This should cover it for you. But it sounds like you may have a short.
The Flux capacitor is the device that traditionally fails in a spacecraft or time machine. The purpose is still somewhat unknown; however it seems to follow Murphy's law in that, at the most awkward moment, flux failure renders escape impossible. It seems that they only actually work when there is no imminent risk of harm or embarrassment. This forces the intrepid space or time traveller to face his fears, embarrassments , or undergo a character arc in some other fashion.
Flux capacitors are also responsible for every space related accident, from the Apollo XIII to the Challenger and Columbia shuttle disasters. However, scientists have yet to create spaceships without flux capacitors, because without the flux capacitor, something else would inevitably fail. The issue in each "accident" is obviously that the victims were not morally, physically and academically strong enough to muddle through the ethical issue that arose around the time of the flux problem.
The flux capacitor requires 1.21 gigawatts to be used and is offen in conjunction with plutonium or a lightning strike(OR a Mr. Fusion, but if you can afford one of those why would you leave your house). Many have pondered the theoretical implications of two flux capacitors being used together. Some believe this would either end the world, create another Humphrey Bogart or both simultaneously.
At least with flux capacitors you know that there is the problem. The down side is that knowing what the problem is does not solve the moral dilemma faced.
Although the military application of flux capacitors has long been known, their high rate of failure is considered problematic. This was notably demonstrated in 1943 during the US Navy's Philadelphia Experiment. Following a series of test failures in which the frigate USS Eldridge failed to go anywhere, the flux capacitor was removed from the degaussing equipment, culminating in the spectacular teleportation of the ship to the bottom of the ocean in the area now known as the Bermuda Triangle. The ship's equipment continues to function to this day, creating a constant hazard to navigation and frustrating all efforts at recovery. This is the largest Epic Fail of all time (next to taking a swig out of the "butt" can).