NPR reports:

If you are wondering why anybody would deliberately detonate an H-bomb in space, the answer comes from a conversation we had with science historian James Fleming of Colby College:

"Well, I think a good entry point to the story is May 1, 1958, when James Van Allen, the space scientist, stands in front of the National Academy in Washington, D.C., and announces that they've just discovered something new about the planet," he told us.

Van Allen described how the Earth is surrounded by belts of high-energy particles -- mainly protons and electrons -- that are held in place by the magnetic fields.

Today these radiation belts are called Van Allen belts. Now comes the surprise: While looking through the Van Allen papers at the University of Iowa to prepare a Van Allen biography, Fleming discovered "that [the] very same day after the press conference, [Van Allen] agreed with the military to get involved with a project to set off atomic bombs in the magnetosphere to see if they could disrupt it."

The plan was to send rockets hundreds of miles up, higher than the Earth's atmosphere, and then detonate nuclear weapons to see: a) If a bomb's radiation would make it harder to see what was up there (like incoming Russian missiles!); b) If an explosion would do any damage to objects nearby; c) If the Van Allen belts would move a blast down the bands to an earthly target (Moscow! for example); and -- most peculiar -- d) if a man-made explosion might "alter" the natural shape of the belts.

This sounds like madness to me. Nuclear explosions and uncertainty don't mix well!