Astronaut Karen Nyberg shows us how she washes her hair on board the International Space Station. Credit: insideISS/YouTube

AN ASTRONAUT on board the International Space Station has created a video to answer one of the most pressing scientific questions - how does she wash her long hair in space?

American astronaut Karen Nyberg tweeted her video saying "I have had a LOT of questions about how I wash my hair in space! Let me show you…"

With her long hair floating above her head, Ms Nyberg first squirts some water onto her scalp - but bubbles float free as she explains "sometimes the water gets away from you".

The next step is no-rinse shampoo, which she rubs in and works out to the ends, combing straight up as her hair hovers above her head. She then sticks the comb, shampoo and bag of water to the wall, to prevent them floating free, and towels off.

“It actually feels kind of squeaky clean right now”, she says. “We use towels for quite a while here, since we have limited supplies. We use them wisely.”

Not an inch of water is wasted, Ms Nyberg explains.

"Now, as my hair dries, as water evaporates from my hair, it will become humidity in the hair and then our air conditioning system will collect that into condensate and…our water processing system will turn it into drinking water."

Ms Nyberg, a mechanical engineer-turned-astronaut is a member of the Expedition 36 to the International Space Station.