There's a tragic story behind a seemingly carefree image showing three men in spacesuits floating in a swimming pool.
When we picture the training which NASA astronauts undertake, the first thing which comes to mind is most likely extended periods of time inside zero gravity machines, memorising every aspect of their spacecraft and gruelling physical training.
But it turns out there's a lot whole lot more hoops astronauts must jump through before waving goodbye to the Earth's atmosphere - including spending an afternoon hanging out by a swimming pool in your spacesuit.
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Taken in June 1966, the photo taken at Ellington Air Force Base in Houston, Texas may look like every space fanatic's dream birthday party, but it was actually a critical part of pre-mission training.
The three men suited up and sat on yellow floats in the image are Gus Grissom, Roger Chaffee and Ed White and they were in the pool that day to practice emergency landing procedures in water.
Astronauts still train in water to this day, but this is now undertaken in training facilities which look a lot less picturesque than Ellington Air Force Base's swimming pool on a summer afternoon.
However, the story of Grissom, Chaffee and White is one which would end in tragedy just six months later.
What happened to the astronauts onboard Apollo 1?
The Apollo 1 mission was scheduled to launch on 21 February 1967, however, the spacecraft would never reach that date.
During a pre-launch test on 27 January, a devastating fire would break out in the cabin and claim the lives of the three men.
On the day in question, the three men would enter Apollo 1's control module in order to simulate a 'plugs-out test', which would see the spacecraft disconnected from electrical systems on the launch pad and make sure it was ready for launch.
Dressed in their pressurised suits, Grissom, White and Chaffee were strapped into their seats and began working through a checklist as the module's three-part hatch was installed. After the hatch was sealed, all air inside the cabin was replaced by pure oxygen.
It is at this point that the unthinkable happened as the cabin suddenly burst into flames, with the heat inside meaning it was impossible for the men to open the hatch from inside.
The final moments of the three men would be captured in a harrowing audio transmission to ground control.
"Fire," Grissom is believed to shout, before Chaffee can be heard saying: "We’ve got a fire in the cockpit."
The three men can then be heard scrambling inside the cabin before one of them cries out in pain as the flames take hold.
Grissom was 40 years old when he died, White was 36 and Chaffee was 31.
The tragedy would lead NASA to make major changes to future spacecraft, including using a 60/40 oxygen/nitrogen mix in the cabin, removal of flammable materials and a redesigned hatch which opened in seconds.
Brenna Cooper