The original A-12 took 4 years (or less) to design and build from scratch with slide rules and manual machine tools.
Surely we can match that with our 70 years of advanced knowledge and equipment?
Maybe our risk tolerance is low now, and we don't have Kelly Johnson.
Design is a very different matter when you have a workshop full of skilled workers and machinery right on your doorstep, who can critique your work and explain what they can and cannot produce. A lot of engineers discovered this the hard way when companies started outsourcing to the other side of the world and lost control of production process.
Designing parts that look nice but are impossible to machine or assemble is simple.
Designing the plane may only have taken four years, but training the staff, organising the workshops and mastering the production tools took much longer.
Just look at the struggles faced by all the organisations that stopped producing anything for a long time and then wanted to restart production. Whether it’s ships, aeroplanes or nuclear power stations, each time it takes something close to ten years to restart.
When they manage to do so.
Lockheed had no experience with titanium prior to OXCART. 95% of the first 6,000 sheets of titanium had to be scrapped.
It was the first production design to incorporate low-observable shaping.
It was 50% faster than anything Lockheed had previously tried to build, and four times faster than the U-2.
And they literally did all that between April 1958 and April 1962.
So, yes, it was designed from scratch as nothing useful from prior projects read across to it.
I'd compare it to a really old codebase. Sure, our modern tech is much better. But if you need to make an old, top-secret COBOL program work as-is, you're in a pickle. Sure, we could rewrite it in Rust and make it way better, but management sees it as more cost-effective to just "turn the old one back on, it worked great!". And unlike software, it's pretty hard to comprehensively test a plane in a non-destructive way. Bolt falls off turbine while in flight, etc etc. Losing even a single SR-71A airframe would be a massive headache, methinks.
Yes, you are not a mechanical engineer.
If you think my reply was off-base, give me a bit more than this mate.
or the engineers from that time who had an intuitive knowledge of how this should all be designed. You can't teach a computer intuition.