Scientists on the International Space Station may have found a way to improve internal combustion engines with some zero gravity flame experiments. It turns out gravity is a huge factor in forming the shapes of flames. As combustion happens, the exhaust gases get hot and rise which creates a current that draws fresh air in from the bottom of the flame. It’s this air current that causes flames to flicker upwards and to burn much hotter and faster thanks to the constant supply of fresh air.

As we saw with Bubbles and Anti-Bubbles in Water, air density has little effect in space. What does that mean for combustion? Without the ability to to produce convective air currents, flames burn completely differently. The exhaust gases naturally dissipate in all directions and at slower speeds. Without the rising hot air pulling it upwards, the flame takes on a spherical shape. It also burns much cooler since it’s not being constantly force fed fresh air.

These Cool Flames are what have scientists interested. We’ve barely been able to create them here on Earth, but it’s how all combustion happens in space. Gasoline has a lot of energy content, but the problem is controlling it. When ignited, all of the energy is released at once. While this has allowed us to make powerful engines to move cars, the efficiency is abysmal. Only a quarter to a third of the energy of content from the gas in your tank ends up turning the wheels of your car. The rest of it is wasted as heat. As we saw with slingshots and bullwhips, a tapered and controlled release of energy is often times more effective than an instant punch. If we can figure out how to replicate this Cool Flame chemistry inside of an engine, we can burn fuel slower and cooler to get more work out of it.