Sheila A. Thibeault, Catharine C. Fay and Kevin D. Earle NASA Langley Research Center, Hampton, Virginia

Godfrey Sauti, Jin Ho Kang, and Cheol Park National Institute of Aerospace, Hampton, Virginia!

Radiation Shielding Materials Containing Hydrogen, Boron, and

Nitrogen: Systematic Computational and Experimental Study!

Radiation Shielding Materials Containing Hydrogen, Boron, and

Nitrogen: Systematic Computational and Experimental Study!

Sheila A. Thibeault, Catharine C. Fay, and Kevin D. Earle NASA Langley Research Center, Hampton, Virginia

Godfrey Sauti, Jin Ho Kang, and Cheol Park National Institute of Aerospace, Hampton, Virginia!

Hazards in Space •  Galactic Cosmic Radiation •  Solar Particle Events (Solar Flares) •  Secondary Neutrons •  Micrometeoroids and Orbital Debris •  Large Temperature excursions

Norbury, et. al., NASA LaRC Space Radiation Roadmap

Neutron

Objective: To develop multifunctional lightweight systems to reduce mass and to provide greater physical protection against radiation (and in addition, protection against

micrometeoroids and orbital debris, thermal extremes, pressure extremes).

Solar Particle Events & Galactic Cosmic Radiation

Secondary Neutrons

Micrometeoroids

Primary Hazards in Space

Space Radiation Risks

Humans

Electronics

Materials

Acute risks (acute radiation syndrome) Chronic risks (cancer from GCR)

Single event effects

Degradation

2

Need

3

NASA Space Technology Roadmaps and Priorities Both Radiation Mitigation for Human Spaceflight and Lightweight and Multifunctional Materials and Structures are in the top 8 technology needs for all three technology objectives considered. Radiation Mitigation is ranked as the #1 priority for extending and sustaining human activities beyond low Earth orbit.

Technology Horizons: Game Changing Technologies for the Lunar Architecture Among technology areas that could have the most game changing effects on NASA’s lunar architecture - Radiation Shielding identified as revolutionary and Advanced Nanotube Based Materials identified as a rapidly evolving technology.

Technology Frontiers: Breakthrough Capabilities for Space Exploration Both High Strength Materials and Nanotubes are identified as crosscutting technologies that are consistently mentioned as potential or even necessary components of multiple breakthrough capabilities.

Human Architecture Team: Technology and Development Radiation Protection and Lightweight Structures have been identified as enabling technologies for the campaigns being considered by the Human Architecture Team.

•  Radiation Shielding Structural Systems •  Biological counter measures (pharmaceuticals) •  Crew selection (genetics) •  Active radiation shielding (magnetic, plasma,

electrostatic) •  Advanced propulsion (minimizing mission duration) •  Warning systems (predication and detection) •  Temporary shelter (safe haven)

4

Radiation Protection Concepts

•  Radiation Shielding Structural Systems •  Biological counter measures (pharmaceuticals) •  Crew selection (genetics) •  Active radiation shielding (magnetic, plasma,

electrostatic) •  Advanced propulsion (minimizing mission duration) •  Warning systems (predication and detection) •  Temporary shelter (safe haven)

5

Radiation Protection Concepts

"Because you have to build it out of something."

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With structural, lightweight, low z material, such as H, B, N, .…

Is this possible?

Structural Radiation Shielding Systems

7

Good Radiation Shielding Materials

Good Structural Materials

Water

Hydrogen

Polyethylene

Aluminum or Aluminum/Lithium

Hydrogenated BNNT

Value of BNNT for Primary Structures

8

BNNT

0

200

400

600

800

1000

0 20 40 60 80 100 120 140 160 180

Spec

ific

Mod

ulus

, GPa

/(g/c

m3 )

Specific Strength, GPA/(g/cm3)

IM7

M46J

M46J CFRP Al 2219

SiC/Be

TiFoamSand BeAl

Al2O3/Al TiAl IM7 CFRP AlFoam

Nt/P

Nt/Al

0

50

100

150

200

250

300

0 0.5 1 1.5 2 2.5 3 3.5 Spec

ific

Mod

ulus

, GPa

/(g/

cm3 )

Specific Strength, GPA/(g/cm3)

Baseline Materials 5-10 years (TRL = 4-6) 10-20 years + (TRL = 1-3)

Charles E. Harris, M. J. Shuart, H. Gray, NASA/TM-2002-211664

The structural materials properties

of BNNT significantly exceed

those of current SOA materials.

BNNT

0

200

400

600

800

1000

0 20 40 60 80 100 120 140 160 180

Spec

ific

Mod

ulus

, GPa

/(g/c

m3 )

Specific Strength, GPA/(g/cm3)

Value for High Temperature Use

9

Baseline Materials 5-10 years (TRL = 4-6) 10-20 years + (TRL = 1-3)

Charles E. Harris, M. J. Shuart, H. Gray, NASA/TM-2002-211664

At high temperatures, the

properties of BNNT significantly exceed

those of current SOA materials.

SiC/Be

TiAl

0

50

100

150

200

250

300

0   0.5   1   1.5   2   2.5   3   3.5  

Spec

ific

Mod

ulus

, GPa

/(g/

cm3 )

Specific Strength, GPA/(g/cm3)

@ 700⁰C

BNNT Production Rig at LaRC

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Production Approach

11

Benefits

• High scale up potential

• Synthesized with standard industrial cutting/welding lasers

• No toxic catalysts (only boron and nitrogen are used as reactants)

• Composed only of B and N, no binders or metals

• Can spin yarn directly from BNNT raw material

Synthesis Time: ~5 minutes

LaRC’s Enabling Innovation

12 Smith, et. al., Nanotechnology, 20 505604 (2009)

LaRC’s BNNT •  Tubes with one to few walls - with high

crystallinity •  Very long, high aspect ratio tubes •  Nontoxic, as no toxic catalysts are used •  High service temperature (over 700⁰ C) •  Highly electroactive •  Demonstrates extraordinary length and

natural alignment of as grown BNNT nanotubes

•  World’s First BNNT Yarn!

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Neutron Cross Section Versus Incident Neutron Energy

B10 is superior to all up to 103 eV

Neutron Radiation Shielding Study Radiation Shielding Structural Materials •  Hydrogen, Boron, Nitrogen •  BN, BNNT •  Low density polyethylene (LDPE); polyimides (Kapton, Ultem, CP2, (β-CN)APB/ODPA)

Polymer Synthesis •  In-situ polymerization under simultaneous sonication and shear •  Supercritical fluid infusion

Characterization •  LaRC Neutron Radiation Exposure Lab: 1 Curie Am/Be Source •  Moderated by polyethylene cylinder block •  Specimens: 2 in. x 2 in. neat, BN, and BNNT polymer composites •  Detection Foil: 1.25 in. Indium Foil (0.5 mm, 19 barns) •  RSMES: Radiation Shielding Materials Evaluation Software

Modeling •  OLTARIS

http://www.inp.nsk.su/bnct/introduction/introduction.en.shtml

neutron

14

LDPE: Low density polyethylene h-BN: Hexagonal boron nitride platelets BNNT: Boron nitride nanotubes Considering wt%, BNNT is better than h-BN

Advanced Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Preliminary Results

Nitrogen is effective shielding material. BNNT is effective shielding material.

If linearly projected

High surface area

15

Computational and Experimental Validation for Materials Selection

PE

Aluminum Carbon

More Hydrogen

Candidate Radiation Shielding Materials

More Hydrogen = Better Shielding 16

State of Art

Less Dosage Is Better

Materials assumed to have common 30 cm thickness.

BN materials perform better than LH2 and water. BN+5%H performs better than state of art polyethylene.

Dose Equivalent of Various Shielding Materials: OLTARIS Modeling

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WHY H, B, and N?

18

Hydrogen is effective at (1) fragmenting heavy ions such as are found in galactic cosmic radiation (GCR), (2) stopping protons such as are found in solar particle events (SPE), and (3) slowing down neutrons such as are formed as secondaries when the GCR and SPE interact with matter. Hydrogen, however, by itself is not a structural material. Polyethylene (CH2) contains a lot of hydrogen and is a solid material, but it does not possess sufficient strength for load bearing aerospace structural applications. The industry appears to be stuck with aluminum alloys for primary structures, retrofitted with polyethylene or water for radiation shielding. Clearly, a newer paradigm or concept is needed. We think we have a new concept!

BNNT

Forms

19

Processable into Composite, Fabric, Yarn, and Film Forms

H, B, & N Containing Materials BNNT

Hydrogen Storage BNNT Hydrogenated BNNT

Examples of Applications

20

Forms of BNNT Materials

Primary Structure & Radiation Shielding in

Deep Space or Surface Habitats

Primary Structure & Radiation Shielding in

Nuclear Thermal Rockets

As Fabric in EVA Suits to Provide Radiation Protection

High Temperature Components In Rocket Engines

We thank NIAC for providing us with the funding opportunity to explore this radiation shielding concept!

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Acknowledgement

Are there any questions?

22

Questions