A final option is to not go anywhere at all. Humanity will be planetary homebodies. Our use of space will consist primarily of Earth-orbiting satellites, maybe a lightly crewed Low Earth orbiting station, and the occasional robotic exploration mission. Basically, what we’ve been doing since Apollo 17.
This is certainly the cheapest and easiest option. It’s also the most unsatisfying and dangerous option. Since there’s nothing to explain here, let’s just jump to the costs and results.
- Nothing new in the way of money being spent. We just keep doing what we are doing now. Or even less.
- There would be a significant lost opportunity cost if we gave up human space exploration (and settlement). I couldn’t find a reputable source but I remember reading that the economy grows by $10 for every $1 spent on NASA. Please email me if you find a good source.
- One word. Dinosaurs. The joke is that the dinosaurs went extinct because they didn’t have a planetary protection system. And there’s truth in that. However, you can’t really blame the dinosaurs as they didn’t have a technological civilization (how cool would that be!). The sad part is that we DO HAVE an advanced civilization that COULD develop the tech to protect itself from extinction. We could build the infrastructure to deflect incoming asteroids and we could establish life all across the Solar system so no single planetary disaster could wipe it out.
- What happens to civilizations that stop looking outwards? They turn inwards. I’m not a sociologist and I don’t claim to have any particular theory. But it seems logical that society starts stagnating when it stops expanding into new frontiers. I would argue that our obsession with entertainment (in all it’s forms) is a symptom of this. I would also add our current rabid divisiveness as a symptom of our lack of frontiers.
- Less technological advancement. Since 1976, the U.S.A has benefited from more than 1,300 NASA technologies . And it’s not just solar panels and Tang. Space exploration has resulted in significant medical advances (dialysis, artificial hearts, advanced imaging, etc.) . I use cordless power tools all the time. Those were developed by NASA . Those are just few of the thousands of things we use or rely on that came from space exploration. We stop getting new toys if we stop exploring.
- Less kids getting into the harder sciences. Let’s face it. Entertainers and CEO’s get paid a lot more than scientists and engineers. If you’re going to be paid less you should at least be doing something really cool, exciting, and worthwhile. Like expanding life into space. Without the draw of space settlement, we could lose generations of talented and passionate people to more mundane pursuits.
That list is nowhere near comprehensive. Heck, I’m sure someone has already written a book on the subject. And if not, someone should! My point is that we are already suffering significant costs by not expanding into space and will incur more in the future.
 NASA Spinoffs Fact Sheet (https://www.nasa.gov/centers/kennedy/news/facts/nasaspinoff.html)