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  3. (1)If all had gone according to plan, the James Webb Space Telescope(JWST)wo

(1)If all had gone according to plan, the James Webb Space Telescope(JWST)wo

游客2024-11-14  38
问题     (1)If all had gone according to plan, the James Webb Space Telescope(JWST)would be celebrating its 10th anniversary of capturing stunning portraits of distant galaxies, NASA would be hard at work on its dark energy detector, Virgin Galactic would be running two daily tourist flights to the edge of space for just $ 50,000 a head, and a Russian company would be doing brisk business with its orbiting luxury space hotel. Of course, that’s not how it worked out in reality. Last month, Virgin Galactic made its tenth annual prediction that "next year" it will finally shuttle tourists to space, joining the JWST on the horizon of 2018, and the inaugural mission of NASA’s new Space Launch System slipped to 2019. As for that space hotel, don’t ask.
    (2)Planning for the future is part of what it means to be human, but cognitive biases, development challenges, and financing conventions conspire to make accurate predictions next to impossible. With forecasting occupying a central role in our greatest ambitions from space to construction, economists and engineers alike are harnessing new tools that let the past inform the future, aiming to make prediction more science and less art.
    (3)At the root of the problem is the tendency to take the optimism generated by a grand idea and overlay that on the execution without applying the critical rigor required to foresee the inevitable hurdles that are likely to complicate the process. Known to psychology for decades, the Planning Fallacy describes the tendency to overstate chances of finishing tasks on time, despite memories of past projects having rarely gone as planned. " Kind of counterintuitively, it’s because people base their predictions too much on imagining and planning how the task is going to unfold," explains Dr. Buehler, a professor of social psychology at Wilfrid Laurier University.
    (4)Most folks think through a mental simulation of completing various stages of the task and budget time accordingly. Even when reminded of past failed predictions, people tend to assume those were isolated mishaps, forgetting that there are countless ways for a plan to go wrong but only one way for it to go right. When individuals gather into groups, the situation gets even worse. "If the team is all invested in the project, getting together and planning it out as a group in fact exacerbated the bias," says Buehler. Apparently, no one wants to be a Negative Nancy.
    (5)Such optimism often leads to underestimating the chance of unknown unknowns derailing your project, so planning experts suggest a technique called reference class forecasting, where project planners learn from past risk by predicting overruns based on how similarly complex projects fared before.
    (6)The aerospace industry in particular could use some new tricks. Virgin Galactic doesn’t release public estimates, but according to the U. S. Government Accountability Office’s annual review, NASA’s large project costs have overrun budget by between 10 percent and 50 percent in each of the last nine years, a figure dominated by the ballooning costs of the JWST. The 2015 NASA Cost Estimating Handbook outlines three prediction models: drawing holistic analogies to previous projects, calculating relationships between key characteristics and cost, and building up itemized costs.
    (7)But when you’re attempting the unprecedented, be it space tourism or a Pluto probe, how do you build data-based models?
    (8)Not one to back down from a challenge, NASA in 2013 and 2014 developed the Technology Cost and Schedule Estimating(TCASE)software, which uses reference class forecasting tenets to predict the most uncertain of undertakings: creating new technology. Mining a database of over 3,000 past technology development projects, the program’s creators isolated a handful of characteristics that showed predictive power, such as technology area and a classification scheme known as Technology Readiness Levels, or TRLs, which go from 1(physically conceivable on paper)to 9(mission proven). Such tools formalize techniques that have proved effective, according to former ESA program manager Alan Thirkettle, who oversaw the development of the European ISS components. He describes a budgeting process that has long incorporated reference class forecasting type thinking, but one that may have varied between managers and facilities.
    (9)TCASE is just one of a suite of models, and how successful they’ll prove remains to be seen. The 2016 GAO report congratulated NASA for slowing budget creep in recent years, but attributed it only in part to new project management tools, with the rest of the credit going to rising baseline estimates that hide percentage-wise growth.
    (10)What’s more, TCASE applies only to technologies in the early development stage. This period may be the most uncertain, but it counterintuitively accounts for less than a fifth of total development resources. A meta-study of a dozen NASA missions found that costs tend to explode toward the end, with nearly half of the total dedicated to moving a technology from TEL 7(space-ready prototype)to launch. Mr. Thirkettle says this trend is standard, likening spacecraft development to building an electric car. Even if inventing long-range battery tech is tough, actually building the whole car costs much more. "The system is far, far more expensive than the technology development part," he says.
    (11)These unavoidable features of the development cycle combine with cognitive bias to make even the best-laid plans go awry. But to make matters worse, even if reference class forecasting could roughly estimate the chance of unknown unknowns cropping up, it’s hard to get advance funding for what-if scenarios. " Historically you can say on the average project you might get somewhere between 5 and 10 percent of surprise that you just couldn’t foresee," says Thirkettle, but "you can’t say give me an extra so many million because I may get a launch failure. " Available money tends to get spent, so any rainy-day funds have to be carefully earmarked.
    (12)This paradox means that even though planners may expect delays, initially authorized plans often don’t reflect that wisdom, making them closer to a best case scenario than a firm promise. And space just exaggerates that challenge. "You tend to be fairly close to the state of the art so you can get surprises no matter how much discipline you try to put into things," Thirkettle says. [br] The key difference that "reference class forecasting" has brought into planning lies in that______.
选项 A、it is largely based on imagination
B、it relies on accurate calculations
C、it learns from the past experience
D、it establishes prediction models
答案 C
解析 细节题。根据题干定位至第五段。该段指出，这种技术是通过分析过去类似复杂程度的项目进展情况来预测超限程度，而从前一段的内容可知，以往人们的计划往往是依赖于想象，忽视了过去失败的经验，可见这种技术与以往做法的最大不同就是汲取过去的经验，故[C]为答案。依赖于想象，是以往人们制订计划的特点，也正是这种新技术要克服的，因此排除[A]；文章中没有提到精确计算的问题，因此排除[B]；作者并没有提到以往的技术是否建立过预测模式，因此不能判断建立预测模式是否是新技术区别于过去的关键性差异，故排除[D]。
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