Japanese astronaut's 9cm growth spurt could mean he can't fly home

Norishige Kanai
Norishige Kanai Photo credit: Getty

Japanese astronaut Norishige Kanai has gone public with one of his fears in space - that he may now be too tall to come back to earth.

The Washington Post reports Mr Kanai has grown nine centimetres during his stay on the International Space Station, which brings him quite close to the limit for trip back to Earth.

Astronauts are shuttled back to Earth in a Russian Soyuz TMA spacecraft, which has a seat limit of 191 centimetres.

"Today I share some serious news," Mr Kanai wrote. "Since coming to space, I have grown nine centimetres. 

"This is the most I've grown in three weeks since junior high school. I am a little worried I won't fit in my seat on the return trip on Soyuz."

Mr Kanai later realised he was mistaken and had actually only grown two centimetres. 

It's not uncommon for astronauts to grow in space, as the lack of pressure on the spine allows fluid to expand.

Nine centimetres in three weeks is unusual, but it's not outside the realms of possibility.

"Nine centimetres is a lot, but it is possible, knowing that every human body is different," Libby Jackson of the UK Space Agency told BBC News.

"There's a range of growth for different people and everybody responds differently."

It's unlikely that the growth will prevent Mr Kanai from heading back to Earth, though, and he's not the first astronaut to still have this problem.

"According to my quick calculations here, I seem to have grown about an inch or so," formerly 191 centimetres-tall astronaut Richard Hieb told controllers in 1994.

"So I'm now too tall to fly in space... and that's without slipper-socks."

Mr Hieb was able to return safely, a feat Mr Kanai hopes to achieve him in June, when he departs the ISS.

Newshub.