*Originally posted by Rocketmaniac *

**...but how did the engineers predict 90 days and the rovers last for more than 4 times that amount? **

As an engineer, I've noticed that pi is a suitable multiplier to apply wherever guesses and estimates are concerned. Some evidence:

A old professor of mine used to take the tests he was about to give his students, then multiply the amount of time it took him by pi in order to estimate the time it would take the students. Worked every time.

I was doing a study once about 10 years ago where cost estimates were required. As the study manager went through the numbers (plucked from thin air in most cases), I noticed the trend that non-recurring engineering costs were always about pi times the acquisition costs. When I pointed this out to him, he stopped making up numbers and started just multiplying things by pi. Strangely enough, a large DoD acquisition program wound up budgeting procurement based on those numbers! This trend has held up repeatedly over several other studies I've been involved in.

Whenever waiting for funding to arrive from one of my customers, I always multiply their time estimate by pi. If that customer is the government, I multiply by pi squared. Works like a charm. A coincidence? I think not.

I could go on and on, but you get the idea. The answer, it seems, is always pi!