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Comment by jandrese | Hacker News Reader

> But there are much more modern, cost-effective ways to build very-high-altitude, very-fast aircraft. I'm doubtful that going manned is the right approach. It takes a lot of weight and space to carry a person and the required life support systems. That capacity could be better utilized for more fuel and sensors.

Is there? High speed turbofans are still exotic technologies. Or are we doing the research with drone rockets now? I have to imagine that building a modern SR-71 replacement would be an expensive development project with little commercial prospects. The sort of thing that is extremely hard to complete in the modern political environment.

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Turbofans are not exotic technologies. They are well understood, and their limitations are well understood.

Presumably, an SR-71 successor would use a mix of turbofans and ramjet/scramjet to meet their performance (speed/altitude) goals, depending on whether it would be self-sufficient or use takeoff assist from another aircraft.

Despite them being complex, high-bypass turbofan engines ARE exotic technology. There are vanishingly few countries/companies that have the expertise necessary to produce the single crystal fan blades used in the engines of these aircraft.

As far as the SR-71, its engines were turbojets that transitioned to ramjets above Mach 2ish. They required a special grade of jet fuel and a dedicated fleet of refueling aircraft.

I rather doubt an SR-71 successor would use a turbofan. The mission profile really doesn't require it. I would expect it to be a turbojet that transitions (as you said) to a ramjet and eventually a scramjet.

I would love to see the SR-71 fly again, if only from a nostalgia standpoint, but I really doubt this effort will be successful. I doubt even more that much of value can be accomplished by getting one to be flyable again that couldn't be achieved in a much more cost-effective manner via unmanned aircraft.

The whole of the SR-71 was built around what kind of cameras was needed to perform the mission. Modern electronics and cameras are much smaller. I would presume an unmanned plane launched from a bomber could perform the mission today.

> Despite them being complex, high-bypass turbofan engines ARE exotic technology.

Sure, I'll concede here. I think of "exotic" as "few people/nations understand it well enough" but including the manufacture and tooling seems like a no brainer inclusion.

Edit to my comment, I meant "Despite them being common," not "Despite them being complex."

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