The Basilica di Santa Maria del Fiore is a good example. One of the most fascinating things about this cathedral was that they had no idea how they were going to build the dome when they started building it (the construction techniques weren't advanced enough at the time). They had faith that someone in a later generation would figure it out. That person turned out to be Filippo Brunelleschi, one of the greatest engineers of that time.
Construction of cathedrals often takes a long time - look at the Sagrada Família in Barcelona, started in 1883 and still being worked on (although it has been consecrated):
I second Arethuza, if you count construction projects there are some impressive long term projects. Some, such as Chichen Itza (400yrs) or Stonehenge (1,600yrs), have direct scientific significance as well.
... and that is exactly how funding would have to work -- tied to an ongoing organization's operations. Academia has their endowments and perma-fundraising. Religions have donations and tithing. This effort would need an analogous long term funding source.
My first thought is that if 1% of all renewable energy revenue was sent to this effort, it would provide potentially massive funding as renewable energy grows. I don't know how to convince the greedy energy folk to give up 1%, but it sure sounds nice.
This effort would need an analogous long term funding source.
No need to re-invent the wheel: turn the problem over to the religious.
The Roman Catholics has a long organizational history, millions of adherents, a large and functional bureaucracy, familiarity with generations-long projects.
Also, they speak Latin which will jazz things up.
I suppose Rome needs a reason _why_ to pursue this.
- Long-term people will be in space. They'll need ministry.
- If you're looking for the ultimate in isolation from wordly concerns for your religious, you can't beat the Oort Cloud.
Roman Catholics, outside of Gene Roddenberry's religion-free vision of the future, often seem to end up in space. In the Speaker for the Dead series, they were attempting to convert a whole other species. In Altered Carbon, they were still on spaceships trying to catch up to the distant stars since they weren't allowed to use subspace transmission (needlecasting) to transfer their consciousness (because of issues with their souls). In either scenario, you could make the case that they'd have a vested interest in being the first or best at creating interstellar space travel.
I think only a few religious/academic institutions have managed to have ambitious projects in the 100-year range.