Babbage's technology was feasible in principle. The differential engine was successfully built as a museum project, though it was complicated by Babbage not leaving behind detailed plans[0]. It can be argued that gear-based computational engines face inherent technical challenges that electrical designs don't. But simpler, far more successful versions of mechanical calculators have been developed as well[1].
There is a far greater resolve to invest in Quantum Computing technology compared to Babbage's technology in the 19th century. It remains to be seen whether ultimately something useful emerges. But we might discover other things along the way, just as the Manhattan project and the Race to the Moon were the pathway to develop several other useful technologies.
> The differential engine was successfully built as a museum project
…with modern CNCs. It was simply not feasible at the time to build the parts required with enough precision, that’s what I meant by “no impact”, no one built on it because by the time we had the tools to build it, the tools where better than the thing itself.
As for the “along the way” argument, for me that’s a non-starter. We could use the same argument to justify investing in scams. “Cold fusion might not be possible, but think of what could we discover on our way there!”
The link I referenced stated that care was taken to ensure the tolerances required were achievable by 19th century technology. The biggest difficulty was in refining the designs into actionable manufacturing plans. Of course they used CNC; why mess up at the last step.
For both moon landing and quantum computing the challenges were recognized to be enormous, but achievable by unthrottling the money faucet. Cold fusion is different because there is not even a theoretical venue ahead. It would be a true search in the dark at this point.
Yes, I recognize that these astronomical projects were seldom launched with purely scientific goals in mind, and I wish humanity would do it for the science in the future.
There is a far greater resolve to invest in Quantum Computing technology compared to Babbage's technology in the 19th century. It remains to be seen whether ultimately something useful emerges. But we might discover other things along the way, just as the Manhattan project and the Race to the Moon were the pathway to develop several other useful technologies.
[0]: https://www.computerhistory.org/babbage/modernsequel/
[1]: https://en.m.wikipedia.org/wiki/Curta