This document discusses radiation shielding materials containing hydrogen, boron, and nitrogen. It summarizes a study investigating boron nitride nanotubes (BNNT) for use as a structural radiation shielding material. BNNT outperforms current state-of-the-art materials in strength and modulus properties, particularly at high temperatures. Experimental results show that BNNT and other hydrogen-, boron-, and nitrogen-containing materials perform better than water and polyethylene in reducing radiation dosage. BNNT composites have potential for applications as primary structures and radiation shielding in space habitats, rockets, and spacesuits due to their strength, shielding ability, and ability to be formed into various shapes.

1. Radiation Shielding Materials
Radiation Shielding Materials
Containing Containing Hydrogen, Hydrogen, Boron, Boron, and
and
Nitrogen: Systematic Systematic Computational
Computational
and Experimental Study!
and Experimental Study!
Sheila Sheila A. A. Thibeault, Thibeault, Catharine Catharine C. C. Fay, 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!

2. Primary Hazards in Space
Solar Particle Events &
Galactic Cosmic Radiation
Secondary
Neutrons
Hazards in Space
• Galactic Cosmic Radiation
• Solar Particle Events (Solar Flares)
• Secondary Neutrons
• Micrometeoroids and Orbital Debris
• Large Temperature excursions
Micrometeoroids
Neutron
Space Radiation Risks
Humans
Electronics
Materials
Acute risks (acute radiation syndrome)
Chronic risks (cancer from GCR)
Single event effects
Degradation
Norbury, et. al., NASA LaRC Space Radiation Roadmap
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).
2

3. Need
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.
3
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.

4. • 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

5. • 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

6. "Because you have to build it out
of something."
6
With structural, lightweight, low z material, such as H, B, N, .…
Is this possible?

7. Structural Radiation Shielding Systems
7
Good Radiation
Shielding Materials
Good Structural
Materials
Water
Hydrogen
Polyethylene
Aluminum or
Aluminum/Lithium
Hydrogenated
BNNT

8. Value of BNNT for Primary Structures
BNNT
8
1000
800
600
400
200
0
IM7
M46J
300
250
200
150
100
50
0 20 40 60 80 100 120 140 160 180
Specific Modulus, GPa/(g/cm3)
Specific Strength, GPA/(g/cm3)
M46J
Al 2219C FRP
SiC/Be
TiFoamSand
BeAl
TiAl Al2O3/Al
IM7 CFRP
AlFoam
Nt/P
Nt/Al
0
0 0.5 1 1.5 2 2.5 3 3.5
Specific Modulus, 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.

9. BNNT
1000
800
600
400
200
0
Value for High Temperature Use
300
250
200
150
100
50
0 20 40 60 80 100 120 140 160 180
Specific Modulus, GPa/(g/cm3)
Specific Strength, GPA/(g/cm3)
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
0
0.5
1
1.5
2
2.5
3
3.5
Specific Modulus, GPa/(g/
cm3)
Specific Strength, GPA/(g/cm3)
@ 700⁰C

10. BNNT Production Rig at LaRC
10

11. Production Approach
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
11
Synthesis Time: ~5 minutes

12. LaRC’s Enabling Innovation
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!
12 Smith, et. al., Nanotechnology, 20 505604 (2009)

13. 13
Neutron Cross Section Versus Incident Neutron Energy
B10 is superior to all up to 103 eV

14. 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
neutron
http://www.inp.nsk.su/bnct/introduction/introduction.en.shtml
14

15. Advanced Radiation Shielding Materials Containing Hydrogen,
Boron, and Nitrogen: Preliminary Results
If linearly projected
High surface area
Nitrogen is effective shielding material. BNNT is effective shielding material.
LDPE: Low density polyethylene
h-BN: Hexagonal boron nitride platelets
BNNT: Boron nitride nanotubes
Considering wt%, BNNT is better than h-BN
15

16. Candidate Radiation Shielding Materials
Computational and Experimental Validation for Materials Selection
Carbon Aluminum
PE
More
Hydrogen
More Hydrogen = Better Shielding
16

17. Shielding Materials: OLTARIS Modeling
Less
Dosage
Is Better
State of Art
Materials assumed
to have common
30 cm thickness.
Dose Equivalent of Various
BN materials perform better than LH2 and water.
BN+5%H performs better than state of art polyethylene.
17

18. 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

19. Forms
19
H, B, & N Containing Materials BNNT
Hydrogen Storage BNNT Hydrogenated BNNT
Processable into Composite, Fabric, Yarn, and Film Forms

20. 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

21. We thank NIAC
for providing us
with the funding opportunity
to explore
this radiation shielding concept!
21
Acknowledgement

22. Are there any questions?
22
Questions