Project Manhigh was a short term program designed to see how a man could withstand the near-space environment by living in a capsule at 100,000 feet for a full day. The exposure to radiation would be akin to what an astronaut would experience in space, and the capsule that would keep him alive would go a long way towards developing something to keep a man alive in space. At least, that was the idea. And it turned out to be a very good one!
For more on Stapp, check out this article on Vintage Space.
And there's a lot more on Project Manhigh in my book, Breaking the Chains of Gravity, which is available now in the UK and January 12 in the US, Canada, Australia, and India (I think!). You can (pre)order your copy on Amazon.
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