a virtual instantiation of a flying vehicle, the Digital Twin is expected to be able to experience every event that its flying twin experiences.”

Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing). May combine two claims.

Because the vehicles needed for future extreme missions are unlikely to be developed using existing material forms, the design and development of new enabling materials is required and is well aligned with the NRC's ICME roadmap.

“Because the vehicles needed for future extreme missions are unlikely to be developed using existing material forms, the design and development of new enabling (e.g., multifunctional, nanostructured, ultra-durable) materials is required and is well aligned with the NRC's ICME roadmap.”

• cites [20]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing).

Application of continuum fracture mechanics analyses, including NASGRO fatigue crack growth analysis, is the foundation of much of the codified fracture control methodology.

“The application of continuum fracture mechanics analyses, including NASGRO fatigue crack growth analysis (see JSC 22267B 6 ), is the foundation of much of the codified fracture control methodology.”

• cites JSC 22267BNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

The ability to assess the evolution of defects is a critical element within the Digital Twin's on-board IVHM system and is well aligned with the NRC's advocacy for developments in Materials State Awareness.

“The ability to assess the evolution of defects is a critical element within the Digital Twin's on-board IVHM system and is well aligned with the NRC's advocacy for developments in Materials State Awareness.”

• cites [21]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing).

The protoflight approach requires a factor-of-safety for yield that is higher than the factor-of-safety used for prototype testing.

“The latter approach requires a factor-of-safety for yield that is higher than the factor-of-safety used for prototype testing.”

• cites NASA-STD-5001ANot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S4 (based). May combine two claims.

The Digital Twin can predict system response to safety critical events and uncover previously unknown issues before they become critical by comparing predicted and actual responses.

“The Digital Twin can also predict system response to safety critical events and uncover previously unknown issues before they become critical by comparing predicted and actual responses.”

Probably not a substantial claim: may not pass S2 (checkable), S4 (based). May combine two claims.

Because of its ability to mirror the life of a specific vehicle in an as-built state, the Digital Twin will necessarily revolutionize certification, fleet management and sustainment.

“Because of its ability to mirror the life of a specific vehicle in an as-built state, the Digital Twin will necessarily revolutionize certification, fleet management and sustainment.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Fracture critical hardware requires the additional imposition of damage tolerance requirements.

“Fracture critical hardware requires the additional imposition of damage tolerance requirements (see, for example, NASA-STD-5019 2 ).”

• cites NASA-STD-5019Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S2 (checkable), S4 (based). May combine two claims.

The Digital Twin concept is unlikely to attain maturity for many decades, so a series of intermediate steps is required.

“However, such an ambitious concept is unlikely to attain maturity for many decades, so a series of intermediate steps is required.”

• AssumptionRests on an assumption: The Digital Twin concept is unlikely to attain maturity for many decades.

May combine two claims.

The extensive legacy of historical flight information incorporated in standards and handbooks will likely be insufficient to either certify future extreme vehicles or to guarantee mission success.

“Thus, the extensive legacy of historical flight information incorporated in the various standards and handbooks that were based on decades of aircraft and spacecraft design experience, will likely be insufficient to either certify future extreme vehicles or to guarantee mission success.”

• AssumptionRests on an assumption: Future generations of vehicles will rely on increasingly complex, heterogeneous and multifunctional material forms with increasingly complex failure modes.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Minimum design and test factors-of-safety for metallic and composite structures in NASA-STD-5001A vary widely depending on circumstance and can be as large as 2.0 depending on material and local structural configuration.

“These factors vary widely depending on circumstance and can be as large as 2.0 depending on the material and local structural configuration.”

• cites NASA-STD-5001ANot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing).

Worst-case limit loads for the mission must be used to compute the far field stress state at the location of the detected crack.

“Additionally, worst-case limit loads for the mission must be used to compute the far field stress state at the location of the detected crack.”

• cites NASA-HDBK-5010Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S2 (checkable), S4 (based).

An understanding of the exact state of the structure of the vehicle or its systems, including existence of defects at the microstructural and possibly atomistic scale, is required as a baseline for ultra-high fidelity simulations.

“Additionally, an understanding of the exact state of the structure of the vehicle or its systems, including the existence of defects at the microstructural and, possibly, the atomistic scale, is required as a baseline for ultra-high fidelity simulations.”

Probably not a substantial claim: may not pass S4 (based).

The Digital Twin will enable mission managers to make knowledgeable decisions regarding the consequences of possible in-flight changes to a vehicle's mission.

“Additionally, it will enable mission managers to make knowledgeable decisions regarding the consequences of possible in-flight changes to a vehicle's mission.”

Probably not a substantial claim: may not pass S4 (based).

Once the vehicle is launched, the Digital Twin will increase the reliability of the flying vehicle because of its ability to continuously monitor and mitigate degradation and anomalous events.

“Once the vehicle is launched, the Digital Twin will increase the reliability of the flying vehicle because of its ability to continuously monitor and mitigate degradation and anomalous events.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Because of apparent scatter in material response under cyclic and creep loading, corresponding factors-of-safety are even larger.

“Because of the apparent scatter in material response under cyclic and creep loading, the corresponding factors are even larger.”

• cites NASA-STD-5001ANot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Many of the technologies critical for the Digital Twin are currently being developed under related visions for multi-scale and multi-physics modeling, structural health management, high-performance computing and others.

“Many of the technologies critical for the Digital Twin are currently being developed under related visions for multi-scale and multi-physics modeling, structural health management, highperformance computing and others.”

Probably not a substantial claim: may not pass S4 (based). May combine two claims.

The systems on board the Digital Twin are capable of mitigating damage or degradation by activating self-healing mechanisms or by recommending changes in mission profile to decrease loadings, thereby increasing both the life span and the probability of mission success.

“Finally, the systems on board the Digital Twin are capable of mitigating damage or degradation by activating self-healing mechanisms or by recommending changes in mission profile to decrease loadings thereby increasing both the life span and the probability of mission success.”

May combine two claims.

Codified practices tend to be reactive rather than proactive and are often based on heuristic experience, worst-case scenarios and fleet leaders rather than on the specific material, structural configuration and usage of an individual vehicle.

“However, they tend to be reactive rather than proactive and are often based on heuristic experience, worst-case scenarios and fleet leaders rather than on the specific material, structural configuration and usage of an individual vehicle.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The handbook requires analysts to use material properties corresponding to the lower bound of fracture toughness and the upper bound of fatigue crack growth rate.

“The handbook requires analysts to use material properties corresponding to the lower bound of fracture toughness and the upper bound of fatigue crack growth rate (da/dN vs. ΔK) as shown in Figure 2.”

• cites NASA-HDBK-5010Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing).

Upper bounds of fatigue crack growth rate curves are either visually estimated or statistically estimated as being three standard deviations above the mean values.

“Upper bounds of fatigue crack growth rate curves are either visually estimated or statistically estimated as being three standard deviations above the mean values.”

• cites NASA-HDBK-5010Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S2 (checkable), S4 (based).

By replacing conventional engineering practices with an understanding of the degradation of an individual vehicle or vehicle system, the paradigm of the Digital Twin will impact the way that physical items ranging from micro-devices to civil infrastructure are developed, certified and maintained.

“By replacing conventional engineering practices with an understanding of the degradation of an individual vehicle or vehicle system, the paradigm of the Digital Twin will impact the way that physical items ranging from micro-devices to civil infrastructure are developed, certified and maintained.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The Digital Twin paradigm can provide focus to the recent advocacy of the National Science Foundation and the National Research Council in the areas of Simulation Based Engineering Science, Integrated Computational Materials Engineering and Materials State Awareness.

“In addition to its prominence in the recently-published roadmaps of NASA's Office of Chief Technologist (OCT) [15][16] and plans of the Air Force Research Laboratory [17][18] , the Digital Twin paradigm can provide focus to the recent advocacy of the National Science Foundation (NSF) and the National Research Council (NRC) in the areas of Simulation Based Engineering Science (SBES) 19 , Integrated”

• cites [19]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites [20]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites [21]Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S4 (based).

By exercising ultra-high fidelity approaches on flight hardware, the shortcomings of the existing state-of-the-art in multiscale modeling, in-situ experimentation and material state awareness will be highlighted.

“By exercising such ultra-high fidelity approaches on flight hardware, the shortcomings of the existing state-of-the-art in multiscale modeling, in-situ experimentation and material state awareness will be highlighted.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The crack size assumed for analysis is a combination of NDE-detected crack dimensions and an adjustment based on NDE detection capability.

“Here, the crack size assumed for analysis (2c A ) is a combination of the NDE-detected crack dimensions (2c D ) and an adjustment based on the NDE detection capability (2c N ).”

• cites NASA-HDBK-5010Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

Potential spin-offs from the development of the Digital Twin span the breadth of the Nation's industrial and manufacturing sectors, infrastructure and development of nanotechnology.

“Potential spin-offs from the development of the Digital Twin span the breadth of the Nation's industrial and manufacturing sectors, infrastructure and development of nanotechnology.”