Re: To quote Top Gear... How Hard Can It Be™
You quoted Top Gear, it's a car program.
It's not that things are known/unknown, it's that growth and innovation come from commercial prospects. (Most of us live in a Capitalist society)
The technology in rockets hasn't evolved much since the 60's, we've had maybe 4-5 generations of rockets, for 2 reasons:
Cars are a good analogy, because of the problems with rockets, while more complicated than a car. Cars also had problems to begin with, but Cars generally have a generation every 4 years or so, given they've been around for a 100 year, so around 25 generations.
It's evolution, Cars also have a commercial market with an established demand from customers.
Rockets are in lower demand, relatively and due to their high development and operating costs, the frequency and volume is low, reducing investment stimulation.
The commercial opportunities (currently) are also low, due to these high operational costs.
Cars require much lower investment and operating costs, have a higher commercial return and experience generational upgrades on a higher frequency.
Until that generational leap is achieved in propulsion that allows orbit to be achieved for a much lower cost, it will remain a venture for Governments and the Super rich.
I do hope Reaction engines get their pre-cooler to work, it will be a real game changer in the industry.