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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
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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
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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
17
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!
21
Acknowledgement
Are there any questions?
22
Questions