Chinese astronauts aboard the Shenzhou 16 spacecraft conducted an intriguing experiment on September 21, lighting a candle during a live lecture broadcast from China’s Tiangong space station. The purpose of the experiment was to showcase how flames behave in a microgravity environment. Astronauts Gui Haichao and Zhu Yangzhu demonstrated this phenomenon to a worldwide audience.
The flames produced by the lit candle in space appeared almost spherical, contrasting with the teardrop-shaped flames typically observed on Earth. On our planet, flame shapes are influenced by buoyancy-driven convection, with hot air rising and cold air descending, creating the iconic teardrop form. However, in the microgravity of low Earth orbit, this combustion convection current is weak, causing flames to diffuse in all directions, resulting in spherical fireballs.
This groundbreaking experiment was conducted as part of the “Tiangong classroom” initiative, a series of live lectures hosted from China’s space station. During the broadcast, astronauts interacted with students across five classrooms in China, demonstrating various microgravity phenomena. The experiment shed light on the significant differences in physical processes in space compared to those on Earth.
The uniqueness of this experiment lies in the use of open flames, which is typically restricted on the International Space Station (ISS) due to strict rules regarding flammable materials and fire safety. The ISS enforces stringent measures to prevent fire hazards, a response to a major fire incident that occurred on the Russian space station Mir in 1997.
While the subject of combustion in microgravity has been extensively studied on the ISS using specially designed combustion integrated racks, Tiangong space station also boasts its Combustion Experiment Rack (CER). This facility is dedicated to conducting in-depth research on combustion and fire behavior in space. The successful demonstration of open flame combustion on Tiangong provides valuable insights into fire dynamics in microgravity, contributing to our understanding of safety measures and potential applications for future space exploration missions.