Over at Oobject, you can see an amazing collection of rocket sled images from the past century. Some of these rocket sleds can reach up to 6000 mph, and are used for everything from testing aircraft to researching how much G-force a human can withstand.
In fact it was one of those human tests that gave rise to Murphy's Law back in the late 1940s. An engineer named Edward Murphy was working on G-force tests at Edwards Air Force base. He'd devised a force measurement sensor that could be plugged into the rocket sled, called the Gee Whiz (below), which would give researchers an extremely accurate measurement of the amount of G-force their long-suffering test subject Lt. Col John Paul had endured.
Unfortunately, a technician hooked the sensors up incorrectly and got a zero result, meaning that Paul had suffered through potential broken bones and a concussion for nothing. Later, when test participants discussed the dud test with media, they referred to how they hadn't accounted for "Murphy's Law," in which anything that could go wrong would go wrong.
See more amazing rocket sleds via Oobject.