.  

c. Part does not serve as primary or secondary containment. 

d. Part does not serve as redundant structures for fail-safe criteria per NASA-STD-5019, 
Fracture Control Requirements for Spaceflight Hardware. 

e. Part is not designated “Non-Hazardous Leak Before Burst” per NASA-STD-5019. 

f. Failure of part does not cause debris or contamination concerns, as defined by the 
Non-Fracture Critical Low-Release Mass classification per NASA-STD-5019, NASA-STD-
6016, and/or other project/program requirements. 

Contamination requirements are commonly defined in interface control drawings. 

g. Failure of part causes only minor inconvenience to crew or operations. 

h. Failure of part does not alter structural margins or related evaluations on other 
hardware. 

i. Failure of part does not adversely affect other systems or operations. 

j. Failure of part does not affect minimum mission operations. 

[Rationale:  Class C designs have the lowest performance requirements and the fewest controls 
for realizing the performance specifications and process repeatability.]  

This class of parts allows tailored quality assurance and material performance controls due to 
negligible consequences of failure. Consideration of consequence have to include all possible 
end uses of the part, including protoflight scenarios or development hardware that may 
transition to actual flight hardware. 

For the above checklist, failure can be defined as any failure condition (including, but not 
limited to, yielding, buckling, cracking, fracture, leak, wear/galling, or corrosion) where the part 
does not achieve every aspect of its design intent. 


NASA-STD-6030 imposes a large number of process AMRs for Class A and Class B 
parts. Although Class C parts have a negligible consequence of failure, a minimum set of 
requirements is kept to ensure that flight parts still meet their intended function. A large number 
of AMRs are eliminated, and the remaining set of AMRs is selected to ensure that the AM 
process produces sound material. 

Many of the remaining AMRs were simplified to reduce cost, schedule, and complexity. The 
following are examples of simplified process controls for Class C parts: 

 For process qualification, only six tensile coupons are to be made and tested using the 
machine setup (see section 5.4 of this NASA Technical Standard).  
 For process control, the production parts are built using the identical machine setup as 
the qualification coupons. 
 For process verification, only two tensile coupons are to be included in the production 
build (see section 4.11 of this NASA Technical Standard). 

AMRs for NDE and preproduction articles are removed. AMRs for statistical methods are 
also removed (e.g., MPS, PCRD, materials allowables, and design values).  

The AMCP and PPP are required for Class C parts, although these plans are simplified 
since the majority of AMRs are waived. The remaining AMRs required document the process 
controls, part usage, and justification for part classification to ensure all concerned understand 
what will be done and what is further tailored.  

Choosing to tailor out process controls and process verifications intended to ensure functionality 
of Class C parts is not encouraged, but it may be acceptable for the risk posture of some projects 
provided those projects meet any higher-level platform requirements (e.g., a CubeSat 
transitioning through the International Space Station [ISS] habitat). 

Note that all parts still need to meet NASA-STD-6016 requirements necessary to ensure safety of 
flight (e.g., flammability, toxic offgassing) and vehicle compatibility (e.g., vacuum outgassing). 


 Exempt Parts 

[AMR-11]  A part shall be designated as Exempt provided that all of the following criteria are 
satisfied and it meets all criteria for Class C (see section 4.3.1.3), which exempts it from all other 
requirements in this NASA Technical Standard: 

a. The part does not require any form of structural assessment. 

b. The part does not permanently interface to, or attach to, the launch vehicle, 
spacecraft, habitable module, or any subsystems thereof. 

c. Except for use in habitable crew spaces, the part does not provide any functionality or 
serve any purpose to the launch vehicle, spacecraft, or any subsystems thereof. 

[Rationale:  Every AM part requires evaluation for classification, and documentation thereof, 
even if that classification results in no further requirements.] 

Parts that meet the criteria for Exempt are still recommended for Class C, if practical. 

Documentation of rationale and approval of an Exempt part designation may take place in a 
number of different ways, including, but not limited to, a Materials Identification and Usage List 
(MIUL), MUA, contract memorandum, material certification, or safety review hazard report. A 
detailed rationale addressing the criteria of sections 4.3.1.3 and 4.3.1.4 of this NASA Technical 
Standard is recommended. A specific mechanism for documentation and approval is 
intentionally omitted from this requirement since many programs using this designation may 
have greatly reduced numbers of requirements or deliverables. As such, it is important that 
projects and programs that allow Exempt parts define requirements for documentation and 
approval. 

Note that all parts must still meet NASA-STD-6016 requirements necessary to ensure safety of 
flight (e.g., flammability, offgassing, and compatibility) and vehicle compatibility (e.g., vacuum 
outgassing). 


 Secondary Classification 

[AMR-12]  For Class A and B parts, a secondary classification shall be assigned based on 
structural demand and AM risk, according to Table 2, Structural Demand, Metallic AM Parts, 
Table 3, Structural Demand, Polymeric AM Parts, and Table 4, Assessment Criteria for Additive 
Manufacturing Risk (also see Figure 4). 

 Structural Demand 

The purpose of the structural demand assessment is to identify the relative structural 
performance demands on the part. Parts with high structural margin are less sensitive to 
variations and uncertainty in material performance. The use of structural demand in 
classification of parts is not uncommon (e.g., see the classification system in SAE AMS2175, 
Castings, Classification and Inspection of); however, past use of such structural criteria has 
typically been simplistic and non-specific. The criteria herein are intended to be sufficiently 
comprehensive of common structural failure modes to allow the margin required in each 
assessment to be specific to its property. For example, the strength margin requirements are set 
to cover potential variability in strengths, not to bound fatigue or fracture behavior, as these 
properties are addressed directly. The requirements of the above tables may be tailored to 
account for significant conservatisms present in analysis methods or material properties; 
however, the intent of the criteria must be maintained, and rigorous substantiation of the 
tailoring request will be required. 

The assessment of structural demand does not levy or alter any of the structural requirements, 
factors of safety, or required structural margins for any hardware. The criteria for low 
structural demand in the tables are used only as a consistent indicator for the level of demand 
(e.g., stress) on the part to inform the amount of structural risk associated with the part. 

For each AM part, the results of the structural assessment conducted in accordance with the 
levied structural requirements are compared against the appropriate table for material type:  
metals (Table 2) or polymers (Table 3). The criteria in the table are only applicable when that 
criteria is required by the structural requirements. For example, the fracture mechanics life 
criteria is not applicable to non-fracture critical hardware that do not require this evaluation. 
There is not an expectation for any structural evaluations beyond those required by the 
structural requirements to be conducted solely for purposes of classification.  

If all structural assessment requirements for a given part meet or exceed those in Table 2 for 
metals and Table 3 for polymers, then the part is considered to have a low structural demand 
and is assigned a subclass of 3 or 4 pending evaluation of AM risk (see Tables 2 and 3).  
Otherwise, the part is considered to be high structural demand. 


Table 2—Structural Demand, Metallic AM Parts 
Analysis Input/Material Property Criteria for Low Structural Demand 
Load cases Well-defined or bounded loads environment 
Environmental degradation Only due to temperature 
Ultimate strength Minimum margin* ≥0.3 
Yield strength Minimum margin* ≥0.2 
Point strain Local plastic strain <0.005 
High cycle fatigue, improved 
surfaces 
Cyclic stress range (including any required factors) ≤80% of 
applicable fatigue limit  
High cycle fatigue, as-built surfaces  Cyclic stress range (including any required factors) ≤60% of 
applicable fatigue limit  
Low cycle fatigue No predicted cyclic plastic strain 
Fracture mechanics life 20x life factor 
Creep strain No predicted creep strain 
*Margin = [design/(operation * safety factor)] – 1 (see commentary) 

The following notes are provided for some of the above criteria for metallic AM systems: 

Loads Cases — The loads environment for spaceflight systems and structures is rarely 
comprehensively understood. Examples of loads that are not well defined or bounded include 
parts passing through or operating near resonance, or parts requiring forced response and 
coupled dynamic loads analysis to predict fluid-structure interaction. Commonplace 
uncertainties (e.g., the precise magnitude of a random vibration or loads due to quasi-static 
pressure or thrust loads) are considered sufficiently defined and do not violate the intent of this 
criterion. 

Environmental Degradation — To meet the low structural demand criterion, temperature is the 
only allowed source of environmental material degradation. Exposure to a hydrogen embrittling 
environment would be an example failing this criterion. 

Ultimate and Yield Strength — These assessments are performed as defined by the governing 
structural requirements. Methodologies for yield and ultimate evaluations often differ by 
analysis organization. The requirements to demonstrate low structural demand are expressed as 
the margin needed in excess of the required factor of safety, per standard NASA notation (see 
Table 2 and discussion of “Margin” here). 

Margin — Margin refers to the common definition of the margin of safety, as defined in 
structural requirements such as NASA-STD-5001, Structural Design and Test Factors of Safety 
for Spaceflight Hardware, or NASA-STD-5012, Strength and Life Assessment Requirements for 
Liquid-Fueled Space Propulsion System Engines. It is the fraction by which the allowable 
capability (σdesign) exceeds the applied load (σoperation) as multiplied by the factor of safety. The 
margins used in the structural demand assessment criteria are those defined by the method of 


margin calculation from the levied structural requirements and should come directly from the 
structural assessment. Margins should not have to be recalculated for evaluation of part 
classification. Appropriate tailoring to equivalent metrics may be used in cases where the 
structural requirements use other means of calculating margin (also applies to Table 3). 

Point Strain — This evaluation is required for all parts and is intended to limit the dependence 
on ductility for low structural demand parts. Linear elastic evaluation where peak, local von 
Mises stress remains below yield is sufficient. Proper modeling practice for converged mesh 
discretization dependence within stress models is assumed. For cases where peak, local von 
Mises stress is greater than yield, any approved method of calculating plastic strain is 
acceptable (e.g., elastic-plastic finite element analysis or Neuber notch analysis). 

High Cycle Fatigue — For low structural demand, the cyclic stress must be below the defined 
fatigue limit cyclic stress by the percentage indicated. Fatigue initiation life evaluation includes 
the influence of the surface condition. The factors provided for “improved surfaces” intend that 
such surfaces have been altered through machining or other chemical or mechanical processes 
to eradicate or mitigate the effects of the as-built L-PBF surface on fatigue life as substantiated 
experimentally. Part surfaces that remain in the as-built condition are to be evaluated against 
fatigue data developed with a representative as-built surface. 

Low Cycle Fatigue — Plastic point strains are not intended to occur cyclically for parts with low 
structural demand. 

Fracture Mechanics Life — This evaluation is only intended for parts subject to damage 
tolerance analysis. For low structural demand, the damage tolerance assessment demonstrates 
life ≥20 missions, based on a starting defect applicable to the inspection method. 

Creep — Confirmation of no-creep deformation is intended only in cases where creep-inducing 
environments are present. 


Table 3—Structural Demand, Polymeric AM Parts 
Analysis Input/Material Property Criteria for Low Structural Demand 
All materials 
Load cases Well-defined or bounded loads environment 
Environmental Degradation 
Only allowed due to temperature and moisture, if 
specific environmental performance data exist. Design 
environment temperature does not cross the Tg. 
Fatigue Cyclic stress range (including any required factors) 
≤50% of applicable fatigue limit  
Sustained stress/creep strain No sustained stress† and no predicted creep strain 
Material with elongation at failure ≥3% in application environment 
Ultimate strength Minimum margin* ≥0.5 
Yield strength‡ Minimum margin* ≥0.3 
Material with elongation at failure <3% in application environment 
Ultimate strength# Minimum margin* ≥2.0 
†Includes assembly stress (tight snap fit connections, shrink fits, fastener preloads) and operational stress . 
‡Yield strength defined by secant modulus to specified strain, by specified offset strain, or as otherwise defined by 
structural assessment requirements. 
#Ultimate strength assessed against local maximum principal stress at stress concentrations (brittle material design 
rules) for low ductility materials. 
*Margin = [design/(operation * safety factor)] – 1 (see commentary following Table 2) 

 Additive Manufacturing Risk 

New opportunities presented by the AM process (e.g., previously impossible geometries) also 
present new risks in the use of the parts. Limitations in the ability to characterize defect 
attributes and verify defect densities in finished parts are prominent among these risks. The 
questions in the AM risk criteria table are phrased such that a positive answer corresponds to a 
zero score, not contributing to AM risk. A lower score equates to lower risk. Improved surfaces 
refer to areas that have had material removed from support structure mating surfaces such that 
only bulk material remains. 

For each AM part, an AM risk assessment is to be conducted and compared against the table for 
the applicable feedstock type. If the summed AM risk scores less than 5, then the part will be 
assigned low AM risk and placed in subclass 2 or 4. If the summed AM risk scores greater than 
or equal to 5, then the part will be assigned high AM risk and placed in subclass 1 or 3. 

In Table 4, "X" indicates the applicability of the AM risk. The intent is to capture differences in 
processes (e.g., DED or L-PBF) or materials (e.g., metallic or polymer). The numerical score 
assigned for each row is binary:  either zero for Yes or the value listed in the “No” column. 


Table 4—Assessment Criteria for Additive Manufacturing Risk 
 Metallic Polymer   
  L-PBF DED L-PBF Score For   
Additive Manufacturing Risk       Yes No Score 
All surfaces and volumes can be reliably 
inspected, or the design permits adequate proof 
testing1 based on stress state? 
X X X 0 5  
As-built surface can be fully removed on all 
fatigue-critical surfaces2? X X  0 3  
Surfaces interfacing with support structures are 
fully accessible and the as-built surface 
removed? 
X X X 0 3  
Structural walls or protrusions are the 
equivalent of ≥8 trace, (e.g., melt pool, bead, 
scan path) widths in cross section? 
X  X 0 2  
Structural walls or protrusions are the 
equivalent of ≥2 trace, (e.g., melt pool, bead, 
scan path) widths in cross section? 
 X  0 2  
Critical regions of the part do not require 
support structure? X X X 0 2  
1 In the context of the assessment of AM risk, the adequacy of a proof test is determined by the degree to which the test 
meets its assigned objectives. For a workmanship proof test, at any given location in the part the proof test is considered 
adequate when the state of stress in the part during the proof test exceeds the state of stress in the part during operation by 
the required proof factor. If the proof test conditions do not fully replicate the operational environment, as is typically the 
case, the proof and operational stresses are compared using directional stress components with any needed corrections for 
environment. For the rare case of quantitative flaw screening by proof test as an anchor to fracture control requirements, 
the adequacy of the proof test is determined only by the ability of the applied proof test stress conditions to screen the 
critical initial flaw size for operation by causing failure, leak, or other clearly detectible damage to the part during the 
proof test. Just as in the workmanship proof test, the adequacy of a proof test for quantitative flaw screening is likely to 
vary throughout the part. Demonstrating the adequacy of a quantitative proof test is non-trivial and must be coordinated 
intently with the structures and fracture control communities. 
2 Fatigue-critical surfaces are locations where fatigue analysis and surface condition assumptions influence the outcome of 
the structural assessment. 

4.4 Quality Assurance 

 Quality Management Systems 

[AMR-13]  A QMS compliant to SAE AS9100, Quality Management Systems – Requirements 
for Aviation, Space, and Defense Organizations, or an alternate QMS approved by the CEO and 
NASA, documented or referenced in the AMCP, shall be in place for all entities involved in the 
design, production, and post-processing of AM hardware. 

[Rationale:  A QMS is required to ensure necessary process controls and mitigate risks 
associated with noncompliance. The AS9100 QMS requirement applies because an AM process 
is considered “complex” per NPD 8730.5, NASA Quality Assurance Program Policy, due to