Arguably the depression would have been worse had he not enacted those programmes, and it's entirely possible that, had they been bigger, they would have worked
That may be true, but the value of these programs( $50,000,000,000 Estimated off of Harvard's website) to today's dollar roughly comes out to 1,000,000,000,000; as one U.S. dollar in 1900 was worth somewhere around 20 dollars today.
Our space program may somewhere come out to be somewhere around this amount, possibly more,
still who's to say it will work?
A generation ship can contain an entire ecosystem. You would have fields on board to feed people. All waste would be recycled (including dead people). The only things you'd need would be a small stockpile of stuff like steel for repairs and things.
Even if that didn't work and we had to go with the constant re-supply (which seems largely impossible seeing as the resupply ships would need resupplying once the mother ship got far enough from Earth) there would still be the problem of using up resources like that later when there were none to spare. If there is going to be a global food shortage as looks likely then I'd prefer that we didn't have to keep sending a load of food off to a space ship too.
As for fuel, solar sales as are used on probes already will do just fine.
Ok, fair enough,
we'd still be risking a lot doing this, and when I say a lot, I mean A LOT.
How many human lives could be lost if we had a shortage or didn't have enough materials to repair a huge problem?
And where would we get this ecosystem?
You yourself stated that we don't have enough farm land, what are we going to do when building this ship during the beginning? Take farmland off of the Earth and stick it up in a ship?
Solar Sails are fairly new technology for space travel. If we were going to use them we should probably develop the technology farther than it is.
Solar Sails still haven't been used successfully in space as a propulsion system, so this isn't a liable option yet.
What would we do when we hit an area where there is no sun?
Superluminar travel is an idea of science fiction only. It's been shown that you need the total energy of many, many stars to actually do it (I can't remember how it's done exactly. It's something like opening a small wormhole and throwing the other end of it away as far as possible so that instead of moving mass (which Einstein showed to be impossible) you move empty space).
Ok, fair, but we could still create recyclable batteries and make energy plants on every planet we hit(assuming they are close enough to the sun).
We'd need more research still, and we don't have the technology now to efficiently do this,
I stand my case.