NASA/TM—2014–218560

Nondestructive Evaluation of Additive 

Manufacturing

State-of-the-Discipline Report

Jess M. Waller

White Sands Test Facility, Las Cruces, New Mexico

Bradford H. Parker

Goddard Space Flight Center, Greenbelt, Maryland

Kenneth L. Hodges

Goddard Space Flight Center, Greenbelt, Maryland

Eric R. Burke

Langley Research Center, Hampton, Virginia

James L. Walker

Marshall Space Flight Center, Huntsville, Alabama

Prepared for

Edward R. Generazio

National Aeronautics and

Space Administration

Langley Research Center

Hampton, Virginia

November 2014
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NASA/TM—2014–218560

Jess M. Waller

White Sands Test Facility, Las Cruces, New Mexico

Bradford H. Parker

Goddard Space Flight Center, Greenbelt, Maryland

Kenneth L. Hodges

Goddard Space Flight Center, Greenbelt, Maryland

Eric R. Burke

Langley Research Center, Hampton, Virginia

James L. Walker

Marshall Space Flight Center, Huntsville, Alabama

Prepared for

Edward R. Generazio

National Aeronautics and

Space Administration

Langley Research Center

Hampton, Virginia

National Aeronautics and

Space Administration

White Sands Test Facility

Las Cruces, New Mexico

November 2014
Acknowledgements

Jose Carlos S. Abesamis, Jet Propulsion Laboratory, Pasadena, California

Kenneth C. Cheung, NASA Ames Research Center, Moffett Field, California

Ben Chin, NASA Ames Research Center, Moffett Field, California

Justin S. Jones, NASA Goddard Space Flight Center, Greenbelt, Maryland

Ajay Koshti, NASA Johnson Space Center, Houston, Texas

Christopher B. Kostyk, NASA Armstrong Flight Research Center, Palmdale, California

Richard E. Martin, NASA Glenn Research Center, Cleveland, Ohio

Lynn J. Rothschild, NASA Ames Research Center, Moffett Field, California

Richard W. Russell, NASA Kennedy Space Center, KSC, Florida

Regor L. Saulsberry, NASA White Sands Test Facility, Las Cruces, New Mexico

Miles Skow, NASA Kennedy Space Center, KSC, Florida

David M. Stanley, NASA Johnson Space Center, Houston, Texas

John A. Slotwinski, National Institute of Science and Technology, Gaithersburg, Maryland

Karen B. Taminger, NASA Langley Research Center, Hampton, Virginia

LaNetra C. Tate, NASA STMD, Washington, DC

Michael C. Waid, NASA Johnson Space Center, Houston, Texas

Available from:

NASA Langley Research Center

Hampton, VA 23681-2199

757-864-9658

National Aeronautics and

Space Administration

White Sands Test Facility

Las Cruces, New Mexico

November 2014
Contents

Section Page

Figures iii

Acronyms v

Executive Summary ii

1.0 Introduction 1

1.1 Background and Scope 1

1.2 NASA Additive Manufacturing Effort 2

Highlights of NASA’s Additive Manufacturing Work-to-Date 2

Relevance to the NASA Office of the Chief Technologist 2

NASA Nondestructive Working Group Role 2

NASA Space Technology and Mission Directorate Role 3

Relevance to the NASA Space Launch System 4

Relevance to the NASA Orion Program 5

Relevance to Commercial Space Partners 5

Armstrong Flight Research Center 5

Ames Research Center 6

Glenn Research Center 7

Goddard Space Flight Center 8

Jet Propulsion Laboratory 9

Johnson Space Center 9

Kennedy Space Center 10

Langley Research Center 11

Marshall Space Flight Center 12

White Sands Test Facility 13

1.3 America Makes 13

1.4 National Institute of Science and Technology Additive Manufacturing Effort 16

1.5 National Research Council Assessment of Space-Based Additive Manufacturing 17

1.6 Department of Defense Additive Manufacturing Effort 18

1.7 European Space Agency Additive Manufacturing Effort 19

2.0 Gap Analysis 20

2.1 Organizational Gaps 21

2.2 General Additive Manufacturing Gaps 21

Materials 21

Process and Equipment 21

Qualification and Certification 22

Technical Standards 22

Modeling and Simulation 23

i
2.3 Gaps in the NDE of Additively Manufactured Parts 23

Critical Defects 24

Complex Geometry 24

Physical Reference Standards 24

Inspection Procedures 25

In-Process Monitoring 25

Qualification and Certification 25

2.4 NASA NDE Data: Illustrative Examples 25

Penetrant Testing 27

Eddy Current Testing 29

Structured Light 29

Ultrasonic Testing 30

Near Infrared Camera Measurement for In Situ Process Monitoring 30

3.0 Recommendations 31

3.1 General Considerations for Additive Manufacturing 31

3.2 NDE-Specific Recommendations for Additive Manufacturing 31

References 33

ii
Figures

Figure Page

1 Selective laser melting equipment (left) and test specimens (right) used in the Marshall Space 

Flight Center Inconel 625 and Ti-6Al-4V material properties development task. 4

2 Test of a SuperDraco rocket engine at full power using an additively manufactured 

Inconel thrust chamber (NRC 2014). 5

3 Ames Research Center’s combining of synthetic biology and additive manufacturing to 

create 3D-structured arrays of cells that are bioengineered to secrete different materials in a 

specified three-dimensional pattern. 7

4 Hot-fire test at Glenn Research Center’s Rocket Combustion Laboratory of an Aerojet 

Rocketdyne liquid-oxygen/gaseous hydrogen RL-10 rocket injector assembly built 

using additive manufacturing. 8

5 Goddard Space Flight Center’s reentrant tube made by additive manufacturing for a cryogenic 

thermal switch for the ASTRO-H Adiabatic Demagnetization Refrigerator. 9

6 Jet Propulsion Laboratory’s metals parts made by additive manufacturing. 10

7 Conceptual regolith structures being fabricated on the Moon. 11

8 Langley Research Center’s modeling of temperature (left) and phase profile (right) during 

electron beam freeform fabrication processing. 11

9 Marshall Space Flight Center’s Pogo-Z physical reference standard used to verify and 

validate NDE measurements made on additively manufactured parts. 12

11 The relationship between the National Institute of Standards and Technology roadmap 

challenge areas for metal-based additive manufacturing and their funded programs. 16

12 A comparison of the technological gaps identified by the National Institute of Standards and 

Technology for ground based AM of metals, and the National Research Council for 

space-based AM (the latter was commissioned by NASA and the United States Air Force). 17

13 The Air Force Research Laboratory’s Additive Manufacturing Strategy emphasizes the 

development of this technology primarily for ground-based use for aircraft (NRC 2014). 19

14 Technology transition showing area of needed nondestructive evaluation development 

between Technology Readiness Levels 3 and 6 (Higginbotham 2014). 20

15 Computed tomography images of an indexing seam on the interior wall (left), and internal 

structure of a Ti-6Al-4V ASTRO-H adiabatic refrigerator component (right). 26

16 Computed tomography images of Pogo-Z baffles, RS-25/J2-X nozzles, injectors and 

valve bodies made by a direct metal laser sintering process 26

17 Photography (left) and computed tomography image (right) of a direct metal laser sintered 

aluminum gauge black 27

18 GRC computed tomography of an as-received Ti-6Al-4V tensile sample and following hot 

isostatic pressing, confirming closure of porosity. 27

19 Penetrant testing of a Ti-6Al-4V block under development for a liquid rocket gaseous 

hydrogen/liquid oxygen (GH2/LOX) injector (left) and a Pogo-Z baffle (right) showing high 

background noise due to as-manufactured surface roughness. 28

20 Optical photograph of variable background penetrant indications (left) and of penetrant 

indications from indexing seams on a Ti-6Al-4V ASTRO-H adiabatic refrigerator component 

(right). 28

21 Eddy current testing of a Pogo-Z baffle showing the ET probe in the standard set-up 

hole (left), probe in Pogo-Z bottom hole (center), and probe in Pogo-Z flange hole. 29

iii
22 Selective laser melting valve body showing smooth area on side (left) and the scratched 

area that were inspected by eddy current testing. 29

23 Structured light characterization of a Pogo-Z baffle. 30

24 Ultrasonic testing (UT) inspection of a 2219 aluminum electron-beam freeform fabrication 

part showing the area scanned (left) and the UT A- and B-scans (right). 30

iv
Acronyms

3D Three dimensional

ABS Acrylonitrile-butadiene-styrene

ADO Advanced Development Office

AFRC Armstrong Flight Research 

Center

AFRL U.S. Air Force Research 

Laboratory

AM Additive manufacturing

AMAZE Additive Manufacturing Aiming 

Towards Zero Waste and 

Efficient Production

ARC Ames Research Center

ASTM American Society of Testing 

and Materials

ATHLETE All-Terrain Hex-Limbed ExtraTerrestrial Explorer

AWS American Welding Society

COSMIAC Configurable Space 

Microsystems Innovations and 

Applications Center

CT Computed tomography

CTE Coefficient of thermal 

expansion

DMLS Direct metal laser sintering

DoD Department of Defense

EB Electron beam

EBF3 Electron-beam freeform 

fabrication

EBM Electron beam melting

ESA European Space Agency

ET Eddy current testing

EUS Exploration Upper Stage

FTIR Fourier transform infrared 

spectroscopy

GH2/LOX Gaseous hydrogen/liquid 

oxygen

GRC Glenn Research Center

GRCop84Glenn Research Copper 84

GSFC Goddard Space Flight Center

HIP Hot isostatic pressing

HQ Headquarters

IRAD Internal Research and 

Development

ISO International Standardization 

Organization

ISRU In-Source Resource Utilization

ISS International Space Station

JPL Jet Propulsion Laboratory

JSC Johnson Space Center

KSC Kennedy Space Center

LAMP Laser aided manufacturing 

process

LaRC Langley Research Center

LCUS Low Cost Upper Stage

LENS Laser engineered net-shaping

LS Laser sintering

MSFC Marshall Space Flight Center

MT Magnetic particle testing

NAMII National Additive 

Manufacturing Innovation 

Institute (America Makes)

NDE Nondestructive evaluation

NIAC NASA Institute for Advanced 

Concepts

NIR Near infrared

NIST National Institute of Science 

and Technology

NNWG NASA NDE Working Group

NRC National Research Council

OCT NASA Office of the Chief 

Technologist

OEM Original equipment 

manufacturer

ORNL Oak Ridge National Laboratory

OSMA Office of Safety and Mission 

Assurance

PAUT Phased array ultrasonic testing

PEKK poly(ether ketone ketone)

PMC Polymer matrix composite

PT Penetrant testing

RT Radiologic testing

SAE Society of Aerospace 

Engineers

SBIR Small Business Independent 

Research

SERS Surface enhanced Raman 

spectrometry

SLM Selective laser melting

SLS Space Launch System

SSTP Small Spacecraft Technology 

Program

STMD Space Technology Mission 

Directorate 

TM Technical Memorandum

TRL Technology readiness level

v
TTCP The Technical Cooperation 

Program

UT Ultrasonic testing

VCO Voluntary consensus 

organization

WSTF White Sands Test Facility

vi
Executive Summary

Given NASA's unique needs for highly customized spacecraft and instrument components, 

additive manufacturing (AM), or ‘three-dimensional (3D) printing,’ offers a compelling alternative 

to more traditional manufacturing approaches. NASA's work in AM should enable it to save time, 

expense, and mass. NASA also has an opportunity to push the envelope on how this 

technology is used both terrestrially and in zero gravity, and how manufacturing in space will 

ultimately occur. This Technical Memorandum (TM) presents current work being done both in 

and outside of NASA on AM, with a focus on nondestructive testing (NDE) of additively 

manufactured parts. Other AM disciplines not related to NDE are also highlighted in this 

Technical Memorandum (TM) for reference; however, this TM does not necessarily reflect or 

make recommendations for the current state-of-the-art for non-NDE disciplines .

While NASA is not leading the national AM effort, it is leveraging associated technology 

developed internally and externally for its unique needs. Plenary meetings and workshops 

attended by industry, academia, and government interests, including NASA, have identified 

NDE as a pervasive need for all aspects of AM. The impact of NDE on AM is crosscutting and 

spans materials, processing, quality assurance, testing, and modeling disciplines. Simply put, 

NDE techniques are needed before, during, and after the AM production process. 

This Memorandum highlights NASA’s AM accomplishments-to-date, first outlining the 

relevance of the AM effort to the NASA Office of the Chief Technologist, the NASA Space 

Technology Mission Directorate, the Space Launch System and Orion programs, and to NASA’s 

commercial space partners. The role the NASA NDE Working Group (NNWG) will play in 

integrating NDE into NASA’s AM effort is also discussed. Next, technology gaps impeding 

widespread adoption of AM by NASA are identified. Gaps are differentiated along lines of 

materials, process and equipment, consensus standards, and modeling and simulation, to focus 

effort according to specific technical discipline areas. Special attention is given to technology 

gaps in AM bridged by NDE. Both traditional and novel NDE approaches are discussed, and the 

inherent limitations and advantages of each. Based on this gap analysis, a series of 

recommendations are presented at the end of the document. Included are general 

recommendations to help unify the NASA’s AM effort across participating centers, and more 

specific NDE recommendations to focus NDE efforts. The latter recommendations are intended 

to guide Agency investments in NDE for AM and to insure the NNWG is properly positioned to 

support the use of additively manufactured parts in its ground and flight applications.

The major gaps and recommendations identified in this Memorandum are as follows:

• Lack of NDE and design allowables data specific to AM

o Fabricate physical reference standards to verify and validate NDE data 

o Augment current NDE dataset to increase agency experience and knowledge

o Apply NDE to understand feedstock-process scatter in design allowables data 

generation activities

• Low maturity finished part NDE

o Apply NDE to understand effect-of-defect and establish acceptance limits 

o Correlate process and destructive test data with NDE and develop processproperty recommendations

• Lack of in situ process monitoring

o Implement NDE in closed-loop process control to maximize part quality and 

consistency, and obtain ready-for-use certified parts directly after processing

o Develop better physics-based process models corroborated by NDE

o Use NDE to validate and confirm the effectiveness of post-processing

• Lack of Standards for NDE as applied to AM

o Develop NDE-based qualification and certification protocols for flight hardware

o Standardize NDE build records to serve as a permanent quality record

o NDE qualification of feedstock before build 

vii
1.0 Introduction

1.1 Background and Scope

This NASA Technical Memorandum (TM) briefly discusses the technical challenges and 

gaps associated with the fabrication of uniform and consistent additively manufactured parts 

and the certification and qualification of the parts. More specifically, this NASA TM addresses 

the nondestructive evaluation (NDE) methods that will play a crucial role in the verification of 

additively manufactured hardware having predictable and controlled properties.

Additive manufacturing (AM) has been around since 1987, with the introduction of 

stereolithography from 3D Systems, Inc. (Wohlers 2011). Additive manufacturing is the process 

of making three-dimensional (3D) objects (virtually any shape) from a digital model, and is

achieved using an additive process where successive layers of material are laid down to form 

different shapes. It is different from conventional machining methods, which rely on the removal 

of material by methods such as cutting or drilling, which are subtractive processes. Additive 

manufacturing has traditionally been viewed as a tool for rapid prototyping, but in recent years it 

has taken a substantial shift to the possibility of manufacturing high-quality complex metallic 

parts for infusion into primary structural hardware. The use of AM has great potential for 

producing high-value, complex, and individually customized parts, and could revolutionize 

manufacturing of aerospace parts by enabling novel ‘design to constraint’ products that could 

not be fabricated using conventional processes, by reducing waste (green manufacturing), by 

eliminating reliance on original equipment manufacturers (OEMs) for critical spares, and by 

extending the life of in-service parts through innovative repair methodologies (Harris 2011; 

NIST 2013a).

NASA is currently using AM methods to fabricate complex components that are either costprohibitive or, in some cases, impossible to fabricate using more traditional fabrication methods. 

The spaceflight certification and validation of these components by NDE is a high priority; 

however, no Agency-coordinated multidisciplinary effort currently exists to validate, certify, or 

qualify these parts made by AM processes. 

The path to the qualification and verification of parts made by AM is a universal concern 

echoed throughout government, industry and academia. Industry adoption of parts made by AM

is slow because of ambiguity in current validation and verification approaches, which are 

intimately tied to NDE capability. A key barrier for AM processes and equipment is that existing 

NDE methods and techniques are not optimized for AM processes, materials, or parts. 

Techniques are either non-existent or lacking for in situ process NDE, and post-process NDE of 

finished parts made by AM using conventional NDE techniques is challenging or still emerging 

(NIST 2013a).

Nondestructive evaluation challenges are crosscutting and span materials, fabrication, 

quality assurance, testing, and modeling disciplines. Accordingly, NDE represents a pervasive 

need for AM and impacts all aspects from design and materials, through part build, and on to 

inspection and certification. The time and cost to develop NDE methods is an ongoing concern, 

particularly when keeping up with rapidly shifting or emerging AM technologies. However, NDE 

is versatile and uniquely poised to accelerate broader and more effective use of AM by NASA.

NASA applications impacted by integration of NDE into NASA’s AM enterprises range from 

alleviating spares issues due to OEM obsolescence, to certification of flight hardware, to 

developing safer and more robust systems for space colonization and long duration space 

flights.

1
While this TM covers AM parts made from metals, polymers, ceramics and synbio1 materials 

using a variety of processes, most of discussion will focus on titanium and nickel alloys formed

by electron beam (EB) and laser sintering (LS) AM techniques.

1.2 NASA Additive Manufacturing Effort

Highlights of NASA’s Additive Manufacturing Work-to-Date 

Nearly all NASA Centers are engaged in AM, whether in terms of past or future effort. 

Summaries of AM efforts-to-date at each Center are given below. In some cases, activities in

different NASA programs overlap, illustrating the crosscutting nature of some priorities and 

gaps.

The Advanced Manufacturing Strategic Technology Development Project, which involves 

multiple centers and discipline areas, represents NASA on the National Advanced 

Manufacturing Initiative Committee (NRC 2014). The NASA Space Technology Mission 

Directorate (STMD) involvement and interests cross all Technology Readiness Levels (TRLs), 

from low-TRL activities, including the Materials Genome Initiative, the NASA Institute for 

Advanced Concepts (NIAC), research fellows, and Small Business Independent Research 

(SBIR) projects, to higher-TRL technology development and demonstration projects. Examples 

include the NIAC Printed Electronics Project at NASA Jet Propulsion Laboratory (JPL), the 

Small Spacecraft Technology Program (SSTP) Printable Spacecraft Project by the Configurable 

Space Microsystems Innovations and Applications Center (COSMIAC) at the University of New 

Mexico in collaboration with the University of Texas at El Paso, and the Made In Space 

Technology Demonstration project at Marshall Space Flight Center (MSFC) and Ames 

Research Center (ARC). For the AM of metals, technology development and demonstration 

efforts are being conducted primarily at MSFC, Langley Research Center (LaRC), and Glenn 

Research Center (GRC). The NASA Additive Manufacturing Working Group consists of 

participants from the engineering and technology services and products from all Centers. 

Despite the existence of this working group, the committee learned that AM researchers at 

different Centers were not fully aware of work going on at other Centers and determined that 

better Agency coordination and communication is needed.

Relevance to the NASA Office of the Chief Technologist 

The space technology roadmaps developed by the NASA Office of the Chief Technologist 

(OCT) highlight 14 critical technology areas (TA01 through TA14) (NASA 2013). The roadmaps 

target timelines where technology development is needed to enable space exploration, and one 

of those (TA12, Materials, Structures, Mechanical Systems and Manufacturing) specifically 

discusses advanced manufacturing, including AM. NASA’s strategy for AM can be summarized 

as migration of capabilities from terrestrial AM capabilities to using the International Space 

Station (ISS) for development and demonstration of space-based AM, and finally migration of 

AM capabilities to planetary surface platforms (NRC 2014). Development of NDE as applied to 

AM will follow a similar strategy.

NASA Nondestructive Working Group Role

The NASA Office of Safety and Mission Assurance (OSMA)-sponsored NASA NDE Working 

Group (NNWG) has recommended strengthening inter-Agency communication and 

collaboration within the NASA AM community by reaching out to center-specific organizations 

that are either directly or peripherally involved in the procurement, design, fabrication, materials 

1 Synbio, or synthetic biology, is the design and wholesale construction of new biological parts and systems; and the 

re-design of existing, natural biological systems for tailored purposes by integrating engineering and computerassisted design approaches with biological research.

2

 
characterization, testing, and inspection of AM hardware. A balanced and diverse set of NDE 

activities in research and applications to AM are being pursued. The role of the NNWG in this 

report is to identify AM technology gaps and where best to apply resources to close the gaps. 

As part of OSMA, the NNWG’s role specific to NDE of AM may be stated as follows:

• Establish and assure compliance of AM with NASA OSMA strategies, policies, and 

standards

• Improve NDE methodologies as applied to AM for risk identification and assessment, 

and provide recommendations for risk mitigation and acceptance

• Provide NDE analysis and recommendations specific to AM for critical Agency safety 

decisions

• Sponsor the innovation and rapid transfer of NDE methods applied to AM technologies, 

processes, and techniques to improve safety and reliability and reduce the cost of 

mission success

NASA Space Technology and Mission Directorate Role

The STMD is striving to invest in AM as one of several tools to manufacture components for 

complex ground equipment and the next generation additive tools that may one day be used to 

manufacture in space. The investment strategy is focused on exploring pathfinders in-house as 

well as working with industry to optimize and scale up processes and products that NASA will 

need for its missions.

Recent STMD investments in AM include a funded collaboration between GRC and Aerojet 

Rocketdyne to explore the fabrication and hot fire testing of AM engine components, specifically 

RL-10 injectors and thrust chamber assembly using Inconel 625 (injector) and copper (thrust 

chamber assembly); a collaboration between MSFC, GRC, and LaRC to use Glenn Research 

Copper 84 (GRCop-841

) in a selective laser melting (SLM) and electron-beam freeform 

fabrication (EBF3

) process to fabricate higher thrust engine systems (Low Cost Upper Stage

(LCUS) effort); Materials Genome Initiative effort to develop an intercenter effort including 

computational, experimental, and processing expertise; and support for the shared ISS 3D 

Printing in Zero-G effort. Each effort shares in innovative firsts –– from design innovation, to use 

of two AM processes on one part, to the first demonstration of AM in a micro-gravity 

environment. Also, STMD has invested in the use of AM to fabricate cubesats, and in lower TRL 

activities such as using AM to manufacture structures using regolith for scenarios such as heat 

shields and landing pads.

With AM and the ability to fabricate parts with complex geometries comes the need to 

properly inspect these parts. Within the STMD’s funded Materials Genome Initiative effort, test 

samples are being evaluated at the Oak Ridge National Laboratory (ORNL) Spallation Neutron 

Source to help understand material properties with greater sensitivity and higher resolution. In 

addition, within the LCUS effort conventional tools such as visual inspection, computed 

tomography (CT), and structured light scanning will be used to inspect the parts. For traditional 

manufacturing processes, parts could be inspected during the build; however, AM does not 

allow for inspection during build since a single piece is being fabricated. To overcome this 

obstacle, engineers at MSFC are working with the LCUS team to develop a method that would 

enable inspection during the build, to allow for real-time inspection to identify material flaws 

(impurities, voids, etc.). Although the development of these techniques is years away, there is 

an immediate need to accelerate their development.

1 GRCop-84 is a high-temperature copper alloy for high-heat-flux applications. It possesses excellent hightemperature strength, creep resistance and low-cycle fatigue up to 700 °C (1292 °F) along with low thermal 

expansion and good conductivity.

3

 
Relevance to the NASA Space Launch System 

To meet future 70- and 130-metric ton heavy-lift Space Launch System (SLS) needs, the 

MSFC Advanced Development Office (ADO) is pursuing advanced manufacturing strategies, 

including AM (Higginbotham 2014). Specific AM-related SLS ADO tasks include:

• Characterization of SLM materials for SLS engine components

• SLM integral valve/injector - valve proposal

• SLM integral valve/injector - injector proposal

• SLM integral valve/injector integrated hot-fire testing

• Hot-fire test of liquid oxygen and hydrogen additively manufactured SLM integral 

valve/injector applicable to the Exploration Upper Stage (EUS)

• Testing of additively manufactured turbomachinery hardware sized for the EUS

• Inconel 625 and Ti-6Al-4V material properties development

• CT sensitivity verification for SLM SLS engine components

• Real time infrared inspection of AM processes

The last effort, notably, applies NDE (infrared inspection) during the NDE process, and is 

synergistic with America Makes and NASA LaRC activities covered in this Memorandum. In 

cases where NDE is not called out, NDE still has relevance. For example, one of the key 

technology development areas for AM is to develop design allowables databases incorporating 

knowledge of 1) input materials; 2) process (EB, LS, etc.); and 3) test data (destructive and 

NDE) (Martukanitz 2014; NIST 2013a). Such design allowables databases are predicated on 

developing concise process-property recommendations, which in turn rely on optimized 

processes that have been validated using destructive and NDE test data. Therefore, it is 

conceivable NDE could play a vital role in NASA projects such as the MSFC ADO Inconel 625 

and Ti-6Al-4V material properties development task. Inconel 625 and Ti-6Al-4V parts made by 

the SLM process at MSFC (Figure 1) have been made under a range of process conditions by 

varying laser wattage, laser speed, and laser hatch spacing; and the properties have thus far 

been evaluated destructively (hardness, tensile). Use of NDE could further facilitate process 

optimization and generation of design allowables databases for NASA parts made by AM.

(Photographs courtesy of MSFC)

Figure 1 

Selective laser melting equipment (left) and test specimens (right) used in the Marshall Space 

Flight Center Inconel 625 and Ti-6Al-4V material properties development task.

4
Relevance to the NASA Orion Program

The Orion Project has inquired about AM, but it has not been adopted due to the low TRL of 

AM materials and processes and corresponding NDE. The Orion vehicle has a large titanium 

structure where near-net-shape AM pre-forms could possibly save significant material and 

machining costs. Additionally, it is envisioned that AM could be useful for complex life support 

and structural components.

Relevance to Commercial Space Partners 

NASA’s commercial space partners are pursuing opportunities to incorporate AM flight 

hardware into their spacecraft systems. The benefits of creating AM components for load path 

optimization, reduced weight, and improved performance are key metrics that make AM an 

attractive alternative to conventionally manufactured flight hardware. At this time, limited details 

are available for internal NASA dissemination; however, it is assumed that our commercial 

partners are encountering materials and NDE-related qualification and certification issues 

similar to NASA.

Recently, SpaceX unveiled the Dragon V2, its first manned spacecraft (Figure 2; 

SpaceX 2014). The Dragon V2 engines, referred to as SuperDraco engines, are more than 

160 times more powerful than the Draco engines found in the current version of Dragon, 

allowing them to produce 16,400 lbf thrust. In a departure from the norm, their combustion 

chambers are 3D-printed using direct metal laser sintering (DMLS).

Figure 2

Test of a SuperDraco rocket engine at full power using an 

additively manufactured Inconel thrust chamber (NRC 2014).

Armstrong Flight Research Center

The Armstrong Flight Research Center (AFRC) has three AM systems that produce 

nonstructural plastic acrylonitrile-butadiene-styrene (ABS) parts. Uses-to-date have been 

commonsensical and non-critical. Examples include fit checks, rapid prototyping/proof-ofconcept, and fabrication of unmanned system parts (autopilot mount, data cube enclosure, 

dead-man mount, and an air cleaner boss). Also, water tunnel parts have been made for ground 

support equipment.

5
Ames Research Center

The ARC recently created the ‘Space Shop,’ which is an advanced AM facility modeled after 

the ‘Fab Lab’ concept (NRC 2014, Chapter 2), created at the Massachusetts Institute of 

Technology Center for Bits and Atoms and co-located with the traditional machine and 

manufacturing shop. The Space Shop facility is made available as a mentored resource to all 

who have properly trained on the use and operation of the equipment. Other Centers have 

initiated or have plans for similar in-house, fab lab-type facilities. 

The ARC is using AM to develop multifunctional devices and structures for life support and 

radiation shielding. The research areas include carbon dioxide removal and/or oxygen

regenerating systems, supercapacitor devices and radiation resistant structures using both 

liquid and solid novel materials developed at ARC. In addition, ARC is examining the use of 

portable non-contact optical Surface Enhanced Raman Spectrometry (SERS) to monitor

materials properties during the AM processes. ARC has similar capabilities for high throughput 

chemical mapping or imaging (Raman, Fourier transform infrared spectroscopy (FTIR)) that 

have demonstrated value for the semiconductor industry for processing and disk head quality 

control.

These materials and processes are being studied in the context of synbio systems, but 

might not be considered synbio products themselves. Regarding advanced manufacturing NDE 

in general, ARC employs AM as part of its general engineering development resources, as well 

as a couple of projects that are focused on AM demonstrations in particular. For the former, the 

majority of the work is aimed at checking/confirming physical make-up, geometry and fit-checks. 

Thus far, NDE beyond basic inspection has not been a part of the process. Also, ARC is a 

partner with MSFC in the planned Fall 2014 ISS Made In Space, Inc. 3D Printing in Zero-G 

project (Knapp 2014). Another set of advanced manufacturing research projects that ARC is 

focused on is building block-based materials systems for aerospace structural applications.

In addition, ARC has a unique program in the AM of advanced biocomposites through the 

printing of synthetic biology altered cells which, subsequent to printing, secrete biomaterials that 

could not be made any other way. For example, the potential exists to print cells that have been 

engineered to produce products such as spider silk and rubber resulting in 3D composites. The 

cells could be fed primarily by the output of photosynthetic cells, thus allowing the production of 

materials off planet with virtually no inputs other than in situ-sourced water, radiation, carbon 

dioxide and nitrogen (Figure 3). This work is unique both in the Agency and the community at 

large, and thus is currently being supported by a NIAC Phase I award (Rothschild 2013; 

Gentry et al. 2014).

6
(Image courtesy of ARC)

Figure 3

Ames Research Center’s combining of synthetic biology and additive manufacturing to create 

3D-structured arrays of cells that are bioengineered to secrete different materials in a specified 

three-dimensional pattern.

Glenn Research Center

Additive manufacturing efforts at GRC consist of an Air Force-funded project with Aerojet 

Rocketdyne on liquid rocket gaseous hydrogen/liquid oxygen (GH2/LOX) injectors and other 

structural components for an RL-10 rocket (Figure 4) to demonstrate certification of SLM and 

electron beam melting (EBM) processes for highly critical rocket engine components, reduction 

of manufacturing lead time, and cost savings compared to traditional manufacturing processes. 

GRC is also testing Inconel®,1 625 injectors in this project. Nondestructive evaluation is being 

used in the testing of material characterization samples and the development of test plans for 

full-scale components. Specifically, CT is being performed on all samples and ultrasonic testing 

(UT) and penetrant testing (PT) are being used on machined surfaces. GRC is also working with 

rp+m to develop polymer and ceramic technologies for a ‘Fully Non-Metallic Gas Turbine 

Engine.’ A GRC Center Innovation Fund project is using an EB powder bed method to 

fabricate/join single crystal to polycrystal nickel-base disk and blade alloys, with the goal being 

to produce a hybrid turbine disk with a single crystal rim and polycrystalline bore. The build is 

being done at MSFC. Also in collaboration with MSFC, work is being done on the Materials 

Genome Effort involving microstructural/phase modeling of Inconel 718. GRC has a NASA 

STMD Game Changing project with MSFC, involving the building of a GRCop-84 combustion 

chamber liner. GRC is procuring the powder and doing the microstructural and mechanical 

characterization. GRC is supporting a Headquarters (HQ)/STMD Grand Challenge in AM in 

collaboration with America Makes (the National Additive Manufacturing Innovation Institute 

(NAMII)). Last, GRC is developing methods to additively manufacture ceramics and ceramic 

composite materials using pre-ceramic polymers.

1 Inconel® is a family of austenitic nickel-chromium-based superalloys and a registered trademark of Precision 

Castparts Corp., Portland, OR 97239.

7

 
(Photograph courtesy of GRC)

Figure 4

Hot-fire test at Glenn Research Center’s Rocket Combustion Laboratory of an

Aerojet Rocketdyne liquid-oxygen/gaseous hydrogen RL-10 rocket injector assembly 

built using additive manufacturing.

Goddard Space Flight Center

Goddard Space Flight Center (GSFC) has recognized the benefits of AM and has taken an 

approach of not attempting to drive or develop AM manufacturing technologies, but to use the 

technology that is being developed by industry and academia and to partner with these 

institutions to meet unique future mission requirements. These partnering activities have 

primarily been funded by the GSFC Internal Research and Development (IRAD) program. 

Examples of AM activities include the production of a reentrant tube for a cryogenic thermal 

switch in the ASTRO-H Adiabatic Demagnetization Refrigerator (Figure 5). This Ti-6Al-4V

(Ti 6-4) part is considered a flight spare. The cost of the AM part was an order of magnitude less 

than the conventionally machined and welded part and was produced in two weeks versus three 

months. The GSFC IRAD program funded a development of a DMLS Technology Guide. The

guide provides best practices for fabricating parts and evaluating basic mechanical properties 

for a wide range of AM materials produced by multiple outside vendors. The IRAD program is 

also funding AM production of light-weight low coefficient of thermal expansion optical benches 

for satellites and other instrument structures that demand dimensional stability using novel ironnickel alloys produced by DMLS. Other IRAD activities include spot shielding of sensitive 

electronic parts to space radiation using DMLS-printed Inconel 625. Additive manufactured 

production of proof-of-concept, fully integrated 3D printed telescopes to save mass, increase 

dimensional stability, and slash part counts has also been accomplished. GSFC has used 

DMLS to produce a modulated x-ray source for an instrument being considered for a possible 

flight on the ISS. The first GSFC flight of an AM part was a poly(ether ketone ketone) (PEKK)

battery case that flew on a sounding rocket. For all of these activities, the parts made by AM are 

being produced by outside vendors. These activities have allowed GSFC to better understand 

build challenges and where best to infuse the technology.

8
(Photograph courtesy of GSFC)

Figure 5

Goddard Space Flight Center’s reentrant tube made by

additive manufacturing for a cryogenic thermal switch 

for the ASTRO-H Adiabatic Demagnetization Refrigerator.

Jet Propulsion Laboratory

The JPL effort on AM involves work on amorphous metals created through medial sputtering 

onto a surface – a form of AM. Specific amorphous metal projects include fabrication of a mirror 

assembly including the isogrid backing, and the production of a revolutionary new material for a 

gearbox application. Other AM projects at JPL include the use of AM to fabricate prototype 

gradient Ti-6Al-4V/niobium rocket nozzles, prototype gradient stainless steel/Inconel engine 

valves, prototype low coefficient of thermal expansion (CTE) inserts for composites, and a 

titanium mirror flexure made of deposited titanium on a titanium plate (Figure 6). Also, JPL 

developed the robotic platform concept known as the All-Terrain Hex-Limbed Extra-Terrestrial 

Explorer (ATHLETE) for In-Source Resource Utilization (ISRU)-based robotic construction 

technologies (Khoshnevis et al. 2005).

Johnson Space Center 

Johnson Space Center (JSC) has pursued fabrication and qualification of EBF3 and laser 

engineered net-shaping (LENS) components for manned space flight applications, including inspace manufacturing. Titanium, aluminum and steel EBF3 process development and material 

properties test samples as well as flight-like extravehicular activity tool components, all 

deposited at LaRC, have been inspected in both the as-deposited and final machined 

conditions. Nondestructive evaluation methods applied to the EBF3 samples and parts include xray digital radiologic testing (RT) and CT, conventional UT and phased array ultrasonic testing 

(PAUT), and eddy current testing (ET). Complex conceptual engine components have been 

manufactured at JSC from Inconel, titanium, and steel using the LENS process. Selected 

Inconel LENS components have been inspected using x-ray CT.

9
(Images Courtesy of NASA JPL)

Figure 6

Jet Propulsion Laboratory’s metals parts 

made by additive manufacturing.

Kennedy Space Center 

Work in the Kennedy Space Center (KSC) Surface Systems Office and at the University of 

Southern California under two NIAC awards (Khoshnevis 2011; Khoshnevis 2012) have shown 

promising results with regolith materials for in situ heat shields, bricks, landing/launch pads, 

berms, roads, and other structures that could be fabricated using regolith that is sintered or 

mixed with a polymer binder (Figure 7). The technical goals and objectives are to prove the 

feasibility of AM construction using planetary regolith. Future KSC effort will explore the use of 

NDE to show that regolith structures have structural integrity and practical applications in space 

exploration. 

10
Figure 7

Conceptual regolith structures being fabricated on the Moon.

(Khoshnevis 2005, 2011 and 2012).

Langley Research Center 

Langley Research Center has developed the EBF3 and LENS processes for fabrication of 

metallic parts for aerospace and space applications. More specifically, EBF3 has been used to 

fabricate functionally graded unitized structures with different alloys and integrated damage 

tolerance to replace heavier conventional structures. Examples of unitized structures include 

contoured stiffeners, acoustically tailored fuselage structures, aeroelastically tailored wing 

structures, layered aircraft structures, and functionally graded stiffeners (e.g., EBF3 deposited 

stiffeners onto single-piece cryogenic tank barrel sections of launch vehicle structures). Also, 

LaRC is developing near infrared (NIR) camera inspection technologies for in situ process 

monitoring of melt pool temperatures, and has successfully imaged the melt pool and 

solidification areas during EBF3 processing. In addition, LaRC is applying multi-physics 

modeling of laser-direct powder feed systems (LENS, Laser Aided Manufacturing Process 

(LAMP)) and electron beam-wire feed systems (EBF3

) (Figure 8). Last, LaRC has successfully 

conducted a KC-135 parabolic flight demonstration to show the feasibility of advanced near-net 

shape processing in microgravity. 

(Image courtesy of LaRC)

Figure 8

Langley Research Center’s modeling of temperature (left) and phase profile (right) 

during electron beam freeform fabrication processing.

11
Marshall Space Flight Center 

Past work at MSFC includes an ADO-funded task, titled Characterization of Direct Metal 

Laser Sintering Materials for SLS (Space Launch System) Engine Components, to investigate 

applications of NDE to materials used in AM, methods for defect standard formation, and 

effects-of-defects on material properties. Inspection of dozens of AM components has been 

conducted, primarily with CT, but also with ET, PT, RT, and UT, to help verify their integrity and 

to evaluate the usefulness of these methods on structural components. Some of the major 

components covered are potential items for the RS-25, J2-X, and Morpheus lander including 

Pogo-Z baffles, nozzles, injectors, and valve bodies. These ranged in size from a few inches to 

over 12 inches across and covered several Inconel, aluminum, stainless steel and copper 

alloys. Computed tomography gauge blocks were designed and fabricated to help assess the 

dimensional accuracy of CT and compare both AM and conventionally machined parts. Finally, 

an NDE reference standard was designed for the Pogo-Z baffle to help determine inspection 

characteristics of various NDE methods, in particular CT (Figure 9).

Present work includes performing CT analysis of the aforementioned gauge blocks and 

fabrication and testing of the Pogo-Z reference standard. The NDE team is actively researching 

micro-focus CT methods and working with several vendors to test these out on typical engine 

parts. The team is looking to possibly procure a micro-focus CT system. There is an effort to 

write a standard/specification to certify powder bed fusion manufactured parts for flight. Lastly, 

MSFC is working in collaboration with ARC in the Fall 2014 ISS Made In Space, Inc. 3D Printing 

in Zero-G project.

(Images courtesy of MSFC)

Figure 9

Marshall Space Flight Center’s Pogo-Z physical reference standard used to verify and validate 

NDE measurements made on additively manufactured parts.

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White Sands Test Facility

White Sands Test Facility (WSTF) has one system for making nonstructural ABS parts. 

Uses-to-date have focused on fabrication of mock-up components, piece parts for system fit

checks, brackets and fixtures for test setups, and complex components for visual representation 

when machining flight-like prototypes. WSTF also held a kick-off meeting in January 2014 with

American Society of Testing and Materials (ASTM) International Committees E071 on 

Nondestructive Testing and F422 on Additive Manufacturing Technologies, and gained support 

to develop voluntary consensus organization (VCO) standards for NDE of AM (Figure 10). This 

approach will allow NDE and AM experts drawn from industry, academia, and other government 

agencies to be leveraged to develop standards having direct value to NASA. Also, WSTF sits on 

ASTM E07 and F42 and is part of an F42 collaboration team for an ASTM draft Guide for 

measuring the mechanical properties of parts made by AM (ASTM 2014a). Additionally, WSTF 

is leading an ASTM E07 effort to develop an ASTM draft Guide for NDE of parts made by AM 

(ASTM 2014b). Previously, WSTF has analyzed Optomec test specimens consisting of LENSdeposited nickel on aluminum and titanium alloy substrates for use as flightweight combustionresistant components for service in enriched oxygen environments.

1.3 America Makes

America Makes, also known as NAMII, is a publicly run consortium composed of companies, 

universities, non-profit organizations, and government agencies. America Makes funds two tiers 

of projects: Project Call 1 and Project Call 2. Project Call 1 efforts focus on maturing 

technologies between TRL 4 (component and/or breadboard validated in a laboratory) and 

TRL 5 (component and/or breadboard validated in a relevant environment). Project Call 2 efforts 

focus on maturing technologies between TRL 8 (actual system completed and qualified through 

test and demonstration) and TRL 9 (actual application of technology is in its final form–

technology proven through successful operations). Also, Project Call 2 efforts allocate funding 

devoted to 1) design; 2) materials; 3) processes and equipment; 4) qualification and 

certification; and 5) knowledgebase development.

Three NDE-related efforts are currently being funded by America Makes (Macy 2014). More 

specifically, one Project Call 1 (launched April 2013) and two Project Call 2 efforts (announced 

January 2014) were identified (Table 1). Possible overlap with NASA NDE efforts is noted 

where applicable.

Of interest also are two Project Call 1 efforts NASA has co-funded that pertain to AM but do 

not involve NDE at this point (Table 2).

1 American Society of Testing and Materials, Committee E07 on Nondestructive Testing, 

astm.org/COMMITTEE/E07.htm. 2 American Society of Testing and Materials, Committee F42 on Additive Manufacturing Technologies, 

astm.org/COMMITTEE/F42.htm

13

 
Figure 10

Timeline showing past (1-6) and current (7-10) White Sands Test Facility-led ASTM E07 standardization efforts related to 

nondestructive evaluation (NDE), and planned (11) NDE of additively manufactured parts ASTM E07-F42 standardization effort.

14
Table 1

America Makes-Funded NDE-related Projects

Project Call 1: TRL 4-5 

(possible overlap with NASA Langley Research Center’s Nondestructive Evaluation (NDE) effort)

Targeted Technology Area: In situ process monitoring NDE

Title Lead Organizationa and Team Key Outcomes

Thermal Imaging for Process 

Monitoring and Control of Additive 

Manufacturing

Penn State University, Stratonics, 

Sciaky Inc., Optomec, CMU, WSU, 

Aero Energy Ind.

Thermal imaging for process 

monitoring and control of electron 

beam direct manufacturing and 

laser engineered net shaping 

(LENS) additive manufacturing (AM)

Project Call 2: TRL 8-9 

(possible overlap with NASA Johnson Space Center’s NDE effort):

Targeted Technology Area: Qualification and Certification using NDE

Lead Organization and Team Short Description

EWI, Lockheed Martin, Sciaky Inc. Improve ability to ultrasonically inspect titanium alloy 

components through advancement in process 

parameters and inspection techniques

Project Call 2: TRL 8-9 

(general relevance):

Targeted Technology Area: NDE Methods Knowledgebase Development

Lead Organization and Team Short Description

Northrop Grumman Aerospace Systems, CalRAM, 

Inc., Concurrent Technologies Corp., General Electric

(ge.com), Robert C. Byrd Institute

Electron Beam Melted Ti-6Al-4V Component 

Fabrication, Design Allowables, and NDE methods

a Lead Organization appears in boldface type. 

Table 2

America Makes/NASA AM-Related Projects

Project Call 1: TRL 4-5 (General AM, co-funded by NASA):

Targeted Technology Area: General AM

Title Lead Organizationa and Team Key Outcomes

Maturation of High-Temperature 

Selective Laser Sintering 

Technologies and Infrastructure

Northrop Grumman, Oxford 

Performance Materials, Arkema, AST2

Development of lower-cost, hightemperature selective laser sintering

process for making air and space 

vehicle components (Air 

Force/Navy/NASA) and other 

commercial applications; ability to 

recycle

Maturation of Fused Depositing 

Modeling (FDM) Component 

Manufacturing

rp+m, Stratasys, University of Dayton 

Research Institute, Boeing, GE 

Aviation, Lockheed Martin, Northrop 

Grumman

Design guide; critical materials and 

processing data; and machine, 

materials, part and process 

certification for ULTEMTM 9085 – high 

temp aerospace parts (Air Force,

NASA – strong collaboration)

a Lead Organization appears in boldface type.

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1.4 National Institute of Science and Technology Additive Manufacturing Effort

Following the roadmap exercise completed by the National Institute of Science and 

Technology (NIST) in May 2013 (NIST 2013a), the NIST Engineering Laboratory in 

Gaithersburg, MD initiated the Measurement Science for Additive Manufacturing Program. This 

five-year program, which started October 1, 2013, has four thrust areas that closely match the 

technology challenges identified in the roadmap exercise. The roadmap technology challenge 

areas and the linked funded programs are shown in Figure 11.

Figure 11

The relationship between the National Institute of Standards and Technology roadmap 

challenge areas for metal-based additive manufacturing and their funded programs.

The NIST roadmap addressed finished-part NDE as an element in the Process and 

Equipment challenge area. The action plan for this area called for the evaluation and 

optimization of existing post-process NDE techniques. However, the corresponding funded 

program focuses on developing in-process NDE sensing methods that are applied during 

processing. Based on the description found on the NIST website, the Real-Time Control of AM 

Processes program (funded) is primarily working to develop sensing techniques to monitor melt 

pool temperature distribution and geometry, dimension of layers and the detection of defects. 

The program has the goal of developing high speed imaging techniques for detecting defects 

such as cracks, delaminations (weak layers) and voids in real time.

The Qualification for AM Materials, Processes and Parts program (funded) suggests the 

program will focus on testing protocols for qualification and the generation of materials property 

databases through round robin testing (NIST 2013b). Though NDE may be employed in this 

activity, it is not emphasized in the program description.

16
1.5 National Research Council Assessment of Space-Based Additive 

Manufacturing

NASA, the Air Force Space Command, and the Air Force Research Laboratory (AFRL) 

asked the National Research Council (NRC) to conduct a study of the prospects for the use of 

AM in space. In response, the NRC established the Committee on Space-Based Additive 

Manufacturing (NRC 2014) with the following focus areas:

• Assess the current state of AM in the United States and worldwide (especially as relates 

to small satellites or respective subassemblies)

• Characterize the future applications of AM in space

• Discuss the feasibility of space-based AM of space hardware for missions of relevance 

to NASA

• Identify the technology gaps for use of AM in space

• Assess the implications that a space-based AM capability would have on launch 

requirements

The NRC report lists the current technology gaps pertaining to space-based AM that 

confront NASA and the Air Force. While the gaps identified by the NRC mirror the ones 

identified by the NIST (NIST 2013), namely, Materials and Processes; Equipment; Certification 

and Qualification; and Modeling and Simulation (Figure 11), the gaps are more specific to space 

hardware and the space environment. Regardless, the gaps identified by the NRC effectively 

bar wider use of AM, even in ground-based environments, and must be resolved first before AM

can be used in space-based environments. A comparison of the technological gaps identified by 

NIST and the NRC is shown in Figure 12. Similar to the findings delineated in the NIST 

roadmap, NDE has relevance for evaluating part precision, finished part certification, and 

process control, for example.

Figure 12

A comparison of the technological gaps identified by the National Institute of Standards and 

Technology for ground based AM of metals, and the National Research Council for spacebased AM (the latter was commissioned by NASA and the United States Air Force).

17
The NRC report also provides a possible roadmap for NASA space-based AM. Four key 

factors that will likely have a strong influence on the use of AM in NASA space applications

were identified:

• The degree to which AM will provide technical and programmatic benefits (reduced 

mass, better volumetric efficiencies, increased design flexibility, better cost and schedule 

efficiencies)

• The degree to which AM production of space hardware (e.g., cubesats) can be 

automated and best practices shared

• The availability of resources and infrastructure to insure the effective use of AM systems 

aboard the ISS (the rate of production of artifacts, the cost effectiveness of the 

production system, etc.) 

• The degree to which space-based (or ground-based) AM technologies and products can 

be validated as to their utility, efficacy, and applicability.

1.6 Department of Defense Additive Manufacturing Effort

The NNWG has made contacts with key Department of Defense (DoD) personnel involved 

in AM and NDE through The Technical Cooperation Program (TTCP). A joint meeting of TTCP 

technical panels TP1 (Metals and Ceramics) and TP5 (Materials State Awareness and

Nondestructive Evaluation) was held February 27, 2014 in Arlington, Virginia. TP1 oversees AM

efforts within the TTCP member countries (United States, Canada, United Kingdom, Australia, 

New Zealand). The main purpose of the workshop was to learn about the state-of-the-art of AM, 

and to identify key challenge areas related to NDE as applied to AM across the TTCP countries 

and to provide participant panel members with a forum to explore and propose new study and/or 

operating assignments.

More recently, the NRC has released its findings for both NASA and the U. S. Air Force on 

the feasibility of space-based AM (NRC 2014). One of the key findings as relates to the U. S. Air 

Force was that there is at present a lack of knowledge to credibly determine whether or not 

development of an Air Force-specific, space-based AM production facility would achieve its 

expected benefit. Given that such a fabrication center would be highly complex and expensive, 

a detailed system assessment and cost-benefit analysis might be advisable.

The AFRL Materials and Manufacturing Directorate has a significant portfolio of work in AM.

While AFRL AM work is extensive, it is, to date, largely aimed at aeronautical/aircraft 

applications (Figure 13). It is instructive to note that the AFRL and other DoD Branches are 

actively working on applying NDE to AM. Similar to the hurdles that NASA must surmount, 

significant additional research will be required by AFRL, for example, to fully close all the gaps 

to successfully implement AM either in space or on the ground for space applications. The 

NNWG is actively seeking collaboration that focuses on application of NDE to AM with the AFRL 

and other DoD Branches.

18
(NRC 2014)

Figure 13

The Air Force Research Laboratory’s Additive Manufacturing Strategy emphasizes the 

development of this technology primarily for ground-based use for aircraft (NRC 2014).

1.7 European Space Agency Additive Manufacturing Effort

The European Space Agency (ESA) is using AM to build high-quality, intricate shapes with 

improved cost savings and reduced waste generation. The ESA’s AM effort is part of its Clean 

Space initiative, which seeks to apply innovative technologies to reduce the environmental 

impacts of the space industry (ESA 2014a). Both metallic and polymeric parts have been made 

and are being considered. For example, ESA’s AMAZE (Additive Manufacturing Aiming 

Towards Zero Waste and Efficient Production) project currently involves 28 industrial partners 

across Europe and focuses on metals-based AM (ESA 2014b). The goal of the 5-year AMAZE 

project is to develop the first complete European Union autonomous supply chain for AM by 

2017.

The ESA’s AM efforts include developing AM processes that can be used to build lunar 

bases in the future (ESA 2014c). The ESA has also overseen the successful manufacturing of 

high TRL (TRL 9) reduced mass titanium satellite parts (Ghidini 2011a). Propulsion parts 

(injectors, chambers, nozzles, monolithic thrusters), electrical hardware, and design optimized 

load-bearing mechanical hardware are also being made (Ghidini 2011b). Despite these 

successes, ESA has identified three challenges pertaining to AM that still remain open:

• Design challenges (better design tools and rules are needed)

• Manufacturing challenges (better manufacturing protocols are needed to 

guarantee the accuracy, reproducibility, and reliability of parts made by AM from 

raw materials to end product)

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• Qualification and certification challenges (process verification methodologies, 

such as those involving NDE, are needed)

Although initial contacts have been made between the NNWG and ESA, the NNWG has not 

penetrated the NDE-specific ESA effort other than confirming that the ESA NDE effort is 

currently focusing on CT.

2.0 Gap Analysis

The intent of the gap analysis is to identify the challenges (i.e., gaps) that prevent the 

infusion of AM into NASA and Commercial Space applications and to identify where NDE can 

play a role in overcoming these challenges. This TM will review specific gaps in the NDE 

knowledge base and readiness within the Agency, and make recommendations for Agency 

investments in NDE as it applies to AM, to ensure that the NDE community is properly 

positioned to support the use of parts made by AM in flight applications.

In 2012, NIST conducted a roadmap exercise for metal AM that focused on measurement 

science challenges (NIST 2013). Five of the workshop participants were representatives from 

NASA LaRC, GSFC and MSFC. The NIST workshop report provides a comprehensive 

breakdown of AM technology challenges that must be addressed to achieve widespread use of 

additive processes for direct part production, and to realize the potential economic benefits. 

Gaps identified include measurement methods, performance metrics, and standards to evaluate 

fundamental AM process characteristics, improve the performance of AM equipment, improve 

the accuracy of parts made by AM, and increase confidence in the mechanical properties of 

parts fabricated using these systems. These gaps are grouped into the following challenge 

areas: Materials; Process and Equipment; Qualification and Certification; Standards; and 

Modeling. Examination of these challenge areas shows that NDE is a crosscutting technology 

that will play a key role in closing the gaps in each area. 

Widespread use of AM in NASA will require developing NDE methods that span the gap 

between TRL 3 (analytical and experimental critical function and/or characteristic proof-ofconcept) and TRL 6 (system/subsystem model or prototype demonstration in a relevant 

environment) (Figure 14).

Figure 14

Technology transition showing area of needed nondestructive evaluation development 

between Technology Readiness Levels 3 and 6 (Higginbotham 2014).

20
2.1 Organizational Gaps

In addition to these technology-related challenge areas, the NASA NDE community faces an 

organizational challenge since the AM efforts are spread across the Agency. Much of the NASA 

effort-to-date has been delegated to individual Centers along the lines of core competencies. 

These efforts have reached a stage of development where sufficient overlap exists to warrant

greater cooperation and coordination between the NASA Centers.

From an NDE perspective, this TM is unique since the mechanism for coordination between 

NASA Centers was non-existent before January 2014, which was when the NASA NDE 

community began to discuss coordinating efforts and initiated the writing of this TM. The TM is 

one of the primary mechanisms for coordination. The intention is that this NASA TM be used as 

a guide or catalyst for greater future coordination between the NASA Centers to improve 

technical and scientific synergy, reduce redundancy, and maximize efficient utilization of NASA 

resources and investments.

The need for greater coordination reiterates one of the key findings in the NRC report 

(NRC 2014) that often occurs in emerging technologies such as AM: a lack of coordinated effort 

outside of the driving organization’s primary needs (STMD is highlighted). The lack of 

coordination could be due to several factors such as 1) disconnects between technology 

possibilities and actual end-user applications; 2) linkage between manufacturing and end-user 

applications; and 3) no overarching mechanism “to facilitate communication, discussion, and 

collaboration” on space- and ground-based AM technologies agency wide. From the NDE 

perspective, NASA would benefit from coordination of its many and diverse NDE efforts related 

to AM. Similarly, NASA’s full use and application of NDE as related to AM could be made more 

efficient and effective if there were a stronger associative link between NDE method developers 

and end users. Benefits may include improved efficiency and complexity, and cost reductions.

2.2 General Additive Manufacturing Gaps

Materials

Design Allowables – There is a lack of documented and shared fracture toughness, fatigue 

strength and other key properties for AM metals. The challenge is compounded by the potential 

for machine-to-machine variations, feed stock variations, and the large processing parameter 

space inherent in AM. Nondestructive evaluation can be useful in characterizing test specimens 

and has the potential to provide insight into the effect-of-defects on properties. The need for a 

centrally located, non-proprietary database which contains design allowables data and other 

pertinent information has been expressed by industry, academia, and various government 

agencies (Martukanitz 2014). The three aspects of the design allowables generation activity are

knowledge of 1) input materials; 2) manufacturing platform (i.e., EB or LS); and 3) test protocol. 

This is a challenge or gap area where NDE can help close the gap.

Feed Stock – NIST has taken a lead in testing and characterizing powder and wire feed 

stock materials, which not only need to be consistent but also need to be optimized for AM 

processes. The techniques used to measure particle size, shape, and chemical composition are 

mature. Once feed stock characteristics are optimized, standards or specifications need to be 

developed to insure consistent feed stock.

Process and Equipment

In Situ Process Control –It is recognized that in situ process monitoring is a requirement for 

producing consistent parts made by AM; however, current AM machines are not equipped for 

closed-loop feedback systems. Once it is understood what in situ measurements are needed, 

sensors deigned for the AM build environment must be developed and employed for closed-loop 

21
feedback. Thermal imaging to monitor the weld pool temperature, optical imaging to measure 

shape and distortion during the build, and techniques for addressing residual stress, 

homogeneity, and defects are areas for development. 

Residual Stress – Residual stress is an inherent problem with parts made by AM and can 

result in part distortion as well as part failure due to cracking. As a consequence, AM production 

protocols need to be optimized to reduce residual stress. Oak Ridge National Laboratory is 

leading the way with neutron tomography imaging for mapping residual stress. More affordable 

solutions and an increased knowledge base are needed in order to reduce residual stress.

Post Processing – Protocols are needed for post processes such as hot isostatic pressing 

(HIP), heat treating, and shot peening. Nondestructive evaluation can play a role in helping 

understand the effect of these processes on final part properties and consistency.

NDE – The NIST report identified the need for optimizing and adapting NDE for parts made 

by AM (NIST 2013b). It is recognized that CT is a key technique for parts with complex 

geometries, and the challenge of implementation of this technique is the availability of affordable 

high power and high resolution systems. Thermography was also identified as a key capability 

for in situ process monitoring. NASA has world-class CT and thermography capabilities 

dispersed across the Agency. What lacks is a knowledge base of AM part inspections, which is 

needed to understand defect types and their detectability.

In-Space Processing – This is a challenge area, unique to NASA, which will require the 

development of potentially unique equipment and processing protocols. Advances leading to 

closure of the many equipment and processing challenges for industrial AM manufacturing will 

help drive the TRL of in-space processing.

Qualification and Certification

Guidelines – There is a recognized lack of guidelines for how to qualify and certify AM 

processes as well as parts made by AM. The gap in process certification and qualification 

guidelines is complicated by the wide variety of machine types and the vast processing 

parameter space.

Technical Standards

Input Material and Finished Part Standards – No technical or voluntary consensus 

organization standards exist for measuring the size, shape, chemistry, or microstructural 

homogeneity/heterogeneity of input material powders, spools, etc., and very few standards exist 

for measuring the mechanical or physical properties of finished parts (ASTM 2014a). Standards 

for the 1) preparation of measurement test pieces and 2) creating, reporting, and storing AM test 

data also do not exist. To address this gap, such standards will be developed under the 

jurisdiction of ASTM Committee F42.

Equipment Standards – Standards are particularly critical to ensure machine-to-machine 

consistency and routine or periodic calibration to ensure optimal operation and performance, 

and thus, part quality. To address this gap, AM equipment standards will be developed under 

the jurisdiction of ASTM Committee F42.

Standard Guidelines and Methods for Qualification and Certification – Standard guidelines 

for qualification and certification are lacking. Challenges include the ability to define the type and 

quantity of guidelines and wide variations in machines and end users. ASTM qualification and 

certification guidelines for AM machine components are currently lacking or inadequate. To 

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address this gap, uniform standards are being developed along with a taxonomy that 

encompasses all AM methods and is flexible to accommodate new technologies as they 

emerge.

Standards for Round-Robin Build and Material Testing – No documented standards and 

protocols exist for round-robin build and materials testing for AM. To address this gap, a set of 

protocols are being created for round-robin testing, beginning with a single source powder and 

going through part production, process, build, and inspection using, for example, composition 

(scanning electron microscope/energy dispersive spectrometer and x-ray diffraction), size 

measurement, morphology, and flow-ability/sifting mesh.

Miscellaneous Voluntary Consensus Organizations – In addition to AM-related standards 

developed by ASTM Committee F42, standards developed by other voluntary consensus 

standards organizations such as SAE (Society of Aerospace Engineers), AWS (American 

Welding Society) and ISO (International Standardization Organization) are also being surveyed 

and monitored. For example, SAE has a handful of standards on an alternative ion fusion AM 

method, construction of cubesats using AM, and fast, high-volume AM processes. ISO has 

recently adopted standards on terminology, data processing, uniform file format, process 

categories, feedstock, etc., that parallel ASTM Committee F42’s efforts.

Relevant NASA Standards – AM parts used in NASA ground applications and non-human 

rated and human rated spacecraft must meet several NASA standards. The first standard 

(NASA-STD-6016) sets detailed Materials and Process requirements for spacecraft (NASA 

2008a). This standard is currently being revised to include guidance on qualification of AM 

processes and parts made by AM. The second standard (NASA-STD-5009) sets NDE 

inspection requirements for fracture-critical metallic components (NASA 2008b). A third 

standard (NASA-STD-5001) provides uniform engineering and technical requirements for 

processes, procedures, practices for design, and factors of safety for spaceflight hardware 

(NASA 2014), Any general standards for parts made by AM will adhere to and defer to these 

overarching NASA requirements documents.

Modeling and Simulation

Physics Based Predictive Models – Again due to the rapid pace of change in AM, there is a 

lack of physics-based predictive models for the various AM processes. The models need to be 

able to predict residual stress, grain size distribution, spatial homogeneity, material properties,

and defects. Nondestructive evaluation will play a key role in validating these models, which will 

be fundamental in process optimization.

In situ Sensors – The lack of in situ sensor capabilities is also hindering model validation. 

There is a clear need to know the dynamics of weld pool temperature being achieved in a build 

process in order to predict the end product quality.

2.3 Gaps in the NDE of Additively Manufactured Parts

Challenges for NDE of AM include: complex part geometry, a lack of defined critical defect 

types and sizes, a lack of physical NDE reference standards, a lack of written inspection 

procedures tailored for AM processes, and a lack of probability-of-detection data. In addition, 

there is a recognized need to develop in-process monitoring techniques to inspect parts during 

the build process.

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Critical Defects 

While there may be new or unknown defect types in metal parts made by AM, current NASA 

fracture mechanics and control requirements will still rely on NASGRO®1 analysis to provide 

critical flaw size and orientation for any part with the appropriate geometry, stress, and material 

property inputs. Typically, fracture analysts use standard NDE flaw sizes defined by NASASTD-5009 for assessments, unless a smaller critical crack size is required, in which case 

special NDE methods are used. Fracture mechanics analysts need NDE input to ensure that 

flaws larger than the critical initial flaw size are screened at some defined probability of 

detection and confidence level. Therefore, instead of defining a critical crack for a part made by 

AM, it is probably better to validate NDE techniques that are known to not miss standard-sized 

flaws at a specified probability and confidence level. A possible complicating factor is that the 

assumption of a single rogue flaw detected by NDE methods developed using wellcharacterized physical reference standards may not apply for parts made by AM. In AM, wellcharacterized physical reference standards are still being developed. Also, finished AM parts 

typically have greater ranges of porosity and lack of fusion, with defects distributed throughout 

the part, rendering sizing of relevant flaws or assumption of a single rogue flaw difficult.

The above factors make identification and quantification difficult for the relevant flaw types 

and sizes of defects that must be detected by NDE for parts made by AM. Furthermore, there is 

often industry ambiguity in defining what constitutes a critical defect in a complex-geometry AM 

part. This information will only become available once AM processes have matured and after 

exhaustive effect-of-defect studies have been completed, which is still years away from being 

finished. A further complication is presented by the numerous AM processes and the complex 

processing parameter space for AM. The situation is analogous to the inspection evolution that 

occurred during the early years of polymer matrix composite (PMC) development and 

implementation, during which NDE inspection criteria were often driven by what could be 

reasonably detected and not by what needed to be detected. These challenges can set the 

stage for a dangerous scenario where true critical defect types and sizes are missed in an AM

part inspection because of inexperience and unfamiliarity with the true failure modes of the 

materials.

Complex Geometry

The AM process is most suited for parts with complex geometries, and these geometries 

present a challenge for conventional NDE methods like UT, ET and even RT. Likewise, many 

parts made by AM have internal structure that may not be accessible for the less geometrysensitive methods such as PT and magnetic particle testing (MT). Hence, the most promising 

technique for complex geometry parts appears to be x-ray CT. However, CT has limitations. For 

example, CT is not well suited for crack detection, and is time consuming both for data 

acquisition and data analysis (slice by slice visual interpretation). CT sensitivity will also degrade 

as parts get physically larger/thicker. The CT systems currently employed by NASA may not 

have the combination of penetrating power and resolution to detect critical defects in larger 

parts made by AM.

Physical Reference Standards

Physical reference standards are a basic requirement for any NDE process. However, they 

are just starting to be designed and fabricated for the AM processes and are a needed first step 

in understanding the capabilities of the various NDE methods and techniques that are being 

used on these materials. Again, this will take time because of the numerous AM processes and 

the vast processing parameter space. Furthermore, until critical defect types and sizes are 

1 NASGRO® is a registered trademark of Southwest Research Institute, San Antonio, TX.

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properly quantified, representative defect reference standards are being designed and 

fabricated using engineering judgment.

Inspection Procedures

The lack of standardized procedures (ASTM or otherwise) for the NDE of finished parts

made by AM has been discussed. Although many of the existing NDE standard procedures for 

conventionally wrought, forged, and molded metal and plastic parts are generally applicable to 

parts made by AM, specific requirements such as geometrical complexity, porosity, surface 

finish and deeply embedded flaws may exist that must be addressed by newer standardized 

NDE procedures.

In-Process Monitoring

It is recognized that in-process monitoring of the part during the build may be a game 

changer in 1) improving the consistency, repeatability, and uniformity across machines and 

2) qualification and certification of parts made by AM (NIST 2013a; NRC 2014). Part 

qualification during manufacturing is essential because of the difficulty in applying NDE methods 

to inspect complex parts made by AM after their fabrication. Research on in-process infrared 

monitoring of weld pool temperature and profile is underway, and high-speed visual monitoring 

techniques are available. However, automatic defect recognition algorithms need to be 

developed, and current AM fabrication equipment will likely require modification prior to the 

successful implementation of these novel inspection techniques. Again, this will likely take years 

because of the many processes and complex processing parameter space previously 

discussed.

Qualification and Certification

Once the effects of critical defects are understood, physical reference standards have been 

fabricated, and suitable NDE inspection procedures have been developed, qualification and 

certification of parts made by AM becomes achievable and practical. The need to qualify and 

certify parts used in flight applications is especially relevant since NASA (Kjelgaard 2013; 

Higginbotham 2014) and its commercial space partners (SpaceX 2014) are already 

aggressively pursuing AM to make flight hardware. However, there are no NDE protocols 

currently in place to evaluate the quality, workmanship and acceptability of these parts. Central 

to NDE-based qualification and certification of parts used in NASA ground applications and nonhuman rated and human rated spacecraft are several NASA standards. Central to NDE-based 

qualification and certification of parts used in NASA ground applications and non-human rated 

and human rated spacecraft are several NASA standards: NASA-STD-5001, NASA-STD-5009, 

NASA-STD-6016 (NASA 2014; NASA 2008b; NASA 2008a). Nondestructive evaluation

protocols developed to qualify and certify parts made by AM will adhere to and defer to these 

overarching NASA requirements documents.

2.4 NASA NDE Data: Illustrative Examples

Computed Tomography

Computed tomography scans of a Ti-6Al-4V ASTRO-H adiabatic refrigerator component 

(Figure 15) and Pogo-Z baffles, RS-25/J2-X nozzles, injectors and valve bodies (Figures 16 and 

17), demonstrate the ability of CT to detect simulated internal flaws and inaccessible internal 

features. CT has also demonstrated utility to confirm closure of porosity by HIP post-processing 

and to detect high-density inclusions in EBM as-manufactured Ti-6Al-4V specimens subjected 

to HIP (Figure 18). This demonstrates the value of CT to 1) detect deep or embedded defects;

2) interrogate inaccessible features; 3) confirm the effectiveness of post-process treatments

25
often required to make usable parts made by AM; and 4) to characterize and qualify asmanufactured parts made by AM. One limitation of CT is the inability to reliably detect cracks,

since cracks oriented perpendicular to the x-ray beam may not be detected.

(Images courtesy of GSFC)

Figure 15

Computed tomography images of an indexing seam on the interior wall (left),

and internal structure of a Ti-6Al-4V ASTRO-H adiabatic refrigerator component (right).

(Images courtesy of MSFC)

Figure 16

Computed tomography images of Pogo-Z baffles, RS-25/J2-X nozzles, injectors and valve 

bodies made by a direct metal laser sintering process 

Pogo-Z Baffle

Injector

Injector

Nozzle

26
(Images courtesy of MSFC)

Figure 17

Photography (left) and computed tomography image (right) of a direct metal laser sintered

aluminum gauge black 

(Images courtesy of GRC)

Figure 18

GRC computed tomography of an as-received Ti-6Al-4V tensile sample and 

following hot isostatic pressing, confirming closure of porosity.

Penetrant Testing

A survey of representative NDE data acquired-to-date is informative and reveals some of 

the advantages and limitations of NDE as well as specific technological challenges that need to 

be addressed and advanced. For example, one of the prominent features of parts made by AM

is higher levels of porosity compared to conventional wrought, cast or molded parts. The 

irregular or rough surfaces present in these parts make traditional NDE methods for the 

detection of surface defects difficult to impossible to accomplish. For example, PT of an 

as-manufactured Ti-6Al-4V specimen and a machined surface of a Pogo-Z baffle highlight the 

fact that PT may not be a realistic method for inspection of porous or rough parts made by AM

without special post-process machining and polishing (Figures 19 and 20). 

27
(Images courtesy of GRC and MSFC, respectively)

Figure 19

Penetrant testing of a Ti-6Al-4V block under development for a liquid rocket gaseous 

hydrogen/liquid oxygen (GH2/LOX) injector (left) and a Pogo-Z baffle (right) showing high 

background noise due to as-manufactured surface roughness. 

(Images courtesy of GFRC)

Figure 20

Optical photograph of variable background penetrant indications (left) 

and of penetrant indications from indexing seams on a Ti-6Al-4V ASTRO-H 

adiabatic refrigerator component (right).

Similarly, understanding how to measure complex internal/lattice structures containing deep 

or inaccessible defects will represent a daunting task. Clearly, newer, more sensitive, and noncontact NDE methods are needed to overcome issues that limit the effectiveness of techniques 

complementary to CT, such as PT, ET, and UT.

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Eddy Current Testing

Eddy current testing of accessible regions of additively manufactured components should 

prove to be very similar to that of conventionally formed (machined, cast) metals. As for any 

metal component subjected to ET, surface finish and grain structure play a huge role in the 

success of the method in finding critical defects. For example, ET of an Inconel Pogo-Z baffle 

(Figure 21) showed that holes not properly prepared had a high degree of background noise. 

The as-build surface finish was too noisy for ET and had to be completely removed to get a 

good baseline signal. Regions that were machined smooth behaved well. Similarly, ET of 

cracked areas of a SLM valve body (Figure 22) revealed no discernable signals from the 

scratches due to overall surface roughness of the part (signal from smooth area was only 

slightly less noisy than signal from scratched area). Some research into the understanding of 

the basic grain structure of the material still needs to be performed, and this grain structure will 

probably drive additional probability of detection studies to prove out the method for each 

unique AM material and fabrication process.

(Photographs courtesy of MSFC)

Figure 21

Eddy current testing of a Pogo-Z baffle showing the ET probe in the standard set-up hole (left), 

probe in Pogo-Z bottom hole (center), and probe in Pogo-Z flange hole.

(Photographs courtesy of MSFC)

Figure 22 

Selective laser melting valve body showing smooth area on side (left) and the scratched area 

that were inspected by eddy current testing.

Structured Light 

Given the possible geometrical and property variation that can occur during deposition of 

successive layers during the AM build process, control of both part uniformity and dimensions 

are extremely important. One NDE technique that has emerged is structured light, which can be 

used to verify part accuracy to ensure close engineering tolerances are met prior to service or 

29
are maintained during service. Marshall Space Flight Center has been actively applying 

structured light NDE to characterize the dimensional accuracy and surface feature of the PogoZ baffle (Figure 23).

(Image courtesy of MSFC)

Figure 23

Structured light characterization of a Pogo-Z baffle.

Ultrasonic Testing

Ultrasonic testing and PAUT are being used by JSC for interrogating embedded voids or 

weak deposition layers in 2219 aluminum EBF3 parts (Figure 24). 

(Images courtesy of JSC)

Figure 24 

Ultrasonic testing (UT) inspection of a 2219 aluminum electron-beam freeform fabrication part 

showing the area scanned (left) and the UT A- and B-scans (right).

Near Infrared Camera Measurement for In Situ Process Monitoring

Several advancements in the area of feedback and control using near-infrared imaging and 

machine vision techniques are being used to improve the quality of EBF3 processing (Figure 8). 

Advancements include temperature calibration of commercial NIR cameras for measurement 

and characterization of weld pool characteristics. Additional advancements include multiple 

cameras, real-time tracking, and feedback algorithms to improve weld shape consistency. 

Implementations of these systems have improved the consistency of stainless steel straight wall 

samples. Use of calibrated NIR cameras has been shown to enable detection of defects in parts 

during fabrication. Several advancements in the area of feedback and control using NIR imaging 

30
and machine vision techniques are being used to improve the quality of EBF3 processing. 

Advancements include techniques for temperature calibration of commercial NIR cameras for 

measurement and characterization of weld pool characteristics. Temperature calibrations are 

specific to each individual camera and temperature range of the material being inspected. This 

is achieved using black body calibrations in the temperature ranges of the solidification ranges 

of the material under investigation. Multiple cameras allow for simultaneous top and side view 

weld characterizations in real-time. Real-time shape and tracking algorithms allow 

implementations of power feedback to control the temperature of the weld pool faster than what 

is humanly possible. Various parameters of temperature, shape, and cooling rate can be used 

to create metrics for feedback and control in real-time.

3.0 Recommendations

3.1 General Considerations for Additive Manufacturing

General considerations for AM that do not involve NDE are offered here with the caveat that the 

considerations made do not necessarily reflect the current state-of-the-art or current thinking 

within the general AM disciplines. As such, the considerations given below are provided to help 

guide the NDE-related recommendations in Section 3.2. The need for general effort in the 

following technology push areas specific to AM but not including NDE has been demonstrated. 

These gaps are (not listed in order of priority):

• Develop an expert system for AM design

• Generate and use design allowables

• Develop a shared, standardized third-party data repository for input materials data, 

process data, and final part property data

• Validate physics- and properties-based predictive models for AM

• Develop standard data structures, definitions, and metrics for AM models

• Develop in-space processing methods for metals and polymers 

• Refine post-processing requirements

• Implement closed-loop process control

• Develop standard guidelines and methods for qualification and certification of parts 

made by AM

• Adopt standards for AM equipment

• Adopt standards for input materials and finished parts

• Adopt standards for round-robin build and materials testing

Progress in many of these areas must be made before progress is made resolving the NDErelated gaps, discussed next.

3.2 NDE-Specific Recommendations for Additive Manufacturing

This TM demonstrates clearly the vital role NDE will play in closing many of the gaps or 

challenges associated with the advancement of AM. The push to use AM parts in NASA

applications is relatively new and, as a consequence, the knowledge base of NDE as applied to 

those parts is immature. Nondestructive evaluation will be necessary for the qualification and 

certification of AM parts; therefore, resources must be invested to make sure NDE is capable of 

performing this function. There is need for effort in the following technology push areas specific 

to AM and including NDE. These gaps are (not listed in order of priority):

• Develop mature techniques for NDE of finished parts

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• Apply NDE to understand effect-of-defect, including establishment of acceptance limits 

for certain defect types and defect sizes

• Apply NDE to understand scatter in design allowables database generation activities 

• Fabricate physical reference standards to verify and validate NDE data 

• Develop in situ process monitoring NDE to improve feedback control, to maximize part 

quality and consistency, and to obtain certified parts that are ready-for-use directly after 

processing 

• Develop better physics-based process models using and corroborated by NDE

• Develop NDE-based qualification and certification protocols for flight hardware that rely 

on testing and modeling

• Develop ASTM E07-F42 standards for NDE of AM parts

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4.0 References

ASTM WK43031. New Guide for Nondestructive Testing of Additively Manufactured Parts Used 

in Aerospace Applications. American Society for Testing and Materials, West 

Conshohocken, PA, 2014b, astm.org/WorkItems/WK47031.htm.

ASTM WK43112. New Guide for Evaluating Mechanical Properties of Metals Made via Additive 

Manufacturing Processes. American Society for Testing and Materials, West 

Conshohocken, PA, 2014a, astm.org/WorkItems/WK43112.htm.

European Space Agency. Applying a Long-Term Perspective: Laurent Pambaguian Interview.

2014a, esa.int/Our_Activities/Space_Engineering/Clean_Space/Applying_a_longterm_perspective_Laurent_Pambaguian_interview.

European Space Agency. 3D Printing for Space: The Additive Revolution. 2014b, 

esa.int/Our_Activities/Human_Spaceflight/Research/3D_printing_for_space_the_additive

_revolution.

European Space Agency. 3D Printing for Space: The Additive Revolution. 2014c

esa.int/Our_Activities/Technology/Building_a_lunar_base_with_3D_printing.

Gentry, D., A. Micks, and L. Rothschild. Biomaterials out of thin air: in situ, on-demand printing 

of advanced biocomposites. 2014 NIAC Symposium, Stanford University, Stanford, CA, 

February 4-6, 2014.

Ghidini, T. European Space Agency Perspective on Additive Manufacturing (AM). 3D Printing & 

Additive Manufacturing – Industrial Applications, Global Summit, London, UK, 

November 2011a, 3d-printing-additive-manufacturing.com/media/downloads/47-d1-09-

00-b-tommaso-ghinini-esa.pdf.

Ghidini, T. An Overview of Current AM Activities at the European Space Agency. 3D Printing & 

Additive Manufacturing – Industrial Applications, Global Summit, London, UK, 

November 2011b, 3d-printing-additive-manufacturing.com/media/downloads/52-d1-12-

20-c-tommaso-ghidini-esa.pdf.

Harris, I. D. Development and Implementation of Metals Additive Manufacturing. Edison 

Welding Institute presentation to the U.S. Department of Transportation, 2011.

Higginbotham, K. Additive Manufacturing & NDE Tasks Applicable to SLS. MSFC/Advanced 

Development Office, April 3, 2014.

Khoshnevis, B., K. H. Burks, E. Ethridge, D. Tucker, W. Kim, and M. R. Fiske. Lunar Contour 

Crafting – A Novel Technique for ISRU-Based Habitat Development. American Institute 

of Aeronautics and Astronautics Conference, January 2005.

Khoshnevis, B. Contour Crafting Simulation Plan for Lunar Settlement Infrastructure Build-Up.

University of Southern California, Los Angeles, CA, NASA Innovative Advanced 

Concepts (NIAC) Program Phase I Award, 2011.

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Khoshnevis, B. ISRU-Based Robotic Construction Technologies for Lunar and Martian 

Infrastructures. University of Southern California, Los Angeles, CA, NASA Innovative 

Advanced Concepts (NIAC) Program Phase II Award, 2012, 

youtube.com/watch?v=OU9Ek3UgZaw&feature=youtu.be.

Kjelgaard, C. The new meaning of additive value. Aerospace America, 20-22, November 2013,

aerospaceamerica.org/Documents/AerospaceAmerica-PDFs-2013/November2013/GreenEngineering_AANov2013.pdf.

Knapp, A. “First Zero-G 3D Printer Is On Its Way To The Space Station”. Forbes, 22 September 

2014, http://www.forbes.com/sites/alexknapp/2014/09/22/first-zero-g-3d-printer-is-on-itsway-to-the-space-station/.

Macy, B. America Makes National Additive Manufacturing Innovation Institute. TTCP TP1-5 

Joint Workshop, Arlington, VA, February 27, 2014, slides 9-13.

Martukanitz, R., T. Simpson, and G. Messing. The Center for Innovative Materials Processing 

through Direct Digital Deposition (CIMP-3D). TTCP TP1-5 Joint Workshop, Arlington, 

VA, February 27, 2014.

NASA. Space Technology Roadmaps: The Future Brought to You by NASA. Office of the Chief 

Technologist, National Aeronautics and Space Administration, Washington, DC,

December 13, 2013, nasa.gov/offices/oct/home/roadmaps/#.VE7CgRA1uvA.

NASA-STD-5001B. NASA Technical Standard, Structural Design and Test Factors of Safety for 

Spaceflight Hardware. National Aeronautics and Space Administration, Washington, DC, 

Approved: August 6, 2014. 

NASA-STD-5009. NASA Technical Standard, Nondestructive Evaluation Requirements for 

Fracture-Critical Metallic Components. National Aeronautics and Space Administration, 

Washington, DC, Approved: April 7, 2008b. 

NASA-STD-6016. NASA Technical Standard, Standard Materials and Processes Requirements 

for Spacecraft. National Aeronautics and Space Administration, Washington, DC, 

Approved: July 11, 2008a.

National Institute of Standards and Technology. Measurement Science Roadmap for MetalBased Additive Manufacturing. Prepared by Energetics Incorporated, Columbia, 

Maryland, for NIST, U.S. Department of Commerce, p. 19, May 2013a.

National Institute of Standards and Technology. Qualification for Additive Manufacturing 

Materials, Processes, and Parts. NIST, 100 Bureau Drive, Gaithersburg, MD, Start Date 

October 1, 2013b, nist.gov/el/isd/sbm/qammpp.cfm.

National Research Council. 3D Printing in Space. The National Academies Press, 500 Fifth 

Street NW, Washington, DC, 2014.

Rothschild, L. Biomaterials out of thin air: in situ, on-demand printing of advanced 

biocomposites. NASA Ames Research Center, Moffett Field, CA, NASA Innovative 

Advanced Concepts (NIAC) Program Phase I Award, 2013.

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SpaceX. SpaceX unveils Dragon V2, its first manned spacecraft. Hawthorne, CA, May 29, 2014. 

cnet.com/news/spacex-unveils-dragon-v2-its-first-manned-spacecraft/.

Wohlers, T. and T. Gorne. History of additive manufacturing. Wohlers Report 2011, State of the 

Industry, wohlersassociates.com/history, 2011.

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