Among the few apocalypses worse than nuclear annihilation, asteroid impact has got to be near the top of the list—at least if Hollywood's depictions are any indication. Luckily, the American public has at least one agency defending it against errant space rocks: the exact same agency that's supposed to be protecting us from thermonuclear war in the first place.
Our bodies are surprisingly resilient in many situations, but rapid acceleration is not one of them. While the human body can withstand any constant speed—be it 20 miles per hour or 20 billion miles per hour—we can only change that rate of travel relatively slowly. Speed up or slow down too quickly and it's lights out for you, permanently.