If Skunkworks were to design a replacement for the SR-71, with the same mission requirements it had in the 1960's, what would change? I'm not talking about the spy technology or drones; I'm asking from an aircraft engineering standpoint. A manned-aircraft capable of 80,000 feet-plus with a top speed of greater than Mach 3. Are there engines made today that would work better than the J58's they used in the 1960's? Would it still have titanium skin? How about the shape of the airplane - would there be a better, more efficient shape? Would it still leak like a sieve when parked?

The aircraft seemed so ahead of its time; I just wonder if it is a design upon which could be improved...?

I'm not sure this is that big of a problem to solve, but I'm betting new materials would allow for fuel tanks that didn't leak when on the ground.

You can look at a lot of the work going into hypersonics today for some of these answers. A lot of the metals would be subbed out for various high-performance composites (MMCs and CMCs).

On the engine side I'm assuming that you're not going to hit Mach 3 with anything made after the 1980s, so probably not any better tech available there. Only evidence there is that it's a similar problem that Boom's supersonic airplane has that nobody is building engines to thrust a massive airframe >Mach 2 through the air anymore.

I've often thought that there was a secret follow-on program to the X-15. But WTFDIK?

They’d design the craft to fly really high, so high that regular aircraft can’t even reach them. They’d be designed so that they stay above the weather and any turbulent air currents. They’d have the ability to transmit their information and photos directly to ground stations without having to use film or other media. They would be made to stay aloft for years and run on solar energy. They’d be satellites.

The problem with satellites is their orbit is predictable, and a satellite can only carry so much Delta-V to change it's orbit.

If the SR-71 could be improved, Kelly would have done it. Do we have any of his talent and vision today?

I believe the engineering talent is out there today but without Kelly's willingness to pursue unproven concepts something like the Blackbird couldn't be done. So much of corporate focus is on increasing the share value that taking risks like that are uncommon today.

I don’t think we really cracked the hyper sonic thing, other than the X 15 and the space shuttle. If we had the same mission requirements for a manned plane today, I think it would look a lot like the original Blackbird. Similar proportions, cleaner lines, maybe lighter weight and a little smaller.

That mission disappeared when we signed the treaty with Russia that allows free over flight, so the U-2 and satellites do a plenty capable job of gathering the intelligence we need.

The challenge begins with propulsion. The SR's engine was already designed for a Navy program when the SR was conceived. The engine drove the design and performance of the airplane. Better, they didn't have to go design a new engine and a new airplane simultaneously, which is a tough row to hoe.

So... What engine are we starting with?

That's a 5 year old article and all I can see is the leading paragraph because of the paywall. What's the body of the article say?