The key to long-term space exploration may lie in a nanomaterial 50,000 times thinner than a human hair.
Imagine you're an astronaut on a mission to Mars. As you journey through the void, an invisible threat constantly bombards your spacecraft—cosmic radiation. This isn't the radiation we experience on Earth, protected by our atmosphere and magnetic field. In space, subatomic particles traveling at nearly the speed of light penetrate everything in their path, damaging equipment and posing serious health risks to crew members.
For decades, spacecraft have relied on aluminum hulls and other materials for protection, but these traditional shields have limitations, especially against certain types of cosmic radiation. What if we could create a next-generation shield that's lighter, stronger, and more effective? Enter boron nitride nanotubes (BNNTs)—tiny cylindrical structures that may hold the key to safer space exploration.
To understand why scientists are excited about BNNTs, picture a chain-link fence made of boron and nitrogen atoms arranged in a hexagonal pattern, rolled into an incredibly tiny tube. These nanotubes measure roughly 50 nanometers in diameter—so small that billions could fit on the head of a pin—yet they possess extraordinary properties 1 .
Young's modulus up to 1.3 TPa, making them among the strongest known materials 7
Approximately 200 W/mâ»Â¹Kâ»Â¹, helping dissipate heat efficiently 7
BNNTs' most valuable property for space radiation protection lies in boron's natural ability to absorb neutrons. The boron-10 isotope, found in BNNTs, has an enormously high thermal neutron absorption cross-section of 3,835 barns (a unit measuring absorption capability) 7 . This means BNNTs can capture harmful neutrons from cosmic radiation 200,000 times more effectively than carbon nanotubes 3 4 .
This exceptional neutron-absorbing capability, combined with their mechanical strength and thermal stability, makes BNNTs ideal multifunctional materials—they can provide structural support while simultaneously offering radiation protection, unlike traditional shielding that often adds dead weight.
To truly understand how BNNTs withstand the harsh environment of space, researchers conducted a comprehensive investigation into their stability when bombarded by high-energy particles 1 . The study employed both theoretical modeling and experimental approaches to simulate the effects of cosmic radiation on BNNT structures.
Researchers obtained commercially available BNNTs with an average outer diameter of 50 nm, inner diameter of 18 nm, and average length of 10 micrometers. The sample assay contained approximately 90% BNNTs, with the balance being hexagonal boron nitride particles and flakes.
The team exposed BNNT samples to different types of radiation:
After irradiation, scientists used high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) to examine structural changes in the BNNTs at the atomic level.
The results were promising for space applications. After exposure to high-energy radiation that would damage many materials, the BNNTs showed remarkable resilience 1 :
This resilience stems from BNNTs' unique architecture at the nanoscale. Even when radiation knocks atoms out of place, the structure can often reorganize itself without catastrophic failure.
| Radiation Type | Energy Level | Observed Effects on BNNT | Implications for Space Applications |
|---|---|---|---|
| Proton | 100 MeV | No severe damage; intact outer shells | Excellent protection against solar particle events |
| Argon ions | 200 keV | Slight decrease in crystallinity | Resilient against heavy ions in cosmic rays |
| Nitrogen ions | 200 keV | Slight decrease in crystallinity | Stable under various charged particles |
| Electrons | 200-300 keV | Shortening; local fractures; vacancy defects | Moderate resistance to secondary electrons |
Table 1: BNNT Response to Different Types of Radiation
The most convincing test of BNNTs' space-worthiness came from an actual space mission. In March 2023, Ti/2 vol.% hBN coatings containing boron nitride nanomaterials hitched a ride to the International Space Station (ISS) aboard SpaceX-27 2 . These samples spent 171 days exposed directly to the space environment outside the ISS as part of the Materials International Space Station Experiment (MISSE-17).
Distance traveled during 4,512 orbits
From -30°C to 44°C
Galactic cosmic rays and solar particles
When the samples returned to Earth in December 2023 after completing 4,512 orbits and traveling 115 million miles, researchers made exciting discoveries 2 :
| Coating Type | Crack Density Change | Porosity Change | Microhardness Change | Elastic Modulus Change |
|---|---|---|---|---|
| APS Ti/2hBN | Increased by 21% | Increased by 50% | Not specified | Not specified |
| VPS Ti/2hBN | Little to no increase | Increased by 19% | Increased by 56% | Increased by 26% |
Table 2: Performance Comparison of BNNT-Composite Coatings After Space Exposure
The exceptional performance of these BNNT-containing coatings under real space conditions demonstrates their potential for protecting spacecraft and equipment in long-duration missions.
The applications of BNNTs extend far beyond radiation shielding alone. Recent advancements have incorporated these nanomaterials into flexible composite fibers that can be woven into fabrics for next-generation spacesuits 3 4 . These BNNT-aramid composite fibers are:
Comfortable enough for extended wear during spacewalks
Protection up to 500°C in extreme environments
Effective radiation protection during spacewalks
Similarly, BNNT-enhanced polymers are being developed for use in spacecraft components that serve dual purposes—providing structural support while absorbing harmful radiation 6 7 .
| Material/Equipment | Function in Research | Key Characteristics |
|---|---|---|
| Boron Nitride Nanotubes (BNNT) | Primary radiation-absorbing nanomaterial | High boron content for neutron absorption; tubular structure for mechanical strength |
| Polydimethylsiloxane (PDMS) | Polymer matrix for BNNT composites | Flexible; stable under radiation; easy to process |
| Epoxy resins | High-temperature polymer for structural composites | Thermal stability; good adhesion to BNNTs; structural integrity |
| Polyethylene | Hydrogen-rich polymer matrix for composites | Effective at slowing down neutrons; enhanced by BNNT addition |
| Stopping and Range of Ions in Matter (SRIM) | Computer simulation software | Models ion penetration depth and damage in materials |
| High-Resolution Transmission Electron Microscope (HR-TEM) | Structural characterization | Visualizes atomic-level defects and damage in BNNTs after irradiation |
Table 3: Essential Research Reagents and Materials in BNNT Radiation Shielding Studies
As we look toward establishing a long-term presence on the Moon and eventually sending humans to Mars, developing effective radiation protection becomes increasingly critical. BNNT technology offers a promising solution that addresses multiple challenges simultaneously—radiation shielding, structural integrity, and thermal management.
Ongoing research continues to optimize BNNT composites for space applications. Scientists are experimenting with different polymer matrices, nanomaterial concentrations, and manufacturing techniques to enhance these materials' performance 6 7 . As production methods improve and costs decrease, we may soon see BNNT-based protection as a standard feature in spacecraft, habitats, and spacesuits.
The incredible journey of BNNTs from laboratory curiosity to space-tested material represents the power of nanotechnology to solve some of humanity's most challenging problems. These tiny tubes may well enable our big dreams of exploring the cosmos.