The debt is serviceable still, and a national debt that is reasonable can be a good thing. The key is to manage it will. The bad thing is when it gets to be too large.
Ours is around I think 65% or so of GDP right now. Japan's is like 200%, and the European nations on average have larger debts too.
As for space, I'd say I think the private sector will be the ones to take us there. One key is to get a much more affordable rocket for launching stuff into space (Elon Musk is attempting this, don't know if he'll succeed though), and one that is also safer. Some more affordable and safer rocket designs have been proposed within NASA, but were killed due to politics and bureaucracy in NASA and Washington.
For example, I believe the only reason they still use the solid rocket boosters on the space shuttle is because of politics. A much safer liquid methane-fueled rocket was proposed, but was killed.
Solid rockets are dangerous because once they start burning, you can't turn them off.
Also ROBOTS. As robotics technology becomes more advanced and cheaper, we can explore space via robotics a lot more I think, especially in the private sector, and then this can make way for industrializing space and also sending humans up.
For example, it used to be bipedal robots were only science fiction. Then Honda and Sony created bipedal robots. Now there are bidepal robot kits in the thousands and hundreds of dollars even. Amazing to think where the technology will get to over another twenty years, especially with tinkerers and hobbyists.
Maybe today's robot tinkerers will be the entrepreneurs of a coming "robot revolution," in which every home will have a personal robot. Perhaps you could then send humanoid robots that can walk and utilize tools to Mars, to do things traditionally only humans could do. Much safer that way.
Or a human could go to Mars themselves, but with a group of robot aids. Google right now has an award up for whoever can launch a robot to the Moon and then drive it around and broadcast the video on Youtube.
Sending humans to Mars presents ENORMOUS problems though, in terms of psychology (how to put multiple people into a small space together for months and not have them murder each other), the fact that the Earth from Mars is just a blue dot and not a huge globe in the sky like from the Moon, the fact that spending months in zero gravity causes huge atrophy of bone and muscle tissue, so how to prevent this...?
And so forth. So while I hope we can do this someday, until then, robots I think can present a cheaper and safer alternative.