In 2012, NASA observed a fuel droplet continue burning invisibly in space after the visible flame went out, producing carbon monoxide and formaldehyde

NASA's 2012 space station experiment revealed an invisible cool flame phenomenon. This unexpected discovery occurred when fuel droplets continued burning without visible heat. Microgravity conditions allowed scientists to observe this slow, low-temperature combustion process. The findings have implications for engine design and space fire safety. This research continues to highlight microgravity's unique scientific revelations.