What if Flying to Mars was Like Driving to Chicago?

By now, it’s pretty well known what went wrong in the Mars Climate Orbiter Mission: Lockheed gave NASA’s Jet Propulsion Laboratory a computer file with units in the old English notation, and the JPL assumed they were metric. In this case, it was maneuvering data, defining how much thrust was needed out of the maneuvering jets at certain times. The English unit for thrust is called a pound-per-second, the metric unit is called a Newton. So how big is the difference?