The violent life of rocket nanoparticles
Researchers from Monash University and collaborators in China have used advanced computer simulations to uncover what happens when tiny particles travelling at extreme speeds smash through hot air inside rocket engines, findings that could help improve the durability and performance of future space and defence technologies.
Researchers from Monash University and collaborators in China have used advanced computer simulations to uncover what happens when tiny particles travelling at extreme speeds smash through hot air inside rocket engines, findings that could help improve the durability and performance of future space and defence technologies.
Published in the journal Physics of Fluids, the study investigates microscopic particles of alumina, a ceramic material formed when aluminium fuel burns inside solid rocket motors.
These particles, thousands of times smaller than the width of a human hair, can reach speeds of up to 10 kilometres per second inside rocket nozzles. Under such extreme conditions, they can heat up, melt, deform and even change shape mid-flight, potentially damaging rocket components in the process.
The research team used molecular dynamics simulations - a type of atom-by-atom computer modelling - to track how the nanoparticles behaved in high-temperature, high-pressure air.
Co-author Associate Professor Qijun Zheng from Monash Mechanical and Aerospace Engineering said the work provides new insight into how particles interact with air under some of the harshest conditions engineers encounter.
The simulations revealed that slow-moving particles remained relatively stable, but particles travelling at hypersonic speeds rapidly heated up due to intense collisions with surrounding air molecules. Smaller particles heated and melted faster because they had more surface area exposed relative to their size.
One of the study’s most striking findings was that molten particles could dramatically change shape during flight. In dense air, some particles stretched into thin “bag-like” structures before collapsing back into new forms.
These changing shapes altered how the particles interacted with the surrounding gas, affecting drag, heat transfer and flight behaviour.
The researchers also discovered that melted particles disturbed the surrounding airflow more strongly than solid particles, creating larger regions of turbulence and energy transfer.
While the research focuses on solid rocket motors, the findings could have broader applications in aerospace engineering, atmospheric re-entry, energy systems and high-temperature industrial processes involving nanoparticles.
The study was led by researchers from the Southeast University-Monash University Joint Research Institute, Monash University and Shanghai University.
Read the full article in Physics of Fluids here.
