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Comment by justin66 | Hacker News Reader

> The Air Force and NASA destroyed a $600 million supply of spare parts for the Blackbird fleet in 2007. The move came long after it seemed unlikely, if not impossible, that an SR-71A would return to operational service.

There's also the issue of converting a tanker back so it can carry the SR-71's unique fuel again. And for that matter, making a supply of JP-7 again. No other planes today use JP-7.

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That seems reminiscent of the Fogbank material in the US nuclear weapons. The process of making it was lost, and when it was finally recreated modern processes where to good and it still didn't work. In the end they had to compensate for the improved processes and re-add impurities.

https://www.youtube.com/watch?v=Y6tqlf31YTc

it looks like it would be much easier to get a powerful regular fighter jet engine (even old Mig-25 engines were fine for 2.8M), stick it to pilotless frame and just launch. Work a bit on intake shape, modern materials, CFD, and probably you can push it well into 3+.

Building a machine that can travel at speeds exceeding Mach 3 for a brief period of time is probably well within aeronautical engineering's current capabilities, with today's engines, yes. The innovation with the SR-71 was that it could fly at those speeds for an hour and a half, thanks in part to that JP-7 fuel with its high flash point.

Either way it's unclear why NASA, with its decreasing budget, might feel like they need to be taking this on as a research project.

This is essentially the thought process behind the Hermeus Quarterhorse which is already a thing that exists and is in active development:

https://www.google.com/search?client=firefox-b-d&q=hermeus+q...

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