From New Scientist Technology, your ACME Inc. update

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Human cannonballs

The old circus trick of firing a person from a cannon is being considered by the US Defence Advanced Research Projects Agency (DARPA) as a way to get special forces, police officers and fire fighters onto the roofs of tall buildings in a hurry.

A ramp with side rails would be placed on the ground near the target building at an angle of about 80°. A (very brave) person would then sit in a chair, like a pilot’s ejection seat, attached to the ramp.

Compressed air from a cylinder underneath would be rapidly released to shoot the chair up the ramp's guide rails. At the top the chair would come to an instant halt, leaving the person to fly up and over the edge of the roof, to hopefully land safely on top of the building.

Of course, the trick is to get the trajectory just right. But the DARPA patent suggests a computer could automatically devise the correct angle and speed of ascent. It also claims that a 4-metre-tall launcher could put a man on the top of a 5 storey building in less than 2 seconds. I think I'll take the stairs.

Read the full patent here.

Source: http://www.newscientisttech.com/article/dn9170-invention-human-cannonballs.html