Thread

NASA asked several former SR-71A staffers to help secret restart

327 points · 403 comments · ilamont

scrumper · 1790779923 · focus · HN ↗
The general tone here seems to be against the effort, but separate the circus from the ringmaster and there is a lot to like here.
Having a manned, very high altitude, very fast research plane is undoubtedly useful for all sorts of development purposes.
But more than that, we are as a civilization doing a bad job of preserving cutting edge expertise from the past. We keep letting entire areas of engineering and technology die out without really trying to preserve them even though we know at some point they will come in useful. The skills, processes, even institutional confidence developed in just trying to get an SR-71 flying again will teach us a lot about resurrecting other such dead ends. Aerospace in particular is full of them. That will, for sure, get us out of trouble or speed up something we need at some unknown point in the future. I'd think of it more as developing a general capability than the world's most expensive vintage aircraft hobby.
1. runjake · 1790780542 · focus · HN ↗
  Look, I'm certified as the world's biggest SR-71 fan. As a kid, I saw it fly a number of times, got to see it up close, and had a family member who worked as an engineer on the program. I believe it may have even been this Blackbird, 844. It impacted me so much that I later went on to work on my own black and other military aircraft.
  I'm assuming that, if this rumor is true, somebody in the Trump campaign forced somebody at NASA to do this out of some misguided nostalgia. My hope is that if they're going to resurrect the Blackbird, they'll at least retrofit modern engines into the thing.
  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.
  There's better technology that's far cheaper to maintain and operate. And you could potentially get hypersonic, or at least near-hypersonic, performance.
  1. ryukoposting · 1790782243 · focus · HN ↗
    > My hope is that if they're going to resurrect the Blackbird, they'll at least retrofit modern engines into the thing.
    Question for people who actually make the engines: is this idea feasible? Like, at all?
    I always imagined a plane's engines to be very tightly coupled to its electrics. In my mind, even if the wire harnesses somehow lined up right, the signals inside would be talking totally different languages.
    runjake · 1790783707 · focus · HN ↗
    There's standards for signaling like this. One being MIL-STD-1553. Another being ARINC. And you're now seeing a lot more Ethernet and such.
    Normally, the engine itself uses proprietary signaling for its systems internally, but will present a standardized interface to the avionics.
    <a href="https://en.wikipedia.org/wiki/MIL-STD-1553" rel="nofollow">https://en.wikipedia.org/wiki/MIL-STD-1553
    ryukoposting · 1790785829 · focus · HN ↗
    Some quick wikipedia surfing suggests the SR-71 was built at least 7 years before MIL-STD-1553 was introduced. Wikipedia says 1966 for the Blackbird, and 1973 for MIL-STD-1553.
    Granted, plenty of de facto standards exist long before they're codified into a formal document. So maybe the Blackbird actually does use it, or something close enough for a dinky little converter box to do the job.
    According to that Wikipedia page, out of the first 6 jets to officially use MIL-STD-1553, only one of them was a Lockheed product. That single Lockheed product was the P-3C, which was a retrofitted version of a plane Lockheed started making more than a decade earlier. To me, that suggests that, even if MIL-STD-1553 existed as a de facto standard at the time of the SR-71's contstruction, Lockheed probably wasn't using it yet.
    All speculation, obviously. But the timeline leaves me with doubts.
    runjake · 1790791876 · focus · HN ↗
    It is worth noting that MIL-STD-1553 can and has been retrofitted into multiple aircraft that were manufactured decades before it existed.
    ryukoposting · 1790867410 · focus · HN ↗
    The aforementioned P-3C being an example - a Lockheed-built example, no less.
    There's still part of me that can't quite believe that the SR-71 wouldn't be an exception. You don't just make a turbojet out of 1965 technology, without something being so wackadoodle batshit crazy as to make comparions to all other planes pointless. Another commenter mentioned something about a "hydraulic computer?"
    I'd love to be wrong. It'd be hilarious if some madmen from the 1960s built a Mach 3 jet out of mostly-normal parts, and then that mostly-normal jet turned into American patriotic folklore. And yeah, I'd feel a bit of patriotic euphoria to see a Blackbird in the sky! I'm not above that.
    Onavo · 1790783767 · focus · HN ↗
    The two things that make or break an airplane are the engines and airframe. Everything else can be swapped out. As long as the airframe can support the engine, structurally and aerodynamically speaking, there are no issues. Wiring and avionics can all be easily replaced. The control systems for the plane can be reworked too.
    GP is correct, this is a plane designed almost pre CFD, a clean sheet design would go much further than this. They are missing out on half a century of material science advances.
    Tangurena2 · 1790789873 · focus · HN ↗
    The control "computer" for the engines of the SR-71 is hydraulic, not electronic. Some of the parts of this aircraft reach temperatures beyond what current semiconductors can cope with.
    If you watch a YouTube on the J-58 engines that go into this plane, you will find out that it behaves like a jet at "low" speed (like Mach 1 or below) while at Mach 3 it behaves like a ramjet. There's no other aircraft engine that does this.
    runjake · 1790794541 · focus · HN ↗
    You might be interested in the GE RTA :-)
    <a href="https://ntrs.nasa.gov/citations/20050196667" rel="nofollow">https://ntrs.nasa.gov/citations/20050196667
    The spirit of what you say about the J-58 is true -- it does work like that but it is still "just" an afterburning turbojet.
    I personally think the path forward is a turbine -> ramjet -> scramjet architecture for an aircraft that goes zero to hypersonic.

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