In broad terms, I've been interested in space since the 3rd grade and specifically interested in space colonization since I was in the 6th grade. Throughout high school, my interest in space spurred an interest in STEM in general and a desire to become an aerospace engineer in particular. When I entered college, I studied engineering but quickly realized just how far away the dream is from reality. Instead of giving up, I doubled down and innovated new paths to help us reach space colonization -- with the Moon being a central feature. I've since then given talks at multiple space conferences and joined the Moon Society.
What I've come to realize is that science fiction primes the pump of our imagination while space technology gives us an arena within which we can incrementally work towards bigger goals inspired from sci-fi. The desire for human exploration and later permanent settlement has existed at least since Apollo if not earlier. The problem has always been economic. Can someone build an economically self-sufficient program that can build on itself to achieve exponential growth, lower the overall cost of operating in space, and send humans to places where they can add economic value?
Given that we have not moved forward on space colonization since Apollo, we're probably not going to go forward with a human spaceflight-driven path at first. The upfront cost is high enough that it could affect national security. It will probably be robotic at first and then humans will be added only after logistic economic growth reaches a plateau, and only when the value-add is greater than the cost of sending humans. Once humans start having children in space, the value-add becomes exponential. At a certain point, they would no longer be feeding the initial investors but themselves, and become a community in their own right. At that point, we'll start having interplanetary trade.
Argument 1: It provides the necessary PR and funding for more critical scientific mission like cassini and new horizon.
Counter 1: Lower launch cost in the future will negate high funding cost, thus negating the need for PR stunts involving humans.
Sci-fi was originally an anti-colonial form of literature in the 1800s. It was designed to generate empathy within western cultures for foreign nations to help imagine what it would feel like if an even more advanced civilization treated us as we had been treating others. It later evolved into one of the primary conduits for thinking about the future, which spawns STEM innovation. Space technology has a HUGE disconnect between the present-day reality and the technological ideal it aspires to. As a result, it has the potential to drive innovation until that reality is achieved.
Argument 2: Lot of spin-off technologies are developed in R&D like velcro
Counter 2: These technologies weren't developed by NASA, and even where they were, they do not outway the cost, and might have developed on their own. (This is a weak defense on my part since it relies on speculation)
And the integrated circuit... which is the foundation of the modern world economy. Of course, Fairchild Semiconductor developed the IC, which later became Intel. However, Fairchild's first-run products were too costly for the commercial market. NASA's mission requirement for lighter-weight computers (not the vacuum tubes that filled an entire floor of a university) created the incentives to develop ICs.
At the Moon Society, we're actively thinking about how to economically develop the Moon using robots and later humans. This means putting industry on the Moon. When you consider that lunar regolith is abrasive and lightly magnetic and that it creates challenges with rotary motion (most motors), we're going to have to overcome those challenges to build industry. We also won't have access to oil because 1) it won't be readily available and 2) it outgasses in a vacuum. We're also going to have problems with radiation affecting electronics. Overcoming these critical problems means going back to the drawing board with ALL industrial technology ever developed since the start of the Industrial Revolution. A lazy person might stop when faced with these problems. But for people who are motivated to overcome them, doing so will spur further innovation.
Argument 3: Human are required for time critical task that require improvisation.
Counter 3: What time sensitive task? (This one I hear a lot, I'm not sure as to what they're getting at. If you know, could you explain it to me?)
The most recent ANA Avatar XPrize will demonstrate what teleoperated robots are capable of. Right now, there aren't universal robots that can use a shovel in one moment and work in a lab in another. Even if such a technology matures and becomes viable, and is put on the Moon, we will be limited by the speed of light. The Moon is 1.282 light secs away or 2.564 round trip (no processing). This is with teleoperations on the Moon. A 3-second delay between issuing a command and seeing a response is probably at the upper limit of what most humans would accept. Anything beyond this, we're going to want humans onsite. Especially if we're talking about asteroids or other planets.
So to answer your question, we need to send humans into deeper space because of the limits of light and because humans can prioritize information more quickly than computers can. AI/ML works best for routine problems, not drawing inferences for new ones.
Argument 4: Humans can improvise at the moment where machine can only use the tools it's equipped with.
Counter 4: Humans are also limited to the tools they have at hand. It also much easier just to send a second probe.
Say there is a business operation on Mars that must deliver a payload to Earth in the next planetary transfer window -- say to make a critical bond payment (or risk default). Now imagine there was a mission failure on a scale like in the movie The Martian (ignoring the dust storm and supposing it was something else) -- and suppose it also affected communications. Would a robot be able to develop a workaround?