Travel to other planets is such a practical scientific impossibility that nasa is completely irrelevant.
Seriously? You REALLY think so?
I ask because, well, WE'VE ALREADY DONE IT.
We've sent robots to multiple other planets, and actual human beings to our nearest planetary neighbor (Luna *IS* a planet...). So much for your "practical scientific impossibility".
Saying that traveling to the moon is a first step to interplanetary travel is about like saying that traveling to the top of mount Everest is an important first step to the moon. If you want to get to the moon, you need to build rockets; climbing mountains is a distraction; you can't climb to the moon no matter how good of a climber you are. If you want to get to another planet, well, I think you are going to need hyperspace or wormholes or other physics that don't really exist yet, in which case your breakthrough is going to come in a chalk room or physics laboratory, and prancing around on regolith is a similar distraction.
As already shown, your thoughts on the matter would be... incorrect. There are DOZENS of other planetary bodies in THIS system which we can reach using any of a variety of rocket technologies. But we'll assume that you wanted to refer to other systems' planets, in which case rockets would certainly make for an awfully slow trip. Do you really think that we can't learn from the ENORMOUS variety of planetary surfaces, atmospheres, chemistries, etc. available to us here in the Sol system? That learning here would be of zero, or even NEGATIVE, value once we can get to a different system? That spreading out into other bodies in the system won't reduce or remove potential threats to our species' survival prospects?
People think technology is magic, so if we can go from the pony express to cell phones in a couple hundred years, it will only be a matter of time until we have one of those fancy space ships they saw on TV. But technology will never invent a perpetual motion machine or a single-reservoir heat engine and it's NOT a matter of time or a matter of wanting it bad enough. And any exoplanets, supposing there are any, are so far away as to be irrelevant. They are far. Like really far. Like so far that when we find one, we won't even know if it's there because the light will be centuries old by the time it hits our telescopes. Using the possibility of interstellar travel to justify NASA funding is basically a joke. Oh, it sounds romantic though.
People with mindsets like that thought the same thing about travelling across the Atlantic, or manned flight, or supersonic flight, or spaceflight, or landing a man on the moon...
Humanity does lots of stuff despite the actions and outcries of naysayers. Probably a good thing, that - plenty of things are only impossible until someone (or many someones) figures out how to actually DO them. I may never see it personally. Probably won't, in all reality. So what? Doesn't mean it's not worth working for, and believing in.
You don't need to, I suppose. Just don't stand in our way, is all I ask.
FYI - they've located over a hundred exoplanets already, many (IIRC) within 100 lightyears - right next door, in relative terms, considering the size of the galaxy. Yeah, I'm not walking there, or even taking a shuttle trip. Who knows what we'll come up with in the next hundred years, to get us out into nearby - or distant - galactic space?
Million years, billion years, blah blah blah.
It took human civilization a measly 3,000 years to go from stone age to space age. Where do you think we'll be in another few thousand years?
We could learn intergalactic travel, and then forget all about it and learn it all over again, a thousand times over in the amount of time the earth has left. We could all abandon this rock, and there'd still be plenty of time for an entirely new species to evolve here and learn intergalactic travel on their own.
It surprises me that people say we need to do it all this right now or else we're DOOMED. I don't get that at all.
By some accounts, we're already overdue (given the rough averages) for either a climatic or space-related catastrophe. That, and averages can be off in either direction, as has been noted.
It might not happen for another million years, sure. It could happen in a hundred years, too. Heck, "it" (whatever "it" is) could happen tomorrow - in which case, we're all toast, because we aren't further along and able to either stop the threat or avoid it. Some circumstances, we can't overcome. Others, we can. We should, IMO.