The rightist argument that we shouldn't spend money on something which we can't see an immediate benefit, like the arts for example, starts to look identical to the leftist argument that the money could be used to benefit the poor, or public schooling or other things, pretty quickly. If that was the only means by which the value of a thing should be measured, then I think that there is a pretty good argument to be made that all public art should be defunded and this includes public broadcasting. While we're at it, all public funding of anything to do with sport, the Olympics, all public parks and national parks, needs to be stopped immediately.
Of course I don't believe that all of those things should be defunded and in many cases, I think that more public money should go towards these things. About the subject of space exploration and going to the moon, apart from the multiplier effects where for every $1 invested in the space program it eventually returns $17 in technology improvements, the biggest reason for going into space can be summed up in just one word -
Not quite fifty years later, in the same way that English school kids are still banging on about two world wars and one world cup (doo-dah), American kids can still say that the only twelve people to have been on the moon were 'Murican! If that sounds like some silly super hyper patriotism to you, then you are right in your assessment and you should give yourself a bunch of stars and thirteen stripes. If there's one thing that America does well, it's super hyper patriotism.
Yes, the whole Apollo Program was essentially an empty action which was mostly about waving the flag but that was kind of the point. If you want to tell a national story which is apart from the shameful bits of history like slavery, racism and inequality, then if the country wants to create a shared narrative, it needs to look outwards and there is no greater symbol of looking outwards than actually looking beyond the bounds of this pale blue dot.
The whole point of the public finding of so called useless stuff, if it isn't immediate economic benefit or deferred economic benefit is obviously for some other benefit which policy makers think will be conferred. If something like a public park is being funded then the benefits include the health and well being of the citizenry, if it is the arts which are being funded then the benefits include the cultural advancement of the country; in the case of sports funding the benefits are direct entertainment as well as a sense of civic togetherness in some instances. Looking at space funding generally, I think that as a piece of civic investment that it pays dividends which well exceed that which was spent; for the Apollo Program in particular, it is still telling a story almost five decades later and still inspiring people. As a piece of propaganda at a very singular time in history it was quite effective at demonstrating a nation's power and might but as a piece of history, it still speaks to people as to what could be possible if only people worked together.
This speaks to a greater problem about reducing the world to just a series of numbers. When you reduce everything to a price, you find out the value of nothing. The number that is often quoted about how well the country is doing is Gross Domestic Product (GDP) but the problem with using only a single number like that is that it tells you nothing about the life of the nation. GDP tells you nothing about the happiness of the citizenry, the level of inequality, how well people are living, what brings people together or what inspires them, and it certainly doesn't tell you about how stable the country is. Immediately you are free to ask what the point of space exploration is but if you ask practically anyone who was alive in July of 1969, they can tell you exactly where they were when Neil Armstrong kicked the moon. For a brief moment, the world looked up together and saw something inspiring and which made them happy and reducing this to the single number of cost, obscures what the value was.
I guess what I'm asking here is what is the value of the civic life of a nation? Detractors who will point to what is perceived as a colossal waste of money, and indeed twenty billion dollars is a very big number, fall to recognise that that was spread over ten years and taken as a percentage of the US Government budget it worked out to be less than two percent per year; if you look at NASA's budget in 2017, it is still less than two percent of total government spending. I bet that if you were to look at some individuals' annual budget, there's a distinct possibility that someone spends more on coffee as a percentage of their annual spending than the US Government does on space. The net effect of an individual's spending on coffee is their well being in the morning and I don't think that it's much of a stretch to suggest that the space program is possibly an equivalent, except that it just happens to generate subsidiary benefits in the process. Spending all that money on coffee in the morning doesn't make the nation say 'MURICA! and nor is it ever likely to.