This topic comes up pretty regularly, and it always amazes me that there is not an appreciation that nearly everyone in science and engineering has to work through unknowns in development on a schedule, and we've all adapted.
I work on developing a product that integrates a lot of different fields. I work with various engineers, physicists, biologists, chemists, and programmers. All of them have tasks that are impossible to estimate time and cost for with 100% certainty. That's an unreasonable bar to set. Many of them have tasks that may simply be impossible with current levels of technology.
We work out a schedule and budget, because otherwise we can't move forward on development, or understand when the amount of resources required to finish the project will be more than the end value of the end product. We have some basic research grants and the government requires a schedule, budget, and regular reports for blue sky research as well. We produce some lab equipment for pharmaceutical companies. Those guys have scheduling and budgeting challenges that make a lot of engineering projects look easy.
My team trusts that I will only change requirements for good reason, and will adjust resources and schedule to reflect reality as we progress. This adjustment for reality works the other way too. I trust them to understand that there are finite resources and time available to attempt a project, and if something isn't working out, it's getting cut.