People shocked after finding out what Apollo 11 astronauts left behind to act as life insurance incase they didn’t make it back from space

Decades on, it's hard to imagine just how radical the first manned mission to the Moon was back in 1969 - it was the definition of a truly unprecedented event.

When these space missions are planned out, one of the things that comes into play behind the scenes is insurance - policies to cover unexpected events or bad outcomes.

This has always been a complicated area, but when a Moon landing had never before successfully come off, it's no surprise that insurers were pretty reluctant to set up a policy - or if they did, it was a ridiculous amount of money.

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The astronauts on the mission were reportedly unable to find life insurance policies they could afford that would cover them if they died on the trip, which meant that their families could be left in a bad situation if things did go wrong.

So they came up with a pretty amazing solution. Before the mission, Neil Armstrong, Buzz Aldrin and Michael Collins apparently got to work filling up a number of hours by signing their autographs on envelopes.

They knew that even if their mission didn't go well, their names would become famous.

Robert Pearlman, a space historian and collector with collectspace.com, told NPR: "These astronauts had been signing autographs since the day they were announced as astronauts, and they knew even though eBay didn't exist back then, that there was a market for such things."

Before they departed on their mission, these signed envelopes were given to a friend, whose job was quite simple - on important days of the Moon mission, like the take-off, Moon landing and return to Earth, they went to a post office to have the envelopes stamped, so that they got even more valuable by having that specific date on them.

The envelopes were then distributed to the astronauts' families so that they could sell them down the line if they needed to - acting as a sort of home-made insurance policy of their own design.

Luckily, their families never needed to sell these autographs - but now, they've become collectors' items.

In fact, Pearlman told NPR one of the envelopes can cost as much as $30,000.

When the story got posted to Reddit this week it raised some eyebrows, with the top comment summing things up: "Crazy. You think the government would have underwritten something since it was such an outlandish endeavor."

Another commenter agreed, saying: "That's both incredibly sad and incredibly smart."