Is it bollocks?

Film Buff investigates the facts behind outlandish movie plots.

Can a fire extinguisher really propel you through space, à la Gravity?

THIS MONTH SANDRA BULLOCK’S FIRE EXTINGUISHER PROPULSION IN GRAVITY.

qIn Gravity, Dr. Ryan Stone (Sandra Bullock) travels through space using a fire extinguisher as a thruster. Would that actually work if you happened to be stranded in space?

adr. gemma lavender, phd in asTRophysics, ediToR oF all aBouT space Yes and no. While it’s true that you can use a fire extinguisher as a kind of handheld jetpack as Bullock does in a bid to reach China’s Tiangong-1, being able to control which direction she was moving in through space would have been much trickier than how it’s portrayed.

As a general rule, whenever mass – in this case, the carbon dioxide – is ejected in one direction, momentum causes the remaining mass (the extinguisher) to move in the opposite direction. Bullock was allowing highly pressurised gas to escape, creating something similar to when a rocket launches from the ground here on Earth.

Bullock’s character uses it to change her altitude at high speed

– a manoeuvre that requires a lot of energy that’s not possible to get out of a canister of compressed gas. Bullock successfully propelled herself in the direction she wanted to go, but the extinguisher would have needed to have been at her centre of mass for her to propel herself the way she did – tricky to obtain in her situation. In reality, she would have been thrown off balance and spun around much more.