<p>Atomic oxygen (AO) impinging on satellite surfaces in very low Earth orbit (VLEO) transfers momentum and energy, leading to material degradation and drag forces. To be able to counteract these effects, we investigate the impact mechanisms of AO on both crystalline and amorphous alumina (Al<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$_2$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>2</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>O<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$_3$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>3</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>) surfaces, which occur as oxidized surface layers of bulk aluminum, commonly used in satellite design. Al<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$_2$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>2</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>O<InlineEquation ID="IEq4"> <EquationSource Format="TEX">$_3$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>3</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation> also serves as a protective coating for solar panels, often covering extensive satellite surfaces. Using Molecular Dynamics (MD) simulations with classical and machine-learned (ML) force fields, we gain insights into material stability, angular distributions of reflected particles, and adsorption rates. Our findings indicate that bare Al<InlineEquation ID="IEq5"> <EquationSource Format="TEX">$_2$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>2</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>O<InlineEquation ID="IEq6"> <EquationSource Format="TEX">$_3$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>3</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation> does not degrade under AO impacts but accumulates oxygen due to high adsorption rates. The angular distribution of reflected particles is highly dependent on the surface structure and the angle of incidence, with a higher ratio of specular reflection observed on smoother surfaces and at larger incidence angles measured to the surface normal.</p>

Impact of hyperthermal oxygen on alumina surfaces investigated by molecular dynamics simulations

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2025年8月12日

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Stephen Hocker,
Hansjörg Lipp,
Nico Segreto,
Johannes Roth,
Johannes Kästner

摘要

Atomic oxygen (AO) impinging on satellite surfaces in very low Earth orbit (VLEO) transfers momentum and energy, leading to material degradation and drag forces. To be able to counteract these effects, we investigate the impact mechanisms of AO on both crystalline and amorphous alumina (Al $_2$ $_{2}$ O $_3$ $_{3}$ ) surfaces, which occur as oxidized surface layers of bulk aluminum, commonly used in satellite design. Al $_2$ $_{2}$ O $_3$ $_{3}$ also serves as a protective coating for solar panels, often covering extensive satellite surfaces. Using Molecular Dynamics (MD) simulations with classical and machine-learned (ML) force fields, we gain insights into material stability, angular distributions of reflected particles, and adsorption rates. Our findings indicate that bare Al $_2$ $_{2}$ O $_3$ $_{3}$ does not degrade under AO impacts but accumulates oxygen due to high adsorption rates. The angular distribution of reflected particles is highly dependent on the surface structure and the angle of incidence, with a higher ratio of specular reflection observed on smoother surfaces and at larger incidence angles measured to the surface normal.