标签: cost estimate

NASA recently released an estimate of how much the next phase of manned space exploration would cost, which includes a new heavy booster and capsule worth billions of dollars, see here . So I wondered: "why does manned space exploration cost so much?" and came up with these answers: - "Costs so much" when compared to what else? - Because it is manned, not unmanned, and a manned mission costs 10× to 100× more than an unmanned one, and take much longer to plan and engineer - And my final answer: I don't know why. I'm not going to second-guess the rough cost and time estimates, since I have absolutely no expertise or special insight into the project. But I am pretty sure that the estimate given has an uncertainty band of -50%/+100% (at the very least), and we know that the odds are much more likely that the error will be on the plus side rather than the minus side. What I really wonder about is this: is it even possible to provide an answer with order-of-magnitude accuracy to the question of what it will cost, in money and time? With all the unknowns in an ambitious project like this, and all the new technologies that will have to be developed, built, tested, and assessed, you might as well spin a roulette wheel to get the answer rather than try to work it out in advance. Plus, there's that engineering maxim to keep in mind: we want it fast, cheap, and right—but you can only pick two of those attributes (at best). Have you ever had projects where a tight estimate of time and cost was expected, yet you knew that any SWAG (scientific wild-ass guess) you offered was really just a WAG (SWAG without the "scientific")? Did that "soft" estimate somehow increasingly get taken and used as a real, solidÿnumber as it worked its way up the management chain, despite all the caveats or misgivings you voiced?