3 ms·

Is Mach 3.5 the highest reported speed? Is it "official" in some way?

brightball 4y ago
I believe it's the upper limit to the SR-71's engine style based on air intake. If you watched Top Gun: Maverick since it came out they (spoiler) had him flying a prototype plane called the Darkstar to hit Mach 10 in order to maintain a military contract. During the flight, he switches engines to SCRAM Jet once he reaches Mach 3.5 because in order for those types of engines to have enough air intake to function, you already have to be traveling at that speed. This was such an innovation that China redirected a satellite to find the plane because they thought it was real. If you've never read Skunk Works by Ben Rich, I highly recommend it. Lots of SR-71 stories along with U-2, F-117 too.
- andrewflnr 4y ago
  I doubt they were absolutely convinced it was real, but still pretty hilarious. https://www.businessinsider.com/bruckheimer-china-moved-satellite-to-see-top-gun-hypersonic-aircraft-2022-5 https://www.businessinsider.com/bruckheimer-china-moved-sate...
  - greggsy 4y ago
    “The Navy told us that a Chinese satellite turned and headed on a different route to photograph that plane.” I can only assume that China publish their targeting on some Twitter account? What ludicrous statement.
    - brightball 4y ago
      I don't think the Navy was watching Chinese twitter...
      - greggsy 4y ago
        Are you implying that they disclosed (to a movie director) that the USA have a foothold within China’s IMINT apparatus? It’s trivial to observe flyover changes, but it’s ludicrous to suggest that this action alone meant they were looking for a specific aircraft.
    - andrewflnr 4y ago
      Amateurs can track satellites with telescopes. Inferring intent from a course change is pretty reasonable if it makes a direct overpass, with not much else of interest on the same track. That's not the crazy part of the story.
    - scottyah 4y ago
      Is this a reference of the USA doing just that? https://www.npr.org/2022/11/18/1137474748/trump-tweeted-an-image-from-a-spy-satellite-declassified-document-shows https://www.npr.org/2022/11/18/1137474748/trump-tweeted-an-i...
    - deleted 4y ago
      [deleted]
agloe_dreams 4y ago
Fastest official is Mach 3.43. I would note that that isn't likely the full story. The US Gov has famously been deceptive about the plane, both overselling or underselling its abilities. (Notably, I do not believe that the US Government ever 'officially' admitted to overflying the USSR.) It is very possible that for a short period of time, they sustained over mach 3.5 or 3.6, what affect that would have/had on the airframe and engines is unknown. An interesting story is that once, during the cold war, a Mig-25 was supposedly tracked over Israel at over Mach 3.2 in what is best described as "GTFO" mode. It basically was an attempt to do what the US was doing with the SR-71s. At that speed, the engines are assumed to have been scraped after each flight. One could make assumptions that the ram-jet elements of an SR-71's J-58s could allow for a few minutes, in the right airframe, with a lucky bin of build quality and weather, far beyond that. I would also note that this story buries the lede. The title states mach 3.5 but the pilot implies numbers beyond. I'm not sure how factual it is or if it is dramatized, but the pilot absolutely is who they say they are and wrote a book about it.
- ranger207 4y ago
  > At that speed, the engines are assumed to have been scraped after each flight. > One could make assumptions that the ram-jet elements of an SR-71's J-58s could allow for a few minutes...far beyond that I would expect the SR-71 to stay at speed longer and for the engines to be capable of higher power (assuming the airframe and intake can handle it). US engines were generally higher quality, while Soviet engines were expected to be replaced very quickly relatively. However, this was a conscious decision on the part of the USSR: instead of making expensive engines with good maintainability in the field, they chose to make cheap engines that were easy to replace. As a result, while a MiG-25 may have only been able to maintain Mach 3 for a few minutes and ruin the engine in the process, they built 1,186 of them, with probably >5,000 Mach 3 capable engines. Not particularly relevant, but always interesting to discuss how different people think
  - phkahler 4y ago
    The SR71 engines are the only ones ever designed to run continuously in after burner. Also in ramjet mode, going faster increased the efficiency as the bow shock swept back and into the engine inlets, providing pre-compressed air.

I believe it's the upper limit to the SR-71's engine style based on air intake. If you watched Top Gun: Maverick since it came out they (spoiler) had him flying a prototype plane called the Darkstar to hit Mach 10 in order to maintain a military contract. During the flight, he switches engines to SCRAM Jet once he reaches Mach 3.5 because in order for those types of engines to have enough air intake to function, you already have to be traveling at that speed. This was such an innovation that China redirected a satellite to find the plane because they thought it was real. If you've never read Skunk Works by Ben Rich, I highly recommend it. Lots of SR-71 stories along with U-2, F-117 too.

andrewflnr 4y ago
I doubt they were absolutely convinced it was real, but still pretty hilarious. https://www.businessinsider.com/bruckheimer-china-moved-satellite-to-see-top-gun-hypersonic-aircraft-2022-5 https://www.businessinsider.com/bruckheimer-china-moved-sate...
- greggsy 4y ago
  “The Navy told us that a Chinese satellite turned and headed on a different route to photograph that plane.” I can only assume that China publish their targeting on some Twitter account? What ludicrous statement.
  - brightball 4y ago
    I don't think the Navy was watching Chinese twitter...
    - greggsy 4y ago
      Are you implying that they disclosed (to a movie director) that the USA have a foothold within China’s IMINT apparatus? It’s trivial to observe flyover changes, but it’s ludicrous to suggest that this action alone meant they were looking for a specific aircraft.
  - andrewflnr 4y ago
    Amateurs can track satellites with telescopes. Inferring intent from a course change is pretty reasonable if it makes a direct overpass, with not much else of interest on the same track. That's not the crazy part of the story.
  - scottyah 4y ago
    Is this a reference of the USA doing just that? https://www.npr.org/2022/11/18/1137474748/trump-tweeted-an-image-from-a-spy-satellite-declassified-document-shows https://www.npr.org/2022/11/18/1137474748/trump-tweeted-an-i...
  - deleted 4y ago
    [deleted]

agloe_dreams 4y ago

Fastest official is Mach 3.43. I would note that that isn't likely the full story. The US Gov has famously been deceptive about the plane, both overselling or underselling its abilities. (Notably, I do not believe that the US Government ever 'officially' admitted to overflying the USSR.) It is very possible that for a short period of time, they sustained over mach 3.5 or 3.6, what affect that would have/had on the airframe and engines is unknown. An interesting story is that once, during the cold war, a Mig-25 was supposedly tracked over Israel at over Mach 3.2 in what is best described as "GTFO" mode. It basically was an attempt to do what the US was doing with the SR-71s. At that speed, the engines are assumed to have been scraped after each flight. One could make assumptions that the ram-jet elements of an SR-71's J-58s could allow for a few minutes, in the right airframe, with a lucky bin of build quality and weather, far beyond that. I would also note that this story buries the lede. The title states mach 3.5 but the pilot implies numbers beyond. I'm not sure how factual it is or if it is dramatized, but the pilot absolutely is who they say they are and wrote a book about it.

ranger207 4y ago
> At that speed, the engines are assumed to have been scraped after each flight. > One could make assumptions that the ram-jet elements of an SR-71's J-58s could allow for a few minutes...far beyond that I would expect the SR-71 to stay at speed longer and for the engines to be capable of higher power (assuming the airframe and intake can handle it). US engines were generally higher quality, while Soviet engines were expected to be replaced very quickly relatively. However, this was a conscious decision on the part of the USSR: instead of making expensive engines with good maintainability in the field, they chose to make cheap engines that were easy to replace. As a result, while a MiG-25 may have only been able to maintain Mach 3 for a few minutes and ruin the engine in the process, they built 1,186 of them, with probably >5,000 Mach 3 capable engines. Not particularly relevant, but always interesting to discuss how different people think
- phkahler 4y ago
  The SR71 engines are the only ones ever designed to run continuously in after burner. Also in ramjet mode, going faster increased the efficiency as the bow shock swept back and into the engine inlets, providing pre-compressed air.