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Comment by spingsprong | Hacker News Reader

"It is, in fact, impossible to reach the speeds of which the MIG-25 is capable using titanium: yet the Soviet designers had managed to build this, the fastest combat aircraft in the world, from ordinary steel. "

Right...

MiG-25, Mach-2.8. All steel.

SR-71, Mach-3.5. Uses titanium for 85% of its structure.

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I think this was an area for which the writer simply wasn't as well informed. Titanium and steel are both capable of fulfilling the requirements, but titanium is very difficult to work with. (Lockheed had particular trouble with it as well.) It's more ideal to use because its so much lighter, and increasing weight is the bane of any aircraft's existence. The Soviets would have preferred this, but they couldn't overcome the machining challenges, especially not in the scale required to build the numbers required. So they went with the safer, if less ideal alternative. And since the Soviet system did not exactly encourage discussion of shortcomings, and the "simple is better" tradition fits well, its not far to see how the "steel is better" explanation became the accepted one.

All that being said, I point out that the plane did what they set out to do, and regardless of whatever compromises had to be made, it was an aerospace achievement.

Speaking of titanium, the Soviets also had a class of attack submarines with titanium hulls:

http://en.wikipedia.org/wiki/Alfa-class_submarine

Combat aircraft. SR-71 is a spy plane.

While it is true that the SR-71 & A-12 were spy planes, and that the GP makes a slightly asinine statement, the pedant (and aviation geek) in me feels obliged to point to the YF-12[1].

The YF-12 was a twin-seater derivative of the A-12 that was developed as a fighter aircraft, complete with a look-down/shoot-down radar and missile bays.

The F-12 never made it to production, but a small number high-speed of weapons tests were conducted with the 3 YF-12 airframes that were built.

With that said, the MiG-25 should certainly not be belittled as a marvel of aviation. It was a blisteringly fast interceptor and reconnaissance aircraft, with an impressive radar system for its time. It filled a special role in the Russian Air Force until last year[2].

[1] http://en.wikipedia.org/wiki/Lockheed_YF-12 [2] https://medium.com/war-is-boring/21d12739b5db

Just out of interest, was the MiG-25 'all steel' and 'all valves'? As in no electronics as we know them, just valves? I had heard that it was EMP-proof due to the lack of any transistors on board...

80% nickel steel alloy, 11% aluminium, and 9% titanium. Using valves instead of transistors meant for easier maintenance in addition to resistance to EMP. [0]

[0] http://en.wikipedia.org/wiki/Mikoyan-Gurevich_MiG-25

The SR-71 and the MiG-25 were originally envisioned for exactly the same role: next-gen high speed, high altitude interceptors. We made a decision that missiles would fill the niche better, and the SR-71 became a recon platform, but it's roots are still in combat.

Perhaps a typo/misquote. The point being made is that the high speeds were achieved using steel (rather than more exotic materials). As others have pointed out the SR71 wasn't a combat aircraft.

Pretty sure the SR-71 is not a combat aircraft.

And that matters because?

That matters because you're comparing apples to oranges, the part you quoted specifically mentioned combat aircraft. Giving the SR-71 as a counter example makes no sense.

It's like mentioning the space shuttle as a counterexample.

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