Fire in space? A flame can still burn in microgravity, but it does look very strange. Here's why

Fire can’t start in the vacuum of space, as there is no oxygen available for combustion.

They can, however, start inside a spacecraft or space station that has oxygenated air for passengers.

Any fire in space would look and behave differently than the lit candles on your birthday cake back at home, though, and that’s down to gravity.

Flame shape and gravity

The typical teardrop shape of a burning candle on Earth is caused by the effects of gravity. Hotter air is less dense, so it rises to the top of a flame in a peak.

This also pulls in cooler, more oxygenated air, keeping the fire going. 

But in microgravity, the hot air forms a spherical shape around the source of the fire.

This limits how hot the fire can get and how long it can burn, as there are no convection currents to supply the flame with fresh oxygen for combustion.

The fire will also likely be stifled by its own exhaust gases, limiting its lifespan.

So, that pivotal scene in the film Gravity where Sandra Bullock’s character battles a roaring fire on board the International Space Station? Pure fiction.

She attempts to put the fire out with a CO₂ fire extinguisher, which may actually work, provided it was one designed for a microgravity environment.

Studying fire on the International Space Station

Astronauts have actually carried out experiments for real, studying fire in the weightless environment on the International Space Station.

This includes learning more about the chemical reactions that take place when something burns, and the gravitational forces at work that define the shape of a flame.

You can find out more about this in the NASA video below.