On Earth the flames are like undulating tongues, but not in space. Without gravity, hot air lacks the buoyant force necessary for flames to take on the typical dancing waves we know. In microgravity they sometimes form ethereal domes and orbs that can burn at 480°C (a gas stove at full power is around 1,700°C). The flames in the image above were generated aboard the International Space Station as part of ACME (Advanced Combustion Experiments in Microgravity). “Science fiction writers have contacted me,” says ACME researcher Peter Sunderland. They’re like from another world.” Over more than four years, the ACME project has lit more than 1,500 test flames aboard the station to improve spacecraft fire safety and refine combustion computer models. Good miss: the burning of fossil fuels remains a huge source of carbon emissions and air pollution.
This article belongs to the October 2022 issue of the magazine National Geographic.