but there are alternatives for gold - I don't think that there is anything that relies only on gold
Modern electronics, gadgets, vehicles, and Space equipment NEED to use gold. Sure there are alternatives like silver and copper, but they corrode easily and are not dependable. When you need security, dependability and quality, gold is necessary. With space equipment, where any problems or replacement would require millions/billions of dollars, there is no alternative. I find it concerning that you think astronauts not having quite as good radiation protection is a minor thing.
I don't really know why you suddenly brought up dollar value tokens as legal tender, as well as why you would even bring them through the airport, when we were just talking about them as physical investment. Do you print your stock certificates and bring them with you all the time? haha.