Shrinking the world would be a good use of it if we could get it to work for commercial air travel (and if we solve the sonic boom problem, but that's another issue a different part of government is working on)
It's very hard for me to imagine a world in which scramjet technology is both useful for commercial travel, and impossible to develop without massive government funding. It seems to me like technology needs to reach a point that it can be developed entirely commercially before it can be made safely and consistently enough enough for commercial passengers.
Take rockets for instance. Technology had to catch up to make them commercially viable to develop before they were commercially viable to operate.
pretty much all of air travel had direct government subsidy in the form of postal contracts in its early days and later price controls. automakers also had a huge subsidy in the form of the massive capital expenditure on highways that were free to use.
developing technologies at taxpayer expense for strategic purposes is nothing new. if private airlines were left to their own devices we probably won't ever move away from the basic shape of subsonic, fossil-fueled jet travel. as it is, the airplane manufacturer duopoly is half kept afloat by defense spending, and it remains to be seen whether or not the full financial cost of 737MAX will result in requiring taxpayer bailout.
But afaik all the airplanes used for the earliest demonstrations of airmail were privately funded/constructed. The minimum viable airplane for airmail was within grasp of skilled fabricators working out of their garages; the big government contracts came later. This is world's apart from scramjet tech.
