The Gigantic Space Cannon
Gerald Bull was a physics genius, and without a doubt the greatest weapons designer that Canada has ever produced, which may very well be impressive for all we know of Canadian weapon designers. Bull's line of work was a field called "super-artillery", which is a military term meaning "huge fucking cannons."
One of his crowning achievements was the G5 Howitzer, which could launch a shell 30 miles. Being the sort of person who gets a Physics PhD and goes into the field of "giant gun design," Bull decided 30 miles was fucking embarrassing.
So he went to work with the American government in the High Altitude Research Project, where he pointed other gigantic guns directly up into the sky and fired objects up to 60 miles high. You know the Stratosphere? Bull shot through that shit, sending projectiles into something called the Mesosphere. But that wasn't enough. His dream was to build a cannon so big it could shoot a satellite into orbit. After all, isn't that how they'd do it in a cartoon?
Above: Gerald Bull
After trying the Americans, who shockingly turned down the opportunity to build a ludicrously huge cannon, he went about building and selling arms to crazed dictators from all over the world, including South Africa, China, and Iraq. He eventually convinced budding young Iraqi leader Saddam Hussein that the only way to make all the cool countries respect him was to have a space program built around his big-ass cannon.
Saddam put him to work building his dream. They made a small scale prototype to work out the kinks, and there were probably several considering the final gun (nicknamed Big Babylon) was to be 500 feet long and 3 feet wide. It would have to be built into a freaking hill, just to stand up.
So Why Don't We Have One?
Before they could import the materials for Big Babylon, Hussein decided to invade Kuwait, and brought down the wrath of the international community.
It turns out part of Iraq's strategy in the Gulf War consisted of shooting at the Israelis. Israel wound up sending the Mossad (they're sort of like the CIA only they're actually good at what they do) after Iraq's weapon suppliers. Shortly thereafter, Bull was found dead in his apartment with 5 bullets in his head.
And thus, another of the world's dreamers died, taking his dreams with him. Just as John Lennon wanted world peace, Gerald Bull simply wanted a gun big enough to fire shit into space.
The Atom Bomb-Powered Spacecraft
Even when space travel was still on the drawing board, mankind was full of visions of missions to Mars and space hotels. We saw with sinking disappointment that people could only go up in tiny little capsules with stale air, cramped quarters, and crappy food, and even then only after decades of training.
But there was a pair of crazy bastards named Ted Taylor and Freeman Dyson who headed a project to build a huge, sci-fi atomic spacecraft. And no, we don't mean that it worked on atomic power (though NASA tried to do that, too, with a project called NERVA). We're talking about something way, way more awesome than that.